Ravinder K Oswal

US Patent:

51810069, Jan 19, 1993

Filed:

Dec 11, 1991

Appl. No.:

7/805212

Inventors:

Jeff Shafe - Redwood City CA
O. James Straley - Redwood City CA
Gordon McCarty - San Jose CA
Ravinder K. Oswal - Union City CA
Amitkumar N. Dharia - Newark CA

Assignee:

Raychem Corporation - Menlo Park CA

International Classification:

H01C 710
H01C 713

US Classification:

338 22R

Abstract:

A polymer thick film ink which exhibits PTC behavior comprising an organic polymer which is crystalline, an active solvent suitable for dissolving the polymer, and carbon black which has a pH of less than 4. The ink is particularly useful in producing electrical devices such as heaters and circuit protection devices.

US Patent:

49805410, Dec 25, 1990

Filed:

Oct 3, 1989

Appl. No.:

7/416748

Inventors:

Jeff Shafe - Redwood City CA
O. James Straley - Redwood City CA
Gordon McCarty - San Jose CA
Ravinder K. Oswal - Union City CA
Bernadette A. Trammell - Menlo Park CA

Assignee:

Raychem Corporation - Menlo Park CA

International Classification:

H05B 312

US Classification:

219548

Abstract:

Electrical devices with improved resistance stability comprise a PTC element comprising a conductive polymer and two electrodes. The conductive polymer composition comprises an organic crystalline polymer and carbon black with a pH of less than 5. Particularly preferred conductive polymer compositions comprise carbon blacks which have a pH of less than 5. 0, a dry resistivity R. sub. CB and a particle size D in nanometers such that R. sub. CB /D is at most 0. 1. Electrical devices of the invention include heaters and circuit protection devices.

US Patent:

47615419, Aug 2, 1988

Filed:

May 19, 1987

Appl. No.:

7/051438

Inventors:

Neville S. Batliwalla - Foster City CA
Michael C. Jones - Fremont CA
Ravinder K. Oswal - Union City CA
Jeff Shafe - Redwood City CA
Bernadette A. Trammell - Menlo Park CA

Assignee:

Raychem Corporation - Menlo Park CA

International Classification:

H05B 302
H05B 336

US Classification:

219528

Abstract:

A number of improvements to electrical devices, particularly sheet heaters, comprising conductive polymer compositions, are provided. The preferred heater has the following features (a) it comprises a laminar resistive element and a plurality of electrodes which are so positioned that the predominant direction of current flow is parallel to the faces of the laminar element, (b) it comprises a laminar insulating element adjacent to but not secured to the electrodes and the resistive element; (c) it comprises a metallic foil, which acts as a ground plane and is positioned adjacent the insulating element but is not secured thereto; (d) it comprises a dielectric layer intimately bonded to the resistive element and to the electrodes. The invention also provides an electrical device comprising first and second members having different resistivities, and a thin contact layer of intermediate resistivity positioned between the first and second members.

US Patent:

47773510, Oct 11, 1988

Filed:

May 20, 1987

Appl. No.:

7/053610

Inventors:

Neville S. Batliwalla - Foster City CA
Michael C. Jones - Fremont CA
Ravinder K. Oswal - Union City CA
Jeff Shafe - Redwood City CA
Bernadette A. Trammell - Menlo Park CA

Assignee:

Raychem Corporation - Menlo Park CA

International Classification:

H05B 334
H05B 308

US Classification:

219528

Abstract:

A number of improvements to electrical devices, particularly sheet heaters, comprising conductive polymer compositions, are provided. The preferred heater has the following features (a) it comprises a laminar resistive element and a plurality of electrodes which are so positioned that the predominant direction of current flow is parallel to the faces of the laminar element, (b) it comprises a laminar insulating element adjacent to but not secured to the electrodes and the resistive element; (c) it comprises a metallic foil, which acts as a ground plane and is positioned adjacent the insulating element but is not secured thereto; (d) it comprises a dielectric layer intimately bonded to the resistive element and to the electrodes. The invention also provides an electrical device comprising first and second members having different resistivities, and a thin contact layer of intermediate resistivity positioned between the first and second members.

US Patent:

50930362, Mar 3, 1992

Filed:

Sep 20, 1988

Appl. No.:

7/247026

Inventors:

Jeff Shafe - Redwood City CA
O. James Straley - Redwood City CA
Ravinder K. Oswal - Union City CA
Gordon McCarty - San Jose CA
Amitkumar N. Dharia - Newark CA

Assignee:

Raychem Corporation - Menlo Park CA

International Classification:

H01B 106

US Classification:

252511

Abstract:

A polymer thick film ink which exhibits PTC behavior comprising an organic polymer which is crystalline, an active solvent suitable for dissolving the polymer, and carbon black which has a pH of less than 4. The ink is particularly useful in producing electrical devices such as heaters and circuit protection devices.

US Patent:

52502260, Oct 5, 1993

Filed:

Jun 3, 1988

Appl. No.:

7/202165

Inventors:

Ravinder K. Oswal - Union City CA
Amitkumar N. Dharia - Newark CA
Leonard Barrett - Union City CA

Assignee:

Raychem Corporation - Menlo Park CA

International Classification:

H01B 100

US Classification:

252500

Abstract:

Conductive polymer compositions which exhibit PTC behavior comprising a first polymeric component which may be crystalline, a second component, and a particulate conductive filler. The second component may comprise either a polymer which exhibits side chain crystallization or a crystalline material which has a sharp melting point and has poor physical properties at room temperature and/or exhibits no melt strength at elevated temperatures. The compositions are particularly useful in electrical devices which exhibit "square" resistance vs. temperature characteristics.

US Patent:

47193352, Jan 12, 1988

Filed:

May 19, 1987

Appl. No.:

7/051439

Inventors:

Neville S. Batliwalla - Foster City CA
Michael C. Jones - Fremont CA
Ravinder K. Oswal - Union City CA
Jeff Shafe - Redwood City CA
Bernadette A. Trammell - Menlo Park CA

Assignee:

Raychem Corporation - Menlo Park CA

International Classification:

H05B 334

US Classification:

219528

Abstract:

A number of improvements to electrical devices, particularly sheet heaters, comprising conductive polymer compositions, are provided. The preferred heater has the following features (a) it comprises a laminar resistive element and a plurality of electrodes which are so positioned that the predominant direction of current flow is parallel to the faces of the laminar element, (b) it comprises a laminar insulating element adjacent to but not secured to the electrodes and the resistive element; (c) it comprises a metallic foil, which acts as a ground plane and is positioned adjacent the insulating element but is not secured thereto; (d) it comprises a dielectric layer intimately bonded to the resistive element and to the electrodes. The invention also provides an electrical device comprising first and second members having different resistivities, and a thin contact layer of intermediate resistivity positioned between the first and second members.