Packaging container production equipment and packaging container production method

A packaging container making apparatus for forming tubular web from sheet-like web and producing packaging containers, comprising:

• a web feeding roller for transporting the sheet-like web along a feed path in a direction lengthwise of the sheet-like web;
• a web tensioning device including a rocking arm and a dancer roller secured at a distal end thereof, said dancer roller applying a pressing force against the sheet-like web, said rocking arm being mounted for pivoting between upper limit and lower limit positions;
• a web tension pressing force setting means for setting a value for the pressing force applied by said tensioning device;
• tube forming means for forming the sheet-like web into a tubular web;
• a sealing member for sealing portions of the tubular web by pressing together opposing sides of the tubular web, said pressing forming a transverse sealed portion in said tubular web extending in the direction orthogonal to the lengthwise direction of the tubular web and forming lugs adjacent opposing ends of said transverse sealed portion;
• mark detecting means for detecting registration of predetermined detection marks on the web with points of detection established in advance;
• folding means for folding said lugs through an angle and for advancing the tubular web a distance corresponding to the angle of the folding of the lugs;
• a folding amount controlling means for controlling said folding means by selecting an optimal mode of operation for said folding means from a plurality of modes of operation, responsive to a deviation in timing of detection of the registration;
• and
• rocking arm drive means connected to said rocking arm for adjusting the value for pressing force set by said web tension pressing force setting means according to the mode of operation selected as optimal by the folding amount controlling means.