WO2023073315A1 - Coextrusion installation comprising sealing beads which are squeezed against the roller during the closure of the extrusion head - Google Patents

Coextrusion installation comprising sealing beads which are squeezed against the roller during the closure of the extrusion head Download PDF

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Publication number
WO2023073315A1
WO2023073315A1 PCT/FR2022/052015 FR2022052015W WO2023073315A1 WO 2023073315 A1 WO2023073315 A1 WO 2023073315A1 FR 2022052015 W FR2022052015 W FR 2022052015W WO 2023073315 A1 WO2023073315 A1 WO 2023073315A1
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WO
WIPO (PCT)
Prior art keywords
extrusion head
seal
roller
installation
height
Prior art date
Application number
PCT/FR2022/052015
Other languages
French (fr)
Inventor
Christophe Ougier
Miguel Torres-Castellano
Joao ALVES
Original Assignee
Compagnie Generale Des Etablissements Michelin
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Compagnie Generale Des Etablissements Michelin filed Critical Compagnie Generale Des Etablissements Michelin
Publication of WO2023073315A1 publication Critical patent/WO2023073315A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00—Moulds or cores; Details thereof or accessories therefor
    • B29C33/0038—Moulds or cores; Details thereof or accessories therefor with sealing means or the like
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00—Moulds or cores; Details thereof or accessories therefor
    • B29C33/20—Opening, closing or clamping
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/254—Sealing means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/30—Extrusion nozzles or dies
    • B29C48/303—Extrusion nozzles or dies using dies or die parts movable in a closed circuit, e.g. mounted on movable endless support
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/30—Extrusion nozzles or dies
    • B29C48/35—Extrusion nozzles or dies with rollers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
    • B29C48/49—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using two or more extruders to feed one die or nozzle
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D30/00—Producing pneumatic or solid tyres or parts thereof
    • B29D30/06—Pneumatic tyres or parts thereof (e.g. produced by casting, moulding, compression moulding, injection moulding, centrifugal casting)
    • B29D30/08—Building tyres
    • B29D30/10—Building tyres on round cores, i.e. the shape of the core is approximately identical with the shape of the completed tyre
    • B29D30/16—Applying the layers; Guiding or stretching the layers during application
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B29C48/07—Flat, e.g. panels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B29C48/12—Articles with an irregular circumference when viewed in cross-section, e.g. window profiles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/16—Articles comprising two or more components, e.g. co-extruded layers
    • B29C48/18—Articles comprising two or more components, e.g. co-extruded layers the components being layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2021/00—Use of unspecified rubbers as moulding material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2030/00—Pneumatic or solid tyres or parts thereof
    • B29L2030/002—Treads

Definitions

  • the present invention relates to the general field of coextrusion installations intended to produce profiles by assembling, through an extrusion head provided with a die, several elastomeric mixtures which are conveyed together to said extrusion head by a plurality of extruders.
  • the present invention relates more particularly to coextrusion installations intended to produce profiles which enter into the composition of tires for vehicle wheels, for example profiles intended to form treads or sidewalls of tires, in particular pneumatic tires.
  • the elastomeric compounds now used, in particular in the tire industry, to form the underlayer of the profile, that is to say the first layer of elastomeric compound deposited, which is therefore in contact directly with the surface of the roller, and on top of which the layers formed by the other elastomeric compounds are stacked, tend to be more and more fluid, which makes it necessary to reinforce the seal between the extrusion head and the roller to avoid leaks and malformation of said underlayer of the profile.
  • the objects assigned to the invention therefore aim to remedy the aforementioned drawbacks and to propose a new extrusion installation which guarantees, in a simple and reproducible manner, an effective seal between the extrusion head and the roller, without interfering with roller rotation or requiring complex slack adjustment with each draw.
  • the objects assigned to the invention are achieved by means of a coextrusion installation intended to generate a profile by jointly extraditing a plurality of elastomeric mixtures along a common direction of flow, said installation comprising an extrusion head intended to feed the elastomeric compounds, a roller which is driven in rotation on itself around a central axis, and a closing system designed to alternately pass the installation of an opening configuration, in which the head of extrusion is moved away from the roller, in a closed configuration, in which the extrusion head is brought closer to the roller in order to define with said roller an air gap serving to conform the section of the profile, which air gap extends along a first dimension called "height" carried by a radial direction perpendicular to the central axis, according to a second dimension called “width” carried by an axial direction parallel to the central axis, and according to a third dimension called "wet length" which is carried by the common direction of flow and which represents a portion of the circumference of the
  • the seal is intentionally dimensioned so as to be sandwiched and systematically compressed between the extrusion head and the roller.
  • said seal is intentionally dimensioned so as to be sandwiched and systematically compressed between the extrusion head and the roller.
  • a chosen minimum value of radial interference which allow said joint to adjust, by spontaneous deformation, to the existing air gap, and in particular which allow said joint to absorb, by radial crushing more or less pronounced, any machining and assembly tolerances of the extrusion head, the roller, and the closing system, as well as any variations in the radial height of the air gap along the wetted length .
  • the seal according to the invention is able to fill completely, and for sure, each time the installation is closed, the radial height of the air gap, by marrying over the entire wetted length as well the surface of the roller than the surface of the extrusion head located opposite the surface of said roller, without leaving any radial clearance, and therefore without leaving any gap which would be likely to let the one or the other of the elastomeric mixtures.
  • the invention proposes on the contrary a closing system which defines a unique and reproducible position of the extrusion head with respect to the roller, with a slight known and controlled tolerance range, that is to say a system which makes it possible to maintain the same fixed adjustment value from one pull to the next, and therefore for several successive closings, but which leaves it to the seal to automatically compensate, at each closing, any variations of radial positioning included in said tolerance range, by a suitable and spontaneous radial deformation, said seal under the radial compressive stress which is induced by the existence of the chosen radial interference.
  • the invention therefore advantageously allows the closure system to place the extrusion head facing the "blind" roller, in the nominal position marked by the stopper, without it being necessary to carry out beforehand any adjustment of the position of the members of the closure system which define the position of the extrusion head, and more particularly which define the position of the rigid and fixed elements belonging to said extrusion head, with respect to the position of the roller, in the closed configuration.
  • the closure system according to the invention also makes it possible to dissociate the functional preload of closure on the one hand, that is to say the intensity of the effort which forces the approximation of the head towards the roller by pressing, via the abutment, the support of the extrusion head in a predetermined nominal position against the bearings supporting and guiding the roller, of the functional radial preload of sealing on the other hand, it that is to say the intensity of the force with which the seal or seals carried by the head press on the roller and are compressed against said roller, in the closed configuration, and more particularly in operation during a draw .
  • a very high closing preload typically greater than or equal to ten tons (that is to say, by convention, a force equivalent to the weight of a mass of ten tons) and even of the order of several tens of tons, in order to prevent the extrusion head from being moved away from the roller under the effect of the operating pressure exerted by the extruded mixtures circulating in the air gap, which makes it possible to avoid any alteration of the height of the air gap during a draw, and this without the sealing gasket pressing, and therefore rubbing, too strongly on the roller, since the preload functional radial sealing exerted by the seal on the roller is typically of the order of a few hundred kilograms, preferably less than 2 tons, more preferably less than 1 ton, for example between 100 kg and 800 kg, i.e. said functional radial preload tightness is negligible, namely here less by a factor equal to or greater than 10, or even equal to or greater than 50, relative to the functional closing pre
  • the shape of the seal in particular the width of said seal considered along the direction of the central axis, the minimum radial interference value, as well as the material constituting the seal, will be chosen. so that the extent of the contact area which is created between the roller and the seal, as well as the contact pressure which prevails in said contact area, are on the one hand sufficiently high to guarantee satisfactory sealing, in particular when the radial height of the air gap corresponds to the greatest radial height possible in view of the nominal height and the applicable tolerance range, and on the other hand sufficiently moderate to prevent excessive friction n hinders the proper rotation of the sliding roller on the seal, in particular when the radial height of the air gap corresponds to the smallest possible radial height given the nominal height and the applicable tolerance range.
  • Figure 1 illustrates, in a schematic perspective view, a coextrusion installation according to the invention.
  • Figure 2 illustrates, in a perspective detail view, the extrusion head used by the installation of Figure 1, said extrusion head comprising two seals formed by cords which extend in length in the circumferential direction of the roll and which are housed in grooves dug in the extrusion head; for ease of representation, there is also shown in dotted line, in this same figure 2, an enlarged view of a cord before insertion.
  • Figure 3 illustrates, according to a detail view in section in a radial plane containing the axis of the roller, a first variant of a seal, of circular section, which is housed in a groove of the head of extrusion of Figures 1 and 2. In this view, the seal is shown fictitiously in its shape before radial crushing, so as to show the radial height of interference between said seal and the roller.
  • Figure 4 illustrates, according to a detail view in section in a radial plane containing the axis of the roller, a second variant of a seal having a flattened section and which is housed in a groove of the head of extrusion of Figs 1 and 2, and shows the height of interference between the seal and the roller.
  • Figure 5 illustrates, according to a detail view in section in a radial plane containing the axis of the roller, a third variant of a two-lip seal, housed in a groove of the fig extrusion head 1 and 2, and shows the interference height between the seal and the roller.
  • the present invention relates to a coextrusion installation 1 intended to generate a profile 2 by jointly extraditing a plurality of elastomeric mixtures M1, M2, M3 in a common flow direction L2.
  • the coextrusion consists in bringing together and juxtaposing said elastomeric mixtures M1, M2, M3 in one and the same profile 2, by distributing said elastomeric mixtures so that they coexist in the section of the profile, each according to one or more positions and one or more shapes which have been assigned to the elastomeric mixture under consideration.
  • the common direction of flow L2 corresponds to the longitudinal direction of profile 2, in which said profile 2 is produced continuously, in one piece.
  • the installation 1 comprises an extrusion head 3 which is intended to bring the elastomeric mixtures M1, M2, M3.
  • Said extrusion head 3 comprises for this purpose a plurality of distinct channels Cl, C2, C3, in number at least equal to the number of elastomeric compounds used, each channel Cl, C2, C3 being connected to an extruder which delivers the corresponding elastomeric mixture M1, M2, M3.
  • the extrusion head 3 may comprise, as can be seen in Figure 3, a plurality of blades 4, juxtaposed to each other, which delimit the channels C1, C2, C3 and make it possible to conform the different flows elastomeric mixtures M1, M2, M3.
  • the installation 1 also includes a roller 5 which is rotated R5 on itself around a central axis Y5.
  • Said roller 5 has a cylindrical shape with a circular base centered on said central axis Y5.
  • the apparent cylindrical surface, convex, of said roller 5 forms a receiving surface which is intended to receive the elastomeric mixtures and to accompany the profile 2, as it is generated, in its forward movement in the direction of L2 flow.
  • the roller 5 is preferably made of metal, for example steel.
  • the surface of said roller 5 is advantageously polished, to limit fouling of roller 5 by elastomeric compounds.
  • the surface of the roller 5 is treated to reach a hardness equal to or greater than 1000 HV (Vickers hardness), for example by means of a hard chrome or a vapor phase deposition of chromium nitride CrN.
  • the diameter of roller 5 is between 300 mm and 1000 mm.
  • the extrusion head 3 has a concave shape, substantially matching that of the roller 5, here therefore a concave shape which substantially corresponds to a circular base cylinder portion, so that said extrusion head 3 then comes to cover an angular sector of the roller 5 to define an air gap 6.
  • the installation 1 further comprises a closure system 10 which is designed to alternately pass the installation 1 from an open configuration, in which the extrusion head 3 is remote from the roller 5, to a closing configuration, in which the extrusion head 3 is brought closer to the roller 5 in order to define with said roller 5 the air gap 6 serving to conform the section of the profile 2.
  • a closure system 10 which is designed to alternately pass the installation 1 from an open configuration, in which the extrusion head 3 is remote from the roller 5, to a closing configuration, in which the extrusion head 3 is brought closer to the roller 5 in order to define with said roller 5 the air gap 6 serving to conform the section of the profile 2.
  • the closure system 10 may for example comprise an elevator 11, arranged to move the extrusion head 3 vertically relative to a bearing 12 which supports the roller 5 and which guides said roller 5 in rotation.
  • the opening configuration makes it possible in particular to clean or replace the extrusion head 3.
  • the air gap 6 extends along a first dimension called “height” H6 which is carried by a radial direction DR perpendicular to the central axis Y5, along a second dimension called “width” W6 which is carried by an axial direction DA parallel to the central axis Y5, and along a third dimension called “wet length” L6 which is carried by the common direction of flow L2 and which represents a portion of the circumference of the roller 5.
  • axial will designate a direction parallel to the axis considered, here the central axis Y5, by “radial” a direction perpendicular to said axis considered, and by “circumferential” an orthoradial direction, that is to say which, at a point considered located at a distance from the axis, is normal to the radial plane which contains the axis considered and which passes through said point considered.
  • common flow direction L2 coincides with the circumferential direction.
  • common flow direction L2 and circumferential direction are therefore tangent to the surface of roller 5.
  • the wetted length L6 is preferably between 30 mm and 200 mm, said wetted length L6 generally being all the greater as the number of elastomeric compounds of different compositions entering into the constitution of the profile 2 is high.
  • the wetted length L6 covers, in azimuth around the central axis Y5, a fraction of the perimeter of the roller 5, which represents an angular sector whose extent is between 2 degrees and 40 degrees.
  • the closure system 10 comprises a mechanism 13 with abutment 14 which is arranged to position the extrusion head 3 in a reproducible manner with respect to the roller 5 in the closed configuration in order to guarantee that, in said closed configuration, the height H6 of the air gap 6 is equal to a predetermined nominal height H6_set, together with a known radial tolerance IT6.
  • the abutment 14 of the mechanism 13 may correspond to a surface of the bearing 12, for example the underside of the flange of said bearing 12, against which abuts a portion of the elevator 11, such as this is illustrated in Figure 1.
  • the radial tolerance IT6 will be designated in the form of a tolerance interval defined on the one hand by a low tolerance value, denoted IT6_low, and on the other hand by a high tolerance value, denoted ITô high:
  • IT6 [IT6_low; IT6 Jiigh]
  • the tolerance values IT6_low, ITô high are algebraic, that is to say they may be one and/or the other, either positive or negative, provided that the low tolerance value IT6_low is strictly lower ( algebraically, i.e. taking the sign into account) to the high tolerance value ITô high:
  • the height H6 of the air gap, in the reference zone chosen to set the nominal height H6_set is included with certainty between a predetermined minimum possible height, known in advance, and here being equal to
  • H6_min H6_set + IT6_low taking into account the convention adopted above, and a predetermined maximum possible height, also known in advance, and valid here
  • H6_max H6_set + ITô high, i.e. we have, and we know we have:
  • the radial tolerance IT6 can be determined by simulation (chains of dimensions, finite elements, etc.) and/or by empirical tests, and will depend in particular on the dimensions of the constituent parts of the mechanism 13 of the closing system 10, of the module of Young (here in compression) of said organs, and the value of the closing preload F10 which presses the elevator 11 against the stop 14 of the bearing 12 in order to prevent the extrusion head 13 from being moved radially away from the roller 5 under the pressure of the elastomeric mixtures M1, M2, M3 present in the air gap 6.
  • the installation 1 comprises at least one seal 20 intended to delimit the width W6 of the air gap 6 in order to prevent the elastomeric mixtures M1, M2, M3 from leaking axially out of air gap 6.
  • the extrusion head 3 comprises two seals 20 axially spaced from each other and which each define one of the axial limits of the air gap 6, that is to say which each delimit one of the lateral edges of the air gap 6, so that the width W6 of the air gap 6 corresponds to the distance, preferably constant over the wetted length L6 , which axially separates the first seal from the second seal.
  • the seal 20, where applicable each of the two aforementioned seals 20, is fixed to the extrusion head 3 so as to be able, on the one hand, to cover the length wetted L6 in the closing configuration.
  • the seal 20 advantageously retains the elastomeric mixtures, and more generally the profile 2, captive of the air gap 6 over the necessary length considered for the shaping of said profile 2.
  • the seal 20, where appropriate each of the two seals 20 mentioned above, is fixed to the extrusion head 3 so as to project radially with respect to the extrusion head 3, of a value which, when the extrusion head 3 is in the open configuration, and more particularly when the extrusion head 3 is in the open configuration and fitted with a seal of sealing 20 new, before a first closing, is called "gross projection height" H20_pro and is strictly greater, by a non-zero value called “minimum value of radial interference" H interf, to the maximum possible height H6_max of the air gap 6 which is expected in the closed configuration taking into account the nominal height H6_set of the air gap and the known radial tolerance IT6.
  • the extrusion head 3 forces the radial crushing of the seal 20, if applicable of each of the two seals 20, in compression against the roller 5, by a radial compression value which is at least equal to the minimum radial interference value H interf.
  • the effective height of the seal 20 is automatically adapted, in each radial plane considered along the wetted length L6, to the exact value of the effective height H6. of the air gap 6, by a spontaneous deformation of the seal 20 which occurs when the installation is closed, and the extent of which is automatically adjusted on a case-by-case basis.
  • the radial crushing of the seal 20 advantageously compensates for any foreseeable radial play, and thus guarantees sealing by contact, and this while minimizing the extent of the contact area, and therefore the resisting friction, between the seal 20 and the roller 5.
  • the radial crushing of the seal 20 may include a plastic radial crushing component, that is to say an irreversible radial deformation, of the seal 20. If the seal 20 is sufficiently flexible, the radial crushing may be mainly or even totally elastic.
  • the minimum radial interference value H interf is preferably between 0.05 mm, corresponding to a low value, and 1.00 mm, corresponding to a high value. If necessary, the minimum radial interference value H interf may be between 0.05 mm (low value) and 0.50 mm (high value).
  • the minimum radial interference value H interf is chosen between, on the one hand, a low, non-zero, and of course positive value, which is high enough to guarantee that we will effectively observe, even if c it is only this low value that applies, an effective radial crushing of the seal 20 which is sufficient to ensure leaktight contact between the seal 20 and the roller 5, and on the other hand a high value which is sufficiently moderate so that, even if said high value is applied, severe degradation of the seal by abrasion against the roller is avoided, or excessive braking or even blocking of rotation R5 of roller 5.
  • the nominal height H6_set of the air gap 6 which is intended to be filled by the seal 20 is preferably between 0.10 mm and 0.50 mm.
  • the choice of this value may in particular depend on the diameter of the roller 5, as well as on the quality of production of the profile which is required.
  • the relative fineness of the air gap 6 to be filled radially plumb with the seal 20 advantageously makes it possible to limit the effective height of the seal 20, and therefore the seal surface 20, which is exposed, in service, to the pressure of the elastomeric compounds, which consequently makes it possible to reduce the risk of a leak which would occur by accidental detachment of the seal from the surface of the roller or by local axial deformation of said seal 20 under the pressure of the elastomeric mixtures.
  • this relative thinness of the air gap 6 also makes it possible, even in the event of the occurrence of a leak, to limit the flow rate of said leak.
  • the seal 20 is formed by a bead 21 which has at rest, before being placed on the extrusion head 3, a length L21 which is strictly greater, preferably at least 10 times greater, and more preferably at least 50 times greater, or even at least 100 times greater, than the overall axial width W21 of said bead 21 at rest.
  • the seal 20 is therefore preferably an elongated, wired element which, in the closed configuration, has a small, particularly narrow contact surface with the roller 5, and which therefore generates relatively low friction at against rotation R5 of roller 5.
  • Such a seal 20 in the form of cord 21 is also easy and inexpensive to manufacture, for example by extrusion, and to cut to the desired length.
  • the length L21 at rest of the cord 21 is between 30 mm and 200 mm.
  • the length L21 of the cord 21 is preferably equal to the desired wetted length L6, and in any case sufficient to cover the entire wetted length L6 in one piece.
  • the overall axial width W21 of cord 21 at rest will preferably be between 2.00 mm and 10.00 mm.
  • cord 21 has a cylindrical shape.
  • Such a cord 21 of cylindrical shape has the particular advantage of being easily produced by extrusion in great length, then cut to the desired length L21.
  • the base section S21 of said cylindrical shape is preferably chosen from:
  • a base section S21 with a flat 22 the part intended to project out of the extrusion head 3 is provided with a flat 22 parallel to the surface of the roller 5, or
  • a base section S21 comprising at least two parallel lips 23, 24 which come into contact with the roller 5 according to axially separate contact areas.
  • a circular base section S21 will have the advantage of providing, in the closed configuration, a contact area between the seal 20 and the roller 5 which extends in length following the crest line of the bead. 21, carried by the circumferential direction, and which is relatively narrow, which makes it possible to minimize the wear of the seal 20 and the intensity of the friction exerted on the roller 5.
  • a base section S21 with several lips 23, 24, here two lips, will make it possible to reinforce the seal by creating axially a double barrier which opposes axial leakage of the elastomeric compounds, while maintaining a total contact area. relatively restricted between the seal 20 and the roller 5, since said contact area is limited to the quasi-linear contact areas according to which each of the lips 23, 24, which extends in the circumferential direction, presses on the roller 5.
  • a base section S21 provided with a flat 22 will make it possible to create a wider contact area axially than the two previous variants, which makes it possible to reinforce the seal by creating a more stable barrier and more resistant to pressure.
  • axial which is exerted by the elastomeric mixtures M1, M2, M3, while seekingng however an intensity of friction which may be higher than in the two preceding cases.
  • the axial width W22 of the flat 22 may represent between 50% and 100% of the axial width W21 of the bead 21 at rest.
  • the axial width W22 of the flat 22 may be between 2.00 mm and 10.00 mm.
  • a cord 21 made of a flexible material such as a thermoplastic elastomer (or “TPE”).
  • the central generating line of the cylindrical bead 21, that is to say the longitudinal direction of the bead 21, will preferably follow, when the bead 21 is in place in the extrusion head 3, a circumferential direction, contained in a plane normal to the central axis Y5, and therefore parallel to the direction of flow L2, and said generating line will present a curvature, considered in said plane normal to the central axis Y5, which is such that said bead 21 has a curved profile which matches the curvature of the surface of roller 5.
  • the seal 20 has, at a reference height called “gauge height” which is equal to the maximum possible height H6_max of the air gap 6, one or more portions which occupy, cumulatively, an axial extent called “minimum potential seat width” W20_pot which is between 2 mm and 10 mm.
  • This minimum potential seat width W20_pot will be representative of the minimum axial width of the contact area that can be expected, in the closed configuration, between the seal 20 and the roller 5, in section in a radial plane containing the central axis Y5, when the radially projecting end of the seal 20 sinks, under the effect of the radial compression, by a value equal to the minimum radial interference value H interface
  • the passage in the closed configuration has the effect of reducing the protruding height of the joint by a value which is strictly greater than the minimum value of radial interference H interf, which corresponds to a situation of greater crushing in which the effective height H6 of the air gap 6 is strictly less than the maximum possible height H6_max, and can go down to the minimum possible height H6_min, then the axial width of the effective contact area between the seal 20 and the roller 5 will be strictly greater than the minimum potential seat width W20_pot, since the interference zone reaches a wider solid portion of the gasket 20.
  • the axial width of the contact area between the seal 20 and the roller 5 will systematically be at least equal to the value of the minimum potential seating width W20_pot.
  • the minimum potential seat width W20_pot corresponds, as can be seen in FIG. 3, to the length of the bow chord which extends between the two intersections of the circumference of the circular base section S21 with an axial straight line called the "gauge straight line" L gauge located at a distance from the surface of the extrusion head 3 which is equal to the gauge height, it that is to say at the maximum height H6_max of the air gap.
  • the minimum potential seating width W20_pot corresponds to the sum of the lengths of the various segments defined respectively by the intersection of the gauge line L gauge with each of the lips 23, 24.
  • the seal 20, preferably formed by a bead 21 is inserted into a radially blind groove 25 which is hollowed out on the surface of the head of extrusion 3, groove 25 whose axial width W25 is strictly less than the axial width of the seal 20 before insertion, here the overall axial width W21 of the bead 21 at rest, so that said groove 25 provides axial support said seal 20 by pinching once said seal 20 inserted into the groove 25.
  • said groove 25 preferably has, at its downstream end 25_down considered in the common direction of flow L2, a shoulder 26 against which the seal 20 bears, preferably via its downstream end 20_down , and which thus forms a stop which opposes the circumferential sliding of said seal 20 around the central axis Y5 in the upstream-downstream direction along the common flow direction L2.
  • the invention thus makes it possible to save time and ease of implementation both when setting up a new seal 20 by inserting it into the groove 25 and when removing the worn seal 20 by extracting it from the groove 25.
  • the invention advantageously makes it possible to fix the seal 20 on the extrusion head 3 without it being necessary to resort to auxiliary fixing parts, in addition to the seal 20 itself and of the extrusion head 3.
  • the gasket fixing system 20 can thus advantageously be devoid of fixing screws, flanges, wedges, etc.
  • the radial depth H25 of the groove 25 is chosen in such a way that, when the seal 20 is inserted in abutment against the radial bottom 25_bottom of the groove 25, and the installation 1 is located still in the open configuration, before switching to the closed configuration, said seal 20 protrudes relative to the surface of the extrusion head 23 by the desired gross protrusion value H20_pro.
  • the radial depth H25 of the groove 25 will be chosen strictly less than the radial dimension that the seal 20 has at rest, before insertion of said seal 20 in the groove 25, it that is to say here will be chosen less than the overall radial height H21 of the cord 21 considered at rest, before insertion.
  • the length of the groove 25 will cover the desired wetted length L6, and preferably will be equal to said wetted length L6.
  • a bead 21 will preferably be chosen whose length L21 allows said cord 21 to fill in one piece the entire length of said groove 25, and including the entire wet length L6.
  • cord 21 having, at rest, a radial height H21 of between 2.80 and 2.85 mm, and an axial width W21, preferably equal to the radial height H21, of between 2.80 mm and 2.85 mm ,
  • H6_set i.e. a functional clearance between the extrusion head 3 and the roller 5, of the order of 0.20 mm
  • the seal 20 may be formed in one piece from a thermoplastic elastomer (TPE) material, the hardness of which will preferably be equal to or less than 70 Shore A, in particular when a flexible seal 20, or else in a poly-tetra-fluor-ethylene (PTFE) or a polyamide (PA), the hardness of which will preferably be equal to or less than 70 shore D, in particular when a seal is sought sealing 20 harder.
  • TPE thermoplastic elastomer
  • PTFE poly-tetra-fluor-ethylene
  • PA polyamide
  • the invention of course relates as such to a method of manufacturing a profile 2, preferably a profile 2 intended to enter into the composition of a tire for a vehicle wheel.
  • the profile 2 may for example be intended to form a tread of the tire, or even a sidewall element of the tire.
  • the method according to the invention comprises a step (a) of preparation, during which a first set of seals 20 is placed within an extrusion head 3 of an installation 1 extrusion as described in the foregoing, in order to delimit the two lateral edges of the air gap 6, then a step (b) of producing a first draw during which said installation 1 is placed in the closed configuration , and the extrusion head 3 is fed by means of a plurality of extruders each connected to one of the paths of said extrusion head 3 and each conveying an elastomeric mixture M1, M2, M3, so to produce a first profile 2, then the drawing is stopped and the installation 1 is replaced in the open configuration, then a step (c) of replacing the seals 20 during which the first set is removed of used seals 20 and it is replaced by a second set of new seals 20, then a step (d) of carrying out a second draw, during which the installation 1, provided with its second set of new seals 20, in the closed configuration and a second profile 2 is produced.
  • step (c) of replacing the seals within the same extrusion head 3 is implemented systematically with a lower periodicity or equal to three consecutive draws, that is to say once every one, two or three settings in the closing configuration of the installation 1, and more preferably with a periodicity equal to one and only one draw, it that is to say each time the installation 1 is put into the open configuration, equipped with said extrusion head 3, which follows a step (b) of producing a print using said extrusion head 3 and which precedes a new step (d) of producing a print involving this same extrusion head 3.
  • the seals 20 can be replaced frequently, and more preferably after each use, at each new opening/closing cycle of the installation 1.
  • the seals 20, which are particularly easy and inexpensive to replace, will therefore preferably be "disposable", that is to say for single use, which will guarantee a reliable seal with each new draw.
  • the invention will make it possible, despite these frequent or even systematic changes of the seals 20, to keep the closure system 10 unchanged between consecutive draws, without it being necessary to carry out or modify any adjustment of said closure system 10, in particular any adjustment of play or positioning of abutment 14, nor to operate any modification of extrusion head 3, after each change of seals 20.

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Abstract

The invention relates to a coextrusion installation (1) comprising an extrusion head (3) and a roller (5) that delimit between one another a gap (6), a closure system (10) having an abutment (14) mechanism (13) which is arranged so as to reproducibly position the extrusion head (3) with respect to the roller (5) in order to ensure that the height (H6) of the gap is equal to a predetermined nominal height (H6_set), associated with a known radial tolerance (IT6), and the extrusion head (3) comprising seals (20) formed by beads (21) which axially delimit the gap (6), which protrude from the extrusion head (3) so as to be compressed against the roller (5) with a radial compression value which is at least equal to the minimum value of a predetermined radial interference (H_interf).

Description

INSTALLATION DE COEXTRUSION COMPRENANT DES CORDONS D’ÉTANCHÉITÉ QUI SONT ÉCRASÉS CONTRE LE ROULEAU LORS DE LA FERMETURE DE LA TÊTE D’EXTRUSION CO-EXTRUSION INSTALLATION INCLUDING SEALING CORDS THAT ARE CRUSHED AGAINST THE ROLLER WHEN THE EXTRUSION HEAD IS CLOSED
[0001] La présente invention concerne le domaine général des installations de coextrusion destinées à produire des profilés en assemblant, à travers une tête d’extrusion pourvue d’une filière, plusieurs mélanges élastomériques qui sont acheminés conjointement jusqu’à ladite tête d’extrusion par une pluralité d’extrudeuses. The present invention relates to the general field of coextrusion installations intended to produce profiles by assembling, through an extrusion head provided with a die, several elastomeric mixtures which are conveyed together to said extrusion head by a plurality of extruders.
[0002] La présente invention concerne plus particulièrement les installations de coextrusion destinées à produire des profilés qui entrent dans la composition de bandages pour roues de véhicules, par exemple des profilés destinés à former des bandes de roulement ou des flancs de bandages, en particulier de bandages pneumatiques. The present invention relates more particularly to coextrusion installations intended to produce profiles which enter into the composition of tires for vehicle wheels, for example profiles intended to form treads or sidewalls of tires, in particular pneumatic tires.
[0003] Il est connu d’utiliser des installations de coextrusion comprenant d’une part un rouleau, qui est entraîné en rotation et qui présente une surface de réception cylindrique recevant les mélanges élastomériques et accompagnant l’écoulement du profilé, et d’autre part une tête qui coopère avec ledit rouleau pour définir un entrefer dont la forme et les dimensions déterminent la section du profilé. It is known to use coextrusion installations comprising on the one hand a roller, which is driven in rotation and which has a cylindrical receiving surface receiving the elastomeric mixtures and accompanying the flow of the profile, and on the other share a head which cooperates with said roller to define an air gap, the shape and dimensions of which determine the section of the profile.
[0004] Afin d’éviter les fuites de mélanges élastomériques hors de l’entrefer, il est connu, par le document EP-0 201 337, de fixer sur la tête d’extrusion, de chaque côté de l’entrefer, des patins d’étanchéité auto-lubrifïés qui viennent au contact de la surface du rouleau avec un léger jeu permettant au rouleau de glisser sur lesdits patins. [0004] In order to prevent elastomeric compounds from leaking out of the air gap, it is known, from document EP-0 201 337, to fix on the extrusion head, on each side of the air gap, pads self-lubricated seals which come into contact with the surface of the roller with a slight clearance allowing the roller to slide on said pads.
[0005] Toutefois, une telle solution est délicate à mettre en œuvre, dans la mesure où il est nécessaire de disposer de moyens de réglage qui permettent d’ajuster précisément, à chaque nouveau tirage, c’est-à-dire à chaque lancement d’une nouvelle opération d’extrusion d’un profilé, la position radiale des patins par rapport à la surface du rouleau, en fonction notamment du degré d’usure desdits patins. Un tel réglage est en effet indispensable afin d’obtenir un montage glissant qui ne soit ni trop lâche, pour que les patins ne laissent pas fuir un ou des matériaux extradés, ni serré, afin que les patins ne génèrent pas un frottement excessif qui pourrait gêner voir bloquer la rotation du rouleau, et causer ainsi une surconsommation d’énergie ou des irrégularités dans l’écoulement des mélanges, irrégularités qui seraient susceptibles de faire apparaître des défauts dans la géométrie ou les dimensions du profilé. [0005] However, such a solution is difficult to implement, insofar as it is necessary to have adjustment means which make it possible to precisely adjust, with each new draw, that is to say with each launch of a new operation of extrusion of a profile, the radial position of the pads relative to the surface of the roller, depending in particular on the degree of wear of said pads. Such an adjustment is indeed essential in order to obtain a sliding assembly which is neither too loose, so that the pads do not leak one or more extruded materials, nor tight, so that the pads do not generate excessive friction which could hinder or even block the rotation of the roller, and thus cause an overconsumption of energy or irregularities in the flow of the mixtures, irregularities which could lead to defects in the geometry or dimensions of the profile.
[0006] En outre, la nécessité de recommencer les opérations de réglage de jeu à chaque nouveau tirage cause d’importantes pertes de temps, ce qui rend l’installation d’extrusion difficilement compatible avec des changements fréquents de production, lorsqu’il est nécessaire de fabriquer successivement, au moyen de la même installation d’extrusion, une grande variété de profilés différents, chacun en petite série. [0006] In addition, the need to start the clearance adjustment operations again with each new print causes significant loss of time, which makes the extrusion installation difficult to reconcile with frequent production changes, when it is necessary to manufacture successively, by means of the same extrusion installation, a wide variety of different profiles, each in small series.
[0007] Par ailleurs, les profilés actuels tendent à devenir de plus en plus complexes, et donc à faire intervenir un nombre élevé de mélanges élastomériques qui se combinent au sein de la section du profilé, typiquement cinq, six voire sept mélanges élastomériques différents, ce qui a pour conséquence d’augmenter la « longueur mouillée », c’est-à-dire la distance, considérée selon la direction d’écoulement du profilé, ici donc selon la direction circonférentielle du rouleau, sur laquelle ledit profilé doit impérativement rester captif de l’entrefer, entre le rouleau et la tête d’extrusion, pour que l’on puisse garantir la cohésion entre eux des différents mélanges élastomériques au sein dudit profilé. [0007] Furthermore, current profiles tend to become more and more complex, and therefore to involve a large number of elastomeric compounds which combine within the section of the profile, typically five, six or even seven different elastomeric compounds, which has the consequence of increasing the "wet length", that is to say the distance, considered according to the direction of flow of the profile, here therefore according to the circumferential direction of the roller, on which said profile must imperatively remain captive of the air gap, between the roller and the extrusion head, so that the cohesion between them of the various elastomeric mixtures within said profile can be guaranteed.
[0008] Or, il est particulièrement malaisé, voire impossible, d’assurer une étanchéité au moyen de patins connus sur une longueur mouillée importante, car le risque d’erreur dans le réglage du jeu est alors significativement accru, ainsi que les conséquences d’un mauvais réglage de jeu en matière de fuite ou au contraire de blocage du rouleau. [0008] However, it is particularly difficult, if not impossible, to ensure sealing by means of known pads over a long wet length, because the risk of error in adjusting the clearance is then significantly increased, as well as the consequences of 'a bad clearance adjustment in terms of leakage or on the contrary blocking of the roller.
[0009] De surcroît, les mélanges élastomériques désormais utilisés, notamment dans l’industrie du bandage pneumatique, pour former la sous-couche du profilé, c’est-à-dire la première couche de mélange élastomérique déposée, qui est donc en contact direct avec la surface du rouleau, et par-dessus laquelle s’empilent les couches formées par les autres mélanges élastomériques, tendent à être de plus en plus fluides, ce qui impose de renforcer l’étanchéité entre la tête d’extrusion et le rouleau pour éviter des fuites et une malformation de ladite sous-couche du profilé. [0009] In addition, the elastomeric compounds now used, in particular in the tire industry, to form the underlayer of the profile, that is to say the first layer of elastomeric compound deposited, which is therefore in contact directly with the surface of the roller, and on top of which the layers formed by the other elastomeric compounds are stacked, tend to be more and more fluid, which makes it necessary to reinforce the seal between the extrusion head and the roller to avoid leaks and malformation of said underlayer of the profile.
[0010] Les objets assignés à l’invention visent par conséquent à remédier aux inconvénients susmentionnés et proposer une nouvelle installation d’extrusion qui garantisse de manière simple et reproductible une étanchéité efficace entre la tête d’extrusion et le rouleau, sans gêner la rotation du rouleau ni nécessiter un réglage de jeu complexe à chaque tirage. [0010] The objects assigned to the invention therefore aim to remedy the aforementioned drawbacks and to propose a new extrusion installation which guarantees, in a simple and reproducible manner, an effective seal between the extrusion head and the roller, without interfering with roller rotation or requiring complex slack adjustment with each draw.
[0011] Les objets assignés à l’invention sont atteints au moyen d’une installation de coextrusion destinée à générer un profilé en extradant conjointement une pluralité de mélanges élastomériques selon une direction d’écoulement commune, ladite installation comprenant une tête d’extrusion destinée à amener les mélanges élastomériques, un rouleau qui est entraîné en rotation sur lui-même autour d’un axe central, et un système de fermeture conçu pour faire passer alternativement l’installation d’une configuration d’ouverture, dans laquelle la tête d’extrusion est éloignée du rouleau, à une configuration de fermeture, dans laquelle la tête d’extrusion est rapprochée du rouleau afin de définir avec ledit rouleau un entrefer servant à conformer la section du profilé, lequel entrefer s’étend selon une première dimension dite « hauteur » portée par une direction radiale perpendiculaire à l’axe central, selon une seconde dimension dite « largeur » portée par une direction axiale parallèle à l’axe central, et selon une troisième dimension dite « longueur mouillée » qui est portée par la direction d’écoulement commune et qui représente une portion de la circonférence du rouleau, ladite installation étant caractérisée en ce que le système de fermeture comporte un mécanisme à butée qui est agencé pour positionner de manière reproductible la tête d’extrusion par rapport au rouleau en configuration de fermeture afin de garantir que, dans ladite configuration de fermeture, la hauteur de l’entrefer est égale à une hauteur nominale prédéterminée, assortie d’une tolérance radiale connue, et en ce que ladite installation comprend au moins un joint d’étanchéité, destiné à venir délimiter la largeur de l’entrefer afin d’empêcher les mélanges élastomériques de fuir axialement hors de l’entrefer, ledit joint d’étanchéité étant fixé à la tête d’extrusion de sorte d’une part à pouvoir couvrir la longueur mouillée dans la configuration de fermeture, et d’autre part à faire saillie radialement par rapport à la tête d’extrusion, d’une valeur qui, lorsque la tête d’extrusion est en configuration d’ouverture, est dite « hauteur de saillie brute » et est strictement supérieure, d’une valeur non nulle dite « valeur minimale d’interférence radiale », à la hauteur maximale possible de l’entrefer qui est attendue en configuration de fermeture en tenant compte de la hauteur nominale de l’entrefer et de la tolérance radiale connue, de sorte que, lorsque le système de fermeture fait passer l’installation en configuration de fermeture, la tête d’extrusion force l’écrasement radial du joint d’étanchéité en compression contre le rouleau, d’une valeur de compression radiale qui est au moins égale à la valeur minimale d’interférence radiale. [0011] The objects assigned to the invention are achieved by means of a coextrusion installation intended to generate a profile by jointly extraditing a plurality of elastomeric mixtures along a common direction of flow, said installation comprising an extrusion head intended to feed the elastomeric compounds, a roller which is driven in rotation on itself around a central axis, and a closing system designed to alternately pass the installation of an opening configuration, in which the head of extrusion is moved away from the roller, in a closed configuration, in which the extrusion head is brought closer to the roller in order to define with said roller an air gap serving to conform the section of the profile, which air gap extends along a first dimension called "height" carried by a radial direction perpendicular to the central axis, according to a second dimension called "width" carried by an axial direction parallel to the central axis, and according to a third dimension called "wet length" which is carried by the common direction of flow and which represents a portion of the circumference of the roll, said installation being characterized in that the closing system comprises a stop mechanism which is arranged to position the extrusion head in a reproducible manner with respect to the roll in closed configuration in order to guarantee that, in said closed configuration, the height of the air gap is equal to a predetermined nominal height, together with a known radial tolerance, and in that said installation comprises at least one seal , intended to come to delimit the width of the air gap in order to prevent the elastomeric mixtures from leaking axially out of the air gap, said sealing gasket being fixed to the extrusion head so as on the one hand to be able to cover the wetted length in the closed configuration, and on the other hand to protrude radially with respect to the extrusion head, by a value which, when the extrusion head is in the open configuration, is called "height of gross protrusion" and is strictly greater, by a non-zero value called "minimum radial interference value", than the maximum possible height of the air gap which is expected in the closed configuration, taking into account the nominal height of the air gap and the known radial tolerance, so that, when the closing system brings the installation into the closing configuration, the extrusion head forces the radial crushing of the compression seal against the roller, with a radial compression value which is at least equal to the minimum radial interference value.
[0012] Avantageusement, selon l’invention, c’est la déformabilité intrinsèque du joint d’étanchéité, combinée au fait que ledit joint est intentionnellement dimensionné de manière à être pris en sandwich et systématiquement comprimé entre la tête d’extrusion et le rouleau, grâce à l’existence d’une valeur minimale d’interférence radiale choisie, qui permettent audit joint de s’ajuster, par déformation spontanée, à l’entrefer existant, et notamment qui permettent audit joint d’absorber, par un écrasement radial plus ou moins prononcé, les éventuelles tolérances d’usinage et d’assemblage de la tête d’extrusion, du rouleau, et du système de fermeture, ainsi que les éventuelles variations de la hauteur radiale de l’entrefer le long de la longueur mouillée. [0012] Advantageously, according to the invention, it is the intrinsic deformability of the seal, combined with the fact that said seal is intentionally dimensioned so as to be sandwiched and systematically compressed between the extrusion head and the roller. , thanks to the existence of a chosen minimum value of radial interference, which allow said joint to adjust, by spontaneous deformation, to the existing air gap, and in particular which allow said joint to absorb, by radial crushing more or less pronounced, any machining and assembly tolerances of the extrusion head, the roller, and the closing system, as well as any variations in the radial height of the air gap along the wetted length .
[0013] Ainsi, le joint d’étanchéité selon l’invention est apte à combler totalement, et à coup sûr, à chaque fermeture de l’installation, la hauteur radiale de l’entrefer, en épousant sur toute la longueur mouillée aussi bien la surface du rouleau que la surface de la tête d’extrusion située en vis-à-vis de la surface dudit rouleau, sans laisser subsister de jeu radial, et donc sans laisser subsister d’interstice qui serait susceptible de laisser fuir latéralement l’un ou l’autre des mélanges élastomériques. [0013] Thus, the seal according to the invention is able to fill completely, and for sure, each time the installation is closed, the radial height of the air gap, by marrying over the entire wetted length as well the surface of the roller than the surface of the extrusion head located opposite the surface of said roller, without leaving any radial clearance, and therefore without leaving any gap which would be likely to let the one or the other of the elastomeric mixtures.
[0014] Avantageusement, grâce à l’invention, il n’est plus nécessaire, comme le prévoyaient les installations connues, de modifier et d’adapter à chaque nouveau tirage, en fonction de la hauteur et de l’usure constatée de patins d’étanchéité rigides, le réglage fixe qui détermine la distance qui sépare la tête d’extrusion du rouleau en configuration de fermeture, en ajustant avant chaque nouvelle fermeture ladite valeur de réglage fixe de telle manière que l’on obtienne un contact glissant et sans contrainte des patins contre le rouleau. En effet, l’invention propose au contraire un système de fermeture qui définit une position unique et reproductible de la tête d’extrusion par rapport au rouleau, avec une légère plage de tolérance connue et maîtrisée, c’est-à-dire un système de fermeture qui permet de conserver une même valeur de réglage fixe d’un tirage à l’autre tirage, et donc pour plusieurs fermetures successives, mais qui laisse au joint d’étanchéité le soin de compenser automatiquement, à chaque fermeture, les éventuelles variations de positionnement radial comprises dans ladite plage de tolérance, par une déformation radiale adaptée, et spontanée, dudit joint sous la contrainte de compression radiale qui est induite par l’existence de l’interférence radiale choisie. [0014] Advantageously, thanks to the invention, it is no longer necessary, as provided for in known installations, to modify and adapt to each new print, depending on the height and observed wear of the pads. rigid seals, the fixed adjustment which determines the distance which separates the extrusion head from the roller in the closed configuration, by adjusting before each new closing said fixed adjustment value in such a way that a sliding and stress-free contact is obtained pads against the roller. Indeed, the invention proposes on the contrary a closing system which defines a unique and reproducible position of the extrusion head with respect to the roller, with a slight known and controlled tolerance range, that is to say a system which makes it possible to maintain the same fixed adjustment value from one pull to the next, and therefore for several successive closings, but which leaves it to the seal to automatically compensate, at each closing, any variations of radial positioning included in said tolerance range, by a suitable and spontaneous radial deformation, said seal under the radial compressive stress which is induced by the existence of the chosen radial interference.
[0015] L’invention permet donc avantageusement au système de fermeture de placer la tête d’extrusion en vis-à-vis du rouleau « à l’aveugle », dans la position nominale repérée par la butée, sans qu’il soit nécessaire de réaliser au préalable un quelconque réglage de la position des organes du système de fermeture qui définissent la position de la tête d’extrusion, et plus particulièrement qui définissent la position des éléments rigides et fixes appartenant à ladite tête d’extrusion, par rapport à la position du rouleau, en configuration de fermeture. The invention therefore advantageously allows the closure system to place the extrusion head facing the "blind" roller, in the nominal position marked by the stopper, without it being necessary to carry out beforehand any adjustment of the position of the members of the closure system which define the position of the extrusion head, and more particularly which define the position of the rigid and fixed elements belonging to said extrusion head, with respect to the position of the roller, in the closed configuration.
[0016] On économise ainsi un temps précieux lors du passage d’un tirage au tirage suivant, puisque aucune opération de réglage de jeu n’est nécessaire entre les deux tirages consécutifs. [0016] This saves valuable time when switching from one draw to the next draw, since no clearance adjustment operation is necessary between the two consecutive draws.
[0017] Avantageusement, le système de fermeture selon l’invention permet en outre de dissocier la précharge fonctionnelle de fermeture d’une part, c’est-à-dire l’intensité de l’effort qui force le rapprochement de la tête vers le rouleau en plaquant, par l’intermédiaire de la butée, le support de la tête d’extrusion dans une position nominale prédéterminée contre les paliers supportant et guidant le rouleau, de la précharge radiale fonctionnelle d’étanchéité d’autre part, c’est-à-dire de l’intensité de l’effort avec lequel le ou les joints d’étanchéité portés par la tête appuient sur le rouleau et sont comprimés contre ledit rouleau, en configuration de fermeture, et plus particulièrement en fonctionnement pendant un tirage. Advantageously, the closure system according to the invention also makes it possible to dissociate the functional preload of closure on the one hand, that is to say the intensity of the effort which forces the approximation of the head towards the roller by pressing, via the abutment, the support of the extrusion head in a predetermined nominal position against the bearings supporting and guiding the roller, of the functional radial preload of sealing on the other hand, it that is to say the intensity of the force with which the seal or seals carried by the head press on the roller and are compressed against said roller, in the closed configuration, and more particularly in operation during a draw .
[0018] Ainsi, en particulier, il est possible d’exercer une précharge de fermeture très élevée, typiquement supérieure ou égale à dix tonnes (c’est-à-dire, par convention, un effort équivalent au poids d’une masse de dix tonnes) et même de l’ordre de plusieurs dizaines de tonnes, afin d’empêcher la tête d’extrusion d’être écartée du rouleau sous l’effet de la pression de service qu’exercent les mélanges extrudés qui circulent dans l’entrefer, ce qui permet d’éviter toute altération de la hauteur de l’entrefer pendant un tirage, et ce sans pour autant que le joint d’étanchéité n’appuie, et donc ne frotte, trop fortement sur le rouleau, puisque la précharge radiale fonctionnelle d’étanchéité exercée par le joint d’étanchéité sur le rouleau est quant à elle typiquement de l’ordre de quelques centaines de kilogrammes, de préférence inférieure à 2 tonnes, plus préférentiellement inférieure à 1 tonne, par exemple comprise entre 100 kg et 800 kg, c’est-à-dire que ladite précharge radiale fonctionnelle d’ étanchéité est négligeable, à savoir ici inférieure d’un facteur égal ou supérieur à 10, voire égal ou supérieur à 50, par rapport à la précharge fonctionnelle de fermeture. [0018] Thus, in particular, it is possible to exert a very high closing preload, typically greater than or equal to ten tons (that is to say, by convention, a force equivalent to the weight of a mass of ten tons) and even of the order of several tens of tons, in order to prevent the extrusion head from being moved away from the roller under the effect of the operating pressure exerted by the extruded mixtures circulating in the air gap, which makes it possible to avoid any alteration of the height of the air gap during a draw, and this without the sealing gasket pressing, and therefore rubbing, too strongly on the roller, since the preload functional radial sealing exerted by the seal on the roller is typically of the order of a few hundred kilograms, preferably less than 2 tons, more preferably less than 1 ton, for example between 100 kg and 800 kg, i.e. said functional radial preload tightness is negligible, namely here less by a factor equal to or greater than 10, or even equal to or greater than 50, relative to the functional closing preload.
[0019] Bien entendu, la forme du joint d’étanchéité, notamment la largeur dudit joint considérée selon la direction de l’axe central, la valeur d’interférence radiale minimale, ainsi que le matériau constitutif du joint d’étanchéité, seront choisis de manière à ce que l’étendue de l’aire de contact qui se crée entre le rouleau et le joint d’étanchéité, ainsi que la pression de contact qui règne dans ladite aire de contact, soient d’une part suffisamment élevées pour garantir une étanchéité satisfaisante, notamment lorsque la hauteur radiale de l’entrefer correspond à la plus grande hauteur radiale possible au vu de la hauteur nominale et de la plage de tolérance applicable, et d’autre part suffisamment modérées pour éviter qu’un frottement excessif n’entrave la bonne rotation du rouleau en glissement sur le joint d’étanchéité, notamment lorsque la hauteur radiale de l’entrefer correspond à la plus petite hauteur radiale possible au vu de la hauteur nominale et de la plage de tolérance applicable. [0019] Of course, the shape of the seal, in particular the width of said seal considered along the direction of the central axis, the minimum radial interference value, as well as the material constituting the seal, will be chosen. so that the extent of the contact area which is created between the roller and the seal, as well as the contact pressure which prevails in said contact area, are on the one hand sufficiently high to guarantee satisfactory sealing, in particular when the radial height of the air gap corresponds to the greatest radial height possible in view of the nominal height and the applicable tolerance range, and on the other hand sufficiently moderate to prevent excessive friction n hinders the proper rotation of the sliding roller on the seal, in particular when the radial height of the air gap corresponds to the smallest possible radial height given the nominal height and the applicable tolerance range.
[0020] Selon une possibilité particulièrement préférentielle d’utilisation, on pourra prévoir que le joint d’étanchéité est sacrifïable, c’est-à-dire à usage unique, et est remplacé par un joint d’étanchéité neuf après chaque tirage, lors de l’ouverture de l’installation qui précède chaque nouveau tirage. A cet effet, on choisira un mode de fixation du joint d’étanchéité sur la tête qui sera particulièrement simple et rapide à mettre en œuvre, comme cela sera détaillé plus bas. [0020]According to a particularly preferential possibility of use, provision may be made for the seal to be sacrificed, that is to say for single use, and is replaced by a new seal after each draw, when of the opening of the installation which precedes each new draw. For this purpose, we will choose a method of fixing the seal on the head which will be particularly simple and quick to implement, as will be detailed below.
[0021] D’autres objets, caractéristiques et avantages de l’invention apparaîtront plus en détail à la lecture de la description qui suit, ainsi qu’à l’aide des dessins annexés, fournis à titre purement illustratif et non limitatif, parmi lesquels : Other objects, characteristics and advantages of the invention will appear in more detail on reading the description which follows, as well as with the aid of the appended drawings, provided for purely illustrative and non-limiting purposes, among which :
[0022] La figure 1 illustre, selon une vue schématique en perspective, une installation de coextrusion selon l’invention. Figure 1 illustrates, in a schematic perspective view, a coextrusion installation according to the invention.
[0023] La figure 2 illustre, selon une vue de détail en perspective, la tête d’extrusion utilisée par l’installation de la figure 1, ladite tête d’extrusion comprenant deux joints d’étanchéité formés par des cordons qui s’étendent en longueur selon la direction circonférentielle du rouleau et qui sont logés dans des rainures creusées dans la tête d’extrusion ; par commodité de représentation, on a également schématisé en trait pointillé, sur cette même figure 2, une vue agrandie d’un cordon avant insertion. [0024] La figure 3 illustre, selon une vue de détail en coupe dans un plan radial contenant l’axe du rouleau, une première variante de joint d’étanchéité, à section circulaire, qui est logé dans une rainure de la tête d’extrusion des figures 1 et 2. Sur cette vue, le joint d’étanchéité est représenté fictivement dans sa forme avant écrasement radial, de sorte à faire apparaître la hauteur radiale d’interférence entre ledit joint d’étanchéité et le rouleau. [0023] Figure 2 illustrates, in a perspective detail view, the extrusion head used by the installation of Figure 1, said extrusion head comprising two seals formed by cords which extend in length in the circumferential direction of the roll and which are housed in grooves dug in the extrusion head; for ease of representation, there is also shown in dotted line, in this same figure 2, an enlarged view of a cord before insertion. [0024] Figure 3 illustrates, according to a detail view in section in a radial plane containing the axis of the roller, a first variant of a seal, of circular section, which is housed in a groove of the head of extrusion of Figures 1 and 2. In this view, the seal is shown fictitiously in its shape before radial crushing, so as to show the radial height of interference between said seal and the roller.
[0025] La figure 4 illustre, selon une vue de détail en coupe dans un plan radial contenant l’axe du rouleau, une seconde variante de joint d’étanchéité possédant une section à méplat et qui est logé dans une rainure de la tête d’extrusion des figues 1 et 2, et fait apparaître la hauteur d’interférence entre le joint d’étanchéité et le rouleau. [0025] Figure 4 illustrates, according to a detail view in section in a radial plane containing the axis of the roller, a second variant of a seal having a flattened section and which is housed in a groove of the head of extrusion of Figs 1 and 2, and shows the height of interference between the seal and the roller.
[0026] La figure 5 illustre, selon une vue de détail en coupe dans un plan radial contenant l’axe du rouleau, une troisième variante de joint d’étanchéité à deux lèvres, logé dans une rainure de la tête d’extrusion des figues 1 et 2, et fait apparaître la hauteur d’interférence entre le joint d’étanchéité et le rouleau. [0026] Figure 5 illustrates, according to a detail view in section in a radial plane containing the axis of the roller, a third variant of a two-lip seal, housed in a groove of the fig extrusion head 1 and 2, and shows the interference height between the seal and the roller.
[0027] La présente invention concerne une installation 1 de coextrusion destinée à générer un profilé 2 en extradant conjointement une pluralité de mélanges élastomériques Ml, M2, M3 selon une direction d’écoulement commune L2. The present invention relates to a coextrusion installation 1 intended to generate a profile 2 by jointly extraditing a plurality of elastomeric mixtures M1, M2, M3 in a common flow direction L2.
[0028] De façon connue en soi, la coextrusion consiste à réunir et juxtaposer lesdits mélanges élastomériques Ml, M2, M3 en un seul et même profilé 2, en répartissant lesdits mélanges élastomériques de sorte que ceux-ci cohabitent dans la section du profilé, chacun selon une ou des positions et une ou des formes qui ont été assignées au mélange élastomérique considéré. In a manner known per se, the coextrusion consists in bringing together and juxtaposing said elastomeric mixtures M1, M2, M3 in one and the same profile 2, by distributing said elastomeric mixtures so that they coexist in the section of the profile, each according to one or more positions and one or more shapes which have been assigned to the elastomeric mixture under consideration.
[0029] La direction d’écoulement commune L2 correspond à la direction longitudinale du profilé 2, selon laquelle ledit profilé 2 est produit en continu, en un seul tenant. [0029] The common direction of flow L2 corresponds to the longitudinal direction of profile 2, in which said profile 2 is produced continuously, in one piece.
[0030] De façon connue en soi, l’installation 1 comprend une tête d’extrusion 3 qui est destinée à amener les mélanges élastomériques Ml, M2, M3. In a manner known per se, the installation 1 comprises an extrusion head 3 which is intended to bring the elastomeric mixtures M1, M2, M3.
[0031] Ladite tête d’extrusion 3 comprend à cet effet une pluralité de canaux Cl, C2, C3 distincts, en nombre au moins égal au nombre de mélanges élastomériques utilisés, chaque canal Cl, C2, C3 étant raccordé à une extrudeuse qui délivre le mélange élastomérique Ml, M2, M3 correspondant. [0032] La tête d’extrusion 3 peut comprendre, tel que cela est visible sur la figure 3, une pluralité de lames 4, juxtaposées les unes aux autres, qui délimitent les canaux Cl, C2, C3 et permettent de conformer les différents flux des mélanges élastomériques Ml, M2, M3. Said extrusion head 3 comprises for this purpose a plurality of distinct channels Cl, C2, C3, in number at least equal to the number of elastomeric compounds used, each channel Cl, C2, C3 being connected to an extruder which delivers the corresponding elastomeric mixture M1, M2, M3. The extrusion head 3 may comprise, as can be seen in Figure 3, a plurality of blades 4, juxtaposed to each other, which delimit the channels C1, C2, C3 and make it possible to conform the different flows elastomeric mixtures M1, M2, M3.
[0033] L’installation 1 comprend également un rouleau 5 qui est entraîné en rotation R5 sur lui-même autour d’un axe central Y5. The installation 1 also includes a roller 5 which is rotated R5 on itself around a central axis Y5.
[0034] Ledit rouleau 5 présente une forme cylindrique de base circulaire centrée sur ledit axe central Y5. La surface cylindrique apparente, convexe, dudit rouleau 5 forme une surface de réception qui est destinée à recevoir les mélanges élastomériques et à accompagner le profilé 2, au fur et à mesure de sa génération, dans son mouvement d’avance selon la direction d’écoulement L2. Said roller 5 has a cylindrical shape with a circular base centered on said central axis Y5. The apparent cylindrical surface, convex, of said roller 5 forms a receiving surface which is intended to receive the elastomeric mixtures and to accompany the profile 2, as it is generated, in its forward movement in the direction of L2 flow.
[0035] Le rouleau 5 est de préférence réalisé en métal, par exemple en acier. La surface dudit rouleau 5 est avantageusement polie, pour limiter l’encrassement du rouleau 5 par les mélanges élastomériques. De préférence, la surface du rouleau 5 est traitée pour atteindre une dureté égale ou supérieure à 1000 HV (dureté Vickers), par exemple au moyen d’un chrome dur ou d’un dépôt en phase vapeur de nitrure de chrome CrN. The roller 5 is preferably made of metal, for example steel. The surface of said roller 5 is advantageously polished, to limit fouling of roller 5 by elastomeric compounds. Preferably, the surface of the roller 5 is treated to reach a hardness equal to or greater than 1000 HV (Vickers hardness), for example by means of a hard chrome or a vapor phase deposition of chromium nitride CrN.
[0036] De préférence, le diamètre du rouleau 5 est compris entre 300 mm et 1000 mm. Preferably, the diameter of roller 5 is between 300 mm and 1000 mm.
[0037] La tête d’extrusion 3 présente une forme concave, sensiblement conjuguée à celle du rouleau 5, ici donc une forme concave qui correspond sensiblement à une portion de cylindre de base circulaire, de manière à ce que ladite tête d’extrusion 3 puise venir coiffer un secteur angulaire du rouleau 5 pour définir un entrefer 6. [0037] The extrusion head 3 has a concave shape, substantially matching that of the roller 5, here therefore a concave shape which substantially corresponds to a circular base cylinder portion, so that said extrusion head 3 then comes to cover an angular sector of the roller 5 to define an air gap 6.
[0038] L’installation 1 comprend en outre un système de fermeture 10 qui est conçu pour faire passer alternativement l’installation 1 d’une configuration d’ouverture, dans laquelle la tête d’extrusion 3 est éloignée du rouleau 5, à une configuration de fermeture, dans laquelle la tête d’extrusion 3 est rapprochée du rouleau 5 afin de définir avec ledit rouleau 5 l’entrefer 6 servant à conformer la section du profilé 2. [0038] The installation 1 further comprises a closure system 10 which is designed to alternately pass the installation 1 from an open configuration, in which the extrusion head 3 is remote from the roller 5, to a closing configuration, in which the extrusion head 3 is brought closer to the roller 5 in order to define with said roller 5 the air gap 6 serving to conform the section of the profile 2.
[0039] Le système de fermeture 10 peut par exemple comprendre un ascenseur 11, agencé pour déplacer verticalement la tête d’extrusion 3 par rapport à un palier 12 qui soutient le rouleau 5 et qui guide ledit rouleau 5 en rotation. [0040] En pratique, la configuration d’ouverture permet notamment le nettoyage ou le remplacement de la tête d’extrusion 3. The closure system 10 may for example comprise an elevator 11, arranged to move the extrusion head 3 vertically relative to a bearing 12 which supports the roller 5 and which guides said roller 5 in rotation. [0040] In practice, the opening configuration makes it possible in particular to clean or replace the extrusion head 3.
[0041] En configuration de fermeture, l’entrefer 6 s’étend selon une première dimension dite « hauteur » H6 qui est portée par une direction radiale DR perpendiculaire à l’axe central Y5, selon une seconde dimension dite « largeur » W6 qui est portée par une direction axiale DA parallèle à l’axe central Y5, et selon une troisième dimension dite « longueur mouillée » L6 qui est portée par la direction d’écoulement commune L2 et qui représente une portion de la circonférence du rouleau 5. In the closed configuration, the air gap 6 extends along a first dimension called "height" H6 which is carried by a radial direction DR perpendicular to the central axis Y5, along a second dimension called "width" W6 which is carried by an axial direction DA parallel to the central axis Y5, and along a third dimension called "wet length" L6 which is carried by the common direction of flow L2 and which represents a portion of the circumference of the roller 5.
[0042] Par commodité de description, on désignera par « axiale » une direction parallèle à l’axe considéré, ici l’axe central Y5, par « radiale » une direction perpendiculaire audit axe considéré, et par « circonférentielle » une direction orthoradiale, c’est-à-dire qui, en un point considéré situé à distance de l’axe, est normale au plan radial qui contient l’axe considéré et qui passe par ledit point considéré. [0042] For convenience of description, "axial" will designate a direction parallel to the axis considered, here the central axis Y5, by "radial" a direction perpendicular to said axis considered, and by "circumferential" an orthoradial direction, that is to say which, at a point considered located at a distance from the axis, is normal to the radial plane which contains the axis considered and which passes through said point considered.
[0043] En pratique, la direction d’écoulement commune L2 coïncide avec la direction circonférentielle. Dans un plan normal à l’axe central Y5, direction d’écoulement commune L2 et direction circonférentielle sont donc tangentes à la surface du rouleau 5. In practice, the common flow direction L2 coincides with the circumferential direction. In a plane normal to the central axis Y5, common flow direction L2 and circumferential direction are therefore tangent to the surface of roller 5.
[0044] La longueur mouillée L6 est de préférence comprise entre 30 mm et 200 mm, ladite longueur mouillée L6 étant généralement d’autant plus grande que le nombre de mélanges élastomériques de compositions différentes entrant dans la constitution du profilé 2 est élevé. The wetted length L6 is preferably between 30 mm and 200 mm, said wetted length L6 generally being all the greater as the number of elastomeric compounds of different compositions entering into the constitution of the profile 2 is high.
[0045] De préférence, et notamment pour un rouleau 5 qui présente préférentiellement un diamètre compris entre 300 mm et 1000 mm comme indiqué plus haut, la longueur mouillée L6 couvre, en azimut autour de l’axe central Y5, une fraction du périmètre du rouleau 5, qui représente un secteur angulaire dont l’étendue est comprise entre 2 degrés et 40 degrés. Preferably, and in particular for a roller 5 which preferably has a diameter of between 300 mm and 1000 mm as indicated above, the wetted length L6 covers, in azimuth around the central axis Y5, a fraction of the perimeter of the roller 5, which represents an angular sector whose extent is between 2 degrees and 40 degrees.
[0046] Selon l’invention, et tel que cela est illustré sur la figure 1, le système de fermeture 10 comporte un mécanisme 13 à butée 14 qui est agencé pour positionner de manière reproductible la tête d’extrusion 3 par rapport au rouleau 5 en configuration de fermeture afin de garantir que, dans ladite configuration de fermeture, la hauteur H6 de l’entrefer 6 est égale à une hauteur nominale H6_set prédéterminée, assortie d’une tolérance radiale IT6 connue. [0047] A titre d’exemple, la butée 14 du mécanisme 13 peut correspondre à une surface du palier 12, par exemple la face inférieure de la semelle dudit palier 12, contre laquelle vient buter une portion de l’ascenseur 11, tel que cela est illustré sur la figure 1. According to the invention, and as illustrated in Figure 1, the closure system 10 comprises a mechanism 13 with abutment 14 which is arranged to position the extrusion head 3 in a reproducible manner with respect to the roller 5 in the closed configuration in order to guarantee that, in said closed configuration, the height H6 of the air gap 6 is equal to a predetermined nominal height H6_set, together with a known radial tolerance IT6. For example, the abutment 14 of the mechanism 13 may correspond to a surface of the bearing 12, for example the underside of the flange of said bearing 12, against which abuts a portion of the elevator 11, such as this is illustrated in Figure 1.
[0048] La mise en butée de l’ascenseur 11 contre le palier 12 marquera ainsi la fin de la course relative de la tête d’extrusion 3 par rapport au rouleau 5, dans le sens correspondant au rapprochement de la tête d’extrusion 3 vers le rouleau 5. The abutment of the elevator 11 against the bearing 12 will thus mark the end of the relative travel of the extrusion head 3 with respect to the roller 5, in the direction corresponding to the approximation of the extrusion head 3 to reel 5.
[0049] Par simple convention, on désignera la tolérance radiale IT6 sous forme d’un intervalle de tolérance défini d’une part par une valeur de tolérance basse, notée IT6_low, et d’autre part par une valeur de tolérance haute, notée ITô high : By simple convention, the radial tolerance IT6 will be designated in the form of a tolerance interval defined on the one hand by a low tolerance value, denoted IT6_low, and on the other hand by a high tolerance value, denoted ITô high:
IT6 = [IT6_low ; IT6 Jiigh] IT6 = [IT6_low; IT6 Jiigh]
[0050] Les valeurs de tolérance IT6_low, ITô high sont algébriques, c’est-à-dire pourront être l’une et/ou l’autre indifféremment positives ou négatives, dès lors que la valeur de tolérance basse IT6_low est strictement inférieure (algébriquement, c’est-à-dire en tenant compte du signe) à la valeur de tolérance haute ITô high : [0050] The tolerance values IT6_low, ITô high are algebraic, that is to say they may be one and/or the other, either positive or negative, provided that the low tolerance value IT6_low is strictly lower ( algebraically, i.e. taking the sign into account) to the high tolerance value ITô high:
IT6_low < ITô high IT6_low < ITô high
[0051] Ainsi, lorsque l’installation se trouve en configuration de fermeture, et plus particulièrement ici lorsque l’ascenseur 11 est en appui rigide et contraint par une précharge de fermeture F10 contre la butée 14 procurée par le palier 12, la hauteur H6 réelle de l’entrefer, dans la zone de référence choisie pour fixer la hauteur nominale H6_set, est comprise de façon certaine entre une hauteur minimale possible prédéterminée, connue à l’avance, et valant ici Thus, when the installation is in the closed configuration, and more particularly here when the elevator 11 is in rigid support and constrained by a closing preload F10 against the stop 14 provided by the bearing 12, the height H6 of the air gap, in the reference zone chosen to set the nominal height H6_set, is included with certainty between a predetermined minimum possible height, known in advance, and here being equal to
H6_min = H6_set + IT6_low compte-tenu de la convention adoptée ci-dessus, et une hauteur maximale possible prédéterminée, également connue à l’avance, et valant ici H6_min = H6_set + IT6_low taking into account the convention adopted above, and a predetermined maximum possible height, also known in advance, and valid here
H6_max = H6_set + ITô high, c’est-à-dire que l’on a, et que l’on sait avoir : H6_max = H6_set + ITô high, i.e. we have, and we know we have:
H6_set + IT6_low < H6_set < H6_set + ITô high H6_set + IT6_low < H6_set < H6_set + ITô high
[0052] Les sommes indiquées ci-dessus sont algébriques, c’est-à-dire doivent prendre en considération les signes respectifs des valeurs de tolérance basse IT6_low et haute ITô high. [0053] On notera également qu’il est équivalent, dans la finalité de l’invention, de considérer que la hauteur H6 effective de l’entrefer 6 est égale à une valeur nominale H6_set assortie d’une tolérance radiale IT6 connue, ou bien de considérer que la hauteur H6 effective de l’entrefer 6 est comprise de façon certaine entre une valeur minimale possible H6_min prédéterminée et une valeur maximale possible H6_max prédéterminée (lesquelles valeurs minimale et maximale forment les limites de l’intervalle obtenu en appliquant la tolérance radiale IT6 à la hauteur nominale H6_set). The sums indicated above are algebraic, that is to say must take into consideration the respective signs of the low tolerance values IT6_low and high ITô high. It will also be noted that it is equivalent, for the purpose of the invention, to consider that the effective height H6 of the air gap 6 is equal to a nominal value H6_set accompanied by a known radial tolerance IT6, or else to consider that the effective height H6 of the air gap 6 is comprised with certainty between a predetermined minimum possible value H6_min and a predetermined maximum possible value H6_max (which minimum and maximum values form the limits of the interval obtained by applying the radial tolerance IT6 at nominal height H6_set).
[0054] La tolérance radiale IT6 pourra être déterminée par simulation (chaînes de cotes, éléments finis, etc.) et/ou par des essais empiriques, et dépendra notamment des dimensions des organes constitutifs du mécanisme 13 du système de fermeture 10, du module d’ Young (ici en compression) desdits organes, et de la valeur de la précharge de fermeture F10 qui plaque l’ascenseur 11 contre la butée 14 du palier 12 afin d’empêcher la tête d’extrusion 13 d’être écartée radialement du rouleau 5 sous la pression des mélanges élastomériques Ml, M2, M3 présents dans l’entrefer 6. The radial tolerance IT6 can be determined by simulation (chains of dimensions, finite elements, etc.) and/or by empirical tests, and will depend in particular on the dimensions of the constituent parts of the mechanism 13 of the closing system 10, of the module of Young (here in compression) of said organs, and the value of the closing preload F10 which presses the elevator 11 against the stop 14 of the bearing 12 in order to prevent the extrusion head 13 from being moved radially away from the roller 5 under the pressure of the elastomeric mixtures M1, M2, M3 present in the air gap 6.
[0055] Selon l’invention, l’installation 1 comprend au moins un joint d’étanchéité 20 destiné à venir délimiter la largeur W6 de l’entrefer 6 afin d’empêcher les mélanges élastomériques Ml, M2, M3 de fuir axialement hors de l’entrefer 6. According to the invention, the installation 1 comprises at least one seal 20 intended to delimit the width W6 of the air gap 6 in order to prevent the elastomeric mixtures M1, M2, M3 from leaking axially out of air gap 6.
[0056] Plus préférentiellement, tel que cela est visible sur la figure 2, la tête d’extrusion 3 comprend deux joints d’étanchéité 20 distants axialement l’un de l’autre et qui définissent chacun l’une des limites axiales de l’entrefer 6, c’est-à-dire qui délimitent chacun l’une des lisières latérales de l’entrefer 6, de sorte que la largeur W6 de l’entrefer 6 correspond à la distance, de préférence constante sur la longueur mouillée L6, qui sépare axialement le premier joint d’étanchéité du second joint d’étanchéité. More preferably, as shown in Figure 2, the extrusion head 3 comprises two seals 20 axially spaced from each other and which each define one of the axial limits of the air gap 6, that is to say which each delimit one of the lateral edges of the air gap 6, so that the width W6 of the air gap 6 corresponds to the distance, preferably constant over the wetted length L6 , which axially separates the first seal from the second seal.
[0057] Selon l’invention, le joint d’étanchéité 20, le cas échéant chacun des deux joints d’étanchéité 20 susmentionnés, est fixé à la tête d’extrusion 3 de sorte à pouvoir, d’une part, couvrir la longueur mouillée L6 dans la configuration de fermeture. According to the invention, the seal 20, where applicable each of the two aforementioned seals 20, is fixed to the extrusion head 3 so as to be able, on the one hand, to cover the length wetted L6 in the closing configuration.
[0058] Ainsi, le joint d’étanchéité 20 retient avantageusement les mélanges élastomériques, et plus globalement le profilé 2, captifs de l’entrefer 6 sur la longueur nécessaire considérée pour la mise en forme dudit profilé 2. [0059] D’ autre part, et surtout, le joint d’étanchéité 20, le cas échéant chacun des deux joints d’étanchéité 20 susmentionnés, est fixé à la tête d’extrusion 3 de sorte à faire saillie radialement par rapport à la tête d’extrusion 3, d’une valeur qui, lorsque la tête d’extrusion 3 est en configuration d’ouverture, et plus particulièrement lorsque la tête d’extrusion 3 est en configuration d’ouverture et garnie d’un joint d’étanchéité 20 neuf, avant une première fermeture, est dite « hauteur de saillie brute » H20_pro et est strictement supérieure, d’une valeur non nulle dite « valeur minimale d’interférence radiale » H interf, à la hauteur maximale possible H6_max de l’entrefer 6 qui est attendue en configuration de fermeture en tenant compte de la hauteur nominale H6_set de l’entrefer et de la tolérance radiale IT6 connue. Thus, the seal 20 advantageously retains the elastomeric mixtures, and more generally the profile 2, captive of the air gap 6 over the necessary length considered for the shaping of said profile 2. [0059] On the other hand, and above all, the seal 20, where appropriate each of the two seals 20 mentioned above, is fixed to the extrusion head 3 so as to project radially with respect to the extrusion head 3, of a value which, when the extrusion head 3 is in the open configuration, and more particularly when the extrusion head 3 is in the open configuration and fitted with a seal of sealing 20 new, before a first closing, is called "gross projection height" H20_pro and is strictly greater, by a non-zero value called "minimum value of radial interference" H interf, to the maximum possible height H6_max of the air gap 6 which is expected in the closed configuration taking into account the nominal height H6_set of the air gap and the known radial tolerance IT6.
[0060] En d’autres termes, on a H20_pro > H6_max, avec, plus précisément, H20_pro = H6_max + H interf, soit ici H20_pro = H6_set + IT6_max + H interf In other words, we have H20_pro > H6_max, with, more precisely, H20_pro = H6_max + H interf, i.e. here H20_pro = H6_set + IT6_max + H interf
[0061] De la sorte, lorsque le système de fermeture 10 fait passer l’installation 1 en configuration de fermeture, et plus particulièrement lorsque le système de fermeture 10 réalise la première fermeture du joint d’étanchéité 20 considéré contre le rouleau 5, la tête d’extrusion 3 force l’écrasement radial du joint d’étanchéité 20, le cas échéant de chacun des deux joints d’étanchéité 20, en compression contre le rouleau 5, d’une valeur de compression radiale qui est au moins égale à la valeur minimale d’interférence radiale H interf. [0061] In this way, when the closure system 10 causes the installation 1 to pass into the closure configuration, and more particularly when the closure system 10 performs the first closure of the seal 20 considered against the roller 5, the extrusion head 3 forces the radial crushing of the seal 20, if applicable of each of the two seals 20, in compression against the roller 5, by a radial compression value which is at least equal to the minimum radial interference value H interf.
[0062] Ainsi, avantageusement, comme cela a été expliqué plus haut, on adapte automatiquement, dans chaque plan radial considéré le long de la longueur mouillée L6, la hauteur effective du joint d’étanchéité 20 à la valeur exacte de la hauteur effective H6 de l’entrefer 6, par une déformation spontanée du joint d’étanchéité 20 qui survient lors de la fermeture de l’installation, et dont l’ampleur s’ajuste automatiquement au cas par cas. Thus, advantageously, as explained above, the effective height of the seal 20 is automatically adapted, in each radial plane considered along the wetted length L6, to the exact value of the effective height H6. of the air gap 6, by a spontaneous deformation of the seal 20 which occurs when the installation is closed, and the extent of which is automatically adjusted on a case-by-case basis.
[0063] Ceci permet avantageusement de garantir une étanchéité efficace, sans qu’il soit nécessaire de prévoir un système additionnel de réglage de jeu, par exemple ici un système à vis qui permettrait de régler la position de la butée 14 à chaque nouvelle fermeture de l’installation. [0063] This advantageously makes it possible to guarantee effective sealing, without it being necessary to provide an additional clearance adjustment system, for example here a screw system which would make it possible to adjust the position of the stop 14 at each new closing of installation.
[0064] L’existence d’une valeur d’interférence H interf prédéterminée, choisie non nulle, permet de garantir que l’on observera systématiquement un certain écrasement du joint d’étanchéité 20 entre la tête d’extrusion 3 et le rouleau 5, puisque le joint d’étanchéité 20 sera comprimé et verra sa hauteur radiale diminuer d’au moins cette valeur d’interférence H interf sous l’effet de cette compression, et par conséquent que l’on aura, de manière systématique, un contact effectif du joint d’étanchéité 20 avec le rouleau, sur toute la longueur mouillée L6 souhaitée. [0064] The existence of a predetermined interference value H interf, chosen to be non-zero, makes it possible to guarantee that a certain crushing of the joint will be systematically observed. seal 20 between the extrusion head 3 and the roller 5, since the seal 20 will be compressed and will see its radial height decrease by at least this interference value H interf under the effect of this compression, and consequently that there will systematically be an effective contact of the seal 20 with the roller, over the entire wetted length L6 desired.
[0065] L’écrasement radial du joint d’étanchéité 20 compense avantageusement tout jeu radial prévisible, et garantit ainsi une étanchéité par contact, et ce tout en minimisant l’étendue de l’aire contact, et donc le frottement résistant, entre le joint d’étanchéité 20 et le rouleau 5. On notera que l’écrasement radial du joint d’étanchéité 20 pourra comprendre une composante d’écrasement radial plastique, c’est-à-dire une déformation radiale irréversible, du joint d’étanchéité 20. Si le joint d’étanchéité 20 est suffisamment souple, l’écrasement radial pourra être principalement voire totalement élastique. [0065] The radial crushing of the seal 20 advantageously compensates for any foreseeable radial play, and thus guarantees sealing by contact, and this while minimizing the extent of the contact area, and therefore the resisting friction, between the seal 20 and the roller 5. It will be noted that the radial crushing of the seal 20 may include a plastic radial crushing component, that is to say an irreversible radial deformation, of the seal 20. If the seal 20 is sufficiently flexible, the radial crushing may be mainly or even totally elastic.
[0066] La valeur minimale d’interférence radiale H interf est de préférence comprise entre 0,05 mm, correspondant à une valeur basse, et 1,00 mm, correspondant à une valeur haute. Le cas échéant, la valeur minimale d’interférence radiale H interf pourra être comprise entre 0,05 mm (valeur basse) et 0,50 mm (valeur haute). The minimum radial interference value H interf is preferably between 0.05 mm, corresponding to a low value, and 1.00 mm, corresponding to a high value. If necessary, the minimum radial interference value H interf may be between 0.05 mm (low value) and 0.50 mm (high value).
[0067] On choisit en effet la valeur minimale d’interférence radiale H interf, entre d’une part une valeur basse, non nulle, et bien entendu positive, qui est suffisamment élevée pour garantir que l’on observera effectivement, même si c’est seulement cette valeur basse qui s’applique, un écrasement radial effectif du joint d’étanchéité 20 qui soit suffisant pour assurer un contact étanche entre le joint d’étanchéité 20 et le rouleau 5, et d’autre part une valeur haute qui est suffisamment modérée pour que, même si ladite valeur haute est appliquée, on évite une dégradation sévère du joint par abrasion contre le rouleau, ou un freinage excessif voire un blocage de la rotation R5 du rouleau 5. [0067] In fact, the minimum radial interference value H interf is chosen between, on the one hand, a low, non-zero, and of course positive value, which is high enough to guarantee that we will effectively observe, even if c it is only this low value that applies, an effective radial crushing of the seal 20 which is sufficient to ensure leaktight contact between the seal 20 and the roller 5, and on the other hand a high value which is sufficiently moderate so that, even if said high value is applied, severe degradation of the seal by abrasion against the roller is avoided, or excessive braking or even blocking of rotation R5 of roller 5.
[0068] A titre indicatif, la hauteur nominale H6_set de l’entrefer 6 qui est destinée à être comblée par le joint d’étanchéité 20 est de préférence comprise entre 0,10 mm et 0,50 mm. Le choix de cette valeur peut notamment dépendre du diamètre du rouleau 5, ainsi que de la qualité de réalisation du profilé qui est demandée. As an indication, the nominal height H6_set of the air gap 6 which is intended to be filled by the seal 20 is preferably between 0.10 mm and 0.50 mm. The choice of this value may in particular depend on the diameter of the roller 5, as well as on the quality of production of the profile which is required.
[0069] La relative finesse de l’entrefer 6 à combler à l’aplomb radial du joint d’étanchéité 20 permet avantageusement de limiter la hauteur effective de joint d’étanchéité 20, et donc la surface de joint d’étanchéité 20, qui est exposée, en service, à la pression des mélanges élastomériques, ce qui permet par conséquent de réduire le risque d’une fuite qui surviendrait par décollement accidentel du joint de la surface du rouleau ou par déformation axiale locale dudit joint d’étanchéité 20 sous la pression des mélanges élastomériques. En outre, cette relative finesse de l’entrefer 6 permet également, même en cas de survenance d’une fuite, de limiter le débit de ladite fuite. The relative fineness of the air gap 6 to be filled radially plumb with the seal 20 advantageously makes it possible to limit the effective height of the seal 20, and therefore the seal surface 20, which is exposed, in service, to the pressure of the elastomeric compounds, which consequently makes it possible to reduce the risk of a leak which would occur by accidental detachment of the seal from the surface of the roller or by local axial deformation of said seal 20 under the pressure of the elastomeric mixtures. In addition, this relative thinness of the air gap 6 also makes it possible, even in the event of the occurrence of a leak, to limit the flow rate of said leak.
[0070] De préférence, et tel que cela est visible sur la figure 2, le joint d’étanchéité 20 est formé par un cordon 21 qui présente au repos, avant mise en place sur la tête d’extrusion 3, une longueur L21 qui est strictement supérieure, de préférence au moins 10 fois supérieure, et plus préférentiellement au moins 50 fois supérieure, voire au moins 100 fois supérieure, à la largeur axiale hors-tout W21 dudit cordon 21 au repos. [0070] Preferably, and as shown in Figure 2, the seal 20 is formed by a bead 21 which has at rest, before being placed on the extrusion head 3, a length L21 which is strictly greater, preferably at least 10 times greater, and more preferably at least 50 times greater, or even at least 100 times greater, than the overall axial width W21 of said bead 21 at rest.
[0071] Le joint d’étanchéité 20 est donc de préférence un élément allongé, fïlaire, qui présente, en configuration de fermeture, une faible surface de contact, particulièrement étroite, avec le rouleau 5, et qui génère donc un frottement relativement faible à l’encontre de la rotation R5 du rouleau 5. The seal 20 is therefore preferably an elongated, wired element which, in the closed configuration, has a small, particularly narrow contact surface with the roller 5, and which therefore generates relatively low friction at against rotation R5 of roller 5.
[0072] Un tel joint d’étanchéité 20 sous forme de cordon 21 est en outre facile et peu onéreux à fabriquer, par exemple par extrusion, et à couper à la longueur souhaitée. Such a seal 20 in the form of cord 21 is also easy and inexpensive to manufacture, for example by extrusion, and to cut to the desired length.
[0073] De préférence la longueur L21 au repos du cordon 21 est comprise entre 30 mm et 200 mm. Preferably the length L21 at rest of the cord 21 is between 30 mm and 200 mm.
[0074] Ainsi, la longueur L21 du cordon 21 est de préférence égale à la longueur mouillée L6 souhaitée, et en tout cas suffisante pour couvrir d’un seul tenant toute la longueur mouillée L6. Thus, the length L21 of the cord 21 is preferably equal to the desired wetted length L6, and in any case sufficient to cover the entire wetted length L6 in one piece.
[0075] La largeur axiale hors-tout W21 du cordon 21 au repos sera de préférence comprise entre 2,00 mm et 10,00 mm. The overall axial width W21 of cord 21 at rest will preferably be between 2.00 mm and 10.00 mm.
[0076] De préférence, le cordon 21 présente une forme cylindrique. Preferably, cord 21 has a cylindrical shape.
[0077] Un tel cordon 21 de forme cylindrique présente notamment l’avantage de pouvoir être produit aisément par extrusion en grande longueur, puis coupé à la longueur L21 souhaitée. [0078] La section de base S21 de ladite forme cylindrique est de préférence choisie parmi :Such a cord 21 of cylindrical shape has the particular advantage of being easily produced by extrusion in great length, then cut to the desired length L21. The base section S21 of said cylindrical shape is preferably chosen from:
- selon une première variante illustrée sur la figure 3, une section de base S21 circulaire, dont le diamètre correspondra alors à la largeur axiale hors-tout W21 susmentionnée, - according to a first variant illustrated in Figure 3, a circular base section S21, the diameter of which will then correspond to the above-mentioned overall axial width W21,
- selon une seconde variante illustrée sur la figure 4, une section de base S21 à méplat 22 dont la partie destinée à faire saillie hors de la tête d’extrusion 3 est pourvue d’un méplat 22 parallèle à la surface du rouleau 5, ou - according to a second variant illustrated in Figure 4, a base section S21 with a flat 22, the part intended to project out of the extrusion head 3 is provided with a flat 22 parallel to the surface of the roller 5, or
- selon une troisième variante illustrée sur la figure 5, une section de base S21 comprenant au moins deux lèvres 23, 24 parallèles qui viennent au contact du rouleau 5 selon des aires de contact axialement distinctes. - According to a third variant illustrated in Figure 5, a base section S21 comprising at least two parallel lips 23, 24 which come into contact with the roller 5 according to axially separate contact areas.
[0079] Une section de base S21 circulaire présentera l’avantage de procurer, en configuration de fermeture, une aire de contact entre le joint d’étanchéité 20 et le rouleau 5 qui s’étend en longueur en suivant la ligne de crête du cordon 21, portée par la direction circonférentielle, et qui est relativement étroite, ce qui permet de minimiser l’usure du joint d’étanchéité 20 et l’intensité du frottement exercé sur le rouleau 5. [0079] A circular base section S21 will have the advantage of providing, in the closed configuration, a contact area between the seal 20 and the roller 5 which extends in length following the crest line of the bead. 21, carried by the circumferential direction, and which is relatively narrow, which makes it possible to minimize the wear of the seal 20 and the intensity of the friction exerted on the roller 5.
[0080] Une section de base S21 à plusieurs lèvres 23, 24, ici deux lèvres, permettra de renforcer l’étanchéité en créant axialement une double barrière qui s’oppose aux fuites axiales des mélanges élastomériques, tout en conservant une aire de contact totale relativement restreinte entre le joint d’étanchéité 20 et le rouleau 5, puisque ladite aire de contact est limitée aux aires de contact quasi-linéaires selon lesquelles chacune des lèvres 23, 24, qui s’étend selon la direction circonférentielle, appuie sur le rouleau 5. [0080] A base section S21 with several lips 23, 24, here two lips, will make it possible to reinforce the seal by creating axially a double barrier which opposes axial leakage of the elastomeric compounds, while maintaining a total contact area. relatively restricted between the seal 20 and the roller 5, since said contact area is limited to the quasi-linear contact areas according to which each of the lips 23, 24, which extends in the circumferential direction, presses on the roller 5.
[0081] Une section de base S21 pourvue d’un méplat 22 permettra de créer une aire de contact plus large axialement que les deux variantes précédentes, ce qui permet de renforcer l’étanchéité en créant une barrière plus stable et plus résistante à la pression axiale qui est exercée par les mélanges élastomériques Ml, M2, M3, en concédant toutefois une intensité de frottement qui pourra être plus élevée que dans les deux cas précédents. [0081] A base section S21 provided with a flat 22 will make it possible to create a wider contact area axially than the two previous variants, which makes it possible to reinforce the seal by creating a more stable barrier and more resistant to pressure. axial which is exerted by the elastomeric mixtures M1, M2, M3, while conceding however an intensity of friction which may be higher than in the two preceding cases.
[0082] A titre indicatif, la largeur axiale W22 du méplat 22 pourra représenter entre 50% et 100% de la largeur axiale W21 du cordon 21 au repos. As an indication, the axial width W22 of the flat 22 may represent between 50% and 100% of the axial width W21 of the bead 21 at rest.
[0083] De préférence, la largeur axiale W22 du méplat 22 pourra être comprise entre 2,00 mm et 10,00 mm. Pour les valeurs de largeur axiale W22 les plus élevées, par exemple comprises entre 6 mm et 10 mm, on utilisera de préférence un cordon 21 réalisé dans un matériau souple, tel qu’un élastomère thermoplastique (ou « TPE »). Preferably, the axial width W22 of the flat 22 may be between 2.00 mm and 10.00 mm. For the highest W22 axial width values, for example between 6 mm and 10 mm, use will preferably be made of a cord 21 made of a flexible material, such as a thermoplastic elastomer (or “TPE”).
[0084] Quelle que soit la variante de section de base S21 considérée, la ligne génératrice centrale du cordon 21 cylindrique, c’est-à-dire la direction longitudinale du cordon 21, suivra de préférence, lorsque le cordon 21 est en place dans la tête d’extrusion 3, une direction circonférentielle, contenue dans un plan normal à l’axe central Y5, et donc parallèle à la direction d’écoulement L2, et ladite ligne génératrice présentera une courbure, considérée dans ledit plan normal à l’axe central Y5, qui est telle que ledit cordon 21 présente un profil incurvé qui épouse la courbure de la surface du rouleau 5. Whatever the base section variant S21 considered, the central generating line of the cylindrical bead 21, that is to say the longitudinal direction of the bead 21, will preferably follow, when the bead 21 is in place in the extrusion head 3, a circumferential direction, contained in a plane normal to the central axis Y5, and therefore parallel to the direction of flow L2, and said generating line will present a curvature, considered in said plane normal to the central axis Y5, which is such that said bead 21 has a curved profile which matches the curvature of the surface of roller 5.
[0085] De préférence, en configuration d’ouverture, le joint d’étanchéité 20 présente, à une hauteur de référence dite « hauteur de jauge » qui est égale à la hauteur maximale H6_max possible de l’entrefer 6, une ou des portions pleines qui occupent, de façon cumulée, une étendue axiale dite « largeur d’assise potentielle minimale » W20_pot qui est comprise entre 2 mm et 10 mm. Preferably, in the open configuration, the seal 20 has, at a reference height called "gauge height" which is equal to the maximum possible height H6_max of the air gap 6, one or more portions which occupy, cumulatively, an axial extent called “minimum potential seat width” W20_pot which is between 2 mm and 10 mm.
[0086] Cette largeur d’assise potentielle minimale W20_pot sera représentative de la largeur axiale minimale de l’aire de contact que l’on peut attendre, en configuration de fermeture, entre le joint d’étanchéité 20 et le rouleau 5, en section dans un plan radial contenant l’axe central Y5, lorsque l’extrémité radialement saillante du joint d’étanchéité 20 s’enfonce, sous l’effet de la compression radiale, d’une valeur égale à la valeur minimale d’interférence radiale H interf [0086] This minimum potential seat width W20_pot will be representative of the minimum axial width of the contact area that can be expected, in the closed configuration, between the seal 20 and the roller 5, in section in a radial plane containing the central axis Y5, when the radially projecting end of the seal 20 sinks, under the effect of the radial compression, by a value equal to the minimum radial interference value H interface
[0087] En pratique, si le passage en configuration de fermeture a pour effet de réduire la hauteur saillante du joint d’étanchéité 20 d’une valeur qui est égale à la valeur minimale d’interférence radiale H interf, ce qui correspond à une situation d’écrasement minimum dans laquelle la hauteur H6 effective de l’entrefer 6 vaut la hauteur maximale possible H6_max, alors la largeur axiale de l’aire de contact effective entre le joint d’étanchéité 20 et le rouleau 5 sera égale, ou quasi-égale, à la largeur d’assise potentielle minimale W20_pot. In practice, if switching to the closed configuration has the effect of reducing the projecting height of the seal 20 by a value which is equal to the minimum radial interference value H interf, which corresponds to a minimum crushing situation in which the effective height H6 of the air gap 6 is equal to the maximum possible height H6_max, then the axial width of the effective contact area between the seal 20 and the roller 5 will be equal, or almost -equal to the minimum potential seat width W20_pot.
[0088] Si, en revanche, le passage en configuration de fermeture a pour effet de réduire la hauteur saillante du joint d’une valeur qui est strictement supérieure à la valeur minimale d’interférence radiale H interf, ce qui correspond à une situation d’écrasement plus important dans laquelle la hauteur H6 effective de l’entrefer 6 est strictement inférieure à la hauteur maximale possible H6_max, et peut descendre jusqu’à la hauteur minimale possible H6_min, alors la largeur axiale de l’aire de contact effective entre le joint d’étanchéité 20 et le rouleau 5 sera strictement supérieure à la largeur d’assise potentielle minimale W20_pot, puisque la zone d’interférence atteint une portion pleine plus large du joint d’étanchéité 20. If, on the other hand, the passage in the closed configuration has the effect of reducing the protruding height of the joint by a value which is strictly greater than the minimum value of radial interference H interf, which corresponds to a situation of greater crushing in which the effective height H6 of the air gap 6 is strictly less than the maximum possible height H6_max, and can go down to the minimum possible height H6_min, then the axial width of the effective contact area between the seal 20 and the roller 5 will be strictly greater than the minimum potential seat width W20_pot, since the interference zone reaches a wider solid portion of the gasket 20.
[0089] Ainsi, en définitive, on est certain que la largeur axiale de l’aire de contact entre le joint d’étanchéité 20 et le rouleau 5 sera systématiquement au moins égale à la valeur de la largeur d’assise potentielle minimale W20_pot. Thus, ultimately, it is certain that the axial width of the contact area between the seal 20 and the roller 5 will systematically be at least equal to the value of the minimum potential seating width W20_pot.
[0090] Dans le cas d’une section de base S21 circulaire pleine, la largeur d’assise potentielle minimale W20_pot correspond, tel que cela est visible sur la figure 3, à la longueur de la corde d’arc qui s’étend entre les deux intersections de la circonférence de la section de base S21 circulaire avec une droite axiale dite « droite de jauge » L gauge située à une distance de la surface de la tête d’extrusion 3 qui est égale à la hauteur de jauge, c’est- à-dire à la hauteur maximale H6_max de l’entrefer. [0090] In the case of a solid circular base section S21, the minimum potential seat width W20_pot corresponds, as can be seen in FIG. 3, to the length of the bow chord which extends between the two intersections of the circumference of the circular base section S21 with an axial straight line called the "gauge straight line" L gauge located at a distance from the surface of the extrusion head 3 which is equal to the gauge height, it that is to say at the maximum height H6_max of the air gap.
[0091] Dans le cas d’une section de base S21 à plusieurs lèvres 23, 24, la largeur d’assise potentielle minimale W20_pot correspond à la somme des longueurs des différents segments définis respectivement par l’intersection de la droite de jauge L gauge avec chacune des lèvres 23, 24. In the case of a base section S21 with several lips 23, 24, the minimum potential seating width W20_pot corresponds to the sum of the lengths of the various segments defined respectively by the intersection of the gauge line L gauge with each of the lips 23, 24.
[0092] Selon une caractéristique préférentielle qui peut constituer une invention à part entière, le joint d’étanchéité 20, de préférence formé par un cordon 21, est inséré dans une rainure 25 radialement borgne qui est creusée à la surface de la tête d’extrusion 3, rainure 25 dont la largeur axiale W25 est strictement inférieure à la largeur axiale du joint d’étanchéité 20 avant insertion, ici la largeur axiale hors-tout W21 du cordon 21 au repos, de sorte que ladite rainure 25 assure le maintien axial dudit joint d’étanchéité 20 par pincement une fois ledit joint d’étanchéité 20 inséré dans la rainure 25. According to a preferred characteristic which may constitute an invention in its own right, the seal 20, preferably formed by a bead 21, is inserted into a radially blind groove 25 which is hollowed out on the surface of the head of extrusion 3, groove 25 whose axial width W25 is strictly less than the axial width of the seal 20 before insertion, here the overall axial width W21 of the bead 21 at rest, so that said groove 25 provides axial support said seal 20 by pinching once said seal 20 inserted into the groove 25.
[0093] En outre, ladite rainure 25 possède de préférence, à son extrémité aval 25_down considérée dans la direction d’écoulement L2 commune, un épaulement 26 contre lequel le joint d’étanchéité 20 vient en appui, de préférence par son extrémité aval 20_down, et qui forme ainsi une butée qui s’oppose au glissement circonférentiel dudit joint d’étanchéité 20 autour de l’axe central Y5 dans le sens amont-aval selon la direction d’écoulement commune L2. [0094] Ainsi, on peut avantageusement obtenir de façon simple et rapide un montage serré du joint d’étanchéité 20 dans la tête d’extrusion 3, montage qui assure notamment un maintien axial robuste du joint 20 des deux côtés dudit joint 20, c’est-à-dire par les deux bords latéraux dudit joint d’étanchéité 20. In addition, said groove 25 preferably has, at its downstream end 25_down considered in the common direction of flow L2, a shoulder 26 against which the seal 20 bears, preferably via its downstream end 20_down , and which thus forms a stop which opposes the circumferential sliding of said seal 20 around the central axis Y5 in the upstream-downstream direction along the common flow direction L2. [0094] Thus, one can advantageously obtain in a simple and fast way a tight mounting of the seal 20 in the extrusion head 3, assembly which ensures in particular a robust axial retention of the seal 20 on both sides of the said seal 20, c that is to say by the two side edges of said seal 20.
[0095] L’invention permet ainsi de gagner en temps et en simplicité de mise en œuvre aussi bien lorsque l’on met en place un joint d’étanchéité 20 neuf en insérant celui-ci dans la rainure 25 que lorsque l’on retire le joint d’étanchéité 20 usé en l’extrayant de la rainure 25. [0095] The invention thus makes it possible to save time and ease of implementation both when setting up a new seal 20 by inserting it into the groove 25 and when removing the worn seal 20 by extracting it from the groove 25.
[0096] On notera également que l’invention permet avantageusement de fixer le joint d’étanchéité 20 sur la tête d’extrusion 3 sans qu’il soit nécessaire de recourir à des pièces auxiliaires de fixation, en plus du joint d’étanchéité 20 lui-même et de la tête d’extrusion 3. En particulier, le système de fixation du joint 20 peut ainsi être avantageusement dépourvu de vis de fixation, de brides, de cales, etc. It will also be noted that the invention advantageously makes it possible to fix the seal 20 on the extrusion head 3 without it being necessary to resort to auxiliary fixing parts, in addition to the seal 20 itself and of the extrusion head 3. In particular, the gasket fixing system 20 can thus advantageously be devoid of fixing screws, flanges, wedges, etc.
[0097] De préférence, la profondeur radiale H25 de la rainure 25 est choisie de telle manière que, lorsque le joint d’étanchéité 20 est inséré en butée contre le fond radial 25_bottom de la rainure 25, et que l’installation 1 se trouve encore en configuration d’ouverture, avant le passage en configuration de fermeture, ledit joint d’étanchéité 20 fait saillie par rapport à la surface de la tête d’extrusion 23 de la valeur de saillie brute H20_pro souhaitée. Preferably, the radial depth H25 of the groove 25 is chosen in such a way that, when the seal 20 is inserted in abutment against the radial bottom 25_bottom of the groove 25, and the installation 1 is located still in the open configuration, before switching to the closed configuration, said seal 20 protrudes relative to the surface of the extrusion head 23 by the desired gross protrusion value H20_pro.
[0098] Ainsi, le positionnement correct du joint d’étanchéité 20 sera assuré automatiquement du simple fait du montage dudit joint 20. [0098] Thus, the correct positioning of the seal 20 will be ensured automatically simply by mounting said seal 20.
[0099] De façon particulièrement préférentielle, la profondeur radiale H25 de la rainure 25 sera choisie strictement inférieure à la dimension radiale que le joint d’étanchéité 20 présente au repos, avant insertion dudit joint d’étanchéité 20 dans la rainure 25, c’est-à-dire ici sera choisie inférieure à la hauteur radiale hors-tout H21 du cordon 21 considéré au repos, avant insertion. [0099] Particularly preferably, the radial depth H25 of the groove 25 will be chosen strictly less than the radial dimension that the seal 20 has at rest, before insertion of said seal 20 in the groove 25, it that is to say here will be chosen less than the overall radial height H21 of the cord 21 considered at rest, before insertion.
[00100] De préférence, la longueur de la rainure 25 couvrira la longueur mouillée L6 souhaitée, et de préférence sera égale à ladite longueur mouillée L6. [00100] Preferably, the length of the groove 25 will cover the desired wetted length L6, and preferably will be equal to said wetted length L6.
[00101] Par commodité de mise en œuvre et pour éviter toute discontinuité dans l’étanchéité, on choisira de préférence un cordon 21 dont la longueur L21 permet audit cordon 21 de remplir d’un seul tenant toute la longueur de ladite rainure 25, et dont toute la longueur mouillée L6. [00101] For convenience of implementation and to avoid any discontinuity in the seal, a bead 21 will preferably be chosen whose length L21 allows said cord 21 to fill in one piece the entire length of said groove 25, and including the entire wet length L6.
[00102] A titre d’exemple, on pourra mettre en œuvre un agencement présentant les dimensions suivantes : [00102] By way of example, it is possible to implement an arrangement having the following dimensions:
- un cordon 21 présentant, au repos, une hauteur radiale H21 comprise entre 2,80 et 2,85 mm, et une largeur axiale W21, de préférence égale à la hauteur radiale H21, comprise entre 2,80 mm et 2,85 mm, - a cord 21 having, at rest, a radial height H21 of between 2.80 and 2.85 mm, and an axial width W21, preferably equal to the radial height H21, of between 2.80 mm and 2.85 mm ,
- une rainure 25 présentant une profondeur radiale de 2,50 mm, et une largeur axiale W25, de préférence égale, ou inférieure, à la profondeur radiale H25, comprise entre 2,00 mm et 2,50 mm ; on notera à ce titre que, notamment sur les variantes des figures 4 et 5, il peut être intéressant d’avoir une largeur axiale W25 de rainure inférieure à la profondeur radiale H25 afin de diminuer l’effort de contact produit par la déformation du joint d’étanchéité 20,- A groove 25 having a radial depth of 2.50 mm, and an axial width W25, preferably equal to or less than the radial depth H25, between 2.00 mm and 2.50 mm; it will be noted in this respect that, in particular on the variants of Figures 4 and 5, it may be advantageous to have an axial width W25 of the groove less than the radial depth H25 in order to reduce the contact force produced by the deformation of the seal sealing 20,
- une hauteur nominale d’entrefer H6_set, c’est-à-dire un jeu fonctionnel entre la tête d’extrusion 3 et le rouleau 5, de l’ordre de 0,20 mm, - a nominal air gap height H6_set, i.e. a functional clearance between the extrusion head 3 and the roller 5, of the order of 0.20 mm,
- ce qui permettra en pratique d’obtenir, notamment en tenant compte du léger gonflement radial en hauteur du cordon 21 sous l’effet de la compression axiale qui se produit lors de l’insertion en force dudit cordon 21 dans la rainure 25, une hauteur d’interférence radiale H interf de l’ordre de 0,20 mm à 0,30 mm. - which will make it possible in practice to obtain, in particular taking into account the slight radial swelling in height of the bead 21 under the effect of the axial compression which occurs during the force insertion of the said bead 21 into the groove 25, a radial interference height H interf of the order of 0.20 mm to 0.30 mm.
[00103] De préférence, le joint d’étanchéité 20 pourra être formé d’un seul tenant dans un matériau élastomère thermoplastique (TPE), dont la dureté sera de préférence égale ou inférieure à 70 Shore A, notamment lorsque l’on recherche un joint d’étanchéité 20 souple, ou bien dans un poly-tetra-fluor-éthylène (PTFE) ou un polyamide (PA), dont la dureté sera de préférence égale ou inférieure à 70 shore D, notamment lorsque l’on recherche un joint d’étanchéité 20 plus dur. [00103] Preferably, the seal 20 may be formed in one piece from a thermoplastic elastomer (TPE) material, the hardness of which will preferably be equal to or less than 70 Shore A, in particular when a flexible seal 20, or else in a poly-tetra-fluor-ethylene (PTFE) or a polyamide (PA), the hardness of which will preferably be equal to or less than 70 shore D, in particular when a seal is sought sealing 20 harder.
[00104] On obtiendra dans tous les cas un bon compromis entre la raideur du joint d’étanchéité 20, qui permet à ce dernier de maintenir le contact avec le rouleau 5, et la flexibilité dudit joint d’étanchéité 20 qui permet à ce dernier d’épouser les courbures respectives de la tête d’extrusion 3 et du rouleau 5, ainsi que les variations locales de la hauteur H6 de l’entrefer le long de la longueur mouillée L6. A ce titre, on notera qu’un joint d’étanchéité 20 en matériau "dur" sera plus facilement sujet à une déformation plastique au moment de la fermeture, pour s’adapter à la forme de l’entrefer. On notera également que la composante élastique de la compression radiale du joint d’étanchéité 20 permettra utilement à ce dernier de s’adapter aux légères variations de la hauteur H6 de l’entrefer lors de la rotation du rouleau 5, du fait du battement radial dudit rouleau 5. In all cases, a good compromise will be obtained between the stiffness of the seal 20, which allows the latter to maintain contact with the roller 5, and the flexibility of the said seal 20, which allows the latter to match the respective curvatures of the extrusion head 3 and of the roller 5, as well as the local variations of the height H6 of the air gap along the wetted length L6. In this regard, it will be noted that a seal 20 made of "hard" material will be more easily subject to plastic deformation during time of closure, to adapt to the shape of the air gap. It will also be noted that the elastic component of the radial compression of the seal 20 will usefully allow the latter to adapt to the slight variations in the height H6 of the air gap during the rotation of the roller 5, due to the radial beat of said roll 5.
[00105] Le choix de matériau permettra en outre d’obtenir un faible coefficient de frottement du joint d’étanchéité 20 sur la surface métallique du rouleau 5. [00105] The choice of material will also make it possible to obtain a low coefficient of friction of the seal 20 on the metal surface of the roller 5.
[00106] En outre, un tel matériau sera bien adapté aux températures relativement élevées qui régnent dans l’entrefer 6 pendant l’opération de coextrusion. [00106] In addition, such a material will be well suited to the relatively high temperatures which prevail in the air gap 6 during the coextrusion operation.
[00107] Par ailleurs, l’invention porte bien entendu en tant que telle sur un procédé de fabrication d’un profilé 2, de préférence un profilé 2 destiné à entrer dans la composition d’un bandage pour roue de véhicule. [00107] Furthermore, the invention of course relates as such to a method of manufacturing a profile 2, preferably a profile 2 intended to enter into the composition of a tire for a vehicle wheel.
[00108] Le profilé 2 peut par exemple être destiné à former une bande de roulement du bandage, ou bien encore un élément de flanc du bandage. [00108] The profile 2 may for example be intended to form a tread of the tire, or even a sidewall element of the tire.
[00109] Le procédé selon l’invention comprend une étape (a) de préparation, au cours de laquelle on met en place un premier jeu de joints d’étanchéité 20 au sein d’une tête d’extrusion 3 d’une installation 1 d’extrusion telle que décrite dans ce qui précède, afin de délimiter les deux lisières latérales de l’entrefer 6, puis une étape (b) de réalisation d’un premier tirage au cours de laquelle on place ladite installation 1 en configuration de fermeture, et l’on alimente la tête d’extrusion 3 au moyen d’une pluralité d’extrudeuses connectées chacune à l’une des voies de ladite tête d’extrusion 3 et acheminant chacune un mélange élastomérique Ml, M2, M3, de sorte à réaliser un premier profilé 2, puis on stoppe le tirage et l’on replace l’installation 1 en configuration d’ouverture, puis une étape (c) de remplacement des joints d’étanchéité 20 au cours de laquelle on retire le premier jeu de joints d’étanchéité 20 usagés et on le remplace par un second jeu de joints d’étanchéité 20 neufs, puis une étape (d) de réalisation d’un second tirage, au cours de laquelle on replace l’installation 1, pourvue de son second jeu de joints d’étanchéité 20 neufs, en configuration de fermeture et l’on réalise un second profilé 2. The method according to the invention comprises a step (a) of preparation, during which a first set of seals 20 is placed within an extrusion head 3 of an installation 1 extrusion as described in the foregoing, in order to delimit the two lateral edges of the air gap 6, then a step (b) of producing a first draw during which said installation 1 is placed in the closed configuration , and the extrusion head 3 is fed by means of a plurality of extruders each connected to one of the paths of said extrusion head 3 and each conveying an elastomeric mixture M1, M2, M3, so to produce a first profile 2, then the drawing is stopped and the installation 1 is replaced in the open configuration, then a step (c) of replacing the seals 20 during which the first set is removed of used seals 20 and it is replaced by a second set of new seals 20, then a step (d) of carrying out a second draw, during which the installation 1, provided with its second set of new seals 20, in the closed configuration and a second profile 2 is produced.
[00110] De préférence, l’étape (c) de remplacement des joints d’étanchéité au sein d’une même tête d’extrusion 3 est mise en œuvre systématiquement avec une périodicité inférieure ou égale à trois tirages consécutifs, c’est-à-dire une fois toutes les une, deux ou trois mises en configuration de fermeture de l’installation 1, et plus préférentiellement avec une périodicité égale à un et un seul tirage, c’est-à-dire à chaque nouvelle mise en configuration d’ouverture de l’installation 1, équipée de ladite tête d’extrusion 3, qui suit une étape (b) de réalisation d’un tirage utilisant ladite tête d’extrusion 3 et qui précède une nouvelle étape (d) de réalisation d’un tirage impliquant cette même tête d’extrusion 3. [00110] Preferably, step (c) of replacing the seals within the same extrusion head 3 is implemented systematically with a lower periodicity or equal to three consecutive draws, that is to say once every one, two or three settings in the closing configuration of the installation 1, and more preferably with a periodicity equal to one and only one draw, it that is to say each time the installation 1 is put into the open configuration, equipped with said extrusion head 3, which follows a step (b) of producing a print using said extrusion head 3 and which precedes a new step (d) of producing a print involving this same extrusion head 3.
[00111] En d’autres termes, on pourra remplacer les joints d’étanchéité 20 fréquemment, et plus préférentiellement après chaque utilisation, à chaque nouveau cycle d’ouverture/fermeture de l’installation 1. [00111] In other words, the seals 20 can be replaced frequently, and more preferably after each use, at each new opening/closing cycle of the installation 1.
[00112] Les joints d’étanchéité 20, particulièrement faciles et peu onéreux à remplacer, seront donc de préférence « jetables », c’est-à-dire à usage unique, ce qui garantira une étanchéité fiable à chaque nouveau tirage. [00112] The seals 20, which are particularly easy and inexpensive to replace, will therefore preferably be "disposable", that is to say for single use, which will guarantee a reliable seal with each new draw.
[00113] S’ il est prévu de réutiliser le joint d’étanchéité 20 pour plus d’un tirage, on procédera toutefois à son inspection avant réutilisation, et on le remplacera si l’on constate une dégradation dudit joint d’étanchéité 20 qui serait susceptible de nuire à sa fonction d’étanchéité, par exemple une usure excessive ou la présence d’un résidu collant de mélange élastomérique extrudé. [00113] If it is planned to reuse the seal 20 for more than one draw, it will however be inspected before reuse, and it will be replaced if there is a degradation of said seal 20 which would be likely to impair its sealing function, for example excessive wear or the presence of a sticky residue of extruded elastomeric compound.
[00114] Avantageusement, l’invention permettra, malgré ces changements fréquents voire systématiques des joints d’étanchéité 20, de conserver le système de fermeture 10 inchangé entre les tirages consécutifs, sans qu’il soit nécessaire d’effectuer ou de modifier un quelconque réglage dudit système de fermeture 10, notamment un quelconque réglage de jeu ou de positionnement de la butée 14, ni d’opérer une quelconque modification de la tête d’extrusion 3, après chaque changement des joints d’étanchéité 20. [00114] Advantageously, the invention will make it possible, despite these frequent or even systematic changes of the seals 20, to keep the closure system 10 unchanged between consecutive draws, without it being necessary to carry out or modify any adjustment of said closure system 10, in particular any adjustment of play or positioning of abutment 14, nor to operate any modification of extrusion head 3, after each change of seals 20.
[00115] Bien entendu, l’invention n’est nullement limitée aux seules variantes décrites dans ce qui précède, l’homme du métier étant notamment à même d’isoler ou de combiner librement entre elles l’une ou l’autre des caractéristiques susmentionnées, ou de leur substituer des équivalents. [00115] Of course, the invention is in no way limited to the variants described above, the person skilled in the art being in particular able to isolate or freely combine one or the other of the characteristics above, or to substitute equivalents for them.

Claims

- 22 - REVENDICATIONS - 22 - CLAIMS
1. Installation (1) de coextrusion destinée à générer un profilé (2) en extradant conjointement une pluralité de mélanges élastomériques (Ml, M2, M3) selon une direction d’écoulement commune (L2), ladite installation comprenant une tête d’extrusion (3) destinée à amener les mélanges élastomériques, un rouleau (5) qui est entraîné en rotation sur lui- même autour d’un axe central (Y5), et un système de fermeture (10) conçu pour faire passer alternativement l’installation (1) d’une configuration d’ouverture, dans laquelle la tête d’extrusion (3) est éloignée du rouleau (5), à une configuration de fermeture, dans laquelle la tête d’extrusion (3) est rapprochée du rouleau (5) afin de définir avec ledit rouleau un entrefer (6) servant à conformer la section du profilé (2), lequel entrefer (6) s’étend selon une première dimension dite « hauteur » (H6) portée par une direction radiale (DR) perpendiculaire à l’axe central (Y5), selon une seconde dimension dite « largeur » (W6) portée par une direction axiale (DA) parallèle à l’axe central (Y5), et selon une troisième dimension dite « longueur mouillée » (L6) qui est portée par la direction d’écoulement commune (L2) et qui représente une portion de la circonférence du rouleau (5), ladite installation étant caractérisée en ce que le système de fermeture (10) comporte un mécanisme (13) à butée (14) qui est agencé pour positionner de manière reproductible la tête d’extrusion (3) par rapport au rouleau (5) en configuration de fermeture afin de garantir que, dans ladite configuration de fermeture, la hauteur de l’entrefer (H6) est égale à une hauteur nominale (H6_set) prédéterminée, assortie d’une tolérance radiale (IT6) connue, et en ce que ladite installation (1) comprend au moins un joint d’étanchéité (20), destiné à venir délimiter la largeur (W6) de l’entrefer afin d’empêcher les mélanges élastomériques (Ml, M2, M3) de fuir axialement hors de l’entrefer (6), ledit joint d’étanchéité (20) étant fixé à la tête d’extrusion de sorte d’une part à pouvoir couvrir la longueur mouillée (L6) dans la configuration de fermeture, et d’autre part à faire saillie radialement par rapport à la tête d’extrusion (3), d’une valeur qui, lorsque la tête d’extrusion (3) est en configuration d’ouverture, est dite « hauteur de saillie brute » (H20_pro) et est strictement supérieure, d’une valeur non nulle dite « valeur minimale d’interférence radiale » (H interf), à la hauteur maximale (H6_max) possible de l’entrefer (6) qui est attendue en configuration de fermeture en tenant compte de la hauteur nominale (H6_set) de l’entrefer et de la tolérance radiale (IT6) connue, de sorte que, lorsque le système de fermeture (10) fait passer l’installation (1) en configuration de fermeture, la tête d’extrusion (3) force l’écrasement radial du joint d’étanchéité (20) en compression contre le rouleau (5), d’une valeur de compression radiale qui est au moins égale à la valeur minimale d’interférence radiale (H interf). 1. Coextrusion installation (1) intended to generate a profile (2) by jointly extraditing a plurality of elastomeric mixtures (M1, M2, M3) along a common flow direction (L2), said installation comprising an extrusion head (3) intended to bring the elastomeric mixtures, a roller (5) which is driven in rotation on itself around a central axis (Y5), and a closure system (10) designed to alternately pass the installation (1) from an open configuration, in which the extrusion head (3) is moved away from the roller (5), to a closed configuration, in which the extrusion head (3) is brought closer to the roller ( 5) in order to define with said roller an air gap (6) serving to conform the section of the profile (2), which air gap (6) extends along a first dimension called "height" (H6) carried by a radial direction (DR ) perpendicular to the central axis (Y5), along a second dimension called "width" (W6) carried by an axial direction (DA) parallel to the central axis (Y5), and along a third dimension called "wet length" (L6) which is carried by the common direction of flow (L2) and which represents a portion of the circumference of the roller (5), said installation being characterized in that the closing system (10) comprises a mechanism (13) with abutment (14) which is arranged to position the extrusion head (3) in a reproducible manner with respect to the roller (5) in the closed configuration in order to guarantee that, in said closed configuration, the height of the air gap ( H6) is equal to a predetermined nominal height (H6_set), together with a known radial tolerance (IT6), and in that said installation (1) comprises at least one seal (20), intended to delimit the width (W6) of the gap in order to prevent the elastomeric compounds (M1, M2, M3) from leaking axially out of the gap (6), said seal (20) being fixed to the extrusion head so as on the one hand to be able to cover the wetted length (L6) in the closed configuration, and on the other hand to protrude radially with respect to the extrusion head (3), by a value which, when the extrusion head (3) is in the open configuration, is called "gross projection height" (H20_pro) and is strictly greater, by a non-zero value called "minimum radial interference value" (H interf), at the maximum possible height (H6_max) of the air gap (6) which is expected in the closed configuration taking into account the nominal height (H6_set) of the air gap and the radial tolerance (IT6) known, so that when the closure system (10) passes the installation (1) in the closed configuration, the extrusion head (3) forces the radial crushing of the seal (20 ) in compression against the roller (5), with a radial compression value which is at least equal to the minimum radial interference value (H interf).
2. Installation selon la revendication 1 caractérisée en ce que la valeur d’interférence radiale minimale (H interf) est comprise entre 0,05 mm et 1,00 mm. 2. Installation according to claim 1 characterized in that the minimum radial interference value (H interf) is between 0.05 mm and 1.00 mm.
3. Installation selon l’une des revendications 1 ou 2 caractérisée en ce que le joint d’étanchéité (20) est formé par un cordon (21) qui présente au repos, avant mise en place sur la tête d’extrusion (3), une longueur (L21), de préférence comprise entre 30 mm et 200 mm, qui est strictement supérieure, de préférence au moins 10 fois supérieure, et plus préférentiellement au moins 50 fois supérieure, voire au moins 100 fois supérieure, à la largeur axiale hors-tout (W21) dudit cordon au repos. 3. Installation according to one of claims 1 or 2 characterized in that the seal (20) is formed by a bead (21) which has at rest, before placing on the extrusion head (3) , a length (L21), preferably between 30 mm and 200 mm, which is strictly greater, preferably at least 10 times greater, and more preferably at least 50 times greater, or even at least 100 times greater, than the axial width overall (W21) of said cord at rest.
4. Installation selon la revendication 3 caractérisée en ce que le cordon (21) présente une forme cylindrique dont la section de base (S21) est choisie parmi : une section de base (S21) circulaire, une section de base (S21) à méplat (22) dont la partie destinée à faire saillie hors de la tête d’extrusion est pourvue d’un méplat (22) parallèle à la surface du rouleau (5), ou une section de base (S21) comprenant au moins deux lèvres (23, 24) parallèles venant au contact du rouleau (5) selon des aires de contact axialement distinctes. 4. Installation according to claim 3 characterized in that the cord (21) has a cylindrical shape whose base section (S21) is chosen from: a base section (S21) circular, a base section (S21) flat (22) whose part intended to protrude from the extrusion head is provided with a flat (22) parallel to the surface of the roller (5), or a base section (S21) comprising at least two lips ( 23, 24) parallel coming into contact with the roller (5) according to axially distinct contact areas.
5. Installation selon l’une des revendications précédentes caractérisée en ce que, en configuration d’ouverture, le joint d’étanchéité (20) présente, à une hauteur de référence dite « hauteur de jauge » qui est égale à la hauteur maximale (H6_max) possible de l’entrefer (6), une ou des portions pleines qui occupent, de façon cumulée, une étendue axiale dite « largeur d’assise potentielle minimale » (W20_pot) qui est comprise entre 2 mm et 10 mm. 5. Installation according to one of the preceding claims characterized in that, in the open configuration, the seal (20) has, at a reference height called "gauge height" which is equal to the maximum height ( H6_max) possible of the air gap (6), one or more solid portions which occupy, cumulatively, an axial extent called “minimum potential seating width” (W20_pot) which is between 2 mm and 10 mm.
6. Installation selon l’une des revendications précédentes caractérisée en ce que le joint d’étanchéité (20), de préférence formé par un cordon (21), est inséré dans une rainure (25) radialement borgne qui est creusée à la surface de la tête d’extrusion (3), rainure (25) dont la largeur axiale (W25) est strictement inférieure à la largeur axiale (W21) du joint d’étanchéité (20) avant insertion, de sorte que ladite rainure (25) assure le maintien axial dudit joint d’étanchéité (20) par pincement une fois ledit joint d’étanchéité (20) inséré dans la rainure (25), et en ce que la rainure (25) possède, à son extrémité aval (25_down) considérée dans la direction d’écoulement (L2) commune, un épaulement (26) contre lequel le joint d’étanchéité (20) vient en appui, de préférence par son extrémité aval (20_down), et qui forme ainsi une butée qui s’oppose au glissement circonférentiel dudit joint d’étanchéité (20) autour de l’axe central (Y5) dans le sens amont-aval selon la direction d’écoulement commune (L2). 6. Installation according to one of the preceding claims, characterized in that the seal (20), preferably formed by a bead (21), is inserted into a radially blind groove (25) which is hollowed out at the surface of the extrusion head (3), groove (25) whose axial width (W25) is strictly less than the axial width (W21) of the seal (20) before insertion, so that said groove (25) ensures the axial holding of said seal (20) by pinching once said seal (20) has been inserted into the groove (25), and in that the groove (25) has, at its downstream end (25_down) considered in the common flow direction (L2), a shoulder (26) against which the seal (20) comes into abutment, preferably by its downstream end (20_down), and which thus forms an abutment which opposes the circumferential sliding of said seal (20) around the central axis ( Y5) in the upstream-downstream direction along the common flow direction (L2).
7. Installation selon l’une des revendications précédentes caractérisée en ce que le joint d’étanchéité (20) est formé d’un seul tenant dans un matériau élastomère thermoplastique (TPE), dont la dureté sera de préférence égale ou inférieure à 70 Shore A, ou bien dans un poly-tetra-fluor-éthylène (PTFE) ou un polyamide (PA), dont la dureté sera de préférence égale ou inférieure à 70 shore D. 7. Installation according to one of the preceding claims, characterized in that the seal (20) is formed in one piece from a thermoplastic elastomer (TPE) material, the hardness of which will preferably be equal to or less than 70 Shore. A, or in a poly-tetra-fluor-ethylene (PTFE) or a polyamide (PA), the hardness of which will preferably be equal to or less than 70 shore D.
8. Installation selon l’une des revendications précédentes caractérisée en ce que la hauteur nominale (H6_set) de l’entrefer destinée à être comblée par le joint d’étanchéité (20) est comprise entre 0,10 mm et 0,50 mm. 8. Installation according to one of the preceding claims, characterized in that the nominal height (H6_set) of the air gap intended to be filled by the seal (20) is between 0.10 mm and 0.50 mm.
9. Procédé de fabrication d’un profilé (2), de préférence un profilé destiné à entrer dans la composition d’un bandage pour roue de véhicule, ledit procédé comprenant une étape (a) de préparation, au cours de laquelle on met en place un premier jeu de joints d’étanchéité (20) au sein d’une tête d’extrusion (3) d’une installation (1) d’extrusion selon l’une des revendications précédentes, afin de délimiter les deux lisières latérales de l’entrefer (6), puis une étape (b) de réalisation d’un premier tirage au cours de laquelle on place ladite installation (1) en configuration de fermeture, et l’on alimente la tête d’extrusion (3) au moyen d’une pluralité d’extrudeuses connectées chacune à l’une des voies de ladite tête d’extrusion et acheminant chacune un mélange élastomérique (Ml, M2, M3), de sorte à réaliser un premier profilé (2), puis on stoppe le tirage et l’on replace l’installation (1) en configuration d’ouverture, puis une étape (c) de remplacement des joints d’étanchéité au cours de laquelle on retire le premier jeu de joints d’étanchéité (20) usagés et on le remplace par un second jeu de joints d’étanchéité (20) neufs, puis une étape (d) de réalisation d’un second tirage, au cours de laquelle on replace l’installation (1), pourvue de son second jeu de joints d’étanchéité (20) neufs, en configuration de fermeture et l’on réalise un second profilé (2). 9. A method of manufacturing a profile (2), preferably a profile intended to enter into the composition of a tire for a vehicle wheel, said method comprising a step (a) of preparation, during which places a first set of seals (20) within an extrusion head (3) of an extrusion installation (1) according to one of the preceding claims, in order to delimit the two lateral edges of the air gap (6), then a step (b) of performing a first draw during which said installation (1) is placed in the closed configuration, and the extrusion head (3) is fed to the means of a plurality of extruders each connected to one of the tracks of said extrusion head and each conveying an elastomeric mixture (M1, M2, M3), so as to produce a first profile (2), then stopping pulling and replacing the installation (1) in the open configuration, then a step (c) of replacing the seals during which the first set of used seals (20) is removed and it is replaced by a second set of new seals (20), then a step (d) of carrying out a second draw, during which the installation (1) is replaced, provided with its second set seals (20) new, in the closed configuration and a second section (2) is produced.
10. Procédé selon la revendication 9 caractérisé en ce que l’étape (c) de remplacement des joints d’étanchéité (20) au sein d’une même tête d’extrusion (3) est mise en œuvre systématiquement avec une périodicité inférieure ou égale à trois tirages consécutifs, et plus - 25 - préférentiellement avec une périodicité égale à un et un seul tirage c’est-à-dire à chaque mise en configuration d’ouverture de l’installation (1) équipée de ladite tête d’extrusion (3) qui suit une étape (b) de réalisation d’un tirage utilisant ladite tête d’extrusion (3) et qui précède une nouvelle étape (d) de réalisation d’un tirage impliquant cette même tête d’extrusion (3). 10. Method according to claim 9, characterized in that step (c) of replacing the seals (20) within the same extrusion head (3) is implemented systematically with a lower periodicity or equal to three consecutive draws, and more - 25 - preferably with a periodicity equal to one and only one draw, that is to say each time the installation (1) equipped with said extrusion head (3) is put into the opening configuration which follows a step (b) producing a print using said extrusion head (3) and which precedes a new step (d) producing a print involving this same extrusion head (3).
PCT/FR2022/052015 2021-10-26 2022-10-25 Coextrusion installation comprising sealing beads which are squeezed against the roller during the closure of the extrusion head WO2023073315A1 (en)

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Application Number Priority Date Filing Date Title
FR2111340A FR3128395B1 (en) 2021-10-26 2021-10-26 COEXTRUSION PLANT INCLUDING SEALING CORDS THAT ARE CRUSHED AGAINST THE ROLLER WHEN CLOSING THE EXTRUSION HEAD
FRFR2111340 2021-10-26

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WO2023073315A1 true WO2023073315A1 (en) 2023-05-04

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1523830A (en) * 1966-05-23 1968-05-03 Du Pont A method and apparatus for the continuous molding of a thermoplastic resin into a continuous sheet, and articles obtained by this method
US4539169A (en) * 1983-07-29 1985-09-03 The Goodyear Tire & Rubber Company Apparatus and method for forming a co-extrusion from extruded strips
EP0201337A2 (en) 1985-05-08 1986-11-12 The Uniroyal Goodrich Tire Company Early progressive junction extrusion system
FR2700291A1 (en) * 1993-01-08 1994-07-13 Michelin & Cie Extrusion apparatus and extrusion method for raw rubber mixtures.
US6474966B1 (en) * 1998-05-19 2002-11-05 Berstorff Gmbh Slot die for producing webs of a foamed plastic material
US20040009255A1 (en) * 2000-11-27 2004-01-15 Philippe Lamoine Extrusion device for manufacturing a product based on a rubber mix
FR3068281A1 (en) * 2017-06-30 2019-01-04 Compagnie Generale Des Etablissements Michelin METHOD FOR EXTRUSION OF A COMPLEX PROFILE COMPRISING A GUM OF EDGE IN THE BACK OF SILLON

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1523830A (en) * 1966-05-23 1968-05-03 Du Pont A method and apparatus for the continuous molding of a thermoplastic resin into a continuous sheet, and articles obtained by this method
US4539169A (en) * 1983-07-29 1985-09-03 The Goodyear Tire & Rubber Company Apparatus and method for forming a co-extrusion from extruded strips
EP0201337A2 (en) 1985-05-08 1986-11-12 The Uniroyal Goodrich Tire Company Early progressive junction extrusion system
FR2700291A1 (en) * 1993-01-08 1994-07-13 Michelin & Cie Extrusion apparatus and extrusion method for raw rubber mixtures.
US6474966B1 (en) * 1998-05-19 2002-11-05 Berstorff Gmbh Slot die for producing webs of a foamed plastic material
US20040009255A1 (en) * 2000-11-27 2004-01-15 Philippe Lamoine Extrusion device for manufacturing a product based on a rubber mix
FR3068281A1 (en) * 2017-06-30 2019-01-04 Compagnie Generale Des Etablissements Michelin METHOD FOR EXTRUSION OF A COMPLEX PROFILE COMPRISING A GUM OF EDGE IN THE BACK OF SILLON

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FR3128395A1 (en) 2023-04-28

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