Finishing assembly and method for a vertical form, fill and seal machine

Abstract

A stripping/sealing assembly and method for a vertical form, fill and seal machine. The stripping assembly comprises a rotatable master axis including a pair of oppositely rotating primary axes. A stripper may be associated with each of the primary axes, each stripper being located in a mount. A slave axis, comprising a pair of rotatable cranks mounted on central axes, is provided for displacement of the mounts in unison toward and away from the primary axes during rotation. By judicious retarding and then accelerating of the rotation of the cranks in relation to the primary axes, the stripper/sealer dies traverse linear paths along the tubular film to strip and seal the tubular film. The method provides adjustable seal dwell time, stripping and seal cooling time all programmable in software.

What is claims is:  
     
         1 . A stripping/sealing assembly for a vertical form, fill and seal (VFFS) machine, the VFFS machine including a source of plastic film, a product delivery head, a device for forming the film into a tubular configuration and a drive mechanism for advancing the tubular film as a product is packaged therewithin, the stripping/sealing assembly comprising 
 a. a rotatable master axis including a pair of oppositely rotating primary axes,    b. a drive for rotating said primary axes in unison,    c. a stripper/sealer associated with each of said primary axes,    d. a mount for each stripper/sealer, each mount being connected to one of said primary axes, and    e. a slave axis for said mounts, said slave axis including a displacement mechanism connected to each mount for selectively moving said mounts in unison toward and away from said primary axes.    
     
     
         2 . The stripping/sealing assembly according to  claim 1  in which said master axis includes a support mounted on each primary axis, each support having a slot formed therein, one of said mounts being located in each of said slots.  
     
     
         3 . The stripping/sealing assembly according to  claim 2  in which each said displacement mechanism comprises a rotatable crank mounted on a central axis and an arm connected to said crank at an offset position, said arm being connected to one of said mounts.  
     
     
         4 . The stripping/sealing assembly according to  claim 3  in which said primary axes and said central axes are coaxial.  
     
     
         5 . The stripping/sealing assembly according to  claim 3  including a drive for rotating said central axes in unison.  
     
     
         6 . The stripping/sealing assembly according to  claim 5  in which each said drive comprises a servo motor.  
     
     
         7 . The stripping/sealing assembly according to  claim 5  in which each said drive comprises a stepper motor.  
     
     
         8 . The stripping/sealing assembly according to  claim 5  in which said drives comprise a differential gearbox, said gearbox including a prime mover for driving said axes.  
     
     
         9 . The stripping/sealing assembly according to  claim 8  including a drive for said gearbox to provide a variable differential speed for said axes.  
     
     
         10 . The stripping/sealing assembly according to  claim 5  including a programmable control for said drives.  
     
     
         11 . The stripping/sealing assembly according to  claim 1  in which each stripper comprises a stripper bar, each stripper bar being mounted in a die connected to said mount.  
     
     
         12 . The stripping/sealing assembly according to  claim 11  in which said dies include a sealing mechanism.  
     
     
         13 . The stripping/sealing assembly according to  claim 11  in which said dies include a staging mechanism.  
     
     
         14 . A method of stripping and sealing an advancing tubular film in a vertical form, fill and seal (VFFS) machine, the VFFS machine including a source of plastic film, a product delivery head, a device for forming the film into a tubular configuration and a drive mechanism for advancing the tubular film as product is packaged therewithin, and the VFFS machine further including a stripping and sealing assembly comprising a pair of stripper/sealer jaws, each stripper/sealer jaw being mounted for rotation about spaced, primary axes with the strippers being located on opposite sides of the tubular film such that the tubular film is contacted between the stripper/sealer jaws for each revolution of the primary axes, the method comprising the steps of 
 a. rotating the stripper/sealer jaws in unison about the primary axes, and    b. displacing the stripper/sealer jaws toward and away from the primary axes during a predetermined portion of each revolution of the primary axes to cause the stripper/sealer jaws to follow generally linear paths along the tubular film at a speed faster than the tubular film to strip the tubular film.    
     
     
         15 . The method according to  claim 14  in which the stripper/sealer jaws are mounted in slots in opposite arms rotatably mounted on the primary axes, and method step “b” comprises displacing the stripper/sealer jaws along the slots.  
     
     
         16 . The method according to  claim 14  in which each stripper/sealer jaw comprises a stripper mounted in a die, the dies further including a sealing mechanism, and including the further step of sealing the tubular film after method step “b”.