US Patent 7150181 Apparatus for testing the purity of plastic melts

In a device for testing the purity of a plastic melt by plasticizing a melt and pressing a defined quantity of the melt through a screen with a defined size and porosity while simultaneously measuring the melt pressure, a changeover valve with two positions is provided—namely a working position for the test operation and a cleaning position—and furthermore a screen changer is provided, which has at least two screen positions in the interior of the testing device which is heated, namely a pre-heating and a testing position, in addition to a respective insertion and removal positions.