| 摘要 |
1279663 Extruder Screw MIDLAND-ROSS CORP 6 Nov 1969 [14 Feb 1969] 54480/69 Heading B5A The efficiency of melting of particulate thermoplastics material e.g. polyvinyl chloride, within the heated barrel of a screw extruder, is improved by utilizing, in the melting region of the screw, the displacing action of the interior barrel surface to constantly displace material, melted in contact therewith, from a screw channel 10 of progressively decreasing volume effected by constantly decreasing depth, over an intervening land 12 into an adjacent channel 11 of constantly increasing volume. The screw feed section comprises a single channel 8 of constant root diameter and pitch, connected to the melting region by a short transition region wherein the flight width 7 is increased to decrease the width of the channel over a portion 10a to that of the portion 10 which remains constant throughout the melting region as the depth thereof decreasss. The adjacent channel 11 of progressively increasing depth is commenced at the melting zone in the widened flight at 14, to be defined between a trailing flight portion 16 and a leading flight portion 12 of lesser height providing the intervening land over which the molten material is displaced. The trailing edge 6 of the flight is of constant pitch throughout the screw. The channel 11 is merged over a short transition section, to a metering section 11b of decreased depth and increased width. The barrel is heated either by electric strip heaters, or by fluid jackets. The feed section may alternatively comprise a channel of the same width as channel 10, but of decreasing depth theretowards.
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