Mischer und Entlader fuer Urethan

1,196,485. Injection moulding machines. BRITISH UNITED SHOE MACHINERY CO. Ltd. 31 Aug., 1967 [1 Sept., 1966], No. 39773/67. Heading B5A. [Also in Division B1] Apparatus for mixing the constituents of a mixture and then dispensing the mixture comprises a cylinder 80 containing a piston 78 and mixing blades 156. The constituents (e.g. hydroxyl and isocyanate groups, for forming polyurethane foam) are stored in pressurized tanks 42 and are admitted in sequence through pneumatically opened valves (246, 278, Fig. 4, not shown), to raise the piston. The blades 156 mounted on a shaft 148 are rotated after introduction of the first constituent, and are both rotated and reciprocated along the cylinder after introduction of the second constituent, before an outlet valve 184 is opened and the piston is lowered by a pneumatic ram 72 to inject the mixture into a mould 286. The valves controlling the inlet, outlet and operation of the ram 72 are operated by microswitches (V2A, V3, VIA, Fig. 7, not shown) actuated by a cross-bar 82 on the piston-rod 76. The quantities of constituents admitted are determined by the positions of microswitches (V2A, V3) slidable on guides 92. These positions may be adjusted individually or together to preserve a constant ratio of constituents, by connecting them to a lever 112 pivoted at one end (114) and movable over a scale (118) at the other end. In operation the apparatus is stopped with the cross-bar contacting the first microswitch (V2A), i.e. after admission of the first constituent, so that any mixture remaining in the cylinder is diluted and prevented from curing. The outlet nozzle block 176 is porous and is supplied with lubricant when the outlet valve 184 opens, and compressed air, to clean it, when the first inlet valve opens, through passages 180, 182. The mixing blade shaft 148 is similarly lubricated through a passage 162 and an opening 161 in the bearing 146. The mixing blade shaft bearing, and the cylinder 80 also have cooling passages 158, 138 respectively.