Patent ID: 7359506

Claim:
An opening and closing device for use in a telephone handset comprising: a stator having a stator cam; and a rotor having a rotor cam urged to the stator cam by a spring, and rotatable with respect to the stator; wherein, the stator cam includes: a flat stator portion and a projecting stator portion, the projecting stator portion including a first tilting portion and a second tilting portion extending from the flat stator portion to the first tilting portion, and a first inclined plane formed on a side wall of at least one of the first tilting portion and the flat stator portion; and wherein, the rotor cam includes: a projecting rotor portion; and a second inclined plane formed on a side wall of the projecting rotor portion; and wherein, friction between the stator cam and the rotor cam is greater (a) when the first inclined plane and the second inclined plane are in contact with each other than (b) when the first inclined plane and the second inclined plane are not in contact with each other.