GB770638A - Hydraulically operated machine - Google Patents

Abstract

770,638. Shearing. CASTLE, J. B. Dec. 7, 1954 [June 25, 1954], No. 35380/54. Class 83 (4). [Also in Group XXIX] The ram of a hydraulically-operated shearing- machine is moved by two pistons connected in series, the area of the second piston being equal to the area of the underside of the first piston so that the rate of travel of both pistons is the same. Cylinders 33, 35 have pistons therein connected to the ram and are supplied with liquid from a pump 43 driven by a motor 45. A main valve 51, operated by solenoids 53, 55 controls the flow for the up and the down strokes. To lower the ram, liquid is directed through a pipe 57 to cylinder 33 and liquid from beneath the piston in cylinder 33 passes through a pipe 59 to the cylinder 35. Liquid exhausted from cylinder 35 passes through a counterbalance valve 63, a pipe 61, and the valve 53 to a reservoir 47. The reservoir is formed by a pipe of large diameter extending between the end plates of the machine. The valve 63 has a spring 67 of sufficient strength to prevent the ram falling by gravity. During a down stroke of the ram, the pressure in a pipe 69 increases and overcomes the spring and opens the valve. The ram is held on its slides by jacks 269 supplied with liquid from an accumulator 219 having an air cushion 223 and a valve 225 for charging. Springs 277 in the jacks keep the ram on its slide under no load conditions. The machine is controlled by a foot-operated switch. A shunt circuit can be provided to take over after initiation of stroke so that the foot need not remain on the pedal. Upper and lower limit switches 81, 83 are provided, the lower switch having a cam profile 107 that can be rotated to adjust the travel. A bar 175 pivoted at its centre and connected by a cable 179 passing round pulleys 181, 183 on the ram to a fixed point 185 maintains the ram level by means of microswitches 165, 167. Levelling of the ram is effected on the up stroke and if the piston in cylinder 33 is lagging, one of the microswitches energizes a solenoid 156 controlling a valve 155 whereby fluid by-passes the cylinder 35 and flows along the pipe 59 to give extra lift to the piston in cylinder 33. If the right-hand piston is lagging, a solenoid 161 is energized and a valve 159 operated so that the left-hand cylinder is by-passed. If the ram tilts beyond the range of switches 165, 167, one of two microswitches 285, 287 is operated, and cuts the power supply to the machine, and a valve 291 is also opened to divert the pump output to the reservoir. A push-button 295 allows the operator to connect the power supply temporarily. The material to be cut is held down by pistons 205 in cylinders 195. Liquid is supplied to the cylinders via a pipe 217 from the accumulator 219. When the foot-operated switch 79 is closed, a solenoid 237 is energized, a valve 235 opened, and liquid flows from the accumulator through a counterbalance valve 231 to the cylinders 195. When the ram moves down, the cylinders 195 are forced down over the pistons 205 and liquid returns to the accumulator via another counterbalance valve 229. Oil which leaks past the piston passes through a pipe 251 to a reservoir 253 from which it is pumped back to the accumulator by a pump 255. The cylinder of the pump may be fixed to the machine and the piston fixed to the ram. The normal partiallyextended position of the pistons 205 is adjusted by a needle-type valve 249. A dash-pot 245 on a timing relay 129 allows the pistons 205 to secure the work before a " down " relay is energized and the ram moves towards the work.