Film guiding assembly
A film guiding assembly for guiding a plastic film during travel along a desired path includes at least two non-rotating turning bars over which the film passes, and an actuator for pivoting the turning bars to laterally shift the film. A sensor for senses the lateral position of the film downstream of the turning bars and operates to cause the actuator to pivot the turning bars when necessary to maintain the film leaving the guiding assembly in the desired path.
This application claims priority from U.S. Provisional Patent Application No. 60/903322 filed Feb. 26, 2007.
FIELD OF INVENTIONThe present invention relates to film guiding assemblies for guiding plastic film during travel along a desired path.
BACKGROUND OF THE INVENTIONIt is frequently necessary to guide plastic film as it travels along a desired path. Guiding techniques currently used usually comprise a set of rollers which pivot to change the direction of the film. However, this often produces a change in film tension, with resulted tension memory in the film. Such tension memory can cause problems further along the path of travel. For example, if the film is subsequently wound on a roll and the tension of the film during winding is not sufficient, the edge of the roll may follow the film memory so that the roll edges are not straight. Edge guides which utilize such techniques therefore tend to create the same problem which they were designed to eliminate.
SUMMARY OF THE INVENTIONThe present invention provides a film guiding assembly for guiding a plastic film during travel along a desired path, the assembly including:
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- at least two non-rotating turning bars over which the film passes;
- an actuator for pivoting the turning bars to laterally shift the film; and
- a sensor for sensing the lateral position of the film downstream of the turning bars and operable to cause the actuator to pivot the turning bars when necessary to maintain the film leaving the guiding assembly in the desired path.
The film therefore slides over the turning bars. The turning bars may be lubricated by a gas such as air for use with sticky films or films with a high coefficient of friction or may have a slippery coating. It has been found that such an arrangement guides a plastic film without causing any substantial additional stress in the film such that, if the film is subsequently wound onto a roll for example, the film in the roll is subsequently without tension memory.
The actuators may also be operable to move the turning bars to a loading position in which the film can be passed therebetween in a downward direction. Further, the guiding assembly may include further actuators operable to permit the turning bars to rotate during a start-up operation.
One embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, of which:
Referring to the drawings and as shown in
The various parts of the guiding assembly referred to above will of course be appropriately secured to a suitable main frame, as will be readily apparent to a person skilled in the art.
When the film 10 is initially being threaded through the guiding assembly, the actuators 36, 38 are operated to permit the turning bars 12, 14 to rotate, see
The actuator 26 is then operated to return the carrier 16 back to the position showing in
The advantages of the invention and other embodiments thereof will now be readily apparent to a person skilled in the art, the scope of the invention being defined in the appended claims.
Claims
1. A film guiding assembly for guiding a plastic film during travel along a desired path, said assembly including:
- at least two non-rotating turning bars over which the film passes;
- an actuator for pivoting the turning bars to laterally shift the film; and
- a sensor for sensing the lateral position of the film downstream of the turning bars and operable to cause the actuator to pivot the turning bars when necessary to maintain the film leaving the guiding assembly in the desired path.
2. A guiding assembly according to claim 1 wherein the actuator is also operable to move the turning bars to a loading position in which the film can be passed therebetween in a downward direction.
3. A guiding assembly according to claim 1 including further actuators operable to permit the turning bars to rotate during a start-up operation.
Type: Application
Filed: Oct 18, 2007
Publication Date: Aug 28, 2008
Inventor: Mirek Planeta (Mississauga)
Application Number: 11/907,837
International Classification: B65H 20/36 (20060101);