Patent ID: 7591326

Claim:
A power tool, comprising: a tool bit that performs a predetermined operation by rotating around its longitudinal axis, a driving mechanism that drives the tool bit, and a torque limiter engaged with the driving mechanism that transmits a torque of the driving mechanism to the tool bit when a torque acting upon the tool bit is lower than a predetermined set value, while interrupting the torque transmission of the driving mechanism when the torque acting upon the tool bit exceeds the set value, wherein the torque limiter comprises: a first rotating member rotatably disposed with respect to a predetermined axis crossing the longitudinal direction of the tool bit, a second rotating member disposed such that the second rotating member is rotated on the same axis as the first rotating member and a rotating peripheral surface of the second rotating member faces a rotating peripheral surface of the first rotating member, a ball held by the first rotating member such that the ball is prevented from relatively moving in a circumferential direction with respect to the first rotating member, the ball transmitting torque of the driving mechanism between the first and second rotating members by engaging with the second rotating member in the circumferential direction, a pressing member movably disposed in an axial direction of the first rotating member to contact the ball, and an elastic member that applies a biasing force in the axial direction of the first rotating member with respect to the ball via the pressing member, wherein the second rotating member comprises: a power transmitting region comprising a groove that is continuously formed in the circumferential direction from a deepest groove part to a shallowest groove part to allow torque transmission between the first and second rotating members by engagement with the ball in the circumferential direction, and a power transmission interrupted region comprising a groove that is continuously formed in the circumferential direction in a depth shallower than or equal to the shallowest groove part of the power transmitting region to interrupt the torque transmission between the first and second rotating members by release of the engagement with the ball in the circumferential direction, wherein, when the ball is in the power transmitting region, the pressing member contacts the first rotating member such that the biasing force of the elastic member is prevented from acting upon the ball, while, when the ball is moved from the power transmitting region to the power transmission interrupted region, the pressing member is pushed by the ball in the axial direction and applies the biasing force of the elastic member to the ball.