Shin-Etsu Polymer Co., Ltd.

Takekuni Okamoto

Ryoichi Sado

Kazutoki Tahara

Shigeru Matumoto

Yoshitusgu Morikawa

The invention provides a push button switch covering member integrally made of a rubbery elastomeric material having an improved structure with which a much larger key stroke is obtained before a snapping action takes place in the covering member when the member is pushed at the center portion leading to the contact of the contact points than in the conventional ones. The covering member is constructed of (a) a central pushing part, (b) a first annular portion which may be in a form of a truncated cone or a cup laid upside down and is connected to the central pushing part at the upper end, (c) a second annular portion encircling and connected to the first annular portion and (d) a base flat connected to the second annular portion, at which the covering member is mounted on the base board of the switch, the relationship between the strengths of the first and the second annular portions being such that the first annular portion does not undergo a buckling deformation before the second annular portion is substantially deformed or bent around the connecting line between the second annular portion and the base flat.

Rubber-made covering member for push button switches

The invention provides a key-board switch unit used, for example, in pocketable electronic calculators comprising a base plate having at least one pair of switch electrodes and a covering pad made of an insulating rubber and provided with at least one contact member made of an electroconductive rubber and bonded on the lower surface thereof to face the electrodes coming into contact therewith when the pad is depressed. The contact member is embedded in the covering pad in such a manner that the surface of it is coplanar with the surface of the covering pad at least along the peripheries in conjunction with the covering pad and the contact member is sufficiently small so as to be confined within the area of the covering pad facing the void space formed between the base plate and the covering pad at the portion of the electrodes. The hardness relationship between the rubbery materials of the covering pad and the contact member is also of essential importance for reliable switching and durability of the switch unit.

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Tokyo, Japan

Takekuni Okamoto