Sack, and a method and apparatus for filling, removing air from, and closing the sack

摘要

A tube sack has a fill chamber and a flag at one end thereof, the flag having a sealing seam at the outer end thereof and a labyrinth seam which is adjacent the fill chamber and which is arranged to provide small passages through which air can flow from the fill chamber to a ventilation chamber located between the sealing and labyrinth seams. A vent opening is provided in the form of a perforation through a wall of the flag or an interruption in the seal seam, and is sealed by a bridging seam which surrounds it or by a seal piece which is glued over it. In a method and apparatus for making the sack, a tube is formed and sealed at one end, is then filled, and the flag, sealing seam and labyrinth seam are then made in the other end along with, where appropriate, a perforation for the vent opening. The sack is placed on a horizontal conveyor apparatus and passes through a mechanism which presses air out of the fill chamber through the vent opening, and the vent opening is then sealed by the bridging seam or by the seal piece.