| 摘要 |
A screw-type extruder for plastic material has a cylindrical housing axially divided into two externally heated compartments provided at their upstream ends with a hopper and a venting aperture, respectively; at its downstream end each compartment terminates in a mobile housing section for adjustment of the back pressure prevailing therein and, consequently, of the flow rate of plastic mass discharged from the compartment. To equalize the two flow rates, a pair of hydraulic jacks serving to shift these mobile sections are controlled by respective regulators which respond to associated function generators and to the corresponding back pressure as measured just ahead of these mobile sections; the first function generator receives at its input the back pressure of the second compartment whereas the second function generator is adjusted to deliver a constant output dependent upon the desired flow rate at the extrusion nozzle and upon the speed of rotation of the screw.
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