Abstract: A permeator has a cylindrical body whose filtration chamber accommodates a embrane element. Arranged to both sides from the filtration chamber along the axis of the body are permeate withdrawal chambers, communicating with the membrane element by way of permeate withdrawal pipe branches and each furnished with its own permeate withdrawal pipe branch.

Abstract: The invention relates to impact wrenches for tightening threaded joints comprising an impact clutch accommodated in a housing and having a hammer which is axially movable for imparting each blow, and a device for automatically limiting the number of blows to a pre-set number of blows. The device for automatically limiting the number of blows comprises a blow number setter, a movable member directly co-operating with the hammer and axially movable upon each axial displacement of the hammer so as to enable the axial displacement of the hammer until a pre-set number of blows are delivered, and a locking device for locking the movable member against displacement in the position preventing further axial movement of the hammer after the ultimate blow of the pre-set number of blows is delivered. Thus the possibility of imparting blows in excess is eliminated without deenergization of the impact wrench drive, and the construction of the impact wrench is simplified.