| 摘要 |
1,217,187. Controlling extrusion processes. BRITISH INSULATED CALLENDER'S CABLES Ltd. 9 Sept., 1969 [9 Sept., 1968], No. 42815/68. Heading B5A. In a method of controlling an extrusion process, a controlled feeding device 1, such as a weight or volume dispenser, feeds material to a reservoir 3 having a narrow glass neck 4 to display and amplify variations in the level of material in the reservoir, a signal representing the rate of feed is obtained from a transducer 15, a signal representing the line speed is obtained, e.g. from a capstan 18, and the rate of feed and/or the line speed are adjusted to maintain the level in the reservoir and the relationship between the signals constant such that the cross-sectional area of the extrudate remains substantially constant. The term, line speed, may apply to the speed at which a core being covered passes through the extruder or the speed at which extrudate is taken up, e.g. by a capstan. As shown, a volume dispenser 1 is associated with a sampler 7 which automatically calibrates the feed signal. The feed signal is applied to a voltmeter 17, previded with a set of changeable scales marked to indicate the correct line speed via a calibrating potentiometer 16. An indicator 19 shows the actual line speed. In a second embodiment, Fig. 2 (not shown), voltmeter 17 is replaced by an analogue/digital converter (20) which supplies a digital feed signal (A) to a display (21). A digital signal (B) representing the line speed is also fed to display (21) which shows signal (A), signal (B) or signal (A)/signal (B), the latter being proportional to the weight per unit length of material in the extrudate. In a third embodiment, Fig. 3 (not shown), the feed signal for potentiometer 16 is applied directly to a haul-off speed control (23) and the level in neck 4 is measured by a capacitance probe (24) which applies a signal to the speed controller (25) of feeding device motor 14 or alternatively to extrusion motor (26). Generally, reservoir 3 is provided with a vibrator 42 and overflow mechanism 9-11. The invention is particularly directed to the coating of cores with PVC.
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