| 摘要 |
<p>A tubeless vertical form, fill and seal packaging machine has a tube former for receiving flexible packaging material in thin flat strip form and juxtaposing opposite longitudinal edge portions thereof in parallel vertically extending relationship to provide a depending tube open at the top. Side and end sealers respectively seal vertical longitudinal edge portions and provide vertically spaced horizontally extending end seals across the tube. A product dispenser discharges measured quantities of product into the tube interior through its open upper end. Improved tube feed means comprises first and second pairs of vertically spaced rolls respectively on opposite external sides of the tube of packaging material and first and second tube feeding belts respectively trained over said pairs of rolls. Inner runs of the belts engage the tube and have vertically extending imperforate marginal portions and a perforate intermediate portion. Vacuum generating means communicate with the intermediate perforate portions to cause the belts to grip the tube and tube guide and belt back-up means within the tube prevent lateral vacuum loss and provide for frictional tube feeding action. In one form, the back-up means comprise depending cantilevered thin flat members which provide frictional feeding action throughout the width of the belts. In a second form, first and second pairs of back-up members provide frictional feeding action only at the imperforate marginal belt portions. The rolls and belts are adjustable horizontally for varying frictional tube feeding action.</p> |
