GB2113019A - Electric cable junction sealing - Google Patents

Abstract

A sleeve 15 for sealing a junction between electric cables includes a tubular sheet 16 composed of a radially inwardly heat-shrinkable outer layer and a fusable inner layer fused to the outer layer. Longitudinal marginal portions of the tubular sheet 16 are directed radially outwardly to provide a pair of opposed ridges 18, for mating together at their inner sides. Each ridge 18 has a projection 19 on an outer side thereof in spaced relation to the outer peripheral surface of the tubular sheet 16 to provide a recess 20 between the projection 19 and the outer peripheral surface. A pair of elongated receptive members 22 are fixedly secured to the recesses 20, respectively. Each receptive member 22 is plastically deformable longitudinally. A clip 30 holds ridges together so that, on application of heat, the ridges fuse together and the sheet 16 shrinks. <IMAGE>

Description

SPECIFICATION Electric cable junction sealing This invention relates to a sleeve for and method of sealing a junction between electric cables such as those having a sheath of a plastics material.

It is known in the art to cover and seal a junction of cables by the use of a heat shrinkable sheet. A sealing assembly 100 of this general type shown in FIG. 1 is assembled in the following manner: A pair of end closure members 102 are attached on the respective cables 101 adjacent to a junction therebetween, each end closure member having an inner cylindrical portion (not shown) and an outer tapered portion 102a. A split tube (not shown) is attached to the end closure members 102 in surrounding relation to the cable junction. Then, a heat shrinkable sheet 103 of a generally tubular shape is wrapped around the split tube with its longitudinal marginal portions 103a. The mated marginal portions are gripped by a pair of rigid straight bars 104 which are clamped by a plurality of clips 105.Thus, the marginal portions 103a of the sheet 103 are held in uniform and intimate contact with each other throughout the entire length thereof. Then, the heat shrinkable sheet 103 is heated over the entire surface thereof by a suitable heating means such as a torch lamp, so that the sheet 103 is shrunk radially inwardly to be tightly fitted over the split tube and the inner cylindrical portions of the end closure members 102, the sheet 103 being fusingly bonded at its inner surface only to the inner cylindrical portions of the end closure members. The mated marginal portions 103a are also fusingly bonded together at their inner surfaces. This conventional sealing method is advantageous in that it has a good operating efficiency and that the fused marginal portions 103a of the heat shrinkable sheet 103 have an increased bonding strength.However, since the mated marginal portions 103a are gripped by the straight rigid bars 104, the tubular sheet 103 has a uniform circular cross-section throughout its entire length after it is radially inwardly shrunk upon application of heat thereto. For this reason, the pair of end closure members 102 having the outer tapered portions 102a are used to completely seal the junction between the cables 101. Each end closure member 102 is fusingly bonded to the cable 101 before the split tube is installed.

In order to overcome this difficulty, it has been proposed in the art to use a fastener 106 of a Cshaped cross-section which is fitted on the mated marginal portions 107a of a heat shrinkable sheet 107 to hold them together, as shown in FIGS. 2A and 2B. The C-shaped fastener 106 has a plurality of notches 108 formed through opposite sides thereof and spaced along the length thereof so that the fastener 106 is rendered flexible. Upon the application of heat to the split tubular sheet 107, the tubular sheet is radially inwardly shrunk to tightly fit over the junction between the cables.

At this time, the flexible fastener 106 is deformed to follow the contour of tapered end portions of the cable junction. Thus, the heat shrinkable sheet 107 can enclose the cable junction entirely without the need for the end closure members as is the case with the above-mentioned conventional sealing method. However, since the marginal portions 107 of the heat shrinkable sheet 107 are held in contact with each other merely by the flexible fastener 106, the mated marginal portions are not sufficiently held together so that the bonding strength of the fused marginal portions is not adequate.

It is therefore an object of this invention to provide a longitudinally split sleeve for sealing a junction between electric cables in which longitudinal marginal portions can be easily held together firmly and subsequently be bonded together quite positively by a heat treatment, the sleeve being able to be radially inwardly shrunk by the heat treatment to completely cover and seal an inner support structure having tapered portions at its opposite ends.

According to the present invention, there is provided a sleeve for sealing a junction between electric cables which comprises a generally tubular sheet composed of a radially inwardly heat-shrinkable outer layer and fusable inner layer fused to the outer layer, the tubular sheet being longitudinally split, the longitudinal marginal portions of the tubular sheet being directed radially outwardly to provide a pair of opposed ridges, each ridge having a projection on an outer side thereof in spaced relation to the outer peripheral surface of the tubular sheet to provide a recess between the projection and the outer peripheral surface, the pair of ridges being adapted to be mated together at their inner sides; and a pair of elongated receptive members fixedly secured to the recesses, each receptive member being plastically deformable longitudinally.

The invention will now be described by way of example with reference to the accompanying drawings in which:~ FIG. 1 is a perspective view of a conventional sealing assembly; FIG. 2A is a fragmentary cross-sectional view of a conventional sealing sleeve; FIG. 2B is a cross-sectional view taken along the line B-B of FIG. 2A; FIG. 3 is a cross-sectional view of a sealing assembly provided in accordance with the present invention; FIG. 4 is a cross-sectional view of a sleeve employed in the sealing assembly of FIG. 3; FIG. 5 is a fragmentary perspective view of the sleeve; FIG. 6A is a fragmentary plan view of a receptive member of the sleeve; FIG. 6B is a cross-sectional view of the receptive member taken along the line C-C of FIG. 6A;; FIG. 7 is a cross-sectional view of the sleeve, showing a fastening means attached thereto; FIG. 8 is a fragmentary perspective view of the sleeve as shown in its heat-shrunk configuration; and FIG. 9 is a cross-sectional view of a modified sealing assembly.

FIG. 3 shows a sealing assembly 10 for covering and sealing a junction or splice 11 between cables 12. The sealing assembly 10 comprises an inner split tube 13 consisting of two half cylinders 13a and surrounding the cable junction 11, a pair of hollow support rings 14 attached to the opposite ends of the inner split tube 13, respectively, and a sleeve 15 wrapped around the inner split tube 13, the support rings 14 and those portions of the cables 12 adjacent to the support rings 14. The sleeve 15 is a flat sheet and is wrapped around these members. The inner split tube 13 is made of metal such as aluminum, and the support rings 14 are made of rubber or plastics material. Each of the support rings 14 has a cylindrical portion 14a held against the split tube 13 and a tapered portion 14b engaging the cable 12 at its outer end.The support ring 14 has an axial slit (not shown) extending along the entire length thereof to interrupt the periphery thereof so that the support ring 14 can be attached onto the cable 12. Alternatively, the support ring 14 may be of the axially split type consisting of two halves.

As best shown in FIG. 4, the sleeve 15 comprises a generally tubular sheet 16 composed of a heat shrinkable outer layer and fusable inner layer fused to the outer layer, the inner layer being made of uncrosslinked and unstretched polyethylene or polyvinyl chloride while the outer layer is made of crosslinked and stretched polyethylene. The longitudinal marginal portions of the tubular sheet 1 6 are directed radially outwardly to provide a pair of opposed ridges 18.

The opposed inner flat surfaces of the two ridges 18 are adapted to be mated together as later described.

Each of the ridges 18 has an integral projection 19 formed on an outer side thereof and extending along the entire length thereof (FIG. 5), the projection 19 being disposed in spaced relation to the outer peripheral surface of the tubular sheet 16 to provide a recess 20 therebetween. The outer end of the projection 1 9 lies flush with the outer end of the ridge 1 8.

A pair of identical receptive members 22 are attached to the recesses 20, respectively. Each receptive member 22 comprises a relatively rigid strip of heat resistant metal (FIG. 6A) which is bent along its length into a generally V-shaped cross-section as best shown in FIG. 6B. The Vshaped receptive member 22 is defined by a pair of upper and lower arms 23 and 24 and a connective curved portion 25 interconnecting the upper and lower arms 23 and 24.A plurality of notches 26 are formed through the upper arm 23 of each receptive member 22 and uniformly spaced along the length thereof, each notch 26 extending into the curve portion 25 as shown in FIG. 6B. For fixing each receptive member 22 relative to the tubular sheet 16, the receptive member 22 is first placed on the tubular sheet 16 with the curved portion 25 received in the recess 20 and with the lower arm 24 mated with the outer peripheral surface of the tubular sheet 1 6. Then, an adhesive tape 28 of a heat resistant nature such as an adhesive glass tape is bonded to the lower arm 24 and that portion of the outer peripheral surface of the tubular sheet 1 6 adjacent to the lower arm 24, thereby fixing the receptive member 22 relative to the tubular sheet 16.

For assembling the sealing assembly 10 to enclose and seal the junction 11 between the cables 12, the pair of support rings 14 are first attached onto the respective cables 12 adjacent to the junction 11. Then, the inner split tube 13 is attached to the support rings 14 in surrounding relation to the junction 11, and a suitable adhesive tape (not shown) or the like is wound around the inner split tube 13 to positively hold its halves together. Then, the sleeve 15 is wrapped around the inner split tube 13 and the pair of support rings 14, the opposite ends of the sleeve 15 extending by a predetermined distance beyond the tapered portions 14b of the support rings 1 4, respectively.Then, as shown in FIG. 7, a plurality of clips 30 are attached to the two receptive members 22 to bring the opposed inner flat surfaces of the two ridges 18 into intimate contact with each other, two jaws 30a of each clip 30 being received in the curved portions 25 of the two receptive members 22, respectively. Then, the sleeve 15 is subjected to a heat treatment over the entire surface thereof by the use of a torch lamp, so that the sleeve 15 is shrunk radially inwardly to tightly fit on the inner split tube 13, the support ring 14 and the portions of the cables 12 adjacent to the support rings, the inner surface of the sleeve 15 being fused and bonded to the support rings 14 and the portions of the cables adjacent thereto. The inner surface of the sleeve 1 5 is not fused to the split tube 13 of metal.The mated inner surfaces of the two ridges 18 are also fusingly bonded together. During the heat treatment, the sleeve 1 5 is not axially contracted.

Also, during the heat treatment, the sleeve 15 is subjected to a plastic deformation to follow the contour of the tapered portions 14b of the two support rings 14, as shown in FIG. 8. At this time, the upper arm 23 of each receptive member 22 is readily plastically deformed due to the provision of the notches 26. Since the clips 30 are positively engaged with the curved portions 25 of the receptive members 22 during the deformation of the upper arms 23, the mated inner surfaces of two ridges 18 are always held in intimate contact by the force of the clips. Therefore, particularly, the mated inner surfaces of the two ridges 1 8 are quite firmly bonded together upon application of heat to the sleeve 1 5.

FIG. 9 shows a modified sealing assembly 1 Oa which differs from the sealing assembly 10 of FIG. 3 only in that an inner support tube 32 replaces the inner split tube 13 and the pair of support rings 14. The inner support tube 32 has a major cylindrical portion 33 and a pair of tapered portions 34 extending outwardly from the opposite ends of the major cylindrical portion 33.

The inner support tube 32 comprises a rectangular laminated sheet consisting of an intermediate paper layer and a pair of polyethylene layers bonded to the opposite surfaces of the intermediate layer. The rectangular laminated sheet has a plurality of slits (not shown) formed in the opposite end portions thereof and extending longitudinally. The laminated sheet is wrapped around the cable junction 1 1 in spaced relation thereto, with the slit end portions engaging the respective cables 12 and 12 at their outer ends to form the tapered portions 34. The inner support tube 32 so formed is retained in its final configuration by means of an adhesive tape or the like. The sleeve 15 is applied to the inner support tube 32 in the same manner as described above for the sealing assembly 10 of FIG. 3.

As described above, since the sleeve 15 has the receptive members 22 and 22, the ridges 18 are easily and firmly held together by the clips 30. As a result, upon application of heat to the sleeve 15, the ridges 18 are fusingly bonded together quite firmly throughout the entire length thereof.

While the sleeve according to the present invention has been specifically shown and described herein, the invention itself is not to be restricted by the exact showing of the drawings or the description thereof. For example, although the notches 26 are spaced uniformly along the entire length of the upper arm 23 of each receptive member 22, the notches may not be provided at regions where the clips 30 are adapted to be attached. Also, although the receptive member 22 has a generally V-shaped cross-section, it may have an L-shaped cross-section or a U-shaped cross-section. Further, the receptive members 22 may be bonded to the sleeve 15 by a suitable adhesive instead of the adhesive tapes 28.

Claims (7)

1. A sleeve for sealing a junction between electric cable which comprises: (a) a generally tubular sheet composed of a radially inwardly heat-shrinkable outer layer and a fusable inner layer fused to the outer layer, said tubular sheet being longitudinally split, the longitudinal marginal portions of said tubular sheet being directed radially outwardly to provide a pair of opposed ridges, said ridges being adapted to be mated together at their inner sides, and each ridge having a projection on an outer side thereof in spaced relation to the outer peripheral surface of said tubular sheet to provide a recess between said projection and said peripheral surface; and (b) a pair of elongated receptive members fixedly secured to said recesses, respectively, each receptive member being plastically deformable longitudinally.

2. A sleeve according to claim 1, in which said receptive member comprises a strip which is bent along its length into a generally V-shaped crosssection, said receptive member being defined by a pair of upper and lower arms and a connective curved portion interconnecting said upper and lower arms, a plurality of notches being formed through said upper arm and spaced along the length thereof, said notches extending into said curved portion, said curved portion being received in said recess, and said lower arm being fixedly secured to the outer peripheral surface of said tubular sheet.

3. A sleeve according to claim 1 or 2, in which said respective member is made of heat resistant and relatively flexible metal.

4. A method of sealing a junction between electric cables which comprises the steps of: (a) placing an inner support structure over the junction to enclose it, said support structure having tapered opposite end portions; (b) wrapping a sleeve around said support structure with opposite ends thereof extending by a predetermined distance beyond the opposite ends of said support member, said sleeve comprising a flat sheet composed of heatshrinkable outer layer and a fusable inner layer fused to the outer layer, said sheet having a pair of ridges formed on one surface thereof and extending along the longitudinal edges, each of said ridges having a projection formed on one surface thereof in spaced relation to the one surface of said sheet to provide a recess between said projection and the one surface of said sheet, said sleeve comprising a pair of elongated receptive members fixedly secured to said recesses, respectively, each receptive member being plastically deformable longitudinally; (c) bringing the other surfaces of said two ridges into contact with each other and detachably attaching a plurality of fastening members to said receptive members to firmly hold said the other surfaces together; and (d) applying heat over the entire surface of said sleeve so that said sleeve is radially inwardly shrunk to be tightly fitted over said support structure and those portions of the cables adjacent to said support structure, said sleeve being fusingly bonded at its inner surface to said tapered end portions and those portions of the cables adjacent thereto, the other surfaces of said two ridges being fusingly bonded together, and said receptive members being plastically deformed to follow the contour of said tapered end portions; and (e) removing said fastening members and said receptive members.

5. A sleeve for sealing a junction between electric cables substantially as hereinbefore described with reference to figures 3 to 8 of the accompanying drawings.

6. A sleeve for sealing a junction between electric cables substantially as hereinbefore described with reference to figures 3 to 8 when modified according to figure 9 of the accompanying drawings.

7. A method of sealing a junction between electric cables substantially as hereinbefore described with reference to figures 3 to 9 of the accompanying drawings.