GB2122037A

GB2122037A - Electric cable connection

Info

Publication number: GB2122037A
Application number: GB08311841A
Authority: GB
Inventors: Raymond Krabs; Manfred Viebranz; Ulrich Fuchs; Gregory Jegarajah Swampillai
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1982-05-03
Filing date: 1983-04-29
Publication date: 1984-01-04
Also published as: NL190346B; DE3216431C2; AU1413483A; ZA833108B; IT1197639B; JPH0410295B2; NL8301488A; JPS58204712A; CA1207045A; GB2122037B; SE8302428D0; GB8311841D0; CH662014A5; FR2526233B1; AU561267B2; SE455976B; AR230902A1; ES521962A0; NZ204059A; ES8405563A1

Abstract

An electrical cable connection for low or medium voltage electricity supply networks, has a connection area (29) surrounded by a rubber- elastically stretchable and elastically stretched sheet material (31) which is secured (41, 42) to the sheaths of the cables and is fastened at adjacent edges (35) to form an enclosure by a quick action closure (37, 38) adapted to be closed under tension. A casting mass is introduced to the connection at a pressure insufficient to substantially inflate the enclosure. <IMAGE>

Description

SPECIFICATION Electric cable connection Technical field The invention relates to an electric cable connection as well as to a process for the production of such a cable connection.

Background art In a known cable connection of the type indicated (U.S. Patent letter 3,419,669) pressuresensitive self-sealing strips are provided at all the edges of a rectangular sheet upon which a spacer material is provided. In the making of this known cable connection the sheet is placed around the connection area, the transverse edges are pressed against the cable sheaths, the longitudinal edges are pressed together except for a small remainder portion forming an introduction opening for the casting mass, and the casting mass is filled in The sheet material in this case must be dimensioned such that it will be capable with the type of cable connection for which it is to be used to enclose even the maximum perimeter being present of the connection area. Correspondingly great will be the necessary amount of casting mass.In order to reduce this amount, it is possible in the production of the known cable connection to tightly press the sheet material arranged therearound against the connection area in certain places by means of clamps. Thereby it is intended to prevent the enclosure formed by the laidaround sheet material from becoming filled to the maximum possible volume by the casting mass.

The clamps mentioned are inconvenient to use.

Because of the mostly irregular shape of the core connection, their fitting requires a certain skill.

Nevertheless, they may easily slide over again, especially if the core connection happens to be a little thicker or particularly irregular. Often the clamps are not at hand or get lost. The obtainable saving in casting mass is insignificant.

In another known cable connection (U.S.

patent letter 3,967,795) the enclosure is formed of a wrapper made with insulating tape. Thereby it may indeed be ensured that the enclosure will lie closely against the connection area conforming to the shape thereof so that but a relatively small amount of casting mass will be necessary to fill the enclosure, however, the production of a sufficiently tight wrapper is very costly in terms of time and labor and requires care and skill.

Disclosure of invention It is the object of the invention to provide a poured cable connection which may be made conveniently and quickly also by less skilled labor and which can do with a very small amount of pouring material.

With the cable connection according to the invention the rubber-elastic encosure lies closely against the cable sheaths and the connection area under the tension caused by the stretching, conforming also to irregular contours such as may be given in the connection area especially with multiple core cables. Because of the close yielding to the shape of the enclosure the space to be filled with the pouring mass is very small so that the consumption of casting mass is correspondingly low. With the quick-acting closure means, preferably in the form of a zipper, the sheet material may be conveniently drawn together and closed for the formation of the enclosure, in which connection rather high elongation stresses may be generated by hand in the enclosure.The casting mass can therefore be introduced at a relatively high pressure, without the enclosure being caused to expand to a disturbing extent, whereby the casting mass may be introduced quickly, quickly and completely penetrating through all the interstices and expelling the air. The casting obtained after curing the casting mass will then be essentially free of air occlusions and thus mechanically solid and electrically safe. It consists only of the really necessary minimum amount of casting mass. In sum mary, there results thus an extremely advantageous combination of easy production, a considerable saving in casting mass, and high mechanical strength and electrical quality of the connection.

Cable protection sleeves have indeed become known which are formed of a sheet material placed around the cable and a zipper provided thereat, said sleeves extending from cable sheath to cable sheath forming a sealing therebetween U.S. patent letter 3,187,090). But these protective sleeves are only forming an additional safety structural member over an otherwise finished and outwardly sealed and protected cable connection. A noticeable elongation of the protective sleeve is not provided for, and neither is the filling-in of a casting mass, and the protective sleeve must be tailored to suit the respective cable connection because of the poor extensibility.Other embodiments of these known protective sleeves are designed as dimensionally stable pockets which are only temporarily placed around a cable connection which has not yet been completed in order to avoid ingress of moisture or dirt during an interruption of work, or the like.

There as well, no elongation of the protective sleeve is provided nor the filling-in of a casting mass. Similar protective sleeves intended for temporary application and closable by zippers are described in the U.S. patent letter 3,495,026.

These known protective sleeves consist of synthetic material, for example, polyvinyl chloride, polyethylene and the like. There is no elongation provided for these protective sleeves nor any filling-in of casting mass.

Mention should be made furthermore of the fact that a flexible protective sleeve provided with a zipper has become known for different purposes from U.S. patent letter 3,038,557; this known protective sleeve is intended in particular for the purpose of providing a supply of grease on bowden cables. There is no similarity to the present invention.

Finally, it should be noted that it has been known already for quite a time from the U.S.

patent letter 2,756,172 in connection with pipes of cast iron or the like which are provided with an outer insulation of asbestos or the like, and an enclosure holding together the insulation, to form the insulation, instead of canvas of a sheet material which in cases may also be elastic, and to close the same by means of a zipper closure.

This does not, however, involve cable connections. and neither in the said patent letter nor elsewhere it has been proposed or suggested that a similar principle can be successfully employed with cable connections.

The present statement that the sheet material is capable of elastic elongation like rubber, is meant to say that there is an expansibility as it is known from natural or synthetic rubber. Such an expansibility may be obtained in different ways; in the simplest case by making the foil part substantially entirely of rubber-elastic material.

But other embodiments are also possible, in which only portions of the sheet material consist of rubber-elastic material capable of elongation, and/or in which a rubber-elastic expansibility is present predominantly or exclusively in the transverse direction only (in a radial direction with respect to the axis of the cable connection). In general, such embodiments will be preferred in which the sheet material consists substantially entirely of rubber-elastic material, because then the essential advantage obtained in accordance with the invention, i.e. the contiguously close covering of even irregular contours in the connection area, is afforded undiminished. Such irregular contours may form in particular in connection of multiple core cables, in which block- or ball-like core connections are distributed in the connection area.With the aid of sheet materials which are only flexible but not rubberelastic, cylindrical connection areas at best may be smoothly covered on all sides, but not connection areas of more complicated shape, such as double-conical or irregular connection areas.

The invention will be described in the following in more detail by way of examples of embodiment and in connection with the drawings, wherein Brief description of drawings Figure 1 is a diagrammatic perspective view of a cable connection according to the invention with parts broken away; Figure 2 is a diagrammatic perspective representation of a sheet material suited for making the cable connection according to Figure 1; Figure 3 is a view similar to Figure 1 showing a diagrammatic perspective representation of another embodiment of a cable connection according to the invention; Figure 4 is a view similar to Figure 2 showing a fractional diagrammatic prespective view of another embodiment of a sheet material for the production of a cable connection according to the invention;Figure 5 is a diagrammatic perspective view corresponding to Figure 2 showing a different embodiment of a sheet material suited to make the cable connection according to the invention; Figure 6 is a diagrammatic perspective view of the inner surface of another embodiment of a sheet material suited for the production of a cable connection according to the invention; and Figures 7 to 11 are diagrammatic views of different stages during the production of a cable connection according to the invention.

Detailed description Figures 2 to 11, part occurring in a corresponding form in Figure 1 are designated with the same reference numerals but with a number characterizing the respective Figure place in front. To avoid repetitions, in connection with such reference numerals, also Figure 1 and the appertaining specification will always have to be referred to.

Figure 1 shows an electric cable connection for connecting two electric cables 1,3, each comprising a cable sheath 5 and 7, respectively, and three cores. In Figure 1, only the cores 9, 11 and 13 of cable 1 are recognizable in the portion of the cable connection that has been broken away. The cores are connected to each other by core connections 1 5, 17, 19 which are surrounded by core connection insulations 21, 23, 25 and kept mutually spaced from each other.

The entire arrangement is surrounded by an enclosure 27 formed of flexible material sealingly extending from cable sheath 5 to cable sheath 7 over the connection area 29, and comprising sheet material 31 laid around the cables, which is connected in itself in two oppositely disposed longitudinal strip areas 33, 35 to form the enclosure 27. The connection is by means of a zipper 37 which is closable in the usual manner by means of a slide 38. The longitudinal strip areas connected to each other are preferably provided along the longitudinal edges of the sheet material 31.In the embodiment shown in Figure 1, the longitudinal strip area 33 as shown as the upper one in Figure 1 together with the one part of the zipper 37 is provided along one longitudinal edge of the sheet material 31, while the longitudinal strip area 35 shown as the lower one in Figure 1 together with the second part of the zipper provided there is arranged spaced through a distance from the adjacent longitudinal edge 39 of the sheet material 31, so that in the condition of being laid around a sealing ledge 40 will form covering the closed zipper 37 from below and sealing the zipper 37 against the interior of the enclosure 27.

The transverse edges 41,42 of the sheet material 31 are provided with sealing means 43, 45 in the form of self-sealing strips and thus are also sealed at the cable sheaths 5 and 7, respectively. These sealing strips may be fastened at the inner surface of the sheet material 31 or may be formed integrally with the sheet material 31.

A casting mass 47 capable of being cured is filled into sleeve-shaped enclosure 27, which fills all the interstices and after curing will form a mechanically solid block. Provided between the sheet material 31 and the core connections 15, 1 7, 1 9 is a spacer material 49 which preferably consists of an open matting and is penetrated by the casting mass 47. For the usual multiple core low voltage cable connections, for instance, in 1 1V household current supply malns and the like, a mat of an open matting having a thickness of 5 to 20 mm is suited which consists of loosely interconnected randomly oriented fibers of synthetic material having a diameter of about 0.5 mm.

Suitable open mattings of polyamide or polyester fibers are commercially available.

The sheet material 31 is strongly rubberelastically extensible and, according to the embodiment of Figure 1 , for this purpose, consists as a whole of a strongly extensible rubber-elastic material such as, for instance, neoprene or the like. Especially suited for cable connections of the above mentioned type are sheets of a polychloroprene polymer having the following properties: Shore hardness 36 Tensile strength (MPa) 1 5.5 Elongation at break (%) 895 Breaking strength (N/mm) 26.

The zipper 37 shown in Figure 1 is a particularly simple and advantageous embodiment of a quick-acting connecting means which is adapted to be closed under a transverse tension. Other forms of such quick-acting closure means include, for instance, interengaging profile sections which may be hooked into each other by means of a closure slide, similar to a usual zipper.

In each case it is necessary that the quick-acting closure means closes, and preferably is also closable, while being under transverse tension because in the cable connection described, the enclosure 27 sits on the connection area while being elastically stretched. The sheet material 31 is dimensioned such that it can be closed about the connection area 29 only under stretching and the zipper 37 is designed in such a manner that it can be pulled closed under a transverse tension. Thereby, the rubber-elastic sheet material 31 is stretched and subjected to a tensile stress. The tensile stress may be considerable and is restricted only by the force available for pulling the zipper closed.

The filling-in of the casting mass 47 may on principle be carried out in any suitable manner, for instance, through an aperture in the enclosure 27 formed therein by piercing it with a syringe.

Because of the high stretching forces which are possible in the enclosure 27 it is, however, recomended to provide the sheet material 31 with a special casting mass introduction aperture 53 at a location remote from the edges thereof, which may easily be designed in such a manner that the sheet material 31 will not rupture in that location.

What is particularly advantageous is the formation thereof in a strength-enhancing connecting piece 55 which may easily be made in one piece with the sheet material 31 and which may, in addition, easily be designed for contacting with an injection nozzle of a casting mass injection apparatus (now shown).

The sheet material 31, suitably, has at least one air exit opening. In that case one does not have to rely on the air escaping through leaks, for example, of the quick-acting closing means (zipper 37) upon the casting mass being filled in, and can design the quick-acting closure means as well as also the seals 43, 45 in such a manner that a high degree of tightness is ensured. This is easily possible in connection with zippers in wellknown manner in that the interengaging closure sections provided in the longitudinal strip areas 33, 35 are formed as continuous ledges of synthetic material (not shown). Such ledges of synthetic material may, besides, advantageously be formed at least in part integrally with the sheet material 31; this simplifies substantially the production.

In the embodiment according to Figure 1, air exit openings 57, 59 are provided one each on either transverse edge 41, 42 of the sheet material 31. In both embodiments shown, these openings are quite simply formed by hoses 61 and 63, respectively, which are passing through the sealing means 43 and 45, respectively, or are simply fixed by an adhesive to the inner surface of the sealing means, or are inserted below the sealing means when the sheet material 31 is laid around. The known-per-se technique is very simple and enables a safe predication as to when the cable connection is completely filled with the casting mass; in that case, excess casting mass will exit from both air exit openings 57 and 59.So that the casting mass will exit only after the filling of the enclosure 27 has been completed, it is to the purpose to arrange the casting mass introduction opening 53 spaced from the air exit opening through as great a distance as possible.

Accordingly, in the embodiment of Figure 1, the casting mass introduction opening 53 is disposed about midway between the two air exit openings 57 and 59.

It is easily recognizable that the openings as described for the introduction of casting mass and for exiting air, respectively may advantageously be formed at least in part integrally in the sheet material 31. In that case, no special measures are necessary when laying the sheet material around, in order to provide the openings in the proper location.

It will furthermore be noted that the enclosure surrounding the connection area 29 under rubberelastic elongation contiguously adapts itself throughout to the contour of the connection area, so that it is ensured that only the absolutely necessary minimum amount of casting mass will be consumed.

Figure 2 shows a sheet material 231 which is on principle suited for the production of an enclosure according to the type of enclosure 27 shown in Figure 1. In the embodiment according to Figure 2, it is assumed that the parts 237a and 237b of the zipper 237 are formed integrally at the longitudinal edges of the sheet material 231.

The sealing means 243 and 245 provided at the transverse edges and the hoses 261 and 263 placed therein as well as the connection piece 255 with the casting mass introduction opening 253 are designed similar to tha corresponding parts of Figure 1. Insofar, reference is made to the description of Figure 1.

Figure 3 shows an embodiment in which, similar to Figure 2, the quick-acting closure means are provided in the form of a zipper 337 at the longitudinal edges of the sheet material 331.

As a speciality, provision is made for the quickacting closure means to be formed with a leak suited to vent the enclosure 327. Such a leak normally will result already when a zipper of the usual type is used for the quick-acting closure means. The leak, however, is not so great that when filling in the casting mass, disturbing amounts of excess casting mass can exit through the quick-acting closure means. Suitably, in this embodiment, when making the cable connection, the quick-acting closure means is arranged to be disposed on top, as shown in Figure 3. One may also restrict the venting to certain areas of the quick-acting closure means by the provision of sealing means in other regions where air is not to exit, comprising, for example, a marginal portion 40 of the sheet material effective as a sealing ledge 40 in accordance with Figure 1.Figure 3 shows that the quick-acting closure means 337 are extended in a curve line around the casting mass introduction opening 353 which is likewise to be arranged on top during the production of the cable connection. In the embodiment according to Figure 3 the casting mass introduction opening 353 is provided in a filling chute 355 into which the casting mass is poured pressureless. In the embodiment shown, comprising a leak suited for venting in the quick-acting closure means 337, the construction of the sheet material 331 is evidently especially simple, so.that the production is particularly easily possible. As may readily be seen, one may also form a casting mass introduction opening by leaving a small opening in the process of closing the quick-acting closure means. Thereby, the sheet material is even simpler.However, the proper dimensioning of the portion to be left open calls for a certain degree of care; in general, one will therefore prefer embodiments in which the quick-acting closure means are pulled entirely closed and in which a special casting mass introduction opening is provided.

It goes without saying that the quick-acting closure means may also be provided to be present in several portions, So, for instance, a zipper may be used that can be pulled closed from both ends by means of a closure slide.

Figure 4 illustrates the possibility of fixedly arranging the spacer material 449 on the inner surface of the sheet material 431. This facilitates the production of the cable connection.

Figure 5 shows a sheet material 531 in which a casting mass introduction opening 553 is arranged in an elongated connecting piece 555 midway between two air exit openings 557 and 559. The latter are provided near the transverse edges and the sealing means 543, 545 provided there, in venting pipes 67, 69. It is easily possible to provide in the connecting pieces closure means, valves or the like such as a check valve (not shown) in the connecting piece 555 of the casting mass introduction opening 553. In the case of the embodiment shown, the connecting pieces 555, 67 and 69 are formed as separate members and are welded to the sheet material 531 or adhesively connected thereto.To enhance the strength one will then suitably select for the connection pieces a somewhat harder material, for example, a polychloroprene polymer having the following properties: Shore hardness 70 Tensile strength (MPa) 1 5 Elongation at break (%) 300 Breaking strength (N/mm) 33.

Figure 6 shows a sheet material 631 provided with knubs 649 on the inner surface thereof.

These knubs are effective as spacing material ensuring a certain distance from the core connections. The knubs may also easily be formed integrally with the sheet material 631 during production thereof. In the embodiment shown, the knubs 649 are designed substantially to be cylindrical and are regularly distributed in rows, more specifically, in longitudinal rows. It has been found that thereby the rubber type elasticity of the material of the sheet material 631 is least impaired by the knubs 649.In Figure 6 it can be seen that with this embodiment the sealing means 643, 645 are provided in the form of ledges at the transverse edges of the sheet material 631, and that similar to the embodiment of Figure 5, connection pieces 655, 667 and 669 are provided which are formed as separate constructional members and connected to the sheet material 631 afterwards; these connection pieces contain the casting mass introduction opening 633 and the air exit openings 657 and 659, respectively.

Figure 7 to 11 illustrate the production of a cable connection between two multiple core cables 701,703 with a sheet material 731 of the type shown in Figure 5. A separate spacer material 749 is utilized in the form of an open matting of an approximately dovetail-shaped outline, so that the matting has a web portion 71 and two wing portions 73, 75. According to Figure 7 the web portion 71 of the spacer material 749 is first laid around the core connections which have been completed and insulated before, such as the core connection 717, for example. This done, the wings (Figure 8) 73, 75 are also laid around the core connections.

The wrapper 77 thus formed (Figure 9) may be temporarily held together by means of clamps or the like. Thereupon, a sheet material 731 is laid around the connection area 729. At the longitudinal edges 733,735 of the sheet material 731, portions of a zipper 737 are provided. A closure slide 738 of the zipper is arranged on the zipper portion of the longitudinal edge 735. The sheet material 731 is laid around the connection area 729 in such a manner that it extends from cable sheath 705 to cable sheath 707, and the slide of the zipper 737 is hooked-in at the one end of the zipper (Figure 10) while stretchingly pulling the sheet material 731 around, and pulled closed (Figure 11).In so doing, the sheet material is extended, and the sheet material is sealed to the cable sheaths 705, 707 along the transverse edges thereof by means of the sealing means 743, 745 provided thereat. Thereupon, a casting mass is filled into the casting mass introduction opening 753, and the air displaced during the operation of filling-in may escape through the air exit openings 757 and 759. In any case, the casting mass is introduced at a pressure insufficient to substantially inflate the enclosure 731. After curing the casting mass the cable connection is finished.

It will be noted that the essential steps ot the process described consist in that a sheet material of strongly expansible rubber-elastic material is closed on the connection area and around it while being subjected to elongation by means of quickacting closure means closable under a transverse tension, preferably in the form of a zipper, and thereupon the casting mass is introduced at a pressure insufficient to substantially inflate the enclosure. As has already been explained before, the quick-acting-closure means may in general be provided in oppositely disposed strip-shaped areas, preferably marginal areas, of the sheet material 731 that has been laid around.

If a sheet material is utilized that does not adhere to the casting mass, the sheet material may lie removed after the casting mass has been cured. This is made possible by using a sheet material which is free of spacer material fastened thereto and is provided on the inner surface thereof with a release material preventing the casting mass from sticking thereto. As a separation material, silicone grease may be used.

The making of the cable connection according to the invention may be rendered particularly simple by the provision of a prefabricated kit of constructional members for the production of the cable connection, comprising all the necessary parts, i.e. especially a rubber-elastic sheet material suited for the respective type of cable connection.

Claims

1. An electric cable connection, especially for low and medium voltage electricity supply networks, in a connection area between at least two electrical cables each having at least one core and a cable sheath, the cable connection comprising a core connection which preferably is provided with a core connection insulation, an enclosure formed of flexible material extending sealingly from cable sheath to cable sheath over the connection area and having a sheet material laid around the cables, said sheet material having oppositely disposed interconnected longitudinal strip areas preferably along longitudinal edges of the sheet material and transverse edges lying in close contact against the cable sheaths, said transverse edges being preferably provided with sealing means, and casting mass filled into the enclosure, with the spacer material preferably provided between the sheet material and the core connection, which is permeated by the casting material and preferably fixedly attached to the inner surface of the sheet material, characterized in that the sheet material (31) is strongly stetchable rubber-elastic, and is dimensioned so that it can be closed around the connection area (29) only when stretched, and in that the longitudinal strip areas (33, 35) of the sheet material (31) are provided with quick-action closure means (37, 38) closing under transverse tension.

2. A cable connection according to claim 1, characterized in that the quick-action closure means comprise a zipper.

3. A cable connection according to claim 1 or 2, characterized in that the quick-action closure means are-designed with a leak suited to vent the enclosure.

4. A cable connection according to anyone of the preceding claims, characterized in that the sheet material (31) is provided with a casting mass introduction opening (53).

5. A process for the production of a cable connection, especially for low and medium voltage current supply networks, in a connection area between two electrical cables each comprising at least one core and one cable sheath, said process comprising the following steps: a) making a core connection and preferably insulating same, b) laying a sheet material around the connection area from cable sheath to cable sheath, if desired or required, with the interposition of a spacer material which is adapted to be permeated by the casting mass, c) sealing the sheet material at the cable sheaths, preferably by means of sealing means provided on the sheet material, d) forming an essentially closed enclosure by interconnecting oppositely disposed strip-like areas, preferably marginal areas, of the sheet material laid around, e) introducing a curable casting mass into the enclosure until it is completely filled, and f) curing the casting mass.

characterized in that the enclosure is formed by f) curing the casting mass characterized in thqt the enclosure is formed by g) closing a sheet material of strongly rubberelastic material on and about the connection area while being subjected to elongation by means of quick-action closure means adapted to be closed under a transverse tension, preferably in the form of a zipper, and h) introducing the casting mass at a pressure insufficient to substantially inflate the enclosure.

6. An electric cable connection substantially as herein described with reference to the accompanying drawings.

7. A process for the production of a cable connection substantially as herein described.