Membrane switch with rigid fascia

• US 20050061649A1
• Filed: 05/13/2004
• Published: 03/24/2005
• Est. Priority Date: 09/22/2003
• Status: Active Grant

• Current Assignee: Broadcom Corporation (Broadcom, Inc.), Illinois Tool Works Inc.
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Howie, Malcolm, Huang, Jiianming
• Granted Patent: US 6,967,299 B2
• Time in Patent Office: Days
• US Class Current: 200/512
• CPC Class Codes: H01H 13/702 with contacts carried by or formed from layers in a multilayer structure, e.g. membrane switches
• CPC Class Codes: H01H 2209/006 Force isolators
• CPC Class Codes: H01H 2209/018 flat, smooth or ripple-free
• CPC Class Codes: H01H 2209/07 metallic
• CPC Class Codes: H01H 2209/084 Glass
• CPC Class Codes: H01H 2239/038 Anti-vandalism

Abstract

A membrane switch provides a substantially rigid front fascia without the need for flexure limiting standoffs or the like. The membrane switch may use thin, printed insulating dots whose pattern controls the force required to actuate the switch elements as a function of distance from the switch elements preventing multiple activations.

Claims

1. An electrical switch assembly comprising:

a substantially rigid front panel;

a membrane switch positioned behind the front panel in contact with the front panel, the membrane switch providing a plurality of spatially separated switch elements; and

a backer plate positioned behind the membrane switch in contact with the membrane switch;

wherein a space between the front panel and the backer plate is substantially free of structure confining deflection of the front panel to an area of the switch elements.

2. The electrical switch assembly of claim 1 wherein the front panel is a panel of sheet metal.

3. The electrical switch assembly of claim 1 wherein the front panel is a rigid plastic.

4. The electrical switch assembly of claim 1 wherein the front panel is glass.

5. The electrical switch assembly of claim 1 wherein the front panel is non-planar.

6. The electrical switch assembly of claim 5 wherein the front panel is outwardly convex.

7. The electrical switch assembly of claim 1 wherein the membrane switch actuates with a deflection of less than 0.002 inches.

8. The electrical switch assembly of claim 1 further including a movable switch operator positioned in front of the rigid front panel to be pressed by a user and to apply increased pressure to the switch area from that pressing by a user.

9. The electrical switch assembly of claim 1 wherein the rigid front panel is transparent and further including a lamp behind the front panel.

10. The electrical switch assembly of claim 9 wherein the backer plate is a printed circuit card holding the lamp.

11. An electrical switch assembly comprising:

a substantially rigid front panel;

a front and back flexible sheet supporting at multiple spatially separated switch areas, electrically independent conductive switch contacts upon respective opposed surfaces of the front and back flexible sheet, portions of the front and back flexible sheets separated by insulator elements having a thickness of no greater than 0.002 inches;

whereby actuation forces may be transmitted through the substantially rigid front panel.

12. The electrical switch assembly of claim 11 wherein the front panel is selected from the group consisting of sheet metal, rigid polymer, and glass.

13. The electrical switch assembly of claim 11 wherein the switch areas are separated along a first axis, and the electrically independent conductive switch contacts are proportionally narrower along the first axis than along a perpendicular to the first axis.

14. The electrical switch assembly of claim 11 wherein the front and back flexible sheet are separated by a plurality of dielectric dots.

15. The electrical switch assembly of claim 14 wherein the dielectric dots are areas of printed insulating ink.

16. The electrical switch assembly of claim 14 wherein the dielectric dots are formed from portions of a separate insulating sheet.

17. The electrical switch assembly of claim 14 wherein the dielectric dots are embossments in at least one of the front and back flexible sheets.

18. The electrical switch assembly of claim 14 wherein the dielectric dots have a varying pattern density dependent on a distance from centers of the switch areas.

19. An electrical switch assembly comprising:

a substantially rigid front panel supporting on a rear surface at different switch locations conductive first switch contacts; and

a backer element positioned behind the front panel in contact adjacent to the front panel and supporting on its a front surface at the different switch locations second switch contacts connectable to the first switch contacts with deflection of the front panel;

wherein the first switch contacts are metal of the front panel.

20. (cancelled)

21. (cancelled)

22. An electrical switch assembly comprising:

at least two adjacent deformable sheets supporting at a switch area multiple electrically independent conductive switch contacts upon opposed surfaces of the deformable sheets to contact each other when the deformable sheets are pressed at the switch area wherein one deformable sheet is a substantially rigid front panel;

a plurality of dielectric dots separating the conductive switch contacts, the dielectric dots spaced apart provide a contacting of the conductive switch contacts at different thresholds of pressure when the deformable sheets are pressed at the switch area;

wherein a switch distinguishing between no pressure and at least two levels of compressive pressure is provided.

23. The electrical switch assembly of claim 22 wherein the dielectric dots near different contacts are of different thickness to provide the different thresholds of pressure.

24. The electrical switch assembly of claim 22 wherein the dielectric dots are of different separations from one another to provide the different thresholds of pressure.

25. The electrical switch assembly of claim 22 wherein the rigid front panel is positioned in front of two deformable sheets supporting the switch contacts and pressure must be applied to the deformable sheets through the rigid front panel.

26. (cancelled)