Process and apparatus for making a thermoplastic foil
US4911868A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 25, 1988 |
| Grant date | Mar 27, 1990 |
| Priority date | — |
| Expiry date | Nov 25, 2008 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB29C2948/92904
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
The process for making a thermoplastic foil involves the use of a wide-outlet or long-slit die which has at least one outlet-gap-defining adjustable die lip, an opposing gap-bounding lip and a group of piezotranslators distributed over the length of the outlet-gap-defining adjustable die lip, each of which is part of a control loop, acts as a positioning member and is associated with an individual section of an outlet-gap-defining adjustable die lip. At least one actual value of the foil thickness of the thermoplastic foil formed is measured with a measuring device and is fed to a controlling processor. Each of the piezotranslators is controlled by a controlling processor with a controlling variable. In the controlling processor a distribution control variable which is generated by a thickness variation or error is generated by a control variable deviating from a setpoint value and the distribution control variable is fed to individual piezotranslators from the controlling processor according to a distribution function which distributes the thickness errors over the length of the adjustable outlet-gap-defining adjustable die lip.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.