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Electrical resistance heating element with signal means to indicate first use

  • US 4,647,756 A
  • Filed: 07/05/1983
  • Issued: 03/03/1987
  • Est. Priority Date: 07/05/1983
  • Status: Expired due to Term
First Claim
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1. In an electric resistance heating element for welding thermoplastic tubes together, said heating element including an electrical resistor for producing heat when connected in circuit with a power supply, the improvement comprising, in combination with said heating element'"'"'s resistor, a fusible signal means incorporated within said heating element, said fusible signal means being connected in parallel electrical circuit with the resistor of said heating element, said fusible signal means being capable when intact of providing a signal indicative of previous nonuse of said heating element and being automatically self-destructable upon energization of said heating element resistor during the first use of said heating element so as to be incapable of providing the signal indicative of previous nonuse upon a subsequent energization of said heating element resistor.

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