NZ193716A - Powder filled cable manufacture - Google Patents

Description

'1 9371 6 Priority Datefs): .. J.4^ j Comploto Specification Filed: Cf&s-s: tP. L..~nA V H6 1984 So\ Fubiicfitson Dsts: r**t • r~ r '-VVi Y'.' J, wV IZ55 NEW ZEALAND PATENTS ACT, 1953 COMPLETE SPECIFICATION "PROCESS AND PLANT FOR MANUFACTURING TELECOMMUNICATION CABLES" k/We, INDUSTRIE PIRELLI S.p.A., an Italian company, of Servizio Brevetti, Piazzale Cadorna, 5, 20123 - Milan, Italy hereby declare the invention for which ?/ we pray that a patent may be granted to mx/us, and the method by which it is to be performed, to be particularly described in and by the following statement:- 193716 The present invention concerns a process and its relative plant for manufacturing telecommunication cables, and particularly, for cables comprising substantially a bundle of insulated conductors.

Henceforth in this text, we shall intend by the term 'conductor* to indicate a conductor possessing a relative insulation, and by 'powdered expansible material' we shall intend the employment of several substances - under the form of powders, which have the characteristic of expanding when subjected, for example, to absorbing water. Hence due to this characteristic in a telecommunication, introduced between the sheath and the conductors themselves and disposed in such a way as to swell out as a consequence of the entry of water into the cable due to accidental causes - a block is constituted, against any such water spreading throughout the entire cable.

As an example of these substances, mixtures of various powders can be briefly cited - such as those found indicated in the U.S. PATENT No. 4002819; or yet as another example, carboxymethylcellulose, bentonite.

Certain of the cable manufacturing processes cited, are based upon the operation of causing a bundle of conductors, that are already cabled together, to pass into a container having an internal diameter corresponding to that of the bundle, and in sending a mixture of powders through the means of pressurized air,- towards the annular tl 937 16 aperture of the container traversed by the conductors -in such a way as to force the powdered material or the powdered mixture in-between the conductors.

This process still foresees the operations of winding certain tapes around the cable core, for preventing the \ leakage of the powders, and finally the step of extruding a protective sheath.

Unfortunately, during the cabling of the conductors -which is effectuated before these enter into the container, a canal can be formed among the conductors; successively, when the conductors pass into the container, there is had the drawback in that the air - used under pressure at times upto 10 atm - can pass along the canal to the outside of the container - and hence, this could tend to expel the powders that are already introduced in-between the conductors.

A further 'known' process, consists in applying the powdered material electrostatically in-between the conductors - before assembling them together.

This procedure has the drawback of being rather slow, and moreover, with the phased being unsuited as regards the standard cabling machines used for the actual manufacture of telecommunication cables.

Moreover, the powder disposed on the conductors, results in certain cases, as being insufficient with respect to the quantity that is desired, and the further 193716 operation of pre-disposing oil on the surface of the conductors, for consenting the disposition of the powders, in the successive electrostatic phase brings about - as is 'known' to technicians - damages to the conductor insulation, due to the presence itself of the oil, and when the cable is in electrical tension.

Therefore, the purpose of the present invention, is to have a process and plant for manufacturing telecommunication cables incorporating expansible material in powder form, and without manifesting any of the above-cited drawbacks.

What forms the object of the present invention, is a process for manufacturing a telecommunication cable, said cable comprising: a plurality of conductors, a covering sheath disposed around the conductors, material in expansible powder form disposed in-between the sheath and conductors, said process comprising the phases of:- a) causing the conductors to advance through a truncated-cone shaped cavity between an entrance section and an exit section, to said cavity maintaining the conductors separated, one from the other, and converging towards the exit section; b) causing the material in powder form to advance under pressure along a helicoidal course towards the exit section, with mechanical thrusts imparted to said /i r O r? .< o ibo do material for urging said material between the conductors passing through the truncated-cone shaped cavity; and c) covering the conductors with a sheath, upon their exiting from said cavity.

In one form of actuation, the process is characterized by the fact of causing said material to advance between the entry and the exit sections of the cavity, along a helicoidal course disposed all around the conductors and moving the said material-in powdered form from the helicoidal course towards the centre of the cavity, and around the conductors themselves.

What forms a further object of the invention, is an apparatus for manufacturing a telecommunication cable, said cable comprising: a plurality of conductors and at least one external sheath for covering the conductors, said conductors having material in the form of an expansible powder located therebetween, said apparatus comprising:-means for helicoidally thrusting forward the material into a truncated-cone shaped cavity having an entry and an exit section; means for separately guiding each conductor into the cavity in a direction converging towards the. exit section.

Said frusto-conical cavity - in which the conductors advance separately, can be the very same cavity wherein the powders advance in helicoidal fashion.

In this form of realization, the apparatus is characterized by the fact that said means, for helicoidal thrusting forward the material in powder form comprises a frusto-conical casing, a hopper mounted on the casing and communicating with the interior thereof for admitting said powdered material into the casing, a hollow screw member within the casing and having a helicoidal thread, the outer profile of which lies in close proximity to the casi surface, and the inner profile of which forms a frusto-conical chamber in which the conductors pass, and means fo rotating the screw itself.

For a better comprehension of the process and the apparatus of the present invention, there will now be described the basic phases of the process, and the plant that comprises a form of realization for the apparatus, with the aid of the following drawings, wherein:- FIG. 1- represents a cable, manufactured according to the invention; FIG. 2 - represents a longitudinal view of a plant for manufacturing the cable of FIG. 1. >!h 1 9371 6 FIG. 3 - represents a longitudinal section of the basic apparatus of the plant in FIG. 2 for the introduction of the powders.

FIG. 3a. - represents a detail of the apparatus of FIG. 3.

FIG. 4 - represents a view along the line IV-IV of FIG. 3.

FIG. 5 - represents a variation of the basic apparatus of the Invention wherein the means for urging forward the powders are separated from the cavity wherein the conductors pass.

FIG. 6 - represents a view according to the line VI-VI of FIG. 5.

The Invention will now be described with reference to the manufacture of a telecommunication cable 1 (FIG. 1) comprising: a plurality of conductors 2, insulated -for example, with thermoplastic resins, such as polyolefins or vinylic resins, two spiralled overlapped tapes 3,4, an external sheath 5, expansible material 6, under the form of powder- in-between the conductors 2 and the tapes 3 and 4.

For example, the tapes are in polyesther, the sheaths in polyethylene, and the expansible material comprises carboxy1-methy1-cellulose.

In a particular cable, constructed according to this Invention, the inter-spaces between the conductors 193716 and around the conductors, can be filled at least partially, by means of a suitable dosage,"with the expansible material apt for forming a block - against any penetration of water. For example, this material can occupy 30% of 5 the spaces present in the cable-core, and then, if there be any presence of water, to swell out - and thus to block the water from spreading along the cable.

The plant 7 (FIG. 2) for the manufacture of cable 1-, -comprises a station 8 with a plurality of bobbins 9 around. 10 which are wound the conductors 2, a group 10 of the guide- pulleys 11 for the conductors 2 during unwinding, an apparatus 12 for the application of the expansible material, a group 13 for applying spiralled tapes 3 and 4 around . the cable-core, an extruder 14 for covering the core with 15 the sheath 5, a winching drum 15, and a drum 15' for collecting the cable.

The drums 15 and 15' respectively, rotate around their own axis for pulling and collecting the cable, and simultaneously, they also rotate around the axis A-A of the 20 plant 7 - for determining, in a 'known' way, the cabling of the conductors at the exit of the apparatus 12.

The fundamental part relative to the Invention, is constituted by an apparatus 12, the latter parts of the plant 7 are constituted with 'known' devices and hence, 25 herebelow - for simplicity sake, these devices will simply be mentioned wherever necessary. *93716 The apparatus according to the main concept of the Invention, is based upon means apt for helicoidally urging forward the material 6 in powder form (FIG. l) into a frusto-conical cavity defined by two sections and upon further means for guiding the conductors 2 separately, one from the other, into the cavity.

In a preferred form of embodiment, these means are constituted respectively, by an Archimedean screw device 16, that rests upon a base 16' (FIG. 3) and by a special element 17, referred to henceforth here, as the 'die'.

The spiralled device 16 comprises a frusto-conical casing 18, a hopper 19 for the entry of the expansible material in powder form towards the inside of the casing 18, a hollow screw 20 disposed within the casing and having a helicoidal thread rotating around its own axis 21 that coincides with the axis A-A of the plant, means 22 for rotating the screw. The exit of the casing 18 comprises a plug 18' - made out of stainless steel for preference, and having a central hole for the passage of the conductors.

Said helicoidal thread of the screw 20 is disposed with its external profile 23 in the proximity of, and along the inner surface 24 of the casing, and with its inner profile 25 defining a frusto-conical chamber 26, inside which the conductors 2 pass, and which is in communication with the inter-spaces in-between the spirals of the screw. - 9 1 9371 The means 22 for the rotation of the screw, comprise an annular flange 27 made solidal with the extremity 28 of the helicoidal thread in the proximity of the entry section of the conductors 2 in the casing, a pulley 29 empty in the cradle cehtre and connected laterally to the flange 27, an actioning group 30 - comprised by a motor 31, a pulley 32 and a belt 33, associated - through the transmission motion of the screw itself - with the pulley 32 and the pulley 29 respectively.

The screw 20 is supported and centered with respect to the casing, by suitable supporting means which are comprised in the preferred realization of a plurality of rollers 34 applied on the arms 35 of the casing itself -with the axis parallel to the axis of the screw 10, and with a circular distribution around the flange 27 (see FIGS. 3 and 4) .

Said plurality of rollers presses with its own periphery 36 upon a special annular well 37 of the flange 27 - in such a way that the rollers are dragged into rotation by the flange 27 itself, and these rollers prevent any dis-alignment of the screw 20 with respect to the casing 18.

The entry section of. the Archimedean screw device, is limited by a disc sustained by a structure 38 and provided by a plurality of holes 39, distributed according to various circumferential lines, inside which the 193716 conductors 2 pass.

The apparatus 12 is completed by the presence of sealing means between the stationary die 17 and the pulley 29 which is facing and rotary. These means can be diverse, and they are comprised out of materials which are apt for being sealed fixedly either to the pulley 29, or to the die 17, in such a manner that - during the relative motion between pulley and die, there is had a sliding contact and simultaneously a sealing . For example, this material can be comprised of an elastomeric annular gasket 40 having its periphery 41 attached to the pulley 29, and in a lip-seal contact with the circular protuberance having the form of point 43 on the die 17.

The apparatus further foresees sealing means between the casing 18 and the opposed rotating pulley 27 - for example, an annular elastomeric gasket 44 applied as is clearly visible ir: FIG. 3a, in contact with the surfaces of the casing and of the pulley - and for preference, chrome plated for reducing friction to the minimum.

Upstream and downstream of the apparatus 12, suitable containers (not illustrated) may be attached for holding, if necessary, small quantities of powder which come out nevertheless, from the same said apparatus.

The sealing means - made from the material cited, prevent the material from escaping, within this way con-, senting the eliminating of any subsequent operations for i9371t the recovery of such material, and more important still, maintaining practically free, the air surrounding the plant of great quantities of powder dispersed therein. In this manner the health of the workers is also safeguarded .

The plant functions as follows:- The conductors 2 (FIG. 2) subjected to the pull exercised by the drum 15 are gradually unwound from the bobbins 9 and guided from group 10 (of pulley 11) towards the screw device 16 of FIG. 3.

The conductors 2 - which are separated one from the other, cross the device 16 with a convergent direction, owing to the action of the separating and guiding that is imposed upon them by the holes 29 (FIG. 4) of the die 17 within which they pass and from the cabling to which they are subjected when exiting from the casing 18.

During their passage into the screw device, the various conductors cross the frusto-conical chamber 26, remaining inside the helicoidal canal determined by the spirals of the screw 20 that is dragged into rotation around its axis - by means of the actioning group 30 (FIG. 3).

The screw continuously pushes towards the stopper 18' (i.e. according to a helicoidal course), the expansible material loaded under the powder form into the hopper 19, and as the powders gradually approachs the extremity of the casing exit, they are found to occupy even smaller 193716 areas - with, in this way being pushed compactly - and as a consequence, making the said powders to fully penetrate in-between the conductors.

This action is further favoured by the circumstance of the bundle of conductors being further squeezed towards the exit section, with the result of pushing and more compactly enclosing the powders within the bundle.

Successively, when the bundle of conductors 2 - containing the powdered material, issues forth from the Archimedean screw device 16, there takes place the further and following usual phase for manufacturing the cable 1 (FIG. 2): - firstly, the cabling of the conductors is effectuated by rotating the drums 15 and 15' around the axis A-A: - then, the tapes 3 and 4, are applied by means of the group 13; - thereupon, the cable-core is covered with an external protective layer 5, by means of the extruder 14; - finally, there takes place the winding of the cable under the form of turns - with the help of the winch drum 15 and the collecting drum 15'.

One particular advantage of the plant just described, lies in the possibility of filling-up the inter-spaces between the conductors, with powders i.e. even when, for some reason or other, the 'feeding' by means of the hopper is interrupted. In fact, inside the casing - within which the screw rotates, there is deposited*a_ certain quantity §937 1 6 of powder having a volume that is higher than that instantly required by the bundle of cables on exiting from the apparatus. Consequently, the screw is able to push, for a certain period, this powdered material -independently of the load, towards the hopper; with, in this way guaranteeing (at least for the period sufficient for the hopper to be refilled again) a correct manufacturing of the cable.

In a particular embodiment - according to this Invention, the apparatus for applying the powders, comprises means for pushing forward the powders separated by the frusto-conical cavity where the conductors 2 pass - and precisely, with reference to the drawings given in FIGS. 5 and 6:— - a first frusto-conical casing 45, resting on the base 45', inside which the conductors 2 pass separatedly, with being dragged by appropriate pulling means (not illustrated) from the entry section - represented by a die 4.6, to the exit section 47 of the casing; - a second frusto-conical casing 48, inside which a frusto-conical screw 49 rotates with a full-core 50 and thread 51; said screw being dragged into rotation around its own axis 52 by a motor 53 - through the 'known' per se connection means 54-55 - for example, an end-less screw 54, and gears within a casing 55 for rotating the shaft of screw 49.

This second casing is fed with e-xpansible material 9 9371 6 in powder form coming from a hopper 56 and comprising at the exit, an extension 57 the final section of which lies between the conductors 2 of the bundle in the proximity of the section exit 47 of the casing 45, or in a more distant (see FIG. 6), with variations in the load of the powders as a function of the position of the end section of the said extension with respect to the conductors that are convergent one to the other.

The first casing further comprises adequate systems for the exiting of one part of the pov/ders when the pressure - to which they are subjected inside this casing in the vicinity of the hole in the exit section 47, becomes excessive and may risk bringing about a rupture in the conductors themselves.

For example, the apparatus could be provided with an exhaust valve that is set for a pressure value of the powders; otherwise, it could comprise a conduit between the first casing and the hopper - in such a way as to return a certain quantity of powders to the hopper, and - in this manner, to maintain the pressures of the powders in the vicinity of the exit 47 at correct functioning values.

The apparatus of FIGS. 5 and 6, forms part of the plant for manufacturing a cable (FIG. l), as the cable illustrated in FIG. 2.

Even in this case, the powders are forced to follow a 1 9371 helicoidal course - as determined by the turns of the screw 49 at the exit from the extension 57, with a mechanical thrust that guides them forwards towards the frusto-conical part having a narrower section 47 of the casing 45.

Supposing that the casing 45 is half-filled with expansible material in powder form, there is had - as a consequence of the continuous rotation of the screw 49 -a further inflow of powders coming from the hopper 56 and directed from the exit section of the extension 57, in such a way as to continually stretch and fill the upper free space in the proximity of the exit section 47 of the casing 45 - with thus originating a mass of powders, in the form of a frusto-conical 'block' inside which the conductors pass.

The solutions presented in the present Invention, prevent the formation in the powders accumulated in the vicinity of the exit of the casing, of canals originated by the same passage of the conductors having the characteristic as of walls delimiting areas having sections that are greater than the transversal dimension of the conductors.

This situation, if verified, would become extremely unfavourable - since the conductors would pass through the canals without receiving or dragging the powders along with them.

The solutions illustrated in the FIGS. 3 and 5 eliminate to good advantage, these drawbacks. In fact, 193716 the continuous inflow of the new quantities of powders -pushed by the screw 20 (FIG. 3) or by the screw 49 (FIG. 5) causes the collapsing and the continuous re-mixing of the canal walls eventually formed by the passage of the conductors and therefore, this guarantees the contact and the dragging of the powders among the conductors.

Although this present Invention of ours has been described in a particularly advantageous form of realization, it has nevertheless toJoe kept in mind that within the ambit of the protection of this patent have also to be comprised all the variations derived from the inventive principle, that are accessible to a technician of the field. For example, the Invention is applicable for telecommunication cables having compound parts that are diverse to those that are described and illustrated in FIG. 1; or again for example, the screw can have a single or a multiple-thread, as desired.

Claims (13)

WHATCWWr CLAIM IS:

1. A process for manufacturing a telecommunication cable, said cable comprising: a plurality of conductors, a covering sheath disposed around the conductors, material in expansible powder form disposed in-between the sheath and conductors, said process comprising the phases of:- a) causing the conductors to advance through a truncated-cone shaped cavity between an entrance section and an exit section, to said cavity maintaining the conductors separated, one from the other, and converging towards the exit section; b) causing the material in powder form to advance under pressure along a helicoidal course towards the exit section, with mechanical thrusts imparted to said material for urging said material between the conductors passing through the truncated-cone shaped cavity; and c) covering the conductors with a sheath, upon their exiting from said cavity.

2. A process as claimed in claim 1 of causing said material to advance between the entry and the exit sections of the cavity, along a helicoidal course disposed all around the conductors and moving the said material in powder form, from the helicoidal course towards the centre of the cavity and around and between the conductors themselves.

3. A process as claimed in claims 1 or 2 after the phase (b) and before the phase (c), the phase of binding the 18

Ji c *> { C4 ibodu conductors with tapes.;4. An apparatus for manufacturing a telecommunication cable, said cable comprising a plurality of conductors and at least one external sheath covering the conductors, said conductors having material in the form of an expansible powder located therebetween; said apparatus comprising:-;- means for helicoidally thrusting forward the material into a truncated-cone shaped cavity having an entry and an exit section, and;- means for separately guiding each conductor into the cavity in a direction converging towards the exit section.;

5. An apparatus as claimed in claim 4, wherein the means for helicoidally thrusting forward the powdered material comprises: a frusto-conical casing, a hopper mounted on the casing and communicating with the interior thereof for admitting said powdered material into the casing, and a hollow screw member within the casing having a helicoidal thread, the outer profile of which lies in close proximity to the casing surface, and an inner profile of which forms a frusto-conical chamber in which the conductors pass and means for turning said screw.;

6. An apparatus as claimed in claim 5, wherein the means for rotating the screw comprises: an annular flange fixed to the extremity of the helicoidal thread at the entry section, an annular pulley connected laterally to the flange, means for supporting the flange, and power means for rotating;- 19;' ^ 1;153716;the pulley.;

7. An apparatus as claimed in claim 6 including means for supporting the flange, comprising: a plurality of rollers supported on arms fixed to the casing with the axes of said rollers being parallel to the central longitudinal axis of the casing, said rollers being positioned around the flange and in contact with an annular well in said flange.;

8. An apparatus as claimed in claim 6 and 7, which includes sealing means positioned between the pulley and the screw.;

9. An apparatus as claimed in claim 8, that the said sealing means comprise an annular gasket of elastomeric material, fixed to the pulley and in sliding contact with a projection on said casing projection.;

10. An apparatus as claimed in any one of claims 4 to 9, wherein the means for guiding the conductors comprises a disc having holes therein for the passage of the conductors.;

11. An apparatus as claimed in claim 4, wherein said means for helicoidally urging powdered material forwards comprises a first frusto-conical casing through which the conductors separated one from the other and guided by special means pass, a second frusto-conical casing within which a full-core frusto-conical screw turns, said second casing being connected by one extremity to a hopper, and having at its opposite end an outlet extension whose end section is disposed between the conductors which pass through the first casing, and which outlet extension;1c *> yy f bo i 1 is directed towards the exit of the first casing.

12. An apparatus, as in claim 11, wherein said special means for guiding the conductors in the first casing comprises a disc fixed to an entry section of the first casing, said disc being provided with holes for the passage of the conductors.

13. An apparatus as claimed in claims 11 or 12, wherein the outlet extension is located in proximity of the exit of the first casing. fHv (tot/their authorised Agents 21