GB620652A - Improvements in or relating to injection-moulding or extrusion apparatus - Google Patents

Abstract

620,652. Injection-moulding and extrusion machines. STEVENS, A. H. (Chrysler Corporation). Dec. 1, 1944, No. 29095/47. Divided out of 605,867. [Class 87 (ii)] [Also in Group XXX] The obturating-discs 30, 31, which mesh with and are driven by the impelling screw 21 and prevent material turning with the screw, are disposed in chambers 22, 23 communicating with the cylinder bore 16 by slots 24, 25 in the cylinder wall. The distance between the upper edge A of the slots and the inlet end B of the cylinder bore is such as to accommodate at least one complete turn of the screw, whereby when material which has been carried between the teeth of the discs 30, 31 into the chambers 22, 23 is returned to the cylinder bore (just below the edges A), the material will not escape from the bore. Grooves 100 in the bore prevent material turning in the thread at the entrance to the bore. The chambers are formed in part by the slots 24, 25 ,and in part by caps 28, 29. The screw has an extension 52 which acts as a spreader, and the lower end of the extension carries blades 53 which contact the walls of the cylinder bore and centralize the screw. Heating elements 50, 51 surround the lower part of the cylinder. Disposed in the nozzle 14 is a rotatable valve 45 having a discharge orifice extending therethrough. The screw is turned by an electric motor 54 through pinion gearing and carries a gear 92 which drives a feed drum 82 disposed at the bottom of a hopper 79. A vertically-adjustable gate 94 controls the feed from the hopper into the cylinder. In a modification, (Fig. 4 not shown), suitable for the injectionmoulding of rubber, the screw-thread extends to the bottom of the cylinder and the lower end of the screw shaft is formed as a cone which periodically seats on the nozzle to prevent egress of the rubber, this seating being effected by reverse rotation of the screw and by a spring against which the screw floats.