Patent GB-1246701-A (GB)
Title: Method of moulding powdered or granular material
Inventor: BENT JOHN
IPC: B28B3/02
Filed: 1969-01-16
Abstract: 1,246,701. Feeding powdered material to presses. CARBORUNDUM CO. Ltd. 23 Dec., 1969 [16 Jan., 1969; 28 May, 1969], Nos. 2536/69 and 26874/69. Heading B5A. A deeply recessed and relatively thin article, e.g. a cap or dish, plate or saucer, is moulded from powdered or granular material, e.g. of ceramic, metal, plastics, or composites, which is distributed in layers 2, Fig. 1, longitudinally spaced apart on an elastomeric conveyer belt 1 which is intermittently advanced to position each layer 2 above a female die 3 against which it is moulded upon descent of an upper male die 5. In the Fig. 1 embodiment, earthenware material, which has been produced by blunging, filter pressing, and de-flocculation, followed by spray drying, of 70% solids content in water, to 7-8% moisture content, is distributed through the intermittently opened adjustable gates of a hopper (not shown), on to the advancing rubber belt 1 to form five layers 2 laterally spaced thereacross, each of which is advanced between co-operating dies 3 and 5 defining the shape of a rectangular dish. The die 3 is provided with six holes 4, five whereof function as vents and through one, 4a, whereof pressurized air is admitted to support the belt 1 and layer 2, prior to descent of the die 5 when the belt 1 is first clamped around the die 3 by a sprung frame 6, whereafter it is additionally engaged around the cavity periphery by a projecting rim extending around the die 5 prior to full compression being exerted by the die 5 which, together with the die 3, is silicone lubricated. After retraction of the die 5, the moulded dishes are advanced on the belt 1 from which they are led by further conveyers through drying, towing, glazing, drying and firing stage. The process is automatically controlled by means of time and limit switches, and motorized valves. Alternatively, a separate belt 1 may be employed for each cavity  of a multi-cavity die unit; the belts may be patterned, e.g. with woven designs, or embossed, or individual patterned rubber sheets may be located thereon; with thin articles, a thinner rubber sheet may be located on a talc lubricated belt 1. With articles of non-uniform thickness, e.g. a plate having an annular rim, a non-uniform layer 2 is obtained by deposition either on to an appropriately configured belt 1, or on to a thin belt, e.g. of P.V.C., which is deformed by vacuum applied therebeneath. Finished articles having recesses and/or projections at certain location may also be produced by the further moulding of a moulding from a uniform thickness layer, having a greater mass at these locations which has been obtained either by precompressing the layer to form depressions to which further material is added, or precompressing parts only of the layer from the uncompressed parts of which excess material is removed. To obtain articles with a smooth finish, the belt, e.g. of polyvinylchloride, is not of greater thickness than the particle size of the material and is held tensioned during the depositing and moulding. Vacuum may be applied beneath the belt during moulding and may be actuated by an adjustable control on the upper press platen.