Abstract: An impact wrench includes a driving unit, a spindle configured to be rotated by the driving unit, an anvil arranged in front of the spindle in a direction of a rotational axis of the spindle, a primary hammer that is capable of rotating about the rotational axis of the spindle and moving in the direction of the rotational axis of the spindle, a secondary hammer having a cylindrical part in which the primary hammer is housed and that rotates synchronously with the primary hammer, the cylindrical part being configured to receive the spindle, and a rotary impact mechanism that impulsively engages the primary hammer with the anvil to rotate the anvil about the rotational axis of the spindle.

Abstract: An impact wrench is provided that can mitigate vibrations in the axial direction without reducing the rotary impact force of hammers. The hammers are composed of a primary hammer fitted to the outer circumference of a spindle and a cylindrical secondary hammer that is disposed so as to cover the primary hammer and that rotates integrally with the primary hammer. Furthermore, the secondary hammer is held by a center holding means in a state in which the rotational axis of the secondary hammer is coincident with the axis of the spindle in order to prevent run-out movement. With the use of the hammer configuration of the present invention, the mass of the primary hammer can be decreased compared to that of the secondary hammer, and therefore it is possible to mitigate vibrations in the axial direction while maintaining the rotary impact force.

Abstract: An impact wrench is provided that can mitigate vibrations in the axial direction without reducing the rotary impact force of hammers. The hammers are composed of a primary hammer fitted to the outer circumference of a spindle and a cylindrical secondary hammer that is disposed so as to cover the primary hammer and that rotates integrally with the primary hammer. Furthermore, the secondary hammer is held by a center holding means in a state in which the rotational axis of the secondary hammer is coincident with the axis of the spindle in order to prevent run-out movement. With the use of the hammer configuration of the present invention, the mass of the primary hammer can be decreased compared to that of the secondary hammer, and therefore it is possible to mitigate vibrations in the axial direction while maintaining the rotary impact force.

Abstract: A main spindle of an air saw is reciprocated by sliding a piston in a cylinder chamber with the pressure of air supplied to the cylinder chamber via an air supply path so as to alternately apply the air pressure to pressure-receiving surfaces of a back plate and a front plate, wherein a rear air-cushion chamber is formed in a portion for fixing a return spring for urging the back plate toward the center of a cylinder while a front air-cushion chamber is formed in a portion for fixing a return spring for urging the front plate toward the center of the cylinder, so that the front and rear balance is maintained.

Abstract: A wrench includes a main shaft having a working portion provided at the top thereof; a torsion member having an elastic restoring force against torsion about the axis of the main shaft; at least one operating handle disposed so as to intersect with the middle of the main shaft; and torque display means for displaying a torque produced in accordance with the degree of twist of the torsion member with respect to the reference point of the same. The main shaft is dividable into two divided bodies in the axial direction thereof, and the two divided bodies are connected to each other. The torsion member is interposed between the divided bodies, which are turnable relative to each other about the axis of the main shaft. With this wrench, a screw can be quickly sent to its seating position and is then fastened with up to a predetermined torque.

Abstract: A torque wrench is formed by a hollow handle, a sheath tube, a head, a slider, a torque transmitting mechanism, a torque adjusting mechanism, etc. The sheath tube covers the front half of the hollow handle with a predetermined gap between the inner and outer surfaces of the sheath tube and the hollow handle, respectively, and is connected to the front of the hollow handle and also to the head at the front thereof. The slider is moveably disposed around the hollow handle in the longitudinal direction of the hollow handle such that the front end surface of the slider opposes the rear end surface of the sheath tube. The torque transmitting mechanism is disposed between the opposing end surfaces of the slider and the sheath tube, and the torque adjusting mechanism is disposed in the rear of the slider and around the rear half of the hollow handle.

Abstract: A hand-held powered screw tightening tool has a detecting device to detect a rotation angle of a rotary member in a clockwise direction and a counterclockwise direction. In screw tightening, an angle obtained by subtracting a cumulative total of the rotation angle of the rotary member with rebound, if any, in a counterclockwise direction from a cumulative total of the rotation angle of the rotary member in the clockwise direction is detected and accumulated as a total rotation angle (P) and a rotation angle formed during the deceleration at the hammering is detected as &Dgr;H and accumulated, and a preset design angle Pd for hammering is accumulated. A wobbling angle is calculated from Equation: A wobbling angle=P−a cumulative total of Pd−a cumulative total of &Dgr;H (where Pd is a design value of the impact wrench, indicating an angle corresponding to 360°/m for the case of the m number of hammerings per rotation of the rotary member).