Electricity: circuit makers and breakers – Multiple circuit control – Multiple switch
Reexamination Certificate
1994-03-30
2001-02-06
Friedhofer, Michael (Department: 2832)
Electricity: circuit makers and breakers
Multiple circuit control
Multiple switch
C200S517000, C200S341000, C200S345000
Reexamination Certificate
active
06184481
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to computer keyboards, and more particularly to key switches for computer keyboards.
Various key switches have been disclosed for use in computer keyboards. There is known a key switch comprised of a key base, a conductive rubber cone received inside the key base at the bottom and supported on a circuit board and having a rectangular hole above the rubber cone, a key cap mounted on the key base at the top and having a unitary plunger at the bottom inserted into the rectangular hole on the key base. The plunger comprises two opposite guide walls and two opposite locating walls disposed around the four sides, the locating walls respectively terminating in a hooked portion hooked on a respective retaining groove on the key base to limit the upward movement of the plunger within the key base. When the key cap is depressed, the conductive rubber cone is compressed by the plunger of the key cap to trigger a respective electrical contact on the circuit board causing an electrical signal provided to the computer. This structure of key switch is functional, however, the hooked portions of the plunger may be damaged easily when the key cap is frequently removed from the key base for cleaning. Furthermore, because the locating walls are respectively extended from the top of the plunger (inside wall of the key cap), they have a long arm of force, and therefore the hooked portions of the locating walls may be disconnected from the retaining grooves of the key base easily.
SUMMARY OF THE INVENTION
The present invention has been accomplished to provide key switches for computer keyboards which eliminates the aforesaid drawbacks. According to the present invention, the key cap and the plunger are separately made. The plunger is made of a springy material having a mounting slot at the top in the middle, and two spring strips respectively integrally extended downward from two opposite sides thereof in the middle and terminating in a respective hooked portion hooked on a respective retaining groove inside the key base. The key cap has a hollow projecting rod on the inside fitted into the mounting slot causing the plunger fastened to the key cap.
REFERENCES:
patent: Re. 30435 (1980-11-01), Fukao
patent: 4609791 (1986-09-01), Abbat
patent: 4733036 (1988-03-01), Koizumi et al.
patent: 5066842 (1991-11-01), Yamagata et al.
patent: 5372442 (1994-12-01), Wang
Browdy and Neimark
Friedhofer Michael
Silitek Corporation
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