Electrical safety circuit with a breakable conductive element

• US 5,801,914 A
• Filed: 05/23/1996
• Issued: 09/01/1998
• Est. Priority Date: 05/23/1996
• Status: Expired due to Fees

• Current Assignee: Sunbeam Products, Inc. d/b/a Jarden Consumer Solutions (Newell Brands Inc.)
• Original Assignee: Sunbeam Products, Inc. d/b/a Jarden Consumer Solutions (Newell Brands Inc.)
• Inventors: Thrash, Joseph L.
• Primary Examiner(s): Fleming, Fritz
• Assistant Examiner(s): Sherry, Michael J.
• Application Number:
  US08/652,898
• Time in Patent Office: 831 Days
• Field of Search: 361/104, 361/103, 361/106, 361/93, 337/300, 337/401, 219/212, 219/544, 219/545, 219/549
• US Class Current: 361/104
• CPC Class Codes: H02H 5/043 the temperature dependent resistor being disposed parallel to a heating wire, e.g. in a heating blanket
• CPC Class Codes: H05B 1/0227 Applications
• CPC Class Codes: H05B 2203/003 using serpentine layout
• CPC Class Codes: H05B 2203/014 Heaters using resistive wires or cables not provided for in H05B3/54
• CPC Class Codes: H05B 2203/017 Manufacturing methods or apparatus for heaters
• CPC Class Codes: H05B 2203/035 Electrical circuits used in resistive heating apparatus
• CPC Class Codes: H05B 3/342 heaters used in textiles
• CPC Class Codes: H05B 3/56 Heating cables

Abstract

An electrical safety circuit for discontinuing the operating power to an electrical device when overheat conditions are present. The safety circuit includes a conductive element in thermal proximity to at least one of the circuit elements of the electrical device that is energized by the operating power. The conductive element is structured so as to quickly break in response to high temperatures. A switching circuit is included which responds to a break in the conductive element by discontinuing the operating power to the electrical device.

Claims

1. An electrical safety circuit for an electrical device having circuit elements that are energized by an operating power, the safety circuit comprising:

a conductive element in thermal proximity to at least one of the circuit elements that are energized by the operating power, said conductive element structured for breaking in response to high temperatures; and

a switching circuit coupled to said conductive element and the operating power, said switching circuit responding to a break in said conductive element by discontinuing the operating power to the electrical device.

2. The safety circuit as defined in claim 1 wherein said conductive element comprises stainless steel fibers twisted around a polyester yarn.

3. The safety circuit as defined in claim 1 wherein said conductive element comprises stainless steel fiber.

4. The safety circuit as defined in claim 1 wherein said switching circuit comprises a relay.

5. The safety circuit as defined in claim 1 further comprising a fuse that is coupled to the operating power, said fuse discontinuing the operating power to the electrical device when a predetermined current level is exceeded.

6. The safety circuit as defined in claim 1 wherein the electrical device is an electric blanket.

7. The safety circuit as defined in claim 1 wherein the at least one circuit element is a positive temperature coefficient heating element having two spaced conductors, and wherein said conductive element is contained within the heating element and runs parallel to the conductors.

8. The safety circuit as defined in claim 7 wherein each of the two spaced conductors has two ends which are connected together.

9. The safety circuit as defined in claim 1 wherein said conductive element breaks before a fire is ignited in the electrical device.

10. The safety circuit as defined in claim 1 wherein said conductive element breaks if an open circuit or short circuit condition occurs in the electrical device.

11. An electrical safety circuit for an electrical device having circuit elements that are energized by an operating power, the safety circuit comprising:

a means for conducting current, said conducting means in thermal proximity to at least one of the circuit elements that are energized by the operating power, said conducting means structured for materially breaking in response to high temperatures of the at least one circuit element; and

a means for responding to a break in said conducting means by discontinuing the operating power to the at least one circuit element.

12. A method for protecting an electrical device that is energized by an operating power and in which an overheating condition may occur, the method comprising the steps of:

positioning a conductive element in thermal proximity to the potential site of an overheating condition;

severing said conductive element in response to an overheating condition; and

implementing a responsive circuit to discontinue the operating power to the site of the overheating condition in response to the severing of said conductive element.

13. An electrical safety circuit for an electrical device having circuit elements that are energized by an operating power, the safety circuit comprising:

a conductive element in proximity to at least one of the circuit elements, said conductive element structured for breaking in response to heat from the at least one circuit element exceeding a predetermined level;

a switching circuit responsive to a break in said conductive element for discontinuing the operating power; and

wherein the at least one circuit element is a heating element having at least one conductor, and wherein said conductive element is contained within the heating element and runs substantially parallel to the at least one conductor.

14. The safety circuit as defined in claim 13 wherein the heating element is a positive temperature coefficient heating element having two spaced conductors, and wherein each of the two spaced conductors has two ends which are connected together.

15. In an electrical device having a circuit element that is energized by an operating power, the combination comprising:

a conductive element substantially coextensive with and in proximity to the circuit element, said conductive element adapted for breaking in response to heat from the circuit element exceeding a predetermined level; and

a responsive circuit coupled to said conductive element and the operating power, said responsive circuit responding to a break in said conductive element by discontinuing the operating power to the circuit element.

16. In an electrical device having an element that is energized by an operating power, the combination comprising:

a conductor in proximity to the element, said conductor configured for breaking in a non-revertible manner in response to heat from the element exceeding a predetermined level; and

a responsive circuit coupled to said conductor and the operating power, said responsive circuit responding to a break in said conductor by discontinuing the operating power to the element.