Patent GB-649987-A (GB)
Title: Improvements in injection moulding apparatus
IPC: B29C45/12
Filed: 1948-01-30
Abstract: 649,987. Injection-moulding machines. UNITED STATES RUBBER CO. Jan. 30, 1948, No. 2758. Convention date, March 26, 1947. [Class 87 (ii)] An injection-moulding apparatus comprises in combination, supporting cross-heads 1 and 2 at least one of which cross-heads being movable relative to the other, means carried by one cross-head for supporting a plurality of hinged two-part cavity moulds 16 at an angle relative to the plane of the cross-head 2, means for moving the cross-heads towards and away from each other so that the parts of the moulds are clamped together when the cross-heads are moved together, and means for injecting mouldable material into the cavities of the moulds. A vertically movable cross-head 2 of a hydraulic press of conventional type carries two laterally spaced blocks 5 supporting a heated platen 6 which in turn carries a turret 7 rotatable on sprung ball bearings 11. The turret is in the form of a truncated pyramid or cone and has a plurality of flat surfaces 15 around its periphery on which are mounted individual two-part moulds 16 hinged at 20 and adapted to break as shown in Fig. 2. A guide pin 21 seats itself in the opening 22 of the mould half 17 when the mould is closed. In order to hold the mould parts in closed position during injection an upper fixed cross-head 1 is adapted to support a ring 26 having steam-heated channels 29, 30, the ring being fixed to a heated platen 25. A series of wedges 32 are sprung by spring washers 35 against the ring and are supported by bolts 34, so that each wedge has an inclined surface 33 adapted to engage the outer surface 23 of a mould. A plunger 42 is fastened to a support 43 extending between the blocks 5, and itself extends through an opening in platen 6. The plunger is received in a chamber or channel 41 of the turret 7 and has bevelled surfaces 51 adapted to actuate knock-out rods 52. The support 43 has ears 45 which overlie bars 46 carried by shock-absorbing lift rods 47, so that as the support moves downwardly when the ram 4 is lowered it will be brought to rest and be held by the bars 46. The knockout rods 52 co-operate with and ride along the bevelled surfaces 51, the other ends of the rod engaging an equalizer bar 53 which rests in a groove 54 on the flat surface 15 and is adapted to engage and move a plurality of knock-out pins 55 which act to separate the mould halves. Additional pins may be provided to eject or loosen the moulded articles. In operation, the mould halves are closed and the ram 4 moved to raise the cross-head 2. Since the parts are initially in the position shown by Fig. 2, the cross-head 2 moves the supporting blocks 5, the platen 6, and the turret 7 upwardly relative to the plunger 42, so that the plunger moves relatively downwardly in the chamber 41 moving the bevelled surfaces 51 out of engagement with the knock-out rods 52. Further movement of the cross-head 2 causes it to engage the member 43 to lift it off the bars 46 so that all the lower parts are moved as a unit towards the upper cross-head 1. Continued upward movement causes the turret 7 to enter the ring 26, thus clamping the mould parts together by the imposed wedging action. A biscuit of rubber or other mouldable material is then placed in the cylinder 36 and the piston 37 is moved by a conventional hydraulic mechanism (not shown) into the cylinder to force the material through the radial channels 39, 40, into the closed moulds. The compound is then cured under heat and pressure. After curing, the cross-head 2 is lowered and the outer surfaces 23 of the moulds are broken away from the wedges. As the cross-head 2 is lowered further it reaches a point at which the support 43 is brought to rest on the bars 46. Continued downward movement of the crosshead with the blocks 5, platen 6 and turret 7 causes the chamber 41 to move downwardly relative to the plunger 42 which is held stationary with the support 43 by the bars 46. The knock-out rods are thus moved by the surfaces 51 to break the moulds, the outer halves of which inoulds are pivoted to rest on arms 56. The turret may be rotated in order to remove the moulded articles and permit cleaning of the mould cavities before re-closing.