KEYBOARD FOR ELECTRONIC CIRCUIT

• US 3,797,630 A
• Filed: 07/12/1971
• Issued: 03/19/1974
• Est. Priority Date: 07/12/1971
• Status: Expired due to Term

• Current Assignee: Sammy Zilkha
• Original Assignee: Sammy Zilkha
• Inventors: Zilkha, Sammy
• Primary Examiner(s): Bagwill, Robert E.
• Assistant Examiner(s): Rader, R. T.
• Application Number:
  US05/161,611
• Time in Patent Office: 981 Days
• Field of Search: 197/17,98 340/365,173 179/9K 235/145,146 178/79,81 307/88ET 200/52,DIG.1,159,166
• US Class Current: 400/479.1
• CPC Class Codes: B41J 5/08 Character or syllable selected by means of keys or keyboards of the typewriter type
• CPC Class Codes: H01H 13/02 Details
• CPC Class Codes: H01H 13/705 characterised by construction, mounting or arrangement of operating parts, e.g. push-buttons or keys
• CPC Class Codes: H01H 2203/056 Cuts or depressions in support, e.g. to isolate contacts
• CPC Class Codes: H01H 2205/022 Conductive rubber
• CPC Class Codes: H01H 2215/036 Metallic disc
• CPC Class Codes: H01H 2217/02 After travel
• CPC Class Codes: H01H 2221/002 integral with membrane
• CPC Class Codes: H01H 2221/04 magnetic
• CPC Class Codes: H01H 2221/062 Damping vibrations
• CPC Class Codes: H01H 2221/066 replaceable
• CPC Class Codes: H01H 2223/002 sealed
• CPC Class Codes: H01H 2223/008 metallic
• CPC Class Codes: H01H 2233/034 Snap coupling
• CPC Class Codes: H01H 2239/006 Containing a capacitive switch or usable as such
• CPC Class Codes: H01H 2239/008 Static electricity considerations

Abstract

An electronic keyboard assembly is formed essentially of three parts, an integrated circuit using high input impedance metal oxide semi-conductors, a printed circuit board electrically connected to the integrated circuit and a number of key assemblies located above the printed circuit board. In a preferred construction, the key assemblies are not electrically connected to the printed circuit board, each key having a conductive element forming, when the key is depressed, a capacitive bridge coupling two conductors on the printed circuit board.

Claims

1. A keyboard comprising a base plate, a plurality of keys and, for each key, an Associated cylindrical key support on the base plate, and, each of said keys comprising a key carrier formed by a sleeve around and slidable on the key support, a key member mounted on the key carrier, a plunger within said key support and having a stem extending through said base plate, a resilient conductive element on said plunger, a resilient pad within said key member and engaging said key member and said stem to permit relative axial movement therebetween, and a helical bias spring within the key support biasing the key carrier away from the base plate, said keyboard further comprising a printed circuit board below said base plate but supported thereby, said printed circuit board having at least two conductors below each key, said conductive element on each key being arranged to provide capacitive coupling between the two conductors below that key when the key is depressed.

2. A keyboard as claimed in claim 1 wherein said base plate comprises a metal plate with downwardly extending flanges, the flanges on two opposite sides being partially inturned to form a support for said printed circuit board.

3. A keyboard as claimed in claim 1 and having, on said printed circuit board, a grounded conductor between each pair of conductors to be capacitively coupled by depression of a key.

4. A keyboard as claimed in claim 1 wherein said stem has a pair of projections extending radially outwardly, one on each side of the stem and wherein said key carrier has inwardly extending portions engaging said projections to form a bayonet joint.

5. A keyboard as claimed in claim 1 wherein said conductive element on said stem comprises a block of conductive elastomeric material.

6. A keyboard as claimed in claim 5 wherein said block of elastomeric material is shaped to have portions overlying said two conductors with a channel on the underside of the block between said portions.

7. A keyboard as claimed in claim 6 wherein said block of elastomeric material has an aperture and said stem has a downwardly extending portion with a head so that the block can be snapped onto the downwardly extending portion to be secured by said head.

8. A keyboard as claimed in claim 1 wherein said base plate is metal and wherein each of said key carriers is formed of plastics material and is shaped to be held in an aperture in the base plate.

9. A keyborad as claimed in claim 1 wherein said base plate is of plastics material and is moulded integrally with said key carriers.

10. A keyboard as claimed in claim 1 and having an insulating layer over the conductors on the printed circuit board.