Cover film stretching device

Abstract

The invention relates to a packaging machine with which packaging cavities ( 3 ) are filled with a product to be packaged and are closed by a cover film ( 2 ). The packaging cavities ( 3 ) are displaced in an intermittent manner along the packaging machine, and the cover film is stretched to its exact positioning on the packaging cavities. The invention also relates to a method for sealing a cover film on packaging cavities.

1 . Packaging machine, by means of which packaging troughs ( 1 ) are filled with packagable material and closed by a cover film ( 2 ), wherein the packaging troughs ( 1 ) are moved intermittently along the packaging machine and the cover film ( 2 ) is stretched for its exact positioning above the packaging troughs ( 1 ) counter to its direction of travel by means of a stretching device ( 4 ) that is not based on the movement of the packaging troughs ( 1 ), characterized in that the stretching device ( 4 ) has a clamping means ( 5 ) for the cover film ( 2 ) as well as a shifting means ( 6 ).  
   
   
       2 . (canceled)  
   
   
       3 . Packaging machine according to  claim 1 , characterized in that it has a photocell ( 7 ), which detects print marks ( 8 ).  
   
   
       4 . Packaging machine according to  claim 1 , characterized in that the cover film is supported as a film roll ( 9 ) on a roll holder ( 10 ).  
   
   
       5 . Packaging machine according to  claim 1 , characterized in that the cover film ( 2 ) may be tensioned by means of a dancer roll ( 11 ).  
   
   
       6 . Method of sealing a cover film ( 2 ) on packaging troughs ( 1 ) that are moved intermittently along a packaging machine and whereby the cover film ( 2 ) is stretched for its exact positioning above the packaging troughs ( 1 ) without the aid of the movement of the packaging troughs ( 1 ) and then sealed, characterized in that the cover film ( 2 ) is fixed by a clamping means ( 5 ) and stretched counter to the direction of travel by a shifting means ( 6 ).  
   
   
       7 . Method according to  claim 5 , characterized in that the cover film ( 2 ) is fixed to at least one packaging trough ( 1 ) the cover film ( 2 ) is unwound from a film roll ( 9 ) by the movement of the packaging troughs ( 1 ).  
   
   
       8 . Method according to  claim 6 , characterized in that during the unwinding of the cover film ( 2 ) the actual positioning of print marks ( 8 ) is detected.  
   
   
       9 . Method according to  claim 8 , characterized in that the measure of the stretching is determined on the basis of the difference between actual positioning and setpoint positioning.  
   
   
       10 . Method according to  claim 9 , characterized in that the measure of the stretching is limited on the basis of the film formulation.