ELECTRIC RESISTANCE HEATING CABLE

• US 3,621,203 A
• Filed: 07/07/1970
• Issued: 11/16/1971
• Est. Priority Date: 06/26/1970
• Status: Expired due to Term

• Current Assignee: N/A
• Original Assignee: N/A
• Primary Examiner(s): Volodymyr Y. Mayewsky
• Application Number:
  US05/052,801
• Time in Patent Office: 497 Days
• Field of Search: 219/528,549,542,544 338/214,139-143 174/68-69
• US Class Current: 219/528
• CPC Class Codes: H05B 3/56 Heating cables

Abstract

A resistance heating cable having relatively high and low temperature sectors during operation. The cable has a flexible core, a resistance wire wound thereon and an outer covering. The resistance wire is wound with a number of layers in the low temperature sectors one across the other, which layers establish mutual electrical contact with each other. The high temperature sectors have at least two layers of windings.

Claims

1. An electric resistance heating cable comprising a flexible core of electrically insulating material, a heating wire helically wound on said core and extending the length of the cable, said cable being divided into groups of a first heating sector for producing relatively low temperatures during operation and a second heating sector for producing relatively high operating temperatures, said first sector having a plurality of layers of heating wire in electrical contact with each other wound about the core therethrough, said plurality of layers being an odd number of layers, alternate layers of said plurality being helically wound in the same direction as the heating wire wound about the core through said second sector, the layers intermediate said alternate layers being wound in the opposite direction, adjacent layers being located one across the other, said plurality of layers in the first sector exceeding the layers in the second sector by at least two layers, and a covering about said cable of electrically insulating material.

2. The electric resistance heating cable as claimed in claim 1, wherein said heating wire is of a material having a high positive temperature coefficient of the specific resistance.

3. The electric resistance heating cable as claimed in claim 1, wherein said odd number of layers of heating wire in said first heating sectors comprises three layers located one across the other and wherein the number of layers of heating wire in said second heating sectors is a single layer.

4. The electric resistance heating cable as claimed in claim 3, wherein the first two layers of heating wire in said first sector located on the core being wound at a greater pitch than is the third layer.

5. The electric resistance heating cable as claimed in claim 3, wherein said core is comprised of glass fibers and wherein said electrically insulating material of said cover is comprised of a glass-fiber pleat.

6. The electric resistance heating cable as claimed in claim 1, further comprising a central electric conductor within said core, said conductor being surrounded by an electrically insulating envelope and extending throughout the length of the cable.