| 摘要 |
A plastics extruder in operative association with a control arrangement is disclosed. The plastics extruder includes a screw extruder, a screen downstream of the screw extruder, a throttle located between the screw extruder and the screen, a moulding tool downstream of the screen, and a melt index measuring device. The measuring device includes a metering pump whose rotational speed is controllable and which is provided with a rotational speed indicator, a measuring nozzle disposed in a sample flow channel, and pressure and temperature sensors connected to the sample flow channel directly upstream of the inlet of the measuring nozzle. The sample flow channel is adapted to be located downstream of the screen pack and upstream of the moulding tool. For the purpose of regulating the viscosity of the plastics material melted in the screw extruder, the throttle cross-section is variable by a servomotor connected to the output of a programmable two-coordinate controller. The characteristic of the controller provides a desired value output and can be predetermined as a temperature-pressure characteristic when the metering pump is operated with constant delivery, or as a temperature-delivery characteristic when the metering pump is operated with a constant pressure drop via the measuring nozzle while the temperature sensor is connected to one of two actual value inputs of the two coordinate controller. Either the pressure sensor or the rotational speed indicator is connected to the second actual value input. |
