HEAT RESPONSIVE CABLE ASSEMBLY

• US 3,774,184 A
• Filed: 11/24/1971
• Issued: 11/20/1973
• Est. Priority Date: 11/24/1971
• Status: Expired due to Term

• Current Assignee: David F. Scarelli
• Original Assignee: David F. Scarelli
• Inventors: Scarelli, David F.
• Primary Examiner(s): Caldwell, John W.
• Assistant Examiner(s): Partridge, Scott F.
• Application Number:
  US05/201,760
• Time in Patent Office: 727 Days
• Field of Search: 340/227C,227.1,227,228 338/26
• US Class Current: 340/590
• CPC Class Codes: G08B 17/06 Electric actuation of the alarm, e.g. using a thermally-operated switch
• CPC Class Codes: H01B 13/008 for manufacturing extensible conductors or cables
• CPC Class Codes: H01B 7/102 responsive to heat

Abstract

A heat responsive cable assembly for use with a fire alarm system, or the like, said assembly comprising a pair of helically twisted conductors of substantially the same thermal expansion rates, the wires being plastically deformed during twisting, with a medium of heat sensitive insulation therebetween which is removed in response to predetermined high temperature conditions to permit contact between the conductors due to random thermal expansions and changes in helix angles of adjacent sections of the conductors.

Claims

1. In combination with a fire alarm system having a voltage source, a heat responsive cable assembly comprising a single pair only of solid electrical conductors of relatively soft, deformable material helically twisted about each other, said conductors being connected to said fire alarm system voltage source, and a medium of heat sensitive electrical insulation normally between said conductors, said heat sensitive insulation being removed from between said conductors in response to a predetermined high temperature condition to expose said conductors for engagement with each other, said conductors normally being spaced from each other by a distance of approximately 0.003 inch and being helically twisted at least 35 turns per foot of axial length, said conductors having relatively high rates of thermal expansion such that they are significantly expanded when exposed to said predetermined high temperature condition to provide different helix angles between adjacent sections of said conductors and effect contact therebetween, both of said conductors having substantially the same rate of thermal expansion and said insulation gasing off at said predetermined high temperature condition to provide clean contact areas on each conductor.

2. The structure set forth in claim 1, wherein said conductors are each between 20 to 50 AWG.

3. The assembly set forth in claim 1, wherein said insulation is polyurethane.

4. The structure set forth in claim 1 wherein said voltage source is less than 25 volts.

5. The structure set forth in claim 4 wherein said voltage source is approximately 10 volts alternating current.