Air rings for production of blown plastic film

Details Air rings for production of blown plastic film Air rings for production of blown plastic film

1989-03-09

1990-05-29

Chiesa, Richard L.

Plastic article or earthenware shaping or treating: apparatus

Shaping orifice and downstream work contacting gaseous...

264565, 264568, 4253261, 425388, B29C 4788

Patent

active

049291629

ABSTRACT:
The invention provides a new air ring of single or dual orifice type for use as a primary or secondary ring to cool a blown extruded tube of molten plastic material, and also to stabilize the moving tube. The air from the ring is kept in contact with the tube outer surface as much as possible by a chamber surrounding the tube. Maximum cooling requires maximum air velocity and in prior art apparatus this may then cause generation of vibrations of the bubble, resulting in non-uniform film, or even disruption of the bubble. The air volume and velocity must therefore be restricted to ensure that this does not happen. In the new air rings the side wall of the chamber diverges outwards in the direction of bubble movement with an end wall closing the downstream of the chamber and forming a short narrow orifice. The chamber is provided with a plurality of thin annular partition members which extend radially inwards so that their inner edges are close to the bubble wall to provide respective short, narrow gaps. Each adjacent pair of partitions forms a small annular chamber, and the endmost partitions form similar small annular chambers with the end walls. The air in these chambers is turbulent and disrupts the laminar flow of air over the bubble wall to increase its cooling effect. In addition a vacuum is formed in each chamber so that this part of the bubble wall is held by a series of small successive vacuums instead of a single vacuum, increasing its stability and permitting higher speed operation.

REFERENCES:
patent: 3548042 (1970-12-01), Hinrichs
patent: 3775523 (1973-11-01), Haley
patent: 3819790 (1974-06-01), North et al.
patent: 3888609 (1975-06-01), Saint Eve et al.
patent: 4069292 (1978-01-01), Herrington et al.
patent: 4139338 (1979-02-01), Cole
patent: 4209475 (1980-06-01), Herrington et al.
patent: 4399094 (1983-08-01), Fujitani et al.
patent: 4717323 (1988-01-01), Karl et al.

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