초록 ▼

It is an object of the present invention to provide an effective technique to alleviate vibration in the electric hammer drill. According to the invention, representative electric hammer drill is provided with a body, a motor, a striker, a cylinder, first and second power transmitting mechanisms, a

It is an object of the present invention to provide an effective technique to alleviate vibration in the electric hammer drill. According to the invention, representative electric hammer drill is provided with a body, a motor, a striker, a cylinder, first and second power transmitting mechanisms, a power switching mechanism, a mode changing mechanism, and a coupling mechanism. The mode changing mechanism is disposed on the upper surface of the body and can change between a hammer-drill mode and a hammer mode. The coupling mechanism is disposed between the mode changing mechanism and the power switching mechanism. 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. Because the mode changing mechanism is disposed on the upper surface of the body and the coupling mechanism extends along the peripheral surface of the cylinder to move in the longitudinal direction of the cylinder, the center of gravity of the electric hammer drill is positioned nearer to the axis of the cylinder, compared with the known art in which the components for the switching the operation modes are centralized in one area. As a result, operating vibration of the electric hammer drill is effectively alleviated.

대표청구항 ▼

We claim: 1. 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 cyli

We claim: 1. 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. 2. The hammer drill as defined in claim 1, wherein the cylindrical element prevents free rotation of the tool bit by an engagement with a member that rotates together with the tool bit when the mode changing mechanism is switched to the hammer mode. 3. The hammer drill as defined in claim 1, wherein the cylindrical element is disposed coaxially with the cylinder and the relay members on the opposite sides of the cylinder are connected to the cylindrical element on a straight line that extends in the radial direction passing across the axis of the cylinder. 4. The hammer drill as defined in claim 1, wherein the body further includes a handgrip disposed on the opposite side of the tool bit, and wherein the mode changing mechanism is disposed on the upper surface of the body and forward of the handgrip. 5. The hammer drill as defined in claim 1, wherein the power switching mechanism is disposed on the side opposite to the mode changing mechanism with respect to the cylinder. 6. The hammer drill as defined in claim 1, wherein the power switching mechanism includes engaging clutches. 7. The hammer drill as defined in claim 1, wherein the axis of the motor is perpendicular or parallel to the axis of the cylinder. 8. The hammer drill as defined in claim 1, wherein the second power transmitting mechanism includes an intermediate shaft that transmits rotation of the motor to the tool holder, and wherein the power switching mechanism is disposed in the second power transmitting mechanism. 9. The hammer drill as defined in claim 8, wherein the driving gear is integrally formed on an end of the intermediate shaft. 10. An electric hammer drill comprising: a body, a motor that is 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 that is disposed on the upper surface of the body and is adapted to 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 that is 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 includes a cylindrical element that is disposed around the cylinder and that can move in the longitudinal direction of the cylinder and wherein the coupling mechanism transmits 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 that are disposed on the-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.