Abstract: The power wrench comprises a housing (10) with a rearward housing member (12) which forms a protection against bursting for the hydraulic cylinder (27) arranged within the housing member (12). Through a joint (38, 40) and self-aligning, the piston (35) acts upon the lever (18) which is supported coaxially to the ring (14). The lever (18) comprises a ratchet element (17) being supported at the lever (18) by a semisperical pressure member (20). The power wrench can be submitted to extremely high hydraulic pressures without a danger to the environment.

Abstract: The piston-cylinder unit (30') of a power wrench presses against the arm (16), by means of a ball and socket joint (44, 45), for swivelling the ring (11), which is connected secure against rotation to the wrench head to be turned. The piston (35) and the arm (16) have complementary spherical surfaces (40, 41) which press against each other. The dimensions of the spherical surfaces can be selected in dependence on the maximum power to be transmitted. The result is a uniform power distribution and a force-free adaptation of the movements of piston (35) and arm (16), without jamming and tilting.