| 摘要 |
A foam extrusion system and method employs a horizontal vacuum chamber (10) with a bulkhead (11) and extrusion die (16) at one end of the chamber, the extrusion die being inside the chamber when the bulkhead is closed. A liquid baffle, preferably water, is provided at the opposite end of the chamber through which the extrudate passes from the chamber to atmosphere. The baffle comprises a pond (30) of liquid having a higher level in the chamber and a lower level (31) outside the chamber. The higher level of the pond is formed between a dam plate (20) and a seal plate (12), the latter forming the opposite end of the chamber. The seal plate includes a size adjustable window (34) through which the extrudate passes, the extrudate being guided by a conveyor (43) to extend inclined downwardly into the pond and to exit through the seal plate and pond with a large radius upwardly curved section. The level of liquid in the chamber is controlled by circulating liquid (50, 51) from the higher level of the pond within the chamber to the lower level of the pond outside the chamber with the amount of liquid circulated being inversely proportional to the absolute pressure in the vacuum chamber. Optionally the circulated liquid may pass through a cooler (61) to control the liquid temperature. The size adjustment of the window or exit orifice in the seal plate may be used to control the flow of liquid from the lower level pond portion outside the chamber to the higher level pond portion inside the chamber, particularly during start up. |
