Smk Corporation

Kumio Ozeki

Fumio Watanabe

Haruo Yoshida

Yosuke Sakai

Osam Kamishima

A membrane switch is actuated by pressure transmitted from a movable key member through two coaxial springs connected end-to-end. A first of the two springs is held by the key member in a partially strained state requiring an initial force to strain it further. The second spring, smaller in diameter and stiffer than the first, has a free end at which force is applied to the membrane switch. As a top of the key member is pressed, the free end of the second spring moves toward, touches, then presses the membrane switch. Force builds rapidly with displacement in the small spring until it reaches the initial force under which the first spring is retained. This initial force is made roughly equal to the force required to actuate the membrane switch. After that point, the force-displacement characteristic is that of the two-spring combination, which is less stiff than the second spring alone. Thus, long key travel is permitted while the actuation force is reached early in the displacement of the key member. In one embodiment, a resilient boot, covering a key stem of the key switch, buckles when the key is pressed to provide a click-like feedback to an operator.

Key switch

A double-axis key switch has a key cap with a pair of key stems which slide into a housing to actuate a pair of switches. The key stems are slightly out of parallel so that the axes of the key stems meet in a direction of stroke relative to the key cap. However, the sleeves, into which the key stems insert, are parallel. When the key cap is pressed off-center, causing tilting of the key cap, one key stem advances ahead of the other. Because of the relative positions of the axes, binding forces increase in the leading key stem and decrease in the following stem. The asymmetry of the binding forces tends to correct the tilting of the key cap so that the key cap advances symmetrically and smoothly.

Double-axis key switch

In a keyboard switch that switches on and off by sliding a key stem, the key stem is slidably inserted in a key stem sleeve that is integral with the housing of the keyboard switch. The key stem comprises a sliding member integrally formed therewith and a keytop support whose shape is a wide flange formed integrally with and projecting outwardly from the outer periphery of the sliding member. An elastic hollow cylinder has one end hermetically joining the lower face of the keytop support and its other end hermetically joining the outer periphery of the key stem guide sleeve. With this structure, there can be no gap between the sliding member and the keytop support, so the interior of the keyboard switch is kept completely free from dust and moisture.

Growing community of inventors

Tokyo, Japan

Kumio Ozeki