| 摘要 |
A pneumatic impulse wrench comprising a motor (12), a housing (10) with a pressure air inlet passage (22), an exhaust air outlet passage (23), and an air flow control valve (25) provided in the exhaust air outlet passage (23) and including a valve element (30; 60) shiftable between an exhaust air flow restricting position and an exhaust air flow non-restricting position, wherein a rigid contact member (31) is provided in the housing (10) to positively define the exhaust air flow restricting position of the valve element (30; 60), and a bypass passage (43a, b, c; 63a, b) of a well defined flow area provided to let through a limited exhaust air flow as the valve element (30; 60) occupies the flow restricting position in engagement with said contact member (31), thereby accomplishing a limited motor speed during an initial low load stage of a tightening process and, hence, a minimized risk for overtightening a stiff screw joint the very first delivered torque impulse. |
