Water resistant cable construction

• US 5,043,538 A
• Filed: 07/03/1989
• Issued: 08/27/1991
• Est. Priority Date: 07/03/1989
• Status: Expired due to Fees

• Current Assignee: Southwire Company
• Original Assignee: Southwire Company
• Inventors: Thrash, Frank R. Jr., Hughey, Raburn L. Jr., Hesterlee, Jerry M.
• Primary Examiner(s): Nimmo, Morris H.
• Application Number:
  US07/374,714
• Time in Patent Office: 785 Days
• Field of Search: 174/107, 174/106 R, 174/106 SC, 174/108, 156/51
• US Class Current: 174/107
• CPC Class Codes: H01B 7/2825 using a water impermeable sheath
• CPC Class Codes: H01B 9/02 with screens or conductive layers, e.g. for avoiding large potential gradients
• CPC Class Codes: Y02A 30/14 Extreme weather resilient electric power supply systems, e.g. strengthening power lines or underground power cables

Abstract

A water impervious cable construction for aerial, underground, or underwater use which includes at least one central electrical conductor, an overlayer of insulation material such as a plastic, a shield layer formed of a plurality of individual conductors (or the equivalent) which may be spirally wrapped and which shield layer is embedded in a layer of semiconducting material (which may also be a plastic), a layer of overlapped moisture barrier metal foil material, and a further overlayer of insulating material. The cable is manufactured on a substantially conventional cable extrusion line in which the partially manufactured cable (insulated core or cores wrapped with the shield conductors) is introduced into an extruder and a layer of semiconducting material is extruded thereon, wrapped with metal foil tape (which may include an edge located sealant), and introduced into a subsequent extruder to form one or more outer coatings. Use of expensive or special plastic laminated metal tape in combination with "hold" tape materials is eliminated, reducing the manufacturing cost to produce the cable.

Claims

1. A high voltage, high power water resistant cable, comprising:

a) a conductive cable core;

b) a plastic layer surrounding said cable core;

c) an electrically conductive shielding overlying said plastic layer;

d) a semiconducting layer encapsulating said shielding;

e) a moisture barrier enclosing said semiconducting layer, said moisture barrier comprising a foil having overlapping edges, said edges being unsealed to permit internal cable expansion; and

f) an outer covering of protective, insulating plastic over said moisture barrier.

2. The cable of claim 1, wherein said moisture barrier is a metal foil.

3. The cable of claim 1, wherein said shielding includes a plurality of longitudinal wires.

4. The cable of claim 1, wherein said shielding is encapsulated in said semiconducting layer such that moving contact between said shielding and said moisture barrier is substantially eliminated.

5. The cable of claim 2, wherein said metal foil moisture barrier is coated with a plastic material on at least one side.

6. The cable of claim 2, wherein said metal foil moisture barrier is aluminum.

7. The cable of claim 2, wherein said metal foil moisture barrier is copper.

8. The cable of claim 2, wherein said metal foil moisture barrier is lead.

9. The cable of claim 2, wherein said metal foil moisture barrier is steel.

10. The cable of claim 2, wherein said metal foil moisture barrier is an alloy including a metal selected from the group which includes aluminum, copper, lead, and steel.

11. The cable of claim 2, wherein said metal foil moisture barrier is between about 3 mils and about 10 mils thick.

12. The cable of claim 1, wherein said outer layer of insulation is corrugated.

13. The cable of claim 12, wherein said outer layer of insulation is longitudinally corrugated.

14. The cable of claim 12, wherein said outer layer of insulation is circumferentially corrugated.

15. The method of manufacturing a high voltage, high power water resistant cable, comprising:

a) providing at least one electrical cable core conductor;

b) extruding at least one layer of insulation around said at least one core conductor;

c) forming a metal shield layer overlying said extruded insulation layer;

d) extruding a semiconducting layer so as to encapsulate said shield layer;

e) forming an elongated metal foil moisture barrier around said semiconducting layer;

f) overlapping said moisture barrier along the edges thereof;

g) extruding an outer covering of protective, insulating plastic over said moisture barrier; and

,

h) permanently sealing the overlapping edges of the moisture barrier by the latent heat of one of said extrusion steps.

16. The method of claim 15, wherein the metal foil moisture barrier includes longitudinal edges, further including the step of forming the moisture barrier around the semiconducting layer such that the metal foil encircles the semiconductor layer in electrical contact therewith.

17. The method of claim 15, further including the step of corrugating the outer covering of protective, insulating plastic.

18. The method of claim 15, wherein the moisture barrier heat seal is accomplished with latent heat from the semiconductor layer extrusion step.

19. The method of claim 15, wherein said moisture barrier heat seal is formed with the aid of latent heat from a subsequent extrusion step.

20. A water resistant cable which includes an insulation layer;

an electrically conducting shielding overlying said insulation layer;

a semiconducting layer encapsulating said shielding;

an elongated moisture barrier comprising a metal foil face and a plastic layer face, said moisture barrier having overlapping edges; and

an outer layer of insulation extruded overall, wherein said moisture barrier encircles said semiconducting layer such that the metal foil face is in electrical contact therewith and the overlapping edges are not sealed to one another.