| 摘要 |
A vertical form, fill and seal packaging machine in which a predetermined length of web or film is pulled downwardly past a tube forming collar by endless belts located downstream of the collar. A power-rotated feed roll is located upstream of the collar and pulls film from a supply roll for delivery to the collar, the feed roll being driven at a higher surface speed than the pull down belts. To match the supply of the feed roll with the demand of the belts, means sense the tension in the film at a location between the feed roll and the forming collar and cause the feed roll to slip relative to the film as an inverse function of that tension.
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