CA1081811A

CA1081811A - Process and apparatus for producing screened unitary elements and the novel elements so produced

Info

Publication number: CA1081811A
Application number: CA253,526A
Authority: CA
Inventors: Antonio Ferrentino
Original assignee: Industrie Pirelli SpA
Current assignee: Industrie Pirelli SpA
Priority date: 1975-05-28
Filing date: 1976-05-27
Publication date: 1980-07-15
Also published as: IT1038547B; ES448491A1; AR212706A1; GB1546609A

Abstract

ABSTRACT OF THE DISCLOSURE: A process for producing an electrically screened communication cable unit com-prising a pair of screening tapes surrounding a plurality of electrical conductors, each of such tapes comprising a sheet of high conductivit ?etal coated on its inner face with a thermoplastic resin and the tapes being bonded to-gether at their edges by heat sealing the respective inner faces together, which differs from prior art processes in that the conductors and the tapes with their thermo-plastic resin coated faces facing the conductors are fed to a forming and sealing zone where the tapes are formed around the conductors and sealed together at their faces.
The tapes are sealed together at longitudinal ribs with a rib intermediate groups of conductors and may be sheared along an intermediate rib to provide two units each com-prising such tapes and a plurality of conductors. Also, apparatus for performing such process and the novel cable units produced thereby.

Description

The present invention relates to a process for producing individually screened unitary elements or ele-mentary circuits (pairs, quads, trefoils, coaxial cables and the like), suitable for making communication cables, as well as to apparatus intended to carry out said process and the individually screened unitary elements or ele-mentary circuits produced according to said process.
It is known that, in order to improve cross-talk between the elements of a telecommunication cable, in addition to adopting usual expedients, such as, for ex-ample, the choice of appropriate quadding and doubling pitches and the arrangement of said elements in convenient relative positions, it may be necessary to provide each element or elementary circuit constituting the cable with an electromagnetic and/or electrostatic screen.
In particular, Italian Patent No. 983,995 of the same applicant refers to an improved screen for the unitary element or elementary circuit of a telephone cable.
Said improved screen has a tubular shape and is constituted by a composite tape, namely, a tape consisting essentially of a good-conducting metal sheet (for example, aluminum, copper, etc.), plated on at least one face or surface with thermoplastic synthetic resin material, for example, polyethylene, turned towards the inside.
However, a preferred embodiment includes a triple tape, namely, a tape in which both faces or surfaces are plated with synthetic resin, but in which the surface layer, which, in the individually screened unitary element or elementary circuit is directed to the outside, is made of polyester resin and preferably, but not necessarily, of polyethyleneglycolterephthalate.
Among the various embodiments suggested in the .

` 1081811 cited Italian patent, the electrostatic and/or electromagnetic screen which proved particularly effective is one in which the unitary screen is defined as constituted by a first and a second composite tape adjacent to each other and wound up on the unitary element or elementary circuit in such a way as to result in their facing the one to the other and with each subtending a center-angle of at least 180.
The corresponding edges of said tapes are two by two in mating contact and are sealed along their inner surfaces coated with thermoplastic material.
Practically, said electrostatic and/or electromagnetic screen is therefore constituted by two strips of composite tape which enclose a unitary element or elementary circuit, and the two strips are jointed along two longitudinal ribs by casting the plating of thermoplastic material.
The present invention has, an object, the providing of a process intended to carry out industrially a screened element enclosing a plurality of unitary elements as indicated hereinbefore, arranged parallel to one another and mutually screened, or with only one screened unitary element.
A further object of the invention is the provision of an apparatus for carrying out the hereinbefore indicated process.
According to one aspect of the present invention, there is provided a process for producing a plurality of individually screened unitary elements or elementary circuits of electrical conductors, each element or circuit being surrounded by a tubular screen, said tubular screen being constituted by a pair of tapes sealed together, each tape comprising a sheet of good-conductivity metal having its surface facing toward the element or circuit plated with a thin layer of a thermoplastic synthetic resin, said process comprising: continuously advancing a plurality of said elements or circuits longitudinally toward a screen application zone with said elements or circuits in spaced relation and substantially in the same plane; simultaneous-ly advancing from opposite sides of said plane and toward said zone a first said tape and a second said tape, said first tape and said second tape each having a width greater than the dimension between the outer sides of said elements or circuits and being advanced at the same speed as said elements or circuits with their plated surfaces facing toward said elements or circuits; shaping said tapes into tubes around said elements or circuits in said zone by bringing the tapes into contact at their plated surfaces both intermediate said elements or circuits and at the outer sides of said ~:
elements or circuits to form longitudinal ribs both between and outside of said elements or circuits while maintaining the thickness of the tapes sub-stantially unaltered substantially throughout their widths except possibly any thickness change at the ribs due to resin flow thereat when the plated surfaces are brought together and heated as set forth hereinafter; and applying heat to said tapes, at least along said ribs, to bond the resin of one tape to the resin of the other tape.
A preferred embodiment of the invention is a process as described, in which, before the final shaping phase, a phase for pre-forming said first and second tapes is employed, which pre-forming is intended to give to each tape a form approximate to the final one destined to be subjected to the heat sealing.
Another preferred embodiment of the invention is a process as described in which, after the heat sealing phase, there is a phase of shear-ing longitudinally the sealed ribs of said first and second tapes, so as to separate each individually screened unitary element or elementary circuit of said plurality from the adjacent one or ones.
According to another aspect of the invention, there is provided apparatus for performing the process, the apparatus comprising shaping and sealing means for shaping and sealing said tapes into tubes with adjacent ribs without significantly altering the thickness of the tapes throughout their widths except possibly any thickness change at the ribs due to resin flow thereat when the plated surfaces are brought together and sealed, feeding means in advance of said shaping and sealing means for feeding a plurality of electrical conductors in spaced relation and substantially in -r ~ii _ 3 _ ,j ,;~

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~ 31811 a plane to said shaping and sealing means, a pair of tape feeding means in advance of said shaping and sealing means, one tape feeding means on one side of said plane and the other tape feeding means on the other side of said plane, for feeding said tapes to said forming and sealing means at the same speed as said conductors are fed to said shaping and seallng means and with one tape at one side of said conductors and the other tape at the other side of said conductors.
A further embodiment of the above apparatus contemplates, down-stream of the forming and/or heat sealing equipment, a device provided with circular knives.
Other objects and advantages of the invention will be apparent ; to those skilled in the art from the following detailed description of the presently preferred embodiments thereof, which description should be con-sidered in conjunction with the accompanying drawings in which:
Fig. 1 shows schematically an embodiment of the apparatus intended to carry out the process of the invention;
Fig. 2 shows in perspective elementary circuits or unitary screened elements obtained with the process of the invention and the apparatus shown in Fig. l;
Fig. 3 shows in perspective a single elementary circuit or unitary screened element obtainable according to the invention; and Fig. 4 represents schematically and in perspect-ive a detail of the apparatus shown in Fig. 1. -The apparatus schematically shown in Fig. 1 re-presents a practical line of production for individually screened unitary elements or elementary circuits.
The apparatus illustrated in Fig. 1 includes a unit 41 for feeding a plurality of unitary elements or elementary circuits 10 (pair, quad, trefoil, etc.). The elements or circuits lO are formed by insulated electrical conductors, such as the conductors 23 and 24 in Fig. 2 or the conductors 35 in Fig. 3. Such feeding unit 41 for the unitary elements or elementary circuits 10 may con-sist either of doubling or quadding machines, etc., feeding the elements 10 directly, or may consist of appropriate storing coils arranged in such a way as to allow the feed-ing of a plurality of unitary elements or elementary cir-cuits 10 all lying substantially in the same plane, spaced the one from the other and fed at constant speed in the direction of the arrow F.
At the opposite sides of the plane of said plurality of unitary elements or elementary circuits 10, there are a first and a second feeding coil 11 and 12, respectively, of a first and a second composite tape 13 and 14. The feeding coils 11 and 12 rotate in opposite directions.
Downstream of the feeding coils 11 and 12, there are two pairs 15 and 16 of transversal guide rollers, respectively for the tapes 13 and 14, followed by equip-LO~

ment for forming and simultaneously heat sealing said composite tape along longitudinal ribs. In the example, this equipment consists of at least one pair of rollers, that is to say, a first roller 17 and a second roller 18 cooperating with each other.
The faces of these rollers 17 and 18 (see Fig.
4) are provided with reliefs 29a, 29_ and 29c alternating with grooves 30. In the working position, the reliefs 29 of the first roller 17 engage the reliefs 29 of the second roller 18, the roller 17 being pushed against the roller 18 by means of elastic elements (not shown), which may, for example, be springs.
Preferably, one of the two rollers, for example, the roller 18, has the support for its own shaft held in a fixed position. The roller 17 has the support for its own shaft movable, so that the axes of the two rollers may be moved away from or toward each other, the axes remaining always parallel. Said elastic elements, e.g., springs, are also adjustable and hold the rollers 17 and 18 in mutual contact, with the pressures in the contact zones adjustable according to the requirements of the tape hea~ sealing.
Each roller 17 or 18, or at least one, either totally or at least along the reliefs, is heated, for ex-ample, by means of a heating device consisting of a re-sistance heating unit (not shown), preferably internal to each roller and inside a recess 40 provided in one or both of the lateral faces of the roller itself.
The number of the grooves 30 of each roller 17 and 18 corresponds to the number of the unitary elements or elementary circuits 10.
In the particular case illustrated, the equip--- ,7' ---.~, .

ment for forming and the equipment for heat sealing are the same, but it is possible to have embodiments in which the forming equipment and the heating equipment are separate The drawing element 42 for the plurality of unitary elements or elementary circuits 10, as well as of said first and second tapes 13 and 14, may be located downstream of the heat sealing device. However, in an embodiment of the invention, said drawing element may be the forming and heat sealing rollers 17 and 18. In this case, the rollers 17 and 18 are motor driven so as to act as the drawing element.
In a further embodiment, the drawing element 42 may be the collection device for the individually screened unitary Plements or elementary circuits 10.
Downstream of said first and second rollers 17 and 18, there is a device provided with knives, e.g., peripheral knife edges. Said device, in the illustrated case, consists of a second pair of cooperating rollers which are shown as a third roller 19 and a fourth roller 20.
Preferably, only one of the rollers of the se-cond pair, for example, the roller 19, is provided with knives. In this case, the other roller 20 is provided with abutments corresponding to each knife of the roller 19. The knives of the third and/or fourth roller 19 and 20 are lined up with the center-line 28 (Fig. 2) of the corresponding reliefs 29b of said first and second rollers 17 and 18. In an embodiment of the invention, said knives may be lined up only with the intermediate reliefs 29_ and not with the end reliefs 29a and 29c of the rollers 17 and 18. In this case, the number of knives C - ~8 -lQ8~81~
would be equal to the number of the plurality of unitary elements 10 less one, that is, n - 1.
In a further embodiment, said device provided with knives may be omitted and, instead, there may be the collection device of the group of n individually screened unitary elements or elementary circuits 10, which exit from the forming and heat sealing pair of rollers 17 and 18.
During the working of the apparatus schemati-cally illustrated in Fig. 1, the plurality of unitary ele-ments or elementary circuits 10 spaced from each other advances in the direction of the arrow F in a plane inter-mediate the two feeding coils 11 and 12. The first compo-site tape 13 and the second composite tape 14, unwinding respectively from coils 11 and 12, are respectively driven transversely to the direction of feed by the two pairs of rollers 15 and 16, have transverse dimensions larger than the transverse dimensions of said plurality of elements 10. The image produced by projection of the periphery of the unitary elements 10 on said first and second tapes 13 and 14 is within the edges of the tapes 13 and 14.
Said tapes 13 and 14 consist of at least a good-conducting metal sheet, such as aluminum, plated at least on one face with thermoplastic material, e.g., polyethylene, but preferably, also plated on the other face with a syn-thetic resin of the polyester type, e.g., polyethylenegly-colterephthalate.
Said first composite tape 13 and said second composite tape 14 unwind specularly with respect to each and with their faces or surfaces 33 and 34, respectively, plated with thermoplastic material, facing toward the plurality of elements 10, on which they converge, from 811~
opposite sides, in the leading zone 21 of said first roller 17 and second roller 18 which cooperate with each other. From the zone 21, the tapes 13 and 14 with said plurality of elements 10 pass at constant speed between the roller 17 and 18, pulled by the drawing element 42 or by the rollers 17 and 18, in case these latter are motor driven. The grooves 30 of the rollers 17 and 18 allow the passage of the unitary element or elementary circuit with the tape strips enclosing it, whereas the reliefs 29, besides forming ~he tapes around the unitary elements or elementary circuits 10, heat them at a temperature which will bring their thermoplastic plating to a plastic state, so as to allow the heat sealing along longitudinal ribs 28 (Fig. 2) intermediate one unitary element and the adja-cent one, namely, between two contiguous unitary elements, and along peripherals ribs 25 and 26 (Fig. 2), on the out-side with respect to the unitary elements 10.
In Fig. 2, the plurality of unitary elements or elementary circuits 10 is represented by only two units 23 and 24 (n=2), but it will be understood that the num-ber of unitary elements or elementary circuits 10 can be greater than 2.
The tape-shaped product 27 of the heat sealing could be sent, either directly or after a passage through a cooling apparatus or another apparatus, to the collection device or to an appropriate processing line, because it represents an assembly of individually screened unitary elements or elementary circuits which are enclosed by a first and a second composite tape, which are spaced from one another, and which are screened with respect to one another and to the external ambient by means of heat-sealed longitudinal ribs 22, 25 and 26.

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'' -` 3L6:3 81~11 When it is wished to obtain single screened unitary elements or elementary circuits (see Fig. 3), in which only one unitary element 35 is enclosed between two strips of composite tape 36, 37, sealed or heat-sealed along two peripheral ribs 38 and 39, the tape-shaped pro-duct 27 is caused to advance through the second pair of rollers 19 and 20. These rollers 19 and 20, by means of their knives (not illustrated), but being of conventional shape, shear the longitudinal ribs 22 (Fig. 2) along the center-line 28 (shown in dotted lines in Fig. 2).
A further and preferred embodiment of the apparatus or production line according to the invention provides, upstream of the rollers 17 and 18, at least a device, preferably a pre-shaping mold (not shown) for the tapes 13 and 14, which allows the latter to reach gradually the final shape without suffering rapid, one-stage deformations which might produce cracks in the tapes.
As already indicated hereinbefore, a further and preferred embodiment provides a cooling system (not shown) downstream of the rollers 17 and 18. This serves in particular, but not exclusively, to bring the ribs to be cut to a non-plastic state in a short time. Among the cooling systems, the use of a ventilation device em-ploying air jets is preferred.
The same result can be obtained by providingelements (not shown) able to adjust the temperature of the heat-sealing device, or of the rollers 17 and 18.
To this purpose, for example, use could be made of a thermocouple in contact with the rollers 17 and 18, or an optical thermometer able to measure the temperature of the tape-shaped product 27 exiting from the rollers 17 /~
-- ,a~ -- ' . ` ~' and 18. When said temperature exceeds the pre-established value, the resistance heating unit for heating the rollers 17 and 18 is automatically cut off.
A further embodiment provides, downstream of the feeding unit 41, elements able to space or to line up the unitary elements or elementary circuits 10.
A further and preferred embodiment also provides means for marking the unitary elements or elementary cir-cuits contained in the tape-shaped product 27 exiting from the forming and/or heat sealing station. For said differ-entiation by marking, resort can be had to identification marks both outside and inside the screening envelope. Use could be made of marking techniques employing dyes, to be carried out on the production line, downstream of the rollers 17 and 18.
In a further embodiment, screening tapes could be adopted which are numbered or colored on their surfaces directed towards the outside.
The identification mark could also be inside the screening envelope. As is already known, it could be based on appropriate colors of the unitary elements or ele-mentary circuits, or could be made by joining to these an identification thread of colored cotton.
Although preferred embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various modifi-cations may be made without departing from the principles of the invention.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for producing a plurality of individ-ually screened unitary elements or elementary circuits of electrical conductors, each element or circuit being surrounded by a tubular screen, said tubular screen being constituted by a pair of tapes sealed together, each tape comprising a sheet of good-conductivity metal having its surface facing toward the element or circuit plated with a thin layer of a thermoplastic synthetic resin, said process comprising:
continuously advancing a plurality of said elements or circuits longitudinally toward a screen application zone with said elements or circuits in spaced relation and substantially in the same plane;
simultaneously advancing from opposite sides of said plane and toward said zone a first said tape and a second said tape, said first tape and said second tape each having a width greater than the dimension be-tween the outer sides of said elements or circuits and being advanced at the same speed as said elements or circuits with their plated surfaces facing toward said elements or circuits;
shaping said tapes into tubes around said elements or circuits in said zone by bringing the tapes into con-tact at their plated surfaces both intermediate said elements or circuits and at the outer sides of said elements or circuits to form longitudinal ribs both between and outside of said elements or circuits while maintaining the thickness of the tapes substantially unaltered substantially throughout their widths except possibly any thickness change at the ribs due to resin flow thereat when the plated surfaces are brought together and heated as set forth hereinafter;
and applying heat to said tapes, at least along said ribs, to bond the resin of one tape to the resin of the other tape.

2. A process as set forth in claim 1, wherein said shaping step and said heat applying step are carried out simultaneously.

3. A process as set forth in claim 1, wherein said shaping is carried out in two phases, both said tapes being partly formed in a first phase and being formed to the final shape of tubes with adjacent ribs in a second phase.

4. A process as set forth in claim 1, further comprising cooling of the tapes downstream of the heat sealing thereof.

5. A process as set forth in claim 1, further comprising applying distinctive marking to each screened element or circuit during the produc-tion thereof far identification purposes.

6. A process as set forth in any of claims 1-3, further comprising shearing the tapes along the longitudinal rib or ribs between said elements or circuits so as to provide a plurality of screened elements or circuits.

7. Apparatus for performing the process of claim 1 comprising shaping and sealing means for shaping and sealing said tapes into tubes with adjacent ribs without signficantly altering the thickness of the tapes throughout their widths except possibly any thickness change at the ribs due to resin flow thereat when the plated surfaces are brought together and sealed, feeding means in advance of said shaping and sealing means for feeding a plurality of electrical conductors in spaced relation and substantially in a plane to said shaping and sealing means, a pair of tape feeding means in advance of said shaping and sealing means, one tape feeding means on one side of said plane and the other tape feeding means on the other side of said plane, for feeding said tapes to said forming and sealing means at the same speed as said conductors are fed to said shaping and sealing means and with one tape at one side of said conductors and the other tape at the other side of said conductors.

8. Apparatus as set forth in claim 7, wherein said shaping and seal-ing means comprises means for heating said ribs for simultaneously heat sealing said tapes along said ribs as the tapes are shaped.

9. Apparatus as set forth in claim 8 wherein said shaping and sealing means comprises a pair of opposed grooved rollers, each roller having peripheral grooves shaped to provide the external configuration of the tubes and intermediate peripheral rib forming surfaces, the rollers being mounted with the grooves and intermediate surfaces aligned and with the grooves spaced and sized and the intermediate surfaces spaced to permit the tapes to pass therebetween without significantly altering the thickness of the tapes throughout their widths.

10. Apparatus as set forth in claim 8, wherein said heating means comprises an electric heating unit.

11. Apparatus as set forth in claim 9, further com-prising means for driving said rollers and thereby drawing said tapes through said rollers.

12. Apparatus as set forth in claim 8, further com-prising shearing means downstream of said shaping and sealing means for shearing said tapes intermediate pairs of conductors and along the seal line between said tapes.

13. Apparatus as set forth in claim 12, wherein said shearing means comprises a pair of opposed rollers at least one of which has a peripherally extending knife edge thereon, the plane of said knife edge being aligned with the plane of the intermediate surface of one of said pair of rollers of said shaping and sealing means.

14. Apparatus as set forth in claim 13, further comprising means for at least partially preshaping both said tapes mounted in advance of said shaping and sealing means.

15. Apparatus as set forth in claim 13, further com-prising cooling means downstream of said shaping and sealing means for cooling said tapes.

16. Apparatus as set forth in claim 15, wherein said cooling means comprises jets for directing air on said tapes.

17. Apparatus as set forth in claim 13, wherein said shaping and sealing means comprises means for maintaining the temperature of the rollers thereof within a predetermined temperature range.

18. Apparatus as set forth in claim 13, further comprising guide rollers intermediate said tape feeding means and said shaping and sealing means for directing said tapes transversely of a direct path between said tape feeding means and said shaping and sealing means.