Key-board switch unit

摘要

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.