초록 ▼

An air chamber is formed in a cylinder between a piston and a striking member. The cylinder is formed with at least one through-hole for providing fluid communication between the air chamber and an outside of the cylinder. A switching mechanism switches operation modes between a first operation mode

An air chamber is formed in a cylinder between a piston and a striking member. The cylinder is formed with at least one through-hole for providing fluid communication between the air chamber and an outside of the cylinder. A switching mechanism switches operation modes between a first operation mode and a second operation mode. In the first operation mode, the at least one through-hole is closed when the working tool is moved toward the another end and, when the at least one through-hole is closed, reciprocating motion of the piston generates pressure changes in the air chamber, allowing the striking member to transmit a striking force to a working tool. In the second operation mode, the at least one through-hole is constantly open, prohibiting the striking member from transmitting a striking force to the working tool.

대표청구항 ▼

What is claimed is: 1. 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

What is claimed is: 1. 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. 2. The hammer drill according to claim 1, wherein the switching mechanism switches the operation modes by restricting an amount of movement of the working tool toward the second end. 3. The hammer drill according to claim 1, wherein the cylinder is movable in the axial direction when the working tool is moved toward the second end; and wherein the switching mechanism switches the operation modes by restricting an amount of movement of the cylinder. 4. The hammer drill according to claim 1, wherein the switching mechanism comprises a cam rotatable in a plurality of rotational positions; and wherein the switching mechanism switches the operation modes according to rotational position of the cam. 5. The hammer drill according to claim 1, wherein the switching mechanism is capable of switching the operation mode to a third operation mode in which transmission of the rotational force to the cylinder is turned off. 6. The hammer drill according to claim 1, wherein the switching mechanism is capable of switching the operation modes among at least a rotation and strike mode, a rotation only mode, and a strike only mode. 7. The hammer drill according to claim 1, wherein the cylinder has an outer peripheral surface; wherein the gear is rotatably supported around the outer peripheral surface of the cylinder; wherein the rotational force transmitting mechanism further comprises a coupling member disposed around the outer peripheral surface of the cylinder, the coupling member being fitted with the outer peripheral surface of the cylinder by spline fitting; allowing the coupling member to be slidable in the axial direction for engaging with and disengaging from the gear; and wherein the switching mechanism comprises a switching member that can be operated at least among a first switch position in which the coupling member is engaged with the gear and a second switch position in which the coupling member is disengaged from the gear. 8. The hammer drill according to claim 7, wherein the switching member comprises an eccentric pin that moves the coupling member when the switching member is operated, allowing the coupling member to be engaged with the gear in the first switch position, and allowing the coupling member to be disengaged from the gear in the second switch position. 9. 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; 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; and wherein the switching mechanism switches the operation modes by restricting an amount of movement of the working tool toward the second end. 10. 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; 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 cylinder is movable in the axial direction when the working tool is moved toward the second end; and wherein the switching mechanism switches the operation modes by restricting an amount of movement of the cylinder. 11. 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 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; 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 cylinder is movable in the axial direction when the working tool is moved toward the second end; and wherein the switching mechanism switches the operation modes by restricting an amount of movement of the cylinder. 12. 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; and wherein the switching mechanism is capable of switching the operation mode to a third operation mode in which transmission of the rotational force to the cylinder is turned off. 13. The hammer drill according to claim 12, wherein the switching mechanism switches the operation modes by restricting an amount of movement of the working tool toward the second end. 14. The hammer drill according to claim 12, wherein the cylinder is movable in the axial direction when the working tool is moved toward the second end; and wherein the switching mechanism switches the operation modes by restricting an amount of movement of the cylinder. 15. The hammer drill according to claim 12, wherein the switching mechanism comprises a cam rotatable in a plurality of rotational positions; and wherein the switching mechanism switches the operation modes according to rotational position of the cam. 16. The hammer drill according to claim 12, wherein the switching mechanism is capable of switching the operation modes among at least a rotation and strike mode, a rotation only mode, and a strike only mode. 17. The hammer drill according to claim 12, wherein the cylinder has an outer peripheral surface; wherein the gear is rotatably supported around the outer peripheral surface of the cylinder; wherein the rotational force transmitting mechanism further comprises a coupling member disposed around the outer peripheral surface of the cylinder, the coupling member being fitted with the outer peripheral surface of the cylinder by spline fitting, allowing the coupling member to be slidable in the axial direction for engaging with and disengaging from the gear; and wherein the switching mechanism comprises a switching member that can be operated at least among a first switch position in which the coupling member is engaged with the gear and a second switch position in which the coupling member is disengaged from the gear. 18. The hammer drill according to claim 17, wherein the switching member comprises an eccentric pin that moves the coupling member when the switching member is operated, allowing the coupling member to be engaged with the gear in the first switch position, and allowing the coupling member to be disengaged from the gear in the second switch position. 19. 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 cylinder has an outer peripheral surface; wherein the gear is rotatably supported around the outer peripheral surface of the cylinder; wherein the rotational force transmitting mechanism further comprises a coupling member disposed around the outer peripheral surface of the cylinder, the coupling member being fitted with the outer peripheral surface of the cylinder by spline fitting, allowing the coupling member to be slidable in the axial direction for engaging with and disengaging from the gear; and wherein the switching mechanism comprises a switching member that can be operated at least among a first switch position in which the coupling member is engaged with the gear and a second switch position in which the coupling member is disengaged from the gear. 20. The hammer drill according to claim 19, wherein the switching member comprises an eccentric pin that moves the coupling member when the switching member is operated, allowing the coupling member to be engaged with the gear in the first switch position, and allowing the coupling member to be disengaged from the gear in the second switch position.