Temp. control of rotationally moulded hollow articles - using recycling line with programme controlled mixer servocontrolled to temp. in heating fluid line

摘要

A device for making hollow thermoplastic objects by rotary casting in a mould revolving about two axes utilises a common heating and/or cooling circuit comprising, on the feed side, a 3-way valve or opt. supply of hot or cold oil, and a circulating pump and, on the discharge side another pump or venturi nozzle and a second 3-way valve. This valve arrangement enables either hot or cold oil to be supplied to the hollow wall chambers of the mould. In addn. a mixing line leads from any point in the return line situated between the mould and the 3-way valve to a point in the feed line between the 3-way valve to a point in the feed line between the 3-way valve and circulating pump; this mixing line contains a mixing valve; a temp. sensor at any point in the feed line between the connection of this mixing line and the mould sends signals to a time pattern emitter, pref. operating on the punched tape principle, so that the time plan can regulate the mixing valve and thus the cross flow between the return and feed lines. The control from the emitter to the mixing valve is pref. by pneumatic pulses.