Screwdriver

In a screwdriver including a normally and reversely operable motor, a driving shaft member for transmitting power from the motor, a cylindrical member disposed on the driving shaft member, an output shaft member for retaining a screw-driving bit, the output shaft member being supported in an axially movable manner, a cylindrical member disposed on the output shaft member, pressing means for causing the output shaft member and the driving shaft member to be spaced apart from one another, a coiled clutch spring positioned in a coaxial direction of the driving shaft member and the output shaft member in a state of extending over the respective cylindrical members on the output shaft member and the driving shaft member, the clutch spring having one end secured to one of the output shaft member and the driving shaft member and having the other end held against the other of the output shaft member and the driving shaft member in a response to movement of the output shaft member, a one-way clutch disposed between the output shaft member and the driving shaft member, a ball retained in a through-hole in a maimer movable in a radial direction of the other of the output shaft member and the driving shaft member, the through-hole being defined in the other of the output shaft member and the driving shaft member, the ball being possible to project beyond the cylindrical member on the other of the output shaft member and the driving shaft member along an outer circumference of the cylindrical member, the ball further being possible to abut an end of the clutch spring, and means for allowing the ball to protrude beyond the cylindrical member of the other of the output shaft member and the driving shaft member along the outer circumference of the cylindrical member in response to axial movement of the output shaft member against the pressing means, in which a revolving force is transmitted from the driving shaft member to the output shaft member through the clutch spring during normal rotation of the motor, thereby tightening a screw, but the revolving force is transmitted from the driving shaft member to the output shaft member through the one-way clutch during reverse rotation of the motor, thereby loosening the screw, the improvement comprising:

• disengagement means for releasing engagement between the clutch spring and the ball during the reverse rotation of the motor, wherein
• the disengagement means is a through-hole shaped to permit the ball to be moved away from an immovable shaft member when the ball and the clutch spring are driven against one another during reverse rotation of the motor, part of the clutch spring being secured to the immovable shaft member, and
• the through-hole includes a relief aperture that is slanted in an axial direction of the output shaft member.

In a screwdriver including a normally and reversely operable motor, a driving shaft member for transmitting power from the motor, a cylindrical member disposed on the driving shaft member, an output shaft member for retaining a screw-driving bit, the output shaft member being supported in an axially movable manner, a cylindrical member disposed on the output shaft member, pressing means for causing the output shaft member and the driving shaft member to be spaced apart from one another, a coiled clutch spring positioned in a coaxial direction of the driving shaft member and the output shaft member in a state of extending over the respective cylindrical members on the output shaft member and the driving shaft member, the clutch spring having one end secured to one of the output shaft member and the driving shaft member and having the other end held against the other of the output shaft member and the driving shaft member in a response to movement of the output shaft member, a one-way clutch disposed between the output shaft member and the driving shaft member, a ball retained in a through-hole in a manner movable in a radial direction of the other of the output shaft member and the driving shaft member, the through-hole being defined in the other of the output shaft member and the driving shaft member, the ball being possible to project beyond the cylindrical member on the other of the output shaft member and the driving shaft member along an outer circumference of the cylindrical member, the ball further being possible to abut an end of the clutch spring, and means for allowing the ball to protrude beyond the cylindrical member of the other of the output shaft member and the driving shaft member along the outer circumference of the cylindrical member in response to axial movement of the output shaft member against the pressing means, in which a revolving force is transmitted from the driving shaft member to the output shaft member through the clutch spring during normal rotation of the motor, thereby tightening a screw, but the revolving force is transmitted from the driving shaft member to the output shaft member through the one-way clutch during reverse rotation of the motor, thereby loosening the screw, the improvement comprising:

• disengagement means for releasing engagement between the clutch spring and the ball during the reverse rotation of the motor, wherein
• the disengagement means includes a slanted surface and a through-hole, the slanted surface being formed on the clutch spring at the end of the clutch spring where the ball and the clutch spring are forced against one another when the motor is reversely rotated, the through-hole being shaped to permit the ball to be moved away from an immovable shaft member when the ball and the clutch spring are driven against one another during the reverse rotation of the motor, part of the clutch spring being secured to the immovable shaft member.