GB746390A - Improvements in or relating to hydraulic presses having at least two press cylinders - Google Patents

Abstract

746,390. Hydraulic presses. AKT.-GES. C. ZSCHOKKE ZWEIGNIEDERLASSUNG DOTTINGEN. Oct. 23, 1953 [Oct: 24, 1952], No. 29416/53. Class 69 (2). A hydraulic press having at least two cylinders, each of which transmits pressing forces to a point of attack on a common press beam, is provided with means controlling the admission and exhaust of liquid to and from the cylinders so as to ensure parallel motion of the press beam. Cylinders 4 with double-acting pistons 5 acting on a press beam 3 are supplied with liquid from a pump 11. The pump supplies liquid through a pipe 13, in which a main valve 15 is situated, to pipes 16. A valve 17 is associated with each cylinder 4 and controls the admission of fluid from a pipe 16 to either end of the cylinder. Valve pistons 32 of the valves 17 are interconnected through racks 40, pinions 42 and a shaft 41 rotatably mounted on the beam 3. Depression of a hand lever 25 or foot lever 26 raises the piston 29 of the main valve 15 to put the pipes 16 into communication with the pump, and also, through springs 44 and an arm 43, raises the valve pistons 32 so that an upper chamber 6 of each cylinder 4 communicates with a pressure pipe 16, and a lower chamber 7 communicates with a relief pipe 19. The press beam is thereby moved towards the table 1. Should, for example, the left hand end of the beam move slightly ahead of the right hand end, the shaft 41 is correspondingly inclined. The right hand rack 40 is prevented from moving upwardly due to the piston 32 abutting against a valve cover 36. The left hand rack is therefore moved downwardly, entirely or partly closing the control ports communicating with the upper and lower chambers of the associated cylinder 4. The corresponding piston 5 is thus halted or moved slowly until the other end of the beam has caught up. If the levers 25, 26 are put in their intermediate position the valve pistons 32 assume the position shown, in which the chambers 6, 7 of the cylinders are closed and the press beam is maintained in the position it happens to occupy. To open the press, lever 25 or 26 is raised. Valve 15 again puts pipes 16 into communication with the pump, and pistons 32 are lowered, putting the chambers 7 into communication with the pressure pipes 16, and chambers 6 into communication with the relief pipe 19. Parallel motion of the press beam is again ensured during its rising motion, move ment of the control piston at the lagging end being prevented by the bottom cover 37 of the corresponding valve.