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

1988-08-22

1989-05-02

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

048264148

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 ring "chimney" surrounding the tube. Maximum cooling requires maximum air velocity and in prior art apparatus this may 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 resricted to ensure that this does not happen. In the new air rings the side wall of the chimney diverges outwards in the direction of bubble movement to form a chamber, an end wall closing the downstream end of the chamber turning suddenly radially inwards toward the bubble to form a short narrow orifice. This chamber side wall is spaced from the tube outer wall along its entire length a minimum distance substantially greater than the outlet orifice, preferably from 2 to 20 times greater. The chamber has at least one aperture, preferably a plurality of circumferentially spaced apertures, whihc permit ambient air to bleed into the chamber and reduce the vacuum to a safe value. The apertures preferably are of controllable flow to permit adjustment of the vacuum force. The air velocity and vacuum are now effectively independent of one another and can be adjusted separately. Different structures to accommodate bubbles of a range of blow-up ratios are provided.

REFERENCES:
patent: 4139338 (1979-02-01), Cole
patent: 4259047 (1981-03-01), Cole
patent: 4473527 (1984-09-01), Fujisaki et al.
patent: 4478564 (1984-10-01), Shinmoto
patent: 4717323 (1988-01-01), Karl et al.
patent: 4750874 (1988-06-01), Keim
"Blown Films's A Cinch with New Air Ring", Plastics Technology, Sep. 1988.

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