Method for fabricating a bag with a flat bottom, and a bag thus obtained

Abstract

A method for fabricating a bag with a flat bottom comprises: making a flattened tubular element with lateral bellows; obtaining a quadrilateral bottom of a single piece, the perimeter of which has a size equal to that given by the sum of the tubular element and the bellows; folding the bottom in a single piece along one of its first axes, keeping the outer sides parallel to the axis and of a size equal to the initial one; folding the other two sides to identify two opposite bellows, bringing a central folding line of the bellows thus identified into a position perpendicular to the first axis; inserting the bottom thus folded into the flattened tubular element, bringing the two opposite bellows of the bottom so that they are astride of the lateral bellows of the flattened tubular element; and welding the ends facing outwards of the flattened tubular element and of the corresponding lateral bellows respectively to the outer sides, which are parallel to the axis and are of a size equal to the initial size of the bellows and to the inner edges of the two opposite bellows obtained in the bottom. The bag has a quadrilateral bottom added to the tubular element and welded around the perimeter.

Description

[0001] The present invention relates to a method for fabricating a bag with a flat bottom and to a bag thus obtained.

[0002] In the field of automatic manufacture of bags, both bags with handles (shopping bags or shoppers) and without handles (open-mouthed bags), it is normal to use as starting material a continuous tubular element, which is, in general, made of thermoplastic material.

[0003] The aforesaid continuous tubular element is then provided, on its opposite longitudinal sides, with appropriate areas turned inwards, in the branch referred to herein as “bellows formation”, which enable it to be amply developed in an open condition and enable a bottom having a certain width to be obtained, but one that is not flat.

[0004] In fact, once the continuous tubular element provided with longitudinal side bellows formations is created, the next step in the process is to use an appropriately designed transverse welding rod, which functions intermittently, to form both the mouth (either opened or closed) of the bag and the weld for closing so as to obtain the bottom of the bag, blocking both the opposite sides of the flattened tubular element and the inner sides of the two bellows formations by means of a single weld.

[0005] The use of the above bags is by now fairly widespread and is bound to continue increasing. The aforesaid bags are also used for containing objects having a certain weight, even though they present a bottom of limited dimensions as compared to the transverse development that the bag may have given by the sum of the sides of the flattened tubular element and the size of the internal sides of the bellows all splayed out together.

[0006] There is consequently felt the need to make bags with wider bottoms, for example, bags with flat bottoms, which will present a certain degree of sturdiness and a certain degree of strength.

[0007] So far, no solution has been found to the above rather important technical problem.

[0008] The purpose of the present invention is therefore to identify a solution to the technical problem referred to above by making a bag with a wide flat bottom.

[0009] Another purpose of the invention is to provide a bag with a flat bottom that is particularly valid and that is able to perform the function outlined previously, which will be particularly simple to construct.

[0010] Yet a further purpose of the present invention is to provide a bag with a flat bottom which will be able to be manufactured automatically, without any need for manual intervention for its completion.

[0011] The above purposes according to the present invention are achieved by providing a bag with a flat bottom and by a method for fabrication thereof, as set forth in the attached independent claims.

[0012] Further salient characteristics and details of the present invention form the subject of the dependent claims.

[0013] The characteristics and advantages of a bag with a flat bottom and of a method for fabrication thereof according to the present invention will emerge more clearly from the ensuing description, which is provided purely by way of non-limiting example, of an embodiment thereof, with reference to the attached figures, in which:

[0014] FIG. 1 is a side view of a bag in a folded condition or position made according to the present invention;

[0015] FIG. 2 is a top plan view of a bottom element in a non-operative condition, laid out flat, which must then be included in the bag of FIG. 1 according to the present invention;

[0016] FIG. 3 is a perspective side view of the bottom element of FIG. 2 in a folded condition ready for being inserted within the initial tubular element having an external shape that is the same as the one illustrated in FIG. 1;

[0017] FIG. 4 is a perspective view, from beneath, of the bag of FIG. 1, when it is partially splayed out in an operative condition and is provided with the flat-bottom element illustrated in FIGS. 2 and 3; and

[0018] FIG. 5 illustrates an enlarged view of a closed bottom end portion of the bag of FIG. 1.

[0019] With reference to the various figures taken as a whole, there is illustrated in an altogether schematic way a bag with a flat bottom according to the invention, designated, as a whole, by 11 and obtained according to the method, which itself constitutes a novelty and inventive idea of the invention.

[0020] The bag with flat bottom 11 is obtained from a flattened tubular element 12 provided with lateral bellows formations 13 folded towards the inside of the tubular element itself.

[0021] The bag 11, which is illustrated finished, envisages an open mouth 14 and a quadrilateral bottom 15, having in the case illustrated by way of example in FIG. 4 a rectangular shape, even though the said quadrilateral bottom 15 may also be square.

[0022] In the folded condition, the bag 11 comprises a bottom element 16, which is inserted inside an open end of the flattened tubular element 12 with the free edges of both elements, towards the outside, set aligned and one on top of the other.

[0023] The bottom element 16 is made initially of a quadrilateral sheet (see FIG. 2), which is folded in a first direction into two halves along a first folding axis 17, keeping two external sides or parallel edges 18 parallel to said first folding axis 17 and so that they have a size that is equal to the initial size.

[0024] Next, in a second operating step carried out on the aforesaid bottom element 16, the further two sides 19 are folded in order to identify two opposite bellows 20 by bringing a central folding line 21 of said bellows 20 thus identified into a position perpendicular to said first axis 17.

[0025] Once the bottom element 16 has been folded as described above, said bottom element 16 is inserted into the aforesaid flattened tubular element 12 by bringing the two opposite bellows 20 of said bottom element 16 astride of the lateral bellows 13 of the flattened tubular element 12.

[0026] In this way, the configuration and arrangement illustrated in FIG. 1 is achieved, except for the weld. In fact, it is at this point that the step of welding the ends facing the outside of the flattened tubular element 12, opposite to the open mouth 14, with the corresponding ends of the lateral bellows 20 of the bottom elements 16 is carried out.

[0027] During the above operation, the outer sides 18 of the bottom element 16 parallel to the first folding axis 17 are kept so that the said sides 18 are set aligned with the end of the flattened tubular element 12. The weld is a perimetral weld, which constrains, in a first portion 22, the sides that remain in view of the flattened tubular element 12 with the sides 18 of the bottom element 16 and, in a second portion 23, the sides of the internal bellows 13 of the flattened tubular element 12 with the sides or internal edges of the two opposite internal bellows 20 of the bottom element 16; of course, this is done whilst the latter are set in the folded condition on top of each other.

[0028] A perimetral weld is then made between the sides and the end bellows of the flattened tubular element 12 and the sides and the bellows of the bottom element 16, so obtaining a bag, which, in the splayed-out and open condition has a quadrilateral flat bottom.

[0029] It is evident that a splayed-out and open bag provided with a quadrilateral flat bottom may be obtained also following steps other than the ones described previously, and hence the present invention also regards, in a much simpler manner, the said bag, irrespective of the method with which it is obtained.

[0030] It has thus been seen how the said bag with flat bottom and the method indicated according to the present invention achieve the purposes specified previously.

[0031] The method of fabrication of a bag with flat bottom, as well as the bag thus obtained according to the present invention, as conceived herein, may undergo numerous modifications and variations all falling within the scope of the same invention.

[0032] Furthermore, in practice, the materials used, as well as the dimensions and components, may be any whatsoever according to the technical requirements.

Claims

1. Bag with flat bottom obtained from a flattened tubular element (12) with side bellows (13), characterized in that said flat bottom is obtained from a bottom element (16), which is quadrilateral and has a perimetral weld, at the ends of the sides and of the bellows of said tubular element.

2. Bag with flat bottom according to claim 1, characterized in that said perimetral weld is made, in one of its first portions (22), between the sides in view of the flattened tubular element (12) with the first opposite sides (18) of said bottom element (16) and, in one of its second portions (23), between the sides of the internal bellows (13) of said flattened tubular element (12) with the remaining two sides or internal edges of two opposite internal bellows (20) of said bottom element (16).

3. Method for fabricating a bag with flat bottom, characterized in: making a flattened tubular element (12) with side bellows (13); obtaining a quadrilateral bottom of a single piece (15), the perimeter of which has a size equal to that given by the sum of said tubular element and said bellows; folding said bottom in a single piece along one of its first axes (17), keeping the outer sides (18) parallel to said axis (17) and of a size equal to the initial one; folding the other two sides (19) to identify two opposite bellows (20), bringing a central folding line (21) of said bellows thus identified into a position perpendicular to said first axis (17); inserting said bottom element (16) thus folded into said flattened tubular element (12), bringing said two opposite bellows (20) of said bottom so that they are astride of said lateral bellows (13) of said flattened tubular element (12); and welding the ends facing outwards of said flattened tubular element and of the corresponding lateral bellows respectively to said outer sides (18) which are parallel to said axis (17) and are of a size equal to the initial size of said bellows and to the internal edges of said two opposite bellows obtained in said bottom.

4. Method according to claim 3, characterized in that said bottom element (16) is obtained having a rectangular shape.