Connection for heating cable

Abstract

 The present invention relates to electrical heating cables and in particular to provision of an improved heating cable conductor joint, - prior to application of common outer sheaths over the conductors and the joints. Such joint includes butt-jointing end portions of two electrical conductors having different diameters, in particular for jointing a heating cable resistance conductor to a cold end copper conductor and vice versa.
The invention includes reducing the diameter of the end portion (3) of the larger conductor (2) before abutting the ends (1,3) of the two conductors and jointing the two conductor ends. The diameter should be reduced so that the diameter over a crimp jointing element (4) crimped over the conductor ends does not exceed the diameter of the larger conductor.

Description

[0001] The present invention relates to electrical heating cables and in particular to provision of an improved heating cable conductor joint, - prior to application of common outer sheaths over the conductors and the joints. Such joint includes butt-jointing end portions of two electrical conductors having different diameters, in particular for jointing a heating cable resistance conductor to a cold end copper conductor and vice versa.

[0002] The technical problem has been solved with soldering technique in accordance with our US Patent No 4,518,445 (J Pedersen 5-10). The object of the present invention is to improve the jointing technique for heating cable conductors. The main features of the invention appears from the claims.

[0003] With the invention we have obtained a simple and inexpensive joint which fully meets all requirements to such joints.

[0004] Above mentioned and other features and objects of the present invention will clearly appear from the following detailed description of embodiments of the invention taken in conjunction with the drawings, where

Figure 1-4 illustrate four stages in preparing the improved heating cable conductor joint,

Figure 5 is a crossection of Figure 3, and

Figure 6 shows a crimp element.

[0005] In Figure 1 a resistance conductor 1 has a smaller diameter than the (cold) copper conductor 2. In Figure 2 the end portion 3 of the larger diameter conductor 2 has been reduced in diameter. Such reduction can be done by means of a milling, rolling, forging or other mechanical process. The diameter should be reduced so that the diameter over a crimp jointing element 4 (Figure 3) crimped over the conductor ends 1 and 3 does not exceed the diameter of the larger conductor 2. The diameter of said end portion could be reduced to substantially the same diameter as that of the smaller conductor.

[0006] The crimp element 4 is crimped onto the conductor ends as indicated with arrows 5. An improved joint breaking strength may be obtained by heat treating the crimped joint. In Figure 4 is indicated that the heating cable conductors including the conductor 1, the crimp joint 4 and the conductor 2 are covered with a common continuous sheath of insulation material.

[0007] Figure 5 is a cut through line V-V in Figure 3, whereas Figure 6 illustrates a crimp element.

[0008] Whereas the cold end conductor 2 normally is a copper wire, the resistance conductor 1 can be a Ni/Cr/Mn alloy wire. With a resistance wire being some 0.25 mm in diameter, - a copper wire with a 1.13 mm diameter (1 mm²) could be reduced to some 0.5 mm, whereas with a 0.93 mm resistance wire the 1.13 mm copper wire could be reduced to 1.0 mm. Good results have been obtained with a bronze crimp element.

[0009] As this type of heating cable is manufactured in continuous lengths and thereafter cut into individual installation lengths each having a middle resistance conductor portion and two cold end portions, remedies will have to be put on the conductor at or near each joint to ensure that cutting is made substantially in the middle of each cold section. Such remedies which are well known can be combined with the crimp joint.

[0010] The above detailed description of embodiments of this invention must be taken as examples only and should not be considered as limitations on the scope of protection.

Claims

1. Method for crimp-jointing end portions of two electrical conductors (1,2) having different diameters, in particular for jointing a heating cable resistance conductor to a cold end copper conductor and vice versa, prior to application of common outer sheaths over the conductors and the joints, characterized by reducing the diameter of the end portion (3) of the larger conductor (2) before abutting the ends (1,3) of the two conductors and jointing the two conductor ends.

2. Method according to claim 1, characterized by reducing the diameter of said end portion so that the diameter over a crimp jointing element (4) crimped over the conductor ends does not exceed the diameter of the larger conductor.

3. Method according to claim 1, characterized by reducing the diameter of said end portion to substantially the same diameter as that of the smaller conductor.

4. Method according to claim 1, characterized by making said diameter reduction by means of a milling, rolling, forging or other mechanical process.

5. Method according to claim 1, characterized by heat treating the crimped joint.

6. Joint between two electrical conductors (1,2) having different diameters, in particular between a heating cable resistance conductor and a cold end copper conductor and vice versa, characterized in that an end portion (3) of the larger conductor (2) has a reduced diameter so that the diameter over a crimp jointing element (4) crimped over the conductor ends does not exceed the diameter of the larger conductor.

7. Joint according to claim 6, characterized in that the diameter of said end portion is reduced to substantially the same diameter as that of the smaller conductor.

Drawing