Abstract: A foam extrusion apparatus and method in which extrudate is extruded into a sealed chamber which may be subjected to pressure variation such as a vacuum with the controlled shaping of the plastic being obtained by power driven rolls within the chamber downstream of the die. Because of the harsh environmental conditions within the chamber it is desirable that the shaping or forming rolls be driven by an externally powered source which will therefore be not subject to the pressure, vacuum, or other deliterious conditions found within the chamber. Moreover, because of the external position of the drive with regard to the chamber, the entire system need not then be shut down in order to open the chamber and make the required adjustments or repairs. The chamber is preferably the upper end of a barometric leg into which the extrudate passes. The upper end of the chamber is closed by one or more bulkheads which are movable toward and away from the upper end of the chamber.

Abstract: An apparatus adapted to be positioned downstream of a foam extrusion die in an environmental control or vacuum chamber for remote monitoring of the thickness and profile of foam boards, planks and like extrudates soon after the extrudate exits the die and takes its final shape, is characterized by opposed, relatively narrow shoes on opposite sides of the extrudate path and respective carriages therefor which together are movable transversely with respect to the extrudate path by respective worms and translating nuts and a common worm drive. One shoe is operative to support the bottom surface of the extrudate in a predetermined position while the other shoe rides on the extrudate and is position monitored by a transducer operative then to provide an output signal representative of the spacing between the shoes, and thus the thickness of the extrudate passing between the shoes, to remote monitoring circuitry located outside of the vacuum chamber.

Abstract: A foam extrusion die and monitoring apparatus, including a pair of adjustable die lip members having opposed, rigid die lips defining therebetween an elongated arcuate die orifice, is characterized by position sensors located along the arc of the die lips to monitor the die opening at such locations. The position sensors include sensing styli mounted for movement with the lip members at respective sensing locations such as at the arc ends and arc centers of the die lips, and provision is made for connecting the sensing styli as by precision push-pull, flexible cables to respective linear variable displacement transformers which provide electrical output signals representative of sensed positions to remotely located monitoring circuitry. The apparatus has particular application in a vacuum extrusion line wherein the extrusion die is located inside a vacuum chamber and thus is inaccessible during extrusion.