| 摘要 |
A method is described in which the operative condition of the cooling sections of a slot die for making flat films of thermoplastic material, or of an annular die of a blow molding extruder for making tubular films from synthetic thermoplastics, is tested. The cooling sections are provided with lines for supplying and discharging cooling air and the lines for supplying cooling air are connected, as required, to a central cooling air feed line, which is under superatmospheric pressure, by solenoid valves controlled by an electronic computer. In one embodiment of the invention, a testing program is performed in which the cooling air feed line is disconnected by a shut-off valve from the branch lines leading to respective solenoid valves when the latter are closed. A pressure detector disposed in the cooling air feed line is then used to measure the pressure and the pressure drop which occurs in the cooling air feed line upon the opening of the solenoid valve associated with the first cooling section that is to be tested. An error signal is generated when the pressure and the measured pressure drop do not correspond to values which are typically obtained in case of proper operations of the cooling air feed line and of the cooling section being tested. All cooling sections are subsequently tested, in succession, by closing all solenoid valves and the shut-off valve and opening only the solenoid valve associated with the cooling section to be tested during the testing interval.
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