Snap-action pushbutton switch with click sound

This invention provides a pushbutton switch which produces a click sound, the loudness of which is easily variable. In response to the vertical movement of operating cams of a pushbutton, a plate spring moves up and down. The moment when the edge of the operating cams trips over click spring portions of the plate spring, a force is applied to the plate spring so that the plate spring hits the inner top wall or bottom wall of a housing. In this manner, the pushbutton switch provides both a snap feeling and a click sound.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a pushbutton switch, and more particularly to a 
pushbutton switch for use on keyboards of electronic typewriters, word 
processors, computer terminal units or the like, which produce a snap 
feeling and a click sound. 
2. Related Art 
In order that a pushbutton switch for electronic typewriters and other 
machines may be easy for the operator to manipulate with reduced fatigue, 
the switch preferably produces a click or snap feeling and a click sound 
when pressed. As an example of a known pushbutton switch adapted to give 
such a snap feeling and a click sound, there is the device disclosed in 
Japanese laid-open Utility Model Application No. 19928/1986. 
Thus, as shown in FIGS. 7 and 8, this pushbutton switch comprises a housing 
1, a pushbutton 2 accommodated in said housing 1 in such a manner that it 
can be vertically movable within and with respect to said housing 1, a 
switch element 3 which is disposed within said housing 1 and which 
responds to the vertical movement of said pushbutton 2, and a plate spring 
4 which is disposed in said housing 1 and adapted to produce a feeling and 
a click sound in response to the vertical movement of said pushbutton 2. 
As the pushbutton 2 is depressed, it presses an arm portion 4a extending 
from the top of said plate spring 4, whereupon a bend portion 4b of said 
plate spring 4 is displaced away from an inner lateral wall 1a of said 
housing 1 toward the pushbutton 2 until the bend portion 4b hits a 
projection 1b of housing 1 to produce a click sound. In the course, a 
pressure plate spring 5 is also pressed but does not yet actuate the 
switch element 3. As the pushbutton 2 is further depressed, it rides on a 
tip portion 4c of the arm 4a of said plate spring 4 to thereby produce a 
click or snap feeling. Furthermore, the pushbutton 2 presses the tip 
portion 4c of plate spring 4 in a transverse direction to let the plate 
spring 4 return to the inner lateral side 1a of housing 1, whereupon a 
click sound is produced. At the same time, the pushbutton 2 actuates the 
switch element 3 through the pressure spring 5. The pushbutton 2 is biased 
by a coil spring 6 in a release direction (toward the upper position). 
In this switch construction, as the pushbutton 2 is depressed, the plate 
spring 4 is flexed to cause its bend portion 4b to hit the lateral wall 1a 
of the housing 1 and the projection 1b to thereby produce click sounds. 
However, since the amount of flexure of the plate spring 4 is fixed, the 
loudness of the click sound cannot be varied, even though it is desirable 
to vary the loudness of kinds of switches. 
SUMMARY OF THE INVENTION 
It is an object of this invention to provide a pushbutton switch whose 
click sound level can be easily varied. Other objects and advantages of 
this invention will become apparent as the following description proceeds. 
The pushbutton switch of this invention comprises a housing, a pushbutton 
which is disposed within the housing in such a manner that it can 
reciprocate in a vertical direction and is biased in a release direction, 
a switch element which is disposed within the housing and is actuated in 
response to the vertical movement of said pushbutton, and click means 
which is disposed within the housing and adapted to produce a snap feeling 
and a click sound in response to the vertical movement of the pushbutton. 
The click means comprises an operating cam which moves vertically with the 
pushbutton as a unit and a plate spring having an upright portion adapted 
to move vertically along the inner lateral wall of the housing, with the 
vertical movement thereof being limited by abutment against the inner top 
and bottom walls of the housing. A click spring portion extends into the 
range of reciprocating motion of the operating cam, the pushbutton being 
vertically movable over a range greater than that of the plate spring. The 
operating cam and the plate spring are movable together in engagement, so 
that when the operating cam trips over the click spring portion, a 
resilient force acting in the direction from the operating cam portion to 
the inner top wall or bottom wall of the housing is imparted to the plate 
spring resilient force acting in the direction from the operating cam 
portion to the inner top wall or bottom wall of the housing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The preferred embodiments of this invention are described in detail below 
with references to the accompanying drawings. 
Referring to FIGS. 1 through 4 showing a preferred embodiment of this 
invention, the pushbutton switch of this invention, indicated at 10, 
comprises a housing 11, a pushbutton 12, a switch mechanism 13, a click 
means 14, a pressure spring 15 and a release spring 16. 
The housing 11 comprises an upper case 17 and a lower case 18, both of 
which are generally box-shaped, with the upper case 17 being dimensioned 
to fit into the open space of the lower case 18. After the internal 
component parts, including the pushbutton 12, are built into the upper 
case 17, the lower case 18 is mated with the upper case 17, for example by 
a snap-in means (not shown). 
The pushbutton 12 is inserted into a hole 19 provided in the upper case 17 
and is supported so as to be vertically movable by means of pairs of 
projections 20, 20 and 21, 21 disposed on the inner sides of the opposite 
lateral walls of the top case 17. The pushbutton 12 is provided with a 
pair of operating cams 22 formed on the lateral sides 12A facing said pair 
of projections 20, 20. The operating cam 22 has a ridge 22A in the central 
portion thereof to define inclined surfaces 22B and 22C. The cam 22 is 
disposed as projecting between the pair of projections 20, 20 toward the 
inner side 17B of the lateral wall of the upper case 17 and is biased 
upwardly at all times by the release spring 16 interposed between the 
pushbutton 12 and the lower case 18. This release spring 16 is constituted 
by a coil spring and its tip is accommodated in, and positioned by, a 
recess 24 formed in the bottom of said pushbutton 12, while its lower end 
is engaged and positioned by a projection 23 formed on the center of the 
bottom wall of the lower case 18. 
The switch mechanism 13 is accommodated between the projections 21, 21 of 
the upper case 17 and the inner surface 17A of the lateral wall of the 
upper case 17. The pressure spring 15 is interposed between this switch 
mechanism 13 and the pushbutton 12. The top end 15A of the pressure spring 
15 is supported by and between the switch mechanism 13 and upper case 17, 
with the bottom end 15a slanting inwardly into the range of reciprocating 
movement of the pushbutton 12 which lies below the position of the 
pushbutton 12 prior to depressing. 
The plate spring 26, together with said operating cam 22, constitutes the 
click mechanism 14. As illustrated in detail in FIG. 3, this plate spring 
26 has an upright portion 27, a pair of click spring portions 28 extending 
toward the front from the upright portion 27 through respective bottom 
bends 29, and a bend 30 extending approximately at ,a right angle as 
illustrated relative to the upright portion 27. Furthermore, said upright 
portion 27 has lateral portions 31, each of which is bent approximately at 
right angles toward the front. The plate spring 26 is loosely mounted 
between the pair of projection 20, 20 of the upper case 17 and the inner 
side 17B of the lateral wall in such a manner that it can move vertically 
as its lateral portions 31 are guided by and between them. In this loosely 
fitted condition, the top bends 28a of the click spring portions 28 are 
abutted against the lateral wall 12A of the pushbutton 12. 
Operation of the pushbutton switch thus constructed is explained with 
reference to FIGS. 1, 2 and 4. 
First, prior to depressing the pushbutton 12, the operating cam 22 is in 
the uppermost position beyond the top bend 28a of the click spring portion 
28. The plate spring 26 is positioned with its bottom bend 29 abutted 
against the inner bottom wall of the lower case 18, while the top bend 28a 
of the click spring portion 28 is abutted against the inclined surface 22B 
so that the whole plate spring 26 is displaced downward. On the other 
hand, the pressure spring 15 is in a condition such that its top end 15a 
invades far into the range of reciprocating movement of the pushbutton 12, 
with the projection 15b being held away from the switch mechanism 13. This 
condition is shown in FIG. 1 and FIG. 4(a). 
Then upon depression, the pushbutton 12 is displaced downward 14 as the 
inclined surface 22B of the operating cam 22 slides against the plate 
spring 26. In response, the click spring portion 28 of the plate spring 26 
is displaced toward the inner lateral wall 17B as illustrated in FIG. 
4(b). Until, the top bend 28a of the click spring portion 28 reaches the 
ridge 22A, the plate spring 26 is subject to a pressing force acting 
downward from the pushbutton 12 side. 
As the pushbutton 12 is further depressed and the ridge 22A trips over the 
top bend 28a of the click spring portion 28, the plate spring 26 is 
released as the downward pressing force is instantly relieved by the 
inclined surface 22C, whereby a feeling is obtained. At the same time, the 
plate spring 26 is abruptly pushed upward along the inclined surface 22C 
and the top bend 30 of the plate spring 26 hits the top inner wall 17C as 
illustrated in FIG. 4(c) to produce a click sound. At the same time, the 
tip 15a of the pressure spring 15 is pressed outwardly by the bottom 
angular portion of the pushbutton 12 so that the projection 15b actuates 
the switch mechanism 13. And as the pushbutton 12 is further depressed 
until its bottom hits the inner bottom wall 17D, this position corresponds 
to the maximum stroke of the pushbutton 12. This state is illustrated in 
FIG. 2 and FIG. 4(d). 
Then, as the depressing force on the pushbutton 12 is released, the 
pushbutton 12 is displaced upward by the resilient force of the release 
spring 16. Thus, as illustrated in FIG. 4(e), the ridge 22A of the 
operating cam 22 of the pushbutton 12 reaches the top bend 28a of the 
click spring portion 28. Beyond this top bend 28a, the plate spring 26 is 
released as the upward pressing force is instantly relieved by the 
inclined surface 22B as illustrated in FIG. 4(f) to produce a "snap" 
feeling. At the same time, the bottom bend 29 hits the inner bottom wall 
17D to produce a click sound. The pressing force exerted on the switch 
mechanism 13 by the pressure spring 15 is released at the same time. In 
this manner, the top bend 28a of the click spring portion 28 is positioned 
on the lower side of the operating cam 22, i.e. said inclined surface 22B, 
so as to return to the original condition illustrated in FIG. 1 and FIG. 
4(a). 
Thus, in this pushbutton switch, the vertical movement of the pushbutton 12 
is accompanied by the vertical movement of the plate spring 26. Moreover, 
the operating cam 22 is larger than the click spring portions 28 and 
movable. When the operating cam 22 trips over the top bends 28a of the 
click spring portions 28, a resilient force is applied to the plate spring 
26 by the operating cam 22 and this resilient force causes the plate 
spring 26 to abruptly move upward 14 or downward 14 to hit the top inner 
wall 17C or inner bottom wall 17D, producing both a click sound and a snap 
feeling. Furthermore, by varying the vertical dimension of the plate 
spring 26, that is the distance from the top bend 30 to the bottom bend 
29, the distance of movement to the inner top wall 17C or inner bottom 
wall 17D can be varied so that an optimal loudness of the click sound can 
be obtained. Therefore, the click sound level can be easily adjusted by 
changing the vertical length of the plate spring 26. 
Another embodiment of this invention is described below with reference to 
FIG. 5. It should be understood that like numerals are used to represent 
like parts or positions. Whereas the plate spring 26 in the preceding 
embodiment has click spring portions 28 bent back from the bottom of the 
upright portion 27, the plate spring 26 of this embodiment has click 
spring portions 28 formed by raising along incisions made from its top 
edge. As shown in FIG. 6, this plate spring 26 is loosely fitted between a 
pair of projections 20, 20 of the upper case 17 and the inner lateral wall 
17B in such a manner that it can move vertically as its lateral portions 
31 are guided between them. The top bend 28a of the click spring portion 
28 is disposed in abutment against the lateral side 12A of the pushbutton 
12. The rest of the operations of the switch is more or less the same as 
that to the first embodiment. 
It should be understood that while the switch mechanism 13 in each of the 
above embodiments is actuated through the pressure spring 15, the present 
invention is not limited to such a switch mechanism driven by a pressure 
spring but may use other switching systems. 
The above description and the accompanying drawings are merely illustrative 
of the application of the principles of the present invention and are not 
limiting. Numerous other arrangements which embody the principles of the 
invention and which fall within its spirit and scope may be readily 
devised by those skilled in the art. Accordingly, the invention is not 
limited by the foregoing description, but is only limited by the scope of 
the appended claims.