发明概况冲击式气扳机由发动机,回转冲击机构和扳轴组成。本发明在气扳机的发动机与冲击机构之间、或在冲击机构与扳轴之间安有一个扭力棒;扭力棒上有一个件,对扭力棒预加载或预扭转。这样,只有当扭力棒上的扭矩超过预选数值后,扭力棒才扭紧。气 SUMMARY OF THE INVENTION The impact gas trigger consists of an engine, a rotary impact mechanism and a wrench shaft. In the present invention, a torsion bar is provided between the engine of the gas trigger and the impact mechanism, or between the impact mechanism and the wrench shaft; there is a member on the torsion bar to pre-load or pre-torque the torsion bar. In this way, the torsion bar is only tightened when the torque on the torsion bar exceeds a preselected value. gas