Patent GB-1025976-A (GB)
Title: Improvements in or relating to presses suitable for use in performing cutting operations on sheet materials
IPC: C14B5/00
Filed: 1963-01-29
Abstract: 1,025,976. Cutting-out presses. BRITISH UNITED SHOE MACHINERY CO. Ltd. Jan. 29, 1963 [Jan. 31, 1962], No. 3538/63. Heading B4B. In a cutting press for operating on sheet materials comprising a support for a workpiece, a platen movable, by fluid pressure operated means, from an initial position to press a cutting edge portion of a die through the workpiece and means for reversing the direction of movement of the platen when the cutting edge portion of the die has penetrated the workpiece, a regulating valve is provided which is arranged, after a predetermined amount of movement of the platen in the reverse direction, to prevent the pressure fluid from causing further movement of the platern and thereby determine the initial position of the platen. As shown, column 2 of a swinging platen 1 is secured to the piston rod 6 of a piston 5 movable in a cylinder 4 the upper and lower ends of which are connected by pipes 8, 9 to a solenoid valve 10 leading through a pipe 11 to a pump 12. The lower end of cylinder 4 is closed by a cover 13, an extension 17 of which has screwed thereto a member 22 pinned at 24 to a control rod 23 which is adjustable by a handle 25. The piston-rod 6 has a bore 19 which narrows to a bore 20 so as to provide a valve seat 30. Transverse bore 21 connects bore 20 to the pressure fluid supply. A sleeve 27 is urged by spring 26 towards a fixed abutment ring 28 on the rod 23. The sleeve 27 together with bores 19, 20 and valve seat 30 constitutes a regulating valve 31. The valve 10 comprises a housing 35 with an annular groove 45 and a spring-supported stem 36 provided with bores 39, 40 through which pressure fluid flows to the supply. Above the stem 36 is a pusher member 41 engaging an armature 42 of a solenoid 43 connected to the pump 12. The solenoid is controlled by an adjustable limit switch 57 engageable with an abutment 62 on the rod 23. When the solenoid is energized, the valve stem 36 is pushed downwardly so that pressure fluid flows from pump 12 to pipe 8 and the platen is moved downwardly to perform a cutting stroke. During this movement, an opening 29 between the sleeve 27 and the valve seat 30 is closed. On de-energization of the solenoid at the end of a cutting stroke, the valve stem 36 is returned to its initial position so that return movement of the platen is effected hydraulically. The pressure fluid then flows through the pipes 8 and 9 into the cylinder 4 above and below the piston 5. The valve 31 is still closed so that no pressure fluid can escape. Since the piston 5 is a differential one, the platen is moved upwardly and this movement is accelerated since the pressure fluid in the upper part of the cylinder 4 does not flow back to its supply. The sleeve 27 remains in engagement with the valve seat 30 until the sleeve abuts ring 28. The pressure fluid fed by the pump further raises the platen until the opening 29 is large enough to permit pressure fluid to flow through it into the bores 20, 21 and into the supply under no pressure. The opening 29 does not become larger than necessary for the flowing pressure fluid to support the total weight of the platen 1, column 2 and piston 5. The limit switch 57 may be replaced by an insulated contact pin connected to the grid of a thyratron so that reversal of the platen is effected by the contact pin. Alternatively, reversal of the platen may be initiated by contact of the die with an electrically conductive work support as disclosed in Specification 764,634. In a modification, Fig. 3 (not shown), an auxiliary cylinder is formed in the cover and has movable therein a piston the heightwise position of which is adjustable by a control valve. In another modification, Fig. 4 (not shown), reversing movement of the platen is effected by a solenoid-operated spring-influenced sleeve arranged within the bore of the piston-rod.