| 摘要 |
1,127,507. Screw mixers. SEKISUI KAGAKU KOGYO K.K. 16 Nov., 1966 [30 Nov., 1965], No. 51417/66. Heading B1C. [Also in Division B5] In an extrusion moulding machine, air, moisture and volatiles are removed from plastics material in a vacuum chamber B" prior to the material entering a heatable barrel 16 which houses a screw plasticizer (not shown). The evacuation occurs via a pipe 6. The mouth of barrel 1 which houses a feed screw 2 is closed by a valve 12 urged thereagainst by a spring 21. When a predetermined pressure is built up with barrel 1 material forces valve 12 to open a predetermined amount and discharges into chamber B" in such a way that a material seal is maintained at the mouth of the barrel. The clearance between valve 12 and the barrel mouth is indicated on a dial 40. If a consolidated lump of material forms at the mouth, valve 12 is opened sufficiently to operate a cam switch 31, 32 which itself actuates apiston, cylinder arrangement 26, 38 to rapidly withdraw valve 12 and release the lump. Thereafter the withdrawal movement is reversed and initial operating conditions are re-established on actuation of limit switch 37 by a spring plate 36. In other embodiments the lump removal mechanism is dispensed with and valve 12 is hydraulically or pneumatically operated, Fig. 1 (not shown) spring operated, Fig. 2 (not shown), with spring tension adjustable by rotation of a sleeve (23), or is fixed relative to the vacuum chamber, Fig. 4 (not shown), with the valve comprising a flexible rubber, plastics or metal diaphragm (121). Various forms of the screw plasticizer are described, Figs. 6-10 (not shown), that of Figs. 9 and 10 being preferred and comprising two tapered screws (174) each having at their downstream ends mixing vanes (174'), and arranged such that the clearance between the screws and the barrel decreases downstream.
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