GB2023477A

GB2023477A - Improvements relating to binding together the wires at a non- insulated multi-wire conductor

Info

Publication number: GB2023477A
Application number: GB7919716A
Authority: GB
Original assignee: NORSK ELEKTRISK KABEL
Current assignee: NORSK ELEKTRISK KABEL
Priority date: 1978-06-21
Filing date: 1979-06-06
Publication date: 1980-01-03
Also published as: NL175123C; NO141289C; DE2923220C2; DE2923220A1; NL7904835A; SE7905188L; GB2023477B; NL175123B; NO782164L; DK254779A; NO141289B

Abstract

A method of binding together the ends of the wires (e.g. copper) on an non-insulated end section (3) of an insulated multi-wire conductor (e.g. cable) (1) by means of a bonding agent. This is obtained in that the bonding agent is applied to the end surfaces (13) of the wires, which have been exposed by a cut through the cable, while the ends of the wires remain held together by the surrounding insulation (4), after which a desired length of the insulation is removed from the conductor. Preferably liquid tin is used as a bonding agent which is applied to the end surfaces of the wires following application of flux. <IMAGE>

Description

SPECIFICATION Improvements relating to binding together the wires at a non-insulated end section of an insulated multi-wire conductor The present invention pertains to a method of binding together, by means of a bonding agent, the ends of the wires on at least one non-insulated end section of an insulated, multi-wire conductor, preferably in a multi-core cable having conductors made of multiple copper wires twisted together.

The invention also pertains to an insulated multiwire conductor as produced by the method of the invention, having at least one non-insulated end section in which the wires are held together by means of a bonding agent.

The conventional practice when the ends of the wires on a non-insulated end section of an insulated multi-wire conductor are to be bonded together is first to remove the insulation from the end of the conductor and then to coat the noninsulated, twisted ends of wire with tin, a flux having first been applied to promote the coating process. The coating of tin can be applied either by dipping the ends of the wires into a liquid tin bath, or by passing the ends of the wires through a stream of liquid tin. The same process is used for multi-core cables having multi-wire conductors.

When conductors with tin-coated ends are to be coupled to switches or to an apparatus, the end of the conductor is inserted into a sleeve and retained therein by a screw which is screwed through a threaded bore in the sleeve. Experience has shown, however, that the resultant pressconnection of the screw, tin-coated conductor end and the interior of the sleeve will become weakened with time, because the tin-coated end of the conductor, which usually consists of copper wires, has very little elasticity; thus, when the fastening screw is screwed in, the tin-coated conductor end merely becomes deformed without exerting any spring force against the screw.As a result, if the fastening screw loosens somewhat owing to vibrations, which often happens, the tincoated, deformed conductor end, having reduced or deficient elasticity, will be released from the pressure of the screw to lie loose in the sleeve; in this case, the conductor end will either slide out of the sleeve, or it will be held so loosely that an oxygen coating will form, with the result that the electrical contact will either be broken or deteriorate.

It has been shown that conductor ends made of copper wires which have not been coated with tin have much greater inherent flexibility, so that the fastening screws have less tendency to loosen when the coupling is subjected to vibrations.

However, conductor ends consisting of several thin copper wires which have not been coated with tin have a tendency to unravel, because when the insulation is being removed from the twisted copper wires of the conductor, the pulling motion untwists the wires somewhat, causing them to separate. This is not desirable when the non ulated conductor end is to be inserted into a narrow sleeve opening and subsequently fastened therein by means of a press screw.

It is the purpose of the present invention, therefore, to provide through the method of the invention a non-insulated conductor end section in which the wires are held together by means of a bonding agent, preferably tin, at the outer ends of the wires, so that the coating or the tin does not adversely affect the elastic properties of the noninsulated conductor end retained in a coupling sleeve by a press screw.

This is achieved according to the invention by means of the method features disclosed in the appurtenant main claim and subclaims, and an insulated multi-wire conductor of the type specified introductorily is thereby produced in which the wires are bonded together only in the region of the end surfaces thereof.

In addition to the improved coupling capabilities of the conductor when used in connection with a sleeve and press screw, a conductor coated in accordance with the method also requires less tin, because only the end surfaces of the wires which have been exposed by the cut are coated with tin, the liquid tin penetrating only a small distance in between the wires while the wire ends remain held together, in the twisted state, by the surrounding insulation. In this way, one also avoids the tendency of the ends of the conductor wires to separate as they become partially untwisted during the removal of the insulation, as has occurred heretofore when the insulation was removed from the ends of the conductor wires before the coating of tin was applied.

Instead of tin, another suitable binding coating could be applied to the end surfaces of the conductor wires, but the coating means should preferably be of a type which solidifies quickly, so that the insulation can be removed from the end section of the conductor immediately following the coating treatment.

The characteristic features of the invention are disclosed in the appurtenant patent claims, and the invention will be explained in further detail in the following description of the method and of the conductor produced thereby, having a noninsulated end section in which the ends of the wires are bound together, with reference to the accompanying drawings, where Figure 1 shows the construction of a multi-core cable, Figure 2 shows a multi-core cable with a straight cut end being passed through a liquid stream of tin to coat the end, and Figure 3 is a schematic drawing of the production process, in which cut lengths of cables are clamped to a conveyor belt which carries the cable length ends to successive stations for application of flux, tinning, removal of insulation, and delivery to a collecting station, respectively.

Figure 1 shows a cable 1 with outer insulation 2 surrounding two multi-wire conductors 3, each of which is covered by insulation 4. The multi-wire conductors are preferably made of twisted copper wires. The cable 1 is cut into suitable lengths, making sure that the end of the cable is cut cleanly such that the exposed end surfaces of the conductor wires 3 are flush with the cut surface of the cable. Figure 2 shows how the cable 1 is guided into a stream 5 of liquid tin 6 which is melted in a melt vessel 7 with an overflow edge 8.

Flux has been applied to the exposed ends of the wires in the cable 1 prior to this tin-coating operation, in order to facilitate the coating process. The stream of tin 5 is collected in a vessel or trough 9 and recirculated, for example, by means of a pump 10 and tubes 1 1, 12, to the melt vessel 7.

Following the tin coating process, 2 section of the outer insulation or mantle 2 on the cable is removed in a manner known per se, and a section of the insulation 4 around the conductors 3 is subsequently removed over a certain length such that the conductors 3 with the insulation 4 and the non-insulated ends project out beyond the outer insulation on the cable 1. The non-insulated portions of the conductors 3, which consist of twisted copper wires, are, as shown on Figure 1, held together at the end surfaces thereof by tin, or optionally by some other binding coating, and are also joined in a small area in between the ends of the wires, as shown at 13.

The various steps of the production process are shown schematically in Figure 3. A chain conveyor 14 is provided with gripping means 15 for retaining lengths of cable 1 which have been cut and inserted between the grippers in a preceding station, not illustrated on the drawing. The chain conveyor 14 is moved in steps such that the length of cable shown at the left of Figure 3 will progress in a subsequent movement to station 16, where flux is applied to the end surfaces of the conductor wires. With the next movement, the length of cable 1 is brought to station 17, where the cut end surfaces of the conductor wires 3 are coated with tin, as discussed above and shown in Figure 2. With the next movement, the length of cable 1 is led to station 18, where the mantle and the insulation are removed from the cable 1 and the conductors 3, respectively, as discussed above and shown in Figure 1.With the next movement, the length of cable 1 is led to station 19, where the length of cable is removed from the chain conveyor 14, or optionally taken to a packing apparatus where a predetermined number of cable lengths are collected and bundled together.

As mentioned previously, the cut surfaces of the conductor wires can be joined by any means whatsoever which is capable of holding the ends of the conductors 3 together after the insulation has been removed; one thus obtains the advantage mentioned above, i.e., that the noninsulated ends 3 of the conductors are not adversely affected by the coating means, e.g., tin, and one thus avoids the slesve-coupling problems discussed previously.

The end surfaces of the wires can also be coated with tin by dipping the ends into a tin bath, and the lengths of cable 1 can be carried to the different treatment stations in any suitable manner, the method shown on Figure 3 merely being intended to be illustrative of one possible way in which this might be done.

Claims

1. A method of binding together with a bonding agent the ends of the wires of at least one non insulated end section of an insulated multi-wire conductor, wherein the bonding agent is applied to the end surfaces of the wires, which have been exposed by a cut through the cable, while the ends of the wires remain held together by the surrounding insulation, and, thereafter, a desired length of the insulation is removed from the conductor.

2. A method as claimed in claim 1 wherein the conductor is an element of a multi-core cable comprising multi-wire conductors each made of multiple copper wires twisted together.

3. A method as claimed in claim 1 or claim 2 wherein the bonding agent is applied to the end surfaces of the wires by dipping them into a bath of liquid bonding agent.

4. A method as claimed in claim 3 wherein the bonding agent is tin and a flux is applied to the end surfaces of the wires before they are dipped in the bath of liquid tin.

5. A method as claimed in claim 1 or claim 2 wherein the end of the conductor with the exposed end surfaces is passed through a stream of the bonding agent.

6. A method as claimed in claim 5 wherein the end of the conductor with the exposed end surfaces of the wires is passed into said stream, allowed to remain there briefly, and subsequently guide out of the stream.

7. A method as claimed in claim 5 or claim 6 wherein the bonding agent is tin.

8. An insulated multi-wire conductor having at least one non-insulated end section in which the wires have been bound together using a bonding agent by a method as claimed in any preceding claim, wherein the wires are bound together by the bonding agent only at an area at or adjacent the free end surfaces of the wires.

9. A method of binding together the ends of wires at an end of an insulated multi-wire conductor, substantially as hereinbefore described with reference to the drawings.

10. An insulated multi-wire conductor having the wires at a non-insulated end section of the conductor bound together by a bonding agent, the conductor being substantially as hereinbefore described with reference to and as illustrated in Figure 1 of the accompanying drawings.