Electricity: circuit makers and breakers – Electric switch details – Actuators
Reexamination Certificate
2001-05-17
2003-01-07
Evanisko, Leslie J. (Department: 2854)
Electricity: circuit makers and breakers
Electric switch details
Actuators
C400S490000, C400S495000
Reexamination Certificate
active
06504121
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a keyboard switch suitable for use with various kinds of equipment such as personal computers, word processors, and the like, and particularly to a keyboard switch having keytops configured to be supported by means of pantograph mechanisms.
FIG. 1
illustrates an example of the heretofore proposed keyboard switch having such configuration in which on a plate
11
made of a metal plate, for example there is disposed a membrane sheet (contact sheet)
12
on which a base
13
made of a metal plate is positioned. The membrane sheet (contact sheet)
12
comprises,a pair of laminated contact layers
12
B and
12
C spaced apart by a spacer
12
A, and a movable contact pattern and a pair of fixed contact patterns (not shown) formed on the opposed surfaces of the contact layers
12
B and
12
C, respectively, the arrangement being such that the contact layer
12
B is adapted, when depressed toward the contact layer
12
C, to bring the movable contact pattern into contact with the pair of fixed contact patterns. It is to be noted that there are a plurality of the sets of the movable contact pattern and the fixed contact patterns are provided so that any selected one of the sets may be actuated to make contact.
As shown in
FIG. 2
, the base
13
has generally square openings
13
A formed therethrough, each for one of the sets of contact patterns, and is formed with a pair of first journal bearing portions
13
B and a pair of second journal bearing portions
13
C projecting oppositely from the membrane sheet
12
along the two opposed side edges of each opening
13
A. The pair of first journal bearing portions
13
B are opposed to each other and are formed in the form of a protrusion having a generally trapezoidal contour in cross-section when the base
13
is formed by a drawing process, for example while the pair of second opposed journal bearing portions
13
C are formed in the form of a protrusion having a generally, semi-circular contour in cross-section when the base
13
is formed by a drawing process (FIG.
1
).
A pair of links
14
and
15
comprising a pantograph mechanism
24
is disposed on the membrane sheet
12
for each of the sets of the contact patterns with the pair of links
14
and
15
supported at their one ends in the associated journal bearing portions
13
B and
13
C, respectively.
As shown in
FIGS. 3A and 3B
, the first link
14
is generally U-shaped and comprises a shaft
14
A and a pair of legs
14
B extending from the shaft at the opposite ends thereof and having stud shafts
14
C protruding outwardly therefrom at their forward ends and away from each other. The legs
14
B further have columnar (solid cylindrical) bosses
14
D protruding inwardly toward each other from the inside surfaces thereof intermediate their opposite ends. In addition, the legs
14
B have stops
14
E protruding inwardly toward each other from the inside surfaces thereof adjacent their forward ends.
The second link
15
, as shown in
FIGS. 4A and 4B
, comprises a generally annular frame-like portion
1
5
A having a pair of spaced apart extensions
15
B extending in the same direction from the outer periphery of the frame-like portion along one semi-circular segment (forward end side) thereof. The two extensions
15
B have stud shafts
15
C extending inwardly toward each other therefrom adjacent the forward ends thereof. Further, a pair of stud shafts
15
D extend outwardly from the base end portion (the other semi-circular segment) of the frame-like portion
15
A in parallel to the stud shafts
15
C. The frame-like portion
15
A is formed in the diametrically opposed outside surfaces in the center thereof with shaft receiving holes
15
E, respectively. The first and second links
14
,
15
are typically made as molded parts of synthetic resin such as polyacetal (POM).
As shown in
FIG. 2
, the links
14
and
15
are configured such that the frame-like portion
15
A of the link
15
is accommodated between the opposed legs
14
B of the link
14
with the inside surfaces of the legs
14
B facing the outside surfaces of the frame-like portion
15
A and with the pair of bosses
14
D matingly engaged in the corresponding holes
15
E of the link
15
whereby the two links
14
and
15
are assembled and connected together for relative pivotal movement. It should be noted here that the stops
14
E provided on the link
14
serve to limit the relative movement of the links
14
and
15
toward the overlapping relation beyond a predetermined position.
Prior to superposing the membrane sheet
12
over the base
13
, the pair of stud shafts
14
C of the link
14
are inserted in the corresponding journal bearing portions
13
B of the base
13
from the membrane sheet
12
side to be rotatably and movably (slidably) supported therein, while the pair of stud shafts
15
D of the link
15
are likewise inserted in the corresponding journal bearing portions
13
C of the base
13
to be rotatably supported therein.
On the other hand, the shaft
14
A of the link
14
is rotatably fitted in a pair of journal bearings
16
A formed in the bottom side of the keytop
16
while the pair of stud shafts
15
C of the link
15
are rotatably and slidably supported in corresponding slide bearings
16
B formed in the bottom side of the keytop
16
.
A dome-like rubber member
17
is mounted on the membrane sheet
12
within the opening
13
A in the base
13
and extends through the central aperture of the frame-like portion
15
A so as to be is interposed between the keytop
16
and the membrane sheet
12
. The rubber member
17
comprises a cylindrical portion
17
A fitted over a projection
16
C extending from the keytop
16
, and a dome portion
1
7
B connecting with the cylindrical portion. The dome portion
17
B has a push-button portion
17
C projecting inwardly from the ceiling thereof for pressing down on the corresponding contact region of the membrane sheet
12
.
With the keyboard switch constructed as described above, downward pressing operation on the keytop
16
will move the keytop
16
generally parallel to the face of the base
13
by means of the links
14
and
15
in the form of the pantograph mechanism while the keytop
16
presses on the rubber member
17
so that the dome portion
17
B is deformed and collapsed down. Through this process, the user will get a good tactile feeling while at the same time the contact region of the membrane sheet
12
is pressed on by the push-button portion
17
C whereby the electrical continuity is established. On the contrary, upon the downward pressure on the keytop being released, the rubber member
17
returns to its original position by its resilient restoring force to cut off the electrical continuity through the contact region whereby the keytop
16
is restored to its original position.
It should be noted here that an increasing reduction in the thickness of the keyboard switch of the type discussed herein is accompanied with a reduction in component space allowed to be allotted for the pantograph mechanism (linkage), inevitably leading to an increasing demand for reduction in both size and vertical profile (thickness) of the pantograph mechanism. Such a situation has resulted in a decrease in the rigidity of the linkage, and hence a greater vulnerability of the linkage to deformation.
More specifically, comparison between the links
14
and
15
has shown that the U-shaped link
14
is more vulnerable to deformation than the link
15
comprising the frame-like portion
15
A as a central body portion. Moreover, there is more freedom of motion involved in the support of the stud shafts
14
C provided at the forward ends of the legs
14
B of the link
14
by the journal bearing portions
13
B of the base
13
than in the support of the stud shafts
15
D of the link
15
by the journal bearing portions
13
C of the base
13
. For this reason, when a force to pull the keytop
16
upward from its unactuated state is applied to the keytop as in an attempt to remove dust, for instance, such a situation may o
Culler Jill E.
Evanisko Leslie J.
Gallagher & Lathrop
Hosiden Corporation
Lathrop, Esq. David N.
LandOfFree
Keyboard switch having leg dislodgement preventing mechanism does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Keyboard switch having leg dislodgement preventing mechanism, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Keyboard switch having leg dislodgement preventing mechanism will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3048232