GB1035816A - Improvements in or relating to presses - Google Patents

Abstract

1,035,816. Cutting out presses; hydraulic presses. BRITISH UNITED SHOE MA. CHINERY CO. Ltd. March 21, 1963 [March 23, 1962], No. 11116/62. Headings B4B and B5F. A press for cutting out pieces of sheet material comprises a lower platen 12, Fig. 2, to support the sheet 28 to be cut out, an upper platen 20 and hydraulic operating means comprising a piston and cylinder assembly 24, 26 at each end of the movable platen and two pumps 174, 176, Fig. 8, one of which is connected to the cylinder of one assembly above the piston and to the cylinder of the other below the piston and the other pump is connected to the cylinder of said one assembly below the piston and to the cylinder of said other assembly above the piston, the press also comprising balancing valve means including normally closed ports 196, 194 leading from the pressure lines from the two pumps so as to respond to relative advance of one end of the platen ahead of the other by bleeding pressure fluid from the pressure line leading to the cylinder of the assembly at the more advanced end of the platen. A vertical rod 54 depends from each end of the crosshead 18 being connected via linkwork 60, 62, 64, 66 to the spindle 76 of the balancing valve. If the upper platen 20 becomes misaligned, the lever 66 will rock about some other point than the centre of its pivotal connection with the spindle and move the spindle to left or right. The valve has a central port 192 leading to the reservoir, a port 194 connected to line m and line a leading from pump 174, and a port 196 connected by line n to pressure line c leading from pump 176. When e.g. the left-hand end of the platen advances relatively ahead of the right-hand end, the spindle 76 moves allowing fluid to bleed from line a, so that the platen is restored to its horizontal position while maintaining full pressure above both pistons. By energizing solenoids 182D, 184D, the solenoid valves 182, 184 permit fluid to pass through lines b, f, g and d, k, g to the reservoir causing a downstroke of the upper platen; de-energization of solenoids D and energization of solenoids U causes flow from lines a, c through the valves to the cylinders 26 below the pistons to raise the platen, the pressurizing of lines b, d opening the valves 178, 180 to permit a higher rate of fluid flow and a correspondingly faster movement of the platen. Since the effective areas of the under-sides of the pistons are larger than the effective areas of the upper sides, the platen is raised by differential pressure when the fluid pressure on both sides is equalised. Non- energization of the solenoids holds the upper platen raised by fluid below the pistons 24 and in the lines b, f and d, k closed by the valves; the pumps then idle and the fluid recirculctes via lines a, e, g and c, h, g. The hydraulic system is controlled via switch buttons 50 at opposite sides of the lower platen and a system of relays. The upper and lower limits of the stroke of the press are adjusted by knobs 126, 128, Fig. 2; a plunger 144 associated with knob 126, Fig. 6, is extended within the housing and its head 150 bears on a plunger 152 of a microswitch 154. Movement of its associated lever 142 releases the knob and opens the switch 154 so that the platen will not move while its height-control switch 118 is adjusted. By rotating the knobs, slides 106, 108 (Figs. 5 and 6) which carry microswitches 118, 120 are set in positions so that the switches are actuated by rollers 122 lying in the path of a shoulder 124, Fig. 5, on a control rod 92 secured to the cross beam 18, Fig. 2. The slides 106, 108 also carry arms which project through the front wall of the housing and carry pointers 158, 160 which indicate on a graduated scale the positions of the microswitches 118, 120 and thus the upper and lower limits of travel of the upper platen 20. An electrical circuit is provided which reverses the platen when it has reached the bottom of its stroke and terminates its withdrawal from the other platen. The work-table 32, Fig. 2, is slidably mounted on rollers 34 to facilitate positioning of the shaped knives 33 on the material 28 to be cut. Under sufficient pressure from the upper platen, the table is pressed against the force of springs below it on to the lower platen 12. The table is movable by two handles 50 necessitating the use of the operator's both hands and adjacent to which are the two control switches which must be manually actuated to start a cycle: release of either switch during the operation results in the platen being withdrawn.