Patent GB-598544-A (GB)
Title: Improvements in or relating to injection pressure casting machines
IPC: B29C45/53
Filed: 1944-10-18
Abstract: 598,544. Injection-moulding machines. ARNOLD, J. C. (Lester Engineering Co.). Oct. 18, 1944, No. 20173. [Class 87 (ii)] [Also in Groups XXII and XXIX] A fluid-operated injection-moulding machine comprises high- and low-pressure pumps 31, 30 connected by pipes 45, 36, 43, 61 to the injection cylinder 5, pressure responsive means 38 connected to said pipes 36, 43 and actuated by variations of pressure in the pipe 45 to disconnect the pump 30, means for controlling the rate of flow to the cylinder 5, and means for rendering this control inoperative when the pump 30 is disconnected. Fig. 2 shows the control system just before beginning of operations, the motor 17 driving the pumps 30, 31. A valve 48 is first operated by its solenoid to cause the piston in the cylinder 13 to close the die. As this piston reaches the end of its stroke the pressure in the pipe 45 increases and acts, via a pipe 91, valve 87, and pipe 92, on the lower face of a piston 39 and thus raises it, against the action of a spring 85 set to 300 lbs. per square inch, and thus open the space 37 to exhaust 41, 42, 35. The one-way valve closes automatically and the pump 31 alone applies its high pressure to clamp the die cylinder. The switch 104 is then closed by hand to energise solenoids 66, 90 and reverse the valves 63, 87, the former causing the valve 55 to move to the right and apply the pressure in the pipe 45 to the upper, instead of the lower face of the piston in the cylinder 5 and thus start the injection stroke. The reversing of the valve 87 releases the pressure in the pipe 92<1>, thus allowing a valve 71 to fall and connect the pipes 69, 74 and applies the pressure in the pipe 91 to the upper face of the piston 39, thus closing the valve and keeping it closed so that both pumps supply the fluid for the injection stroke in spite of slight variations of pressure in the pipe 61 but when this builds up at the end of the stroke to say 1,000 lbs. per square inch, it acts, through a pipe 68, on a piston 97 to open a switch 98 against the action of an adjustable spring 95. This de-energises the solenoid 90 and allows the valve 87 to return to the position shown thus allowing the pressure in the pipe 45 to act, through the pipes 91, 92 to raise the piston 39 and cause the pump 31 alone to supply its high pressure to the injection plunger. During the major portions of the injection stroke, the valve 87 being in the left hand position and the pipes 92, 92' open to exhaust, the valve 71 is in its lowest position and some of the fluid supplied to the pipe 61 flows through the pipe 68, valve 71, pipe 74, valve 77, and adjustable throttle 78 to exhaust 42. The pressures on either side of the throttle 78 act on the two sides of the floating piston 81 to open the valve 77 more when the pressure in the pipe 61 rises and close it when it falls thus keeping this pressure substantially constant. But, when the final big increase occurs and the solenoid 90 is de-energised, the pressure in the pipe 92 lifts the valve 71 to cut out this regulator. The switch 104 is then opened to de-energise the solenoid 66, allow the valve 63 to move to the left and thus move the valve 55 to the left and supply fluid to the lower side of the piston in the cylinder 5. The pipe 61, being connected to exhaust at the same time, allows the piston 97 to move to the left and close the switch 98. The valves 48, 51 are then operated to open the die and eject the casting, these movements being effected by the fluid supplied by the pumps 30 31, the valve 38 acting, when resistance rises, to throw whole load on the pump 31 as before.