Patent GB-723824-A (GB)
Title: Improvements in or relating to presses with hydraulically operated press plungers
IPC: B29C45/70
Filed: 1952-08-12
Abstract: 723,824. Hydraulic presses. STUDLI, H. Aug. 12, 1952, No. 20294/52. Class 69 (2). [Also in Group V] A press includes a first press plunger of large cross-section and short stroke and a second press plunger of smaller cross-section and longer stroke, the second plunger acting in a direction opposite to that of the first plunger. A press plate is guided on columns and is taken along by the second plunger during a first part of its forward movement and then locked in its end position on the columns, whereupon the second plunger continues its forward movement. The press may be a transfer or moulding press, but as shown is an injectionmoulding press. The first press plunger 59 slides in a stationary cylinder block 2 secured to four columns 3, and its function is to apply a high clamping pressure to two mould parts 33, 58. The second press plunger is a piston rod 9 having a piston 8 slidable in a cylinder 4 secured to the upper end of columns 3, and its lower end terminates in a plastic - material - injecting plunger 57. The press plate 20 slides on the columns 3 between an upper position, Fig. 8, and a lower mouldclamping position, Fig. 1, in which it is locked on the columns and provides a top abutment to resist the upward thrust applied by plunger 59. The piston rod 9 carries a yoke 11 from which depend two rails 12 which are slidably disposed in plate 20 but support the latter in the raised position of Fig. 1. Each rail has a cam groove 15 which receives a pin 17 secured to a rack 18 having teeth 31 meshing with teeth 30 on two sleeves 27. Each of the four sleeves 27 is screwed into a bore in plate 20 and has on its interior six grooves 28 and six threaded splines 29. The columns 3 also have six grooves 24 and threaded splines 25, and when the plate 20 is in the mould-clamping position (Fig. 1) the sleeves 27 are turned so that the threaded splines 29 engage the threaded splines 25 to lock the plate on the columns. A second plate 26 is secured to the plate 20 by means of hinged bolts 38 and carries the injection cylinder 34. A powdered-materialfeeding hopper 42 is fastened to plate 36, and material is delivered therefrom by a piston 43 operated by a lever 46, 50 and spring 46<SP>1</SP>, the delivered material falling down funnel 56 into the injection cylinder. The end 53 of lever arm 50 may be swung into the inoperative position shown in dotted lines. Mould part 33 is secured to plate 20 and mould part 58 rests on plunger 59. The press may be horizontal. Operation. The parts being in the raised position shown in Fig. 8, the operator moves valve rod 114 from the rest position M to the downstroke position P, whereupon the following movements (1) to (5) occur automatically: (1) pressure fluid depresses piston 8, which descends with the plates 20 and 36 and their appurtenances, plate 20 coming to rest on flanges 3<SP>1</SP> on columns 3; (2) the piston 8 continues its descent, and the rails 12 slide through plate 20. The pins 17 are thus forced sideways out of the inclined portions 16 of cam grooves 15 into straight portions, and this movement of the pins moves racks 18 and sleeves 27 so that the threaded splines 29 on the sleeves engage the threaded splines 25 on the columns 3. Simultaneously (3) a cam 68 on one rail moves levers 70, 71 to operate valve 81 to (a) interrupt pressure fluid supply to the upper side of piston 8 so that the latter is halted and (b) supply pressure to raise plunger 59 to clamp the mould parts together; (4) when the required pressure on plunger 59 is reached, valve 98 opens and pressure is again directed to piston 8 to depress it, whereby the material is injected into the mould; (5) when the required injection pressure is reached a safety valve 119 opens. After an interval to allow the material in the mould to harden, the operator moves the rod 114 to position R, whereupon the following movements (6) and (10) occur automatically: (6) valve 10 is opened to release pressure on plunger 59; (7) pressure is applied to the underside of piston 8 to raise the latter. During the initial ascent of piston 8, the plate 20 remains in the locked, Fig. 1, position, but when the inclined part 16 of the cam grooves 15 reaches the pins 17 the plate is released from the columns and is raised by means of the rails; (9) as the piston 8 rises, (a) an abutment (not shown) on yoke 11 engages lever part 53 to effect feeding of material from the hopper into the injection cylinder, and (b) projections 66 on plate 20 act on nuts 67 on rods 65 to raise ejector 61 to discharge the moulded article from the mould; (10) at the end of the upward stroke of piston 8, a projection 20<SP>1</SP> on plate 20 raises a rod 112 to restore rod 114 to its neutral position M. A stop valve 123 is provided by which the piston 8 may be stopped in any desired position.