Air ring for controlling blown film thickness
US5288219A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 25, 1991 |
| Grant date | Feb 22, 1994 |
| Priority date | — |
| Expiry date | Mar 25, 2011 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB29C2948/92923
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
Apparatus and method are described for controlling thickness of plastic films produced by the blown film process. The apparatus is an air cooling ring modified to include devices for locally modifying the temperature of the air discharged from the air ring onto the blown bubble. Local variations in the temperature of the cooling air applied to the surface of the bubble result in variations in the bubble cooling rate and viscosity, with consequent variations in thinning during transverse bubble expansion. The method includes controlling the location and extent of local temperature variation applied to the bubble in response to comparison of measured film thickness with a desired film thickness.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.