Note: Descriptions are shown in the official language in which they were submitted.
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SUMMARY OF THE INVENTION
The present invention relates to a keyboard switch
of the type conventionally used in connection with an under-
lying membrane switch array. A specific purpose of ~he in-
vention is to provide such a keyboard switch which has a
lever pivotally mounted on the key housing and cammed away
from a switch closure position until such time as the plunger
or key has moved inwardly a given distance.
A primary purpose of the invention is a keyboard
switch of the type described in which the lever causing a
switch closure is held away from a switch closing position
until the operating plunger or key has moved inwardly a given
distance, after which the switch closing lever will suddenly
move to a switch closure position. This provides a tactile
feel to indicate when a switch closure has in fact taken
place.
Another purpose is a keyboard switch of the type
described including sloped cam surfaces which allow the
actuator lever to gradually apply a switch closing force
during inward movement of the plunger.
Another purpose is a keyboard switch of the type
described including sloped cam surfaces which allow the
actuator lever to gradually apply a switch closing force
during inward movement of the plunger.
Another purpose is a keyboard switch of the type
described in which the return spring also provides the force
required for switch closure movement.
Another purpose is a simply constructed, reliably
operable switch of the type described.
Other purposes will appear in the ensuing specifi-
cation, drawings and claims.
BRIEE' DESCRIPTION OF T~E DRAWINGS
The invention is illustrated diagrammatically in
the following drawings wherein:
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Figure 1 is a top plan view of the switch assembly
with the cap removed, but illustrated in broken lines,
Figure 2 is a section along plane 2-2 of Figure 1 illus-
trating the plunger in an unoperated position,
Figure 3 is a section, similar to Figure 2, but illus-
trating the plunger in a switch closure position,
Figure 9 is a view of the lever and plunger taken along
the line 4-4 of Figure 1,
Figure 5 is a view similar to Figure 4, but showing
the plunger in a depressed position,
Figure 6 is a partial side view in section taken along
plane 6-6 of Figure 1,
Figure 7 is a top plan view of the housing and the
lever,
Figure 8 is a top plan view of the plunger,
Figure ~ is a side view of the plunger,
Figure 10 is a side view of the plunger as viewed from
the right side of Figure 9,
Figure 11 is a bottom view of the plunger,
Figure 12 is a section along plane 12-12 of Figure
9,
Figure 13 is a section along plane 13-13 of Figure
9,
Figure 14 is a section, similar to Figure 2, illustrat-
ing an alternate embodiment of the invention, i.e., a linear
switch,
Figure 15 is a plan view of the housing for the linear
switch of Figure 14, and
Figure 16 is a side elevation view of the plunger for
the linear switch of Figure 14.
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DESCRIPTION OF THE PREFERRED EME30DIMENTS
The present invention relates to a keyboard switch
in which the point of closure or "make point" is dependent on
the geometry of the switch parts and not on the force applied
to the switch. In other words, the ss~it~h will close only after
the plunger has moved inwardly a given distance. Only upon such
movement will the switch parts assume positions wherein the
geometry of the parts allows application of a closing force to
the membrane switch. The application of the closing force may
be gradual or sudden. In the former case, the force applied
to the membrane switch is a smooth, continuous function of the
plunger travel; there are no sudden changes in the force. Since
the force-deflection curve is generally a straight line, this
switch is called a linear switch. In the latter case, an effectively
instantaneous jump in the force-deflection curve is deliberately
created so the user can feel it and know when the switch has
closed. This is called a tactile switch. In both the linear
and tactile switches the actuator lever is restrained from applying
a switch closing force until the plunger has moved inwardly a
given distance.
The tactile switch of the present invention finds utility
in keyboards, such as computer terminals, typewriters, calculators
and other applications in which it is desirable that the key
have a very low profile. For example, the total height of the
entire key structure disclosed herein normally will not be greater
than one-half inch. With a key construction of this dimension,
the travel of the key actuator from the unoperated to the operated
position will normally be quite small. In the present instance
such travel may be on the order of slightly more than one-eighth
inch. Heretofore, it has been a problem in keyboards of this
size for the operator of the key to feel confident that in fact
the key has been pressed in a manner as to insure a switch closure
in the underlying membrane switch array. Thus, it is necessary
for there to be a tactile feel in operation of the key or some
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indication to the user that in fact the key has been pressed
to the degree necessary to cause operation of the switch. In
one aspec~ the pres~nt invention is specifically directed to
such a tactile key and to a means for providing a tactile feel
in key operation. The tactile feel must not be a gradual sen-
sation, but, rather, there must be an abrupt or sudden movement
in operation of the key so that the operator is assured and in
fact completely confident that switch operation has taken place.
Considering first Figllres 1, 2 and 3, the tactile
switch includes a housing indicated generally at 10 having a
central opening 12 mounting a reciprocal plunger 14. The plunger
may mount a keycap 16 of a conventional size and shape for key-
board operation. Pivotally mounted on the housing and in position
to be in cooperative contact with plunger 14 is a lever 18 which
will be described in more detail hereinafter.
Housing 12 is seated upon a membrane switch array which
may consist of the conventional lower substrate 20, intermediate
spacer 22 and membrane 24. Conventionally, the membrane and
substrate will have electrical contacts thereon which normally
will be positioned beneath plunger 14. There will be the usual
opening 26 in the spacer beneath the switch so that movement
of keycap 16 and thus plunger 14 can effect a switch closure
between the membrane and substrate.
Housing 10 has a cylindrical wall 28 which defines
opening 12 and that portion of housing 10 beneath opening 12
may have arcuate slots 30 just inside of wall 28, with slots
30 cooperating with arcuate projections 32 on the bottom of the
plunger to maintain align~ent and relative position between these
two elements during switch operation. The bottom of the housing
may have an opening 31 which will permit lever 18 to effect a
switch closure. Further, in order to maintain the plunger within
opening 12, housing 10 has oppositely-disposed hook elements
34, illustrated in Figure 6, which will ride in cooperating grooves
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36 on the sides of the plunger. Note that grooves 36 have a
lower surface 38 forming a stop which prevents removal of the
plunger from the housing opening. When the plunger is initially
inserted during assembly, the plunger will be pushed past hooks
34 which will flex to permit assembly. Once assembled, the plunger
cannot be removed from the housing.
Lever 18 has a pivot portion 40 which is positioned
within a slot 42 of housing portion 44 formed at one corner of
the housing. Lever 18 is accordingly mounted for pivotal movement
10 between the Figure 2 and 3 positions. Lever 18 has a spring
support portion 46 which extends through an opening in wall 28
of the housing and provides a spring seat 48 which will seat
a coil spring 50 which is captured between the spring seat and
an inner surface 52 of plunger 14. In addition, spring seat
portion 46 of lever 18 includes a downward projecting boss 54
which is positioned, as specifically illustrated in Figure 3,
to provide a closure of the underlying membrane switch by forcing
a portion of membrane 24 through opening 26 in the spacer so
that there is contact between the electrical conductive areas
20 of the membrane and substrate.
The side of plunger 14 which faces lever 18 has a reset
ramp 56 and a threshold ramp 58 with the reset ramp and threshold
being separated by an open area or slot 60. To cooperate with
the cam areas on plunger 14, lever 18 has a nose 62 which is
positioned in alignment with reset ramp 56 and an arm 64 which
cooperates with threshold 58 to hold the lever in the non-actuated
position of Figures 2 and 4 until such time as arm 64 is in align-
ment with threshold 58. Lever 18 further has a stop 66 positioned
directly behind arm 64 which restricts movement of the arm to
30 a single plane.
The unoperated position of the switch is illustrated
in Figure 2. Coil spring 50 is seated upon that portion 48 of
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lever 18 which extends into opening 12 and the spring maintains
plunger 14 and keycap 16 in the up or unoperated position. As
the keycap, and hence the plunger, are depressed during switch
operation, spring 50 will be compressed as the keycap moves toward
the underlying membrane switch array. However, as illustrated
in Figure 4, lever 18 will be maintained in the Figure 2 position
because its arm 64 will bear against the face of threshold 58.
Only when plunger 14 has been depressed a sufficient distance
for arm 64 to clear threshold 58 can there be inward movement
of the lever. Once the arm has cleared the threshold, the lever
will suddenly move to the position of Figure 3 to effect a switch
closure. The force which will drive the lever through such movement
is that provided by spring 50. The spring is compressed as the
keycap is moved inward. Once the lever is permitted to move
to the switch closure position of Figure 3, the compressed spring
will provide the necessary force to effect such sudden movement.
During reset or outward movement of the keycap nose
62 of lever 18 will bear against reset ramp 56. The cooperation
between these two surfaces will cause the lever to pivot in a
clockwise direction as the force of spring 50 moves the keycap
back to the position of Figure 2. Arm 64, as it is bearing against
threshold 58, will to some degree retard the outward movement
of the keycap, but the arm will flex in the single plane of its
movement, as indicated in broken lines in Figure 5, as the plunger
and keycap retract. Stop 66 will prevent the arm from moving
in any direction other than in the vertical plane parallel with
threshold 58. Thus, the arm is protected by stop 66 and is per-
mitted the flexing movement required so that the keycap and plunger
can retract. Movement of the lever during the retraction of
the plunger i5 controlled by nose 62 riding upon reset ramp 56.
Of particular importance in this aspect of ~he invention
is the provision of a tactile feel driving switch closure. The
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sudden movement can be felt by the operator of the key, thereby
giving the required tactile sensation to tell the operator that
in fact the key has been moved to a switch closure positionO
The switch closure force is effected by the compression cf the
return spring during the downward movement of the key. The spring
is compressed until such time as the plunger has moved inwardly
a distance to permit the sudden movement required for a switch
closure and this sudden movement is effected by the stored force
in spring 50.
We show the compound movement of the rocker member
by pivotal movement in one plane and by flexing in another plane.
The same type of compound movement can be derived by having the
rocker mounted on a universal pivot or ball so that it can pivot
in two planes.
Figures 14-16 illustrate an alternate embodiment of
the invention. This is the linear switch referred to above.
Linear switch 70 has three main parts; a housing 72, a plunger
74 and a spring 76. It will be understood that the switch is
designed for use with a membrane switch array mounted on a base
plate, although the membrane switch array and base plate are
not shown. The switch is attached to the base plate by a pair
of expandable rivets 78.
The plunger 74 includes a body portion 80 to which
a cap 82 is connected. The cap engages the spring 76 as shown
in Figure 14. An appropriate key top (not shown~ would be attached
to the cap 82. A pair of integrally formed legs 84 extend from
either side of the body 80. The legs 84 carry hooks 86 near
their ends. A cam surface 88 is formed on one side of the body
80. As shown in Figure 14, the cam surface has a gradual, sloped
configuration.
The housing 72 includes a generally flat base 90 having
a central opening 92 therein. A pair of upstanding walls are
located in facing relation on either side of the opening 92.
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Each wall includes an elongated lower portion 94 and a ~-shaped
upper portion 96 which extends above the lower portion 94. The
bight of the U-shaped wall includes a groove or channel 98 in
which the hooks 86 of the plunger ride. The groove ~8 extends
about halfway up the wall portion 96. Its terminus forms an
up stop for the plunger. The lower portions 94 of the walls
provide a base on which the spring 76 bottoms.
Other features of the housing include a chamber 100
in which an optional cam follower may be inserted to provide
an alternate action-type switch. The housing also has an up-
standing spring support wall 102. Along with the wall portions
94, the spring support 102 provides a base on which the spring
76 rests.
An actuator lever is shown generally at 104. The lever
is disposed above the housing opening 92 and between the walls
94,96. The actuator lever 104 includes an elongated, upright
bracket 106. The bracket is pivotally attached to the base of
the housing by a flexible hinge 108, commonly referred to as
a living hinge. A pair of extension pieces 110 are connected
to the top of the bracket and extend downwardly therefrom. The
extensions merge into a pair of legs 112 which extend generally
horizontally across the bottom of the housing. The legs 112
extend beyond the wall portions 96 and terminate with a pair
of upturned feet 114. Each foot 114 has two tabs 116 which form
a slot between them for retaining the spring 76, as best seen
in Figure 14. The legs 112 are connected by a strap 118. On
the underside of the strap there is a knob 120 which is the part
that actually contacts the membrane switch.
A cam surface 122 is formed at the upper end of the
bracket 106. This surface is in the nature of a cam follower
as it engages the cam surface 88 on the plunger 74.
The operation of the linear switch is as follows.
The plunger body 80 and legs 84 are disposed in the housing between
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the U-shaped walls 96. The hooks 86 slide in the grooves 98
and are retained therein. The spring 76 is compressed between
the plunger cap 82 and the lower wall portions 94, the spring
support 102 and the feet 11~ of the actuator lever 104. Thus,
the spring urges the lever toward the membrane switch, i.e., in
a counterclockwise direction (as seen in Figure 14) about the
hinge 108. When the switch is in the unoperated~ rest position
(as in Figure 14) the lever is restrained from moving into a
membrane switch closing position by the engagement of the cam
follower 122 on the cam surface 88. When a user pushes the plunger
inwardly, the cam surface 88 allows the lever 104 to pivot about
the hinge 108 and bring the knob 120 into contact with the membrane
switch. The compressed spring acts on the lever to gradually
apply a membrane switch closing force through the knob 120.
As can be seen in Figure 14, the cam surface 88 has a sloped
configuration. This permits the gradual application of switch
closing force in a smooth and continuous manner. When the user
releases the plunger the spring 76 causes the plunger to move
outwardly in the housing while at the same time the cam surface
88 resets the actuator lever 104 to its rest or non-operative
position. It can be seen that the cam surface 88 prevents the
lever from moving to a switch closing position until the plunger
has moved inwardly a given distance. That distance can be regulated
by the shape of the cam surface.
It will be understood that the cam surface 88 does
not have to have a smooth and continuous configuration. It could
also have a sharp step or drop-off which would prevent any movement
of the lever until the last possible moment. Then the lever
would be released suddenly with the switch closing force being
applied effectively instantaneously. This would provide a tactile
feel as in the switch of Figures 1-13.
Whereas the preferred form of the invention has been
shown and described herein, it should be realized that there
may be many modifications, substitutions and alterations thereto.
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