Patent ID: 7383893

Claim:
An electric hammer drill comprising: a body, a motor housed within the body, a tool holder that holds a tool bit disposed in a tip end region of the body, a striker that linearly moves in the axial direction of the tool bit and causes the tool bit to perform a striking movement, a cylinder in which the striker is slidably disposed, a first power transmitting mechanism that causes the striker to move linearly by a rotating output of the motor, a second power transmitting mechanism that includes a region of transmitting rotation by engagement between a driving gear and a driven gear and causes the tool bit to rotate around its axis by a rotating output of the motor, a power switching mechanism that can switch between a state of transmitting rotation of the motor to the hammer bit and a state of preventing the transmission of rotation while keeping the driving gear and the driven gear of the second power transmitting mechanism in engagement with each other, a mode changing mechanism disposed on the upper surface of the body and can change between a hammer-drill mode in which the tool bit is caused to perform a combined movement of striking and rotating and a hammer mode in which the tool bit is caused to perform only a striking movement, and a coupling mechanism disposed between the mode changing mechanism and the power switching mechanism and is adapted to cause the power switching mechanism to switch to the state of power transmission when the mode changing mechanism is switched to the hammer drill mode, while causing the power switching mechanism to switch to the state of preventing the power transmission when the mode changing mechanism is switched to the hammer mode, wherein the coupling mechanism extends along the peripheral surface of the cylinder and transmits the mode changing movement of the mode changing mechanism to the power switching mechanism by moving in the longitudinal direction of the cylinder, and wherein the coupling mechanism includes a cylindrical element that is disposed around the cylinder and that can move in the longitudinal direction of the cylinder, the coupling mechanism being adapted to transmit the mode changing movement of the mode changing mechanism in the longitudinal direction of the cylinder to the cylindrical element via a plurality of relay members disposed on opposite sides of the cylinder, and wherein the cylindrical element includes a cam that causes the power switching mechanism to switch to the state of power transmission or to the state of preventing the power transmission, by components of movement in a direction perpendicular to the longitudinal direction of the cylinder, when the cam moves together with the cylindrical element in the longitudinal direction of the cylinder.