Abstract: A hydraulically-actuated blade actuator selectively actuating the shear blades associated with a rotary cutter for cutting the harvested crop into small pieces prior to the baling or collecting process in agricultural harvesting machines. The hydraulic cylinders (12) are disposed within a parallelpiped block (14). A plurality of hydraulic cylinders (12) are arranged adjacent to one another in a block (14). A plurality of transversely extending borings (18, 19, 20) are arranged in the base region of each one of the blocks (14), the borings extending continuously through each of the assembled blocks such that each one of these borings (18, 19, 20) is connected to the space within a hydraulic cylinder (12) via a respective connecting bore (21, 22, 23). Each of the borings (18, 19, 20) is provided with an appertaining on-off valve (29, 30, 31) and an accumulator (32, 33, 34).