Fluid pressure actuated device

A material splitting machine which includes a cutting region for a material to be split, a ring roller in said cutting region for applying pressure to the material, scrapers associated with, and arranged to guide the ring roller, a pressure roller acting on the ring roller, and a fluid pressure actuated device comprising a cylinder, a double acting piston movable in the cylinder by pressurized fluid, a rack movable with the piston, a pinion gear co-operating with the rack, a cam connected to the pinion gear for angular movement therewith, a lever system connected to the pressure roller and a connecting rod connecting the cam to the lever system for effecting displacement of the pressure roller from the cutting region in response to movement of the piston from a first position adjacent to a first end of the cylinder towards a second position adjacent to a second, opposite end of the cylinder, said cylinder having first and second ports communicating with the first and second ends of the cylinder and a third port between the first and second ports, conduit means for respectively connecting the ports to a source of fluid pressure and to exhaust, the arrangement being such that connection of the first port to the fluid pressure source while the second port is connected to exhaust will cause the piston to move from said first position to said second position so as to effect maximum displacement of the pressure roller, whereas connection of the fluid pressure source to the first port when the piston is in said first position and while the third port only is connected to exhaust will cause the piston to move from said first position to a position in which it closes the third port and between said first and second positions so as to effect limited displacement of the pressure roller.