Electrical safety device

• US RE38,714 E1
• Filed: 07/30/1998
• Issued: 03/22/2005
• Est. Priority Date: 03/07/1994
• Status: Expired due to Fees

• Current Assignee: Electro-TK, Inc.
• Original Assignee: Electro-TK, Inc.
• Inventors: Watkins, Kenneth S. Jr., Pope, Ralph E. Jr.
• Primary Examiner(s): Leja, Ronald W.
• Application Number:
  US09/126,508
• Time in Patent Office: 2,427 Days
• Field of Search: 361/103, 361/106, 219/110, 219/241, 219/485, 219/488, 219489-491, 219/494, 219/497, 219/501, 219/510, 315/150, 315/158, 315/159
• US Class Current: 361/103
• CPC Class Codes: H01B 7/324 comprising temperature sensing means
• 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: H02H 5/10 responsive to mechanical injury, e.g. rupture of line, breakage of earth connection
• CPC Class Codes: H02H 7/228 for covered wires or cables
• CPC Class Codes: H05B 1/02 Automatic switching arrangements specially adapted to apparatus ; Control of heating devices thermally-actuated switches H01H37/00
• CPC Class Codes: H05B 1/0208 actuated by the expansion or evaporation of a gas or liquid
• CPC Class Codes: H05B 3/56 Heating cables

Abstract

An electrical safety device is disclosed which utilizes a sensor conductor configured in a continuous loop and disposed in an electrical component so as to sense overtemperature or mechanical damage over a length or wide area of the component. The sensor may be simple insulated or non insulated copper wire. A low voltage potential is maintained across the sensor conductor. The sensor circuitry includes ambient temperature compensation.

Claims

1. An electrical cord safety device, the device comprising:

an electrical power cord comprising at least one current carrying conductor, insulation surrounding the current carrying conductor, and a cord outside surface;

a sensor conductor for sensing temperature in the said electrical power cord, the said sensor conductor disposed in the insulation of the said electrical power cord as a continuous loop, the said sensor conductor having a positive temperature coefficient of resistivity, and further disposed between the said current carrying conductor and the said outside surface and in a manner such that continuity of the said sensor conductor is lost upon mechanical damage to the electrical power cord before the current carrying conductor is exposed, whereby the said sensor conductor further comprises a continuity detecting means;

a reference conductor disposed in the vicinity of the said electrical power cord for sensing ambient temperature; and

a control circuit connected to the said sensor conductor and the said reference conductor, the said control circuit comparing a first electrical quantity representative of the said sensor conductor temperature and a second electrical quantity representative of the said reference sensor temperature and interrupting current to the said current carrying conductor upon a predetermined difference between the said first electrical quantity and the said second electrical quantity.

2. The device of claim 1 wherein the said sensor conductor is disposed in a parallel relationship with the said current carrying conductor.

3. The device of claim 1 wherein the said sensor conductor is disposed in a sinusoidal shape along the said current carrying carrying conductor.

4. The device of claim 1 wherein the said sensor conductor is disposed in a helical shape surrounding the said current carrying conductor.

5. The device of claim 1 wherein the said sensor conductor comprises a conductive polymer strip.

6. An electrical safety device, the device comprising:

a case for an electrical component, the said case comprising an outside surface;

a current carrying conductor disposed inside the said case;

a sensor conductor for sensing temperature in the said case, the said sensor conductor disposed in the said case as a continuous loop, the said sensor conductor having a positive temperature coefficient and further disposed between the said current carrying conductor and the said outside surface of the said case and in a manner such that continuity of the said sensor conductor is lost upon mechanical damage to the said case before the said current carrying conductor is exposed, whereby the said sensor conductor further comprises a continuity sensing means;

a reference conductor disposed in the vicinity of the said case for sensing ambient temperature; and

a control circuit connected to the said sensor conductor and the said reference conductor, the said control circuit comparing a first electrical quantity representative of the said sensor conductor temperature and a second electrical quantity representative of the said reference sensor temperature and interrupting current to the said current carrying conductor upon a predetermined difference between the said first electrical quantity and the said second electrical quantity whereby the said device acts to detect a high temperature in the said case as compared to the said ambient temperature.

7. The device of claim 6 wherein the said case comprises an inside surface and the said sensor conductor is a conductive foil disposed in the said inside surface of the said case.

8. An electrical power cord including an insulated electrical conductor portion for use in connection with a control circuit configured for measuring resistance, said control circuit configured for initiating a control action upon its detection of a predetermined resistance, said electrical power cord being substantially elongate, having a length, and comprising:

an electrical power cord portion itself including along its length a substantially elongate current carrying conductor portion configured to pass electrical current, said current carrying conductor portion extending substantially straight along said length of said insulated electrical conductor portion such that said current carrying conductor portion is approximately as long as said insulated electrical conductor portion;

insulation at least partially surrounding said current carrying conductor portion, said insulation defining an insulated electrical conductor outside surface portion; and

a substantially elongate sensor conductor portion for sensing temperature within said insulation, said elongate sensor conductor portion extending along said length of said insulated electrical conductor portion but curving at least partially laterally relative to said conductor portion length such that said elongate sensor conductor portion is longer than said insulated electrical conductor portion, said sensor conductor portion comprising a material having a change in resistance with temperature whereby a change in the temperature of said sensor conductor portion results in a change in resistance of said sensor conductor portion, and said sensor conductor portion further disposed between said current carrying conductor portion and said insulated electrical conductor outside surface portion in a manner such that continuity of said sensor conductor portion tends to be lost upon mechanical damage of said insulation before said current carrying conductor portion is exposed,

such that said sensor conductor portion provides a dual function of indicating mechanical damage as well as the function of indicating heating of said insulation to allow said control circuit to initiate said control action upon a predetermined resistance of said sensor conductor portion.

9. The electrical power cord as claimed in claim 8, wherein said sensor conductor portion has a positive temperature coefficient of resistivity.

10. The electrical power cord as claimed in claim 8, wherein said sensor conductor portion is disposed in a helical relationship about the current carrying conductor portion, said helical relationship causing said sensor conductor portion to be longer than said current carrying conductor portion for a given length of insulated electrical conductor portion.

11. The electrical power cord as claimed in claim 8, wherein said sensor conductor portion is disposed in a sinusoidal relationship about the current carrying conductor portion, said sinusoidal relationship causing said sensor conductor portion to be longer than said current carrying conductor portion for a given length of insulated electrical conductor portion.

12. The electrical power cord as claimed in claim 8, wherein said sensor conductor portion is one of a plurality of coparallel strips disposed radially about the current carrying conductor portion.

13. An electrical power cord including an insulated electrical conductor portion for use in connection with a control circuit configured for measuring resistance, said control circuit configured for initiating a control action upon its detection of a predetermined resistance, said electrical power cord being substantially elongate, having a length, and comprising:

an electrical power cord portion itself including along its length a substantially elongate current carrying conductor portion configured to pass electrical current, said current carrying conductor portion extending substantially straight along said length of said insulated electrical conductor portion such that said current carrying conductor portion is approximately as long as said insulated electrical conductor portion;

insulation at least partially surrounding said current carrying conductor portion, said insulation defining an insulated electrical conductor outside surface portion; and

a substantially elongate sensor conductor portion for sensing temperature within said insulation, said elongate sensor conductor portion extending along said length of said insulated electrical conductor portion but curving at least partially laterally relative to said conductor portion length such that said elongate sensor conductor portion is longer than said insulated electrical conductor portion, said sensor conductor portion comprising a material having a change in resistance with temperature whereby a change in the temperature of said sensor conductor portion results in a change in resistance of said sensor conductor portion, and said sensor conductor portion being noninsulated, and said sensor conductor portion being further disposed between said current carrying conductor portion and said insulated electrical conductor outside surface portion in a manner such that continuity of said sensor conductor portion tends to be lost upon mechanical damage of said insulation before said current carrying conductor portion is exposed,

such that said sensor conductor portion provides a dual function of indicating mechanical damage as well as the function of indicating heating of said insulation to allow said control circuit to initiate said control action upon a predetermined resistance of said sensor conductor portion.

14. The electrical power cord as claimed in claim 13, wherein said sensor conductor portion has a positive temperature coefficient of resistivity.

15. The electrical power cord as claimed in claim 13, wherein said sensor conductor portion is disposed in a helical relationship about the current carrying conductor portion, said helical relationship causing said sensor conductor portion to be longer than said current carrying conductor portion for a given length of insulated electrical conductor portion.

16. The electrical power cord as claimed in claim 13 wherein said sensor conductor portion is disposed in a sinusoidal relationship about the current carrying conductor portion, said sinusoidal relationship causing said sensor conductor portion to be longer than said current carrying conductor portion for a given length of insulated electrical conductor portion.

17. The electrical power cord as claimed in claim 13, wherein said sensor conductor portion is one of a plurality of coparallel strips disposed radially about the current carrying conductor portion.

18. An electrical power cord including an insulated electrical conductor portion for use in connection with a control circuit configured for measuring resistance, said control circuit configured for initiating a control action upon its detection of a predetermined resistance, said electrical power cord being substantially elongate and comprising:

an electrical power cord portion itself including along its length a substantially elongate current carrying conductor portion configured to pass electrical current;

insulation at least partially surrounding said current carrying conductor portion, said insulation defining an insulated electrical conductor outside surface portion; and

a plurality of substantially elongate, noncontacting sensor conductor portions for sensing temperature within said insulation, said sensor conductor portions not contacting each other, at least one of said sensor conductor portions comprising a material having a change in resistance with temperature whereby a change in the temperature of said sensor conductor portion results in a change in resistance of said sensor conductor portion, and said same one of said sensor conductor portions further disposed between said current carrying conductor portion and said insulated electrical conductor outside surface portion in a manner such that continuity of said same one of said sensor conductor portions tends to be lost upon mechanical damage of said insulation before said current carrying conductor portion is exposed,

such that said same one of said noncontacting sensor conductor portions provides a dual function of indicating mechanical damage as well as the function of indicating heating of said insulation to allow said control circuit to initiate said control action upon a predetermined resistance of said same one of said sensor conductor portions.

19. The electrical power cord as claimed in claim 18, wherein said same one of said sensor conductor portions is substantially straight and parallel to said current carrying conductor portion.

20. The electrical power cord as claimed in claim 18, wherein said same one of said sensor conductor portions is disposed in a helical relationship about the current carrying conductor portion.

21. The electrical power cord as claimed in claim 18, wherein said same one of said sensor conductor portions is disposed in a sinusoidal relationship about the current carrying conductor portion.

22. The electrical power cord as claimed in claim 18, wherein said same one of said sensor conductor portions is one of a plurality of coparallel strips disposed radially about the current carrying conductor portion.

23. An electrical power cord including an insulated electrical conductor portion for use in connection with a control circuit configured for measuring resistance, said control circuit configured for initiating a control action upon its detection of a predetermined resistance, said electrical power cord being substantially elongate and comprising:

an electrical power cord portion itself including along its length a substantially elongate current carrying conductor portion configured to pass electrical current;

insulation at least partially surrounding said current carrying conductor portion, said insulation defining an insulated electrical conductor outside surface portion; and

a plurality of substantially elongate and parallel sensor conductor portions for sensing temperature within said insulation, at least one of said sensor conductor portions comprising a material having a positive temperature coefficient of resistivity, and said same one of said sensor conductor portions further disposed between said current carrying conductor portion and said insulated electrical conductor outside surface portion in a manner such that continuity of said same sensor conductor portion tends to be lost upon mechanical damage of said insulation before said current carrying conductor portion is exposed,

such that said same one of said sensor conductor portions provides a dual function of indicating mechanical damage as well as the function of indicating heating of said insulation to allow said control circuit to initiate said control action upon a predetermined resistance of said sensor conductor portion.

24. The electrical power cord as claimed in claim 23, wherein said plurality of substantially elongate and parallel sensor conductor portions comprises two or more sensor conductor portions.

25. The electrical power cord as claimed in claim 23, wherein said plurality of substantially elongate and parallel sensor conductor portions comprises three or more sensor conductor portions.

26. An electrical power cord including an insulated electrical conductor portion for use in connection with a control circuit configured for measuring resistance, said control circuit configured for initiating a control action upon its detection of a predetermined resistance, said electrical power cord being substantially elongate and comprising:

an electrical power cord portion itself including along its length a substantially elongate current carrying conductor portion configured to pass electrical current, said current carrying conductor portion extending along said length of said insulated electrical conductor portion such that said current carrying conductor portion is approximately as long as said insulated electrical conductor portion;

insulation at least partially surrounding said current carrying conductor portion, said insulation defining an insulated electrical conductor outside surface portion; and

a substantially elongate sensor conductor portion for sensing temperature within said insulation, said elongate sensor conductor portion extending along said length of said insulated electrical conductor portion but curving at least partially laterally relative to said conductor portion length and disposed in a helical relationship about the current carrying conductor portion such that said elongate sensor conductor portion is longer than said insulated electrical conductor portion, said sensor conductor portion comprising a material having a change in resistance with temperature whereby a change in the temperature of said sensor conductor portion results in a change in resistance of said sensor conductor portion, and said sensor conductor portion further disposed between said current carrying conductor portion and said insulated electrical conductor outside surface portion in a manner such that continuity of said sensor conductor portion tends to be lost upon mechanical damage of said insulation before said current carrying conductor portion is exposed,

such that said sensor conductor portion provides a dual function of indicating mechanical damage as well as the function of indicating heating of said insulation to allow said control circuit to initiate said control action upon a predetermined resistance of said sensor conductor portion.

27. The electrical power cord for use in connection with a control circuit configured for measuring resistance as claimed in claim 26, wherein said current carrying conductor portion extends substantially straight along said length of said insulated electrical conductor portion.

28. An electrical power cord including an insulated electrical conductor portion for use in connection with a control circuit configured for measuring resistance, said control circuit configured for initiating a control action upon its detection of a predetermined resistance, said electrical power cord being substantially elongate, having a length, having a transverse cross section having a substantially constant outer periphery, and comprising:

an electrical power cord portion itself including along its length a substantially elongate current carrying conductor portion configured to pass electrical current, said current carrying conductor portion extending along said length of said insulated electrical conductor portion and located substantially consistently within said transverse cross section of said electrical conductor portion along the length of said electrical conductor portion;

insulation at least partially surrounding said current carrying conductor portion, said insulation defining an insulated electrical conductor outside surface portion; and

a substantially elongate sensor conductor portion for sensing temperature within said insulation, said elongate sensor conductor portion extending along said length of said insulated electrical conductor portion and located at different locations within said transverse cross section of said electrical conductor portion along the length of said electrical conductor portion such that said elongate sensor conductor portion is longer than said insulated electrical conductor portion, said sensor conductor portion comprising a material having a change in resistance with temperature whereby a change in the temperature of said sensor conductor portion results in a change in resistance of said sensor conductor portion, and said sensor conductor portion further disposed between said current carrying conductor portion and said insulated electrical conductor outside surface portion in a manner such that continuity of said sensor conductor portion tends to be lost upon mechanical damage of said insulation before said current carrying conductor portion is exposed,

such that said sensor conductor portion provides a dual function of indicating mechanical damage as well as the function of indicating heating o said insulation to allow said control circuit to initiate said control action upon a predetermined resistance of said sensor conductor portion.

29. The electrical power cord for use in connection with a control circuit configured for measuring resistance as claimed in claim 28, wherein said elongate sensor conductor portion is disposed in a helical relationship about the current carrying conductor portion.