FR2738002A1 - BAG OF THE PROVISIONS BAG TYPE PROVIDED WITH A BELLOWS AT ITS BASE, AND PROCESS FOR THE MANUFACTURE OF THIS BAG - Google Patents

Abstract

The invention relates to a bag (1) formed of a single cut material, comprising two side walls (2, 2 ') which are pressed against each other forming a flat surface when the bag is empty and which are connected together, at the bottom, by a lower bellows (3) formed in one piece and without joint with the walls (2, 2 '), comprising two sections forming walls (4, 4') and directed inwards , and, on the sides, by lateral seals (5, 5 ') which also cover the bellows (3). The two sections (4, 4 ') of the bellows (3) are connected to the neighboring side walls by respective slanted joints (6, 6', 12, 12 ') which extend from the two joints (5, 5').

Description

A 2738002

  The present invention relates to a bag formed from a single cut material, comprising two side walls which are applied one against the other. other by forming a flat surface when the bag is empty and which are connected together, at the bottom, by a lower bellows formed in one piece and without joint with the side walls, comprising two sections forming walls and directed inwards , and, on the sides, by side seals which also cover the lower bellows. The invention also relates to a method for manufacturing plastic bags, according to which a sheet strip is folded to form a half-pipe defining the side walls and divided by side joints whose spacing corresponds to the width of the bag and which extend transversely to the longitudinal direction of the half-pipe, the bags thus formed being

  separated at the side seals.

  Bags of this type can be used as shopping bags. They can be made rationally from plastic. The lower bellows directed inwards is used to give the bag a certain lower width, when it is filled, so that it offers a sufficient filling volume. It opens

when filling the bag.

  Compared to square bottom paper bags, bags of this type have the disadvantage of practically not standing upright when opened. The side walls of these paper bags are in fact interconnected not directly by a side seal, but by side bellows directed inward. With the square bottom formed by folding and gluing operations, these paper bags can therefore be erected to form a hollow body in the shape of a parallelepiped which stands upright when it is full and when it is empty. This clearly facilitates the

handling of the bag.

  The object of the invention is therefore to create a bag of the type specified in the introduction which, without harming rational production, makes it possible to obtain characteristics identical to those of a conventional bag with a square bottom, or better. The invention also relates to a method for

  make plastic bags of this type.

  According to the present invention, this object is achieved thanks to the fact that the two sections forming the walls of the lower bellows are connected to the adjacent side walls by respective oblique seals which start from the two side seals. The oblique joints have the effect of strengthening the corners of the bottom corners, which allows the bag to stand upright. The oblique joints preferably extend continuously up to the lower edge of the side walls, but it is also possible to design a joint made by points only. An angle of 45 between the oblique joints and the lower edge of the side walls was found

particularly advantageous.

  The area of the upper edge of each side wall can be designed as a double wall to form a reinforcement, in which case an interior reinforcement section is formed in one piece with the side wall, on the edge, it being specified that the section of reinforcement is connected to the side wall by a joint of

  reinforcement parallel to the upper edge and spaced from it

  this. According to another characteristic of the invention, a handle is fixed to the side wall, inside each reinforcement section. For smaller bags, the

  making holes forming handles may suffice.

  The bag can stand up even better and have an even more beautiful overall appearance if it is made of a polyethylene sheet of at least 50 / m and preferably 80 gm thick. Depending on the application cases, we can however

  consider thicknesses up to 150 gm.

  Particularly good results are obtained with regard to the mechanical characteristics if the polyethylene sheet is produced from a mixture of raw materials composed of polyethylene of different crystallinities and densities, for example: 50% high density polyethylene, 25 % medium density polyethylene and 25% linear low density polyethylene. The proportion by weight percentage of high density polyethylene is always higher than that of medium density polyethylene

  and linear low density polyethylene.

  Thanks to this, the bag can stand upright over its entire height even if it is not completely filled. The bag has a high load-bearing capacity and is insensitive to moisture. But it is obvious that it could also be made from a laminate or a coated textile strip, etc. As regards the method, the object of the present invention is also achieved thanks to the fact that after having formed the half-pipe, a lower bellows is formed which has two sections forming walls, which is directed inwards and which is located between the side walls, that at an interval equal to the width of the bag and coincidentally, the wall sections of the lower bellows are welded, over the entire width of the latter, to the respectively adjacent side walls by means of a seal at an angle, so that the oblique joint forms an isosceles triangle with the lower edge of the side walls, that on the bisector between the two sides of the triangle, a continuous double seal is welded which covers the lower bellows and whose individual joints form the side seals of the bag, and separate the bags between the individual seals. After making the joints at an angle, we weld handles on

  the upper edge of the side walls.

  The oblique joints intended to form a square bottom can be made without great expense before dividing the half-pipe into individual bags. The methods already known per se for making bags from an endless sheet strip therefore need only be slightly modified. Any handles are preferably welded

  before making the side seals.

  An exemplary embodiment of the invention is shown in the drawings and will now be described more

in detail.

  Figure 1 shows an endless strip of sheet that has been folded to form a half-pipe, Figure 2 shows the half-pipe of Figure 1 after the lower bellows has been made, Figure 3 shows the half-pipe of Figure 2 after making the oblique joints and a reinforcement section on the upper edge, Figure 4 shows the half-pipe of Figure 3 transformed, after the installation of the handles, Figure 5 shows the bags finished after the completion of the side seals but before separation, and

  Figure 6 shows a separate, open bag.

  The manufacture of a bag of the present invention will be explained using FIGS. 1 to 5. A strip of polyethylene material, for example, having the material characteristics mentioned above, is folded according to FIG. 1 to form a half-pipe 11. A lower bellows 3 is then formed which is directed inwards, between the two side walls 2 and 2 ', and which

  has two sections forming walls 4, 4 'of the same width.

  According to FIG. 3, oblique joints 6, 6 ′, 12, 6a are produced by welding on the half-pipe thus prepared. These oblique joints extend over the entire width b of the lower bellows 3 or more exactly of the wall sections 4 and 4 ′, up to the lower edge 15 of the side walls. Each oblique joint connects a wall-forming section 4, 4 ′ of the lower bellows to the adjacent side wall, respectively 2 and 2 ′. The oblique joints are also placed so as to form an isosceles triangle defined by the lower edge and the two equal sides 12, 6a. The angle defined between these two sides is preferably 9O, but it could also be

  larger, especially for large bags.

  In the area of the upper edge, a reinforcing section 7, 7 ′ is folded inward on each side wall, whereby the edge of the fold forms the upper edge 16 of the side walls. At a certain distance from this upper edge and in parallel, welds of

respective reinforcement 8, 8 '.

  On a pipe thus prepared, it is possible to weld coincident handles 9 and 9 ′ at regular intervals, according to FIG. 4. The weld points 10 are located in the area of the reinforcement sections 7, 7 ′. Instead of the handles 9, 9 ', we could also introduce cords

  forming handles or cutting holes forming handles.

  To finish the bags, it is then necessary simply to weld a double joint 13 according to a spacing equal to the width of the bag, according to FIG. 5, which joint also covers the lower bellows 3. This double joint forms the bisector of the isosceles triangle comprising the sides 12, 6a. The individual bags can finally be separated in the middle of the double seal 13 using an appropriate cutting device. One could also consider providing a perforation in the double seal, so that the bags could be torn

for example using a roller.

  Figure 6 shows an individual bag 1 open. The spaced lower bellows forms a square bottom 14 which, however, narrows at the oblique joints 6, 6 'and 12, 12' to the side joints 5, 5 '. In the narrowed area is defined, below each of the oblique joints, a small cavity 17, 17 'open at the bottom which helps the bag to stand. Flat, these bags only need a small storage volume and they can be used

  several times thanks to their solidity.

Claims (9)

  1. Bag (1) formed of a single cut material, comprising two side walls (2, 2 ') which are applied one against the other by forming a flat surface when the bag is empty and which are connected together , at the bottom, by a lower bellows (3) formed in one piece and without joint with the side walls, comprising two sections forming walls (4, 4 ') and directed inwards, and, on the sides, by side seals (5, 5 ') which also cover the lower bellows (3), characterized in that the two wall sections (4, 4') of the lower bellows (3) are connected to the adjacent side walls (2, 2 ') by respective oblique joints (6, 6', 12, 12 ') which start from two side seals (5, 5 ').   2. Bag according to claim 1, characterized in that the bias seals (6, 6 ', 12, 12') extend so   continues to the lower edge (15) of the side walls.   3. Bag according to claim 1 or 2, characterized in that the oblique joints (6, 6 ', 12, 12') define with the lower edge (15) of the side walls an angle of 450.   4. Bag according to any one of claims 1   to 3, characterized in that the area of the upper edge of each side wall (2, 2 ') is designed as a double wall to form a reinforcement, an internal reinforcement section (7, 7') being formed in one part with the side wall (2, 2 '), on the edge (16), it being specified that the reinforcement section is connected to the side wall (2, 2') by a reinforcement joint (8, 8 ')   parallel to and spaced from the upper edge.   5. Bag according to claim 4, characterized in that, inside each reinforcement section (7, 7 '),   a handle (9, 9 ') is fixed to the side wall (2, 2').   6. Bag according to any one of claims 1   to 5, characterized in that it consists of a sheet of   polyethylene at least 50 mm thick.   7. Bag according to any one of claims 1   to 6, characterized in that the polyethylene sheet is made from a mixture of raw materials composed of high density polyethylene, medium density polyethylene and linear low density polyethylene, the proportion of high density polyethylene being greater than that of medium density polyethylene and polyethylene linear low density.   8. Method for making bags of material   plastic according to any of the claims   previous, in which a sheet strip is folded to form a half-pipe (11) defining the side walls and divided by side seals whose spacing corresponds to the width of the bag and which extend transversely to the longitudinal direction of the demituyau, the bags thus formed being separated at the side seals,   characterized in that, after having formed by folding the half   pipe (11), a lower bellows (3) is formed which has two wall-forming sections (4, 4 '), which is directed inward and which is located between the side walls (2, 2'), in that that, at an interval equal to the width of the bag and coincidentally, the wall sections (4, 4 ') of the lower bellows (3) are welded, over the entire width of the latter, to the side walls (2, 2 ') respectively adjacent by a bias seal (6, 6', 12, 12 '), so that the bias seal forms with the lower edge (15) of the side walls an isosceles triangle, in that on the bisector between the two sides of the triangle, a continuous double seal (13) is welded which covers the lower bellows (3) and whose individual seals form the side seals (5, 5 ') of the bag (1), and in this we separate the bags   (1, la) between the individual joints.   9. Method according to claim 8, characterized in that, after having made the oblique joints (6, 6 ', 12, 12'), handles (9, 9 ') are welded on the upper edge (16) side walls (2, 2 ').