GB1422109A - Production of moulded foamed articles - Google Patents

Abstract

1422109 Heating & cooling moulds H ERLENBACH 28 Dec 1972 25025/75 Divided out of 1421183 Heading B5A [Also in Division F4] A single heat transfer medium for both heatting and cooling is circulated through a mould for making foam plastics articles, and the returning heat transfer medium is directed to the appropriate heating or cooling device 16, 17 by a temperature sensor 35 in the return path 15 which controls a valve 34 in a tank 18 for separating the hot from the cold medium. The mould comprises thin metal walls 1 which are sealed to thicker g.r.p. walls to form chambers 3 for heat transfer oil entering and returning through pipes 14, 15. Foamable plastics granules are injected by a device 7, and steam to foam the granules is injected through a needle valve 10. Oil for heating the mould is pumped from a heating tank 16 through pipe 14 and displaces cold oil from the previous cycle through pipe 15 and into a cooling tank 17 through the valve 34 which is open. When hot oil reaches the sensor 35, valve 34 is closed and the oil is directed through pipe 25 to tank 16 until this is full, whereupon the oil accumulates in the separating tank 18 which has an overflow 32 into tank 17. When cooling oil is pumped through the mould, valve 34 is opened to allow the accumulated warm oil and the returning cooling oil to pass directly into the cooling tank 17. In other embodiments (see Division F4) two heating tanks are connected in parallel, each with its own pump, one tank producing hotter oil for preheating the mould rapidly. The two heating tanks are either fed from the same separating tank through non-return valves 39, 45 (Fig. 2, not shown), or another separating tank on top of the first divides the two hot return flows (Fig. 3, not shown). The steam injection pipe 12 may have a heating jacket 55 (Fig. 4, not shown) through which oil is pumped by a circulation loop connected to tank 16 before the valve 23 controlling its outlet.