Patent GB-1382701-A (GB)
Title: Face cutting apparatus for forming pellets
IPC: B29C48/05
Filed: 1972-03-30
Abstract: 1382701 Extrusion granulating die WELDING ENGS Inc 30 March 1972 [2 April 1971] 14921/72 Heading B5A [Also in Division G3] Thermoplastic material is extruded by a screw 14 through granulating means comprising radially inwardly directed orifices 17 of a cylindrical die means 16, from the inner outlet face of which granules are cut by the cutting edges of blades 22 arranged helically around a rotating member 20 to provide helical channels along which the granules are discharged to a collecting member 36, by granule treatment fluid delivered by pressure and the impelling action of the blades 22. The treatment fluid may comprise air drawn from atmosphere along the rotating member (20) from a blower (71), Fig. 6 (not shown), exhausting into the collecting chamber (36<SP>1</SP>). The treatment fluid may alternatively be water, may be a heating or cooling fluid, may function to remove volatiles from the granules, or may comprise a reducing or inert gas when the granules are oxidation sensitive. The orifices 17 are defined through a pair of concentric cylinders 43, 44, the inner 44 of which is fixed to the collecting chamber 36 and is automatically axially displaceable with respect to the outer 44, in response to extrusion pressure at the end of screw 14, to adjust the relative alignment between the orifices in the cylinders 43, 44 to maintain a constant extrusion pressure. For this purpose, the extrusion pressure is sensed by a transducer 60, the signal from which is proportionally converted into a control for a regulator 62 from which the output is applied to a pneumatic valve 63, which controls air pressure supplied to an hydraulic fluid accumulator 64 in direct proportion to the sensed extrusion pressure. The hydraulic pressure in accumulator 64 acts in a fluid pressure chamber 52 defined between opposed shoulders, e.g. 47, of the collecting chamber 36 and a sealingly engaging member 50 fixed with the extruder barrel 12, an increase in extrusion pressure and the hydraulic pressure of accumulator 64 displacing the collecting chamber 36, against the action of a spring 55 and together with the cylinder 44, towards the cylinder 43, to a limit determined by the abutment of a collecting chamber abutment 46 with the end of cylinder 43 when the orifices 17 in each cylinder are in alignment. Indicia 69 are provided, on one of members 49 mounting the members 50 to the barrel 12, to indicate the degree of alignment of the orifices 17 effected in the above manner. The alignment of the orifices 17 circumferentially of the cylinders 43, 44 is ensured by a pin 57 locating through a handle 56, attached to the chamber 36, into a flange 58 fixed with respect to the barrel 12. On removal of the pin 57, the relative aligment of the orifices 17 circumferentially of the cylinders 43, 44 may be manually effected from the handle 56, e.g. on commencing or halting extrusion, by rotation of the chamber 36 into a position in which the handle 56 may be locked by a bolt extending from the handle 56 through an elongate aperture in the flange 58. The orifice alignment in this respect is indicated by indicia on the flange 58. The cylinders 43, 44 are enclosed in a housing 19, provided with channels 38 for the circulation of heating and cooling fluid, and through which the pressurized treatment fluid is admitted at 35. A single extruder may discharge to each of a pair of the above described granulating means, Fig. 7 (not shown).