Pneumatically operated screw driver having drive bit attaching and detaching mechanism

A pneumatically operated screw driver that operates with a compressed air to drive screws into a workpiece, the screw driver comprising:

• a casing;
• an accumulator chamber portion in the casing for defining an accumulator chamber that accumulates the compressed air;
• a pneumatic motor rotatable by the compressed air from the accumulator chamber in one direction only;
• a rotation transmission portion including a rotary member that transmits rotation of the pneumatic motor;
• a rotator rotatable only in a right-hand direction by the rotation transmitted by the rotation transmission portion, the rotator comprising:
• a rotation slide member supported in the rotary member so as to rotate together with the rotation of the rotary member and so as to be movable in an axial direction of the rotary member;
• and
• a piston connected to the rotation slide member and rotatable together with the rotation of the rotary slide member and movable in the axial direction;
• a drive bit connecting portion formed with one of a right-handed female threaded hole and a righted-handed male threaded screw;
• a main valve for controlling supply of the compressed air in the accumulator chamber to the pneumatic motor and the rotary member;
• an operation valve for controlling the main valve and accessible from an external position;
• and
• a drive bit formed at one end with one of the right-handed male thread screw and a female threaded hole and at the other end with an engagement tip engagable with the screws that are to be screwed into the workpiece, the drive bit being threadingly engaged with the drive bit connecting portion through threading engagement of the right-handed female threaded hole and the righted-handed male threaded screw,
• the rotation of one of the pneumatic motor, the rotary member and the rotator being regulatable during non-application of the compressed air into the pneumatic motor, while the engagement tip at the other end of the drive bit being engaged with a first tool.