Pushbutton Switch

The invention relates to a pushbutton switch for use in a table electronic calculator, a terminal device, or the like and, more partucularly, to an attachment of the pushbutton and the lever of the pushbutton switch in which the lever is forced to fit into a recess formed in the pushbutton.

Conventionally, a synthetic-resin made lever has been formed to have its attachment portion forced to fit into the recess formed in a synthetic-resin made pushbutton so as to attach the lever to the pushbutton. In such attachment, however, the lever has a tendency to become loose and come out of the recess of the pushbutton as the lever is subject to creep and deforms with the passage of time.

Therefore, it is an object of the present invention to provide an improved attachment of the lever and the pushbutton of a pushbutton switch which is effective to prevent the lever from coming out of the recess of the pushbutton.

Another object of the present invention is to provide an improved attachment which is simple in construction and which is free from the above-mentioned and other disadvantages.

In accordance with the present invention, there is provided a pushbutton switch including a pushbutton formed with a recess, and a lever having an attachment portion forced to fit into the recess, the switch comprising the pushbutton formed of a synthetic resin, the lever formed of a synthetic resin relatively harder than the material of the pushbutton and relatively small in creep contraction rate, and projections attached or integrally formed on the attachment portion of the lever. When the attachment portion is forced to fit into the recess, the projections thrust into the recess wall so as to prevent the lever from coming out of the recess due to the deformation of the recess and the attachment portion with the passage of time.

The invention will be described in greater detail by reference to the following description taken in connection with the accompanying drawings, in which:

FIGS. 1a and 1b are perspective views of the pushbutton and the lever, respectively, in accordance with the present invention;

FIG. 2 is a sectional view taken along a diagonal line with the attachment portion of the lever shown in full engagement with the recess of the pushbutton;

FIG. 3 is a perspective view of the lever of an alternative embodiment of the present invention; and

FIG. 4 is a sectional view showing the conventional attachment of the lever and the pushbutton.

Referring to FIG. 4, there is illustrated a conventional attachment of a pushbutton 11 and a lever 13. The lever 13 is formed to have its attachment portion 14 forced into close engagement with a recess 12 formed in the pushbutton 11. This attachment has a disadvantage in that the lever 13 may become loose and come out of the recess 12 of the pushbutton 11 as the lever 13 is subject to creep and deforms with the passage of time.

FIGS. 1a, 1b and 2 show an improved attachment of a pushbutton 1 and a lever 3 which is capable of eliminating the above disadvantage found in the conventional one. The pushbutton 1 is formed of a synthetic resin such as ABS synthetic resin and is formed in its undersurface with a cross-shaped recess 2. The lever 3 is formed of a synthetic resin relatively harder than the material of the pushbutton 1 and small in creep contraction rate, such as Duracon, a trademark of the Polyplastics Company, Ltd. of Osaka, Japan. The lever 3 has an attachment portion 4a of cross-shape in section as shown in FIG. 1b, which is forced to fit into the recess 2 of the pushbutton 1. The attachment portion 4 has its corners 4a and 4b provided with diamond-shaped projections 5a and 5b each with its tip end pointed.

When the attachment portion 4 is forced to fit into the recess 2 of the pushbutton 1, it, particularly the projections 5a and 5b, strongly presses against the inner wall of the recess 2. With the passage of time, the recess becomes expanded in the direction of the recess being pressed, whereas the attachment portion 4 is contracted due to creep. As a result, the attachment thereof becomes loose and has its strength reduced. However, since the pushbutton 1 and the lever 3 are different in deformation rate and the expansion rate of the recess 2 is larger than the contraction rate of the attachment portion 4, the projections 5a and 5b remain thrusting into the edges 2a and 2b as shown in FIG. 2 so as to prevent the lever 3 from coming out of the recess 2. Thus, the lever 3 cannot be separated from the pushbutton 1 without a rather strong force.

FIG. 3 shows an alternative embodiment of the present invention in which tetrahedron-shaped projections 6a are provided on the corners 4a and 4b of the attachment portion 4 instead of the diamond-shaped projections 5a and 5b. The tetrahedron-shaped projections have respective ridgelines 7a thrusting into the edges 2a and 2b so as to prevent the lever 3 from comming out of the recess 2 of the pushbutton 1.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.