Patent GB-1260652-A (GB)
Title: Improvements in or relating to machines adapted for use in the manufacture of ceramic ware
Inventor: BRADSHAW ARTHUR
IPC: B28B7/42
Filed: 1969-03-07
Abstract: 1,260,652. Drying moist clay pieces. SERVICE (ENGS.) Ltd. 27 March, 1969 [28 Dec., 1967; 7 March, 1969], Nos. 58821/67 and 12069/69. Heading F4G. [Also in Division C1] Shaped moist clay pieces W are dried (while on rotating moulds M and air is passing over them) by subjecting them to the influence of a high-frequency electric field and then to radiant heat to obtain release of the clay pieces W from the moulds M, and the clay pieces W after removal from the moulds M are further dried. Uniform pieces of clay are extruded, cut and loaded at a station S1 (Fig. 2) by a machine 30 (as described in Specification 1,246,613) on to empty moulds M carried by an intermittently-operated upper endless conveyer 22, are shaped at station S2 by a roller tool machine 32, and pass into a heat-insulated drying cabinet 34. The clay pieces initially pass through the rear upper chambers 62 and 63 which contain three electrode assemblies 220 connected to highfrequency generators (70 MHz), then through the upper chamber 64 which contains radiant lamp assemblies 272 to a transfer station S4 where a transfer mechanism delivers the dried clay pieces W from the moulds M to perforated trays 28 carried by an intermittently-operated lower endless conveyer 24, the clay pieces W are further dried by passage through lower chambers 66 and 68 through which heated air is circulated, and are unloaded at station S3 by automatic means (not shown). After the transfer station S4 the empty moulds M on the upper conveyer 22 pass through the front of the upper chamber 62 and return to station S1. Air is drawn into the upper chambers 62 and 64 from the open end 43 and the chamber 70 of the cabinet 34 and is exhausted through ducts 322. Upper conveyer 22 comprises an endless chain 92 (Figs. 4, 8 and 12) driven step-by-step at intervals by a motor 102 and connected to non- ferrous carriages 84 mounted on castors 86 running on rails 80 and 82, each plaster mould M resting on a ring 114 accommodated in a hole in the carriage 84. Rotation of moulds M is effected as they pass along the straight portions of the conveyer 22 in the upper chambers 62 and 64, by means of rubber belts 124 and 126 which are supported at intervals therealong by pulleys 128 so as to engage with and raise the rings 114 (carrying the moulds M) from the carriages 84, and which are driven continuously in opposite directions by electric motors 136 so as to rotate the raised rings 114 (at 40 r.p.m.). Lower conveyer 24 comprises an endless chain 150 (Figs. 4 and 8) driven by the motor 102 and connected to the trays 28 which are mounted on castors 144 running on rails 142 and a bar 147 (Fig. 4), each tray 28 having a central aperture 28 (Fig. 8) and an entry slot. Transfer mechanism at station S4 comprises a yoke 178 (Fig. 8) which is swung by means of a motor 162, cranks 166 and 168 and gear wheels 172 and 174 between the full and dashed line positions to deliver a piece of ware W from the mould M to the tray 28. The yoke 178 adjustably carries a pneumatic cylinder 194 whose piston rod 196 carries a rubber cup 200 to which suction may be applied via a flexible hose 204 in order to grip the wave W. Loading machine 30 (as described in Specification 1,246,613) lifts the ring 114 from the carriage 84 to receive the piece of clay which is subjected to axial pressure and peripherally trimmed. Each electrode assembly 220 (Fig. 12) comprises electrodes 222 each mounted on two screwthreaded insulating rods 224 engaging screwthreaded sleeves 226 having bevel gears 232 meshing with bevel gears 234 on a shaft 236 (for each electrode 222). Each shaft 236 is individually rotatable by means of a knob 240 and a flexible shaft 238, to raise or lower the electrode 222 so that it lies about 9/16 inch above the mould surface, viz. less than 1À5 cm. from the clay. Alternate electrodes 222 are connected to opposite output terminals of the high-frequency generator via plates 242 and a tuning means 242. Insulating rods 244 and spacers 246 form a framework locating the electrodes, the framework being clamped by a knob 256. Each radiant lamp assembly 272 (Fig. 4) comprises four lamps 270 adjustably mounted in pairs on a cross-head 276 which is vertically adjustable by means of a knob 288. Heated air circulation (Fig. 4) in the lower chambers 66 and 68 is effected by fans on the roof 46 of the cabinet which draw air up through ducts (not shown) from the chambers 66 and 68 past gas-fired air heating units and blows air down through a central duct 304 (in each of chambers 66 and 68) leading via ducts 306 to ducts 300 which have transverse outlet slots. Part of the circulating air is exhausted to atmosphere via ducts 322 and fans. Control of the apparatus is accomplished by microswitches at the loading machine 30, at the roller-tool shaping machine 32 and at the transfer station S4. Drying conditions.-Pieces of ware W having an initial water content of 21-23% by weight (on a wet basis) reach about 140‹ F. in the electric field and the hot air in the chambers 66 and 68 is at about 375‹ F., and reach a final water content of 5% or less.