Patent ID: 6495804
Filing Date: 2002-12-17
Classification: B29B,B29C

Abstract:
A method of heating and cooling an extruder cylinder subdivided along a length thereof into a plurality of heating or heating and cooling zones which comprises the steps of:effecting heat exchange between said cylinder and at least one tubular coil extending along the cylinder in at least one of said zones; heating said at least one of said zones with a resistance heating element outside said coil; passing a heat-carrier oil through said coil during extrusion and cooling said heat-carrier oil by heat exchange with a cooling medium by separate passage of the oil and cooling medium through a heat exchanger; maintaining a reduced flow rate of said heat-carrier oil through said coil even during a purely heating phase of said cylinder to equalize a distribution of temperature in said cylinder; and controlling a flow rate of the cooling medium into heat exchange with said heat-carrier oil continuously in response to temperature of said cylinder with a continuously operating temperature regulator, said heat-carrier oil being brought to a higher temperature than the temperature of said heat-carrier oil during cooling thereby for said reduced flow rate during said purely heating phase, the cooling medium flow rate being controlled by the temperature of the heat-carrier oil.