ELECTRICAL LEAD

Abstract

An electrical lead has a lead core composed of a plurality of individual conduction elements and surrounded by a jacket of multiple plies that are formed by extrusion. An inner ply is formed of a swellable material. An outer ply surrounds the inner ply. Upon penetration of moisture, the swellable material of the inner ply swells up and fills out interstices between the conduction elements.

Claims

1. An electrical lead, comprising: a lead core formed of a plurality of individual conduction elements; a jacket formed of a plurality of plies surrounding said lead core, said plurality of plies of said jacket including an inner ply directly surrounding said lead core and an outer ply surrounding said inner ply, said inner and outer plies being extruded plies; said inner ply being formed of a swellable material, which, upon moisture penetration, swells up and fills out interstices between said conduction elements.

2. The electrical lead according to claim 1, wherein said outer ply consists of a material that is harder than the material of said inner ply.

3. The electrical lead according to claim 2, wherein said outer ply is harder by a factor of at least 2 than said inner ply.

4. The electrical lead according to claim 1, wherein said inner ply has a Shore hardness in a range from 35 Shore A to 50 Shore D.

5. The electrical lead according to claim 1, wherein said outer ply has a Shore hardness in a range from 92 Shore A to 85 Shore D.

6. The electrical lead according to claim 1, wherein said inner ply has a first wall thickness and said outer ply has a second wall thickness, said second wall thickness being greater than said first wall thickness.

7. The electrical lead according to claim 1, wherein said inner ply consists of a compounded formulation comprising a superabsorbent and a thermoplastic material.

8. The electrical lead according to claim 7, wherein a fraction of said superabsorbent within said compounded formulation is in a range from 10 vol % to 80 vol %.

9. The electrical lead according to claim 7, wherein said thermoplastic material of said compounded formulation comprises an ethylene-vinyl acetate.

10. The electrical lead according to claim 7, wherein said compounded formulation is composed of: 35 vol % to 55 vol % of said superabsorbent; 40 vol % to 65 vol % of said thermoplastic material; and 0 to 25 vol % of additional substances.

11. The electrical lead according to claim 1, wherein said outer jacket consists of a thermoplastic material.

12. The electrical lead according to claim 11, wherein said thermoplastic material is high-density polyethylene.

13. The electrical lead according to claim 1, wherein said lead core is a stranded conductor and said individual conduction elements are individual strand wires.

14. The electrical lead according to claim 1, wherein said lead core consists of a plurality of cores forming said conduction elements, each said core being formed by a conductor and a surrounding insulation.

15. The electrical lead according to claim 1, wherein said outer jacket directly surrounds said inner jacket and is in contact therewith.

16. The electrical lead according to claim 1, wherein said outer jacket is an exterior jacket.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0039] FIG. 1 shows a cross section through a lead in the original state with an inner ply composed of a swellable material, and

[0040] FIG. 2 shows a cross section of the lead of FIG. 1 in the case where moisture has penetrated into the interior of the lead and the material of the inner ply is swollen.

DETAILED DESCRIPTION OF THE INVENTION

[0041] Referring now to the figures of the drawing in detail, there an exemplary embodiment of an electrical lead 2, which comprises a lead core 4 surrounded by a jacket 6. The jacket 6 is configured as a two-ply jacket, having an inner ply 6A and an outer ply 6B. The inner ply 6A surrounds the lead core 4 directly, and specifically in the manner of a flexible tube. The outer ply 6B surrounds the inner ply 6A, again directly. The lead 2 as a whole has an outer diameter D which is typically in the range from 0.5 to 5 mm, or else more.

[0042] The lead core 4 is formed by a plurality of conduction elements 8. In particular, the lead core 4 has at least two, preferably at least four, conduction elements 8. Usefully, a plurality of plies of conduction elements 8 are formed. In the exemplary embodiment depicted, a two-ply construction of the lead core 4 is shown, having a central conduction element 8, which, so to speak, forms the inner ply, and an outer ply consisting of six conduction elements 8. In the exemplary embodiment, the lead core 4 is formed specifically by a stranded conductor and the individual conduction elements 8 are configured as individual stranded wires, which preferably all in all form a stranded assembly. Alternatively, the conduction elements 8 used are cores.

[0043] The inner ply 6A has a first wall thickness w1 and the outer ply has a second wall thickness w2. The second, outer wall thickness w2 is preferably greater than the first, inner wall thickness w1.

[0044] The inner ply 6A consists of a swellable material which swells up on penetration of moisture. The hardness of this swellable material is preferably much lower than the hardness of the material of the outer ply 6B.

[0045] Specifically, for the inner ply, a compounded formulation is used that is composed of a superabsorbent with a thermoplastic elastomer. The volume fraction of the superabsorbent is usefully about 50 vol %, and the volume fraction of the thermoplastic elastomer, more particularly EVA (ethylene vinyl acetate), is 40 vol % to 50 vol %.

[0046] For the outer layer 6B, in turn, a comparatively hard material is used, as for example a polyamide (PA), a rigid PVC, a polyester elastomer, or an HDPE (high-density polyethylene).

[0047] As a result of this construction, and especially of the choice of the higher hardness for the outer ply 6B, specifically also in combination with the greater wall thickness, it is ensured in the event of moisture penetration that the material of the inner ply 6A undergoes inward expansion, at least primarily and preferably exclusively, and hence that interstices 10 between the individual conduction elements are reliably filled out with the material of the inner ply.

[0048] The latter condition is shown in FIG. 2. Here it is clearly apparent that all of the interstices 10 are filled out with the swellable material of the inner ply 6A. As a result, longitudinal water imperviousness (imperviosity) is ensured.

[0049] Studies have shown that with the construction described herein, it is possible to achieve the longitudinal water imperviosity of DIN EN 60794-1-22 (method F5B).