GB1604438A

GB1604438A - Electrical connections

Info

Publication number: GB1604438A
Application number: GB53702/77A
Authority: GB
Original assignee: Raychem Pontoise SA
Current assignee: Raychem SA
Priority date: 1977-12-23
Filing date: 1977-12-23
Publication date: 1981-12-09
Also published as: CA1137186A; FR2412968A1; DE2855602A1

Description

(54) ELECTRICAL CONNECTIONS (71) We, RAYCHEM PONTOISE S.A., a French Company, of Rue de I'Industrie, Lotissement Industriel Courcelles, 95310 Saint Quen I'Aumone, France, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to heat-recoverable articles and, more especially, to their use in forming and insulating electrical connections.

The formation and insulation of electrical connections to substrates has, until recently, involved a series of operations. First, the substrate is prepared, next the electrical connection is made, for example mechanically and/or by soldering, and finally the connection is insulated.

Over the last decade this process has, to some extent, been simplified by so-called heat-recoverable articles, especially heatshrinkage articles, which are now widely used in many areas where insulation, sealing and encapsulation are required. Usually these articles recover, on heating, towards an original shape from which they have previously been deformed, but the term "heatrecoverable" as used herein also includes an article which, on heating, adopts a new configuration, even if it has not been previously deformed.

In their most common form, such articles comprise a heat-shrinkable sleeve made from a polymeric material exhibiting the property of elastic or plastic memory as described, for example, in U.S. Patents 2,027,962; 3,086,242 and 3,597,372. As is made clear in, for example, U.S. Patent 2,027,962, the original dimensionally heat-stable form may be a transient form in a continuous process in which, for example, an extruded tube is expanded, whilst hot, to a dimensionally heat-unstable form but, in other applications, a preformed dimensionally heat stable article is deformed to a dimensionally heat unstable form in a separate stage.

In other articles, as described, for example, in British Patent 1,440,524, an elastomeric member such as an outer tubular member is held in a stretched state by a second member, such as an inner tubular member, which, upon heating, weakens and thus allows the elastomeric member to recover.

Heat-shrinkable sleeves find many applications, especially in the connection and termination of wires, cable and pipes. However, there are other applications where it is desirable to provide a connecting, insulating or protective heat-recoverable member for elongated objects such as cables and pipes where the ends are not accessible or, if they are accessible, where it is undesirable to disconnect or otherwise displace them. For such applications so-called "wrap-around" sleeves have been developed. Basically these are heat-recoverable sheets which can be wrapped round the substrate to form a generally tubular shape and which, in general, are provided with fastening means for holding them in the wrapped-up configuration during recovery. Typically such fastening means are mechanical in nature and comprise, for example, rigid clamps, pins or channel members which co-operate with suitable shape moulded or extruded protuberances adjacent to the overlapping edges of the heat-recoverable sheet. Various types of fastening means are described, for example, in U.S. Patents 3,379,218 and British Patents 1,155,470; 1,211,988 and 1,346,479. In other applications the sheet may be held in the wrapped-up configuration during recovery by means of an adhesive which may, in some cases, be applied on site.

Wrap-around devices of the type described above have been successfully employed in many applications. However, in general, the previously proposed wrap-around devices have proved unsuitable for forming electrical connections, e.g. earth connections, to continuous substrates, e.g. elongate substrates having inaccessible ends, for example, supply lines such as electric cables especially coaxial cables. With tubular heat-recoverable sleeves of unbroken cross-section it has proved possible to provide insert members made, for example, from solder, so that, on heating, recovery and the formation of a soldered connection occur simultaneously (as described, for example in British Patent 1,062,043). This has been virtually impossible with wrap-around devices and, although it has been proposed in U.S. Patent 3,467,761 to use a wrap-around sleeve as an electrically shielded jacket around conductors and cables with provision for an earth connection, the sleeve is somewhat complicated and comprises a specially designed electrically conductive liner. Even with this, it is not possible simultaneously to effect recovery and the making of the earth connection.

Thus to date, there has been no successful solution to this problem.

The present invention provides a method of forming an electrical connection to a substrate which comprises the steps of (a) positioning about the substrate a heat-recoverable wrap-around device which comprises heat-recoverable sheet material and retaining means which co-operates with and engages opposed edge regions of the sheet material, the retaining means being provided with means for receiving and engaging an electrical component to connect it electrically to the substrate positioned within the wrap-around device.

(b) engaging an electrical component in said receiving means; and (c) heating said sheet material to cause recovery and to effect an electrical connection between said component and said substrate.

The present invention also provides a heat-recoverable wrap-around device which comprises heat-recoverable sheet material and retaining means which co-operates with and engages opposed edge regions of the sheet material, the retaining means being provided with means for receiving and engaging an electrical component so as to connect it electrically to a substrate positioned within the wrap-around device.

By using the retaining means to form the electrical connection we have found that it is now possible to effect recovery and the formation of the connection in a single operation and the devices of the present invention are, therefore, extremely useful in making electrical connections to continuous, i.e. elongate, substrates. One particularly useful application is in the connection of earth leads to the conductive sheaths of electric cables such as coaxial cables.

In especially preferred embodiments of the present invention, the retaining means is an electrically conductive buckle, generally made from sheet material such as copper, and is provided with means for receiving an electrical components, for example an earth lead, to facilitate formation of the connection. Such members may, for example be provided by cutting or otherwise forming the buckle to provide a small bridge member under which the earth lead passes so as to be held against the main body of the buckle by resilient and/or frictional forces. Alternatively, the buckle may comprise one or more slots in which the earth lead is held, for example, by frictional forces.

The end of the earth lead may be tinned prior to inserting it in the buckle and/or the buckle itself may be provided with a solder preform. If these measures are taken it is possible to effect recovery and form a soldered connection in a single operation, which is especially advantageous.

In many of the preferred wrap-around devices used in the method of the present invention, the surface of the device after recovery lies more or less flush with the surface of the substrate. Attention is drawn in this respect to our copending Application No. 53730/77 (Serial No 1604439). inventors Lagardere and Sovish, filed 23rd December.

1977 which describes and claims such devices. In these devices the retaining means does not need to pass through the body of the heat-recoverable member and thus the need for moulded or extruded protuberances at the edges of the heat-recoverable sheet is obviated. In this respect the retaining means comprises a member having two sections which engage the opposed edge regions of the heat-recoverable sheet material. These sections typically comprise tines, which pass through loops in the sheet material, or are provided with slots, through which the sheet material passes. In both such embodiments the heat-recoverable sheet material may be regarded as passing around these sections and, in many cases, it is engaged by frictional forces.

A flush configuration can readily be obtained by using a buckle as the retaining means. The buckle, which may. if desired, be contoured, e.g. curved, for conformity with the surface of the substrate, or which may be deformable so that it adopts the desired curved configuration during recovery, may comprise one or more slots through which the sheet passes. In certain applications, it may be advantageous for the nature of the slots to be different, for example, the slots may be closed or open-ended. By this means, for example, it may be possible to attach the buckle to one end of the heat-recoverable sheet before it is wrapped around the substrate, thus facilitating installation.

In some embodiments of the present invention the heat-recoverable sheet material may be provided with loops on each opposed edge and the retaining means, e.g. the buckle, then preferably comprises two connected tines each of which passes through a loop to hold the sheet in the wrap-around configuration. (Of course, the loop could also be provided only at one edge and it will be appreciated that may design modifications are possible.) The loops may be formed from flat sheet material by folding, preferably followed by bonding, for example by ultrasonic welding or, in certain embodiments, by providing the heat-recoverable sheet member as a tube which becomes flattened during the.

wrap-around operation to leave two edge loops in its flattened configuration. In this respect, it will be appreciated that the term "opposed edge regions", as used herein means the opposed edge regions of the heatrecoverable sheet where they engage the retaining means and does not imply that these regions are necessarily at an end or edge of the sheet itself.

It will be appreciated that the use of a buckle will be especially appropriate when the width of the heat-recoverable sheet is small, for example where the device acts as a wrap-around tie rather than as an insulative or protective closure device. The buckle may, if desired, be coated with a plastics film in one or more parts for insulative purposes or to facilitate assembly.

Depending on the application concerned, the heat-recoverable sheet material can be made from any of the polymers known from the art to be useful for the production of heat-recoverable articles. Generally the sheet material will be of constant composition throughout; however laminates of two different polymers bonded or fused together may be used in certain instances. Amongst suitable polymers there may be mentioned, for example polyolefins, especially polyethylene, copolymers of ethylene and vinyl acetate, copolymers of ethylene and ethyl acrylate; chlorinated and fluorinated polymers, especially polyvinyl chloride, polyvinylidene fluoride and polymers incorporating units from vinylidene fluoride, hexafluoroethylene and chlorotrifluoroethylene; and rubbers such as ethylene/propylene rubber, chlorinated rubbers, e.g. Neoprene, and silicone rubbers which may be used in a blend with a crystalline or glassy polymer such as an olefin polymer. All of the above materials may, if desired, be cross-linked for example by irradiation and/or chemical means.

In certain applications, the internal surface of the wrap-around sheet material may, of course, be provided with a coating of an adhesive or a sealant such as a hot-melt adhesive or a mastic. Especially suitable hotmelt adhesives include, for example. polyamides, ethylene/vinyl acetate copolymers and terpolymers (with or without incorporated waxes) and polyesters. Such materials are described, for example, in British Patent 1,440,810 and German OS 2,709,717. Also suitable are curable adhesives which melt and flow on heating but which will not afterwards be hot-meltable. There may also be mentioned epoxy resins and conventional mastics such, for example, as those based on butyl and isobutylene rubbers modified with suitable materials known in the art. Obviously the use or otherwise of such materials and their type, if chosen, will depend upon the particular requirements in any given case.

It will be seen that the wrap-around devices used in the present invention can be formed in a simple manner and therefore that production costs can be kept very low, which is one of the main advantages provided by the present invention. Amongst other advantages there may especially be mentioned the ease of installation of the devices, which are more or less independent of manufacturing tolerances and other factors contributing to the lack of versatility of the previously proposed mechanical fastening systems for wrap-around devices. Notwithstanding the fact that the high degree of recovery of the sheet material itself allows the devices to be used with different size substrates, the buckle arrangement enables the operator to position the device accurately and tightly around any size of substrate prior to recovery.

Finally, because the buckle can itself carry the solder there is no difficulty in keeping the solder in position, which might otherwise be a problem with large sleeves.

Various embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which Figures la and lb illustrate one form of wrap-around device and its use in making an electrical connection; Figures 2a to 2d illustrate a second form of wrap-around device and its use in making an electrical connection; Figure 3 illustrates yet another form of wrap-around device suitable for use in the present invention; Figures 4a to 4d illustrate a fourth form of wrap-around device suitable for use in the present invention, and Figures 5a to 5e illustrate a similar form of wrap-around device.

Referring now to the drawings, Figures la and I b show a wrap-around device according to the present invention comprising a strip of heat-recoverable material I which is heatshrinkable in its longitudinal direction and a retaining means in the form of a thin metal buckle 2. The buckle is provided with two sets of closed slots 3 and 4 through which the heat-recoverable strip passes. It is also formed to provide a central bridge 5. As shown, an earth lead 6 is held against the buckle 2 by this bridge 5. The end of braid 6 is preferably tinned with solder before it is inserted into the buckle 2.

This wrap-around device may be used to form an earth connection to the conductive sheath 7 of a cable 8. The device is assembled with the earth lead 6 as shown, for example in Figure Ib, and is then wrapped about the sheath 7 as shown in Figure la. Heat is then applied causing the strip I to shrink longitudinally and the solder to flow and thus form the desired connection. It will be appreciated that the device is capable of adaptation to substrates of various sizes because the length of the strip I may readily be varied.

Figures 2a to 2d illustrate a somewhat similar form of device except that in this case the heat-shrinkable member is made from a heat-shrinkable tube 11 as shown in Figures 2a to 2c and that the buckle 12 is provided with two one-ended slots 13 and 14 so that tines sl5 and 16 respectively may pass into the loops formed at the edges of the flattened tube 11. The assembly may be used to make an earth connection as shown, before recovery, in Figure 2d.

In the wrap-around device shown in Figure 3, the retaining means comprises a metal clip 26 which operates on the hairpin principle in that it is provided with two parallel tines 27 and 28. However, in this case the retaining clip is additionally provided with a base portion 29 which extends beneath the tines 27 and 28 and, as shown, operates to provide a sealing flap for the completed closure.

Figures 4a to 4d show a further wrap around device according to the present invention. This comprises a longitudinally heat-shrinkable strip 31 and a metal buckle 32 which is advantageously made from thin soft copper. As can be seen the width of strip 31 is greater than that of buckle 32 as, in this embodiment the strip is designed completely to cover the electrical connection made.

For this purpose, as can be seen from Figure 4d, the arrangement is such that strip 31 overlaps itself when positioned on buckle 32. The strip comprises a longer end portion 33 provided with a tack-welded terminal loop 34 and a shorter end portion 35 provided with a tack-welded terminal loop 36.

The width of end portions 33 and 35 is less than that of buckle 32 as they are designed to pass through the closed slots 37, 38 and 39 and the open ended slot 40 of the buckle, respectively.

As shown in Figure 4c, the device may be provided assembled with loop 34 surrounding the arm 41 between slots 37 and 38 after having been passed through slot 39, the tackweld being formed in situ. Being made from thin soft copper the buckle 32 may bend to conform to a substrate, as shown in Figure 4d, and it may advantageously be coated with a thin film of a plastics material in the vicinity of open-ended slot 40 for electrical insulation purposes.

Prior to recovery, the device is assembled in the wrapped tubular configuration shown in Figure 4d with tine 42 of bracket 32 passing through loop 36 of heat-shrinkable strip 31. The edge portions of strip 31 bordering the dotted lines in Figure 4a may be adhesive coated to provide an environmental seal.

The wrap-around device shown in Figures 5a to 5e is similar to that shown in Figures 4a to 4d. The difference is that the sheet member 51 is provided with terminal tags 52 and 53 which are now provided with loops.

Because of this the buckle 54 may be provided with closed slots as shown and the device may be assembled and positioned about a substrate as illustrated in Figures Sc and 5d. The absence of the terminal loops makes the construction of the device simpler and less expensive and, in addition, means that the device can more readily accommodate various sizes of cable.

Figure 5e shows how buckle 54 may be provided with a solder preform 55 so that a soldered connection may be formed on recovery.

Attention is drawn to copending Application No. 53704/77 (Serial No. 1604440) filed 23rd December, 1977, inventor Francois Biscop (N.V. Raychem S.A.) which describes and claims wrap-around devices in which the two regions of the sheet material which are secured together by a fastening means prior to recovery are each provided with a strip of relatively rigid sheet material, for example made from metal and in which the strips, which lie generally in the plane of the sheet material, co-operate to form the fastening means or a part thereof. Some of the devices of that invention are suitable for use in the present invention.

WHAT WE CLAIM IS: 1. A method of forming an electrical connection to a substrate which comprises the steps of: (a) positioning about the substrate a heat-recoverable wrap-around device which comprises heat-recoverable sheet material and retaining means which co-operates with and engages opposed edge regions of the sheet material, the retaining means being provided with means for receiving and engaging an electrical component to connect it electrically to the substrate positioned within the wrap-around device.

2. A method as claimed in claim 1, wherein the component is an earthed component.

3. A method as claimed in claim 1 or claim 2, wherein the connection is made to a continuous substrate.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. with the earth lead 6 as shown, for example in Figure Ib, and is then wrapped about the sheath 7 as shown in Figure la. Heat is then applied causing the strip I to shrink longitudinally and the solder to flow and thus form the desired connection. It will be appreciated that the device is capable of adaptation to substrates of various sizes because the length of the strip I may readily be varied. Figures 2a to 2d illustrate a somewhat similar form of device except that in this case the heat-shrinkable member is made from a heat-shrinkable tube 11 as shown in Figures 2a to 2c and that the buckle 12 is provided with two one-ended slots 13 and 14 so that tines sl5 and 16 respectively may pass into the loops formed at the edges of the flattened tube 11. The assembly may be used to make an earth connection as shown, before recovery, in Figure 2d. In the wrap-around device shown in Figure 3, the retaining means comprises a metal clip 26 which operates on the hairpin principle in that it is provided with two parallel tines 27 and 28. However, in this case the retaining clip is additionally provided with a base portion 29 which extends beneath the tines 27 and 28 and, as shown, operates to provide a sealing flap for the completed closure. Figures 4a to 4d show a further wrap around device according to the present invention. This comprises a longitudinally heat-shrinkable strip 31 and a metal buckle 32 which is advantageously made from thin soft copper. As can be seen the width of strip 31 is greater than that of buckle 32 as, in this embodiment the strip is designed completely to cover the electrical connection made. For this purpose, as can be seen from Figure 4d, the arrangement is such that strip 31 overlaps itself when positioned on buckle 32. The strip comprises a longer end portion 33 provided with a tack-welded terminal loop 34 and a shorter end portion 35 provided with a tack-welded terminal loop 36. The width of end portions 33 and 35 is less than that of buckle 32 as they are designed to pass through the closed slots 37, 38 and 39 and the open ended slot 40 of the buckle, respectively. As shown in Figure 4c, the device may be provided assembled with loop 34 surrounding the arm 41 between slots 37 and 38 after having been passed through slot 39, the tackweld being formed in situ. Being made from thin soft copper the buckle 32 may bend to conform to a substrate, as shown in Figure 4d, and it may advantageously be coated with a thin film of a plastics material in the vicinity of open-ended slot 40 for electrical insulation purposes. Prior to recovery, the device is assembled in the wrapped tubular configuration shown in Figure 4d with tine 42 of bracket 32 passing through loop 36 of heat-shrinkable strip 31. The edge portions of strip 31 bordering the dotted lines in Figure 4a may be adhesive coated to provide an environmental seal. The wrap-around device shown in Figures 5a to 5e is similar to that shown in Figures 4a to 4d. The difference is that the sheet member 51 is provided with terminal tags 52 and 53 which are now provided with loops. Because of this the buckle 54 may be provided with closed slots as shown and the device may be assembled and positioned about a substrate as illustrated in Figures Sc and 5d. The absence of the terminal loops makes the construction of the device simpler and less expensive and, in addition, means that the device can more readily accommodate various sizes of cable. Figure 5e shows how buckle 54 may be provided with a solder preform 55 so that a soldered connection may be formed on recovery. Attention is drawn to copending Application No. 53704/77 (Serial No. 1604440) filed 23rd December, 1977, inventor Francois Biscop (N.V. Raychem S.A.) which describes and claims wrap-around devices in which the two regions of the sheet material which are secured together by a fastening means prior to recovery are each provided with a strip of relatively rigid sheet material, for example made from metal and in which the strips, which lie generally in the plane of the sheet material, co-operate to form the fastening means or a part thereof. Some of the devices of that invention are suitable for use in the present invention. WHAT WE CLAIM IS:

1. A method of forming an electrical connection to a substrate which comprises the steps of: (a) positioning about the substrate a heat-recoverable wrap-around device which comprises heat-recoverable sheet material and retaining means which co-operates with and engages opposed edge regions of the sheet material, the retaining means being provided with means for receiving and engaging an electrical component to connect it electrically to the substrate positioned within the wrap-around device.

4. A method as claimed in any one of

claims 1 to 3, wherein the substrate is the conductive sheath of an electric cable.

5. A method as claimed in any one of claims 1 to 4, wherein the retaining means is provided with a solder preform.

6. A method as claimed in any one of claims 1 to 5, wherein the retaining means is such that the wrap around device lies substantially flush with the substrate after recovery.

7. A method as claimed in any one of claims 1 to 6, wherein the heat-recoverable sheet material is held in the retaining means by frictional forces.

8. A method as claimed in any one of claims 1 to 7, wherein the retaining means is provided with two sections which engage the opposed edge portions of the heat-recoverable sheet material.

9. A method as claimed in claim 8, wherein said sections comprise tines which pass through loops in said heat-recoverable sheet material.

10. A method as claimed in claim 9, wherein said loops are formed at the edges of said heat-recoverable sheet material by folding back.

11. A method as claimed in claim 10, wherein the loop is secured by bonding.

12. A method as claimed in claim 9, wherein said loops are formed by flattening a heat-recoverable tube to form a dual-walled sheet.

13. A method as claimed in any one of claims 8 to 12, wherein said sections comprise slots through which the heat-recoverable sheet material passes.

14. A method as claimed in any one of claims 1 to 13, wherein the heat-recoverable sheet material is provided as a strip the length of which can be altered according to the girth of the substrate.

15. A method as claimed in any one of claims 1 to 14, wherein the retaining means is a buckle.

16. A method as claimed in claim 15, wherein the buckle is shaped to conform with the substrate.

17. A method as claimed in claim 15, wherein the buckle is capable of deforming to conform to the substrate.

18. A method as claimed in any one of claims 15 to 17, wherein the buckle is provided with a bridge member under which the electrical component may pass so as to be held against the main body of the buckle by resilient and/or frictional forces.

19. A method as claimed in any one of claims 15 to 18, wherein the width of the heat-recoverable sheet material is greater than that of the buckle and the arrangement is such that the heat-recoverable sheet material passes over the buckle so as to insulate it after recovery.

20. A method as claimed in any one of claims 1 to 19, wherein the retaining means is made from an electrically conductive metal.

21. A method as claimed in claim 20, wherein said metal is copper.

22. A method as claimed in any one of claims 1 to 21, wherein one or more parts of the retaining means is coated with a plastics material.

23. A method as claimed in any one of claims 1 to 22, wherein the retaining means is attached to one end of the buckle prior to assembly of the wrap-around device for recovery.

24. A method as claimed in claim 1, substantially as described herein with reference to, and as illustrated in, the drawings.

25. An electrical connection whenever made by a method as claimed in any one of claims 1 to 24.

26. A heat-recoverable wrap-around device which comprises heat-recoverable sheet material and retaining means which cooperates with and engages opposed edge regions of the sheet material, the retaining means being provided with means for receiving and engaging an electrical component so as to connect it electrically to a substrate positioned within the wrap-around device.

27. A heat-recoverable wrap-around device as claimed in claim 26, wherein the retaining means is provided with a solder preform.

28. A heat-recoverable wrap-around device as claimed in claim 26 or claim 27, wherein the heat-recoverable sheet material is held in the retaining means by frictional forces.

29. A heat-recoverable wrap-around device as claimed in claims 26 to 28, wherein the retaining means is provided with two sections which engage the opposed edge portions of the heat-recoverable sheet material.

30. A heat-recoverable wrap-around device as claimed in claim 29, wherein said sections comprise tines which pass through loops in said heat-recoverable sheet material.

31. A heat-recoverable wrap-around device as claimed in claim 30, wherein said loops are formed ar the edges of said heatrecoverable sheet material by folding back.

32. A heat-recoverable wrap-around device as claimed in claim 31, wherein the loop is secured by bonding.

33. A heat-recoverable wrap-around device as claimed in claim 30, wherein said loops are formed by flattening a heat-recoverable tube to form a dual-walled street.

34. A heat-recoverable wrap-around device as claimed in claims 29 to 33 wherein said sections comprise slots through which the heat-recoverable sheet material passes.

35. A heat-recoverable wrap-around device as claimed in claims 26 to 34, wherein the heat-recoverable sheet material is provided as a strip the length of which can be altered according to the girth of the substrate.

36. A heat-recoverable wrap-around device as claimed in claims 26 to 35, wherein the retaining means is a buckle.

37. A heat-recoverable wrap-around device as claimed in claim 36, wherein the buckle is capable of deforming to conform to the substrate.

38. A heat-recoverable wrap-around device as claimed in claim 36 or claim 37, wherein the buckle is provided with a bridge member under which the electrical component may pass so as to be held against the main body of the buckle by resilient and/or frictional forces.

39. A heat-recoverable wrap-around device as claimed in claims 36 to 38, wherein the width of the heat-recoverable sheet material is greater than that of the buckle and the arrangement is such that the heat-recoverable sheet material passes over the buckle so as to insulate it after recovery.

40. A heat-recoverable wrap-around device as claimed in claims 26 to 39, wherein the retaining means is made from an electrically conductive metal.

41. A heat-recoverable wrap-around device as claimed in claim 40, wherein said metal is copper.

42. A heat-recoverable wrap-around device as claimed in claims 26 to 41, wherein one or more parts of the retaining means is coated with a plastics material.