Apparatus for Maintaining Tension in a Vertically Positioned Horizontally Traversing Plastic Film Web

Abstract

In an automated machine that forms a vertically positioned and horizontally traversing web of plastic film into bags and fills the bags with material, the apparatus maintains tension in the plastic film web and supports and maintains the web horizontally aligned as it traverses through the machine. The apparatus includes upstream and downstream guide rollers. The upstream roller is mounted on an arm which is rotatably biased about a vertical axis and is thereby moveable. The upstream roller has an outer concave perimeter surface and the downstream roller has an outer convex perimeter surface. A longitudinal edge portion of the web extends horizontally from an upstream location, around the upstream roller, to and around the downstream roller and to a downstream location. The web extends vertically below the longitudinal edge portion. A rotational sensor coupled to the arm provides an output signal representative of the location of the arm.

What is claimed is: 
     
         1 . A apparatus for maintaining tension in a vertically positioned web of plastic film traversing horizontally from an upstream location to a downstream location, said apparatus comprising:
 an upstream guide roller rotatable about a vertical axis;   a downstream guide roller rotatable about a vertical axis;   wherein a longitudinal edge portion of said plastic film web extends horizontally from said upstream location, around said upstream guide roller, to and around said downstream guide roller and to said downstream location;   wherein said plastic film web extends vertically below said longitudinal edge portion; and,   wherein at least one of said upstream guide roller or downstream guide roller are moveable relative to said upstream and downstream locations, whereby tension is maintained in said web longitudinal edge portion and said web is supported and maintained horizontally aligned.   
     
     
         2 . The apparatus of  claim 1  wherein one of said guide rollers includes an outer concave perimeter surface and the other of said guide rollers includes an outer convex perimeter surface. 
     
     
         3 . The apparatus of  claim 1  wherein said upstream guide roller includes an outer concave perimeter surface and said downstream guide roller includes an outer convex perimeter surface. 
     
     
         4 . The apparatus of  claim 1  wherein said web of plastic film is folded along a central longitudinal fold line thereby defining a pair of parallel proximate longitudinal edge portions, and wherein both said pair of edge portions extend horizontally from said upstream location, around said upstream guide roller, to and around said downstream guide roller and to said downstream location, and said longitudinal fold line is located vertically below said longitudinal edge portions. 
     
     
         5 . The apparatus of  claim 4  wherein a bag opening and closing assembly is provided downstream from said downstream guide roller whereat said longitudinal edge portions are separated whereby a bag is selectively opened and filled with material. 
     
     
         6 . The apparatus of  claim 1  further comprising an arm rotatable about said downstream guide roller vertical axis and wherein said upstream guide roller is rotatably mounted on and rotates with said arm, whereby said upstream guide roller is moveable relative to said upstream and downstream locations. 
     
     
         7 . The apparatus of  claim 6  further comprising a spring coupled to and rotatably biasing said arm about said downstream guide roller vertical axis. 
     
     
         8 . The apparatus of  claim 6  wherein one of said guide rollers includes an outer concave perimeter surface and the other of said guide rollers includes an outer convex perimeter surface. 
     
     
         9 . The apparatus of  claim 6  wherein said upstream guide roller includes an outer concave perimeter surface and said downstream guide roller includes an outer convex perimeter surface. 
     
     
         10 . The apparatus of  claim 9  further comprising a spring coupled to and rotatably biasing said arm about said downstream guide roller vertical axis. 
     
     
         11 . The apparatus of  claim 6  wherein said web of plastic film is folded along a central longitudinal fold line thereby defining a pair of parallel proximate longitudinal edge portions, and wherein both said pair of edge portions extend horizontally from said upstream location, around said upstream guide roller, to and around said downstream guide roller and to said downstream location, and said longitudinal fold line is located vertically below said longitudinal edge portions. 
     
     
         12 . The apparatus of  claim 11  wherein a bag opening and closing assembly is provided downstream from said downstream guide roller whereat said longitudinal edge portions are separated whereby a bag is selectively opened and filled with material. 
     
     
         13 . The apparatus of  claim 6  wherein a rotational sensor is coupled to said arm and provides an output signal representative of the rotational position of said arm. 
     
     
         14 . The apparatus of  claim 1  further comprising an arm rotatable about an arm vertical axis and wherein one of said guide rollers is rotatably mounted on and rotates with said arm about said arm vertical axis, whereby said guide roller mounted on said arm is moveable relative to said upstream and downstream locations. 
     
     
         15 . The apparatus of  claim 14  further comprising a spring coupled to and rotatably biasing said arm about said arm vertical axis. 
     
     
         16 . The apparatus of  claim 14  wherein one of said guide rollers includes an outer concave perimeter surface and the other of said guide rollers includes an outer convex perimeter surface. 
     
     
         17 . The apparatus of  claim 14  wherein said upstream guide roller includes an outer concave perimeter surface and said downstream guide roller includes an outer convex perimeter surface. 
     
     
         18 . The apparatus of  claim 14  wherein a rotational sensor is coupled to said arm and provides an output signal representative of the rotational position of said arm. 
     
     
         19 . The apparatus of  claim 14  wherein said web of plastic film is folded along a central longitudinal fold line thereby defining a pair of parallel proximate longitudinal edge portions, and wherein both said pair of edge portions extend horizontally from said upstream location, around said upstream guide roller, to and around said downstream guide roller and to said downstream location, and said longitudinal fold line is located vertically below said longitudinal edge portions. 
     
     
         20 . The apparatus of  claim 19  wherein a bag opening and closing assembly is provided downstream from said downstream guide roller whereat said longitudinal edge portions are separated whereby a bag is selectively opened and filled with material.