EP0000731B1 - Method of tapping an insulated electric cable - Google Patents

Description

The invention relates to a method for producing branches on an electrical cable insulated by a continuous sheath, in which an electrical connection point is formed at a branch point of the cable having a core within the sheath, the sheath being opened in the region of the branch point and through which Opening a piece of ladder sticks into the inside of the shell.

Various methods of making such an electrical connection are known. However, all of these procedures require the stripping of this cable, which is greater the larger the required contact area, in order to ensure a reliable electrical connection to the cable.

In a method which has become known from FR-A-2 245 103, at least one cable end is first stripped. The cable is further stripped over a predetermined small distance in the area of the branch to be formed, and a conductor piece is then inserted into the interior of the cable in such a way that the small cables located here and forming the soul, which are individually insulated again, do not have their own insulation to be damaged. Thereupon a conductive solution liquid is introduced and after the formation of electrical connections, the electrical connection between the conductor piece and the desired small cable within the soul is produced via the conductive solution liquid.

The present invention has for its object to provide a method according to the preamble of claim 1, which allows the creation of large contact areas in a very simple manner within wide limits and keeps stripping work of negligible order of magnitude.

The solution according to the invention consists in a method of the generic type in that the sheath is opened by an access to the electrically conductive part of the core of the cable giving incision, the conductor piece between the electrically conductive part of the core of the cable and the insulating sheath under friction by the Formed access is inserted such that the conductor piece lies on a predetermined length extension of the cable in contact with the electrically conductive part of the soul. Cutting in with an appropriate tool is very easy to do, although stripping work is not really necessary. The size of the contact surface can be easily adapted to the desired size. Since the incision gives direct access to the electrically conductive part of the soul, aids such as electrically conductive solution liquids and the like are not required. The use of equipment for carrying out the method is also extremely small. In principle, nothing is required other than the tool for making the incision and the conductor pieces themselves. Flanging work and also welding or soldering work are not absolutely necessary, at least in principle.

Preferred embodiments of the method according to the invention result from the subclauses.

In particular, it can be expedient to bend the cable at the location of the incision in the order of 90 °, so that the resulting widening of the incision on the outer jacket of the sheath makes it easier to insert the conductor piece. The lateral lips of the insertion incision are expanded elastically.

According to a further preferred embodiment of the method according to the invention, a line piece with an essentially rectangular cross section is used. Its part protruding from the cable is preferably bent over after insertion.

According to a further preferred embodiment, two lines are inserted through the access created in opposite directions, the two sections of which lie outside the cable and are mechanically and electrically connected to one another in such a way that the branch cannot be detached.

In a further embodiment, the two conductor section sections are twisted together outside the main cable.

It is also possible to additionally weld or solder the conductor pieces electrically to the cable. If two conductor pieces are used, these can be connected to one another by one and the same welding or soldering process.

If tin and a decapitation agent are applied at the point of the incision at the outlet of the conductor section or sections, the welding can take place after local preheating by compressing the end of the conductor section or sections as close as possible to the branch point between two graphite electrodes, which are caused by a current of great strength. Other types of welding or soldering are also possible.

In this way, a branch can be produced which is extremely secure against tearing of the branch if the cable or the branch lines are subjected to tensile loads during operation. According to a further embodiment of the method, the incision is closed by a sealant. In the event that the outer section of the conductor section or sections, which is not directly involved in the design of the connection, is insulated, the connection zone can be easily encapsulated with a suitable material. In this case it is also possible to achieve the tightness of the connection zone by surrounding it with two insulating half-shells.

In this way it is very easy to restore the tightness of the connection in accordance with the particular environmental conditions.

According to a further preferred embodiment, the incision for the insertion is made at the point of the junction, either by grinding the insulating sheath or by inserting it with a suitable tool.

• Fig. 1 ein mit einer durchgehenden Hülle isoliertes elektrisches Kabel, das mittels des erfindungsgemäßen Verfahrens mit mehreren Abzweigungen versehen ist,
• Fig. 2 ein Kabelstück, in dessen Hülle ein Einschnitt zum Einstecken ein oder zweier Leiterstücke zur Bildung einer Abzweigung eingebracht worden ist,
• Fig. 3 den Kabelabschnitt nach Fig. 2 mit Darstellung der Art und Weise der Einsteckung zweier Leiterstücke, nachdem das Kabel an der Stelle des Einschnitts zwecks elastischer Aufweitung des Einschnitts gebogen wurde,
• Fig. 4 den Kabelabschnitt nach Fig. 2 und 3 nach Anbringung der beiden Letierstücke für die Abzweigung,
• Fig. 5 den Kabelabschnitt nach Fig. 4, bei dem die beiden aus dem Kabel vorstehenden Abschnitt der Leiterstücke verdrillt sind, mit Illustration einer möglichen Verschweißung der Abzweigung,
• Fig. 6 und 7 Möglichkeiten der Abdichtung der elektrischen Verbindung im Bereich der Abzweigung, entweder durch Umgießen (Fig. 6) oder mittels zweier isolierender Halbschalen (Fig. 7).

Further properties and advantages of the subject matter of the invention result from the following description of an exemplary embodiment of the subject matter of the invention, which takes place with reference to the attached drawing. Show in the drawing.

• 1 is an electrical cable insulated with a continuous sheath, which is provided with several branches by means of the method according to the invention,
• 2 shows a cable piece, in the casing of which an incision has been made to insert one or two conductor pieces to form a branch,
• 3 shows the cable section according to FIG. 2 with an illustration of the manner in which two conductor pieces are inserted after the cable has been bent at the point of the cut for the purpose of elastic expansion of the cut, FIG.
• 4 shows the cable section according to FIGS. 2 and 3 after attaching the two Letier pieces for the branch,
• 5 shows the cable section according to FIG. 4, in which the two sections of the conductor pieces protruding from the cable are twisted, with an illustration of a possible welding of the branch,
• 6 and 7 possibilities of sealing the electrical connection in the area of the branch, either by casting (Fig. 6) or by means of two insulating half-shells (Fig. 7).

2 shows a section of an electrical cable 1 which has a conductive core 2, which is formed, for example, from a wire strand 3 and which is surrounded by a continuous insulating sheath 4. A cut 5 in the form of a cylindrical segment is machined into the insulating sheath 4, which gives access to the conductive core 2 and defines the lips 6 and 7.

As can be seen from FIG. 3, the cable section according to FIG. 2 is subjected to an inclination of approximately 90 ° in order to elastically remove the lips 6 and 7 from one another and thus to facilitate the insertion of one or more conductor pieces which are to form the branch. If the branch is produced using only a single conductor section, this is inserted into the incision 5 in a position as shown by the conductor section 8. The end 10 of this conductor piece is then bent up and then takes the position as shown in Fig. 4.

If the branch is constructed from two conductor pieces 8 and 9, as shown in the exemplary embodiment, these conductor pieces are inserted one after the other, as can be seen from FIG. 3. After inserting a portion of the conductor piece 9 under the sheath 4 with frictional sliding on the soul 2, the end 11 of this conductor piece 9 is first bent so that the insertion of the second conductor piece 8 is easily possible, as can be seen in FIG. 3. At the end of this process step, the conductor pieces are in longitudinal alignment of the core 2 in contact with it by means of the sections 12 and 13, while the ends 10 and 11, which are then at right angles, are adjacent to each other, as shown in fig. 4 can be seen. The two ends 10 and 11 can be firmly connected to one another, for example by twisting, as shown in FIG. 5.

5 shows the electrical cable 1 as it is bent back into its straight original position, a branch 15 formed by twisting and consisting of the united ends 10 and 11 of the conductor pieces 8 and 9 being formed.

Fig. 1 shows the possibility of providing a plurality of corresponding branches 15 on a continuous cable 14.

The incision 5 can be made by grinding or by piercing or piercing using a suitable tool.

The conductor pieces 8 and 9 can be adapted to the problem to be solved in each case. In the exemplary embodiment shown, they have a rectangular cross section, their width defining the contact area with the conductive core and their thickness determining the strength of the insertion and the clamping between the sheath 4 and the core 2, on the one hand, and the possible current intensity of the current to be branched, on the other hand.

For certain applications on cables of 8 mm ² cross section (120 single stranded wires of 30/100 mm), sections 12 and 13 have a length of the order of 30 mm, for example. 5, the two ends 10 and 11 are twisted together and cut to length. However, they can also be covered with a common cable lug to be crimped and can be electrically connected in this way.

Although the insulating sleeve 4 is close to the The circumference of the ends 10 and 11 of the conductor pieces, which protrude from the sheath, the tightness can be improved even further, if, for example, cable branches are to be used in damp locations by applying a sealant locally in the area of the incision.

Another possibility of forming a seal in the area of the connection between the cable 1 and the conductor pieces 8 and 9 is shown in FIG. 6. The line piece 8 is insulated by a sheath 21 in its area which has not been used to form the connection. A encapsulation 22 surrounds the entirety of the connection zone and ensures tightness both on the sheath 4 of the cable 1 and on the sheath 21 of the conductor piece 8.

Another way of forming a seal is shown in FIG. 7. The conductor piece 8 is insulated by a sheath 21 in the area which has not been used to form the connection. Two insulating half-shells 23 and 24, which are connected to one another, isolate the entirety of the connection zone.

For a good insertion of the sections of the conductor pieces between the sleeve and the core, the cable should have a certain flexibility. The cable can have a simple insulating sheath or a sheath made of a composite material. It can also be considered in certain applications to give sections 12 and 13 a cylindrical segment-shaped profile in order to achieve an optimal contact area with the conductive core of the cable.

In certain applications, it may be necessary to strengthen the electrical and mechanical bond between the conductor pieces forming the branch and the core of the cable, for reasons of the current intensity which is to flow through the branch or for reasons of particularly high tensile loads can act on the junction.

The branch according to the invention prepares for reinforcement by welding in a particularly simple manner. For example, a method of working can be selected which includes direct heating through the Joule effect.

Whichever procedure is used, tin and a paper remover must be placed in the place of the incision at the passage of the conductor pieces forming the branch. This approach can, as illustrated in Fig. 5, by means of a wire 16 or the like. happen.

After local preheating at the level of the branch, the twisted branch piece 15 is clamped as close as possible to the point of the branch between two graphite electrodes 17 and 18, which are connected to conductors 19 and 20 of a circuit through which heavy current flows. Local warming continues through heat conduction to soul 2. The end of the wire 16 melts and the tin is gravitationally infiltrated between the two sections 12 and 13 of the conductor pieces and the core of the cable.

It is understood that the additional process of welding requires the use of an insulating sleeve 4, for example made of an elastomer or a thermoplastic elastomer, which resists the local temperature increase.

Among the numerous possible uses of the invention, the cabling of electrical control cabinets should be mentioned, in which this procedure enables considerable time and cable material to be saved, as well as the location of the branches being very convenient and easy to determine.

In a further embodiment, the corresponding ends of the conductor pieces can also be tinned to prepare for welding.

If the formation of the branch by means of two lettering pieces was assumed in the above description of the example, it goes without saying that the branch can also be formed from one or more than two conductor pieces.

It should also be particularly pointed out that the method according to the invention enables the use of multiple forms of implementation which can be adapted to a particular degree to the connection problem to be solved in each case. This applies in particular to the choice of the profile of the incision made in the insulating sheath, the thickness of this sheath, the cross section of the conductor pieces, the length of the sections of the conductor pieces inserted between the core and the sheath, the type of connection of the protruding from the sheath and the branch forming parts of the conductor pieces and the fact and / or the type of welding of the inserted sections with the core of the cable.

Numerous equivalent embodiments are possible within the scope of the inventive concept. It is particularly noteworthy that practice has shown that branches produced by the method according to the invention can be loaded with currents which can be considerable in relation to that which prevails in the central cable.

Claims (16)

1. A method of making branches in an electric cable (1) having a core (2) insulated by a continuous sheath (4), wherein an electric connecting point is formed at a branching point of the cable and wherein the sheath is opened in the region of the branching point and a conductor element (8,9) inserted through the opening into the interior of the sheath, characterised in that the sheath (4) is opened by means of an incision (5), giving access to the e!ectri.:aiiy conductive part of the core (2) of the cable (1), and the conductor element (8,9) is inserted, with friction through the incision (5), between the electrically conductive part of the core (2) of the cable (1) of the insulating sheath (4), in such a way that the conductor element (8,9) is laid against and is in contact with the electrically conductive part of the core (2) over a predetermined length of the cable (1).

2. The method of claim 1, characterised in that before the conductor element (8,9) is inserted through the incision (5), the cable is bent through approximately 90° at the location of the incision (5), in such a way that the incision (5) lies on the outer arc of the bend.

3. The method of claim 1 or claim 2, characterised in that a conductor element (8,9) with a substantially rectangular cross-section is used.

4. The method of any of the preceding claims, characterised in that the end (10,11) of the conductor element (8,9) projecting outside the cable (1) is bent away from the longitudinal axis of the cable.

5. The method of any of the preceding claims, characterised in that two conductor elements (8 and 9) are inserted in opposite directions through the access formed by the incision (5), and their ends (10 and 11) projecting from the cable (1) are electrically interconnected.

6. The method of claim 5, characterised in that the ends (10 and 11) of the conductor elements are twisted together to effect their electrical connection.

7. The method of any of claims 1 to 4, characterised in that the conductor element (8,9) is additionally electrically connected to the cable (1) by welding.

8. The method of claim 5 to 6, characterised in that the conductor elements (8 and 9) are electrically connected to one another and additionally to the cable (1) by welding.

9. The method of claim 7 or 8, characterised in that the welding is carried out, after local preheating, by adding tin and a pickling medium at the place of the incision (5), and by clamping the ends (10,11) of the conductor elements projecting from the cable, as near as possible to the branching point, between two graphite electrodes (17,18), which may be fed with high voltage current.

10. The method of any of claims 7 to 9, characterised in that the conductor element or elements (8,9) are tin plated.

11. The method of any of the preceding claims, characterised in that the incision (5) is closed with a jointing compound.

12. The method of any of claims 1 to 10, characterised in that the region of the connection between the electric cable (1) and the conductor or conductors (8,9), forming the branch, is cast around with a jointing compound.

13. The method of any of claims 1 to 10, characterised in that the region of the connection between the electric cable (1) and the conductor element or elements (8,9), forming the branch, is sealed by placing together two insulating half shells (23,24).

14. The method of any of the preceding claims, characterised in that the incision (5) is formed by grinding the insulating sleeve (4) of the cable (1).

15. The method of any of claims 1 to 13, characterised in that the incision (5) is formed by puncturing with an implement.

16. The method of any of the preceding claims, characterised in that at least that part of the conductor element (8,9) which is inserted between the conductive core (2) and the insulating sheath (4) of the cable (1) has a transverse profile matching that of the conductive core (2).

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