WO1993009547A1

WO1993009547A1 - Electrical cable having multiple individually coated conductor strands

Info

Publication number: WO1993009547A1
Application number: PCT/US1992/009343
Authority: WO
Inventors: Peter Keith Townsend
Original assignee: E.I. Du Pont De Nemours And Company
Priority date: 1991-11-06
Filing date: 1992-11-02
Publication date: 1993-05-13

Abstract

An electrical cable (10) has an inner core (14) formed from a plurality of individual strands of wire conductor (16). At least some of the strands of wire conductor are coated with a layer (18) of a metallic material. The conductors are grouped into a generally circular locus centered on the axis of the cable to form a core with portions of at least some of the wire conductors cooperating to define an exterior peripheral surface of the core (20). A second layer (30) of metallic material is disposed on the outer peripheral surface of the core.

Description

TITLE ELECTRICAL CABLE HAVING MULTIPLE INDIVIDUALLY COATED CONDUCTOR STRANDS

BACKGROUND OF THE INVENTION

Field of the Invention The present invention relates to an electrical cable and, in particular, to an electrical cable having a core formed from multiple strands of individual wire conductors, at least some of the strands of individual wire conductors having a coating of a metal lic material thereon.

Description of the Prior Art Wire terminations of the insulation displacement type are well known i n the art. Un i ted

States Patent 4,583,29 ! (Lemke et al.) and United States Patent 4,73 1 ,247 (Fusselman et al.) each disclose an insulation displacement contact. Such a contact includes a pair of spring tines cooperating to define a central channel , or bight. The transverse dimension of the bight of the insulation displacement contact is sized to be sl ightly less than the outer diameter of the cable core. When an electrical cable is introduced into the bight of the insulation displacement contact, with the axis of the core extending substantial ly perpendicularly to the plane containing the tines of the contact, the insulating jacket of the cable is parted by the inner edge of the tines, thus placi ng the ti nes in electrical ly conducti ve contact with the conducti ve core of the cable and forming a gas-tight seal between the ti nes and the cable core.

An i nsu lation displacement contact i s used with cables having a core formed either of a single sol id wire conductor strand or with a core formed from plural wire conductor strands that have been compressed into a generally sol id core. An example of this latter form of cable is disclosed in United States Patent 4,648,673 (Endo et al.).

An electrical cable having a core formed from multiple individual strands of wire conductor that have not been compressed to form a solid core is believed unable to be terminated using an insulation displacement contact. Figure 1 is a front sectional view of an insulation displacement contact showing the result when a prior art electrical cable C having a jacket J and a core formed from multiple wire conductor strands W l through Wn is introduced into the bight B defined between the tines TI , T2 of the insulation displacement contact. As the jacket J of the cable C is parted by the action of the tines the individual strands of wire conductors in the cable C assume an arrangement in whic the wire conductors conform to the generally rectangular configuration of the bight. As a result a gas-tight seal between the conductor wires and the material of the tines cannot effectively be formed-

It is believed that the tendency of the individual strands of a cable to conform to the shape of the bight of the contact may occur even with an electrical cable having a core formed of compressed multiple strands of wire conductors.

Accordingly, in view of the foregoing, it is believed desirable to provide a cable having a core formed from multiple strands of wire conductors that is amenable to effective use with an -insulation displacement contact to form a gas-tight seal therewith.

SUMMARY OF THE INVENTION

The present invention relates to an electrical cable havin tg an outer insulating jacket and an inner core. The inner core is formed from a plurality of individual strands of wire conductor grouped into a generally circular locus centered on the axis of the cable. At least some, but more preferably al l, of the strands of wire conductor are coated with a layer of a metallic material. Portions of at least some of the wire conductors cooperating to define an exterior peripheral surface of the core . A second layer of metallic material is disposed on the outer peripheral surface of the core. The metallic material forming the first and second coating layers is preferably tin/lead solder. The core of the resulting cable is generally cylindrical in cross- sectional configuration and maintains this confi guration when the cable is introduced into the bight of an insulation displacement contact.

In another aspect the invention relates to a method for forming an electrical cable comprising the steps of coal ing at least some, but preferably al l , of a plural ity of strands of wire conductor with a layer of a metallic material, such as tin/lead solder, and grouping the plurality of individual strands of wire conductor into a generally circular locus centered on the axis of the cable to form a core. At least some of the wire conductors i n the group cooperate to define an exterior peri pheral surface of the core. A second layer of metallic material is coated on the outer peripheral surface of the core, and, thereafter, an insulating jacket is formed about the coated outer peripheral surface of the core.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more ful ly understood from the fol lowing detailed description thereof taken i n connecti on wi th the accompanying drawings, which form a part of this application, and in which:

Figure 1 is front sectional view of an insulation displacement contact with a prior art electrical cable C having a core formed from multiple wire conductor strands introduced into the bight B of the insulation displacement contact;

Figure 2 is a sectional view of an electrical cable in accordance with the present invention taken in a plane transverse to the cable axis;

Figure 3 is a view similar to Figure 1 illustrating a cable in accordance with the present invention when received within the bight of an insulation displacement contact; and

Figure 4 is a diagrammatic view of a method of forming a cable in accordance with the present invention; and

DETAILED DESCRIPTION OF THE INVENTION

Throughout the following detailed description, similar reference numerals refer to similar elements in all figures of the drawings-

With reference to Figure 2 shown is a multi-stranded conductor cable generally indicated by reference character 10 in accordance with the present invention. The cable 10 includes an outer jacket 12 formed from an insulating material surrounding an inner core 14. The jacket 12 may, for example, be formed from poly vinyl chloride. The inner core 14 is comprised of a plurality of individual wire conductors each indicated by the reference character 16. Although any predetermined number of wire conductors may be used, in the preferred case the core 14 should include at least seven wire conductors 16ι through I67.

In accordance with this invention at least some, but preferably each of the individual strands of wire conductor 16j through 167 1s coated over some predetermined portion of its length with a layer 1 8 of a metallic material . The layer 1 8 of metallic material is on the order of 0.003 inch in thickness. The material forming the layer 1 8 is preferably tin/lead solder. The layer 18 may extend throughout the entire axial length of each of the wire conductor strands 16 or, alternatively, over some predetermined sublength thereof. Each coated wire conductor 16 has an exterior surface 20 thereon.

The plural strands of wire conductors 1 6 | through 1 67 are grouped or bundled to form the core 1 4. The wire conductors 16 are grouped into a generally circular locus centered on the axis 10A of the cable 10. Some or all of the strands of wire conductors 16 cooperate to define an outer shel l 24 of wire conductors, with the remainder forming an inner shell 26 of wire conductors. Portions of the exterior surface 20 of the wire conductors defining the outer shel l 24 cooperate to define an exterior peri pheral surface of the core 14. It should be noted that it lies within the contemplation of this invention that some subset of the strands forming the core 14 can be formed of a nonconducting material. Preferably, if used, such nonconducting strands are disposed in the inner shell 26 of the core 14.

In accordance with this invention a second, outer, layer 30 of metallic material is coated over the exterior peripheral surface of the wire conductors 1 6 formi ng the outer shel l 24. This outer layer 30 of metal lic material is on the order of 0.005 inch thick and is also preferably formed of ti n/lead solder.

The layer 1 8 coating on each of the conductors 1 6 serves to protect the surface and to improve electrical performance by inhibiting the formation of an oxide coating thereon. The outer layer 30 becomes integral with the layer 1 8 on the wi res 1 6 forming the outer shel l 24 and functions to secure together the wire conductors 16 forming the core 14.

A multi-conductor cable 10 in accordance with the present invention is amenable for use with an insulation displacement contact. Owing to the presence of both the metallic layer 18 coated onto the individual strands of wire conductor 16 forming the core and to the outer metallic layer 30 provided over the peripheral surface of the core, the generally cylindrical configuration of the core 14 is maintained when the cable 10 is introduced between the tines of an insulation displacement contact-

As is shown in Figure 3, when the multi-conductor cable is introduced into the bight of the insulation displacement contact, the material of the tines of the contact electrically engage with either the metallic material of the outer layer 30, the coated layer 18 on the individual wire conductors, or the material of the wire conductor 16 themselves. A gas-tight seal may thus be provided between the core of the cable and the tines of the contact.

In Figure 4 a highly stylized pictorial representation of the method steps used in forming a cable 10 in accordance with the present invention is shown. A plurality of reels 40ι through 407, each carrying an individual wire conductor 16 (typically 32 AWG) is arranged to feed a lay machine 42. The wire conductors may each be already coated with a layer 18 of tin/lead solder. If the wire conductors 16 are not already so coated, the wire conductor from the reel 40 is passed through a cleaner 44 and then to a tin/lead solder coating bath 46. The lay machine 42 serves to form the individual wire conductors 16 into a core 14 having serpentine configuration, as appreciated by those skilled in the art. The core has a typical gauge of 26 AWG. The core 14 then passes sequentially through a cleaner 46, a tin/lead bath 50 and a cleaner 52. The second coating layer 30 is applied to the core 14 by the bath 50. The resultant coated core 14 is covered by an insulating jacket in the coating apparatus 54.

Those skilled i n the art having the benefit of the teachings of the present invention as hereinabove set forth may effect numerous modifications thereto. Such modi fications are construed to lie within the contemplation of the present invention as defined by the appended claims.

Claims

WHAT IS CLAIMED IS:

1. An electrical cable comprising an outer insulating jacket and an inner core, the inner core being formed from a plurality of individual strands of wire conductor, characterized in that at least some of the strands of wire conductor are coated with a layer of a metallic material, the strands of wire conductor being grouped into a generally circular locus centered on the axis of the cable to define the core, portions of at least some of the strands of wire conductor cooperating to define an exterior peripheral surface of the core, an d a second layer of metallic material being disposed on the outer peripheral surface of the core.

2. The electrical cable of claim 1 wherein each of the strands of wire conductor is coated with a layer of metallic material.

3. The electrical cable of claim 2 wherein the metallic material coated on each of the strands of wire conductor is tin/lead solder.

4. The electrical cable of claim 1 wherein the metallic material coated on some of the strands of wire conductor is tin/lead solder-

5. The electrical cable of claim 2 wherein the second layer of metallic material disposed on the outer peripheral surface of the core is tin/lead solder.

6. The electrical cable of claim 1 wherein the second layer of metallic material disposed on the outer peripheral surface of the core is tin/lead solder.

7. A method of forming an electrical cable comprising the steps of:

a) coating at least some of a plurality of strands of wire conductor with a layer of a metallic material ,

b) grouping the plurality of individual strands of wire conductor into a general ly circular locus centered on the axis of the cable to form a core, at least some of the wire conductors in the group cooperating to define an exterior peripheral surface of the core,

c) coating a second layer of metallic material on the outer peripheral surface of the core, and

d) forming an insulating jacket about the coated outer peripheral surface of the core.

8. The method of claim 7 wherein each of the individual strands of wire conductor is coated with the metal l ic material .

9. The method of claim 8 wherein the metallic material coated on each of the individual strands of wire conductor is tin/lead solder.

10. The method of claim 7 wherein the metallic material coated on some of the individual strands of wire conductor is tin/lead solder.

1 1 . The method of claim 7 wherein the second layer of metallic material disposed on the outer peripheral surface of the core is tin/lead solder. 12- The method of claim 8 wherein the second layer of metallic material disposed on the outer peripheral surface of the core is tin/lead solder.