APPARATUS FOR CONTROLLING BACK PRESSURE IN AN EXTRUDER

摘要

A pressure control valve or apparatus adapted for controlling the pressure of a viscous fluid in a conduit by producing a pressure drop which is substantially directly proportional to the valve stem position. The valve or apparatus comprises in combination a valve body having a streamlined flow channel which has a narrow section of substantially uniform cross-sectional dimension opening into a wide section of substantially larger cross-sectional dimension and a plunger which is slidably mounted within the channel. The plunger is adapted for movement within the wide section and narrow section of the flow channel wherein the clearance distance between the sidewall of the narrow section and the plunger surface extending into the narrow section is substantially constant. When the plunger is moved reciprocally into the narrow section the changes in pressure drop across the valve or apparatus are substantially directly proportional to the axial extent to which the plunger lies within the narrow section.