Apparatus for the heating and cooling of moulds for the production of plastic bodies

Claim 1

In a moulding apparatus, a combination comprising at least one mould having an outer and an inner wall spaced from each other and defining between said walls a space for the passage of a heat transfer fluid therethrough, at least said inner wall being a thin wall to assure quick heat transfer from said fluid to moulding material in a cavity defined by said inner wall and vice versa; fluid circuit means for circulating the fluid through said space and including a feed conduit communicating with said space for feeding fluid thereinto, a return conduit for discharging the fluid from said space and a pressure pump for pumping the fluid under pressure through said circuit means and said space; means in said fluid circuit means for changing the temperature of the fluid passing therethrough; a bypass conduit between said feed conduit and said return conduit; and regulating means cooperating with said bypass conduit for regulating the amount of fluid flowing therethrough so that only part of the fluid pumped by said pump will flow through said space to thereby avoid excessive pressure in said space which could lead to a deformation of at least said inner wall.