FIELD: mechanical engineering, in particular, microstep and accelerated movement of actuating mechanisms of hydraulic metal-working machines. SUBSTANCE: actuating unit is connected with central movable wall of bellows-type hydraulic cylinder and is movable in accelerated mode of operation, when wall and bellows-type cylinder housing are rigidly fixed with respect to ball roller screw pair nut bracket, which are driven as single unit by adjustable-frequency reversible step motor. Microindexing movement of actuating unit is provided by rigid fixing of bellows-type hydraulic cylinder relative to position of this cylinder upon termination of accelerated movement, when one side of dosing bellows is coupled to bracket of mentioned nut and it is movable in one or other direction by step motor for dosing, while other side of dosing bellows is permanently rigidly coupled to bracket, which is connected to bellows-type hydraulic cylinder housing. Such construction allows accelerated and microstepped motions of different length, speed and direction to be performed by one motor. EFFECT: increased efficiency and enhanced reliability in operation. 1 dwg
