Hydraulic closing unit

A hydraulic closing unit having an annular force cylinder for the production of a closing force, a locking bushing, an actuator for turning the locking bushing from a first angular position into a second angular position, a push rod which passes axially through the force cylinder and the locking bushing, an outer toothing on the push rod and an inner toothing in the locking bushing, this outer toothing and this inner toothing being so developed complementary to each other that in the first angular position of the locking bushing they permit an axial pushing of the push rod through the locking bushing and that, in the second angular position, the inner toothing engages in the outer toothing for the transmission of an axial force, characterized by the fact that the force cylinder is developed as a double-acting annular pressure cylinder having in each case a first pressure chamber for producing a closing force and a second pressure chamber for producing an opening force, and that a piston of said force cylinder is secured against rotation and is coupled via a screw thread to the locking bushing.