is moved forwards to abut against the bottom of recess 53 now rod 48 will follow the inner contour of recess 53 until it reaches the tangent point between recess 53 and the bore 51 at this moment the forward end of release rod 48 falls down into bore 51 and the cup 41 the maneuver rod 46 and shut off valve 38 are displaced forwards the shut off valve 38 is closed this position is illustrated in fig2 the release mechanism is re set in that the supply valve 36 is closed the spring 47 then looses its support from the pressure air and is not able to withstand the load of spring 44 and maintain valve 38 in closed position the cup 41 release rod 48 maneuver rod 46 and shut off valve 38 is then reclosed and the release rod 48 is pivoted into a tilted position by means of spring 49 the characteristic features of the release mechanism 37 as regards operation are specifically related to the characteristic of the above described slip clutch 12 the latter is characterized in that after a completed tightening operation including slippage at the desired maximum torque level it stops in any position and does not tend to seek for any specific reengagement position defined by a certain angular relationship between the driving and driven clutch halves this means that the release mechanism of.