Screw actuated press unit

A screw actuated press unit comprising:

• a casing;
• an actuating screw rotationally journalled in the casing;
• a rotation motor drivingly coupled to the actuation screw;
• a nut assembly cooperating with the actuation screw;
• a thrust rod rigidly connected to the nut assembly and extending out of the casing for connection to a work piece;
• a spring element;
• and
• a locking device which rotationally locks the nut assembly to the casing while permitting axial movement of the nut assembly at rotation of the actuating screw;
• wherein said locking device comprises at least three radially extending roller studs mounted on the nut assembly in a common axially directed row, an axially extending slot in the casing, and two parallel guide rails disposed on edges of said slot;
• wherein said roller studs engage said guide rails to prevent rotation of the nut assembly during press unit operation,
• wherein said middle roller stud is supported on a bearing block which is movably guided in a transverse direction relative to the nut assembly and relative to said other two of said at least three roller studs,
• wherein said spring element is a leaf spring element is arranged to exert a bias force on said roller studs against said guide rails for eliminating rotational play between the nut assembly and the casing, such that the leaf spring presses a middle one of said at least three roller studs that is located between the other two of said at least three roller studs in a first transversal direction against one of said guide rails, and such that the leaf spring presses said other two of said at least three roller studs in a second transversal direction opposite to the first transversal direction, against the opposite guide rail,
• wherein the nut assembly is cylindrical,
• wherein the casing is configured with only said two parallel guide rails for preventing rotation of the nut, and
• wherein the nut assembly is arranged freely in the casing such that rotation of the nut assembly is prevented only by the roller studs engaging the guide rails.