Patent ID: 7707903

Claim:
An actuator comprising a motor; an input rotation member driven by the motor; an input contacting portion formed on the input rotation member; a bush rotatably disposed relative to the input rotation member and having an engaging portion; the bush possessing an outwardly extending first contacting portion; a spiral spring including an outer circumferential hook portion in contact with a first side surface of the input contacting portion of the input rotation member, and an inner circumferential hook portion engaging the engaging portion of the bush, the spiral spring storing a rotational force of the input rotation member as potential energy via the input contacting portion, the input contacting portion possessing a second side surface on a side of the input contacting portion opposite the first side surface; an output member rotatably disposed relative to the input rotation member; an output contacting portion formed on the output member and in contact with the outer circumferential hook portion of the spiral spring when the input contacting member and the output contacting member are in a neutral state; the output contacting portion transmitting the potential energy stored in the spiral spring to the output member; the bush possessing an outwardly extending second contacting portion which is spaced from the outwardly extending first contacting portion so that a space exists between the outwardly extending first contacting portion and the outwardly extending second contacting portion, the input contacting portion and the output contacting portion being positioned in the space, the second side surface of the input contacting portion being spaced from the outwardly extending second contacting portion by a predetermined rotational angle of less than 180° measured in a rotational direction; the input contacting member being rotated in said rotational direction relative to the output member by operation of the motor so that when a difference in relative rotation between the input rotation member and the output member reaches the predetermined rotational angle, the second side surface of the input contacting portion contacts the outwardly extending second contacting portion so continued rotation of the input rotation member in said rotational direction is directly transmitted to the output member.