Pressure-compensated key switch

• US 5,514,843 A
• Filed: 03/23/1994
• Issued: 05/07/1996
• Est. Priority Date: 03/23/1994
• Status: Expired due to Fees

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Wilfong, James A., Gilman, Dave J.
• Primary Examiner(s): SCOTT, JAMES R
• Application Number:
  US08/216,716
• Time in Patent Office: 776 Days
• Field of Search: 200/5 R, 200/5 A, 200/512-517, 200/302.1-302.3, 200/5 E-5 EB, 200/553-563, 200/308-317, 200/17 R, 200/18, 200/339, 200/5 B
• US Class Current: 200/5.00R
• CPC Class Codes: H01H 2231/044 Under water
• CPC Class Codes: H01H 23/02 Details
• CPC Class Codes: H01H 23/025 Light-emitting indicators
• CPC Class Codes: H01H 25/041 having a generally flat operating member depressible at different locations to operate different controls

Abstract

A pressure-compensated key switch that actuates when a force is applied to an individual key but does not actuate when a uniform pressure is applied to all of the keys. The pressure-compensated key switch includes at least two keys arranged approximately symmetrically about, and balanced on, a pivot. A switch mechanism actuates when a force that offsets the balance and depresses one of the keys. The uniform pressure applied equally to all the keys will not depress or actuate any of the keys. When an individual key is depressed, a pad made of conductive material contacts and bridges a gap between two electrodes to complete an electrical path. The bridging of the gap is the actuation of the switch mechanism. The pressure-compensated key switch is typically part of a system that includes an electrical device to sense completion of the electrical path. A spring returns the key to its un-depressed position when no depressing force is applied. The keys are covered by a flexible membrane that makes a waterproof seal with a housing. An optional light source may illuminate the keys from below by shining through the keys and flexible membrane. Due to its balanced design the pressure-compensated key switch may be used underwater at depths as great as hundreds of feet without being actuated by the uniform water pressure and may be used at sea level without requiring an excessive force to depress the keys.

Claims

1. A key switch comprising:

a housing having an exterior, a hollow interior, and two key apertures spaced apart from each other;

a flexible membrane that covers the key apertures on the exterior of the housing;

a pivot/switch support mounted to the hollow interior of the housing;

a key body having an elongated body, a top, a bottom, and two opposite ends, the key body comprising;

a first and a second key surface on the key body top in each opposite end, where the key surfaces (i) extend through the key apertures in the housing to be adjacent to the flexible membrane and (ii) have approximately equal surface areas;

a first and a second switch driver on the key body bottom in each opposite end; and

a pivot line on the key body bottom, positioned approximately mid-way between the two key surfaces, the pivot line to have a line of contact with the pivot/switch support; and

a first and a second switch mechanism, each with a top and a bottom, the bottoms being supported by the pivot/switch support, the tops adjacent to first and second switch drivers, respectively, where the switch mechanism actuates when compressed between the switch driver and the pivot/switch support;

whereby, a light force applied through the flexible membrane upon one of the key surfaces will cause the key body to pivot about the line of contact between the pivot line and the pivot/switch support and cause one of the switch drivers to exert a compressing force on one of the switch mechanisms so that the switch mechanism actuates, and whereby a large pressure applied through the flexible membrane upon both of the key surfaces approximately equally will not actuate either of the switch mechanisms.

2. The key switch of claim 1, wherein said flexible membrane is marked with identification of at least one key surface.

3. The key switch of claim 1, further comprising at least one light source positioned below said key body, to shine through at least one of said key body and said flexible membrane.

4. The key switch of claim 3, wherein said light source is a light emitting diode (LED).

5. The key switch of claim 3, wherein said light source is an electroluminescent (EL) light.

6. The key switch of claim 1, wherein said flexible membrane is part of a waterproof seal to said housing.

7. The key switch of claim 1, wherein said pivot/switch support is a printed circuit board.

8. A key switch comprising:

a housing having an exterior, a hollow interior, a key aperture, and two pivot supports, one pivot support on each side of the key aperture;

a flexible membrane that covers the key aperture on the exterior of the housing;

a key body having an elongated body, a top, a bottom, two sides, and two opposite ends, the key body comprising;

a first and a second key surface on the key body top in each opposite end, where the key surfaces (i) extend through the key aperture in the housing to be adjacent to the flexible membrane and (ii) have approximately equal surface areas;

a first and a second switch driver on the key body bottom in each opposite end; and

two pivot pins, one on each side of the key body, positioned approximately mid-way between the two key surfaces, the pivot pins supported and free to rotate on the pivot supports in the housing;

a switch support mounted to the hollow interior of the housing; and

a first and a second switch mechanism, each with a top and a bottom, the bottoms being supported by the switch support, the tops adjacent to first and second switch drivers, respectively, where the switch mechanism actuates when compressed between the switch driver and the pivot/switch support;

whereby, a light force applied through the flexible membrane upon one of the key surfaces will cause the key body to rotate about the pivot pins supported by the pivot supports to cause one of the switch drivers to exert a compressing force on one of the switch mechanisms so that the switch mechanism actuates, and whereby a large pressure applied through the flexible membrane upon both of the key surfaces approximately equally will not actuate either of the switch mechanisms.

9. The key switch of claim 8, wherein said flexible membrane is marked with identification of at least one key surface.

10. The key switch of claim 8, further comprising at least one light source positioned below said key body, to shine through at least one of said key body and said flexible membrane.

11. The key switch of claim 10 wherein said light source is an light emitting diode (LED).

12. The key switch of claim 10 wherein said light source is an electroluminescent (EL) light.

13. The key switch of claim 8, wherein said flexible membrane is part of a waterproof seal to said housing.

14. The key switch of claim 8, wherein said switch support is a printed circuit board.

15. A key switch comprising:

a housing having an exterior, a hollow interior, and four key apertures spaced apart from each other;

a flexible membrane that covers the four key apertures on the exterior of the housing;

a pivot/switch support mounted to the hollow interior of the housing;

a key body having a cross shaped body with a first and a second pair of opposite ends, a top, and a bottom, the key body comprising;

a first and a second key surface on the key body top in the first opposite ends, where the key surfaces (i) extend through the key apertures in the housing to be adjacent to the flexible membrane and (ii) have approximately equal surface areas;

a third and a fourth key surface on the key body top in the second opposite ends, where the key surfaces (i) extend through the key apertures in the housing to be adjacent to the flexible membrane and (ii) have approximately equal surface areas;

a first, a second, a third, and a fourth switch driver on the key body bottom in each of each pair of opposite ends; and

a pivot point on the key body bottom, located approximately at the intersection of the line joining the centers of the first and second key surfaces with the line joining the centers of the third and fourth key surfaces, the pivot point to have a point of contact with the pivot/switch support; and

a first, a second, a third, and a fourth switch mechanism, each with a top and a bottom, the bottoms being supported by the pivot/switch support, the tops adjacent to first second, third, and fourth switch drivers, respectively, where the switch mechanism actuates when compressed between the switch driver and the pivot/switch support;

whereby, a light force applied through the flexible membrane upon one of the key surfaces will cause the key body to pivot about the point of contact between the pivot point and the pivot/switch support and cause one of the switch drivers to exert a compressing force on one of the switch mechanisms so that the switch mechanism actuates, and whereby a large pressure applied through the flexible membrane upon all four of the key surfaces approximately equally will not actuate any of the switch mechanisms.

16. The key switch of claim 15, wherein said flexible membrane is marked with identification of at least one key surface.

17. The key switch of claim 15, further comprising at least one light source positioned below said key body, to shine through at least one of said key body and said flexible membrane.

18. The key switch of claim 17, wherein said light source is a light emitting diode (LED).

19. The key switch of claim 17, wherein said light source is an electroluminescent (EL) light.

20. The key switch of claim 15, wherein said flexible membrane is part of a waterproof seal to said housing.

21. The key switch of claim 15, wherein said pivot/switch support is a printed circuit board.

22. A key switch having n keys, where n is two or more, comprising:

a housing having an exterior, a hollow interior, and n key apertures spaced apart from each other;

a flexible membrane that covers the n key apertures on the exterior of the housing;

a pivot/switch support mounted to the hollow interior of the housing;

a key body having a body, a top, a bottom, and n ends, the key body comprising;

n key surfaces on the key body top in each of the n ends, where the n key surfaces extend through the n key apertures in the housing to be adjacent to the flexible membrane;

n switch drivers on the key body bottom in each of the n ends; and

a pivot point on the key body bottom, at a selected position that is the area-weighted center of gravity of the n key surfaces, the pivot point to have a point of contact with the pivot/switch support; and

n switch mechanisms, each with a top and a bottom, the bottoms being supported by the pivot/switch support, the tops adjacent to the n switch drivers, respectively, where the switch mechanism actuates when compressed between the switch driver and the pivot/switch support;

whereby, a light force applied through the flexible membrane upon one of the key surfaces will cause the key body to pivot about the point of contact between the pivot point and the pivot/switch support and cause one of the switch drivers to exert a compressing force on one of the switch mechanisms so that the switch mechanism actuates, and whereby a large pressure applied through the flexible membrane upon all n of the key surfaces approximately equally will not actuate any of the switch mechanisms.

23. The key switch of claim 22, wherein said flexible membrane is marked with identification of at least one key surface.

24. The key switch of claim 22, further comprising at least one light source positioned below said key body, to shine through at least one of said key body and said flexible membrane.

25. The key switch of claim 24, wherein said light source is a light emitting diode (LED).

26. The key switch of claim 24, wherein said light source is an electroluminescent (EL) light.

27. The key switch of claim 22, wherein said flexible membrane is part of a waterproof seal to said housing.

28. The key switch of claim 22, wherein said pivot/switch support is a printed circuit board.