WO2019234577A1

WO2019234577A1 - Compact apparatus for welding strips wound onto a support ring

Info

Publication number: WO2019234577A1
Application number: PCT/IB2019/054566
Authority: WO
Inventors: Gian Piero Barozzi
Original assignee: GSKET S.r.l.
Priority date: 2018-06-04
Filing date: 2019-06-03
Publication date: 2019-12-12

Abstract

Welding apparatus for machines for producing seals comprising two strips (1), a first strip (la) of which has superior mechanical characteristics and a second strip (lb) of which has superior sealing characteristics, said seals being wound by means of a winding assembly (100) rotating about a longitudinal axis (X-X) of rotation; the apparatus comprising: a pressing assembly (200) arranged to operate on the seal being wound; a welding assembly (300) for welding the first strip (la) being wound, comprising two electrodes (305a,305b); the pressing assembly (200) has a support (202) to which there is fastened a hub (302) rotating about an axis parallel to a longitudinal direction (X-X) during use parallel to the axis of rotation of the winding assembly and arranged aligned with the pressing wheel (201) in the transverse direction (Y-Y), said hub having an extension (302b) towards the outside in the transverse direction (Y-Y) carrying the welding assembly (300), the rotation of the hub being designed to move the welding assembly from a position disengaged from the seal being machined into a position in contact therewith so as to weld the first strip (la) and vice versa, upon operation of drive means (309); the position of the said pressing assembly can be adjusted in the vertical direction (Z-Z), the adjustment of the pressing assembly causing the automatic positioning of the welding assembly depending on the desired diameter of the seal being wound.

Description

COMPACT APPARATUS FOR WELDING STRIPS WOUND ONTO A

SUPPORT RING

- o -

The present invention relates to an apparatus for welding strips wound onto a support ring.

In the art numerous types of sealing gaskets or seals in the form of rings and designed to perform the static frontal sealing, for example of pipe connections, are known.

It is also known that for the industrial production of these types of seals it is necessary to wind in a spiral two strips which are superimposed on each other and have physical and mechanical characteristics which are very different from each other, winding in particular a first strip with a high mechanical strength, for example made of steel, which forms the support for the second strip made of a material having superior insulating characteristics, but a lower tensile strength, such as graphite.

Also known are machines which perform the construction of said seals either by means of a semi-manual operation, which requires constant monitoring and auxiliary action on the part of an operator fully dedicated to the machine, or semi- automatically as illustrated in EP 707 906, which describes an automatic machine for the production of gaskets obtained by means of the spiral winding of strips with different physical and mechanical characteristics onto a support ring, which machine comprises: means for feeding said support rings to a mandrel, means for feeding the strips to be wound to the support ring; a unit for applying radial pressure onto said rings; and a unit for welding one of said strips for initial winding and for closing the gasket once winding has been completed. Although performing their intended function, the known machines, however, have a number of drawbacks due to the fact that, at the moment of cutting of the steel strip once winding has been completed, they do not have means for retaining the strip, in the direction perpendicular to its axis of rotation, resulting in a misalignment of the steel strip when it is located opposite the welding discs, which misalignment may also cause defects in the final welds, said defects being worsened by the fact that the weld is performed by an associated welding assembly in a position which is remote from the position of the pressing and guiding assembly in the radial and axial direction of the spiral, along the circumference thereof.

Also known from US 9, 346, 133, in the name of the same present Applicant, is an apparatus for welding wound gaskets, which has the sealing unit coaxially inserted inside the pressing unit; although solving some of the problems mentioned above, the apparatus however cannot be used for applying high pressures which are needed to ensure very compact winding, as is at present required by the market, since the welding and pressing electrode is made of copper and cannot withstand the high stresses which are applied by the pressing and guiding disc which must be made of tempered steel.

A further welding apparatus according to the preamble of Claim 1 is also known from EP 0,707,906 in the name of the same present Applicant.

The technical problem which is posed therefore is that of providing an apparatus which provides a solution to the aforementioned problems of the prior art, allowing the machining of wound seals both with small diameters and with very large diameters without the need for special adjustments and/or complicated format-changing operations.

In connection with this problem it is also required that this apparatus should have small dimensions, suitable for reducing the overall dimensions of the machines to which it must be applied, being easy and inexpensive to produce and assemble, and be able to be easily installed also on machines which are already in production.

Furthermore it is preferable to be able to adjust the positioning of the welding means relative to the strip being wound.

These results are obtained according to the present invention by an apparatus for welding strips with different characteristics which are wound onto a support ring according to the characteristic features of Claim 1.

Further details may be obtained from the following description of a non-limiting example of embodiment of the subject of the present invention provided with reference to the attached drawings in which: Figure 1 : shows a front perspective view of a first embodiment of the welding apparatus according to the present invention;

Figure 2 : shows a front view of the welding apparatus according to Fig. 1 with the welding assembly in a position disengaged from the seal; Figure 3: shows a schematic cross-section along the plane indicated by III-III in Fig. 2;

Figure 4 : shows a partially sectioned perspective side view of the pressing and welding assembly;

Figure 5: shows a partial perspective view of the means for locking the pressing assembly to the machine structure; Figure 6: shows a front view of the welding apparatus with welding assembly in the engaged position for initial welding of the steel ring; and Figures 7a-7b: show a detailed view of the different positions of the welding assembly and the pressing assembly depending on the different diameters of the seal.

As shown, solely for the purposes of easier description and without a limiting meaning, a set of three reference axes is assumed, these axes being situated, respectively, in a longitudinal direction X-X corresponding to the rotation axis of the seal winding means; in a transverse direction Y-Y corresponding to the direction of feeding of the strip to be wound; and in a vertical direction Z-Z perpendicular to the other two directions and corresponding to the direction of movement in the vertical direction of parts of the apparatus according to the present invention.

With reference to Fig. 1, a winding machine which includes an apparatus according to the invention comprises essentially:

- a winding assembly 100 for winding the strips 1, in particular a strip la of material, such as steel, with superior mechanical characteristics, and a strip lb with superior sealing characteristics, such as graphite, which are supplied by feeders which are conventional per se and not shown or described in detail and are fed to the apparatus in the transverse direction Y-Y; the assembly 100 comprises a mandrel 110 rotating about the longitudinal axis X-X and carrying the winding disc 108 or an inner ring; in the first case the disc 108 has a radial incision 108a for inserting the free end of the steel strip to be wound, and in the second case the steel strip is welded directly onto the inner ring; whereas the winding disc is separated from the seal at the end of winding, the inner ring is not separated from the seal, remaining incorporated therein.

In both cases, the graphite strip is arranged in between on the steel strip and is conveyed along being wound by it.

The winding assembly 100 is fixed and mounted on a support structure of the machine (not shown) .

a welding assembly according to the invention which comprises:

- a pressing assembly 200 comprising: a disc 201, arranged underneath the winding disc 108 and mounted on a corresponding support 202 (Fig. 3) having a U-shaped form and guided on a ball-mounted sliding block 203 (Fig. 5) sliding on corresponding fixed guide elements integral with the machine frame; the pressing assembly 200 is movable in both senses of the vertical direction Z-Z upon operation of associated actuating means preferably comprising a cylinder 210, which is fastened by means of a sliding block 212, and locking means, preferably of the clamp type 213, to elements situated outside the apparatus and fixed to the machine structure, and the rod of which is connected to the support 202.

The rod of the cylinder may be moved towards/away from the mandrel 110 so as to cause compression of the seal during initial winding and instead release it in the opposite direction, when there is an increase in the diameter of the seal during winding .

A locking system, for example of the clamp type 213,213a (Fig. 5,6), allows the cylinder 210 to be locked at a given distance depending on the size of the seal to be wound.

The disc 201 comprises two flanges 205a, 205b (Fig. 3) which are situated opposite each other in the longitudinal direction X-X and arranged so as to leave an interspace suitable for containing the thickness of the seal being wound; the flanges are mounted on a body 206 which is fixed to the support 202 and relative to which the disc may be displaced in both senses of the longitudinal direction X-X by screw means 205 so as to adjust the position of the disc in the longitudinal direction and therefore centring of the seal during winding;

- a welding assembly 300 movable rotationally about an axis parallel to the longitudinal axis X-X between a disengaged position removed from the pressing assembly and a position close to the pressing assembly for contact with the seal being wound and vice versa.

In detail the welding assembly 300 comprises:

a hub 302 (Fig. 3) rotating on bearings 302a mounted on a shaft 303 extending parallel to the longitudinal direction X-X inside the support 202;

- the hub 302 has an extension 302b (Fig. 2) which extends outwards perpendicularly with respect to the axis of the hub and which has, fixed thereto, two lateral and substantially parallel bars 306a, 306b extending in a direction substantially perpendicular to the said extension 302b.

The top free end of each bar 306a, 306b (Figs. 1,4) has, fixed thereto, in an insulated manner, a respective conducting plate 307a, 307b which carries at a first end the cables 315 for supplying the electric current (Fig. 1) and at the other end welding wheels 305a, 305b (Fig. 4) which are pivotably mounted on the said plates and relative to which they may rotate and from which they receive the electric current.

Advantageously, a spring 310 (Fig. 4) extending parallel to the longitudinal direction X-X is arranged between the two welding wheels 305a, 305b so as to keep them always separated from each other .

The bars 306a, 306b and therefore also the plates 307a, 307b (Fig. 4) are kept spaced from each other by a compression spring 308 coaxially mounted on an adjusting screw 308a passing through the said bars 306a, 306b .

Said adjusting screw 308a is moved by a graduated knob 308b and is designed to adjust the distance between the two wheels 305 (electrodes) so as to adapt them to the different profiles of the steel strip 1.

The plates 307a, 307b, which are moved away from each other or closer together by the action of the adjusting screw 308a, move also the welding wheels 305a, 305b which remain always axially in contact with said plates owing to the action of the spring 310, but are always insulated owing to an insulating material which is arranged in between and is designed to prevent current flowing from one wheel to the other.

The shaft 303 supporting the hub 302 has (Fig. 3) a threaded end 303a which can be coupled to a graduated knob 304, rotation of which allows the displacement of the hub 302 in both senses of the longitudinal direction X-X, correspondingly varying the position of the arms 306a, 306b, which are integral with the hub, and therefore of the plates 307a, 307b, allowing micrometric adjustment in the longitudinal direction of the centring of the welding wheels 305a, 305b relative to the seal.

With the configuration described above the machine may be used in the modes described below suitable for two main production processes:

A) Construction of a seal on a winding support disc which defines the internal diameter of the said seal;

B) Construction of a seal directly on an inner ring, i.e. a ring which remains incorporated in the seal which is formed.

In both cases initially the heightwise position of the pressing assembly 200 is adjusted by means of the cylinder 210 which is moved by a knob 211; when the predefined position is reached, the cylinder is locked in position by means of the clamp 213, leaving a suitable space (e.g. about 50 mm), depending on the diameter of the seal to be wound, between the pressing wheel and the winding disc ( Fig .6 ) .

The clamp 213 locks the support of the cylinder

210, operation of which actuates the associated rod which displaces the support 202 towards the winding mandrel so as to compress the seal during winding. This operation is the same for both the modes A and/or B, the initial sequence of which varies in each case.

CASE A - WINDING DISC

The free end of the steel strip la is inserted inside the corresponding incision 108a formed in the winding disc 108 (Fig. 1), the pressing assembly 200 (Fig. 2) is raised by means of the cylinder 210 until it stops against the disc 108 and the automatic cycle is started;

the winding assembly 100 (Fig.7a) rotates by an amount such as to bring the strip la into the welding position, performing a complete rotation plus a further small partial rotation so as to bring two steel layers opposite the welding wheels for welding together thereof.

The cylinder 309 is activated (Fig. 7a) so as to rotate the assembly 300 into the position for contact with the seal where it rests with the electrodes 305a, 305b on the wound steel.

At this point, current is supplied so as to perform the first weld which causes joining of the steel strip during the first wound turn.

Once the first weld has been completed, the mandrel rotates a predetermined amount and stops so as to perform further welds for closing the steel ring, repeating the aforementioned steps until the minimum number of (three) welds prescribed by the corresponding standards is achieved.

Once the last weld of the first group of welds has been performed the cylinder 309 brings the welding assembly 300 back into the disengaged position and the seal winding cycle is started with the insertion (by known means not shown) of the strip lb with insulating characteristics and operation of the mandrel which performs a number of turns until it reaches the final diameter of the seal, under the control of a linear transducer or the like which is connected to a programming and control device 500 for example of the PLC type, not described in detail.

This step of inserting the insulating strip is known per se and not described or illustrated in detail .

Once winding of the graphite strip lb has been performed, only the steel strip la is wound a further number of turns (for example two turns), said strip having been cut to obtain the final diameter; the welding cycle described above is started again in order to perform the final welds for closing the seal, at the end of which the machine stops.

The assembly 300 returns into its rest position and the assembly 200 is lowered by means of the cylinder 210 so as to allow the extraction of the finished seal with separation from the winding disc .

CASE B - INNER RING

In the case where the seal is wound onto an inner ring 2 (Fig. 6) the initial cycle is different, namely: the operator loads the inner ring 2 onto a self-locking chuck 2a and the automatic cycle is started .

The steel strip la is fed forwards using known means until the free inner end is in the position where it makes contact with the inner ring and is axially aligned with the centre thereof,

the cylinder 309 is activated so as to position the welding discs exactly in the centre of the axis III-III of Figs. 3 and 6;

the cylinder 210 is activated so as to bring the top part of the welding discs into contact with the steel strip and weld it directly onto the inner ring .

The cylinder 210 then returns into the initial position and the cylinder 309 brings the welding assembly back to the starting point and the pressing assembly is again raised with the cylinder 210 until it comes into contact with the steel strip .

At this point the seal construction cycle starts again, this being the same as that already described for the winding disc.

According to preferred embodiments it is envisaged that the cylinder 210 is controlled by a proportional electronic valve which, upon activation of a program defined by a PLC of the control means 500, allows a constant pressure to be maintained on the seal upon variation of its diameter during winding; in this way it is possible to use a low pressure in order to perform welding and a high pressure in order to achieve a greater compactness of the seal.

It is clear from the description above how, with the arrangement of the welding assembly coupled to and mounted on the pressing assembly, the following advantages may be obtained:

possibility of automatically positioning the welding assembly with respect to the seal being wound following positioning of the pressing assembly against the said seal;

- possibility of performing automatically the first weld in the inner ring with the welding assembly positioned exactly above the pressing wheel and brought into contact with the steel by means of the cylinder 210 which exerts the necessary pressure for performing the weld;

welds performed close to the guiding point defined as the point of contact between the pressing disc and the strip being wound, so as to avoid possible displacement of the axis of the seal, as may occur, particularly in the case of a large diameters, in machines where the welding point is on the opposite side to the guiding point; preferably the welding point must be situated as close as possible to the guiding point in order to avoid the aforementioned misalignment.

small overall dimensions of the apparatus and consequent possibility of application also to small size machines which may however wind both seals with a small diameter (1/2 inch) and seals with a diameter of up to 5 m;

- elimination of the adjustments, compared to the large-format machines of the prior where it was necessary for the welding assembly to be displaced so as to be always perfectly radially positioned in relation to the different diameters.

Furthermore the following further advantages are obtained :

- no need for adjustment for the different formats, the difference in terms of working stroke between the small diameter and the large diameter being covered by the working stroke of the welding assembly operated by the cylinder 309, as shown in Figs. 7a and 7b in which the winding mandrel is not shown;

- micrometric adjustment of the distance between the electrodes and of centring with the seal so as to ensure a better machining precision.

Although described in connection with a number of embodiments and a number of preferred examples of embodiment of the invention, it is understood that the apparatus may be used also in sectors other than the gasket production sector and that the scope of protection of the present patent is determined solely by the claims below.

Claims

1. Welding apparatus for machines for producing seals comprising two strips (1), a first strip (la) of which has superior mechanical characteristics and a second strip (lb) of which has superior sealing characteristics, said seals being wound by means of a winding assembly (100) rotating about a longitudinal axis (X-X) of rotation; the apparatus comprising :

- a pressing assembly (200) arranged to operate on the seal being wound;

- a welding assembly (300) for welding the first strip (la) being wound, comprising two electrodes (305a, 305b) ;

characterized in that:

the pressing assembly (200) has a support (202) to which there is fastened a hub (302) rotating about an axis parallel to a longitudinal direction (X-X) during use parallel to the axis of rotation of the winding assembly and arranged aligned with the pressing wheel (201) in the transverse direction (Y-Y) , said hub having an extension (302b) towards the outside in the transverse direction (Y-Y) carrying the welding assembly (300), the rotation of the hub being designed to move the welding assembly from a position disengaged from the seal being machined into a position in contact therewith so as to weld the first strip (la) and vice versa, upon operation of actuating means (309); and that the position of the said pressing assembly can be adjusted in the vertical direction (Z-Z) by means of movement means (210) able to be connected to fixed elements and locked in position by locking means (213,213a), the adjustment of the pressing assembly causing the automatic positioning of the welding assembly depending on the desired diameter of the seal being wound.

2. Welding apparatus according to Claim 1, characterized in that said support (202) is in the form of a "U" and is guided on a ball-mounted sliding block (203) integral with the support (202) .

3. Welding apparatus according to Claim 1 or 2, characterized in that said hub (302) is rotating on bearings (302a) keyed on a shaft (303) axially aligned with the pressing wheel (201), mounted on the support (202) and extending parallel to the longitudinal direction (X-X) .

4. Welding apparatus according to Claim 3, characterized in that the shaft (303) supporting the hub (302) has a threaded end (303a) which can be coupled to a graduated knob (304), rotation of which causes the displacement of the hub (302) in both senses of the longitudinal direction (X-X) , varying correspondingly the position of the welding assemb1y (300).

5. Welding apparatus according to Claim 1, characterized in that the electrodes are two welding wheels (305a, 305b) rotating about a longitudinal axis (X-X) , between the welding wheels there being arranged a spring (310) extending parallel to the longitudinal direction (Y-Y) and able to maintain the correct interaxial distance between the two welding wheels and the bearing on the conducting supports.

6. Welding apparatus according to Claim 1, characterized in that said welding assembly (300) comprises two lateral and parallel bars (306a, 306b) extending in a direction substantially perpendicular to the extension (302b) of the hub, the respective free top end of the bars (306a, 306b) having, fixed thereto, in an insulated manner, a conducting plate (307a, 307b) which carries at a first end the cables (315) for supplying the electric current and at the other end the welding wheels (305a, 305b) pivotably mounted on the said plates from which they receive the electric current .

7 . Welding apparatus according to Claim 6, characterized in that said bars (306a, 306b) are kept spaced from each other by a compression spring (308) coaxially mounted on an adjusting screw (308a) passing though the bars (306a, 306b) and able to be operated by a graduated knob (308b) for adjusting the distance between the two electrodes (305a, 305b) .

8. Welding apparatus according to one of the preceding claims, characterized in that said pressing assembly (200) comprises a disc (201) mounted on the support (202), the pressing assembly

(200) being movable in both senses of the vertical direction (Z-Z) upon operation of a cylinder (210) which is fastened to fixed elements outside the apparatus and the rod of which is connected to the support (202) .

9 . Welding apparatus according to Claim 7, characterized in that said locking means comprise a clamp (213) able to lock the actuating cylinder (210) of the welding assembly (300) at a distance, in the vertical direction, from the winding assembly, depending on the seal to be made.

10 . Machine for forming seals wound onto a support ring, which comprises an assembly (200) for winding seals comprising two strips (1), a first strip (la) of which has superior mechanical characteristics and a second strip (lb) of which has superior sealing characteristics, said seals being wound by means of a winding assembly (100) rotating about a longitudinal axis (X-X) of rotation; characterized in that it comprises an apparatus for welding the first strip (la) according to the preceding claims.

11. Machine according to Claim 9, characterized in that the winding assembly (100) comprises a mandrel (110) rotating about the longitudinal axis (X-X) and carrying a winding disc (108) having a radial incision (108a) for inserting the free end of the strip to be wound.

12. Machine according to Claim 9, characterized in that the winding assembly (100) comprises a self locking chuck (2a) which carries an inner ring (2) .

13. Machine according to Claim 9, characterized in that the rotation of the welding assembly about its axis is designed to bring the welding wheels to a point of contact with the first strip which is as close as possible to the guiding point, both for small diameters and for large diameters of the seals .