Patent ID: 8541707

Claim:
A keypad comprising: a push-button switch; a key for operating the push-button switch along a translational axis; and a plunger interposed between the key and the push-button switch, wherein a stiffness of the plunger along the translational axis increases with a travel of the key along the translational axis before the push-button switch is actuated, the plunger being in contact with the switch, wherein the plunger comprises a recess, a portion of the plunger comprising the recess defining an upper portion of the plunger which has a first stiffness, and a remaining portion of the plunger defining a lower portion of the plunger which has a second stiffness, the second stiffness being greater than the first stiffness, wherein the lower portion of the plunger is interposed between the upper portion of the plunger and the push-button switch, wherein at the beginning of the travel of the key toward the push-button switch, the plunger is essentially deformed at the upper portion of the plunger, the upper portion of the plunger being fitted onto a lug of the key, the lug being distant from a bottom of the recess along the translational axis at the beginning of the travel of the key toward the push-button switch, the bottom of the recess separating the upper portion of the plunger and the lower portion of the plunger, the recess being opened toward the key and closed toward the push-button switch by the bottom of the recess, and wherein beyond a point of travel for which the lug comes into contact with the bottom of the recess, the plunger is essentially deformed at the lower portion of the plunger, the stiffness of the plunger therefore increasing continuously in line with the first stiffness and then the second stiffness before the switch is actuated.