GB744108A - Improvements in or relating to regulating means for hydraulic presses for thermoplastic moulding materials - Google Patents

Abstract

744,108. Hydraulic moulding presses for thermoplastic materials. TELEFONAKTIEBOLAGET L. M. ERICSSON. Oct. 12, 1953 [Oct. 18, 1952], No. 28000/53. Class 87 (2). Automatic control by means of time relays: A platen 2 is moved, towards and from a fixed platen 1 by a haydraulic ram 3 controlled by a valve 5. This valve is operated manually to close the platens and thus begin an automatic cycle of operation. Another valve 8 controls the supply of heating and cooling media to mould parts 6, 7, this valve being controlled by a crank 26 driven by an electric motor 23 which rotates in one direction only, a half revolution at a time. The time between the end of the first half-revolution and the beginning of the second half-revolution is determined by two time relays 18, 20. Operation: (1) The press being open and the parts being in the position shown, the mould parts 6, 7 being heated by steam from pipe 37, the operator pulls down a gate 9, thereby rocking a lever 15 fulcrummed at 16. This movement of lever 15 reverses hydraulic valve 5, so that ram 3 is raised and the press is closed, and closes electrical contact 17. (2) Closing of contact 17 starts time relay 18, the circuit of which includes a normally closed contact 21; a pause ensues whilst the article is being moulded. (3) Relay 18 times out and moves contact 19 to the broken-line position, thereby (a) starting time relay 20 and (b) making a circuit, through closed contact 24, for a contactor 22. Contactor 22 closes to supply threephase current to motor 23, and the motor begins to turn clockwise, whereupon crank 26 on the motor shaft moves linkage 27, 28 to reverse valve 8, and cold water from pipe 38 passes through the moulds. When the crank begins to turn, the lower end of a link 29 connected to link 27 allows a contact 25 to close, and when the crank has turned through half a revolution the motor is stopped by the opening of contact 24 by the lower end of the link 29. The press remains closed whilst the moulds are being cooled. (4) Relay 20 times out and moves contact 21 to the open (broken-line) position, thereby breaking the circuit of relay 18, which allows contact 19 to move back to the full-line position, whereupon a circuit for contactor 22 is made through contacts 19 and 25. The motor then turns clockwise for a second half revolution until link 29 opens contact 25, as shown; during this half revolution the link 29 rises and rocks lever 15 counter-clockwise to the position shown, the valve 5 being thereby reversed to lower ram 3 and open the press, and the gate 9 being raised. The valve 5 may be such that when it is not actuated by the gate it assumes the pressopen position shown, a slight lifting movement of the gate sufficing to break the press cycle and restore the press to the initial position shown.