GB2219442A

GB2219442A - Sealing screw-clamps for cables

Info

Publication number: GB2219442A
Application number: GB8907047A
Authority: GB
Inventors: Gunther Knill; Georg Hillinger
Original assignee: MOSDORFER GmbH
Current assignee: MOSDORFER GmbH
Priority date: 1988-03-30
Filing date: 1989-03-29
Publication date: 1989-12-06
Also published as: NO891323D0; IT1228765B; AU602287B2; AU3222189A; ATA84588A; NO891323L; GB8907047D0; IT8919932A0

Abstract

A branch clamp for insulated conductors, in particular overhead lines, comprising a clamp body formed by at least two jaws (1, 2) connectable with each other by at least one screw (5), with at least two ducts (7) for receiving the conductors (16) being provided in the clamp body and with groove-shaped recesses (8, 9; 10, 11) corresponding to the ducts (7) being provided in the jaws (1, 2), and with at least one contact bridge (14) having projections (15), preferably tips, projecting into the ducts in the clamp body, said contact bridge being arranged in one jaw between its recesses. At least the portions of the contact bridge (14) projecting into the ducts (7) are covered with a deformable material impervious to moisture in the form of a melting adhesive (17), such as a mixture of thermoplastic caoutchouc and mineral oils and resins. <IMAGE>

Description

BRANCH CLAMP The invention relates to a branch clamp for insulated conductors, in particular overhead lines, comprising a clamp body formed by at least two jaws connectable with each other by at least one screw, with.at least two ducts for receiving the conductors being provided in the clamp body and with groove-shaped recesses corresponding to the ducts being provided in the jaws, and with at least one contact bridge having projections, preferably tips, projecting into the ducts, being provided in the clamp body, said contact bridge being arranged in one jaw between its recesses, at least the portions of the contact bridge projecting into the ducts being covered with a deformable material impervious to moisture.

In branch clamps of that type, the sealing in the area of the contact bridges constitutes a problem which has not yet been solved satisfactorily. If in the usual manner grease with which the recesses of the jaws are filled (cf. German Patent 2 903 960) is used for that purpose, the disadvantage is that an additional working step is necessary at site and that excessive development of heat, e.g. by insolation, can liquefy the grease and thus the sealing is lost. It is known to make the jaws of the branch clamp themselves of soft elastic material (German Utility Model G 8 734 948).

However, in that case the problem arises that it is difficult to press the jaws together to obtain the seal and that dimensionally stable auxiliary components, which render the design of the branch clamp more complicated and expensive, are required, without completely excluding a gap between the jaws, in particular in rough assembly at site. In addition to that design it has also been proposed to fill a soft elastic material into the jaws and to use closed-pore silicone or polyurethane foam for that purpose. In another branch clamp, a seal consisting, if necessary, of several sealing elements is provided, which is made of a compressible, permanently soft elastic material, e.g. an open-pore polyurethane foam impregnated with a sealing material, such as artificial caoutchouc or bitumen (Austrian Patent 367 245).In this connection plastically deformable material is referred to as disadvantageous and unsuited because the thermal expansions caused by weather conditions result in material fatigue in a relatively short period of time so that the reliable sealing is lost. The measure of providing a separate sealing is unfavourable insofar as it may be lost before or while the branch clamp is mounted and in any case necessitates a separate working step for impregnating the open-pore foam.

The object of the invention is to eliminate the disadvantages mentioned above and to provide a branch clamp which can be manufactured without complicated equipment and in which the sealing is completely satisfactory and reliable also over a long period of time and even under the most unfavourable conditions.

This object is achieved with a branch clamp of the type mentioned above in that the material according to the invention is a melting adhesive.

In a preferred embodiment of the invention the melting adhesive may be a mixture of thermoplastic caoutchouc and mineral oils and resins, such as the one put on the market by Heinrich Bühnen ICG, of Bremen, FRG, under the tradename "HeiBschmelzkleber 1529".

In one embodiment of the invention the branch clamp may comprise a cap covering one duct, said cap being filled with the melting adhesive.

When manufacturing the branch clamp, the melting adhesive is heated at its processing temperature and is cast in predetermined amounts into the recesses of the jaws of the clamp body provided with the contact bridge or bridges, respectively, and, if necessary, is cast into the cap as well as onto the contact bridges.

In practice, films strippable in the usual manner are applied to the free surfaces of the melting adhesive in order not to affect the adhesiveness of the melting adhesive, e.g. by impurities, and to prevent the two halves of the clamp from sticking together.

The effects achieved with the branch clamp of the invention lie in obtaining an excellent sealing between the melting adhesive and the conductor insulation and of course also between the melting adhesive fillings of the individual jaws and with respect to the jaws themselves as a result of the plastic deformability and surface adhesion of the melting adhesive, which sealing not only meets the present requirements, but even exceeds these by far in some aspects.

Among others, e.g. an imperviousness to salt water (sea water) over a temperature range of from below OOC up to the softening point of approximately 900C is achieved, in which range the dielectric strength according to various European Standards is reached. In addition, the good adhesiveness of the melting adhesive has the advantage that the fillings in the jaw recesses are arranged such that they cannot be lost. Moreover, by using the melting adhesive for sealing purposes the prejudice of those skilled in the art expressed e.g. in the Austrian Patent No. 367 245 that a plastically deformable material is unsuited as a sealing material is overcome. The strong adhesive forces of the melting adhesive permit its plastic deformation without any loss in adhesion and thus in sealing.It has to be pointed out that heating of the melting adhesive to achieve a sealing effect is not necessary.

The invention is explained in greater detail below by means of a preferred embodiment which is illustrated in the drawings; Fig. 1 is a front view of the branch clamp, Fig. 2 is a top view of the branch clamp, Fig. 3 is a section along the line III-III in Fig. 2, Fig. 4 is a bottom view of the upper jaw, and Fig. 5 is a section along the line V-V in Fig. 2.

According to Figs. 1, 2 and 5 the branch clamp substantially consists of two jaws 1, 2 of electrically insulating material which can be clamped together by means of two shim plates 3, 4 of metal and two screws 5 which are screwed into threaded holes 6 of one shim plate 4 (Fig. 5). In the branch clamp two adjacent parallel ducts 7 lying side by side are provided, which are formed each by two groove-shaped recesses 8, 9 and 10, 11, respectively, in the respective jaws 1, 2.

As shown more clearly in Figs. 3 and 4, one of the ducts is covered with a cap 12 which is movably - but so that it cannot be lost - inserted in the likewise cap-shaped projection 13 of the one jaw 1.

According to Figs. 3, 4 and 5 three web-shaped contact bridges 14 are arranged in corresponding recesses in each jaw 1, 2, which contact bridges each extend from one recess 8 or 10, respectively, to the other recess 9 or 11, respectively, of the respective jaw 1 or 2, respectively, and are provided with tooth-shaped projections 15 on their sides projecting into the ducts 7. As shown in Fig. 5, these projections 15 serve to penetrate the insulation of the conductors 16 inserted into the branch clamp and to establish the electric contact between the two conductors 16. In the embodiment shown, the end of the branch conductor is covered by the cap 12.

In the course of the manufacture of the branch clamp, a predetermined amount of melting adhesive 17 is filled into each jaw 1, 2 provided with the contact bridges 14. For this purpose, the melting adhesive 17, which is in particular a mixture of thermoplastic caoutchouc and mineral oils and resins, as sold by Heinrich Bhnen KG of Bremen, FRG, under the tradename "HeiBschmelzkleber 1529", is heated at its processing temperature of from 1500 to 1800C and is cast in this condition at least onto the contact bridges 14.

However, preferably also the groove-shaped recesses 8 to 11 of the jaws 1, 2 are filled with the melting adhesive 17, as shown in Fig. 3. Finally, the free surfaces of the melting adhesive 17 are covered with a strip film 18.

Likewise, the cap 12 preferably made of soft elastic material is filled with the melting adhesive 17.

When mounting the branch clamp, the films 18 are stripped first, and then the conductors 16 are inserted between the jaws 1, 2 and aligned with respect to the recesses 8 to 11. When the screws 5 are tightened, the jaws 1, 2 are clamped together and the melting adhesive 17 is sealingly and adhesively pressed against the insulation of the conductors 16 and is deformed. Subsequently, the projections 15 penetrate the melting adhesive 17 and further the insulation of the conductors 16 to their electrically conducting cores until the jaws 1, 2 contact each other and form the ducts 7. During this step, excessive melting adhesive 17 may emerge from the branch clamp.

Tests have shown that the melting adhesive used according to the invention not only has the required electric insulating properties and even exceeds these, but, moreover, in an excellent way is resistant to relatively high temperatures, great fluctuations of temperature, salt water, ozone and ultraviolet rays.

Another advantage is that the melting adhesive can be applied to the contact bridges in a relatively simple manner and that measures for fastening the se-1 formed in this way to the J aws may be dispensed with.

As mentioned above, the melting adhesive excellently adheres to the insulation of the conductors inserted into the branch clamp as a result of the surprisingly good adhesion in the processed condition, and renders any subsequent treatment of the melting adhesive superfluous.

However, it is of course possible to subject the melting adhesive to a heat treatment after mounting the branch clamp.

Claims

Patent Claims

1. A branch clamp for insulated conductors, in particular overhead lines, comprising a clamp body formed by at least two jaws connectable with each other by at least one screw, with at least two ducts for receiving the conductors being provided in the clamp body and with groove-shaped recesses corresponding to tile ducts being provided in the jaws, and with at least one contact bridge having projections, preferably tips, projecting into the ducts, being provided in the clamp body, said contact bridge being arranged in one jaw between its recesses, at least the portions of the contact bridge projecting into the ducts being covered with a deformable material impervious to moisture, characterized in that the material is a melting adhesive.

2. The branch clamp according to claim 1, characterized in that the melting adhesive is a mixture of thermoplastic caoutchouc and mineral oils and resins.

3. The branch clamp according to claim 1 or 2, comprising a cap covering one duct, characterized in that the cap (12) is filled with the melting adhesive.

4. A branch clamp substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.