GB1493559A - Extruder heads - Google Patents

Abstract

1493559 Extrusion assembly R W DYASON 14 April 1976 15285/76 Heading B5A Apparatus for extruding expanded farinaceous material comprises a die assembly comprises having a plurality of circularly arranged extrusion outlet passages 37 extending through a die plate 29, to which the material to be extruded is delivered by rotation of one of concentric male and female augers 22, 12, via an annular passage 26 defined between an annular ring 25 abutting the plate 29 and a boss 33 of the plate 29 which projects upstream within the ring 25, the passage 26 discharging into an expansion chamber comprising a recess 27 in the ring 25 and whose radially outermost extent is not greater than the circular path defined by the radially outermost parts of the passages 37, so that streamline flow of the material is effected between the recess 27 and the passages 37. The passages 37 may be circular, or flat, and the material expands on leaving the passages 37, to be cut by a rotating knife 41, which may be spring loaded against the plate. The die plate 29 and ring 25 are detachably mounted for cleaning, and the outlet passages 37 may comprise inserts which are replaceable upon wear, or to define different shape passages, or are replaceable by inserts not having passages to vary the extrusion pressure. In the embodiment, the female auger 12 is stationary and replaceably located in a barrel 11 at screws 14 and is tapered to effect an increasing compression on the material in the downstream direction and the male auger 22 is also replaceably mounted. The upstream surface of the boss 33 comprises radial saw tooth formations which assist flow of material between the auger 22 and passage 26 and effect a breaker action. The material is heated by the compression of the augers, and by passage 26, but the barrel 11 may also have heating means and temperature sensors may be located within the barrel or die. The size of recess 27 can be increased by a recess in the die plate 29, around the boss 33 which may be detachable from the remainder of the plate 29. The material is delivered to the inlet 20 of the extruder in finely ground form, via a screw conveyer and hoppers, and the material cut from die may be removed on a conveyer.