Abstract: There is provided a method and an apparatus for forming the tops of material-filled bags into substantially fin-like shapes suitable for sealing in conventional top-sealing machines. The filled bags may be conveyed at random to a top-forming location in the apparatus where a bag is stopped, a device such as a pair of hinged plates is inserted into the top of the bag, front and back forming plates and side gusseting blades simultaneously engage the outside of the bag, forming the top into a fin-shape, the blades and plates are withdrawn, and the bag is then conveyed from the top-forming location. Bag tops are formed more consistently and with excess air expelled with the present method and apparatus.

Abstract: A slitter mechanism for use in a double fold bottomer apparatus employed in making bags from starting flush cut tubes is described which gives precise, high speed side marginal tube slitting in order to permit subsequent downstream gluing and folding operations. In preferred forms, the slitter mechanism includes a bag-end separating assembly having a vacuum manifold and a cooperating adjacent deflector bar serving to separate end portions of the sidewalls of a moving tube. A sequentially rotatable blade is also provided which first enters the open end of the moving tube between separated wall portions, overtakes and slits the leading side margin of the tube, and then stops with a trailing slitting edge situated within the tube open end; subsequent bag movement causes the trailing tube side margin to engage and be slit by the stationary blade edge.

Abstract: An improved bag construction, and a method of bag forming, are disclosed which gives an economical yet strong, burst- and leak-resistant closure without the necessity of sewing or use of expensive stepped cut tubes. The bag is formed using a tube having opposed, interconnected front and rear panels, wherein a pair of laterally spaced, parallel cut lines are provided adjacent the top margin of the tube which define opposed first and second marginal flaps respectively in the front and rear panels. In bag-forming operations, the first flap is folded and glued against the outer face of the front panel, and the closure is completed by folding and gluing the second flap over the open end of the tube in a manner to refold the first flap and engage the outer face of the first panel. In another embodiment, a filling valve is inserted between the front and rear panels adjacent the closure end during the bag-forming operation, so as to provide a valve bag.