Electrical apparatus for overcurrent protection of electrical circuits

• US 5,939,968 A
• Filed: 09/15/1998
• Issued: 08/17/1999
• Est. Priority Date: 06/19/1996
• Status: Expired due to Fees

• Current Assignee: Littelfuse Incorporated
• Original Assignee: Littelfuse Incorporated
• Inventors: Nguyen, Thinh, Minervini, Anthony
• Primary Examiner(s): Picard, Leo P.
• Assistant Examiner(s): Vortman, Anatoly
• Application Number:
  US09/153,688
• Time in Patent Office: 336 Days
• Field of Search: 337/12, 337/14, 337/137, 337/140, 337/158, 337/123, 337/139, 338/22 R, 361/58, 361/106
• US Class Current: 337/12
• CPC Class Codes: H01C 1/1406 Terminals or electrodes formed on resistive elements having positive temperature coefficient
• CPC Class Codes: H01C 7/027 consisting of conducting or semi-conducting material dispersed in a non-conductive organic material

Abstract

An electrical apparatus comprising first and second PTC elements composed of a polymer composition with conductive particles dispersed therein, an insulating body, and first and second conductive terminals. Flexible conductive members having a first end that can be electrically connected to a source of electrical power and a second end that is adapted to receive and make electrical contact with the apparatus are provided. The PTC element and the insulating body are positioned between the first and second conductive terminals so that when the apparatus is inserted between the flexible conductive members, the members exert a pressure on the insulating body.

Claims

1. An electrical circuit protection device making an electrical connection between flexible conductive members, the device comprising:

a first electrically insulating substrate having a first conductive terminal disposed thereon;

a second electrically insulating substrate having a second conductive terminal disposed thereon;

a PTC element positioned between the first and second substrates and electrically connecting the first conductive terminal to the second conductive terminal;

an insulating body positioned between the first and second substrates such that the flexible conductive members exert a force upon the insulating body, said force is greater then a force the flexible members exert upon the PTC element.

2. The circuit protection device of claim 1 wherein the PTC element comprises a polymer composition having conductive particles dispersed therein.

3. The circuit protection device of claim 2 wherein the composition comprises a polymer selected from the group consisting of polyethylene, polypropylene, copolymers of polyethylene and ethylene/propylene copolymers.

4. The circuit protection device of claim 2 wherein the conductive particles comprise carbon black.

5. The circuit protection device of claim 2 wherein the PTC element further comprises first and second electrodes.

6. The circuit protection device of claim 1 wherein the conductive terminals are comprised of a metal.

7. The circuit protection device of claim 1 wherein either a portion of the first conductive terminal or a portion of the second conductive terminal defines a fusible element electrically connected in series with the PTC element.

8. The circuit protection device of claim 1 wherein the insulating substrates have a first and a second surface, the first and second conductive terminals being disposed on the first and second surfaces of the insulating substrates, respectively.

9. The circuit protection device of claim 8 wherein the conductive terminal disposed on the first surface of the substrate is electrically connected to the conductive terminal disposed on the second surface of the substrate by way of a through-hole.

10. An electrical circuit protection device making an electrical connection between flexible conductive members, the device comprising:

a first electrically insulating substrate having a plurality of first conductive terminals disposed thereon;

a second electrically insulating substrate having a corresponding plurality of second conductive terminals disposed thereon;

a plurality of PTC elements positioned between the first and second substrates, each PTC element electrically connected to a first and second conductive terminal, respectively;

a plurality of insulating bodies disposed between the first and second substrates and positioned such that the flexible conductive members exert a force upon at least one of the plurality of insulating bodies, said force is greater then a force the flexible members exert upon at least one of the plurality of PTC elements.

11. The electrical device of claim 10 wherein a portion of either the first or the second conductive terminal defines a fusible element, the fusible element being electrically connected in series with one of the plurality of PTC elements.

12. The electrical device of claim 10 wherein at least two of the plurality of PTC elements are electrically connected in parallel.

13. The electrical device of claim 12 wherein the first of the at least two of the plurality of PTC elements has a resistance R₁ at approximately 25°

C. and the second of the at least two of the plurality of PTC elements has a resistance R₂ at approximately 25°

C., R₁ being approximately equal to R₂.

14. The electrical device of claim 12 wherein the first of the at least two of the plurality of PTC elements has a resistance R₁ at approximately 25°

C. and the second of the at least two of the plurality of PTC elements has a resistance R₂ at approximately 25°

C., R₁ being greater than R₂.

15. An electrical circuit protection device for making an electrical connection between flexible conductive members, the device comprising:

a first electrically insulating substrate having a plurality of first conductive terminals disposed thereon, a portion of each first conductive terminal defining a fusible element;

a second electrically insulating substrate having a plurality of second conductive terminals disposed thereon;

a plurality of PTC elements disposed between the insulating substrates, each PTC element being composed of a conductive polymer composition and being electrically connected to one of the plurality of first conductive terminals and to one of the plurality of second conductive terminals such that each PTC element is electrically connected in series with the portion of each first conductive terminal defining a fusible element, respectively; and

a plurality of insulating bodies disposed between the first and second substrates and positioned such that when the device is electrically connected between the flexible conductive members, the flexible members exert a force upon at least one of the plurality of insulating bodies.