Bit retention and release mechanism

A mechanism for selectively releasing or retaining, in a rotary tool, a bit with a shaft having a groove on the shaft, comprising, in combination:

• a tool housing having an axis and an interior bore aligned with the axis;
• a spindle mateable with a bit and aligned with the axis, the spindle being rotatably mounted within the tool housing bore and adapted to rotate the bit when the bit is inserted into the housing bore;
• a tubular release sleeve mounted within the tool housing bore and slidable between a retention position and a release position, said sleeve having an outside surface;
• a generally annular, removable bushing having an interior and an exterior surface, said bushing positioned within the bore between the sleeve and the housing with at least a part of the exterior, circumferential surface thereof contacting the inside surface of the bore, and at least a part of the interior circumferential surface slidably contacting the outside of said sleeve, said bushing being adapted to prevent complete removal of the sleeve from the housing bore without removing the bushing;
• a retention key mounted within the spindle and adpated to cooperate with the release sleeve to extend into the groove of the bit and retain the bit in the spindle when the sleeve is in the retention position, and move out of the groove in the bit, allowing the bit's release from the spindle, when the sleeve is in the release position;
• means for biasing the release sleeve in the retention position said means for biasing positioned on the outside surface of the release sleeve intermediate the bushing and sleeve;
• and
• a removable retention pin mounted on the tool housing and adapted to project through housing to removably retain the bushing within the housing, whereby the bushing removably retains the sleeve and may limit, at least in part, the travel of the sleeve in the bore.