Key switch unit for computer keyboards

• US 5,565,865 A
• Filed: 03/27/1995
• Issued: 10/15/1996
• Est. Priority Date: 03/24/1995
• Status: Expired due to Fees

• Current Assignee: Henry So
• Original Assignee: Henry So
• Inventors: So, Henry
• Primary Examiner(s): Hofsass, Jeffery
• Assistant Examiner(s): Edwards, Jr., Timothy
• Application Number:
  US08/411,016
• Time in Patent Office: 568 Days
• Field of Search: 400/490, 400/491, 400/491.1, 400/495, 400/496, 341/20, 341/22
• US Class Current: 341/20
• CPC Class Codes: G06F 3/0202 Constructional details or processes of manufacture of the input device
• 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 2217/004 Larger or different actuating area
• CPC Class Codes: H01H 2221/026 Guiding or lubricating nylon
• CPC Class Codes: H01H 2221/03 Stoppers for on or off position
• CPC Class Codes: H01H 2221/056 Modular conception
• CPC Class Codes: H01H 2221/064 Limitation of actuating pressure
• CPC Class Codes: H01H 2229/022 Modular assembly

Abstract

A key switch unit including a key holder frame having a plurality of key holders respectively mounted on the rubber cones of a conductive rubber pad above a membrane circuit, and one L-shaped key switch and a plurality of elongated key switches and a plurality of square key switches respectively mounted on the key holders and depressed to trigger the membrane circuit to produce a respective electric signal, wherein the key holders each has a center through hole and an inside annular flange within the center through hole; the square key switches each has a stepped long plunger inserted into one key holder; the L-shaped key switch and the elongated key switches each has a stepped long plunger and at least one stepped short plungers respectively inserted into the longitudinal center through hole on a respective key holder on the key holder frame; the stepped long plungers of the square key switches and the L-shaped key switch and the elongated key switches each comprises a thicker upper part inserted into the longitudinal center through hole on the respective key holder and suspended above the respective inside annular flange, a thinner lower part passed through the respective inside annular flange and stopped above the respective rubber cone, the thicker upper part being stopped above the respective inside annular flange to stop the at least one stepped short plunger from triggering the membrane circuit when one L-shaped key switch or one elongated key switch is depressed.

Claims

1. A key switch unit for computer keyboards, comprising:

a membrane circuit having a plurality of electric contacts;

a conductive rubber pad mounted on said membrane circuit and having a plurality of rubber cones respectively disposed above said electric contacts;

a key holder frame mounted on said conductive rubber pad and having a plurality of key holders respectively disposed above said rubber cones, each key holder comprising a longitudinal center through hole and an inside annular flange around said longitudinal center through hole at a bottom side;

one L-shaped key switch and a plurality of elongated key switches and a plurality of square key switches respectively mounted on said key holders and depressed to trigger a respective electric contact in producing a respective electric signal;

wherein said square key switches each comprises a key cap and one stepped long plunger inserted into the longitudinal center through hole on one key holder on said key holder frame;

wherein said L-shaped key switch and said elongated key switches each comprises a key cap, one stepped long plunger and at least one stepped short plungers respectively inserted into the longitudinal center through hole on respective key holder on said key holder frame;

wherein the stepped long plungers of said square key switches and said L-shaped key switch and said elongated key switches each includes;

a thicker upper part inserted into the longitudinal center through hole on the respective key holder and suspended above the respective inside annular flange;

a thinner lower part passed through the respective inside annular flange and stopped above the respective rubber cone, a plurality of longitudinal ribs raised from a periphery of the thicker upper part and terminating in a respective end portion of the thicker upper part, and a plurality of hooks respectively extended from the thinner lower part at a bottom side of the thinner lower part and stopped below the inside annular flange of the respective key holder, end portions of said longitudinal ribs being stopped at the inside annular flange of the respective key holder, the at least one stepped short plunger being substantially same as the one stepped long plunger except a bottom portion of the thinner lower part being cut off so as to prevent the at least one stepped short plunger of the respective key switch from triggering said membrane circuit when one L-shaped key switch or one elongated key switch is depressed, so that a set of square key switches can be replaced by one L-shaped key switch or one elongated key switch without changing the conductive rubber pad and the membrane circuit, by inserting the one stepped long plunger of the L-shaped key switch or the one stepped long plunger of the elongated key switch into the respective longitudinal center through hole, which triggers the respective electric contact representing the one of replaced square key switches without triggering the respective electric contacts representing the other replaced square key switches.

2. The key switch unit of claim 1 wherein said key holders each comprises a plurality of longitudinal grooves around the respective longitudinal center through hole above the respective inside annular flange, which receive the longitudinal ribs of the respective stepped long plunger, and a conical bottom chamber below the respective inside annular flange, which receives one rubber cone.

3. The key switch unit of claim 1 wherein one key switch is depressed, the upper part of the respective stepped long plunger is stopped at the inside annular flange of the respective key holder.

4. The key switch unit of claim 1 wherein the key cap of each key switch has a flat bottom side spaced above the respective key holder, the flat bottom side of the key cap is stopped above the respective key holder to limit the down stroke of the respective key switch when the inside annular flange of the respective key holder is damaged by the stepped long plunger of the respective key switch.