Patent ID: 11858094
Assignee: MAKITA CORPORATION
Field: Machine tools (Mechanical engineering)
Classification: CPC B | IPC B

Claim 4:
5. An impact tool, comprising:
a motor;
a carrier including a reduction assembly and configured to be rotated by the motor;
a shaft configured to receive and be rotated by rotation of the carrier;
a hammer held by the shaft;
an anvil configured to be struck by the hammer in a rotation direction;
a ball between the shaft and the hammer;
a coil spring externally mounted on the shaft; and
a cam assembly between the carrier and the shaft, wherein
the shaft and the carrier are configured such that (i) the shaft rotates at a same speed as the carrier when a load on the carrier is at or below a threshold load and (ii) the shaft rotates at a different speed than the carrier when the load on the carrier is above the threshold load,
the shaft extends frontward and has a cam groove on an outer circumferential surface,
the hammer is held with the ball,
the hammer is movable back and forth between a forward position at which the hammer is engaged with the anvil in the rotation direction and a rearward position at which the hammer is disengaged from the anvil in the rotation direction by the ball rolling in the cam groove,
the hammer is urged to the forward position by the coil spring,
the hammer, the ball and the shaft are configured such that, when the load on the carrier is above the threshold load, the ball is at a rearmost end of the cam groove,
the cam assembly (i) is configured to transmit the rotation of the carrier to the shaft and to rotate the carrier and the shaft relative to each other when the load on the carrier is above the threshold load and (ii) includes
a cam projection protruding frontward from a center of the carrier,
a cam coupled to the shaft in a manner rotatable together with the shaft and movable back and forth relative to the shaft, the cam being engageable with the cam projection at the rearward position to transmit the rotation of the carrier to the shaft and being configured to rotate the carrier and the shaft relative to each other at the forward position, and
an urging member to urge the cam to the rearward position.