Electricity: circuit makers and breakers – Multiple circuit control – Multiple switch
Reexamination Certificate
2000-06-02
2001-05-29
Friedhofer, Michael (Department: 2832)
Electricity: circuit makers and breakers
Multiple circuit control
Multiple switch
C200S302200, C200S344000
Reexamination Certificate
active
06239391
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a keyboard assembly having an improved waterproof structure of a torsion bar receiving portion in each key switch provided with the torsion bar.
2. Description of the Related Art
On a keyboard of a computer or a word processor are arranged a large number of key switches
100
, for example like a keyboard B shown in FIG.
7
. Key tops are attached respectively to the key switches
100
so as to be pushed by a user's finger. The key tops are in various planar shapes, including a generally square shape, a half-cut shape thereof, a sideways long shape, and a deformed L shape.
As shown in
FIG. 8
, the key switches are each generally composed of a key top
110
and a key switch body
120
. The key top
110
comprises a top plate
111
to be pushed with a finger, a cylindrical stem portion
112
extending downward through an axis X of the key top from a lower surface of the top plate
111
, pawl portions
113
formed downwards on both sides of the stem portion
112
, and a skirt wall
114
extending downward from a peripheral edge portion of the top plate
111
.
The key switch body
120
comprises a housing
121
which houses the key switch body
120
therein, an inverted bowl-shaped rubber spring
122
connected to a lower end of the stem portion
112
, and a membrane switch
124
disposed below a convex-shaped pressing portion
123
which is formed centrally downward from a top part of the rubber spring
122
. The housing
121
is formed with a cylindrical socket
125
into which the stem portion
112
is inserted vertically slidably and is also formed with pawl engaging holes
126
for engagement with the pawl portions
113
to prevent extraction of the key top
110
from the key switch body
112
.
In the key switch of the above configuration, when the top plate
111
of the key top is pushed by a user's finger, as shown in
FIG. 9
, the stem portion
112
slides downwards through the socket
125
and a lower end thereof pushes the rubber spring
122
downward, causing the rubber spring to buckle. As a result, the pressing portion
123
of the rubber spring pushes the membrane switch
124
and causes the membrane switch to turn conductive. Upon release of the user's finger from the top plate
111
, the key top
110
reverts to its original position with a repulsive force of the rubber switch
122
, so that the membrane switch
124
turns OFF.
In each of the switches
100
of the above keyboard, key tops
110
A of such keys as shift key, space key, and tab key are each provided with a sideways long top plate
111
as in
FIG. 10
, but the shape, position and size of the stem portion
112
are set equal to those in a sectional key switch structure shown in FIG.
8
. Therefore, what is called a torsion bar, as a spring member, is incorporated in the key top so that the top plate
111
can be smoothly depressed right beneath even when it is depressed on an end side thereof.
The torsion bar, indicated at
130
, comprises a body portion
130
a
which is in a rectilinear shape and hook portions
130
b
extending in an inward L shape from both ends of the body portion. The body portion
130
a
is fitted in and engaged with support members
129
formed on the back side of the top plate
111
and is thus retained on the back side of the top plate. A pair of post-like support projections
131
of a hollow structure are erected on both sides of the housing
121
, with support holes
131
a
being formed in upper portions of the support projections
131
, respectively. The hook portions
130
b
of the torsion bar
130
are engaged respectively in the support holes
131
a,
whereby the torsion bar
130
is locked. With the torsion bar
130
thus locked, the stem portion
112
is inserted into the socket
125
. In this way the key tops
110
A of such keys as shift key, space key, and tab key are mounted onto the keyboard.
Drink cans or cups or the like may be placed on a table around the keyboard of this type and therefore it is considered preferable for the keyboard to have a waterproof structure.
Reference will now be made to a water entry route for an electric circuit portion of each membrane switch
124
in the interior of the keyboard. In each key switch
100
of the structure shown in
FIGS. 8 and 9
, water may enter the interior of the keyboard through the opening portions of the socket
125
and the pawl engaging holes
126
. However, since those opening portions are covered with the skirt wall
114
of the key top
110
, it is considered that a high waterproofness is ensured.
However, in the key top
110
A of, for example, a shift key or a space key having the torsion bar
130
shown in
FIG. 10
, the retaining holes
131
a
formed in the support projections
131
for retaining the hook portions
130
b
of the torsion bar
130
are positioned on end sides of the key top
110
A, so the opening portions of the retaining holes
131
a
may be a cause of water entry. In more particular terms, the support projections
131
are of a hollow structure and an electric circuit which constitutes the membrane switch
124
is provided below the support projections
131
, therefore, if water should enter the interior through the retaining holes
131
a
of the support projections
131
, there is a fear that the electric circuit of the membrane switch
124
may be corroded or damaged.
If the support projections
131
are formed not as a hollow structure but as a solid post-like structure and if bent portions for retaining the hook portions
130
b
of the torsion bar
130
are formed on end sides of the support projections respectively, it is required that the support projections
131
be formed in L shape. However, in forming the keyboard by molding a resin, if a plurality of solid L-shaped structures are erected about a housing plate in the keyboard, there arises the problem that the shape of a mold for molding the keyboard housing plate becomes complicated. More particularly, in the structures shown in
FIGS. 8
,
9
and
10
, the portion of the socket
125
, the portion of each pawl engaging hole
126
, and the portion of each support projection
131
are each of a vertically through structure, so it is easy to design a mold in case of molding the keyboard assembly with use of both upper and lower mold halves, but if a structure having L-shaped support members not of a through structure on an upper surface of the housing plate is to be formed by molding with use of upper and lower mold halves, the mold becomes complicated in shape and difficult to design.
SUMMARY OF THE INVENTION
With the foregoing as background, it is an object of the present invention to provide a keyboard assembly in which the portions around keys each having a torsion bar such as shift key, space key, and return key are rendered highly waterproof.
According to the present invention, which has been accomplished in view of the above-mentioned circumstances, there is provided, in the first aspect thereof, a keyboard assembly characterized in that a plurality of key top housings for supporting key tops are formed on a housing plate disposed below the key tops, post-like support members are formed sideways of each of the key top housings corresponding to key tops to which torsion bars are attached respectively, out of the plural key top housings, the support members being erected integrally from the housing plate and having a hollow structure, through holes are formed respectively in base end portions of the support members so as to extend through the housing plate, and a sheet member is disposed on a back side of the housing plate, the sheet member comprising waterproofing protuberances for closing the through holes in a waterproof manner, spring portions for pushing back the key tops upward, and a sheet body portion which makes the spring portions and the waterproofing protuberances integral with each other.
Since the through holes formed in the housing plate under the support members at a position corresponding to each of the key
Ito Hideki
Nishijima Akio
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Friedhofer Michael
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