GB695327A - Improvements in or relating to the manufacture of shaped products of plastic material - Google Patents

Abstract

695,327. Moulding bricks, tiles, pipes, &c. FAWCETT, Ltd., T. C., DIXON, P. J., and WALKER, L. Dec. 5, 1951 [Sept. 26, 1950], No. 2345/50. Class 87 (ii). Products such as bricks, tiles and pipes are formed by transferring measured quantities of uniformly moistened plastic material directly from an evacuated space containing a supply of the material into a further evacuated space, applying pressure to the transferred material to compact it to the required size and shape within the further evacuated space and removing the compacted material that has been thus detached from the supply. leaving the supply still evacuated. The invention is especially concerned with the moulding of material produced as described in Specification 587,698, according to which dry granular material is formed as a semi-plastic by introducing it into a vacuum chamber into which liquid is also sprayed. In the apparatus shown in Fig. 1, 10 is the vacuum chamber and 9 a shoot through which material is transferred to a hopper 8, 14 being a further vacuum connection which may be provided. Mould cavities 2 are formed in a casting 3 having continuous flanges 4 and carried by a horizontal rotatable table 1. A plate 5 in the mould is lowered by the descent of a plunger 6 when the mould is in register with the hopper, and the material is compacted in the mould by the action of a propeller 12, 11 being mixing blades. The continued rotation of the table 1 causes the top of the material in the mould to be scraped level, after which it is further consolidated by a piston (not shown) acting on the top of the material and the moulded article is then ejected by upward movement of the plunger 6. Seals 13 fitting the flanges 4 and a gland 7 surrounding the plunger 6 are fitted to prevent entrance of air. In Fig. 2 a drum 20, having on its periphery moulding cavities 21, is rotated intermittently to bring the cavities through an aperture in the wall 22 of an evacuated hopper 23, with sealing strips 24 to prevent ingress of air. A ram 25, movable horizontally through a gland 26, is first withdrawn to allow material to fall from the hopper 23 into a, measuring chamber 28 capable of holding rather more material than is required, and the ram is then advanced to push the material into the cavity 21 opposite, any surplus being returned to the hopper by a passage 29 in the ram. The charged cavity is carried round to the position B, where the charge is ejected sideways and may be finally consolidated in a separate press. In Fig. 3, a shoot 33 delivers material from an evacuated chamber (not shown) to an evacuated hopper 32 with an outlet to a cylinder 35, in which are pistons 36, 37 with their faces together and sealing the outlet. The pistons move apart to the Fig. 4 position and form between them an evacuated cavity 40 into which material falls from the hopper, and they then move in the same direction to transfer the charge of material from beneath the hopper and the piston 37 moves towards the piston 36 to compress the charge, when further piston movement brings the compacted brick opposite an opening 42, Fig. 7, through which it is discharged. The faces of the pistons need not be plane, but of complementary shapes. For perforated bricks, supplementary plungers may operate through a piston face, or pipes may be formed by a large plunger projected from one or both pistons. Figs. 9, 11 show an arrangement with a movable feed box 57. Material from an evacuated chamber descends through a shoot 50 to a feed hopper 51 situated in an evacuated chamber 53 and into the feed box 57, Fig. 9, which is open at the top and bottom. The feed box then moves over the mould cavity formed by the descent of a bottom ram 63 and the charge drops into the cavity, and the feed box pushes a previously formed brick 60 into a further part 62 of the chamber 53. As the feed box returns it takes back any surplus material and levels the charge, which is then compacted by the descent of a top ram 69. When the ram 69 rises again the bottom ram 63 also rises and pushes the brick out of the mould cavity ready for removal; the ram 69 may again be operated to consolidate the brick. Seals are fitted to prevent ingress of air at 56, 64, 70 and sealing doors 65, 66 shut off the space 62, one being closed when the other is open.