Patent ID: 8322459

Claim:
A pneumatic power tool comprising: a housing; a pneumatic motor mounted in said housing; an air control unit coupled to said pneumatic motor and displaceable from a shut-off state to an entry state where a pressured air is introduced in said pneumatic motor; a drive coupler drivenly coupled to said pneumatic motor to rotate about an axis, and axially movable relative to said housing between depressed and non-working positions that correspond to the entry and shut-off states, respectively, said drive coupler having an outer surrounding region surrounding the axis; a latch which has an actuated end, and which is received in and which is radially movable in said drive coupler between a latched position where said actuated end is disposed radially and outwardly of said drive coupler, and an unlatched position; a tappet configured to be axially movable relative to said drive coupler such that, when said latch is in the latched position, said tappet is axially engaged with said latch to move with said drive coupler to the depressed position so as to displace said air control unit to the entry state, and such that, when said latch is in the unlatched position, said tappet is axially disengaged from said latch to permit axial movement of said tappet so as to displace said air control unit to the shut-off state; an output spindle having a shank which is disposed in said housing and which extends axially to terminate at a bit-side end exposed out of said housing, and at a clutch-side end portion disposed opposite to said bit-side end, said clutch-side end portion having a flared segment which extends outwardly and radially and which has an upward bearing surface, said upward bearing surface defining a plurality of ball-engaging areas angularly displaced from one another about the axis; a coupling shell member which surrounds said outer surrounding region of said drive coupler and which has an inner shell surface including actuating and engaging regions axially opposite to each other; and an override clutch unit including a driving clutch half disposed on said outer surrounding region of said drive coupler, and including a plurality of locating areas which are angularly displaced from one another, a plurality of balls, each disposed in a respective one of said locating areas and to be rollably engaged with a respective one of said ball-engaging areas so as to permit anti-frictional rotation of said drive coupler relative to said output spindle in the non-working position, and a driven clutch half disposed on said engaging region of said inner shell surface of said coupling shell member, and configured to abut said balls against said locating areas such that an override movement of said driven clutch half which arises from an increased load mechanically transferred from said bit-side end to said engaging region, brings said actuating region to move axially so as to force said actuated end of said latch to the unlatched position.