Sack and method and device for producing sacks
A method for the production of sacks from tubular pieces which include plastic material includes at least at one end area, laying a bottom rectangle around a fold line to form triangular pockets, with the bottom rectangle including flaps, folding back parts of the flaps of the bottom rectangle, and applying and connecting a bottom cover sheet at least to areas of the flaps of the bottom rectangle and/or to areas of the triangular pockets. The bottom rectangle includes at least in part an air-permeable material.
1. A method for the production of sacks from tubular pieces which include plastic material comprising:
laying at least at one end area a bottom rectangle around a fold line to form triangular pockets, with said bottom rectangle including flaps,
folding back parts of the flaps of the bottom rectangle, and
applying and connecting a bottom cover sheet at least to areas of the flaps of the bottom rectangle and/or to areas of the triangular pockets,
the bottom cover sheet including a first layer and a second layer,
with the first layer facing the flaps and/or triangular pockets having a material of construction that is an air-impermeable material, the first layer having perforations introduced therein, and adhesive connecting seams thereon that completely encircle individually each of the perforations, and
the second layer having a material of construction that includes an air-permeable material, and the second layer being applied to the first layer and connected thereto via the adhesive connecting seams.
2. The method according to claim 1 , wherein
the flaps are folded such that edges of the flaps and edges of the triangular pockets and/or an edge of a valve patch encircle an opening through which an interior of the sack is accessible.
3. The method according to claim 1 , wherein
each surface encircled by the adhesive connecting seams is at least twice as large as a surface of the corresponding perforation.
4. The method according to claim 1 ,
further comprising a third layer that is applied to and is connected to at least one of the first layer and the second layer.
5. The method according to claim 4 , wherein
into the third layer, at least in a vicinity of the perforations of the first layer, cuts are introduced.
6. The method according to claim 5 , wherein
the cuts are made in a form of a circular arc.
7. The method according to claim 6 , wherein
a seamlessly produced tube is used which includes a circular fabric of extended plastic bands, with the circular fabric being coated with a plastic.
8. The method according to claim 1 , wherein
the bottom cover sheet is fastened to a bottom area of the sack by a heat-induced joining process.
9. The method according to claim 8 , wherein
before the fastening of the bottom cover sheet to the bottom area of the sack, a separating agent is applied to areas of a side of the bottom cover sheet, including the side facing the bottom of the sack, which covers an opening through which an interior of the sack is accessible.
10. The method according to claim 1 , wherein the adhesive connecting seams that encircle each of the perforations individually include a pair of opposed seams extending longitudinally along the bottom sheet, and a pair of opposed seams extending transversely across the bottom sheet.