Patent ID: 7306048

Claim:
A hammer drill comprising: a housing; a motor disposed in the housing and generating a rotational force; a working tool; a striking force transmitting mechanism comprising: a cylinder rotatably supported in the housing, the cylinder extending in an axial direction and having a first end and a second end, the working tool being engaged with the first end so as to be rotatable together with the cylinder, the working tool being movable in the axial direction; a piston disposed adjacent to the second end in the cylinder and movable in a reciprocating motion in the axial direction; a motion converting mechanism that converts the rotational force of the motor into the reciprocating motion of the piston; and a striking member disposed between the working tool and the piston in the cylinder and slidable in the axial direction, an air chamber being formed in the cylinder between the piston and the striking member, the cylinder being formed with at least one through-hole for providing fluid communication between the air chamber and an outside of the cylinder; a rotational force transmitting mechanism comprising a gear that transmits the rotational force of the motor to the cylinder, thereby rotating the cylinder together with the working tool; and a switching mechanism that switches operation modes between: a first operation mode in which the at least one through-hole is closed when the working tool is moved toward the second end and, when the at least one through-hole is closed, the reciprocating motion of the piston generates pressure changes in the air chamber, allowing the striking member to transmit a striking force to the working tool; and a second operation mode in which the at least one through-hole is constantly open, prohibiting the striking member from transmitting a striking force to the working tool; wherein the switching mechanism comprises a sleeve disposed around the cylinder, the sleeve being slidingly movable in the axial direction for closing the at least one through-hole when the working tool is moved toward the second end in the first operation mode; and wherein the switching mechanism switches the operation modes by restricting an amount of movement of the sleeve.