Key switch for a keyboard

DETAILED DESCRIPTION The present invention provides a key switch which eliminates the aforesaid drawbacks.
According to one aspect of the present invention, the key switch comprises a key base having a circular upright bearing defining a first axial hole and a second axial hole around the first axial hole, a key cap having a first downward tube inserted into the first axial hole of the base and a second downward tube inserted into the second axial hole of the key base, a membrane circuit mounted on the flat base of the key base around the upright bearing, and a rubber mounted on the membrane circuit around the upright bearing of the key base to support the key cap above the key base and having a plunger portion spaced around the upright bearing of the key base and forced by the key cap to trigger the membrane circuit when the key cap is depressed, causing it to produce an electric signal.
According to another aspect of the present invention, the first downward tube and second downward tube of the key cap are respectively disposed in contact with the periphery of the first axial hole and second axial hole of the key base, so that a friction force is produced between the first downward tube and second downward tube of the key cap and the periphery of the first axial hole and second axial hole of the key base to keep the key cap to be moved stably.