Patent GB-729048-A (GB)
Title: Improvements in injection (plastic) moulding machines
IPC: B29C45/38
Filed: 1952-06-25
Abstract: 729,048. Injection-moulding machines. PIERWOOD PLASTICS, Ltd. June 25, 1952 [July 30, 1951], No. 16037/52. Class 87 (2). An injection moulding machine of the type having a die and mechanism to close and open the die and having means to inject plastic material into the closed die is provided with means to stop the machine at the completion of each moulding operation and ' means actuated by the machine to cause each article moulded by the machine to be removed from the die when opened and to actuate means which will start the machine again when each article has been removed. A shaft 22, carrying a crank 34 and cams 23, 25, 63, 38 is driven by a motor 17 through a friction roller and disc 18, 19. The motor is slidably mounted and the position of the roller 18 relative radially to the dies 19 may therefore be moved and thus the time for one cycle of operation of the machine may be adjusted. When a moulding operation is nearly complete the crank 34, through a pitman 33 and crosshead 32, raises a plate 27, pivoted at 28, into position for receiving a moulded article after ejection from the machine. As the plate 27 rises it opens a switch 35 in the motor circuit, but the motor continues to operate because a switch 36 in parallel with the switch 35 is still closed. The opening and closing of the die are effected by a locking member 14 which is hydraulically operated under the control of the cam 23. The cam 10 is under the control of the cam 25. At the end of the moulding operation the die is opened and the cam 38 opens the switch 36 to stop the motor. As the member 14 moves back to open the die a trip plate 46 moves with it and frees an extension 45 of an arm 42, so allowing this arm to fall. The arm 42 carries, between terminal bars 40, an electrically heated resistance wire 39, and if the moulded article is hanging to the die by a sprue the heated wire will sever it. A trip plate 55 moves similarly to free an extension 54 of an arm 52 which carries an ejector 53 and is timed to fall after the arm 42 so that the ejector clears the moulded article after the sprue has been cut. The article falls on the plate 27, which is balanced by the weight 29 whose position is adjusted so that the plate will tip under a predetermined weight, and as the plate tips it discharges the article into a shoot'31 and is held down by a magnet 37 until the crank 34 raises it again; also it closes the switch 35. The arm 42 is fixed to an outer member 43 of a compound shaft, and the arm 52 is fixed to an inner member 51 of the same shaft, the member 43 carrying also a crank 58 and the member 51 a crank 59. A plate 60 is fixed to the crank 58 and extends across the crank 59. A push rod 62 is actuated by the cam 63 and engages the plate 60 to restore the arms 42, 52 to. their raised positions at the correct time. The maximum fall of the arms 42 and .52 is limited by the .plate 60 meeting a stop plate 61. A drip tray may be fitted to catch oil or water leaking from the operative components of the machine, and a float in the tray may be arranged to operate a switch to stop the motor in the event of oil or water leakage.