Patent ID: 8191697

Claim:
A clutch mechanism for transmitting a driving force of a motor to an end-bit mounting portion which includes a socket and an engagement segment, comprising: a first clutch portion having driving members and driven members, the driving members being rotatable with the motor and the driven members being rotatable with the end-bit mounting portion, a second spring clutch including; a first part having a sleeve section fixed to a housing, a first spring mount section and an abutment section having a first tapered surface, a second part having a second spring mount section and an engaged section, the second spring mount section having a second tapered surface, the first part and the second part being aligned linearly and coaxially in a state that the first tapered surface is in contact with the second tapered surface, and a spring disposed between the first spring mount section and the second spring mount section for allowing the second part to rotate only in one direction with respect to the first part, wherein the driving force can be transmitted to the socket by way of the first clutch portion when the engagement segment is disengaged from the engaged section and co-rotation of the socket and the first clutch portion in a forward direction can be restrained when the engagement segment is engaged with the engaged section.