Key assembly

• US 5,777,281 A
• Filed: 09/23/1996
• Issued: 07/07/1998
• Est. Priority Date: 09/26/1995
• Status: Expired due to Fees

• Current Assignee: Psion Computers PLC
• Original Assignee: Psion Computers PLC
• Inventors: Riddiford, Martin Philip
• Primary Examiner(s): Gellner, Michael L.
• Assistant Examiner(s): Friedhofer, Michael A.
• Application Number:
  US08/723,881
• Time in Patent Office: 652 Days
• Field of Search: 200/5 R, 200/5 A, 200/511-517, 200/520, 200/341, 200/342, 200/344, 200/345, 400/490, 400/42, 400/491.1, 400/491.2, 400/495, 400/495.1, 235/145 R, 235/146
• US Class Current: 200/5.00A
• 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 13/80 characterised by the manner of cooperation of the contacts, e.g. with both contacts movable or with bounceless contacts
• CPC Class Codes: H01H 2201/008 Both contacts movable
• CPC Class Codes: H01H 2207/012 via underside of substrate
• CPC Class Codes: H01H 2221/026 Guiding or lubricating nylon
• CPC Class Codes: H01H 2223/0345 with keys positioned directly next to each other without an intermediate bezel or frame
• CPC Class Codes: H01H 2227/036 Minimise height
• CPC Class Codes: H01H 2233/016 with limited freedom

Abstract

A key assembly comprising a base; a manually operable key secured to, and mounted above the base by, a resilient key mat having an upstanding wall. The key is moveable against the resilience of the upstanding wall towards the base. A guide assembly extends between the base and the key to guide movement of the keys. A membrane is supported on the base and carries a pair of electrically insulated first contacts, each first contact of the pair being connected to a respective electrical track supported on the membrane and extending to a connection location. A second contact is provided on the underside of the key or the key mat and has a size and position such that movement of the key towards the base causes the second contact to engage both first contacts and thereby electrically connect the first contacts.

Claims

1. A key assembly comprising a base;

a manually operable key secured to, and mounted above said base by, a resilient key mat having an upstanding wall, the key having a depending neck and being moveable against the resilience of said upstanding wall towards said base;

a guide assembly extending between said base and said key to guide movement of said key;

a membrane supported on said base and carrying a pair of electrically insulated first contacts, each of said first contacts of the pair being connected to a respective electrical track supported on said membrane and extending to a connection location; and

a second contact provided on an underside of one of said depending neck and a portion of said key mat in contact with said depending neck and having a size and position such that movement of said key towards said base causes said second contact to engage both of said first contacts and thereby electrically connect said first contacts.

2. An assembly according to claim 1, wherein said first contacts are spaced about an arc, said second contact extending along said arc.

3. An assembly according to claim 2, wherein said second contact forms a closed curve.

4. An assembly according to claim 3, wherein said closed curve is a circle.

5. An assembly according to claim 2, wherein said first contacts are positioned about said guide assembly.

6. An assembly according to claim 1, wherein said tracks are provided on both sides of said membrane.

7. An assembly according to claim 1, wherein said resilient key mat has an upper, cylindrical section integrally formed with said upstanding wall and fitted to said depending neck, said depending neck being positioned on an underside of said key.

8. An assembly according to claim 1, wherein a part of said membrane carrying said first contacts overlies a recess in said base whereby movement of the key towards the base causes the membrane to be pushed against said resilient key mat into the recess.

9. An assembly according to claim 8, wherein said recess extends around said guide assembly.

10. An assembly according to claim 1, wherein said guide assembly comprises a cooperating finger and socket, one on said base and the other on said key.

11. An assembly according to claim 10, wherein said finger is mounted on an underside of said key and said socket is provided in said base.

12. An assembly according to claim 10, wherein said finger and socket each have a cruciform cross-section.

13. An assembly according to claim 10, wherein one of said finger and said socket has a laterally extending lug and the other a resilient tab such that, on insertion of said finger into said socket, said lug snaps over said tab to retain the key on said guide assembly.

14. An assembly according to claim 1, wherein said second contact is provided on an underside of said depending neck.

15. A key pad having a plurality of key assemblies, each key assembly comprising a base;

a manually operable key secured to, and mounted above said base by, a resilient key mat having an upstanding wall, the key having a depending neck and being moveable against the resilience of said upstanding wall towards said base;

a guide assembly extending between said base and said key to guide movement of said key;

a membrane supported on said base and carrying a pair of electrically insulated first contacts, each of said first contacts of the pair being connected to a respective electrical track supported on said membrane and extending to a connection location; and

a second contact provided on an underside of one of said depending neck and a portion of said key mat in contact with said depending neck and having a size and position such that movement of said key towards said base causes said second contact to engage both of said first contacts and thereby electrically connected said first contacts.

16. A key pad according to claim 15, wherein said first contacts of each of said keys are provided on a common membrane.

17. A key pad according to claim 15, wherein said resilient key mats of each key are formed from a common resilient key mat.

18. A key pad according to claim 15, wherein said second contact is provided on an underside of said depending neck.

19. Computing equipment including a processor and a key pad, the key pad having a plurality of key assemblies, each key assembly comprising a base;

a manually operable key secured to, and mounted above said base by, a resilient key mat having an upstanding wall, the key having a depending neck and being moveable against the resilience of said upstanding wall towards said base;

a guide assembly extending between said base and said key to guide movement of said key;

a membrane supported on said base and carrying a pair of electrically insulated first contacts, each of said first contacts of the pair being connected to a respective electrical track supported on said membrane and extending to a connection location; and

a second contact provided on an underside of one of said depending neck and a portion of said key mat in contact with said depending neck and having a size and position such that movement of said key towards said base causes said second contact to engage both of said first contacts and thereby electrically connect said first contacts, said key pad being coupled via the tracks to said processor.

20. Computing equipment according to claim 19, wherein said second contact is provided on an underside of said depending neck.