Vacuum extrusion system and method

Abstract

A horizontal vacuum extrusion line includes a fixed bulkhead, a die inside the bulkhead, a telescoping vacuum chamber section and a fixed chamber section. A dam in the fixed section forms a pond for immersion cooling of the extrudate. A truss extends from the dam to the bulkhead supporting, shaping and calibration equipment and extends through the telescoping section. Fluid pressurizable seals at each end of the telescoping section are operable after the telescoping section is closed against the bulkhead and the telescoping and fixed sections are locked together. The telescoping section provide a more compact line and easier access to the complex equipment downstream of the die. The extrudate from the die passes down into the pond and then through an orifice in a hood projecting from the chamber into a lower level portion of the pond exposed to atmosphere. The hood also includes a tractor drive to push the extrudate through the underwater orifice. The hood and its contents are accessible through the atmospheric pond. A tractor haul-off and the tractor drive in the hood are the only extrudate drives between the calibration equipment and atmosphere. The higher level of the pond within the chamber downstream of the dam is controlled by a valve in turn controlling the output of a pump. The valve control senses the pond level and operates independently of the vacuum controls.