Abstract: In a method for making objects of foamed, thermoplastic synthetic substance, air pressure is maintained in the mold while it and the contained plastic particles are heated, said air pressure being equal to or slightly higher than the pressure of the steam used for heating. When the mold has reached the saturated steam temperature, the air pressure is reduced to fuse the prefoamed synthetic particles together. Thereafter steam is introduced to displace the air in the mold and heat the synthetic particles to the temperature required for fusing or sintering.

Abstract: To make a molded article from expandable synthetic resin particles, especially polystyrene particles, the cooling of the individual mold wall portions is effected exclusively by evaporating condensate obtained from stream, advantageously condensate which accumulates in stream compartments on the exterior or back sides of the mold walls which was fed in for heating of the mold wall portions and fusing the synthetic resin particles. This evaporation of condensate is effected on the back surfaces of the mold wall portions facing the steam compartments because of a low pressure or suction produced in the steam compartments. The condensate is fed in hot at or just below the boiling temperature of the condensate. Surfaces of the mold wall portions facing the steam compartment have increased surface area by reason of spherical surface-area increasing elements which form constricted passages between a plurality of interior reservoir cavities and the outside steam compartment.

Abstract: An improved machine for the production of foamed plastic molded parts, including soft foam plastics, i.e. for processing particles without foaming capacity, and including the processing of greatly frothed plastic foam particles, i.e. particles with but little foaming capacity, is obtained in that a pressure equalization system is provided which creates virtually equal pressure conditions while the mold cavity is being filled, i.e. the same overpressure in the material supply line as in the mold cavity. This makes it possible to introduce the foam particles, already compressed in the material supply system, into the mold cavity in a continuous flow by means of an injector, with excess foam particles being blown back into a tank provided in the material supply system by the injector after the mold cavity is filled.