FR2633870A1 - Method for producing a bag and bag obtained - Google Patents

Abstract

In order to manufacture a bag according to the invention, a composite sheet which is heat-sealable on one face is folded, producing a reentrant pleat 5, 6 enclosed between the two panels of the folding, and folding down the corners 9 to 12 of the reentrant pleat towards the inside and bonding (welding) the flaps along their lateral edges at 7 and 8 and the folded-down corners along the folding lines 13 to 16.

Description

 The invention relates to a method of producing a bag intended in particular to constitute a cover for the packaging of industrial products placed on pallets.

 A known packaging technique consists in placing a composite sheet on a pallet, an outer face of which is aluminum foil and an inner face of polyethylene or any other heat-sealable material. The industrial product to be packaged is then placed on this sheet (on its heat-weldable side) which is then capped with a bag also made of the same composite material and the edges of the bag are welded to the base sheet.

The bag in question is generally with a rectangular bottom and is obtained by welding this bottom to a wall.
Lateral, itself closed on itself by welding its adjacent edges. This operation is Long and has a considerable impact on the cost of the product.

 The present invention intends to propose a solution for manufacturing this bag much faster and thus reduce the cost price.

A first object of the invention therefore resides in a process for producing a bag with a rectangular bottom from a composite sheet material, one face of which is heat sealable, characterized in that it comprises the following steps
- production of a folding of the sheet comprising a re-entrant fold covered by two superimposable flaps, the heat-sealable face forming the internal face of the flaps,
- heating of the parallel edges, perpendicular to the fold, of the sheet thus folded so as to join the heat-weldable portions facing each other by welding,
- folding on itself of each corner located at the Longitudinal ends of the fold returning along a
Line oblique to the longitudinal direction of pLi,
- Heating of each folded assembly thus produced at the ends of the re-entrant fold, along the oblique fold line to join the heat-sealable parts facing each other by welding.

 In a variant, it is possible first of all to carry out the folding operations and then to the lateral and end welds.

Alternatively, we proceed to a first welding
lateral then at the corner bending and finally at the oblique welding.

This variant will be preferred because the folding operation of the corners is facilitated, compared to the previous one, by the lateral welding from one end to the other of the edges.

 The corners are folded either towards the inside of the inside fold, or towards the outside. Note, however, that an inward fold is easier and quicker to do since it is in abutment in the bottom of the re-entrant fold.

 The second object of the invention is a packaging bag made of composite sheet, one face of which is heat-weldable with a substantially rectangular bottom, characterized in that, when it is in volume, each of the two opposite lateral walls of the bag surmounting the smaller sides of the bottom has a Y weld whose branches converge from the ends of the short sides.

 This bag typically includes, due to its manufacturing process and the fact that it is necessary to avoid any expensive recovery operation, extensions formed from a double sheet thickness, triangular, originating from each of the branches of the Y.

 The invention will be better understood during the description given below of nonlimiting exemplary embodiments which also make it possible to identify the advantages and the secondary characteristics thereof.

Reference will be made to the accompanying drawings in which
FIGS. 1 to 4 illustrate the different phases of the method according to the invention in a preferred implementation,
FIG. 5 is a partial exterior perspective view of an area of the bag according to the invention in the vicinity of the bottom,
- Figure 6 is a partial interior view of the same bag part.

 Referring to Figure 1, we see a rectangular sheet 1 which is folded back on itself so as to constitute two flaps 2 and 3 and a re-entrant fold 4 connecting the two flaps and covered by them. This fold has two sides 5 and 6 inside the two parts 2 and 3.

 The sheet 1 is composite with a face 1a for example of aluminum and a face 1b for example of polyethylene (or any other heat-weldable material). The folding is such that the side 1b is interior.

 In Figure 2 are shown in 7 and 8 the traces made by a heating tongs for welding the edges of the folded sheet 1. The blank of the bag thus formed is such that the flaps 2 and 3 are welded together by their lateral edges and, at the re-entrant fold 4, are welded one 2 to pan 5 and the other 3 to pan 6 of withdrawal. On the other hand, the sides 5 and 6 are not welded together, because they face each other by the non-weldable aluminum face of your sheet.

 3 shows the blank of Figure 2 in which we folded each of the corners 9, 10, 11 and 12 of the longitudinal ends of the fold returning inside this fold. The resulting fold lines are referenced 13, 14, 15 and 16 in FIG. 3. The film thicknesses are then heated by heating tongs in the vicinity of these fold lines. The result of this heating is a welding of the pan 5 on the shutter 2 and of the pan 6 on the shutter 3 along the fold lines. The welding will be more effective between the layers closest to the surface than between the internal layers because the former are closer to the machotre of the heating clip.

In other words, as seen in Figure
4, if the corners have been folded towards the inside of the fold
hollow, these are the welding zones 17,18,19,20 located at
inside lines 13, 14, 15 and 16 which will be the most
resistant. The reverse would be the case, i.e. the welding zones located outside these lines which would be
The most resistant, if the corners were folded outwards. However, it can be seen that the welding along the lines 13 to 16 is, by the very fact of the process, twice as wide as the welding zones 7 and 8. It can be seen that the
lines 13 to 16 are inclined at 45 on the longitudinal direction of the re-entrant fold. This value results from the fact that
the drawdown of the corners was such that their welded edges were placed near the bottom of the box pleat. We could have a greater angle if this drawdown was less significant.

 The volume setting of the bag is illustrated in FIG. 5, where we find the fold lines 14 and 16 framed by weld zones 20 and 21 for Line 14 and 19 and 22 for your Line 16.

 It can be seen that the bottom consists of the sides 5 and 6 of the fold, while the side walls of the bag surmounting your short sides 23 of the bottom have a Y weld defined by the zones 16 and 20 which converge to merge in the zone 8.

 Figure 6 is an image of this part of the bag seen from the inside. The corners 10 and 12 (and 9 and 11 not shown in Figures 5 and 6) form, when the bag is in volume, triangular ears from the bias weld areas 16 and 20. These ears are of double thickness which help maintain the volume of the bag when they are folded against the wall thereof.

 In the method described above, the folding of the corners 9 to 12 took place after the welds 7 and 8 have been produced. It is not outside the scope of the invention to provide a folding of the corners before this operation welding and welding the edges of the flaps 2 and 3 and along the lines 13 to 16 in the same phase.

 The implementation of this production method makes it possible to obtain a bag in a much shorter time than that necessary for the usual making of the bag.

Claims (9)

 1. Method for producing a bag with a rectangular bottom from a composite sheet material (1), one side of which is heat sealable (lob), characterized in that it comprises The following steps  - production of a folding of the sheet comprising a re-entrant fold (4) covered by two overlapping flaps (2,3), the heat-sealable face forming the internal face of the flaps,  heating the parallel edges (7,8) perpendicular to the fold (4) of the sheet thus folded so as to join the heat-sealable portions facing each other by welding,  - folding on itself of each corner (9 to 12) located at the longitudinal ends of the fold returning along an oblique line (13 to 16) relative to the longitudinal direction of the fold (4),  - Heating of each folded assembly thus produced at the ends of the re-entrant fold, along the oblique fold line (13 to 16) to secure the heat-sealable parts facing each other by welding.  2. Method according to claim 1 characterized in that the corner folding operation is carried out before the edges are heated and that of each folded assembly.  3. Method according to claim 1 characterized in that the folding of the corners on themselves is carried out after the welding of the parallel edges.  4. Method according to any one of the preceding claims, characterized in that the folding of the corners (9 to 12) is carried out inside the re-entrant fold (4).  5. Method according to any one of claims 1 to 3 characterized in that the folding of the corners is carried out outside the re-entrant fold (4).  6. Method according to any one of the preceding claims, characterized in that the oblique line (13 to 16) is inclined by 45 on the returning fold.  7. Composite sheet packaging bag, one face of which is heat-weldable with a substantially rectangular bottom, characterized in that, when it is in volume, each of the two opposite lateral displays of the bag overcoming the smallest sides (23) of the bottom has a Y weld whose branches converge from the ends of the short sides (23).  8. Bag according to claim 7 characterized in that each of the two branches of the Y-weld separates the side wall of a triangular extension (10,12) outside of double thickness.  9. Bag according to claim 7 or claim 8 characterized in that the width of the weld (16,20) of the two branches of the Y is twice that of the leg (8).