Method and apparatus for manufacturing packaging bags, and bags obtained thereby

Abstract

The present invention relates to a method of manufacturing packaging bags having lateral bellows, the method being characterized by the fact that it comprises the steps consisting in: forming respective cutouts (150, 160) in each of the two lateral, bellows-forming zones of a packaging bag sheet (100) so that the bag has only two thicknesses superposed at the mouth of said bellows, at least over a portion of its width; and heat-sealing (184, 186) the adjacent edges of the sheet to the peripheries of the cutouts (150, 160) to close the bag. The invention also provides apparatus for implementing the method and bags obtained thereby.

Description

[0001] The present invention relates to the field of bags for packaging.

[0002] Numerous packaging bags and numerous systems for manufacturing them have already been proposed.

[0003] For bags of small thickness, i.e. that are generally flat in the filled state, known means generally give satisfaction. Under such circumstances, the bags are generally formed using two plane sheets that are bonded together along three sides and that are provided with closure means, e.g. complementary male/female strips, at the mouth of a bag.

[0004] In contrast, until now, making bags that are intended to receive contents that are thick, has turned out not to be entirely satisfactory, even though a large amount of research has been performed in this very specific field.

[0005] In particular, such bags often require lateral bellows which are difficult to make.

[0006] Accompanying FIG. 1 shows, diagrammatically, a known technique for making bags with lateral bellows by inserting pre-formed bellows 10 between two sheets 12 and 14 that constitute two main faces of the bags, with the bellows being inserted at 90° to the travel direction S of said sheets. Said sheets 12 and 14 are provided with longitudinal male/female closure strips 13 and 15. The bellows 10 are preferably of varying width, increasing away from the closure strips 13 and 15 so as to enable the bags to be inflated. That known technique does indeed make it possible to make packaging bags having lateral bellows. Nevertheless, it turns out to be quite complex. In particular, the need to insert the bellows 10 at 90° to the travel direction of the sheets 12 and 14 does not enable high manufacturing throughputs to be obtained, and requires insertion of the bellows 10 to be adequately synchronized with the travel of the sheets 12 and 14.

[0007] Document FR-A-2 686 063 describes another technique of manufacturing packaging bags with bellows that consist in preforming a bag with lateral bellows, in splitting the bag over a portion of its length along fold lines external to the bellows, in folding the flaps defined in this way back over the outside of the bag, in placing the closure strips on said flaps, in reforming the bag, and in bonding the closure strips to said flaps that have been put into place. Unfortunately, because of its complexity, that technique does not give full satisfaction.

[0008] The Applicant has also described various alternative solutions for manufacturing packaging bags with lateral bellows in French patent application No. 96 02389 filed on Feb. 27, 1996.

[0009] The present invention now seeks to improve known means for manufacturing packaging bags having lateral bellows.

[0010] This object is achieved in the context of the present invention by a method of manufacturing packaging bags characterized by the fact that it comprises the steps consisting in:

[0011] forming respective cutouts in each of the two lateral, bellows-forming zones of a packaging bag sheet so that the bag has only two thicknesses superposed at the mouth of said bellows, at least over a portion of its width; and

[0012] heat-sealing the adjacent edges of the sheet to the peripheries of the cutouts to close the bag.

[0013] The present invention also provides apparatus for implementing the method, and bags obtained thereby.

[0014] Other characteristics, objects, and advantages of the invention will appear on reading the following detailed description and on looking at the accompanying drawings, given by way of non-limiting example and in which:

[0015] FIG. 1, described above, is a diagram showing a conventional technique of manufacturing packaging bags having lateral bellows;

[0016] FIG. 2 shows a first step of a method of the present invention consisting in forming two Z-folds in a film;

[0017] FIG. 3 is a cross-section view through the same film;

[0018] FIG. 4 is a view similar to FIG. 2 and shows the portion of film that is removed to form cutouts;

[0019] FIG. 5 shows the same film as provided with cutouts, when spread out flat;

[0020] FIG. 5bis is a similar flat view of a variant film of the present invention that is provided with cutouts; and

[0021] FIGS. 6 to 9 show four successive steps of the method of the present invention for forming bags.

[0022] In FIG. 2, there can be seen a film 100 provided with two Z-folds 110 and 120 that are parallel to the longitudinal direction D of the film 100.

[0023] The two Z-folds 110 and 120 can be formed by any appropriate means.

[0024] Each of them is preferably formed by means of two blades 200 & 202 or 200 & 204 that are superposed with partial overlap, as shown in FIG. 3, so as to form a baffle into which the film 100 is engaged.

[0025] The folds 110 and 120 are designed to form the lateral bellows of the bag once it has been completed.

[0026] After the folds 110 and 120 have been made, the film as shown in FIG. 2 has a plane main face 130 that is to form a main face of the bag after it has been completed. On its longitudinal edges, this main face 130 is extended on either side by first longitudinal flaps 112 and 122 which are themselves extended by second longitudinal flaps 114 and 124. The flaps 112 and 114 form the fold 110. The flaps 112 and 114 form the fold 120. The flaps 112 and 122 are connected to the main face 130 via fold lines 111 and 121. The flaps 112 and 122 are folded towards the middle of the face 130 from the fold lines 111 and 121 so that they underlie the main face 130. The flaps 114 and 124 are connected to the flaps 112 and 122 via fold lines 113 and 123. The flaps 114 and 124 extend outwards from the fold lines 113 and 123. The flaps 114 and 124 are also of the same length as the flaps 112 and 122 so as to underlie them respectively, being immediately beneath them. Finally, each of the flaps 114 and 124 is extended outwards by auxiliary segments 140 and 142. These auxiliary segments 140 and 142 are designed, in combination, to form the second main face of the bags. As shown in FIG. 2, the two segments 140 and 142 are preferably of identical width. Nevertheless, this condition is not essential. What is essential is that the segments 140 and 142 possess a total width that is slightly greater than the width of the face 130 so as to form the second face of the bags after they have been folded about their outer longitudinal free edges, as explained below with reference to FIG. 8.

[0027] After the step of forming the folds 110 and 120 as shown in FIG. 2, the flaps 114 and 124 are substantially coplanar with the segments 140 and 142. The flaps 114 and 124 are connected to the segments 140 and 142 via lines 115 and 125.

[0028] As mentioned above, according to an essential characteristic of the present invention, the method of forming a bag includes a step of cutting out pairs of cutouts 150 and 160 at regular intervals in each of the zones that is to form a lateral bellows.

[0029] The areas of material removed to form these cutouts 150 and 160 are shaded in FIG. 4.

[0030] The cutouts 150 and 160 are shown in the deployed state in FIG. 5.

[0031] Finally, the cutouts 150 and 160 are shown in their real configuration within the folds 110 and 120 in FIG. 6.

[0032] The cutouts 150 and 160 can be formed in the film 100 before making the folds 110 and 120. Under such circumstances, their initial shape is as shown in FIG. 5.

[0033] Nevertheless, it is preferable for the cutouts 150 and 160 to be formed after the folds 110 and 120 have been made. The cutouts 150 and 160 can be made in the film 100 by any appropriate means. The cutouts 150 and 160 are preferably made using the blade 200 as an anvil that co-operates with a cutting-out punch so as to leave the face 130 of the film intact.

[0034] The shapes of the cutouts 150 and 160 can vary in numerous ways.

[0035] The cutouts 150 and 160 preferably extend between the lines 111 and 115 on one side and the lines 121 and 125 on the other side, as shown in FIG. 5. Nevertheless, in a variant, as shown in FIG. 5bis, the cutouts 150 and 160 can be formed so as to be set back from the above-mentioned lines 111 & 115 and 121 & 125, as shown in FIG. 5bis.

[0036] More precisely, and as shown in the accompanying figures, each of the cutouts 150 and 160 is defined by two longitudinal edges 152 & 154 and 162 & 164, and by two transverse edges 156 & 158 and 166 & 168.

[0037] The longitudinal edges 152 & 154 and 162 & 164 are rectilinear and coincide respectively with the lines 111, 115, 121, and 125 in FIG. 5, which lines themselves constitute the final outer generator lines of the lateral bellows. In the folded state as shown in FIG. 6, the pairs of edges 152 & 154 or 162 & 164 are superposed.

[0038] The transverse edges 156 and 166 that are closer to the mouth of a bag are preferably rectilinear, extending transversely relative to the longitudinal direction D of the film 100.

[0039] The second transverse edges 158 and 168 that are closer to the bottom of a bag are preferably not rectilinear, being concave towards the mouth of the bag. More precisely, the second transverse edges 158 and 168 are preferably in the form of a dihedral made up of two rectilinear segments 158a & 158b or 168a & 168b. The above-mentioned pairs of segments 158a & 158b and 168a & 168b constituting respective second transverse edges 158 and 168 are preferably identical in length. They extend respectively over the flaps 112 & 114 and 122 & 124. In this way, the segments 158a & 158b and 168a & 168b intersect on the middle fold lines 113 and 123.

[0040] As a non-limiting example, the segments 158a & 158b and 168a & 168b are inclined by about 15° relative to a line extending transversely to the longitudinal direction D, such that the dihedral angle formed between the pairs of segments 158a & 158b and 168a & 168b is about 150°.

[0041] The generally plane film 100 together with its two Z-folds 110 and 120 and provided with its two cutouts 150 and 160 as shown in FIGS. 5 and 5bis is preferably fed directly to a conventional form, fill, and seal machine for making bags.

[0042] Such machines are often referred to as “FFS” machines, from the initials of the term “form, fill, and seal”.

[0043] Numerous machines of this type have already been proposed.

[0044] Most such machines have: a forming throat which has an input receiving the film in the flat state and which has an output delivering the film shaped into a tube; a filling chute which opens out into the forming throat and consequently into said tube; longitudinal heat-sealing means for closing the tube longitudinally; and means suitable for acting sequentially to generate a first transverse line of heat-sealing before substance is inserted into the tube via the filling chute, and then a second transverse line of heat-sealing once the substance has been inserted into the tube, so as to close the bag around the substance.

[0045] The general structure of such machines is well known to the person skilled in the art, so the structure is not described in detail below.

[0046] It will be observed that in the context of the present invention, it is preferable for complementary male/female closure strips 170 to be deposited on the film 100 in the vicinity of the mouth zone of a bag transversely to the longitudinal direction D, and prior to the film 100 being brought to the forming throat of the FFS machine, as shown in FIG. 7.

[0047] Still more precisely, closure strips 170 are placed against the main face 130 facing the cutouts 150 and 160, i.e. between the transverse edges 156 and 158 at one end and 166 and 168 at the other.

[0048] The closure strips 170 are preferably of a length that is equal to the width of the main face 130, i.e. the distance between the fold lines 111 and 121.

[0049] After being placed on the film 100, the strips 170 are secured in position on the film 100 by any appropriate means. Preferably, after they have been put into place, the strips 170 are initially fixed to the film 100 solely via their ends using a spot heat-sealing technique. The strips 170 are subsequently fixed to the main faces of the bag over the full length of their inside faces, preferably when making the transverse lines of heat-sealing in the manner described below with reference to FIG. 9. When the strips 170 are secured by spot heat-sealing at their ends, the lateral edges of the bag facing the folds 110, 120 can also be secured by spot heat-sealing at the zones where the transverse lines of heat-sealing shown in FIG. 9 will subsequently be made for holding the above-mentioned folds together and preventing them from deforming as the film 100 moves on.

[0050] Nevertheless, in a variant, at least one of the strips 170 may be heat-sealed to the film 100 along its entire length as soon as it is put into place.

[0051] The above-mentioned means for spot heat-sealing are preferably adjustable along the length of the film 100 so as to make it possible for them to be adjusted accurately relative to the desired length for the bags and to the zones that will subsequently correspond to the transverse lines of heat-sealing.

[0052] Naturally, it is also necessary to synchronize carefully the instant at which said spot heat-sealing means are operated relative to the travel of the film 100, since the instants at which said spot heat-sealing means operate determine both the locations of the corresponding heat-sealing zones and the pitch of said zones.

[0053] By fixing the closure strips 170 via their ends, and possibly also by fixing the folds 110 and 120 by spot heat-sealing, subsequent travel of the film 100 is made easier and it is also easier subsequently to perform the heat-sealing as shown in FIG. 9, particularly because of the resulting crushing of the ends of the strips 170.

[0054] The means for making the above-mentioned spots of heat-sealing can be generally like the means described in document FR-A-2 638 419.

[0055] In a variant, the closure strips 170 are fixed, and the folds 110 and 120 are held temporarily by spots that are not made by heat-sealing, but are made by any equivalent means, such as by static discharge or by spots of adhesive.

[0056] The means designed for depositing the closure strips 170 on the film 100 so that they extend transversely to the longitudinal direction D of the film 100 can be implemented in numerous ways.

[0057] By way of non-limiting examples, these means may be like the means described in the following documents: U.S. Pat. No. 4,617,683, U.S. Pat. No. 4,655,862, U.S. Pat. No. 4,666,536, U.S. Pat. No. 4,701,361, U.S. Pat. No. 4,709,398, U.S. Pat. No. 4,878,987, U.S. Pat. No. 4,844,759, U.S. Pat. No. 4,929,225, U.S. Pat. No. 4,909,017, and U.S. Pat. No. 5,111,643.

[0058] Once the folds 110 and 120 have been made and the closure strips 170 have been put into place and secured, at least temporarily, the film assembly 100 as shown in FIG. 7 is sent to the forming throat of an FFS machine, as mentioned above.

[0059] Where appropriate, special means may be provided at the forming throat to facilitate passage thereover, in particular of the folds 110, 120. By way of example, complementary windows may be provided on the forming throat to receive the folds 110 and 120.

[0060] On leaving the forming throat, the film 100 is shaped into a tubular state, as shown in FIG. 8. The outer free edges 141 and 143 of the segments 140 and 142 are then brought together and heat-sealed in conventional manner by the above-mentioned longitudinal heat-sealing means of the FFS machine.

[0061] The tubular film is then filled with its content via the filling chute provided for this purpose.

[0062] The tubular film is then brought to face the heat-sealing means provided for making the lines of heat-sealing shown in FIG. 9.

[0063] The following are then preferably provided at these heat-sealing means:

[0064] two mutually parallel lines of heat-sealing 180 and 182; and

[0065] respective lines of heat-sealing 184 and 186 at the peripheries of the cutouts 150 and 160.

[0066] One of the transverse lines of heat-sealing 180 coincides with the transverse edges 156 and 166 of the cutouts. This transverse line of heat-sealing 180 is designed to form the bottom of a bag. In the lateral bellows, it serves to connect together four thicknesses of film (the two main faces and the lateral bellows) and between the bellows it connects together two thicknesses of film (corresponding to the main faces).

[0067] The other transverse line of heat-sealing 182 is made between the transverse edges 156 & 158 and 166 & 168 of the cutouts. This transverse line of heat-sealing 182 is designed to form the mouth of a bag. It interconnects the two main faces.

[0068] Once the lines of heat-sealing 180 and 182 have been made, a transverse rectilinear line of cut 181 can be formed between them to separate two adjacent bags.

[0069] The lines of heat-sealing 184 and 186 are respectively made up of pairs of segments 184a & 184b and 186a & 186b respectively covering the longitudinal edges 152 & 154 and 162 & 164 and also the transverse edges 158 and 168 of the cutouts.

[0070] In this way, the lines of heat-sealing 184, 182, and 186 intersect, thereby ensuring that the mouth of a bag is properly sealed. More precisely, the segments 184a and 186a connect together the outside edges of the two main faces of the bag, while the segments 184b and 186b connect together the edges 158a & 158b and the edges 168a & 168b.

[0071] The method of the present invention has the fundamental advantage of limiting the lines of heat-sealing 184, 182, and 186 to two thicknesses of film, in particular where the closure strips 170 are fixed thereto, whereas most conventional methods need to perform heat-sealing through four thicknesses of film at the lateral bellows.

[0072] Naturally, the present invention is not limited to the embodiment described above, but extends to any variant coming within the spirit thereof.

[0073] For example, it is possible to make bags using a film of the type shown in FIG. 7 having cutouts 150, 160 and closure strips 170, without applying the film to a form, fill, and seal machine as mentioned above. The film can then be shaped to have a tubular state by any appropriate conventional means.

[0074] In the context of the present invention, the film 100 can be varied in numerous ways. It is preferably constituted by a thermoplastic film. Nevertheless, the invention applies to any flexible film that can be used for making a packaging bag.

[0075] Furthermore, the person skilled in the art will understand that although, in the example shown in FIG. 5, the longitudinal edges 152, 154, 162, and 164 of the cutouts 150 and 160 coincide with the fold lines 111, 115, 121, and 125, so that the lines of heat-sealing 184a and 186a are made on two thicknesses of film, when the longitudinal edges 152, 154, 162, 164 of the cutouts 150 and 160 are set back from the fold lines 111, 115, 121, and 125, then the lines of heat-sealing 184a and 186a are made, at least in part, on four superposed thicknesses of film. The same applies for end portions of the transverse lines of heat-sealing 180 and 182. The lines of heat-sealing 184a and 186a may also be made at least in part so as to be set back from the fold lines 111, 115, 121, and 125, as shown in FIG. 9. The variant embodiment of the cutouts as shown in FIG. 5bis makes it possible to improve the lateral sealing of the bags.

Claims

1. A method of manufacturing packaging bags having lateral bellows, the method being characterized by the fact that it comprises the steps consisting in:

forming respective cutouts (150, 160) in each of the two lateral, bellows-forming zones of a packaging bag sheet (100) so that the bag has only two thicknesses superposed at the mouth of said bellows, at least over a portion of its width; and

heat-sealing (184, 186) the adjacent edges of the sheet to the peripheries of the cutouts (150, 160) to close the bag.

2. A method according to

claim 1, characterized by the fact that it includes the step consisting in making two Z-folds (110, 120) parallel to the longitudinal direction (D) of the film (100).

3. A method according to

claim 2, characterized by the fact that each of the Z-folds (110, 120) is formed by means of two blades (200, 202, 200, 204) that are partially superposed to overlap so as to form a baffle in which the film (100) is engaged.

4. A method according to

claim 2 or

3, characterized by the fact that the cutouts (150, 160) are formed after the folds (110, 120) have been formed.

5. A method according to

claim 2 or

3, characterized by the fact that the cutouts (150, 160) are formed before the folds (110, 120) are formed.

6. A method according to

claim 3, characterized by the fact that the cutouts (150 and 160) are formed using one of the fold-forming blades (200) as an anvil for a cutting-out punch, thereby leaving one of the faces (130) of the film untouched.

7. A method according to any one of

claims 2 to

6, characterized by the fact that after the folds (110, 120) have been made, the film has a plane main face (130) extended on either side at its longitudinal edges by first longitudinal flaps (112, 122), which are themselves extended by second longitudinal flaps (114, 124), which are in turn extended outwards by auxiliary segments (140, 142).

8. A method according to any one of

claims 1 to

7, characterized by the fact that each cutout (150, 160) is defined by two rectilinear longitudinal edges (152 & 154, 162 & 164) coinciding respectively with the outer generator lines of the lateral bellows, a rectilinear transverse edge (156, 166) extending transversely to the longitudinal direction (D) of the film (100), and a second transverse edge (158, 168) that is not rectilinear, being concave towards the mouth of the bag.

9. A method according to any one of

claims 1 to

7, characterized by the fact that each cutout (150, 160) is defined by two rectilinear longitudinal edges (152 & 154, 162 & 164) situated respectively set back from the outer generator lines of the lateral bellows, a rectilinear transverse edge (156, 166) extending transversely to the longitudinal direction (D) of the film (100), and a second transverse edge (158, 168) that is not rectilinear, being concave towards the mouth of a bag.

10. A method according to

claim 8 or

9, characterized by the fact that the second transverse edge (158, 168) is constituted by a dihedral made up of two rectilinear segments (158a & 158b, and 168a & 168b).

11. A method according to any one of

claims 1 to

10, characterized by the fact that the film (100) provided with two Z-folds (110, 120) and fitted with two cutouts (150, 160) is shaped using a form, fill, and seal machine.

12. A method according to

claim 11, characterized by the fact that the form, fill, and seal machine has a forming throat whose input receives the film (100) in the flat state and whose output delivers the film shaped into a tube, a filling chute which opens out into the forming throat and consequently into said tube, longitudinal heat-sealing means for closing the tube longitudinally, and means suitable for sequentially generating transverse lines of heat-sealing to close a bag.

13. A method according to any one of

claims 1 to

12, characterized by the fact that it further comprises the step consisting in placing complementary male/female closure strips (170) on the film (100) in the mouth zone of a bag, transversely to the longitudinal direction (D), facing the cutouts (150 and 160).

14. A method according to

claim 13, characterized by the fact that the strips (170) are initially held in position on the film (100) by spot heat-sealing at their ends.

15. A method according to

claim 2, characterized by the fact that the folds (110, 120) are fixed by spot heat-sealing at the zones where the transverse lines of heat-sealing are to be formed.

16. A method according to any one of

claims 1 to

15, characterized by the fact that it comprises the steps consisting in making:

two mutually parallel transverse lines of heat-sealing (180, 182), one coinciding with a transverse edge (156, 166) of each cutout to form the bottom of a bag, the other being made between the transverse edges (156 & 158, 166 & 168) of the cutouts to form the mouth of a bag; and

additional lines of heat-sealing (184, 186) each formed by two segments (184a & 184b, 186a & 186b) respectively covering the longitudinal edges (152 & 154, 162 & 164) of the cutouts and also the transverse edges (158 and 168) of the cutouts.

17. A method according to

claim 16, characterized by the fact that a rectilinear line of cut (181) is formed between the two transverse lines of heat-sealing (156, 166) to separate two adjacent bags.

18. A machine for manufacturing packaging bags having lateral bellows to implement the method according to any of

claims 1 to

17, the machine being characterized by the fact that it comprises:

means suitable for forming respective cutouts (150, 160) in each of the two zones forming lateral bellows of a sheet (100) for a packaging bag, such that the bag has only two superposed thicknesses at the mouths of said bellows, at least over a fraction of its width; and

means (184, 186) suitable for heat-sealing together the adjacent edges of the sheet at the peripheries of the cutouts (150, 160) to close the bag.

19. A machine according to

claim 18, characterized by the fact that it includes means for forming two Z-folds (110, 120) parallel to the longitudinal direction (D) of the film (100).

20. A machine according to

claim 19, characterized by the fact that it includes two partially superposed blades (200, 202, 200, 204) that overlap to form a baffle into which the film (100) is engaged to form the folds (110, 120).

21. A machine according to

claim 20, characterized by the fact that one of the fold-forming blades (200) forms an anvil for a cutting-out punch when making the cutouts (150, 160), thereby leaving one of the faces (130) of the film intact.

22. A machine according to any one of

claims 18 to

21, characterized by the fact that each cutout (150, 160) is defined by two rectilinear longitudinal edges (152 & 154, 162 & 164) respectively coinciding with the outer generator lines of the lateral bellows, a rectilinear transverse edge (156, 166) extending transversely to the longitudinal direction (D) of the film (100), and a second transverse edge (158, 168) that is not rectilinear, being concave towards the mouth of the bag.

23. A machine according to any one of

claims 18 to

21, characterized by the fact that each cutout (150, 160) is defined by two rectilinear longitudinal edges (152 & 154, 162 & 164) situated so as to be set back respectively from the outer generator lines of the lateral bellows, a rectilinear transverse edge (156, 166) extending transversely to the longitudinal direction (D) of the film (100), and a second transverse edge (158, 168) that is not rectilinear, being concave towards the mouth of the bag.

24. A machine according to

claim 22 or

23, characterized by the fact that the second transverse edge (158, 168) constitutes a dihedral made up of two rectilinear segments (158a & 158b, 168a & 168b).

25. A machine according to any one of

claims 18 to

24, characterized by the fact that it constitutes a form, fill, and seal machine.

26. A machine according to any one of

claims 18 to

25, characterized by the fact that it includes a forming throat having an inlet that receives the film (100) in the plane state, and an outlet that delivers the film shaped into a tube, a filling chute which opens out into the forming throat and consequently into said tube, longitudinal heat-sealing means for closing the tube longitudinally, and means suitable for sequentially generating transverse lines of heat-sealing to close a bag.

27. A machine according to any one of

claims 18 to

26, characterized by the fact that it further comprises means suitable for placing complementary male/female closure strips (170) on the film (100) in the mouth zone of a bag, the strips extending transversely to the longitudinal direction D and facing the cutouts (150 and 160).

28. A machine according to

claim 27, characterized by the fact that it includes means suitable for securing the strips (170) initially in position on the film (100) by spot heat-sealing at their ends.

29. A machine according to any one of

claims 18 to

28, characterized by the fact that it includes means suitable for fixing the folds (110, 120) by spot heat-sealing in the zones that are subsequently to include the transverse lines of heat-sealing.

30. A machine according to any one of

claims 18 to

29, characterized by the fact that it comprises heat-sealing means suitable for making:

two mutually parallel transverse lines of heat-sealing (180, 182), one coinciding with a transverse edge (156, 166) of each cutout to form the bottom of a bag, the other being made between the transverse edges (156 & 158, 166 & 168) of the cutouts to form the mouth of a bag; and

additional lines of heat-sealing (184, 186) each made up of two segments (184a & 184b, 186a & 186b) respectively covering the longitudinal edges (152 & 154 and 162 & 164) and the transverse edges (158 and 168) of the cutouts.

31. A machine according to

claim 30, characterized by the fact that it comprises means suitable for making a rectilinear line of cut (181) between the two transverse lines of heat-sealing (156, 166) to separate two adjacent bags.

32. A packaging bag having lateral bellows made by implementing the method according to any one of

claims 1 to

17.

33. A bag according to

claim 32, characterized by the fact that it includes respective cutouts (150, 160) in each of the two zones forming lateral bellows and a line of heat-sealing (184, 186) on the periphery of the cutouts (150, 160) to close the bag.