Web guiding apparatus

Apparatus for correcting the lateral divergence or displacement of a travelling air-impervious web from an intended line of longitudinal travel between two points, said apparatus comprising:

• a series of at least two freely rotatable parallel rollers for supporting the web at one side thereof at a zone between said points, said rollers being mounted for pivotable movement so that the angle between their axes and said line of travel, in the projected plane of the web, can be varied,
• a freely rotatable stationary roller mounted upstream from said series of pitotable rollers, the distance between said stationary roller and the adjacent roller of the series of pivotable rollers being at least equal to 1.5 times the length of a roller;
• and
• means for producing on one side of said roller series an air-pressure difference capable of urging a web, which in the absence of such air-pressure difference would be pulled in a tangent plane to said rollers, to follow a path which curves into the space between said pivotable rollers thereby to increase the angle of wrap to effect a substantial frictional engagement of the web with said pivotable rollers, and means for confining said air pressure difference to substantially the length of web within said roller series whereby said web follows a rectilinear path between the stationary roller and the series of pivotable rollers.