Electricity: circuit makers and breakers – Electric switch details – Cases and bases
Reexamination Certificate
2000-02-11
2001-10-09
Scott, J. R. (Department: 2832)
Electricity: circuit makers and breakers
Electric switch details
Cases and bases
C200S341000, C200S345000, C200S517000
Reexamination Certificate
active
06300582
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a dustproof and droplet-proof keyswitch for use in a hazardous environment with dust and droplets, which also is of lower cost and easy assembly.
BACKGROUND OF THE INVENTION
With reference to
FIGS. 6
to
8
, a conventional keyswitch comprises at least a key cap
6
and a hollow plunger
7
connected with the key cap
6
. The key top
61
of the key cap
6
has a cross-shaped pole
62
extending from its bottom surface that engages two pairs of ribs
71
within the hollow plunger
7
. The cross-shaped pole
62
should be tightly fit with the pairs of ribs
71
to facilitate the key pressing operation. However, the key cap
6
is made with a predetermined rigid material, and the hollow plunger
7
must be made with flexible material to allow tight fitting with the key cap
6
. Material and manufacture costs are thereby increased. Moreover, the top portion of the plunger
7
is liable to crack when being assembled with the rigid key cap
6
.
The plunger
7
has two bevels
72
formed on both sides thereof. The bevels
72
engage two lengthwise slits
83
formed in the inner sleeve
82
housed by an outer sleeve
81
of a plunger stage
8
. The plunger
7
has two annular shaped portions
73
formed thereon to receive the bottoms of outer and inner sleeves
81
and
82
such that the space within the outer sleeve
81
is sealed. This kind of keyboard keyswitch is employed in cash registers and is formed with a bump
74
on the bottom of the plunger
7
to contact a switch sheet. However, this keyboard is of a two-piece design, and the structure thereof is complicated. Moreover, an elastic ring
9
is arranged on a step portion
84
on top of the outer sleeve
81
to provide restoring force and prevent the entry of dust and droplets. However, the structure is not satisfactory and requires improvement.
It is the object of the present invention to provide a dustproof and droplet-proof keyswitch wherein a key cap and a plunger are inserted into a stage on a base plate, and an elastic member between the stage and the key cap provides a seal for the keyswitch against dust and droplet entry. Therefore, the keyswitch can be used under severe conditions such as in a dusty environment or when the keyboard has spilled upon it a liquid such as tea or coffee.
To achieve the above objects, a dustproof and droplet-proof keyswitch comprises a base plate with at least one stage formed thereon, each having a step portion on top of the stage; an elastic member arranged on the step portion; a key cap mounted on the elastic member and having a plunger inserting into the stage. The plunger has an elastic plate clamped between a pair of grooves and having a hook on a lower end thereof; the hook having a beveled lower end thereof latched with the stage when the key cap is released. The stage has at least one projecting rib on an inner side thereof corresponding to at least one notch on the plunger to provide a clamping effect.
REFERENCES:
patent: 5386091 (1995-01-01), Clancy
patent: 5396038 (1995-03-01), Yamada
patent: 5430267 (1995-07-01), Ozeki et al.
patent: 5438177 (1995-08-01), Fagan
patent: 5493087 (1996-02-01), Yoshida et al.
patent: 5525979 (1996-06-01), Engle et al.
patent: 5684279 (1997-11-01), Burgett
patent: 5718327 (1998-02-01), Wu
Rosenberg , Klein & Lee
Scott J. R.
Silitek Corporation
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