Windmoller Holscher

Klaus-Peter Voss

Werner Feistkorn

Klemens Sensen

Hans-Udo Beckmann

The invention refers to a method for the reduction of the sag and/or of the different stress profile of a flattened tubular film web produced by a blown film process and made of thermo-plastic synthetic resin, transversely to its longitudinal direction. For the solution of the problem to provide a method according to which the sag and/or the different states of tension transversely to the tubular film web can be easily reduced or eliminated to a maximum degree, the tubular film web is heated along its width and then cooled and/or stretched. Furthermore, the invention refers to an apparatus for carrying out the method.

Method and apparatus for the reduction of the sag and/or of the varying

An apparatus is provided for controlling the flow of air for external cooling of a tubular film issuing from an extruder head. To ensure that the flow of the air for external cooling to the point at which the tubular film begins to expand can be controlled regardless of the distance from that point to the extruder head, flow-directing flaps are evenly distributed around the tubular film and are displaceable along the tubular film.

Apparatus for controlling the flow of air for external cooling of an

To determine and/or automatically control the degree of orientation of tubular films which have been made in a film-blowing plant including an extruder having a film-blowing head and apparatus for internal cooling and also including flattening and take-off apparatus, the rate of exchange of the air for internal cooling, the speed of the extruder, the temperature of the plastic composition being extruded and/or the take-off velocity are controlled. To ensure that the degree of orientation can be determined and/or automatically controlled in a simple manner and without an occurrence of trouble, that shape of the flaring portion of the bubble which corresponds to the desired degree of orientation is determined and/or adjusted and is recorded as the desired shape of the bubble. The actual shape of the flaring portion of the bubble is detected and compared with and adapted to the desired shape.

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Lengerich, Germany

Klaus-Peter Voss