Envelope, manufacturing process and machine

Abstract

The invention relates to an envelope formed from a sheet (M) of flexible material and comprising: • a lower section (12), • an upper section (11) superposed on the lower section (12), the sections (11, 12) being joined together by lateral edges (14), leaving an opening between the lateral edges (14), • a protective strip (17) on a layer of closing adhesive (170), the layer of closing adhesive (170) being intended to bring about the closure of the envelope (1) after the protective strip (17) has been removed, and at least one precut region (19) that is able to be detached from the envelope (1), the protective strip (17) and the layer of closure adhesive (170) extending at least partially over the precut region (19). Associated method and production machine

Description

Domaine technique

[0001] The invention relates to an envelope formed by at least one sheet of flexible material, a method of manufacturing an envelope and a machine for manufacturing flexible envelopes. Technique antérieure

[0002] Industrial processes for manufacturing bags from flexible materials such as paper or synthetic materials have long been known. For example, document FR 1 270 400 describes a machine and a process in which a strip is unrolled and then formed into a casing. The casing is flattened so that it has 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 that extends the first or second wall. In a folding step, the tab is folded and glued by being folded down onto the wall other than the one from which the tab originates. Bags can thus be manufactured at a high speed with a wide variety of materials and formats.

[0003] Document FR 786 579 shows several examples of this technique. It shows in particular on the figures 4 à 6 a manufacturing process in which the paper web is provided at regular intervals with transverse perforation lines, with one line in the center and two lines, offset axially with respect to the center line on each selvage of the web. The casing is formed by folding each edge over the central portion and gluing the two edges together along a central junction so that the perforations form two transverse lines offset respectively on each 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 counter-rotating drum and folding roller. The drum and folding roller rotate with a peripheral speed greater than that of the pair of drive rollers.The folding roller has a bar capable of pinching 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. Upon separation, due to the offsets between the perforation lines, a rear tab is thus formed on the section, as well as a front tab at the end of the casing. This front tab will be found on the next section. 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 also has a folding blade, placed just behind the bar, which pushes the casing into a clamp carried by the drum so as to fold the casing.

[0004] In one variant, the casing is formed with gussets that connect the first and second walls. WO 2016 097310 A1 shows an example of such bags. This document also shows a machine for forming an envelope from the casing using two stations, each comprising a pair of counter-rotating cylinders, the work of which allows the separation into sections and the tearing off of waste to reveal a tab at the front of the section on the same wall as the rear tab. Thus, after folding the tabs, they are applied to the same wall.

[0005] Such bags can be used as mailing envelopes. In this case, the rear flap 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 rear flap serves as a closing flap which can be folded by bringing the adhesive layer against the wall opposite to that from which the rear flap originates, so that the adhesive layer sticks to the wall and seals the envelope. Thus, the wall from which the flaps originate has a smooth face when the flaps are glued to the opposite face to close the envelope. When the envelope is received by its recipient, the latter tears the end of the envelope, for example at the flap, to access its contents.

[0006] When manufacturing bags, waste removal is a limitation: on the one hand, it is a limiting factor for the speed of bag manufacturing, and on the other hand, the large volume of waste is always a constraint to manage. Furthermore, the adjustment of such a machine requires high technical expertise. Changing the bag format takes a long time to adjust, especially when changing the width, because it is necessary to change the perforation means.

[0007] Document FR 1 270 400, already cited, also sets out a manufacturing process that can be used for envelopes. A continuous sheet of paper is unrolled and then cuts are made on the edges so as to release symmetrical glue seams with respect to a longitudinal middle of the sheet and extending along an area of ​​the sheet that is called an upper flap. The seams are folded longitudinally on the sheet and coated with glue on the upper face, opposite the upper flap. The sheet is cut into sections, for example by a clean cut and folded along a transverse fold to delimit a lower flap which is folded over the upper flap. The lower flap is thus glued to the seams and the container is delimited between the upper flap and the lower flap. The cut is made in such a way that a tab remains as an extension of the upper flap opposite the transverse fold.

[0008] Making a clean cut instead of a tear results in a bag with a perceived higher quality, with a cleaner edge. However, this process also generates waste for making the side seams.

[0009] It is possible to apply a layer of sealing adhesive protected by a protective strip to the flap of such envelopes. However, the layer of sealing adhesive cannot extend to the side edges of the flap. Therefore, once the envelope is closed, there is always a part of the flap that is not held on the envelope wall. In addition, it is not easy to grasp the protective strip, because it must first be separated from the wall where it is applied, for example by bending this wall.

[0010] Document EP-3564146-A1 shows a bag manufacturing process quite similar to that of FR 1 270 400, but which differs in that no cutting is done at the selvedge. The flaps folded over each other are glued together along the selvedge. The process therefore does not generate any waste, but the useful width of the bag is reduced by the width of the areas glued to each other. In addition, this type of gluing is more fragile, because the stresses of spacing one flap from the other are concentrated at the edge of the glued area.

[0011] In the prior art, US 5,002,220 A discloses an envelope and a method of making an envelope. Exposé de l'invention

[0012] The invention aims to provide an envelope whose closure is of good quality and easy to produce. It also aims to provide a method and a machine for high-speed manufacturing of such envelopes, with or without gussets, which does not generate waste and is easy to adjust.

[0013] With these objectives in view, the invention provides an envelope according to claim 1.

[0014] Such an envelope is used by first detaching the pre-cut area and pulling the protective strip with it to release the closing adhesive layer. The adhesive layer remaining on the envelope extends to the edge of the remaining part, which, in the case of a closing flap, allows the latter to be glued entirely and prevents a part of the flap from being held on the wall of the envelope. In addition, the removal of the protective strip is made easier. It is sufficient to grasp the pre-cut area along its thickness, then pull on the assembly to remove the protective strip by detaching the pre-cut area. A pre-cut area can be provided at each end of the protective strip. The flexible material is, for example, paper of varying weights, for example between 40 and 150 g / m 2 < , synthetic material, textile or a combination of these materials.The protective strip is, for example, made of paper with, on one side, a silicone layer which comes into contact with the sealing glue, which allows the protective strip to be detached without tearing it and leaving the sealing glue on the envelope.

[0015] According to an improvement, the pre-cut area has a reinforced adhesive layer covered by the protective strip, the protective strip adhering more strongly to the reinforced adhesive layer than to the closing adhesive layer. The removal of the protective strip is further facilitated, since pulling on the pre-cut area is sufficient, even without pinching the protective strip with the pre-cut area. The protective strip remains firmly adhered to the pre-cut area, due to the reinforced adhesive layer.

[0016] According to an alternative improvement, the pre-cut area is folded over a back of the protective strip, the closing adhesive layer on the pre-cut area being glued to said back of the protective strip, the back of the protective strip adhering more strongly to the adhesive layer than the face opposite the back adheres to the closing adhesive layer. The same adhesive is used to obtain a different bonding, using a different quality of adhesion depending on whether the face used is coated or not. The protective strip has a coated face having a non-stick property and an opposite untreated face, on which the adhesion of the adhesive is stronger. The pre-cut area is part, for example, of a hem or a gusset cheek as defined below.

[0017] In one embodiment, the flaps are connected along the side edges by bellows, each bellows having two cheeks.

[0018] According to one provision, in the case of bellows, the pre-cut area extends over at least the entire width of the bellows. Thus, the part of the bellows along the protective strip will be removed entirely with the protective strip.

[0019] According to an improvement, the envelope comprises at least two protective strips in parallel in a transverse direction, and at least one pre-cut area for each protective strip. Thus, the envelope is reusable by being closed first after the removal of a first of the protective strips and the pre-cut areas attached thereto, then a second time after the removal of the second protective strip and the pre-cut areas attached thereto. A weakening line can be provided between the two strips to more reliably open the envelope without tearing the part where the second strip is located.

[0020] According to one feature, the edges of the upper flap and the lower flap at the opening are offset from each other to leave a tab area extending over the lower flap between said edges, the protective strip extending over the tab area. A tab is thus formed which allows the envelope to be closed by folding the tab and gluing it to the upper flap.

[0021] According to one embodiment, the closure adhesive layer is subdivided into a first, a second and a third transversely extending portion, the lower flap having a first and a second line of weakness between the first and second portion, respectively the second and third portion, the protective strip having a third line of weakness aligned with the first line of weakness and a fourth line of weakness aligned with the second line of weakness, the lines of weakness extending through the pre-cut area.Such an envelope is reusable in that the envelope can be closed a first time by detaching the protective strip to release the first part of the closing adhesive layer and sticking it on the upper flap, then the envelope can be opened by tearing off the strip of material delimited between the first and second weakening lines and the part of the protective strip located between the third and fourth lines. Finally, the envelope can be closed a second time by releasing the third part of the closing adhesive layer by removing the rest of the protective strip to stick it on the upper flap.

[0022] According to one embodiment, the protective strip and the closing adhesive layer are at least partially covered by the upper flap. Thus, when the protective strip is removed, the upper and lower flaps can stick together from the inside. This allows for a particularly tight closure.

[0023] According to an improvement of this embodiment, the protective strip and the closing adhesive layer extend over the entire periphery of the opening. Thus, after removal of the protective strip, the closure of the envelope is particularly tight, leaving no passage open at the opening.

[0024] According to one embodiment, the upper flap and the lower flap are made from the same sheet formed into a casing and glued edge to edge. Such an envelope is for example obtained according to a manufacturing method of document WO 2016 097310 A1.

[0025] According to an improvement of this embodiment, the edges of the flaps along the opening are aligned. The protective strip is then located inside the bag, which allows the flaps to be stuck together without folding.

[0026] According to a further improvement, the edge of the upper flap along the opening extends beyond the lower flap, the pre-cut area extending over the entire width of the upper flap set back from the edge of the lower flap. The waste portion that is usually detached in the manufacturing process remains in place in this version. The closing adhesive layer and the protective strip extend over this waste portion, which will be removed by the user of the envelope, by removing the protective strip and the waste portion together.

[0027] According to another embodiment, the upper flap and the lower flap are made from the same sheet of material folded along a transverse folding fold, perpendicular to the lateral edges of the flaps, towards an internal face, the envelope comprising a hem formed on each lateral edge, the hem of the upper flap being glued to the hem of the lower flap on sewing faces. This corresponds for example to the manufacturing method of document FR 1 270 400 at figures 3 And 4 , but with the difference that the selvedges are not cut but hemmed continuously.

[0028] According to one embodiment, the hem is connected to a central part of the flap by means of a cheek folded over the central part, so that a gusset is formed by two cheeks joined by the hems glued together. The same technique as previously explained also applies to obtain envelopes with gussets. The gussets are made by assembling two cheeks, glued in the middle of the gusset. The cheeks are obtained by longitudinally folding the edges of the sheet of flexible material.

[0029] According to an improvement, the hem is glued on the face opposite the sewing face along only one of the elements among the upper flap and the lower flap. Thus, considering one of the selvedges of the manufactured envelope, the two hems are superimposed and glued together and, in addition, only one of them is glued on the cheek if necessary, or on the internal face of the flap. It is noted that this arrangement makes it possible to stress the gluing essentially by sliding from one hem on the other, whereas without the gluing, the stress is concentrated at the edge of the gluing and tears the gluing more easily.

[0030] The invention also relates to a method of manufacturing an envelope, according to claim 17.

[0031] The sealing adhesive layer, the protective strip and the pre-cut lines are produced flat and by operations during the continuous unwinding of the sheet, which lends itself to a high production rate. The envelope formation is then carried out by folding and separating the sheet into sections.

[0032] According to a manufacturing method: a hem is formed with a hemmer on each selvedge of the sheet before folding and the hems are glued over at least one length of an upper flap or a lower flap on a sewing face, a folding of the sheet is formed with folding means along a transverse folding fold to fold the upper flap onto the lower flap against an internal face of the sheet, the folding means bringing back for each selvedge hem against hem by the sewing face so as to obtain the gluing of the hems together to join the upper flap and the lower flap along the selvedge, the sheet is cut by a transverse cut made by cutting means to form a section before or after folding the flaps on top of each other, the section forming the envelope at the end of the operations.

[0033] This process makes it possible to produce envelope-type bags without producing waste, and therefore without any limitation in throughput due to the management of the disposal of such waste. The process uses the principle set out in document FR 1 270 400 but without requiring the selvedges to be cut. In fact, the selvedges are folded along their entire length to form the hems and these are folded over each other after gluing to assemble the two flaps folded over each other. The cut can be made by straight cutting means, i.e. by shearing, which gives a good perceived quality of the cut. The cut could also be obtained by tearing, i.e. by pulling on a portion provided with perforations at the start of a cutting line. The cutting system is the same regardless of 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 use of specific tools to produce perforations specific to the width.

[0034] According to one embodiment, the cross-section extends over the protective strip to separate the protective strip into a first part on the upper flap and a second part on the lower flap, the first part and the second part being superimposed after folding at least partially. This produces a two-part protective strip which makes it possible to obtain a layer of closing glue on the inner face of the two flaps, so as to join them together by this gluing after removal of the protective strip.

[0035] According to one embodiment, the first and third weakening lines, and the second and fourth weakening lines respectively, are marked together after the protective strip has been placed on the sheet.

[0036] According to one embodiment, for the manufacture of a casing formed from a casing, transverse perforation lines are made on the strip delimiting a rear end of a first casing and a front tab of a second casing following the first between a central line in the transverse direction and a bottom line from which the front tab protrudes forward, the bottom line further delimiting the pre-cut area, the sheet is formed into a casing, then the first and second casings are separated by axial traction on the casing by tightening the first casing on the pre-cut areas so that the separation is made along the central line and the bottom line.

[0037] The invention also relates to a machine for manufacturing flexible envelopes according to claim 22. Brève description des figures

[0038] The invention will be better understood and other features and advantages will appear on reading the description which follows, the description making reference to the appended drawings among which: [ Fig.1 ] : there [ Fig.1 ] is a perspective view of an envelope according to a first embodiment; [ Fig.2 ] : there [ Fig.2 ] is a view similar to the [ Fig.1 ] of a part of the envelope of the [ Fig.1 ] after removal of a protective strip; [ Fig.3 ] : there [ Fig.3 ] is a view similar to the [ Fig.1 ] of a part of the envelope of the [ Fig.1 ] after closing; [ Fig.4 ] : there [ Fig.4 ] is a perspective view of an envelope according to a second embodiment; [ Fig.5 ] : there [ Fig.5 ] is a view similar to the [ Fig.4 ] of a part of the envelope of the [ Fig.4 ] after removal of a protective strip; [ Fig.6 ] : there [ Fig.6 ] is a perspective view of an envelope according to a third embodiment; [ Fig.7 ] : there [ Fig.7 ] is a view similar to the [ Fig.6 ] of a part of the envelope of the [ Fig.6 ] after removal of a first protective strip; [ Fig.8 ] : there [ Fig.8 ] is a view similar to the [ Fig.6 ] of a part of the envelope of the [ Fig.6 ] after closing the envelope; [ Fig.9 ] : there [ Fig.9 ] is a top view of a portion of an envelope according to a fourth embodiment; [ Fig.10 ] : there [ Fig.10 ] is a perspective view of a portion of an envelope according to a fifth embodiment; [ Fig.11 ] : there [ Fig.11 ] is a sectional view along plane XI of the [ Fig.10 ] ; [ Fig.12 ] : there [ Fig.12 ] is a perspective view of an envelope according to a sixth embodiment; [ Fig.13 ] : there [ Fig.13 ] is a view similar to the [ Fig.12 ] of a part of the envelope after removal of a protective strip; [ Fig.14 ] : there [ Fig.14 ] is a perspective view of an envelope according to a seventh embodiment; [ Fig.15 ] : there [ Fig.15 ] is a schematic view of a machine according to a first embodiment; [ Fig.16 ] : there [ Fig.16 ] is a schematic view of a machine according to a second embodiment; [ Fig.17 ] : there [ Fig.17 ] is a top view of a sheet during its transformation for the manufacture of an envelope according to the first and second embodiments; [ Fig.18 ] : there [ Fig.18 ] is a top view of a sheet during its transformation for the manufacture of an envelope according to the third embodiment; [ Fig.19 ] : there [ Fig.19 ] is a top view of a sheet during its transformation for manufacturing an envelope according to the fourth embodiment; [ Fig.20 ] : there [ Fig.20 ] is a top view of a sheet during its transformation for manufacturing an envelope according to the fifth embodiment; [ Fig.21 ] : there [ Fig.21 ] is a top view of a sheet during its transformation for manufacturing an envelope according to the sixth embodiment; [ Fig.22 ] : there [ Fig.22 ] is a top view of a sheet during its transformation for manufacturing an envelope according to the seventh embodiment. Description détaillée

[0039] An envelope 1 according to a first embodiment of the invention is shown in the figures 1 à 3 . Such an envelope 1 is made from a layer of flexible material such as paper and comprises a lower flap 12, an upper flap 11 superimposed on the lower flap 12, the flaps 11, 12 being made from the same sheet (M) of material folded along a transverse folding fold 13 perpendicular to lateral edges 14 of the flaps, towards an internal face 120. The envelope 1 comprises a hem 15 formed on each lateral edge 14, the flaps 11, 12 being connected to each other by lateral edges 14 by the fact that the hem 15 of the upper flap 11 is glued to the hem 15 of the lower flap 12 on sewing faces 150. An opening between the lateral edges 14 remains to allow the filling of the envelope 1. The upper 111 and lower 121 edges of the upper flap 11 and of the lower flap 12 at the opening are offset from each other to leave a tab area 16 extending over the lower flap 12 between said edges.

[0040] The envelope 1 further comprises a protective strip 17 extending over the tab area 16 on a layer of closing glue 170. The layer of closing glue 170 is intended to close the envelope 1 after removal of the protective strip 17 and folding of the tab area 16 onto the upper flap 11.

[0041] The envelope 1 further comprises, along the opening, two pre-cut areas 19 capable of being detached from the envelope 1. The protective strip 17 and the closing adhesive layer 170 further extend over the pre-cut area 19. The pre-cut area 19 comprises a reinforced adhesive layer 171 covered by the protective strip 17 so that the protective strip 17 adheres more strongly to the reinforced adhesive layer 171 than to the closing adhesive layer 170.

[0042] When the user of the envelope 1 wishes to use it, after having filled it, he successively grasps the pre-cut areas 19 by pinching the protective strip 17 and pulls to detach the pre-cut areas 19 from the envelope 1, then completely removes the protective strip 17. The layer of closing glue 170 on the tab area 16 then remains exposed, as shown in [ Fig.2 ]. The user can then fold the tab area 16 by folding it over the upper flap 11 to close the envelope 1, as shown in [ Fig.3 ].

[0043] In a second embodiment, shown in the figures 4 And 5, the envelope 1a differs from that of the first embodiment in that the flaps 11a, 12a are connected to each other along the lateral edges 14a by two bellows 18, each bellows 18 comprising two cheeks 181. Considering the section of a selvedge of a flap, the central part, the cheek and the hem 15 form a sort of Z which is flattened during manufacture, but can be deployed when using the envelope 1. The cheeks 181 are connected to each other in the middle of the bellows 18 by gluing the hems on their sewing face 150. One of the hems is further glued to the cheek from which it originates, on the face opposite the sewing face 150. The pre-cut area 19 extends over the entire width of the cheek of the lower flap 12.

[0044] According to a third embodiment, the envelope 1b differs from that of the first embodiment in that it comprises at least two protective strips 17', 17" in parallel in a transverse direction, and at least one pre-cut zone 19', 19" for each protective strip 17', 17", as shown in figures 6 à 8 . The leg area 16b is provided with a transverse weakening line 160. In use, the user removes the outermost protective strip 17', as shown in the [ Fig.7 ], and fold the tab area 16b over the upper flap 11b as shown in [ Fig.8 ]. The closing glue layer 170' released by said protective strip 17' serves to glue the tab 16b. This envelope 1b can be opened by tearing the glued part along the weakening line 160, then closing the envelope 1b again by removing the second protective strip 17", to obtain a closure as in the [ Fig.3 ].

[0045] In a fourth embodiment, the envelope 1c shown in the [ Fig.9 ] differs from that of the first embodiment in that the closing glue layer 170c is subdivided into a first, a second and a third part 1701, 1702, 1703 extending transversely. The lower flap 12c comprises in the tab area 16c a first and a second weakening line 161, 162, between the first and second part 1701, 1702, respectively the second and third part 1702, 1703. The protective strip 17 comprises a third weakening line 173 aligned with the first weakening line and a fourth weakening line 174 aligned with the second weakening line 162. The weakening lines 161, 162, 173, 174 extend through the pre-cut area 19c.

[0046] When using such an envelope 1, a user inserts a content, not shown, into the envelope 1c through the opening, then detaches the third part of the protective strip 1703, including the pre-cut areas 19, by tearing it along the fourth weakening line 174, leaving the first and second parts 1701, 1702 of the protective strip 17. He folds the tab 16c and presses the third part of the closing adhesive layer 1703 onto the upper flap 11 so as to obtain the bonding. The envelope 1 is then closed and can be sent.

[0047] When receiving the envelope 1c, the recipient pulls on the assembly formed by the second strip portion located between the weakening lines 161, 162 and the corresponding tab area 16 connected by the second glue portion 1702. The portion which detaches forms a strap which separates the tab 16c into two parts, one of which remains stuck to the upper flap 11, and another which opens and releases the opening.

[0048] Envelope 1c can be reused by the recipient. To do this, he removes the first part of the protective strip to release the remaining layer of closing glue 1701, he folds back the tab 16c as before to stick it on the upper flap 11.

[0049] In a fifth embodiment, the envelope 1d differs from that of the first embodiment in that the protective strip 17d and the closing adhesive layer 170d are covered at least in part by the upper flap 11, in this case they extend over the entire periphery of the opening, as shown in figures 10 And 11The protective strip 17d is made of two parts 175, 176 glued together by a glue stronger than that of the closing glue layer 170 in a joining zone 177. This joining zone 177 is located on sections 1750, 1760 of the protective strip 17 which extend beyond the hems 15d and in an area where the flaps 11d, 12d overlap. When in use, the user grasps the corner of the tab area 16 to detach the pre-cut areas 19d by first driving the portion of the protective strip 175 onto the lower flap 12 and then the portion 176 onto the upper flap 11. He can then squeeze the flaps 11d, 12d together to stick them together at the opening and further fold the tab area 16d onto the upper flap 11 to stick it.

[0050] In a sixth embodiment of the envelope 1, shown in the figures 12 And 13, the upper flap 11 and the lower flap 12 are made from the same sheet (M) formed into a casing and glued edge to edge and flattened. The envelope 1e is closed by a tab 127 coming from the lower flap folded down and glued onto the upper flap 11e, in a manner known per se. In addition, the upper edge 111e of the upper flap 11e along the opening extends beyond the lower flap 12e, the pre-cut area 19e extending over the entire width of the upper flap 11e set back from the lower edge 121e of the lower flap 12e< up to a pre-cut line 191e. The pre-cut line 191e extends across the entire width of the upper flap 11e set back from the lower edge, as well as across the lower flap 12e joining the lower edge 121e by a slanted line 192e along each side edge 14e.The protective strip 17e extends over the lower flap 12e between the lower edge 121e and the portion of the pre-cut line 191e on the upper flap 11, also covering the bias lines 192e. When using this envelope 1e, the user pulls on the corner of the opening to detach the pre-cut area 19e, i.e. the portion of the upper flap 11e between the upper edge 111e and the pre-cut line 191e, so as to remove the protective strip 17 and release a new tab 16e comprising the closing adhesive layer 170e, as shown in [. Fig.13 ]. The user then simply has to fold down this tab 16e to stick it on the upper flap 11e and thus close the envelope 1e.

[0051] According to a seventh embodiment, shown in the [ Fig.14 ], the envelope 1f differs from that of the sixth embodiment in that the lower and upper edges 111f, 121f are superimposed. The bottom is formed by known means, not detailed here, making it possible to produce a welded flat bottom, a square bottom or a hexagonal bottom etc. A ninth pre-cut segment 199 extends transversely on the upper flap 11f and two eighth segments extend from the ends of the ninth segment towards the edge 121f of the lower flap 12f. When using this envelope 1f, the user pulls on the pre-cut area 19f to detach it, that is to say on the part of the upper flap 11f between the upper edge 111f and the pre-cut line 199, so as to remove the protective strip 17f and release a new tab comprising the closing adhesive layer. An envelope similar to that of the [ Fig.13 ].

[0052] There [ Fig.15 ] schematically shows a machine for producing envelopes according to the first embodiment up to the fifth. Machine 2 comprises: first unwinding means 201 for unwinding the continuous sheet M of flexible material in a longitudinal direction F; marking means 202 for marking on the sheet M pre-cut lines delimiting pre-cut areas 19; depositing means 23 for depositing a layer of closing glue 170 and a protective strip 17 on the layer of closing glue on the sheet M at regular intervals; take-up means 24 configured to exert traction on the sheet M of continuous material; a hemmer 251 for each selvedge M1, M2, to form a hem 15 on each selvedge of the sheet M upstream of the take-up means 24; transport means 26 for guiding the sheet downstream of the take-up means 24;application means 27 for gluing the hems 15 over at least one length of the lower flap 12 or the upper flap 11 on a sewing face 150, first cutting means 28 acting as separation means for cutting the sheet M by a transverse cut to separate a section forming the envelope 1 at the end of the operations; assembly means, for joining the upper flap 11 and the lower flap 12 along the selvedges, produced by folding means 29 to form a fold of the sheet M along a transverse folding fold 13, to fold the upper flap 11 onto the lower flap 12 against an internal face 120 of the sheet M, and to bring back for each selvedge hem 15 against hem 15 by the sewing face 150 so as to obtain the bonding of the hems 15 together to join the upper flap 11 and the lower flap 12 along the selvedges M1, M2;stacking means 290, for stacking the envelopes downstream of the folding means 29.;

[0053] The depositing means 23 comprise second unwinding means 230 for unwinding a sheet of protective material having a face coated with a non-stick coating, a cutting station 231 for forming the protective strips 17 from the sheet of protective material and a depositing roller 232 for bringing the protective strip onto the sheet M with the non-stick face on the glue zones. The depositing means 23 further comprise gluing means 233 for depositing the glue zones 170, 171 upstream of the depositing roller 232.

[0054] The call means 24 are produced by a pair of counter-rotating rollers 241 driven by a motor, not shown.

[0055] The application means 27 are, for example, nozzles injecting glue intermittently.

[0056] The first cutting means 28, the folding means 29 and the stacking means 290 are conventional and are not detailed here. The various members are driven in rotation either by the same 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.

[0057] A machine 2' according to a second embodiment, shown in the [ Fig.16 ], is provided for producing envelopes with gussets 18. It differs from that of the first embodiment in that a cheek forming station 30 is also provided downstream of the call means 24 and configured to further form a cheek 181 at each edge M1, M2 of the sheet M.

[0058] Machine 2 implements the following steps of the method of manufacturing an envelope 1 according to the first embodiment: unwinding the sheet M of flexible material in a longitudinal direction F by the unwinding means 201, marking the pre-cut lines delimiting pre-cut areas 19 on the sheet M by the marking means 202, depositing the closing glue 170 which extends on either side of the pre-cut lines and the reinforced glue 171 on the pre-cut areas 19 and depositing a protective strip 17 over the closing glue 170 and the reinforced glue 171 by the depositing means 23, forming a hem 15 with the hemmer 251 on each selvedge M1, M2 of the sheet M, gluing the hems 15 on a sewing face 150, over twice the length of the upper flap 11 by the gluing means 27, separating the sheet M into sections T by the cutting means 28 by a transverse cut, with folding means 29,folding the sheet M along the transverse folding fold 13 to fold the upper flap 11 onto the lower flap 12 against an internal face 120 of the sheet M, the folding means bringing back for each selvedge hem 15 against hem 15 by the sewing face 150 so as to obtain the gluing of the hems together to join the upper flap 11 and the lower flap 12 along the selvedge M1, M2 so as to form the envelope 1 with the section T.,

[0059] There [ Fig.17 ] schematically shows the sheet M of flexible material when it is in the machine, being unwound from the right of the figure towards the cutting means to the left. The lower part of the figure, below a center line M3, represents one half of the sheet M during the formation of an envelope 1 without gussets according to the first embodiment, the other half being symmetrical with respect to the center line M3. The upper part represents half of the sheet M during the formation of an envelope 1 with gussets 18, according to the second embodiment of the envelope 1, the other half being symmetrical with respect to the center line M3. On the right part of the figure, the sheet M of material is shown flat. A longitudinal line in dashes and double dots represents the future hem fold 151 or also, for the upper part of the figure, the future cheek fold 182.A dotted transverse line 113 represents the position of the first edge 111 when the first flap 11 will be folded. A dashed and double-dotted transverse line 123 represents the future transverse section separating a section of the sheet M.

[0060] Concerning the first embodiment, the pre-cut lines comprise a first segment 191 extending transversely at the future first edge 113 from the edge of the sheet M to the future fold of the hem 151 and a second segment 192 connected to the first segment 191 and extending obliquely to the future transverse cut 123. As already indicated previously, the segments are made symmetrically with respect to the center line M3. Closure glue 170 is deposited by creating a layer of closure glue 170 partially covering the second segments 192 between the future hem folds 151 and reinforced glue 171 is deposited as an extension of the closure glue 170 on the future hem 15. The protective strip 17 is deposited by extending transversely and completely covering the glue zones 170, 171.

[0061] Further to the left, the formation of the hem 15 is shown by folding the edge M1 of the sheet M along the longitudinal hem fold 151. The end of the protective strip 17 is thus also folded back at the same time as the hem 15. The hem is previously coated with glue at intervals by application means of the hemmer. The coating is carried out over a length corresponding to that of the upper flap. After the hem has been formed, it is glued to the upper flap. At the left end, a three-dash, two-dot line represents the folding fold 13 between the upper flap 11, not shown, and the lower flap 12 onto which the upper flap 11 will be folded by bringing the upper edge into alignment with the dotted line 113. The hem 15 has a sewing face 150 which is glued, such that after folding, the hem 15 along the upper flap 11 is glued to the hem 15 along the lower flap 12.The sheet M is cut, generally before folding, to detach a section T which will form the envelope 1 according to the first embodiment after folding and gluing the hems 15.

[0062] In a variant of the first embodiment, not shown, the strip of material for manufacturing the protective strips has one side coated with a release layer over a width corresponding to that of the closing adhesive layer, the edges of the strip of material remaining raw. The areas of reinforced adhesive receive the same adhesive as the closing adhesive areas and the parts of the protective strip which do not have a release layer. The bond thus obtained in the areas of reinforced adhesive is stronger than on the areas of closing adhesive, which is the desired objective.

[0063] In a variant of the first embodiment, not shown, the protective strip extends only between the future hem folds 151, leaving exposed the layer of glue 171 which extends over the pre-cut areas 19. When the cheek or hem is folded over the back of the protective strip 17, they stick strongly together. When the pre-cut areas are detached, they will pull the protective strip to expose the closing layer of glue 170.

[0064] Concerning the second embodiment, the pre-cut lines comprise a third segment 193 extending transversely at the future first edge from the edge of the sheet M to the future fold of the cheek 182 and a fourth segment 194 connected to the first segment 191 and extending obliquely to the future cutting line. Closure glue is deposited by creating a layer of closure glue 170 partially covering the fourth segments 194 between the future cheek folds 182 and reinforced glue 171 is deposited as an extension of the closure glue 170 on the future cheek 181. The protective strip 17a is deposited by extending transversely and completely covering the glue areas. Further to the left, the formation of the cheek 181 and the hem 15a is shown by longitudinal folding of the edge of the sheet M2 according to a Z profile along the cheek fold 182 and the hem fold 151.The end of the protective strip 17a is thus also folded back at the same time as the cheek 181. At the left end, a line of three dashes and two dots represents the folding fold 13 between the upper flap 11a, not shown, and the lower flap 12a onto which the upper flap 11a will be folded back by bringing the upper edge into alignment with the dotted line. The hem 15a has a sewing face 150 which is glued, so that after folding, the hem 15a along the upper flap 11a is glued to the hem 15a along the lower flap 12a. The sheet M is cut, generally before folding, to detach a section which will form the envelope 1 according to the second embodiment after folding and gluing the hems 15a.

[0065] With reference to the [ Fig.18 ], similar to the [ Fig.17 ], the manufacture of an envelope 1b according to the third embodiment has been shown, in the lower part, and a variant with gussets 18 in the upper part, not previously described. The pre-cut lines are similar to those of the [ Fig.17 ], but completed by a fifth segment 195 extending transversely from the edge to the second segment 192 between the future first edge 113 and the future cutting line 123. In addition to the previous glue zones 170b, 171b and the protective strip 17b extending in the pre-cut zones 19b, closing glue 170b' and reinforced glue 171b' are deposited on the tab 16b extending over the pre-cut zone 19b' delimited between the first and fifth segments 191, 195, as well as the second protective strip 17b' parallel to the first protective strip 17b. A weakening line 160 is made at the same time as the pre-cut lines and extends between the fifth segments 195. The remainder of the formation of the envelope 1 is similar to the example described in relation to the [ Fig.17 ].

[0066] In a variant not shown, the protective strip 17b is in one piece and covers the two glue zones 170b, 170b'. The weakening line 160 and the fifth segments are produced together at the same time as a weakening line of the protective strip 17b superimposed on the weakening line 160, after the protective strip 17b has been deposited on the sheet M.

[0067] With reference to the [ Fig.19 ], for the manufacture of an envelope 1c according to the fourth embodiment, or of a variant of the fourth embodiment with gussets 18, the pre-cut zones 19c are identical to those of the [ Fig.17 ]. On the other hand, the closing adhesive layer 170 is subdivided into a first, a second and a third part 1701, 1702, 1703 extending transversely and parallel to each other. The protective strip 17 is deposited on the tab 16c on all the parts of the adhesive layer 1701, 1702, 1703. Then, weakening lines are produced, for example by in-line perforations. Thus, on the lower flap 12, the first and second weakening lines 161, 162 are produced together between the first and second parts 1701, 1702, and respectively the second and third parts 1702, 1703. Similarly, the third weakening line 173 aligned with the first weakening line 161 and the fourth weakening line 174 aligned with the second weakening line 162 are produced together. As a result, the weakening lines extend through the pre-cut area 19c.The weakening lines are made after the protective strip has been removed, to mark together the weakening lines on the tab area 16c and the protective strip 17c. They can be made upstream or downstream of the formation of the hems 15c and the cheeks 181c, or even after the folding of the flaps. The left part of the [. Fig.18 ] is similar to that of the [ Fig.17 ].

[0068] With reference to the [ Fig.20 ], for the manufacture of an envelope 1d according to the fifth embodiment, or a variant of the fifth embodiment with gussets 18, the pre-cut zones 19 are identical to those of the [ Fig.16 ]. On the other hand, the closing adhesive layer 170d extends from hem 15 to hem 15, upstream of the cutting line 123 and downstream of the future upper edge 113. The protective strip 17d extends over the entire surface of the closing adhesive layer 170d and extends beyond the selvedges M1, M2. The left part of the figure represents the envelope 1 after cutting and after folding the upper flap 11d onto the lower flap 12d. The part of the protective strip 176 upstream of the cutting line remains on the upstream section, on the upper flap 11. The part of the protective strip 176 is found after folding inside the envelope 1 opposite the other part 175.

[0069] Optionally, the two parts of the protective strip 176, 175 are glued together by a reinforced glue 171d stronger than that of the closing glue layer 170 in a joining zone 177. This joining zone 177 is located on the panels 1760, 1750 of the parts 175, 176 of the protective strip 17d which extend beyond the hems 15 and in an area where the flaps 11d, 12d overlap. It was possible to deposit two zones of reinforced glue 171d on the panels 1760, 1750 upstream of the folding so that these parts 176, 175 stick together when they come together at the time of folding.

[0070] There [ Fig.21 ] represents the manufacture of envelopes 1e according to the sixth embodiment. The figure represents in the lower part the manufacture of an envelope 1e with one side without gussets and in the upper part, above a middle line M3, an envelope 1e with one side with a gusset 18. In practice, the envelope 1e will have no gussets or will be provided with gussets 18 on both sides. In the manufacturing method shown, the sheet M of flexible material is first unrolled and provided with perforation lines, as shown on the right of the [ Fig.21 ]. These perforation lines comprise a central line 124 extending in the transverse direction and located between future folds of the sides 141 of the envelope 1. The perforation lines further comprise a bottom line 125 also transverse and extending upstream of the central line 124, on either side of the ends thereof, with an oblique joining line 126. Pre-cut lines 195 extend parallel to the bottom line 125, downstream of the central line 124, join the central line 124 by oblique pre-cut lines 196 and delimit with the bottom line pre-cut areas 19e.

[0071] Closure glue is deposited by creating a layer of closure glue 170e partially covering the oblique pre-cut lines 196 between the future folds of the sides 141 and reinforced glue 171e is deposited as an extension of the closure glue 170e beyond the future folds of the sides 141. The protective strip 17e is deposited by extending transversely and completely covering the glue areas 170e and 171e.

[0072] The middle part of the [ Fig.21 ] shows a phase of forming a casing in which the selvedges M1, M2 are folded over the central zone of the sheet along the folds of the sides 141. The folded parts overlap each other and this overlapping part first receives glue, not shown, to form the upper flap 11. The upper part of the figure also shows the formation of a bellows 18, in a manner known per se which is not detailed here.

[0073] After the formation of a casing, it passes into a tearing station acting as a separation means which makes it possible to separate a section at the front of the casing. This type of station is conventional and is not detailed here. It is however specified that the casing is pinched on the one hand above the protective strip 17 and on the other hand upstream of the bottom line 125 to exert traction in the axial direction and obtain the separation of the section along the bottom line 125 and the central line 124. This produces a front tab on the end of the casing which protrudes from the lower flap 12 towards the front. The section was provided with the same front tab in the previous cycle so that this tab is used to close the front end of the section and thus form the casing 1e. An casing 1e is obtained as shown in the [ Fig.12 ].

[0074] In a variation, shown on the [ Fig.22 ], for the manufacture of the casings according to the seventh embodiment, a casing is formed in a similar manner. In the manufacturing method shown, the sheet M of flexible material is first unrolled and provided with pre-cut lines, as shown on the right of the [ Fig.22 ]. A future cutting line 123f is represented with a two-point line and a dash along which the casing will be cut to separate a section. The pre-cut lines comprise an eighth segment 198 which extends along the future side fold from the cutting line downstream and a ninth segment 199 which extends transversely from the end of the eighth segment 198 to the edge M1, M2. The pre-cut areas 19f are delimited between the eighth, the ninth segment 198, 199 and the future cutting line 123f.

[0075] Closure glue is deposited by creating a layer of closure glue 170f partially covering the eighth segments 198 and reinforced glue 171f is deposited as an extension of the closure glue 170f beyond the eighth segments. The protective strip 17f is deposited by extending transversely and completely covering the glue areas 170f, 171f. The formation of the casing is identical to the variant of the [ Fig.21 ].

[0076] After forming a casing, it passes into a cutting station 28 which separates a section at the front of the casing along the cutting line. The cut is a clean shear cut, although it could also be obtained by tearing as before. The formation of the bottom by folding means is not detailed.

[0077] In a variant not shown, and applicable to the sixth and seventh embodiments, the pre-cut segments can be produced after the formation of the casing, upstream or downstream of the bottom formation, by a cutting station which, by enclosing several layers of material, allows all the layers to be cut except one, that of the lower flap. This produces the cutting of the fifth segment 195 or the ninth segment 199.

[0078] The invention is not limited to the embodiments described by way of example, and is defined by the appended claims. Several protective strips can be adapted to the formation of the casings. The replacement of the bonding with reinforced glue can be replaced, as described in a variant of the first embodiment of the casing 1, by the use of protective strips without a release layer opposite the areas of reinforced bonding and the same glue as for the areas of closing glue.

Claims

1. Envelope formed by at least one sheet (M) of flexible material and comprising: - a lower flap (12), - an upper flap (11) superposed over the lower flap (12), the flaps (11, 12) being joined together by lateral edges (14) leaving an opening between the lateral edges (14), - at least one protection strip (17) on one coat of closing adhesive (170), the coat of closing adhesive (170) being designed to ensure the closing of the envelope (1) after removal of the protection strip (17), - along the opening, at least one precut area (19) that can be detached from the envelope (1), the coat of closing adhesive (170) extending at least partially over the precut area (19), characterised by the fact said envelope comprises reinforced means of linking (171) joining the precut area (19) to the protection strip (17) in a reinforced way with respect to the link between the protection strip (17) and the coat of closing adhesive (170).

2. Envelope as per claim 1, in which the reinforced means of linking comprises a coat of reinforced adhesive (171) on the precut area (19) and is covered by the protection strip (17), the protection strip (17) adhering better to the coat of reinforced adhesive (171) than to the coat of closing adhesive (170).

3. Envelope as per claim 1, in which the precut area is folded onto the back of the protection strip, the coat of closing adhesive on the precut area being stuck to said back of the protection strip, the reinforced means of linking being formed by the back of the protection strip (17) adhering better to the coat of closing adhesive than the face opposite the back adheres to the coat of closing adhesive.

4. Envelope as per one of the previous claims, in which the flaps (11a, 12a) are linked along the lateral edges (14) by bellows (18), each bellows (18) comprising two cheeks (181).

5. Envelope as per claim 4, in which the precut area (19a) extends over the whole width of the bellows (18) at least.

6. Envelope as per one of the previous claims, characterised by the fact it comprises at least two protection strips (17b, 17b') in parallel in a transversal direction, and at least one precut area (19b, 19b') for each protection strip (17b, 17b').

7. Envelope as per one of the previous claims, in which the edges (111, 121) of the upper flap (11) and of the lower flap (12) at the level of the opening are offset with respect to each other to leave a tab area (16) extending over the lower flap (12) between said edges (111, 121), the protection strip (17) extending over the tab area (16).

8. Envelope as per claim 7, in which the coat of closing adhesive (170) is subdivided into a first, second and third part (1701, 1702, 1703) extending transversely, the lower flap (12) comprising a first and second weakening line (161, 162) between the first and second part (1701, 1702), respectively the second and third part (1702, 1703), the protection strip (17c) comprising a third weakening line (173) aligned with the first weakening line (161) and a fourth weakening line (174) aligned with the second weakening line (162), the weakening lines (161, 162, 173, 174) extending across the precut area (19c).

9. Envelope as per one of the previous claims, in which the protection strip (17d) and the coat of closing adhesive (170d) are covered at least partially by the upper flap (11d).

10. Envelope as per claim 9, in which the protection strip (17d) and the coat of closing adhesive (170d) extend over the whole periphery of the opening.

11. Envelope as per one of the previous claims, in which the upper flap (11e, 11f) and the lower flap (12e, 12f) extend from the same sheet M shaped into a tube and stuck edge to edge (M1, M2).

12. Envelope as per claim 11, in which the edges (123f) of the flaps (11f, 12f) along the opening are aligned.

13. Envelope as per claim 11, in which the edge of the upper flap (11e) along the opening extends beyond the lower flap (12e), the precut area (19e) extending over the whole width of the upper flap (11e) set back from the edge of the lower flap (121e).

14. Envelope as per claims 1 to 10 in which the upper flap (11) and the lower flap (12) extend from the same sheet (M) of material folded along a transversal folding crease (13), perpendicular to the lateral edges (14) of the flaps, towards an interior face (120), the envelope (1) comprising a hem (15) formed on each lateral edge (14), the hem (15) of the upper flap (11) being stuck to the hem (15) of the lower flap (12) on seam faces (150).

15. Envelope as per claim 14, in which the hem (15) is stuck to the face opposite the seam face (150) along either the upper flap (11) or the lower flap (12).

16. Envelope as per claim 14 or 15, in which the hem (15) is linked to a central part of the flap by means of a cheek (181) folded over the central part, in such a way that a bellows (18) is formed by two cheeks (181) joined by the hems (15) stuck to each other.

17. Process for manufacturing an envelope (1) whereby: - at least one strip of flexible material in a continuous sheet (M) is unreeled in a longitudinal direction, - the precut lines (191, 192, 193, 194) are marked delimiting precut areas (19) on the strip, - a coat of closing adhesive (170) is applied extending on both sides of the precut lines (192, 194), and a protection strip (17) which covers the coat of closing adhesive at least outside the precut areas (19), in such a way that a precut area (19) is linked to the protection strip (17) in a strengthened way with respect to the link between the protection strip (17) and the coat of closing adhesive (170), - the strip is separated into sections, and each section is closed to form an envelope (1) as per one of the previous claims that has an opening bordered by the precut areas (19).

18. Process for manufacturing an envelope as per claim 17, whereby: - a hem (15) is formed with a hemmer on each edge (M1, M2) of the sheet (M) before folding, and adhesive is applied to the hems (15) over at least one length of an upper or lower flap (11, 12) on one seam face (150), - using a folding means (29), a fold of the strip is made along a transversal folding crease (13) to fold the upper flap (11) onto the lower flap (12) against an interior face (120) of the strip, the folding means (29) bringing for each edge (M1, M2) hem (15) against hem (15) by the seam face (150) in such a way as to obtain the adhesion of the hems (15) to each other to join the upper flap (11) and the lower flap (12) along the edges (M1, M2). - the sheet is cut by a transversal cut made by cutting means (28) to form a section before or after the folding of the flaps (11, 12) one onto the other, the section forming the envelope (1) at the end of the operations.

19. Process as per claim 18, whereby the transversal cut extends onto the protection strip (17d) to separate the protection strip (17d) into a first part (176) on the upper flap (11d) and a second part (176) on the lower flap (12d), the first part and the second part (175, 176) being at least partially superposed after folding.

20. Process as per one of the claims 17 to 19, whereby, to make an envelope (1c) as per the claim 8, the first and third weakening lines (161, 173), respectively the second and fourth weakening line (162, 174) are marked together, after application of the protection strip (17) on the sheet (M).

21. Process as per one of the claims 17 to 19, for the manufacture of an envelope (1) as per claim 13, whereby transversal perforation lines are made on the strip delimiting a rear end of a first envelope (1e) and a front tab (127) of a second envelope (1e) following the first between a central line (124) in the transversal direction and a bottom line (125) from which the front tab (127) protrudes forwards, the bottom line (125) also delimiting the precut area (19e), the sheet (M) is shaped into a tube, then the first and second envelope (1e) are separated by axial traction on the tube by gripping the first envelope (1) on the precut areas (19e) so that the separation is made along the central line (124) and the bottom line (125).

22. Machine for manufacturing flexible envelopes, characterised by the fact it comprises: - unwinding means (201) for unreeling at least one sheet (M) of flexible material in a continuous sheet (M) in a longitudinal direction, - marking means (202) for marking precut lines on the sheet delimiting precut areas (19), - application means (23) for applying a coat of closing adhesive (170, 171) at regular intervals, extending on both sides of the precut lines on the sheet (M), and a protection strip (17) that covers the coat of closing adhesive at least outside the precut areas (19), - separation means (28) for separating the sheet (M) into sections (T) along the rear edge of the section, - folding means (29) for closing each section (T) to form an envelope (1) as per one of the claims 1 to 16 with an opening along the rear edge bordered by the precut areas (19), - the machine being configured to implement the process as per one of the claims 17 to 21.

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