GB1514160A - Extrusion pelletising machines - Google Patents

Abstract

1514160 Cooling extrusion pelletizing apparatus FARREL BRIDGE LTD 7 July 1975 [17 Aug 1974] 28450/75 Divided out of 1514159 Heading B5A A pelletizing machine for thermosetting plastics, or thermoplastics material, comprises a screw extruder delivering the material through an annular array of extrusion passages 41 in a die plate 30, to be cut into pellets by radially extending blades 106 of knives 104, rotating in spring urged contact with the downstream face of the plate 30, and cooled by an air blast which also displaces the pellets outwardly away from the passages 41, and which is delivered on to each blade 106 through a shaft 82 to which the blades are mounted for their rotation. The air blast may be wet, or include a fine spray of water. For phenolic resin, the apparatus may be as described in Specification 1,514,159 in which the air is delivered through holes in the shaft. For polyvinylchloride, the apparatus of Figs. 2 and 3 is employed, in which the blades 106 of a pair of diametrically opposed knives 104 are each urged against the die face by a spring member 246, the shaft 82 rotating about a stationary shaft 64 which is loaded against a central area of the die plate 30 to maintain it flat against extrusion pressure. The cooling air is directed along each blade by a jet 248 which rotates with the shaft 82 and is supplied with air from a supply pipe 262 extending through the stationary shaft 64, the pellets which are outwardly displaced by the air being entrained and conducted to a cooling means, by high velocity air circulated along a spiral path between an air inlet 238 and an outlet 284 which are axially offset along a surrounding casing 23. Pipes 278 also extend through the shaft 64, for delivering steam to heat the hollow interior of a conical die torpedo 46. The shaft 82 rotates about an axis eccentric with respect to the annular paths of the holes 41, which are radially offset, so that the blades cut only one pellet at a time, and sequential pellets at different positions along their length to avoid uneven wear of the blades.