Patent GB-400280-A (GB)
Title: Method of moulding materials
IPC: B28B13/02
Filed: 1932-04-16
Abstract: 400,280. Moulding powdered substances. TRIGGS, W. W., 57, Lincoln's Inn Fields, London.-(Champion Spark Plug Co.; Upton Avenue, Toledo, Ohio, U.S.A.) April 16, 1932, No. 32709. Divided on 400,243. [Class 87 (ii).] A method of moulding powdered or granular material consists in charging the mould by connecting it to a storage vessel and subjecting the material in the vessel to gas under pressure to cause it to be permeated with compressed gas so that it will flow readily without clogging, and afterwards subjecting the material in the charged mould to high pressure. The interior of the mould may be subjected to vacuum during the filling operation to assist the charging operation. In one method, as applied to the making of a sparking-plug core, an airtight powder-container 41, Fig. 1, connected by pipe 42 to a source of compressed air, is furnished with raised perforated bosses 43 covered by perforated caps 45 arranged so that the powder in being forced into the tubes 47 has to take a tortuous course. A two-part mould 52, 53 is arranged under the tubes 47 so as to be filled with powder, the air escaping at vents surrounding the tubes 47 during the filling process. After filling, the mould is removed from the container, a cover-plate is applied, and compressed air admitted by pipe 60 to pass through the perforated walls 58 and apply pressure to the exterior of the flexible walls 57 of the mould, thus effecting a final compression of the material. It is stated that the powder in the container is permeated readily by the compressed air, so that a mixture of powder and air is always delivered, thus preventing clogging. In moulding powders of a floury nature, a hopper 84, Fig. 3, is provided with a measuring chamber between two movable gates 85, 88, the capacity of which can be adjusted by telescoping the parts 86, 87. Compressed air, admitted to an annular chamber 89 with downwardly-projecting nozzles, forces the material down the pipe 82 into the mould 79, the escaping air passing through pipe 96 and being re-admitted to the material at 97. A second ring 91 of air-jets assists the movement and prevents clogging. When the mould has been charged, a top-forming die 106, Fig. 4, is placed thereon and fixed by lugs 107 passing under lugs 108 on the surrounding casing 75. The contents are subjected to a vacuum applied through the pipe 118 and perforated plate 116 while the flexible mould walls 79 are compressed by air admitted by pips 105 and passing through perforated casing 76. Prior to filling, the walls 79 are drawn into contact with the casing 76 by a vacuum applied through the pipe 105. The mould in Fig. 4 is more especially for forming a high tension insulator. Another mould, shown in Fig. 5, forming a blank for a sparking-plug core, comprises a flexible wall 131 mounted inside a perforated casing 121 carried in turn by an outer casing 120. A cap 122, having lugs 123 held tightly under lugs 124 on the casing 120 by means of bolts 125, serves to support a filling-tube or the members shown for forming the internal screw thread 154. By connecting the pipe 144 to vacuum, the flexible wall 131 is drawn outwards into contact with the casing 121. On connecting the pipe 145 to vacuum, the mould can then be filled through the filling tube from the compressed material in the storage hopper as before. When the mould is filled, the tube is removed and the member 147 fitted on to the cap, engaging thereunder by means of lugs 149. The member 147 carries the screwed plunger rod 153 which has a play-permitting pin-andslot connection 155 with the member 152 screwed into the main member. A core rod 157 then is forced right through the material. Vacuum is then re-applied through pipe 145 and pressure through 144 to compress the flexible walls 131. The residual air causes slight expansion of the moulded material when the pressure is relieved and during this movement the thread forming plunger moves in its pin-and-slot in unison with the material, to avoid stripping of the screw threads. The threads 154 and 160 are of the same pitch so that the plunger 153 and member 152 can be removed as a unit. A limited longitudinal movement of the plunger 133 forming the base of the mould also is provided for. Specifications 400,243 and 400,281 are referred to.