Patent GB-625427-A (GB)
Title: Hydraulically operated transfer molding presses
IPC: B29C45/02
Filed: 1946-05-25
Abstract: 625,427. Injection-moulding machines. DEFIANCE MACHINE WORKS, Inc. May 25, 1946, No. 15934. Convention date, June 12, 1945. [Class 87 (ii)] [Also in Group XXIX] Leftward movement of a bar 122, Fig. XIX, from a neutral position " N to position "C" opens a valve 120 and allows low pressure fluid to flow from a pipe 118, through pipes 129, 131, to the main cylinder 14 of a transfer moulding press, where it causes the main platen 6 to rise and thus engage a mould part 27, mounted on the platen, with a mould part 42, mounted on a floating platen 7, and then force the platen 7 against a fixed head 3. During this upward movement fluid is exhausted from pull-back cylinders 20 through pipes 132, 137, 138. Low pressure fluid also passes through a pipe 130 and a passage 102 into a cylinder 63 which is attached to the transfer ram 59, but movement of the ram is prevented by push-back cylinders 70 to which high pressure fluid is continually supplied through pipes 140, 139. To inject material from the transfer pot 56, mounted in the platen 7, into the mould and to clamp the mould in closed position, the bar 122 is moved to position " T," to open the valve 141 and allow H.P. fluid to flow through pipes 140, 144, 131, 130 to the main and transfer cylinders respectively. After curing of the material in the mould, the bar 122 is moved to position " R " to cause a slight release of pressure in the cylinders, by allowing fluid to exhaust through the first stage 145 of a double poppet valve 128. Ths slight release allows the platen 6 to fall under its own weight and the push backs 70 to raise the transfer ram. If the mould does not open easily, the bar 122 is moved to position " O " to fully open the valve 128 to allow free flow to exhaust, and to close a valve 153 which causes the pull-backs 20 to be cut off from exhaust, and H.P. fluid to be supplied through pipes 140, 149, 132 to the pull-backs 20, which then positively lower the platen 6. An adjustable choke valve 142 is provided in the hydraulic system. Packing between relatively movable members of the hydraulic system, particularly those located above the moulds, e.g. the push-backs, is mounted in the outer member to be readily accessible, thus helping to control leakage of fluid and prevent it from contacting the plastic material. To prevent damage to the transfer ram 59, if e.g. the press were operated without material in the pot 56, a throttling valve 103 is provided at the outlet end of the passage 102 bored out of the piston 64 around which the cylinder 63 works. This throttling valve also helps to delay injection which helps to ensure that the mould is closed before injection. The lower mould part 27 is supported on the platen 6 by a series of bars 28, Fig. XV, brackets 29 and stop clamps 31. Dowels are provided on the part 27 to engage bushings on the upper mould part which is secured to the floating platen 7 in a similar manner to that in which the part 27 is secured to the platen 6. The.platen 7 is supported on rods 50 secured to a movable head 8. To allow for expansion of the platen when the mould is heated lateral freedom is allowed in the connection of the rods 50 with the platen. Top and bottom ejection is provided. The lower ejecting mechanism comprises end frames 33 which actuate ejector pins 35. The frame 33 is mounted on four rods 37 which pass through holes in the platen 6 and are of such a length that they contact the base 1 slightly before the platen reaches the bottom of its stroke. Springs 38, in compression, retract the pins 35 as soon as the platen starts its upward stroke. The upper ejecting mechanism comprises bars, clamped in end frames 49 connected to actuating pins 46. The frame 49 is carried by rods 51 mounted on the head 8. Springs 53 are provided to pull the ejector frame up. To actuate the upper ejection means, rods 54 are secured to the frame 49 and at their lower ends pass through the platen 6, their length being so adjusted by nuts 55 as to actuate the system when the lower platen reaches the end of its stroke. The bottom limit of travel of the platen 6 is limited by a pair of adjustable rods 18 mounted on the base 1. To adjust the space between the moulds to provide adequate space for removing the moulded articles, the means which fix the head 3, Fig. VI, to the side rods 2 are released, blocks are placed between the platens and the head 3 raised by the main cylinder and then fixed again to the rods 2. The transfer pot 56 is held in the platen 7 by a threaded ring 57 which abuts against an annular spring 58. The upper surface of the platen 7 is relieved around the transfer pot so that when the platen is forced against the head 3 no additional force is transmitted through the walls of the pot to the mould part 42. The sprue opening 60 is formed tapering downwards so that the sprue breaks as near the runners to the mould cavities as is possible. To ensure that the sprue and the waste material left in the pot is removed from the pot, the bottom of the ram 59 is provided with a tapering tee slot 62. The transfer ram 59 may be heated by steam, hot water or oil, or an electric heater of the radiant type. The temperature of the ram may be thermostatically controlled.