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 stepsof 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

FIELD OF THE INVENTION

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

BACKGROUND OF THE INVENTION

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

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

[0004] In contrast, until now, manufacturing 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 manufacturing 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 the sheets 12, 14. The 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 manufacture 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 consists 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 the flaps, in reforming the bag, and in bonding the closure strips to the flaps that have been put into place. Unfortunately, because of its complexity, that technique does not provide 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.

OBJECT OF THE INVENTION

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

SUMMARY OF THE INVENTION

[0010] The foregoing object is achieved in the context of the present invention by a method of manufacturing packaging bags comprising the steps of:

[0011] providing a packaging bag sheet, having a longitudinal extent, for forming a packaging bag;

[0012] folding said packaging bag sheet so as to form a pair of laterally spaced bellow regions within side edge portions of said packaging bag sheet;

[0013] forming cutouts within each one of said pair of laterally spaced, bellow regions of said packaging bag sheet so that saidbag has only two sheet thicknesses superposed with respect to each other within a mouth region of said bellows

[0014] placing complementary male/femelle closure strips provided with a control cursor upon said packaging bag sheet within the vicinity of said mouth region of said bag and transversely with respect to said longitudinal feeding direction and

[0015] heat-sealing edges portions of said sheet edge portions of said cutouts so as to close and seal said bag.

[0016] In the context of the present invention, the complementary male/female closure strips are preferably provided on respective main support walls which are adapted to be fixed on the packaging bag sheet and which are connected together by an auxiliary wall adapted to be broken when the bag is opened the first time.

[0017] The present invention also provides apparatus for implementing the method, and bags obtained thereby.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Other characteristics, objects, and advantages of the invention will become apparent upon reading the following detailed description and upon looking at the accompanying drawings, given by way of non-limiting example and in which like reference characters designate like or corresponding parts throughout the several views and wherein:

[0019] FIG. 1, described above, is a diagram showing a conventional technique of manufacturing packaging bags having lateral bellows;

[0020] FIG. 2 is a top plan view which shows a first step of a method of the present invention consisting in forming two Z-folds in a film;

[0021] FIG. 3 is a cross-section view through the film of FIG. 1;

[0022] FIG. 4 is a view similar to FIG. 2 and shows the portion of film that is removed to form cutouts;

[0023] FIG. 5 shows the film of FIG. 4 as provided with cutouts, when spread out flat;

[0024] FIG. 5a is a similar flat view of a variant film of the present invention that is provided with cutouts;

[0025] FIGS. 6 to 9 show four successive steps of the method of the present invention for forming bags;

[0026] FIG. 10 is a schematic view in perspective of a cursor of the present invention,

[0027] FIG. 11 is a longitudinal cross-section view of the cursor through the section plan referenced XI-XI on FIG. 10,

[0028] FIG. 12 is a first transverse cross-section view of the cursor through the section plan referenced XII-XII on FIGS. 10 and 11 and

[0029] FIG. 13 is a second transverse cross-section viewof the cursor through the section plan referenced XIII-XIII on FIGS. 10 and 11.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0030] 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.

[0031] The two Z-folds 110 and 120 can be formed by any appropriate means.

[0032] 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.

[0033] The folds 110 and 120 are designed to form the lateral bellows of the bag once it has been completed.

[0034] After the folds 110 and 120 have been made, the film as shown in FIG. 2 has a planar 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 122 and 124 form the fold 120. The flaps 112 and 122 are connected to the main face 130 by means of 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 by means of 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.

[0035] 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 by means of lines 115 and 125.

[0036] 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.

[0037] The areas of material removed to form these cutouts 150 and 160 are shaded in FIG. 4.

[0038] The cutouts 156 and 160 are shown in the deployed state in FIG. 5.

[0039] Finally, the cutouts 150 and 160 are shown in their real configuration within the folds 110 and 120 in FIG. 6.

[0040] 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.

[0041] 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.

[0042] The shapes of the cutouts 150 and 160 can vary in numerous ways.

[0043] 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. 5a, 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. 5a.

[0044] 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.

[0045] 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.

[0046] The transverse edges 156 and 166 that are closer to the mouth of the bag are preferably rectilinear, extending transversely relative to the longitudinal direction D of the film 100.

[0047] 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.

[0048] 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 150ø.

[0049] The generally planar 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 5a is preferably fed directly to a conventional form, fill, and seal machine for making bags.

[0050] Such machines are often referred to as “FFS” machines, from the initials of the terms “form, fill, and seal”.

[0051] Numerous machines of this type have already been proposed.

[0052] 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 the formed 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 material is inserted into the tube by means of the filling chute, and then a second transverse line of heat-sealing once the material has been inserted into the tube, so as to close the bag around thematerial.

[0053] 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.

[0054] As mentioned above, according to an essential characteristic of the present invention, the male/female closure strips 170 are provided with a control cursor 1710.

[0055] As illustrated on FIGS. 10, 12 and 13, preferably the male/female closure strips comprise a male/profile 172 provided on a first main wall 174 and a female profile 176 provided on a second main wall 178.

[0056] In a variant the male profile 172 and the female profile 176 may be replaced by equivalent complementary hooked means.

[0057] The two main walls 174 and 178 are adapted to be fixed on the packaging bag sheet 100.

[0058] According to a preferential embodiment of the invention, as illustrated on FIG. 10, the two main walls 174, 178 are initially connected by an auxiliary wall 179. This auxiliary wall 179 is adapted to be broken when the bag is opened the first time. Thus the auxiliary wall 179 is an evidence of an opening of the bag when it is broken.

[0059] Generally the cursor 1710 has two lateral flanges 1712, 1714 interconnected by means of a web 1716 and which co-operate with an elongate central tongue 1718 placed between the closure strips 172, 176 to define two converging passages 1720, 1722 for the interfittable complementary closure strips 172, 176. The central tongue 1718 extends only on a part of the cursor 1710. Thus, when the direction of displacement of the cursor 1710 relative to the closure strips 172, 176 tends to force the closure strips 172, 176 into engagement, the bag is closed. In contrast, when the cursor 1710 is displaced in the opposite direction, the bag is opened by means of the central tongue 1718 separating the closure strips 172, 176.

[0060] 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

[0061] Still more precisely, closure strips 170 are placed against the main face 130 facing the cutouts 150 and 160, that is between the transverse edges 156 and 158 at one end and 166 and 168 at the other end.

[0062] The closure strips 170 are preferably of a length that is equal to the width of the main face 130, that is the distance between the fold lines 111 and 121.

[0063] 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 by means of 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.

[0064] 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.

[0065] 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.

[0066] Naturally, it is also necessary to synchronize carefully the instant at which the spot heat-sealing means are operated relative to the travel of the film 100, since the instants at which the spot heat-sealing means operate determine both the locations of the corresponding heat-sealing zones and the pitch of the zones.

[0067] By fixing the closure strips 170 by means of 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 to subsequently perform the heat-sealing as shown in FIG. 9, particularly because of the resulting crushing of the ends of the strips 170.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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. Nos. 4,655,862, 4,666,536, 4,701,361, 4,709,398, 4,878,987, 4,844,759, 4,929,225, 4,909,017, and U.S. Pat. No. 5,111,643.

[0072] 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.

[0073] 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.

[0074] On leaving the forming throat, the film 100 is shaped into a tubular state, as shown in FIG. 8. The laterally outer free edges 141 and 143 of the segments 140 and 142 are then brought together and heat-sealed in a conventional manner by the above-mentioned longitudinal heat-sealing means of the FFS machine.

[0075] The tubular film is then filled with its content by means of the filling chute provided for this purpose.

[0076] The tubular film is then brought to face the heat-sealing means provided for making the lines of heat-sealing shown in FIG. 9.

[0077] The following are then preferably provided at these heat-sealing means:

[0078] two mutually parallel lines of heat-sealing 180 and 182; and

[0079] respective lines of heat-sealing 184 and 186 at the peripheries of the cutouts 150 and 160.

[0080] One of the transverse lines of heal-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, that is, the two main faces and the lateral bellows, and between the bellows it connects together two thicknesses of film corresponding to the main faces.

[0081] 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.

[0082] Once the lines of heat-sealing 180 and 182 have been made, a transverse rectilinear cut line 181 can be formed between them so as to separate two adjacent bags.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] Naturally, the present invention is not limited to the embodiment described above, but extends to any variant coming within the spirit thereof.

[0087] 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.

[0088] 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.

[0089] 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. 5a makes it possible to improve the lateral sealing of the bags.

[0090] Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claim, the present invention may be practiced otherwise than as specifically described herein.

Claims

1. A method of manufacturing packaging bags comprising the steps of:

providing a packaging bag sheet, having a longitudinal extent, for forming a packaging bag;

folding said packaging bag sheet so as to form a pair of laterally spaced bellow regions within side edge portions of said packaging bag sheet;

forming cutouts within each one of said pair of laterally spaced, bellow regions of said packaging bag sheet so that said bag has only two sheet thicknesses superposed with respect to each other within a mouth region of said bellows;

placing complementary male/femelle closure strips provided with a control cursor upon said packaging bag sheet within the vicinity of said mouth region of said bag and transversely with respect to said longitudinal feeding direction; and

heat-sealing edges portions of said sheet to edge portions of said cutouts so as to close and seal said bag.

2. A method according to

claim 1, wherein said cursor has two lateral flanges interconnected by means of a web and which co-operate with an elongate central tongue placed between the closure strips to define two converging passages for the closure strips.

3. A method according to

claim 1, wherein the closure strips are provided on respective main support walls which are adapted to be fixed on the packaging bag sheet and which are connected together by an auxiliary wall adapted to be broken when the bag is opened the first time.

4. A method according to

claim 1, further comprising the steps of:

feeding said packaging bag sheet in a direction parallel to said longitudinal extent of said packaging bag sheet; and

forming said pair of laterally spaced bellow regions by making two Z-folds which extend parallel to said longitudinal feeding direction of the said packaging bag sheet.

5. A method according to

claim 4, wherein:

each one of said Z-folds is formed by a pair of blades that are partially superposed with respect to each other so as to partially overlap each other and thereby form a baffle within which a side edge portion of said packaging bag sheet is engaged.

6. A method according to

claim 4, wherein:

said cutouts are formed within said pair of laterally spaced bellow regions after said folds have been formed within said packaging bag sheet so as to form said pair of laterally spaced bellow regions.

7. A method according to

claim 4, wherein:

said cutouts are formed within said pair of laterally spaced bellow regions before said folds are formed within said packaging bag sheet so as to form said pair of laterally spaced bellow regions.

8. A method according to

claim 5, wherein:

said cutouts are formed within said pair of laterally spaced bellow regions by using one of said pair of fold-forming blades as an anvil for a cutting-out punch thereby leaving one of the faces of said packaging bag sheet intact.

9. A method according to

claim 1, further comprising the step of:

initially holding said complementary closure strips in position upon said packaging bag sheet by spot heat-sealing ends of said closure strips to said packaging bag sheet.

10. A method according to

claim 4, further comprising the step of:

fixing said Z-folds by spot heat-sealing said Z-folds at zones where transverse lines of heat-sealing are to be formed so as to close said bag.

11. A method according to

claim 10, wherein said formation of said transverse lines of heat-sealing comprises the step of:

forming two mutually parallel transverse lines of heat-sealing such that one of said transverse lines of heat-sealing forms the bottom of a bag while the other one of said transverse lines of heat-sealing forms the mouth of a bag.

12. A method according to

claim 11, further comprising the step of:

forming a rectilinear cut line between said two transverse lines of heat-sealing so as to separate said formed packaging bag into two separate adjacent bags.

13. A machine for manufacturing packaging bags from packaging bag sheets, comprising:

means for feeding a packaging bag sheet having a longitudinal extent;

means for folding said packaging bag sheet so as to form a pair of laterally spaced bellow regions within side edge portions of said packaging bag sheet;

means for forming cutouts within each one of said pair of laterally spaced bellow regions of said packaging bag sheet such that said packaging bag has only two superposed sheet thicknesses within a mouth region of said bellows;

means for placing complementary male/femelle closure strips provided with a control cursor upon said packaging bag sheet within the vicinity of said mouth region of said bag such that said closure strips extend transversely with respect to said longitudinal extent of said packaging bag sheet;and

means for heat-sealing together edges portions of said packaging bag sheet to edge portions of said cutouts so as to close and seal said bag.

14. A machine according to

claim 13 wherein said cursor has two lateral flanges interconnected by means of a web and which co-operate with an elongate central tongue placed between the closure strips to define two converging passages for the closure strips.

15. A machine according to

claim 13 wherein the closure strips are provided on respective main support walls which are adapted to be fixed on the packaging bag sheet and which are connected together by an auxiliary wall adapted to be broken when the bag is opened the first time.

16. A machine according to

claim 13, further comprising:

means for forming said pair of laterally spaced bellow regions so as to comprise a pair of Z-folds which extend parallel to said longitudinal extent of said packaging bag sheet.

17. A machine according to

claim 16, wherein:

said means for forming said pair of laterally spaced bellow regions comprises two partially superposed blades that overlap each other and thereby form a baffle into which said packaging bag sheet is engaged so as to form said pair of Z-folds.

18. A machine according to

claim 17, further comprising:

a cut-out punch; and

one of said fold-forming blades comprises an anvil for said cut-out punch when said cut-out punch is used to make said cutouts so as to leave one of the faces of said packaging bag sheet intact.

19. A machine according to

claim 13, wherein:

said machine comprises a form, fill, and seal machine.

20. A machine according to

claim 19, wherein said form, fill, and seal machine comprises:

a forming throat having an inlet that receives said packaging bag sheet in a planar state, and an outlet that delivers said packaging bag sheet shaped into a tube,

a filling chute which opens out into said forming throat and consequently into said tube so as to deposit material into said tube,

longitudinal heat-sealing means for closing and sealing said tube longitudinally, and

means for sequentially generating transverse lines of heat-sealing so as to close and seal said formed bag.

21. A machine according to

claim 13, further comprising:

means for initially securing said closure strips in position upon said packaging bag sheet by spot heat-sealing ends of said closure strips to said packaging bag sheet.

22. A machine according to

claim 16, further comprising:

means for fixing said Z-folds by spot heat-sealing said Z-folds at zones that are subsequently to include transverse lines of heat-sealing so as to close and seal said bag.

23. A machine according to

claim 22 further comprising:

heat-sealing means for forming two mutually parallel transverse lines of heat-sealing such that one of said transverse line of heat-sealing forms the bottom of a bag while the other one of said transverse lines of heat-sealing forms the mouth of a bag.

24. A machine according to

claim 23, further comprising:

means for forming a rectilinear cut line between said two transverse lines of heat-sealing so as to separate said formed packaging bag into two separate adjacent bags.

25. A packaging bag comprising:

a folded packaging sheet, having a longitudinal extent, for forming a packaging bag;

a pair of laterally spaced bellows formed within side edge portions of said folded packaging bag sheet;

cutout portions respectively formed within each one of said pair of laterally spaced bellows so that said packaging bag has only two sheet thickness superimposed with respect to each other within a mouth region of said bag;

complementary male/female closure strips provided with a control cursor upon said packaging bag sheet within the vicinity of said mouth region of said bag such that said closure strips extend transversely with respect to said longitudinal exent of said packaging sheet; and

heat-sealed regions for closing and sealing said packaging bag.

26. A bag according to

claim 25, wherein:

said heat-sealed regions of said packaging bag comprises a line of heat-sealing defined between edge portions of said packaging bag sheet and edge portions of said cutouts.

27. A packaging bag as set forth in

claim 25, wherein said packaging bag sheet comprises:

a planar main face;

first longitudinal flaps disposed upon and integrally connected to opposite sides of said planar main face;

second longitudinal flaps disposed upon and integrally connected to opposite sides of said first longitudinal flaps, and

auxiliary segments disposed upon and integrally connected to said second longitudinal flaps.

28. A packaging bag as set forth in

claim 25, wherein:

each cutout portion is defined by two rectilinear longitudinal edges coinciding respectively with outer definition lines of said laterally spaced bellows, a rectilinear transverse edge extending transversely to said longitudinal extent of said packaging bag sheet, and a second transverse edge that is not rectilinear and is concave towards said mouth region of said bag.

29. A packaging bag as set forth in

claim 25, wherein:

each cutout portion is defined by two rectilinear longitudinal edges which are respectively set back from the outer definition lines of said laterally spaced bellows, a rectilinear transverse edge extending transversely to said longitudinal extent of said packaging bag sheet, and a second transverse edge that is not rectilinear and is concave towards said mouth region of said bag.

30. A packaging bag as set forth in

claim 28, wherein:

said second transverse edge comprises a dihedral made up of two rectilinear segments.

31. A packaging bag comprising:

a folded packaging sheet, having a longitudinal extent, for forming a packaging bag;

a pair of laterally spaced bellows formed within side edge portions of said folded packaging bag sheet;

cutout portions respectively formed within each one of said pair of laterally spaced bellows so that said packaging bag has only two sheet thickness superimposed with respect to each other within a mouth region of said bag;

complementary male/female closure strips provided with a control cursor upon said packaging bag sheet within the vicinity of said mouth region of said bag such that said closure strips extend transversely with respect to said longitudinal exent of said packaging sheet; and

heat-sealed regions for closing and sealing said packaging bag,

each one of said cutout portions being defined by two rectilinear longitudinal edges coinciding respectively with outer definition lines of said laterally spaced bellows, a rectilinear transverse edge extending transversely to said longitudinal extent of said packaging bag sheet, and a second transverse edge that is not rectilinear and is concave towards said mouth region of said bag.

32. A packaging bag comprising:

a folded packaging sheet, having a longitudinal extent, for forming a packaging bag;

a pair of laterally spaced bellows formed within side edge portions of said folded packaging bag sheet;

cutout portions respectively formed within each one of said pair of laterally spaced bellows so that said packaging bag has only two sheet thickness superimposed with respect to each other within a mouth region of said bag;

complementary male/female closure strips provided with a control cursor upon said packaging bag sheet within the vicinity of said mouth region of said bag such that said closure strips extend transversely with respect to said longitudinal event of said packaging sheet; and

heat-sealed regions for closing and sealing said packaging bag,

each one of said cutout portions being defined by two rectilinear longitudinal edges which are respectively set back from the outer definition lines of said laterally spaced bellows, a rectilinear transverse edge extending transversely with respect to said longitudinal extent of said packaging bag sheet, and

a second transverse edge that is not rectilinear and is concave towards said mouth region of said bag.

33. A bag according to

claim 32, wherein:

said heat-sealed regions of said packaging bag comprises a line of heat-sealing defined between edge portions of said packaging bag sheet and edge portions of said cutout portions.

34. A packaging bag as set forth in

claim 32, wherein said packaging bag sheet comprises:

a planar main face;

first longitudinal flaps disposed upon and integrally connected to opposite sides of said planar main face;

second longitudinal flaps disposed upon and integrally connected to opposite sides of said first longitudinal flaps, and

auxiliary segments disposed upon and integrally connected to said second longitudinal flaps.

35. A packaging bag as set forth in

claim 32, wherein:

said second transverse edge comprises a dihedral made up of two rectilinear segments.