Forming folds in tubular plastic film - by forming two outer folds, inner folds and additional outer folds

摘要

Pairs of oppositely situated, conertina-type folds are made continuously in tubular plastic film, esp. during the prodn., by (a) forming two outwardly directed single folds by passing the tubular film between nipping rollers, (b) retaining each of the outwardly directed folds as one of the outer folds of the concertina, and (c) forming an inner fold and another outer fold at a distance from each of the outwardly directed single folds. Method gives very precise formation of the concertina-type folds, thus facilitating subsequent bag prodn.