Abstract: A key input device in which an input key is oscillated with respect to an opposing surface facing a bottom portion thereof and in which depression of the opposing surface with the input key at a normal operating point situated above a contact portion of a board causes the input key to tilt in a normal oscillating direction to effect input at the contact portion. Either the bottom portion of the input key or the opposing surface is equipped with guide protrusions arranged symmetrically with respect to an imaginary line extending along the normal oscillating direction of the input key. Depression of the opposing surface with the input key at an erroneous operating point deviated from the normal operating point results in the guide protrusions guiding the input key to tilt in the normal oscillating direction while abutting either the bottom portion of the input key or the opposing surface.

Abstract: A key input device in which an input key is oscillated with respect to an opposing surface facing a bottom portion thereof and in which depression of the opposing surface with the input key at a normal operating point situated above a contact portion of a board causes the input key to tilt in a normal oscillating direction to effect input at the contact portion. Either the bottom portion of the input key or the opposing surface is equipped with guide protrusions arranged symmetrically with respect to an imaginary line extending along the normal oscillating direction of the input key. Depression of the opposing surface with the input key at an erroneous operating point deviated from the normal operating point results in the guide protrusions guiding the input key to tilt in the normal oscillating direction while abutting either the bottom portion of the input key or the opposing surface.

Abstract: To make spherical shape of the terminal end of extruding part of a push-button switch to press a curved contact portion composed of a metal belleville spring and a resin film dome. In addition, the gate injecting mouth 4 for thermoplastic material 3 is opened in the side surface of the extruding part 2 or in the side projection made in a mold to inject the resin material in order to make molding of spherical shape of the terminal end of extruding part 2 of a push-button switch possible. By this structure, the present invention can provide a sheet-like key top having improved clicking touch and preventing break of a contact portion by residual stress.

Abstract: A short-stroke dome-shaped disc film spring comprising a dome-shaped portion and a skirt figure portion, wherein the cross section of the skirt figure portion rises in a line, the rise angel is inclined inward between 40 degrees and 60 degrees, the height of the skirt figure portion is between 0.2 mm and 0.4 mm, and the dome-shaped portion and the skirt figure portion are formed from a resin film of thickness 75 to 200 .mu.m. The dome-shaped film spring has a short stroke at which a feeling of a click is obtained.