GB2085538A - Tubular fitting for an electric cable or a pipeline - Google Patents

Abstract

A heat shrinkable fitting for a cable or pipe comprises two thickened edge portions 9, 10 provided with projections 11 and recesses 12. The projections have one or more passages 6 (7, 8 Fig. 3 not shown) running in the longitudinal direction and the projections and recesses of the two thickened portions can be so fitted together, when the fitting (3) is closed about the cable or pipe, that the passages are aligned to receive a wire to secure the edge portions together. The fitting may be formed by extruding tubing of a crosslinkable material, the extrudate having a thickened portion 5 extending in the longitudinal direction and having at least one passage 6, crosslinking the tubing, cutting off a section of required length, expanding the section while heated, causing or allowed to cool the section in its expanded state, and parting the cooled section, in the thickened portion 5, along a meandering line symmetrical with respect to the at least one passage 6. <IMAGE>

Description

SPECIFICATION Tubular fitting for an electric cable or a pipeline, and process for its manufacture The invention relates to a tubular fitting for an electric cable or a pipeline, this fitting being of a kind which is composed of an insulating material which shrinks under the action of heat, and has a parting running from one end to the other, the longitudinal edge portions beside this parting being thickened portions which (in use of the fitting) permit secure closure of the fitting by means of at least one closure element. The invention also includes a process for the manufacture of the fittings.

The fitting of the invention include, for example, connecting joints, terminations and also covers for junctions between various components. In particular, however, the fitting is meant to be useful as a connecting joint for electric cables. If a junction is required between two very long cables, and a closed tubular fitting is employed, this closed fitting ought first to be pushed over one of the cables, but this prior pushing-over can easily be forgotten by a fitter. Moreover, the fittings of the prior-art closed type can only be used on original assembly; they cannot be used after any repair work or switching-round work which may have been carried out.

A non-closed tubular fitting as first mentioned herein, composed of a shrinkable insulating material, is known from German Patent Specification 1,525,825. The closure element used here is a metal rail which is pushed over projections which protrude outwards as extensions of the fitting and extend in the longitudinal direction of the fitting. To manufacture such a fitting, tubing which has radially inward-pointing projections is first extruded from a crosslinkable material, and is crosslinked. A section having a length equivalent to the length of the required fitting is cut off from the tubing, expanded, and cut open with a longitudinal cut between the projections. When actually fitted, the fitting thus obtained has to be turned inside out, so that the projections protrude outwards.This makes application of the fitting more difficult, since the relatively stiff material of the latter must be shaped into a tubular configuration which is the opposite of its bent form. Since, as a result of this, the fitting is always tending to open up, along its parting, and since the metal rail needs to be seated very firmly on the projections, the danger can easily arise that, when the metal rail is pushed on, the projections of the fitting will be notched by the rail, so that the projections can tear when the fitting is subsequently shrunk on to the junction; this would of course tender the fitting useless. Since, moreover, the metal rail has to remain on the fitting even after shrinking, the result is a quite considerable expansion of the latter on one side, which can often be troublesome.

It is an object of the invention to provide a tubular fitting for an electric cable or a pipeline, which fitting is easy to manufacture and easy to apply, and does not cause any troublesome increase in dimensions at a junction.

According to the present invention, we provide a tubular fitting of the kind first mentioned herein which is characterised in that: the two thickened portions are provided with projections and recesses, which are mutually offset in the longitudinal direction, their arrangement being such that the projections of one of the two thickened portions fit into the recesses of the other of the two thickened portions; the projections have closure-element-receiving tunnel-like passages running in the longitudinal direction; and the projections of the two thickened portions can be so fitted together, when the fitting is closed, that the passages are aligned.

The invention also includes a process for the manufacture of a fitting as just specified, characterised in that: tubing is extruded from a crosslinkable material, the extrudate having a thickened portion extending in the longitudinal direction and having at least one tunnel-like passage; the tubing is crosslinked; a section having a length equivalent to the length of the required fitting is cut from the crosslinked tubing; this section is expanded while being heated, and is caused or allowed to cool in its expanded state; and the cooled section is parted, in the thickened portion, along a meandering line whose meanders are symmetrical with respect to the at least one passage.

It is an advantage of a fitting according to the invention that the closure element is not externally engaged on projections but is introduced into the passages mentioned above. Therefore, the closure element does not radially protrude from the fittings, and the dimensions of the cables or pipelines which are being joined or repaired are only insignificantly enlarged at the point of application of the fitting.

Another advantage is that, since the thickened portions do not need to protrude from the fitting, the projections can simply project substantially in a circumferential direction of the fitting.

On application, moreover, the fitting is placed around a junction or a cable or a pipeline bent in the same sense of curvature in which it is already bent following its manufacture. Thus the present construction makes it particularly easy to bring the projections of the two thickened portions together, and to insert the closure element(s).

A fitting according to the invention can be used as a connecting device for a plurality of cables or a plurality of pipelines. For this purpose, there may be provided additional thickened portions which protrude laterally on the outside of the fitting, extend in the longitudinal direction, and are provided with fixing-element-receiving tunnel-like passages. Into the latter, fixing elements can be inserted, on the outside of the fitting, so that the lumen of a fitting can be subdivided by one or more constrictions, e.g. subdivided into two openings which are to receive two cables or pipelines. The closing of the fitting is unaffected by this optional feature.

The invention is illustrated in the accompanying diagrammatic drawings. For simplicity, only the joining of two cables is considered here. Pipelines can be joined in an analogous manner.

In the accompanying drawings: Figure 1 is a fragmentary side view of a junction of two cables, using a fitting according to the invention, Figures 2 and 3 are respective end views of fittings according to the invention of two different designs, Figure 4 is a detail view showing, on an enlarged scale, the region around the parting of a fitting according to the invention, and Figures 5 to 7 are end views of a fitting according to the invention which can be used for two cables, at different stages in its preparation and application.

In Figure 1 , two electric cables which are jointed together in a suitable manner are shown at 1 and 2. A fitting 3 according to the invention, composed of an insulating material which shrinks under the action of heat, has been laid around the junction and securely shrunk, on both sides, on to the outer sheaths of the cables 1 and 2. The fitting is a divided fitting with a parting 4. The parting lies along a meandering line in the case shown. The manner in which the present fitting can be laid around a junction, or around a repair point, in the run of a cable, will be apparent from Fig. 1.

A fitting 3 according to the invention can be manufactured for example as follows.

Tubing of a serviceable crosslinkable plastics material, e.g. a polyethylene composition, is extruded and is thereafter crosslinked. This tubing can be wound up on a drum, or it can be divided immediately into sections of the requisite length, i.e. sections having an axial length equivalent to the length of the required fitting 3. After the cutting off of such a section, the latter is expanded (in diameter) and receives a simultaneous supply of heat; it is cooled down in this expanded state.

The new dimensions are frozen in by the cooling down, and more specifically it may be said that a "memory" is impressed on the fitting so that it will assume its original smaller dimensions again under renewed supply of heat.

The tubing from which the fitting 3 is obtained is so extruded that, around one portion of its periphery, it has a thickened portion 5, as shown in Figures 2 and 3. This thickened portion 5 merely represents an increase in the wall thickness, compared with the dimensions of the remainder of the tubing. In the thickened portion 5, at least one tunnel-like passage is provided, which is continuous in the longitudinal direction. In the case of Fig. 2, one passage 6 is provided.

However, in the case of Figure 3, two passages 7 and 8, which run parallel to one another, are provided. These passages can be provided during extrusion of the tubing, the extrusion die being designed accordingly. It is also possible, however, to co-extrude a tubular lining in the form of a small tube of a mechanically serviceable material, in particular a plastics material, into the wall of the tubing in the thickened portion 5, within the passage 6 or passages 7 and 8.

A tubing section obtained as described above, on which a "memory" of smaller dimensions has been impressed, is parted, e.g. by means of a stamping tool; the parting 4, which lies along a meandering line, is thus made in the thickened portion 5. The parting operation is so carried out that, in the case of Figure 2, the passage 6 lies approximately on the centre line M (Figure 1) of the meandering parting 4. In other words, the parting operation is carried out symmetrically with respect to the passage 6. This feature of symmetry also applies to the fitting of Figure 3; in this latter case, the parting operation should be so carried out that the passages 7 and 8 are both within the lateral extremes of the meandering parting 4.

After the parting operation, there is a through cut at the parting 4, and the fitting 3, which up to this operation was still tubular, can be unfolded and laid around a cable or a junction of two cables.

The thickened portion 5 has in each case been sub-divided into two portions by the parting operation, so that there is a thickened portion 9 on one side of the parting 4, and a thickened portion 10 on the other side of it. Each of these thickened portions 9 and 10 has projections 1 1 and recesses 12. The fact that the projections 11 and the recesses 12 were made by one and the same parting operation ensures that, when the two thickened portions 9 and 10 are fitted together, the projections 11 of one portion will precisely fit into the recesses 12 of the other portion.

Each of the projections 11 contains, in the case of Figure 2, a portion of the passage 6, so that when the fitting 3 is fitted together correctly, a complete passage 6 extending along a continuous line will again be present in the vicinity of the parting 4. A rod-shaped closure element can then be inserted into the passage 6. The closure element, which should naturally be of a mechanically reliable material and design may for example be in the form of a wire, or it may again be of a profiled cross section. As soon as the fitting has been fuly closed by means of this closure element, the shrinking operation can be carried out, so that the fitting 3 is shrunk on to a junction or repair point, generally as shown in Figure 1, and fits itself closely thereto.

To make a perfectly tight junction, the inner surface of the fitting 3 can, if desired, be coated before shrinking with an adhesive which is activated when heat is supplied; this measure can in particular provide an additional seal for the end faces of the fitting 3. It is also possible to apply a tape underneath the parting 4, before the shrinking operation, which tape seals this parting from the cable which the fitting 3 surrounds. This tape can also be coated beforehand with an adhesive which is activated when heat is supplied, so that it is bonded to the shrunk-on fitting.

In a modification of the fitting of Figures 2 and 4, two mutually parallel passages 7 and 8 are present in each of the projections 11 as shown in figure 3. In this case, two mutually separate closure elements, or a single closure element bent into the shape of an elongated U, can be used for the closure of the fitting 3.

A fitting according to the invention can also be obtained from tubing which has a cross-section as shown in Figure 5. This tubing has two passages 7 and 8 which are provided in two mutually separate thickened portions 1 3 and 14 of the tubing.

Between the two thickened portions 13 and 14, there is a section 1 5 of the tubing which has an unthickened wall.

Before the projections 11 and recesses 12 required for closing the fitting 3 are produced, the fitting of Figure 5 is parted where indicated by the line 16, so that the sections 15 forms what can be regarded as a lug protruding in the circumferential direction. Subsequently, projections 11 and recesses 12 are formed by punching pieces out of the thickened portions 13 and 14, so that, when the two longitudinal edges of the fitting are brought together, the projections and recesses interengage with one another, and, as a result, the passage 7 and 8 can be aligned to give a single passage 6.

This condition of the fitting 3 can be seen in Figure 6, in which the section 15 is disposed underneath the junctions, and can be regarded as a seal between the junction and the space enclosed. If the surface of the section 1 5 is coated with an adhesive which is activated when heat is supplied, an effective seal is obtained.

A fitting 3 according to the invention as shown in Figures 5-7 is suitable not only for accommodating a single cable; it is also possible effectively to enclose two or more cables in it. For this purpose, preferably on the outer surface of the fitting, additional thickened portions 17 are provided which have fixing-element-receiving tunnel-like passage 18 and extend in the longitudinal direction of the fitting. When a mechanically serviceable fixing element 19 is introduced into the passages 18 of the thickened portions 17, such a fitting 3 can, for example, be constricted in the middle so that its cross-section takes on the shape of a figure "8", as shown in Figure 7. In this way, two distinct spaces 20 and 21 are formed, into which two cables can be introduced.On shrinking, the fitting 3 fits itself against the two cables, and seals them as in the case of a single cable.

With larger numbers of thickened portions 1 7 with passages 18, which can be distributed either uniformly or in a non-uniform spacing around the periphery of a fitting 3, it is of course possible to use the fitting for a larger number of cables, for example, three cables.

In the drawings, the thickened portion 5 is shown as a portion when there is an increase in the wall thickness of the tubular fitting 3, which portion has a symmetrical shape in the sense that the wall is thickened both inwards and outwards.

However, it can instead be a "one-sided" thickened portion, with its thickening either on the inside or on the outside of the fitting. Even then, however, the at least one closure element is accommodated within the thickened portion, and does not entail an additional enlargement of the fitting assembly.

Claims (8)

1. A tubular fitting for an electric cable or a pipeline, which fitting is of an insulating material which shrinks under the action of heat, and has a parting running from one end to the other, the longitudinal edge portions beside this parting being thickened portions which (in use of the fitting) permit secured closure of the fitting by means of at least one closure element, characterised in that: the two thickened portions (9, 10) are provided with projections (11) and recesses (1 2), which are mutually offset in the longitudinal direction, their arrangement being such that the projections of one of the two thickened portions fit into the recesses of the other of the two thickened portions; the projections have closure-element-receiving tunnel-like passages (6; 7, 8) running in the longitudinal direction; and the projections of the two thickened portions can be so fitted together, when the fitting (3) is closed, that the passages are aligned.

2. A fitting according to claim 1, characterised in that the projections (11) project substantially in a circumferential direction of the fitting (3).

3. A fitting according to claim 1 or claim 2, characterised in that the projections (11) each have two passages (7, 8) disposed side by side and running parallel to one another.

4. A fitting according to claim 1, 2 or 3, characterised in that tubular linings of a mechanically serviceable material are provided within the passage(s) (6; 7, 8).

5. A fitting according to any of claims 1 to 4, characterised in that additional thickened portions (17) are provided which protrude laterally on the outside of the fitting, are provided with fixingelement-receiving tunnel-like passages (1 8), and extend in the longitudinal direction of the fitting.

6. A fitting according to any of claims 1 to 5, characterised in that the passages are designed to receive a closure e!ement in the form of a profiled rod.

7. A fitting according to claim 1, substantially as described with reference to any Figure or Figures of the accompanying drawings.

8. A process for the manufacture of a fitting according to claim 1, characterised in that: tubing is extruded from a crosslinkable material, the extrudate having a thickened portion (5) extending in the longitudinal direction and having at least one tunnel-like passage (6); the tubing is crosslinked; a section having a length equivalent to the length of the required fitting (3) is cut from the crosslinked tubing; this section is expanded while being heated, and is caused or allowed to cool in its expanded state; and the cooled section is parted, in the thickened portion, along a meandering line whose meanders are symmetrical with respect to the at least one passage