GB1589608A

GB1589608A - Method of making an electrical cable joint calbe joint made by said method and mould for putting said method into practice

Info

Publication number: GB1589608A
Application number: GB3439277A
Authority: GB
Original assignee: IJZERGIETERIJ LOVINK BV
Current assignee: IJZERGIETERIJ LOVINK BV
Priority date: 1976-08-16
Filing date: 1977-08-16
Publication date: 1981-05-13
Also published as: NL171506B; NL171506C; BE857841A; DE2736803C2; NL7609087A; DE2736803A1; FR2362510B1; FR2362510A1

Description

(54) A METHOD OF MAKING AN ELECTRICAL CABLE JOINT, CABLE JOINT MADE BY SAID METHOD AND MOULD FOR PUTTING SAID METHOD INTO PRACTICE (71) We, IJZERGIETERIJ LOVINK B.V., a company organized under the laws of The Netherlands, of Lovinkweg 3, Terborg, The Netherlands, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a method of making an electrical cable joint, in which the ends of two electrical cables having insulating sheaths are fixed in a cable sleeve, the respective conductors interconnected, and, the cable sleeve filled with settable insulant.

A known method for jointing electrical cables comprises stripping the insulation from the conductors of the two cable ends, bending the conductors apart to separate them, connecting the respective conductors, fitting a divided cast-iron cable sleeve around the joint, and filling the sleeve with a liquid bituminous insulant, which is solid at ambient temperature. This method yields good results although shrinkage when the insulant sets may cause cavities to form in the cable sleeve and these have to be filled subsequently since otherwise the insulation is inadequate. A thermoplastic bituminous mixture was initially used as insulant, but now a thermosetting casting resin is also used. However the problem occurring with this latter material is that the casting resin sets later near parts having a high thermal capacity or which allow a high heat dissipation, than at other places where the casting resin is heated by the reaction heat evolved, so that cavities form as a result of the inevitable shrinkage at the coldest places.

One of the places where this phenomenon occurs is between the separated conductors and even a miniscule cavity is unacceptable here.

According to the present invention we provide a method of making an electrical cable joint, by fixing the ends of two electrical cables having insulating sheaths in a cable sleeve, interconnecting the respective conductors, and filling the cable sleeve with liquid insulant, which subsequently sets; wherein an elastomeric casting mould is fitted around the end of each of the insulating sheaths and the adjacent parts of the conductors of each cable, each casting mould having a filling aperture, an aperture fitting in sealing-tight relationship around the insulating sheath, and a number of apertures, corresponding to the number of conductors, fitting in sealing-tight relationship around the conductors, whereupon the cables are interconnected, each casting mould is filled with liquid thermosetting insulant, each casting mould is removed, if required, after the solidification of the insulant, and the cable sleeve is completely filled with the first mentioned liquid insulant.

It is advantageous to fix the cables in the cable sleeve before filling the casting moulds.

In order to facilitate the removal of the casting moulds, if required, the casting moulds used generally are such that the inner surfaces and the solidified insulant do not adhere to one another. To ensure that there are no seams remaining between the succesively applied quantities of insulant, it is advantageous to clean each casting mould or the solidified insulant after the casting mould has been removed, where applicable, in order to improve the adhesion thereto of the insulant subsequently applied inside the cable sleeve. It is also advantageous to use the same insulant for filling the casting moulds and the cable sleeve as we have found that the best results are obtained when using as few different materials as possible.

To reduce the time between filling the casting moulds and filling the cable sleeve, it is desirable to use a rapid-setting insulant for filling the casting moulds, and for this purpose a higher proportion of curing agent and/or accelerator is/are added to this material than to the material for filling the cable sleeve.

Another aspect of the invention provides a casting mould for use in the above method according to the invention, which casting mould comprises a hollow elastomeric mould having at one end an aperture in which a cable end can fit in sealing-tight relationship, a number of apertures situated at the opposite end of the mould, in each of which a cable conductor can fit in sealingtight relationship, and a filling aperture in the mould wall between the said ends. To avoid damage to the casting mould when it is fitted around a cable end and in order to obtain good sealing around the insulating sheath and around the conductors, externally projecting collars having substantially the same internal dimensions as the apertures are preferably provided around the apertures. In a casting mould construction which has proved satisfactory in practice, the mould is of cylindrical shape, with the apertures for the cable end and the apertures for the conductors in the end walls and with the filling aperture in the cylindrical wall.

In order that the invention may be more fully understood, a preferred embodiment in accordance therewith will now be described, by way of example only, with reference to the following drawings, in which: Figure 1 is a partially cutaway view of a cable sleeve not yet closed and before filling with insulant.

Figure 2 is an enlarged-scale longitudinal section through a casting mould as shown in Figure 1.

Figure 3 is an axial view of the mould according to Figure 2.

Figure 4 is a cross-section through the mould on the line IV-IV of Figure 3.

Figure 1 shows a partially cutaway and not yet closed cable sleeve comprising a bottom part 1 and a top part 2. Two cable ends 3 are clamped fast in the bottom part by means of conventional clips 4. Prior to jointing the stripped conductors 5 (three per cable in the case illustrated), an elastomeric casting mould 6 is slipped over each cable end and encloses just the end of the insulating sheath and the adjacent parts of the separated conductors 5. The respective conductors of the cable ends are then electrically interconnected by suitable clamping means 7.

When the cable ends 3 have been completely fixed in the bottom part 1, the two casting moulds are filled with a thermosetting insulating resin. which is caused to set.

As soon as the resin has set, the moulds 6 are removed and the outer surface of the resin is cleaned if necessary. After the top part 2 of the cable sleeve has been placed on the bottom part and fixed, it is filled through the top opening with thermosetting insulating resin which adheres to the resin applied previously.

The casting moulds 6 used for applying the relatively small quantity of casting resin around the cable ends consist of a hollow cylindrical mould of elastomeric material, with a filling aperture 9 in a cylindrical wall, with upright edges 10 around said aperture.

An aperture 11 is formed in one of the end walls and the cable end 3 with its insulation fits in sealing-tight relationship therein. An external collar 12 is provided around this aperture 11. The other end wall has three apertures 13, in which the conductors 5 of the cable fit in sealing-tight relationship.

External collars 14 are also provided around these apertures. The capacity of the casting moulds is, of course, dependent upon the cable thickness, but should be so small that there is no appreciable temperature rise of the casting resin as a result of the thermal capacity of the conductors during setting. In practice, the casting mould capacity will be such that after the casting mould has been fitted around a cable end the quantity of casting resin that can be introduced into the mould is of the order of some tens of millilitres.

Although the drawing shows a cable with three conductors 5 and hence casting moulds 6 with three apertures 13 on one side, casting moulds having a certain number of apertures on one side will of course be used for jointing a cable having that particular number of conductors, e.g. four apertures for a four conductor cable.

In the above description of the drawing it was stated that the casting moulds 6 are removed after the casting resin has set therein. Alternatively, the casting moulds can be left in position and can be joined with the casting resin used to fill the cable sleeve.

WHAT WE CLAIM IS: 1. A method of making an electrical cable joint, by fixing the ends of two electrical cables having insulating sheaths in a cable sleeve, interconnecting the respective conductors, and filling the cable sleeve with liquid insulant, which subsequently sets; wherein an elastomeric casting mould is fitted around the end of each of the insulating sheaths and the adjacent parts of the conductors of each cable, each casting mould having a filling aperture, an aperture fitting in sealing-tight relationship around the insulating sheath, and a number of apertures corresponding to the number of conductors fitting in sealing-tight relation

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

casting moulds and filling the cable sleeve, it is desirable to use a rapid-setting insulant for filling the casting moulds, and for this purpose a higher proportion of curing agent and/or accelerator is/are added to this material than to the material for filling the cable sleeve.

Another aspect of the invention provides a casting mould for use in the above method according to the invention, which casting mould comprises a hollow elastomeric mould having at one end an aperture in which a cable end can fit in sealing-tight relationship, a number of apertures situated at the opposite end of the mould, in each of which a cable conductor can fit in sealingtight relationship, and a filling aperture in the mould wall between the said ends. To avoid damage to the casting mould when it is fitted around a cable end and in order to obtain good sealing around the insulating sheath and around the conductors, externally projecting collars having substantially the same internal dimensions as the apertures are preferably provided around the apertures. In a casting mould construction which has proved satisfactory in practice, the mould is of cylindrical shape, with the apertures for the cable end and the apertures for the conductors in the end walls and with the filling aperture in the cylindrical wall.

In order that the invention may be more fully understood, a preferred embodiment in accordance therewith will now be described, by way of example only, with reference to the following drawings, in which: Figure 1 is a partially cutaway view of a cable sleeve not yet closed and before filling with insulant.

Figure 2 is an enlarged-scale longitudinal section through a casting mould as shown in Figure 1.

Figure 3 is an axial view of the mould according to Figure 2.

Figure 4 is a cross-section through the mould on the line IV-IV of Figure 3.

Figure 1 shows a partially cutaway and not yet closed cable sleeve comprising a bottom part 1 and a top part 2. Two cable ends 3 are clamped fast in the bottom part by means of conventional clips 4. Prior to jointing the stripped conductors 5 (three per cable in the case illustrated), an elastomeric casting mould 6 is slipped over each cable end and encloses just the end of the insulating sheath and the adjacent parts of the separated conductors 5. The respective conductors of the cable ends are then electrically interconnected by suitable clamping means 7.

When the cable ends 3 have been completely fixed in the bottom part 1, the two casting moulds are filled with a thermosetting insulating resin. which is caused to set.

As soon as the resin has set, the moulds 6 are removed and the outer surface of the resin is cleaned if necessary. After the top part 2 of the cable sleeve has been placed on the bottom part and fixed, it is filled through the top opening with thermosetting insulating resin which adheres to the resin applied previously.

The casting moulds 6 used for applying the relatively small quantity of casting resin around the cable ends consist of a hollow cylindrical mould of elastomeric material, with a filling aperture 9 in a cylindrical wall, with upright edges 10 around said aperture.

An aperture 11 is formed in one of the end walls and the cable end 3 with its insulation fits in sealing-tight relationship therein. An external collar 12 is provided around this aperture 11. The other end wall has three apertures 13, in which the conductors 5 of the cable fit in sealing-tight relationship.

External collars 14 are also provided around these apertures. The capacity of the casting moulds is, of course, dependent upon the cable thickness, but should be so small that there is no appreciable temperature rise of the casting resin as a result of the thermal capacity of the conductors during setting. In practice, the casting mould capacity will be such that after the casting mould has been fitted around a cable end the quantity of casting resin that can be introduced into the mould is of the order of some tens of millilitres.

Although the drawing shows a cable with three conductors 5 and hence casting moulds 6 with three apertures 13 on one side, casting moulds having a certain number of apertures on one side will of course be used for jointing a cable having that particular number of conductors, e.g. four apertures for a four conductor cable.

In the above description of the drawing it was stated that the casting moulds 6 are removed after the casting resin has set therein. Alternatively, the casting moulds can be left in position and can be joined with the casting resin used to fill the cable sleeve.

WHAT WE CLAIM IS:

1. A method of making an electrical cable joint, by fixing the ends of two electrical cables having insulating sheaths in a cable sleeve, interconnecting the respective conductors, and filling the cable sleeve with liquid insulant, which subsequently sets; wherein an elastomeric casting mould is fitted around the end of each of the insulating sheaths and the adjacent parts of the conductors of each cable, each casting mould having a filling aperture, an aperture fitting in sealing-tight relationship around the insulating sheath, and a number of apertures corresponding to the number of conductors fitting in sealing-tight relation

ship around the conductors, whereupon the cables are interconnected, each casting mould is filled with liquid thermosetting insulant, each casting mould is removed, if required, after the solidification of the insulant, and the cable sleeve is completely filled with the first mentioned liquid insulant.

2. A method according to Claim 1 wherein the cables are fixed in the cable sleeve before filling the casting moulds.

3. A method according to Claim 1 or 2, wherein a casting mould is used having an inner surface not adhering to the solidified insulant.

4. A method according to any one of the preceding claims wherein the solidified insulant is cleaned after removal of the casting moulds in order to improve the adhesion thereto of the insulant with which the cable sleeve is subsequently filled.

5. A method according to any one of the preceding claims, wherein the first and second mentioned insulants are the same.

6. A method according to Claim 5, wherein a rapid setting insulant is used for filling the casting moulds.

7. A method as claimed in Claim 5 or 6, wherein a higher proportion of curing agent and/or accelerator is/are added to the insulant for filling the casting moulds than to the insulant for filling the cable sleeve.

8. An electrical cable joint obtained by using the method of one of the preceding claims.

9. A casting mould for use in the method of any one of Claims 1 to 7, comprising a hollow elastomeric mould having at one end an aperture in which a cable end can fit in sealing-tight relationship, a number of apertures situated at the opposite end of the mould in each of which a cable conductor can fit in sealing-tight relationship, and a filling aperture in the mould wall between the said ends.

10. A casting mould according to Claim 9, wherein externally projecting collars having substantially the same internal dimensions as the apertures are provided around the apertures.

11. A casting mould according to Claim 9 or 10, wherein the mould is of cylindrical shape, with the apertures for the cable end and the apertures for the conductors in the end walls and with the filling aperture in the cylindrical wall.

12. A method of making an electrical cable joint, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.

15. A casting mould according to Claim 9 substantially as described with reference to and as illustrated in the accompanying drawing.