Patent GB-543840-A (GB)
Title: Improvements in and relating to pneumatic-hydraulic die-casting and injection-moulding machines
IPC: B29C45/67
Filed: 1940-07-11
Abstract: 543,840. Hydraulic presses ; casting-machines. TOWLER. J. M., and TOWLER, F. H. July 11, 1940, No. 11532. [Class 69 (ii)] [Also in Groups V and XXII] A hydraulic press suitable for use as a pressure casting-machine has its ram movement in both directions effected against a resilient resistance which decelerates the speed towards the end of each stroke and accelerates it at the beginning. In the press shown in Fig. 1 the space 8 in the fixed cylinder 4 is under constant liquid pressure from a reservoir 13, containing compressed air, via pipes 15a, 15, non-return valve 16, and pipe 15. When the spindle 22 of the control valve 14 is moved into the position shown in broken lines the space 10 is connected to exhaust 20 via a pipe 19 and the head 6, rods 7, and head 5 move to the right compressing springs 7a which decelerate the latter part of this movement. At the same time the valve 14 connects the high pressure supply 17 to the pipe 15b via the pipe 18 so that the final pressure of the head 5 is high. When the spindle 22 is moved into the position shown in full lines the space 10 is connected to high pressure, via pipes 17, 19 and the space 8 to the reservoir 13, via pipes 15b, 18, 23, and 15a, so that the heads 6, 5 move to the left with a motion accelerated at first by the springs 7a and decelerated at the end by the increased pressure in the reservoir 13. The machine may include a rod 29, for forcing molten metal or other material or inserting a nozzle into a mould M, which is moved to the left by high pressure fluid supplied to the space 26, via pipes 32, 17, when a spindle 21 is in the position shown and to the right by air or gas pressure, constantly applied by the reservoir 13 and a pipe 30 to the space 28, when the space 26 is connected to exhaust by moving the spindle 21 into the position shown in broken lines. In a modification the rod is operated by a double acting piston constantly urged to the right by liquid from the bottom of a separate reservoir, also containing compressed gas, and to the left by high pressure fluid from the valve 14 &c. In another modification the rod 29 is moved to the left by the head 5 engaging a flange 36, Fig. 3, thereon and to the right by fluid from a similar reservoir 35 admitted through a valve 37 positively opened by a piston 38 actuated by the high-pressure fluid from the valve 14, the valve 37 opening automatically, against the action of a spring to return the fluid to the reservoir on the plunger 33 moving to the left. In the press shown in Fig. 6 the head 5 is moved from position x to y, by previously compressed springs 46, by releasing the pressure in cylinders 45, fluid being admitted to the cylinder 43 by opening a valve 44. The stroke is completed and pressure applied to the work by closing the valve 44 and by admitting pressure fluid to the cylinder 43 opening the valve 14. The last part of the stroke compresses the springs further and this energy is used in the return stroke by reversing the functions of the cylinders 43, 45. In a modification, to make use of the acceleration due to gravity, the springs 46 are omitted and the press arranged vertically with the cylinder 43 uppermost.' If desired catches may be used in this modification to retain the head 5 in its highest position, instead of or in addition to the lifting cylinders 45. Specifications 499,509, [Group XXVIII], and 526,242 are referred to.