Patent ID: 6883619

Claim:
A bidirectional pneumatic impact wrench comprising: a housing comprising a motor casing having a front, a rear, a bottom, a motor chamber defined longitudinally through the motor casing, a forward air passage and reverse air passage symmetrically defined in the motor casing at the rear, a valve chamber defined in the rear under the motor chamber and a motor-air discharge port communicating between the motor chamber and the valve chamber; and a handle integrally extending from the bottom of the motor casing and having a compressed air passage with an inner opening communicating with the valve chamber, an exhaust air passage with an inner opening communicating with the valve chamber and an air supply valve mounted in the compressed air passage to control compressed air to the valve chamber; a front assembly attached to the front of the motor casing; a hammer assembly mounted in the motor chamber and connected to the front assembly; a pneumatic motor mounted in the motor chamber, connected to the hammer assembly to drive the hammer assembly and having a rear, a reverse air inlet and forward air inlet defined in the rear and an air outlet communicating with the motor chamber; a rear assembly attached to the rear of the motor casing and comprising a rear cover attached to the rear of the motor casing to cover the motor chamber and having an inner side, an outer side, a forward air passage and reverse air passage symmetrically defined in the inner side of the rear cover and a control valve hole defined through the outer side of the rear cover and aligned with the valve chamber in the motor casing, where the forward air passage in the rear cover communicates with the forward air passage in the motor housing to the forward air inlet of the pneumatic motor, and the reverse air passage in the rear cover communicates with the reverse air passage in the motor housing to the reverse air inlet of the pneumatic motor; and a gasket mounted between the rear of the motor casing and the rear cover; and an air control valve mounted at the outer side of the rear cover and comprising a rotatable shaft rotatably held in the control valve hole and the valve chamber and having an inside end inserted into the control valve hole and extending into the valve chamber, an outside end, an exterior surface, a spiral forward air groove and reverse air groove symmetrically defined in the exterior surface to direct the compressed air coming from the inner opening of the compressed air passage to selectively enter the forward air passage and the reverse air passage and an annular slot defined in the exterior surface adjacent to the inside end between the openings of the compressed air passage and the exhaust air passage; a knob attached to the outside end of the shaft to turn the shaft; a positioning device mounted in the knob to hold the knob in place; and an O-ring mounted in the annular slot to keep the compressed air from directly being exhausted through the exhaust air passage.