| 摘要 |
An air shroud device for a conventional blown film extrusion line. The line has air cooling ring(s) to direct primary cooling air along the bubble to cool the film to the frost line. The air shroud device comprises an annular air shroud plenum having an annular air outlet at a level below the frost line. The shroud device is coaxial, of relatively large size so that its outlet mechanism is spaced substantially radially from the bubble and from the outlets of the air cooling ring(s). The air shroud plenum receives air from a source uninfluenced by variable conditions, and provides a diffused source of the air about the bubble to serve as pseudo-ambient air. Secondary air flow induced by primary flow of cooling air from the air cooling ring(s) comprises air drawn from the spaced-apart air shroud device and not from ambient air.
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