A machine for molding plastic articles from foamed granules finely divided foamable plastic impregnated with a blowing agent.

摘要

1,158,181. Foamed articles. GROWN MACHINE & TOOL CO. 25 Nov., 1966 [26 Nov., 1965 (2)], No. 52792/66. Heading B5A. Foamed plastics articles, e.g. of polystyrene, are produced from finely-divided beads thereof impregnated with a blowing agent, e.g. butane, by a process in which certain quantities of the beads are partially foamed on a batch basis to a predetermined density, before supplying them to the moulds in which they are immediately further expanded, the rate of supply and consumption thereof in the mould being so related that the partially foamed beads are used immediately after prefoaming before they can change in density or otherwise deteriorate. In an embodiment described, beads are supplied from a hopper 18 to prefoamer 22 via tube 20, and then to the prefoam hopper 26 via tube 24 and then to the moulds 30 via line 28. The prefoamer (also Figs. 5-9, not shown) includes a metering device 120, stirrer 109, air supply means (Fig. 8, not shown) to effect a swirl of the beads therein, a discharge port (138) controlled by a photo-cell 158 connected to tube 24, cross-bars (164) to break up agglomerates and electrodes (166) to reduce agglomeration caused by electrostatic attraction. The prefoam hopper 26 (also Fig. 4, not shown) comprises a main cylindrical portion (42) and conical portion (44) having leads (48) to two moulds, the hopper also containing a sieve device (50) comprising a cylindrical portion (52) and conical screen (56) around which there is a spiral wire (58) to break up agglomerates due to electrostatic attraction. There may be two photo-electric sensing mechanisms 62, 64 which operate the metering device 120.