Key switch device

An apparatus, comprising:

• a housing having a keyboard disposed therein;
• said keyboard comprising a plurality of key switch devices;
• at least one of the plurality of key switch devices comprising:
• a base plate;
• a membrane sheet laminated on the base plate, wherein the membrane sheet comprises a first lower sheet layer, a second middle sheet layer, and a third upper sheet layer;
• a key top disposed above the membrane sheet;
• an elastic dome that is disposed between the membrane sheet and the key top and presses the sheet in response to the key top being pressed down;
• a guide mechanism that is foldably mounted between the base plate and the key top and supports the key top so as to be movable up and down;
• the guide mechanism comprising an inner frame and outer frame, wherein the inner frame and outer frame are mounted in a diagonally crossing manner;
• projections provided on a bottom surface of the outer frame of the guide mechanism that face the membrane sheet and that approach and impact the membrane sheet in a case where a portion distant from the center of the key top is pressed down, wherein the projections comprise at least two projections being located on a front side of the at least one of a plurality of key switch devices, wherein the projections are a semi-spherical shape;
• and
• receiving portions in the base plate which face the projections and receive the projections in a case where the portion distant from the center of the key top is pressed down and prevent the projections from touching the base plate, wherein the receiving portions are located on locking pieces that support the inner frame of the guide mechanism;
• wherein the projections and receiving portions prevent other portions of the guide mechanism from impacting the membrane sheet in a case where the portion distant from the center of the key top is pressed down.