GB2108779A - Sheathing of conduit joints - Google Patents

Abstract

A conduit joint, such as a telephone cable splice (2), includes a box with two similar halves (12, 13), each having an inner and outer wall (16, 18), the edges of the inner walls (16) mating together to enclose the joint in an air space and the outer walls (18) similarly co-operating to form, with the inner walls, a closed loop (17) around the joint with the conduits passing through recesses (22) in the walls. These recesses have a local mastic seal (23) and the entire loop is filled with another sealing compound to complete the joint. In another form (Fig. 1, not shown) a shell (3) on each side of the joint surrounds the conduit and is sealed at its end by a mastic (7, 8) and then filled with a sealing compound (6). The shells may have extensions which meet over the joint, or there may be an intermediate split tubular sleeve (10) spanning them. A heat shrinkable wrapping (11) is applied over the adjacent ends of the shells and any intermediate sleeve to close off the air space in which the joint lies. <IMAGE>

Description

SPECIFICATION Improvements relating to sheathing of conduit joints This invention relates to the sheathing of conduit joints, and although primarily intended for the covering and insulation of telephone cable splices, it does have many other applications.

One quite common method employs a split tube which encases the joint and a heat shrinkable sleeve over that tube and extending beyond each end. A sealing composition is applied to the inside of each end of the sleeve, which is then heated to constrict around the tube and the cable. This has a number of disadvantages, one of the main ones being that a flame has to be played over the projecting ends of the sleeve, and consequently perilously close to the cable itself. This can cause damage, and although attempts have been made to reduce it by covering the cable with foil and using thermochromic paint to indicate critical temperatures, this is inconvenient and unsatisfactory. Also, joints and cables come in many numbers and sizes, and to cater for these a large number of different sized tubes and sleeves have to be stocked.

It is the aim of this invention to provide a joint sheathing assembly which can readily be adapted to many different sizes of conduit, and which avoids the application of flame heat almost directly onto the conduit itself.

According to the present invention there is provided a sheathed conduit joint, such as a telephone cable splice, comprising an enclosure fitted over the joint after completion to form an air space around the joint and, at each end, further spaces through which the conduits pass to the exterior, any clearances between each conduit and the enclosure as it passes in and out of the associated further spaces being closed by a first sealant and said further spaces being subsequently filled by a second sealant.

In one preferred form, the enclosure is a split box-like member which can be closed over the joint. The air and further spaces may be formed by substantially mirror image recesses in opposed halves of the box-like member, and the further spaces may be united in a closed loop space which surrounds the air space, the second sealant filling of this loop sealing said air space. The boxlike member will conveniently be of moulded plastics material, each half having partitions defining said recesses, and the tops of the partitions of opposed halves interengaging. When the box-like member is closed. The halves will preferably be hinged together.

In another embodiment the enclosure includes two shells fitted over the respective conduits at opposite ends of the joints, the further spaces being within these shells, and a wrapper surrounding the joint to complete said air space, the wrapper overlapping and being sealed to each shell but not the conduits.

The wrapper may be heat shrinkable, or it may be cold-applied, for example in the form of a tape.

In this case, a primer would probably have to be coated over the surfaces to be wrapped.

The sealing means preferably comprise two generally frusto-conical shells, open at apex and base to embrace the conduit and which may be elliptical rather than circular in cross-section.

Each base end, which is arranged nearest the joint to be overlapped by the wrapper, may terminate in a cylindrical portion, and conveniently each shell is made in two mirror image parts which split in a plane containing the shell axis. However, they can each be made in more parts, or as a single member with a single split line and flexible enough to be sprung apart to pass laterally over the conduit. Even a single split line may not be necessary if it could be arranged to pass the shell over the conduit before the joint is made, or if it could readily be severed by a knife, parted, fitted laterally over the conduit and brought together again. The apex end can be cut off to varying extents to accommodate different sizes and numbers of cables.

When these shells are in place they can be filled with a sealing compound, and if they are not in base-to-base abutment they will then be mutualiy spanned by a wrapper support. This may be a split tube, but preferably it is simply stiff sheet material cut to the desired dimensions and wrapped around the joint. This avoids having tubes of various diameters and lengths to cater for different jobs. The heat shrinkable sleeve (if one is used) will have a closing mechanism so that it can be wrapped around the tubular support and closed before heat is applied.

This wrapper support is, however, only necessary when there are long splices which cannot be bridged by two base-to-base shells; and to make it infrequently necessary, the shells may have extended cylindrical portions likely to span most splices. These portions could be shortened by cutting where possible.

In a further variation, there could be longitudinally splittable complete shells, of generally cigar shape. These would embrace most short splices, and if a longer one had to be sealed such a shell could be cut across into halves and lengthened by use of a wrapper.

For a better understanding of the invention, some embodiments will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a longitudinal section of a telephone cable joint assembly with a sheathing.

Figure 2 is a cross-section on the line Il-Il of Figure 1.

Figure 3 is a longitudinal section of another sheathed joint.

Figure 4 is a section on the line IV-lV of Figure 3, and Figure 5 is an end view of the sheathed joint of Figure 3.

In Figures 1 and 2 a pair of cables 1 are joined by respective splices 2. On each side of the splices the cables are surrounded by generally frusto-conical open-ended shells of elliptical cross-section. The smaller end has its rim just surrounding the cables 1. If the cables were thicker, or if there were more of them, the shell 3 would be cut off at an appropriate point to create a larger opening just sufficient to accommodate such cables. The larger end of the shell terminates in a short cylindrical portion 4, formed with a hole 5 into which a polymeric sealing material 6 can be poured. This is confined before setting within the shell by temporary seals 7 and 8 at the smaller and larger ends respectively, formed by a putty-like compound. The main sealing material 6 is conveniently polyurethane.

Each shell 3 is made in two mirror image parts which divide at split lines 9, and they may be formed to clip together or just abut. They are preferably made of high density polyethylene or a plastics material of similar properties which can fairly easily be cut for the reason mentioned above. The hole 5 may be formed by a knock-out disc.

When the shells are in place and filled with the sealing material 6, a stiff tubular support 10 is wound around the splices just to overlap onto the cylindrical portions 4. This support may be cut from a large sheet of material such as polypropylene to the exact dimensions required on site. A heat shrinkable sleeve 11 is then wrapped around the assembly, covering this support and extending over the pouring holes 5 of each shell. The sleeve is completed by a closing mechanism of known type. Heat can then be applied to shrink it around the support 10 and the larger ends of the shells 3 without flame heat coming close to the conduit cables 1.

If the joint has to be re-opened for repairs, much of this sheathing assembly may remain intact. The sleeve 11 would have to be cut off and later replaced, but the support 10 might well be re-usable, and the shells 3 could in many cases remain in place.

Referring to Figures 3 to 5, this version employs a box-like structure to encase the joint.

The cables and the joint are referenced as before.

The box consists of two almost matching halves 12 and 13. They are double walled, each inner wall 14 consisting of a tray-like structure in moulded plastics. The "tray" has a central rectangular recess 1 5 surrounded and defined by an inner partition 1 6. Around this there is a recess 17, still following the rectangular shape, and its outer limit is defined by a further partition 1 8. The tops of the partitions 1 6 and 18 are stepped, the steps on the half 12 being complementary to those on the half 13 so that there is an interengagement as shown in Figure 4. The inner walls 14 are sheathed externally by outer walls 19, which are bonded to the perimeter 20. Along one side of the box, the outer walls 19 are extended and joined by a flexible U-section web 21, as shown in Figure 5. This is in effect a hinge.

In one half (13 in this example) the partitions 1 6 and 1 8 have cut-outs 22 at the centre of each of their shorter sides. These are to accommodate the conduit as shown in Figure 5. It would be possible to have cut-outs in both halves, and this might be necessary if the conduit 1 was large, or if more than one joint was to be accommodated in the box.

When the joint 2 is made, the half 13 can be laid underneath it so that the joint is central of the recess 1 5 with the conduits 1 resting in the cutouts 22. There is bound to be some clearance at the partitions 16 and 18 and as a first seal a mastic is applied locally as indicated at 23. The box is then shut by folding the other half 12 so that the partition rims interengage, trapping the conduits in the cut-outs. The mastic will seal against the rims that are brought down against it.

Another mastic or sealing compound will then be injected into the closed loop space formed by the recess 1 7. This will permeate throughout the loop, firmly sealing both inner and outer partitions and closing off in air-tight manner the space in which the joint 2 lies.

Various sealing materials or compounds are possible for both the primary and secondary sealing jobs. Among the suitable ones are single or two parts urethanes (10096 solids tar extended frames, low or high density) and epoxies (100% solids tar extended).

Claims (15)

Claims

1. A sheathed conduit joint, such as a telephone cable splice, comprising an enclosure fitted over the joint after completion to form an air space around the joint and, at each end, further spaces through which the conduits pass to the exterior, any clearances between each conduit and the enclosure as it passes in and out of the associated further spaces being closed by a first sealant and said further spaces being subsequently filled by a second sealant.

2. A joint as claimed in claim 1, wherein the enclosure is a split box-like member which can be closed over the joint.

3. Ajoint as claimed in claim 2, wherein the air and further spaces are formed by substantially mirror image recesses in opposed halves of the box-like member.

4. A joint as claimed in claim 3, wherein the further spaces are united in a closed loop space which surrounds the air space, the second sealant filling of this loop sealing said air space.

5. A joint as claimed in claim 3 or 4, wherein the box-like member is of moulded plastics material, each half having partitions defining said recesses and the tops of the partitions of opposed halves interengaging when the box-like member is closed.

6. A joint as claimed in claim 3, 4 or 5, wherein the halves are hinged together.

7. A joint as claimed in claim 1, wherein the enclosure includes two shells fitted over the respective conduits at opposite ends of the joint, the further spaces being within these shells, and a wrapper surrounding the joint to complete said air space, the wrapper overlapping and being sealed to each shell but not the conduits.

8. A joint as claimed in claim 7, wherein the wrapper is heat shrinkable.

9. A joint as claimed in claim 8, wherein the wrapper has a closure mechanism, whereby it can be wrapped around and closed into generally tubular form before heat is applied.

10. A joint as claimed in claim 7, 8 or 9, wherein the shells are generally frusto-conical, open at apex and base to embrace the conduit, and with the base adjacent the joint.

11. A joint as claimed in claim 10, wherein each base terminates in a coaxial cylindrical extension.

12. A joint as claimed in any one of claims 7 to 11, wherein each shell is made in two or more parts for assembly around the conduit.

13. A joint as claimed in any one of claims 7 to 1 wherein each shell has a split line and is resilient and flexible enough to be sprung apart and passed laterally over the conduit.

14. A joint as claimed in any one of claims 7 to 13, wherein a tubular support for the wrapper encircles the joint between the shells.

15. A sheathed conduit joint substantially as hereinbefore described with reference to Figures 1 and 2 or Figures 3 to 5 of the accompanying drawings.