Abstract: It is an object of the invention to provide a rational forced vibration of a dynamic vibration reducer in an impact tool that linearly drives a tool bit in an axial direction of the tool bit via a swinging member. An impact tool includes a motor 111, a swinging member 129 that swings in the axial direction of a tool bit 119 by rotation of the motor 111, a driving element 141 that is caused to reciprocate by swinging movement of the swinging member 129 and a first air chamber 143a in which pressure is fluctuated by reciprocating movement of the driving element 141, and the tool bit 119 is driven by pressure fluctuations of the first air chamber 143a. The impact tool further includes a second air chamber 163 in which pressure is fluctuated by swinging movement of the swinging member 129, and a dynamic vibration reducer 151 having a weight 155 and an elastic element 157 which exerts a biasing force on the weight 155.

Abstract: A power tool capable of performing vibration damping action in working operation, without an increase in size. The working tool includes a motor, a housing in which an internal mechanism driven by the motor is stored, a tool bit disposed on one end of the housing, a hand grip continuously connected to the other end of the housing, and a dynamic damper. The dynamic damper is disposed by utilizing a space between the housing and the internal mechanism so that the damping direction of the dynamic damper faces the longitudinal direction of the tool bit.

Abstract: It is an object of the invention to provide a power tool with a rational placement of a dynamic vibration reducer within a tool body. A representative hammer drill embodied as a power tool according to this invention has a dynamic vibration reducer 151 which is placed within an internal space 110 located to a motion converting section 113 side of a driving motor 111 within a body 103. An inner edge of the internal space is defined by an outer edge of the motion converting section 113, and an outer edge of the internal space is defined by an outer periphery of the driving motor 111.

Abstract: A power tool capable of performing vibration damping action in working operation, without an increase in size. The working tool includes a motor, a housing in which an internal mechanism driven by the motor is stored, a tool bit disposed on one end of the housing, a hand grip continuously connected to the other end of the housing, and a dynamic damper. The dynamic damper is disposed by utilizing a space between the housing and the internal mechanism so that the damping direction of the dynamic damper faces the longitudinal direction of the tool bit.

Abstract: An object of the invention is to provide an improved technique for lessening an impact force caused by rebound of a tool bit after its striking movement in an impact power tool. The representative impact power tool comprises a tool body, a hammer actuating member, a tool holder, a driving mechanism, a weight placed in contact with the hammer actuating member to move rearward by a reaction force transmitted from the hammer actuating member when the hammer actuating member performs a hammering operation on the workpiece and an elastic element elastically deformed when the weight moves rearward in the tool body to push the elastic element such that the elastic element absorbs the reaction force transmitted to the weight. The weight is defined one or both of the cylinder and the tool holder.

Abstract: An electric hammer comprising a hammer bit (313) performing hammering work on a work, a drive motor, a hammering piece (334) driven by the drive motor to apply a hammering force to the hammer bit, and a mechanism (371) for damping vibration generated during hammering. The damping performance of the electric hammer is enhanced by causing the driving amount applied to the damping mechanism (371) to vary between a first mode where the damping mechanism (371) generates vibration of the hammer bit (313) subjected to an external force from the work during the load driving time and thereby optimizes the damping and a second mode where the damping mechanism (371) generates vibration corresponding to the vibration of the hammer bit (313) not subjected to an external force from the work during the no-land driving time and optimizes damping.

Abstract: It is an object of the invention to provide a technique that contributes to improvement of the vibration reducing performance of a dynamic vibration reducer in a power tool while realizing reduction in size of the dynamic vibration reducer. A representative power tool which linearly drives a tool bit to perform a predetermined operation on a workpiece includes a tool body and a dynamic vibration reducer. The dynamic vibration reducer has a weight and an elastic element. The weight has an internal space that extends in the axial direction of the tool bit from at least one end of the weight in said axial direction. One end of the elastic element is inserted and received in the internal space, while the other end of the elastic element is placed on the tool body directly or via the body side member.

Abstract: It is an object of the invention to provide a technique for a reduction of an impact force cased by rebound of a tool bit after its striking movement in an impact power tool. The representative impact power tool includes a tool body, a hammer actuating member, a striker, a weight and an elastic element. A reaction force is transmitted from the hammer actuating member to the weight and the elastic element is elastically deformed when the weight moves ward by the reaction to absorb the reaction force. The invention is characterized in that the mass of the weight is set to about 40% or more of the mass of the stiker.

Abstract: It is an object of the present invention to provide an improved technique for preventing leakage of lubricant from an accommodating space that houses a driving mechanism, while regulating the internal pressure of the accommodating space in a power tool. A representative power tool includes a power tool body, a tool bit, a driving mechanism, a lubricant, an accommodating space, a passage and a lubricant leakage preventing region. The accommodating space is disposed in the body to house the driving mechanism and is hermetically sealed. The passage has an accommodating space side opening and an outside opening. The passage extends, starting from the accommodating space side opening, in a direction away from the outside opening. Then, the passage turns around and extends toward the outside opening. Further, the lubricant leakage preventing region is provided with the passage to prevent the lubricant from leaking from the inside to the outside of the accommodating space.

Abstract: It is an object of the invention to provide an improved technique for lessening an impact force caused by rebound of a tool bit after the striking movement of the tool bit. Representative impact power tool (101) includes a tool body (103), a hammer actuating member (119, 145), a driving mechanism (113, 115), a weight (163) and an elastic element (165). A reaction force that the hammer actuating member receives from the workpiece when performing a hammering operation is transmitted from the hammer actuating member to the weight (163) and then, the weight (163) is caused to move rearward to push the elastic element (165). As a result, the reaction force can be absorbed by the elastic element (165). The elastic force of the elastic element (165) is prevented from acting upon the weight (163) forward beyond the reaction force transmitting position.

Abstract: It is an object of the present invention to provide a power tool having a further improved vibration reducing performance. The representative power tool may comprise a tool bit, an actuating mechanism, a dynamic vibration reducer. The actuating mechanism drives the tool bit linearly by means of pressure fluctuations so as to cause the tool bit to perform a predetermined operation. The dynamic vibration reducer has a weight that reciprocates under a biasing force of an elastic element to reduce vibration of the actuating mechanism. The weight may be driven by means of pressure fluctuations caused in the actuating mechanism. According to the invention, the weight of the dynamic vibration reducer can be actively driven by pressure fluctuations in the actuating mechanism for driving the tool bit. Therefore, regardless of the magnitude of vibration acting on the power tool, the dynamic vibration reducer can be forcedly and steadily operated.

Abstract: An object of the invention is to provide an improved technique for lessening an imp force caused by rebound of a tool bit after its striking movement in an impact power tool. representative impact power tool comprises a tool body, a hammer actuating member, a holder, a driving mechanism, a weight placed in contact with the hammer actuating member move rearward by a reaction force transmitted from the hammer actuating member when hammer actuating member performs a hammering operation on the workpiece and an ela element elastically deformed when the weight moves rearward in the tool body to push the ela element such that the elastic element absorbs the reaction force transmitted to the weight. weight is defined one or both of the cylinder and the tool holder.

Abstract: It is an object of the invention to provide an improved technique for lessening an impact force caused by rebound of a tool bit after the striking movement of the tool bit. Representative impact power tool (101) includes a tool body (103), a hammer actuating member (119, 145), a driving mechanism (113, 115), a weight (163) and an elastic element (165). A reaction force that the hammer actuating member receives from the workpiece when performing a hammering operation is transmitted from the hammer actuating member to the weight (163) and then, the weight (163) is caused to move rearward to push the elastic element (165). As a result, the reaction force can be absorbed by the elastic element (165). The elastic force of the elastic element (165) is prevented from acting upon the weight (163) forward beyond the reaction force transmitting position.

Abstract: It is an object of the present invention to provide an improved technique for preventing leakage of lubricant from an accommodating space that houses a driving mechanism, while regulating the internal pressure of the accommodating space in a power tool. A representative power tool includes a power tool body, a tool bit, a driving mechanism, a lubricant, an accommodating space, a passage and a lubricant leakage preventing region. The accommodating space is disposed in the body to house the driving mechanism and is hermetically sealed. The passage has an accommodating space side opening and an outside opening. The passage extends, starting from the accommodating space side opening, in a direction away from the outside opening. Then, the passage turns around and extends toward the outside opening. Further, the lubricant leakage preventing region is provided with the passage to prevent the lubricant from leaking from the inside to the outside of the accommodating space.

Abstract: It is an object of the present invention to provide a power tool having a further improved vibration reducing performance. The representative power tool may comprise a tool bit, an actuating mechanism, a dynamic vibration reducer. The actuating mechanism drives the tool bit linearly by means of pressure fluctuations so as to cause the tool bit to perform a predetermined operation. The dynamic vibration reducer has a weight that reciprocates under a biasing force of an elastic element to reduce vibration of the actuating mechanism. The weight may be driven by means of pressure fluctuations caused in the actuating mechanism. According to the invention, the weight of the dynamic vibration reducer can be actively driven by pressure fluctuations in the actuating mechanism for driving the tool bit. Therefore, regardless of the magnitude of vibration acting on the power tool, the dynamic vibration reducer can be forcedly and steadily operated.