EP4337458A1

EP4337458A1 - Method and machine for manufacturing a flexible envelope-like bag, particularly with reinforcement

Info

Publication number: EP4337458A1
Application number: EP22728423.9A
Authority: EP
Inventors: Cédric Ritondo
Original assignee: Holweg Group SAS
Current assignee: Holweg Group SAS
Priority date: 2021-05-12
Filing date: 2022-05-09
Publication date: 2024-03-20
Also published as: FR3122847B1; FR3122848A1; WO2022238305A1; US20240239556A1; FR3122847A1

Abstract

According to a method for manufacturing flexible bags: - a first strip (la) of flexible material is unwound as a continuous sheet in a longitudinal direction (F); - a hem (15) is formed on each edge of the first strip (la) and the hems (15) are glued over at least one length of a first or a second flap (11, 12) on one stitching face (150), - a fold is formed in the first strip (la) along a transverse folding line (13) to fold down the first flap (11) over the second flap (12) against an internal face (14) of the first strip (la), the fold bringing, for each edge, hem (15) against hem (15) so as to obtain the bonding of the hems (15), - the strip (la) is cut along a transverse section (111) to form the bag (1) at the end of the operations. Machine implementing the method and bag thus obtained.

Description

Method and machine for manufacturing a flexible bag of the envelope type, in particular with reinforcement

The invention relates to the continuous manufacture of flexible bags of the envelope type from flexible sheet material, in particular paper. It relates in particular to the addition of reinforcing layers providing particularly mechanical and/or thermal characteristics.

Industrial processes for manufacturing bags made of flexible material such as paper or synthetic material have long been known. For example, document FR 1 270 400 describes a machine and a method in which a band is unwound and then formed into a casing. The casing is flattened so that it comprises a first and a second wall, then the casing is cut into sections so that at each end of the section there remains a tab which extends the first or the second wall. In a folding step, the tab is folded and glued by being folded over the wall other than that from which the tab originates. It is thus possible to manufacture bags at a high rate with a wide variety of materials and formats.

Document FR 786 579 shows several examples of this technique. It shows in particular in Figures 4 to 6 a manufacturing process in which the strip of paper is provided at regular intervals with lines of transverse perforations, with a line in the center and two lines, axially offset from the center line on each edge of the tape. The casing is formed by folding each edge over the central part and by gluing the two edges together along a central junction so that the perforations form two transverse lines offset respectively on one and the other of the faces of the casing. The casing thus formed passes between a pair of drive rollers which drive the casing at a constant speed. The front part of the casing is gripped by the folding device which comprises a drum and a counter-rotating folding roller. The drum and the folding roller rotate with a higher peripheral speed than the pair of drive rollers. The folding roller has a bar adapted to pinch the front of the casing against the drum, so that the front part of the casing is pulled and separated by tearing along the perforations to form a section. On separation, due to the shifts between the lines of perforation, a rear leg is thus formed on the section, as well as a front leg at the end of the casing. This front leg will end up on the next stretch. The front tab is folded by the folding device over a glued area to close the front part of the section. For this, the roller further comprises a folding blade, placed just behind the bar, which pushes the casing into a gripper carried by the drum so as to bend the casing.

In a variant, the casing is formed with bellows which connect the first and the second wall. Document WO 2016 097310 A1 shows an example of such bags. This document also shows a machine making it possible to form an envelope from the casing by using two stations each comprising a pair of counter-rotating cylinders and the work of which makes it possible to carry out the separation into sections and the tearing of a waste to reveal a leg at the front of the stretch on the same wall as the rear leg. Thus, after folding the tabs, they are applied to the same wall.

Such bags can be used as shipping envelopes. In this case, the rear tab is provided with an adhesive layer, for example protected by protective means such as a sheet of silicone paper. This sheet can be removed, revealing the adhesive layer. The back tab serves as a closing flap which can be folded back by bringing the adhesive layer against the wall opposite to that from which the back tab came, so that the adhesive layer sticks to the wall and seals the envelope. Thus, the wall from which the tabs come has a smooth face when the tabs are glued to the opposite face to close the envelope. When the envelope is received by its recipient, the latter tears off the end of the envelope, for example at the level of the flap, to access its content.

During the manufacture of the bags, the removal of the waste is a limitation: on the one hand, it is found that it is a limiting factor for the speed of manufacture of the bags, and on the other hand the large volume of waste is always a constraint to manage. In addition, the adjustment of such a machine requires high technicality. Changing the bag format takes a long time to adjust, especially when changing the width, because it is necessary to change the perforation means.

Document FR 1 270 400, already cited, also discloses a manufacturing process that can be used for envelopes. A continuous sheet of paper is unrolled and then cuts are made on the selvedges so as to release gluing seams symmetrical with respect to a longitudinal middle of the sheet and extending along a zone of the sheet which is names a first component. The seams are folded longitudinally on the sheet and coated with glue on the upper side, opposite the first flap. The sheet is cut into sections, for example by a straight cut and folded along a transverse fold to delimit a second flap which is folded over the first flap. The second flap is thus glued to the seams and the container is delimited between the first and the second flap. The cut is made in such a way that a tab remains as an extension of the first flap opposite the transverse fold.

The fact of making a clean cut instead of a tear gives a bag with a perceived better quality, the edge being sharper. However, this process also generates waste to make the side seams.

Document EP-3564146-A1 shows a bag manufacturing process quite similar to that of FR 1 270 400, but which differs in that no cut is made on the edge. The flaps folded over each other are glued together along the edges. The process thus has no waste generated, but the useful width of the bag is reduced by the width of the areas glued to each other. In addition, this type of bonding is more fragile, because the spacing constraints of one flap relative to the other are concentrated at the edge of the glued area.

Furthermore, there are needs for envelopes comprising reinforcements, either to give them a better hold and better protect the contents, or to insulate the contents against shocks or thermally.

The invention aims to provide a method and a machine for the high-speed manufacture of bags of the envelope type, with or without gussets, which does not generate waste, which makes it possible to reinforce the bag and which is easy to adjust. The invention also aims to provide a bag produced in this way.

With these objectives in view, the subject of the invention is a process for manufacturing flexible bags, according to which:
- Unrolling a first strip of flexible continuous sheet material in a longitudinal direction;
- forming a fold of the first strip along a transverse folding fold to fold a first flap over a second flap against an internal face of the first strip,
- we join the first and the second part along the edges,
- The strip is cut by a cross section to form a section before or after the folding of the flaps one over the other, the section forming the bag at the end of the operations;
characterized in that a hem is formed on each selvedge of the first strip before folding and the hems are glued over at least one length of the first or of the second flap on one side of the seam,
- the folding bringing for each selvage hem against the hem by the sewing face so as to obtain the gluing of the hems between them to join the first and the second flap along the selvedges.

This process makes it possible to produce bags of the envelope type without producing waste, therefore without limiting the rate due to the management of the evacuation of such waste. The process takes up the principle set out in document FR 1 270 400 but without requiring the edges to be cut. Indeed, the edges are folded over their entire length to form the hems and these are folded over one another after gluing to assemble the two folded flaps one over the other. The cut can be made by straight cutting means, that is to say by shearing, which gives a good perceived quality of the cut. The cut can also be made with a serrated knife cooperating with a groove to obtain separation without prior perforation lines. The cut could still be obtained by tearing, that is to say by pulling on a portion provided with perforations at the start of a cutting line. The cutting system is the same whatever the width of the bag to be produced. It is therefore easy to change the width, unlike the manufacture of pouch-type bags by tearing off waste, which requires the installation of specific tools and the production of perforations specific to the width. The flexible material is for example paper of varying weight, for example between 40 and 150 g/m², synthetic material, textile or a combination of these materials.

According to a refinement,
- at least one reinforcing layer is unrolled,
- the reinforcement layer is cut to obtain a system of at least one reinforcement panel,
- a first gluing is carried out on at least one of the elements from among the first strip and the system of at least one reinforcement panel,
- before folding, the first strip and the system of at least one reinforcement panel are brought together on the internal face of the first strip to glue them together thanks to the first gluing, so that the system of at least one panel is located between the first and the second pane.

We thus come to produce a bag whose internal wall is provided with one or more reinforcing panels. The visual aspect of the exterior of the bag remains substantially the same, the reinforcement panels being hidden inside the bag. Each reinforcement panel can be formed by superimposing multiple layers. The materials can be varied such as embossed paper to provide a layer of mechanical and thermal protection, a synthetic foam sheet or including bubbles, or a reflective sheet.

According to one embodiment, the length of the flaps in the longitudinal direction is unequal, such that the second flap has a tab not covered by the first flap after folding, the tab not being covered by the reinforcement panel. The method makes it possible to manufacture envelope bags with the tab which is used to close the bag by folding over the first flap. As desired for the envelopes, the second flap remains free.

According to an improvement, a second strip of flexible material is unrolled, a second gluing is carried out, and the second strip and first strip are brought together on the internal face of the first strip so that they stick together thanks to the second gluing. This additional band makes it possible to provide specific properties for the inside of the bag, for example by providing a smooth surface inside the bag when using embossed reinforcement or with a rough or adherent surface. Preferably, it extends over the same length as the first strip.

In particular, the system of at least one reinforcement panel is taken between the first and the second band. Thus, the second strip makes it possible to enclose the reinforcement panels.

According to one characteristic, the width of the first and the second band are different so that the hems come from only one of said bands. This makes it possible to have a strip serving as a mechanical reinforcement for the other strip, without however interfering with the folding of the hems during their formation.

According to an alternative characteristic, the width of the second band is identical to that of the first band. In this case, the hems are formed by two layers, which mechanically strengthens them.

According to one embodiment, a cheek is also formed at each selvage of the first band, the cheek being folded against the internal face and extending between the hem and a central part of the band, such that a stack is formed with the central part, the cheek and the hem in order, the cheeks forming a gusset connecting the first and the second flap after the bonding of the hems, the system of at least one reinforcement panel does not not extending over the cheeks when the bag has them. Considering the section of a selvage of a flap, the central part, the cheek and the hem form a kind of Z which is flattened during manufacture, but can be deployed during the use of the bag.

According to one embodiment, the system of at least one reinforcement panel comprises a single panel which extends over the first and the second flap. Reinforcement of the flaps is allowed, including at the level of the folding fold.

According to another embodiment, to form the system of at least one reinforcement panel, two reinforcement panels are cut and placed successively, one on the first flap and the other on the second flap, leaving an interval between them at the level of the transverse fold. Although this solution is more demanding, it allows the use of very rigid reinforcement panels, while allowing the folding fold to be easily made.

According to an improvement, a zone of closing glue and a protective strip are deposited on the zone of closing glue so that they are visible on the tab when the first flap is visible. This protective strip can be removed by the user before folding the tab over the first flap and thus sticking the tab to close the bag. This zone of glue and this protective strip can be deposited together or successively at different stages of the process. They can be deposited for example directly after the unwinding of the first strip on the internal face, directly after the unwinding of the second strip if necessary, after the cut or even after the formation of the folding fold.

According to an improvement, the hem is also glued on the face opposite the face of the seam along one of the elements only among the first and the second flap. Thus, considering one of the edges of the manufactured bag, the two hems are superimposed and glued together and, moreover, only one of them is glued on the cheek if necessary, or on the internal face of the flap . It can be seen that this arrangement makes it possible to stress the bonding essentially by sliding from one hem to the other, whereas without the bonding, the stress is concentrated at the edge of the bonding and tears the bonding more easily.

According to an improvement, separate reinforcement strips are deposited on the cheeks. This makes it possible to maintain the flexibility of the joint between the cheeks and the central part of the flaps while having a reinforcement of the cheeks. This also makes it possible to modulate the rigidity of the reinforcement panels between the central part and the cheeks.

The invention also relates to a bag made of flexible material comprising a first and a second flap from the same sheet folded along a transverse folding fold towards an internal face and joined together along edges of the flaps perpendicular to the fold. folding, characterized in that it comprises a hem formed on each selvedge, the hem of the first flap being glued to the hem of the second flap on the seam faces. The method as described above makes it possible to obtain such bags.

According to an improvement of the bag, the hem is connected to a central part of the flap by means of a cheek folded over the central part, so that a bellows is formed by two cheeks joined by the hems glued together .

According to an improvement, a system of at least one reinforcement panel extends against the internal face of the flaps.

According to an improvement, a second strip of flexible material is glued to the internal face of the first strip of flexible material and, in the case of a bag with a system of at least one reinforcement panel, the second strip of flexible material covers the system with at least one reinforcement panel. The second strip makes it possible to reinforce the bag, and to give it specific properties that the first strip or the reinforcement panels do not have, for example for sealing against liquids.

According to an improvement, the system of at least one panel comprises several superposed reinforcement panels, the reinforcement panels being of decreasing width, each panel being glued to one of the first and the second strip by the surface not covered by the adjacent panel. Thus, it is not necessary to provide for gluing the panels superimposed on each other. A connection of each panel is made with one of the strips, which ensures the positioning of the panels between the strips.

According to an improvement, the first flap is shorter than the second flap and leaves a tab on the second flap not covered by the first flap. There is thus a tab allowing in particular the closure of the bag by folding the tab over the first flap, leaving the second flap looking smooth.

The invention also relates to a machine for manufacturing flexible bags comprising:
- first unwinding means for unwinding a first strip of flexible continuous sheet material in a longitudinal direction;
- folding means to form a fold of the first strip along a transverse folding fold to fold a first flap over a second flap against an internal face of the first strip,
- assembly means for joining the first and the second section along the edges,
- First cutting means for cutting the strip by a cross section to form a section upstream or downstream of the assembly means, the section forming the bag at the end of the operations;
characterized in that it further comprises:
- a hemmer for each selvedge, to form a hem on each selvage of the first band upstream of the assembly means,
- application means for gluing the hems over at least one length of the first or the second flap on one side of the seam,
- the assembly means being the folding means configured to bring each selvage hem against the hem by the sewing face so as to obtain the gluing of the hems together to join the first and the second flap along the selvedges.

Upstream and downstream are defined in relation to the unwinding direction of the first strip. Such a machine is capable of producing bags as defined above continuously, at a high rate, for example at a few hundred bags per minute. The hemmer is for example a guide which causes the reversal of the selvage during the running of the band followed by a pair of rollers which encloses the selvage to mark the fold. The folding means are known for example from document FR 1 270 400.

According to an improvement, the machine further comprises:
- supply means for supplying at least one reinforcement layer,
- second cutting means for cutting the reinforcing layer and thus obtaining a system of at least one reinforcing panel,
- first gluing means for carrying out a first gluing at least on one of the elements among the first strip and the system of at least one reinforcement panel,
- call means, upstream of the folding means and downstream of the first gluing means and the feeding means, configured to bring together the first strip and the system of at least one reinforcement panel on the internal face of the first strip to stick them together by gluing, so that the system of at least one panel is located between the first and the second component.

The first strip and the reinforcing layer are unrolled in parallel and then brought together by the take-up means, formed for example by a pair of counter-rotating rollers. The reinforcement layer is cut beforehand. Gluing is carried out either on the inside face of the first strip, in the area which is intended to receive the reinforcement panel, or on the panel. If it is desired to use several layers of reinforcement, these are unrolled individually then assembled by other means of appeal before being presented to the second cutting means. For example, several layers of paper can be passed together in these call means also acting as an embosser, that is to say comprising two cylinders textured in a complementary manner, in order to produce hollows and bumps on the layers. The embosser is followed by a separator and to separate each of the reinforcement layers and stagger them between them so that the bumps are opposite the bumps. In this way, thickness is given to the stack of layers to perform a damping function.

According to an improvement, the machine comprises:
- second unwinding means for unwinding a second strip of flexible material,
- second gluing means for carrying out a second gluing, and
- Call means configured to further assemble the second strip and first strip on the inner face of the first strip so that they stick together thanks to the second sizing. This makes it possible to manufacture bags with a doubled wall, therefore reinforced mechanically or with properties other than the first band. The second sizing can be deposited on the second strip upstream of the take-off means, or on the first strip when no reinforcement panel is used. When reinforcement panels are used, the second strip is preferably wider than the panels in order to obtain a connection between the first and the second strip and thus enclose the panels.

According to an improvement, the machine further comprises a cheek forming station configured to further form a cheek at each selvedge of the first strip, the cheek being folded against the inner face and extending between the hem and a central part of the strip, so that a stack is formed with the central part, the cheek and the hem in order, the cheeks forming a bellows connecting the first and the second flap after the gluing of the hems, the system of at least one reinforcement panel not extending over the cheeks when provided. When a second strip is provided, it may be limited in width so as not to cover the cheeks, or on the contrary also double the cheeks and possibly the hem.

Brief description of figures

The invention will be better understood and other particularities and advantages will appear on reading the description which follows, the description referring to the appended drawings among which:

: the is a perspective view of a bag according to a first embodiment;

: the is a cross-sectional view of the sac of the ;

: the is a view similar to the of the closed bag;

: the is a perspective view of a bag blank from the during manufacture ;

: the is a view similar to the a bag according to a second embodiment;

: the is a cross-sectional view of a bag according to a third embodiment;

: the is a sectional view according to a mid-plane of the bag of the ;

: the is a top view of the bag from the ;

: the is a view similar to the a bag with gussets;

: the is a schematic view of a machine according to a first embodiment of the invention;

: the is a schematic view of a machine according to a second embodiment of the invention;

: the is a schematic view of the first tape in the machine from the for the lower part and in the machine of the for the upper part of the view;

: the is a schematic view of the assembly of strips before cutting into sections.

detailed description

A bag 1 envelope conforming to a first embodiment is shown in Figures 1 to 4. The bag 1 of flexible material comprises a first and a second flap 11, 12 from the same sheet folded along a fold of transverse folding 13 towards an internal face 14. The flaps 11, 12 are joined together along their edges which are perpendicular to the folding fold 13. A hem 15 is formed on each selvage and it is glued to the internal face 14 of the second flap 12. In addition, the hem 15 of the first flap 11 is glued to the hem 15 of the second flap 12 on seam faces 150. The first flap 11 is shorter than the second flap 12 so that a tab 16 remains by being the part of the second flap 12 not covered by the first flap 11. A layer of glue is deposited on part of the tab 16 and is completely covered by a protective strip 17 of silicone paper. After manual removal of the protective strip 17, the flap 16 can be folded over the first flap 11 in order to be glued and thus close the envelope, as shown in the . The represents the bag 1 in a manufacturing step before the folding of the first flap 11 on the second flap 12.

In a second embodiment, the bag 1' differs from that of the first embodiment in that the hem 15' is connected to a central part 110 of the flap 11', 12' via a cheek 181 folded over the central part 110, so that a bellows 18 is formed by two cheeks 181 joined by the hems 15' glued together.

In a third embodiment of the bag 1'', represented in FIGS. 6 to 8, the flaps 11'', 12'' are formed by the superposition of a first band 1a, a first reinforcement panel 19a, a second reinforcing panel 19b and a second strip 1b. The first reinforcement panel 19a is narrower than the first strip 1a and the second reinforcement panel 19b is narrower than the first reinforcement panel 19a. The second band 1b is narrower than the first band 1a but wider than the first reinforcing panel 19a. On the cross-sectional view of the we see that the first strip 1a has glue on the inner face 14 so that the first reinforcing panel 19a is glued there. Similarly, the second strip 1b includes glue on the inner face 14 so that it is glued to the second reinforcement panel 19b, to the first reinforcement panel 19a on the edges not covered by the second reinforcement panel 19b , and on the first band 1a between the hem 15 and the edge of the first reinforcing panel 19a. In the longitudinal section view, the reinforcing panels 19a, 19b are interrupted at the level of the folding fold 13''. In addition, the reinforcement panels 19a, 19b do not extend over the tab 16'' which is thus formed by the superposition of the two strips 1a, 1b only.

In a fourth embodiment, shown in the , the bag 1''' differs from that of the third embodiment in that the hem 15''' is connected to a central part 110 of the flap via a flange 181 folded over the central part 110 , so that a bellows 18 is formed by two cheeks 181 joined by the hems 15''' glued together.

A machine 2 according to a first embodiment of the invention allowing the manufacture of bags is represented schematically on the . Machine 2 includes:
- first unwinding means 201 for unwinding the first strip 1a of flexible continuous sheet material in a longitudinal direction;
- first gluing means 211 to carry out a first gluing at least on the first strip 1a,
- supply means 22 to supply the reinforcing layer,
- second cutting means 220 to cut the reinforcement layer and thus obtain a reinforcement panel 19a, 19b,
- second unwinding means 202 for unwinding a second strip 1b of flexible material,
- Deposition means 23 for depositing a layer of glue and a protective strip 17 on the layer of glue on the second strip 1b at regular intervals;
- second gluing means 212 to carry out a second gluing on the second strip 1b,
- call means 24 configured to further assemble the second strip 1b and first strip 1a with between them the reinforcing panels 19a, 19b on the inner face 14 of the first strip 1a;
- a hemmer 251 for each selvedge, to form a hem 15 on each selvage of the first strip upstream of the take-up means 24,
- transport means 26 to guide the assembly of strips downstream of the call means 24;
- application means 27 for gluing the hems 15 over at least one length of the first or second flap 12 on a seam face 150,
- First cutting means 28 for cutting the strip by a cross section to form a section forming the bag 1 at the end of the operations;
- assembly means, for joining the first and the second flap 11, 12 along the edges, made by folding means 29 to form a fold of the first strip 1a along a transverse folding fold 13, to fold the first flap 11 over the second flap 12 against an internal face 14 of the first band 1a, and to bring for each selvage hem 15 against the hem 15 by the sewing face 150 so as to obtain the gluing of the hems 15 together to join the first and the second part 11, 12 along the edges;
- stacking means, not shown, for stacking the bags downstream of the folding means 29.

The machine optionally includes another hemmer 252 to produce a hem on the edges of the second strip 1b in the case where the second strip is wider than the first strip and where the hems are carried only by the second strip 1b.

The first and second gluing means 211, 212 are for example flexography rollers making it possible to deposit glue according to a predetermined pattern. The glue is deposited on the internal face 14 of the strip, that is to say on the face facing the other strip after assembly.

The call means 24 are made by a pair of counter-rotating rollers 241 driven by a motor, not shown. They apply pressure to the strips 1a, 1b to obtain bonding between them and to the reinforcing panels 19a, 19b.

The supply means 22 also include call means 221 to join together two reinforcing strips, then the second cutting means 220 to cut the assembled strips into panels 19a, 19b, as detailed below.

The transport means 26 are preferably means operating by suction so as not to apply force through the thickness of the assembly.

The application means 27 are for example nozzles injecting glue intermittently.

The first cutting means 28 and the folding means 29 are conventional and are not detailed here. The various components are driven in rotation either by a single motor and synchronous mechanical transmissions, such as toothed belts or gears, or by several individual but electronically synchronized motors, or a combination of the two solutions.

A machine 2' conforming to a second embodiment, shown in the , is provided for making bags with gussets 18. It differs from that of the first embodiment in that there is also provided a cheek forming station 30 downstream of the call means 24 and configured to form furthermore a cheek 181 at each edge of the first band 1a or of the superposition of the bands 1a, 1b.

The represents the first strip 1a of flexible material seen from above, therefore showing its internal face 14, from its unwinding on the right towards the formation of the bag 1 on the left. The upper part beyond a middle axis A represents the version of a bag 1' according to the second embodiment, that is to say with gusset 18, while the lower part represents the version of the bag 1 according to the first embodiment, that is to say without bellows. For the first embodiment, the width of the strip is subdivided into a central part 110 and a hem zone 15. The hemmer 251 comprises application means, not shown, which deposit glue at intervals at the edge of the hem zone 15 over the length represented by the dashed line 152 corresponding to the first flap 11, then, in the hemmer 251, the hem zone 15 is turned against the central part 110 on the internal face 14. Thus, the hem is glued to the internal face at intervals, along the zone symbolized by the line 152. The means of application are for example

In the second embodiment, the width of the strip is subdivided into a central part 110, a flange 181 and a hem zone 15. By passing through the hemmer application means, not shown, of the glue is deposited at intervals at the edge of the hem zone 15 over the length represented by the dashed line 153 corresponding to the first flap 11, on the external face, opposite to the internal face 14. The hem 15 is formed during the passing through the hemmer 251 by a drawdown on the outer face and is glued on the length extending from the future cut 111 of the section to the future folding fold 13, along what will be the first flap 11. Downstream of the call means 24, the first band 1a passes through the cheek forming station 181 in which the cheeks 181 are folded against the internal face 14 of the first band 1a. The hem 15 becomes visible again from above the first strip 1a, looking at the internal face 14. After the flap 181 has been folded down against the internal face 14, the latter extends between the hem 15 and a central part 110 of the band, so that a stack is formed with in order the central part 110, the cheek 181 and the hem 15.

In both embodiments, the visible face of the hems 15, also called the seam face 150, is coated with glue over identical lengths on either side of the future folding fold 13, then the first strip 1a is cut by the first cutting means 28 into sections, at the level of the cutting line 111. The sections are transferred to the folding means 29 which form the folding fold 13 and fold the first flap 11 over the second flap 12. The hems 15 of the first flap 11 then stick to the hems 15 of the second flap 12 and the bag 1 is formed, as shown in the for bag 1 without gusset, or the for bag 1 with gussets 18.

The , built like the , details the assembly of the bands when the bags are made with reinforcement panels, here in two thicknesses. The call means 221 of the supply means 22 take two layers of reinforcement and superimpose them, the layer on the side of the first strip 1a being wider than the other. The second cutting means 220 sever a first part of the reinforcement panel 19a1, 19b1 which will extend over the first flap 11, then a second part of the reinforcement panel 19a2, 19b2 which will extend over the second flap 12. A small interval is created between the first and the second part of the reinforcement panel in order to allow the easy creation of the folding fold 13. The call means 221 of the supply means 22 slow down the supply of the reinforcement strips to allow the creation of an interval on the second flap 12 between the second part of the panel and the first part of the following section, interval which will be the space of the tab 16. The reinforcement panels extend only over the central part 110 of the first band 1a, and therefore not on the cheeks 181 in the case of a bag 1' with gusset 18, even if this is technically possible for flexible panels.

The invention is not limited to the embodiments which have been described by way of examples only. The protective strip 17 and the layer of glue that it protects is optional or could take various forms.

Claims

Process for manufacturing flexible bags, according to which:
- a first strip (1a) of flexible continuous sheet material is unrolled in a longitudinal direction (F);
- forming a fold of the first strip (1a) along a transverse folding fold (13) to fold a first flap (11) onto a second flap (12) against an internal face (14) of the first strip (1a),
- the first and the second part (11, 12) are joined together along the edges,
- the strip (1a) is cut by a cross section (111) to form a section before or after the folding of the flaps (11, 12) one on the other, the section forming the bag (1) at the end operations ;
characterized in that a hem (15) is formed on each selvedge of the first band (1a) before folding and the hems (15) are glued over at least one length of the first or of the second flap (11, 12) on a sewing face (150),
- the folding bringing for each hem selvage (15) against the hem (15) by the sewing face (150) so as to obtain the gluing of the hems (15) between them to join the first and the second flap (11, 12) along the edges.
A method according to claim 1, wherein:
- at least one reinforcing layer is unrolled,
- the reinforcement layer is cut to obtain a system of at least one reinforcement panel (19a, 19b),
- a first gluing is carried out at least on one of the elements among the first strip (1a) and the system of at least one reinforcement panel (19a, 19b),
- before folding, the first strip (1a) and the system of at least one reinforcement panel (19a, 19b) are brought together on the internal face (14) of the first strip (1a) to glue them together thanks to the first gluing, so that the system of at least one panel is located between the first and the second flap (12).
Method according to Claim 1 or 2, in which the length of the flaps (11, 12) in the longitudinal direction (F) is unequal, so that the second flap (12) has a tab (16) not covered by the first flap (11) after folding, the tab (16) not being covered by the system of at least one reinforcement panel (19a, 19b).
Method according to one of the preceding claims, according to which a second strip (1b) of flexible material is unrolled, a second gluing is carried out, and the second strip (1b) and first strip (1a) are joined together on the internal face (14 ) of the first band (1a) so that they stick together thanks to the second sizing.
Method according to claim 2 or 3 in combination with claim 4, wherein the system of at least one reinforcement panel is taken between the first and the second strip (1a, 1b).
Method according to Claim 4 or 5, in which the width of the first and of the second band (1a, 1b) are different so that the hems (15) come from only one of the said bands (1a, 1b) .
Method according to Claim 4 or 5, in which the width of the second strip (1b) is identical to that of the first strip (1a).
Method according to one of the preceding claims, according to which a flange (181) is also formed at each selvedge of the first strip (1a), the flange (181) being folded against the internal face (14) and extending between the hem (15) and a central part (110) of the band, such that a stack is formed with in order the central part (110), the cheek (181) and the hem (15) , the cheeks (181) forming a gusset (18) connecting the first and the second flap (11, 12) after the hems (15) have been glued, the reinforcement panel (19a, 19b) not extending over the cheeks (181) when the claim depends on claim 2.
Method according to claim 8, according to which separate reinforcing strips are deposited on the flanges (181).
Method according to one of Claims 2 to 9, according to which the system of at least one reinforcing panel comprises a single panel which extends over the first and the second flap (11, 12).
Method according to one of Claims 2 to 9, according to which, in order to form the system of at least one reinforcement panel (19), two reinforcement panels (19a, 19b) are cut out and placed successively, one on the first flap (11) and the other on the second flap (12) leaving a gap between them at the folding fold (13'').
Method according to one of the preceding claims in combination with claim 3, according to which a zone of closing glue and a protective strip (17) are deposited on the zone of closing glue so that they are visible on the tab ( 16) when the first flap (11) is visible.
Method according to one of the preceding claims, according to which the hem (15) is additionally glued on the face opposite the face of the seam (150) along one of the elements only among the first and the second flap ( 11, 12).
Bag of flexible material comprising a first and a second flap (11, 12) resulting from the same sheet folded along a folding fold (13) transverse towards an internal face (14) and joined together along edges of the flaps (11, 12) perpendicular to the folding fold (13),
characterized in that it comprises a hem (15) formed on each selvedge, the hem (15) of the first flap (11) being glued to the hem (15) of the second flap (12) on the seam faces ( 150).
Bag according to Claim 14, in which the hem (15) is connected to a central part (110) of the flap by means of a flange (181) folded over the central part (110), so that a bellows (18) is formed by two flanges (181) joined by the hems (15) glued together.
Bag according to Claim 14 or 15, in which the system of at least one reinforcement panel (19a, 19b) extends against the internal face (14) of the flaps (11, 12).
Bag according to one of Claims 14 to 16, in which a second strip (1b) of flexible material is glued to the internal face (14) of the first strip (1a) of flexible material and, when the claim depends on the claim 16, the second strip of flexible material covers the reinforcement panel (19a, 19b).
Bag according to claims 16 and 17 taken in combination, in which the system of at least one panel comprises several reinforcing panels are superimposed, the reinforcing panels (19a, 19b) being of decreasing width, each reinforcing panel (19a, 19b) being glued to one of the first and second strips (1a, 1b) by the surface not covered by the adjacent panel.
Bag according to one of claims 14 to 18, in which the first flap (11) is shorter than the second flap (12) and leaves a flap (16) on the second flap (12) not covered by the first flap (11).
Flexible bag making machine including:
- first unwinding means (201) for unwinding a first strip (1a) of continuous flexible sheet material in a longitudinal direction;
- folding means (29) to form a fold of the first strip (1a) along a transverse folding fold (13) to fold a first flap (11) over a second flap (12) against an internal face (14) of the first band (1a),
- assembly means (29) for joining the first and the second flap (11, 12) along the edges,
- first cutting means (28) for cutting the strip by a cross section to form a section upstream or downstream of the assembly means (29), the section forming the bag (1) at the end of the operations;
characterized in that it further comprises:
- a hemmer (251) for each selvage, to form a hem (15) on each selvage of the first band upstream of the assembly means (29),
- application means (27) for gluing the hems (15) over at least one length of the first or second flap (12) on a seam face (150),
- the assembly means being folding means (29) configured to bring for each hem selvage (15) against the hem (15) by the sewing face (150) so as to obtain the gluing of the hems (15) between them to join the first and the second flap (11, 12) along the edges.
Machine according to claim 20, characterized in that it further comprises:
- supply means (22) to provide at least one reinforcing layer,
- second cutting means (220) for cutting the reinforcing layer and thus obtaining a system of at least one reinforcing panel (19a, 19b),
- first gluing means (211) for carrying out a first gluing at least on one of the elements among the first strip (1a) and the system of at least one reinforcement panel (19a, 19b),
- call means (24), upstream of the folding means (29) and downstream of the first gluing means (211) and feed means (22), configured to collect the first strip (1a) and the system of at least one reinforcing panel (19a, 19b) on the inner face (14) of the first strip (1a) to bond them together by gluing, such that the system of at least one panel is located between the first and the second flap (12).
Machine according to Claim 20 or 21, characterized in that it comprises:
- second unwinding means (202) for unwinding a second strip (1b) of flexible material,
- second gluing means (212) for carrying out a second gluing, and
- call means (24) configured to further assemble the second strip (1b) and first strip (1a) on the internal face (14) of the first strip (1a) so that they stick together thanks to the second gluing.
Machine according to one of Claims 20 to 22, characterized in that it further comprises a cheek forming station (30) configured to further form a cheek (181) at each selvedge of the first strip (1a), the flange (181) being folded against the internal face (14) and extending between the hem (15) and a central part (110) of the strip, such that a stack is formed with in order the central part (110), the cheek and the hem (15), the cheeks (181) forming a bellows (18) connecting the first and the second flap (12) after the bonding of the hems (15), the system of at least one reinforcing panel (19a, 19b) not extending over the flanges (181) when the claim depends on claim 21.