EP3710242B1 - Method and machine for producing a stack of bags - Google Patents

Description

The invention relates to the field of packaging bags made of flexible material such as paper or plastic film, or an assembly of the two, the bags being collected in the form of a stack. It concerns a process and a machine provided for the manufacture of said bags and their stacking.

PRIOR ART

In the field of packaging, particularly food packaging, flat bags of flexible material are widely used for retailing foodstuffs such as bread, fruit, vegetables or bulk materials. Such bags are often mainly made of more or less thick paper, but can also include parts of synthetic plastic material, for example transparent.

Such a bag according to one of the known manufacturing techniques comprises a first wall and a second wall connected together directly or via bellows in a longitudinal direction. At one of the ends of the bag in the longitudinal direction, the first wall is extended by a first tab which projects from the second wall. At the other end, a second tab coming from the second end is folded, turned over and glued to the first wall in order to form a bottom and thus close the end of the bag.

In another embodiment, the second tab is also an extension of the first wall, so that when the two tabs are folded, they are folded back onto the second wall, leaving the first free. wall. In this case we are talking about a clutch bag. We also make envelopes in the same way. Subsequently, the term “pocket bag” will also designate an envelope.

In certain uses, it is planned to stick the first tab on the second wall to close the bag or envelope. One of the techniques used consists of providing a layer of glue on the second wall and protecting it with a protective strip of silicone paper so as to be non-stick. In use, the protective strip is removed and the first tab is folded and applied against the glue layer so as to close the end of the bag or envelope.

To form such bags industrially, a technique is known consisting of forming a hose from a continuous sheet in a roll, separating sections from this hose and closing one of the ends of the section to form the bag. The hose can also be made up of a plastic part, for example transparent, assembled by gluing with the paper by covering the respective edges.

The document FR 786 579 shows several examples of this technique. The strip of paper is provided at regular intervals with lines of transverse perforations.

The hose is formed by folding each edge over the central portion and gluing the two edges together along a central junction. The hose thus formed and flattened passes between a pair of drive rollers which drive the hose at a constant speed. The hose passes between a pair of separator rollers rotating with a peripheral speed greater than that of the drive rollers before being driven to a folding device. One of the rollers of the pair of separation rollers is hollowed out over a large part of its periphery so as to only come into contact with the other roller intermittently. During this contact, the hose is placed in tension between the drive rollers and the separation rollers so as to obtain the separation of a section coming from the hose at the level of the perforations, provided in such a way that the first tab is formed in the extension of the first wall towards the rear of the section and the second tab remains at the front of the hose in the extension of the second wall. This second leg will be found on the next section. The front part of the section which has just been separated is then grasped by the folding device. The second tab is glued and folded by the folding device to close the front part of the section. The folding device brings the finished bag into a vertical position on a table on which the bags accumulate and form a stack of free bags between them.

Other examples of processes and machines for producing such bags can be found in the document FR 1 270 400 A1 (cover only).

The stack of bags is intended for manual use, which meets most of the demand. However, certain uses require significant productivity. In the case of bags to be closed, provided with an adhesive protected by a peelable strip, entering the strip can only be done manually and is delicate. In addition, it is necessary to dispose of the strip which forms waste.

The document US 4,502,599 shows a stack of flexible bags, preferably made of plastic, provided with a repositionable glue on a tab and making it possible to maintain the closure of the bag after folding the tab. In the stack, the glue adheres to the back of the tab of the adjacent bag. Such a stack of bags facilitates repetitive packaging operations. Removing a bag from the end of the pile allows you to release the glue layer by peeling it off from the non-stick layer. The bag can then be used directly, without having to carry out any specific operation to release the glue layer. Once filled, the bag can be closed by applying the first tab to the layer of glue. However, this technique only applies to bags fitted with repositionable glue and does not allow permanent closure.

The document US 6,142,302 shows a method and a machine for manufacturing a stack of flexible bags, according to the preamble of claim 1.

To solve these problems, the invention aims to provide a method and a machine for producing such a stack of bags.

DESCRIPTION OF THE INVENTION

With these objectives in view, the subject of the invention is a method according to claim 1 and a machine according to claim 5. A stack of flexible bags is thus manufactured, each bag comprising a first flexible wall extended by a first tab to a first ends of the bag and a second flexible wall adjacent to the first wall and from which the first tab protrudes, the stack being characterized in that it comprises means of connection between each bag, the connection means comprising a non-stick layer on the first wall of a first bag and a layer of glue ensuring a temporary connection with the non-stick layer and which also adheres to the second wall of the bag adjacent to the first bag, the layer of glue being able to stick the first tab on the second wall after the bag is detached from the pile.

Such a stack of bags opens up new perspectives for facilitating repetitive packaging operations. On the one hand, removing a bag from the end of the pile allows the glue layer to be released by peeling it off from the non-stick layer. The bag can then be used directly, without having to carry out any specific operation to release the glue layer. Once filled, the bag can be closed by applying the first tab to the layer of glue. On the other hand, by pulling the bag out of the stack, the first and second walls are caused to move apart, which opens the bag which is then ready to receive the object to be packaged, possibly even before being detached from the battery. The glue is for example a pressure-sensitive acrylic glue supplied by Henkel under the name Euromelt 707 or Technomelt EM 707, or Technomelt PS 8707. Other glues from the same supplier are also suitable, for example Technomelt Henkel PS 578. This glue can be applied hot between 150 and 180 °C. The non-stick layer is typically based on a silicone polymer.

According to a first embodiment, the non-stick layer is carried by a strip attached to the first wall. It is thus planned to form the non-stick layer on a substrate which is deposited and glued to the wall of the bag. We thus have a large choice of non-stick layer which is placed on the surface just necessary, the quality of the first wall is preserved over most of its surface.

According to a second embodiment, the non-stick layer extends over the entire surface of the first wall. This eliminates the need for an operation and a device for depositing the attached strip.

According to an improvement, the stack of bags includes separators separating a predetermined number of bags. In addition to serving as a marker to facilitate bag counting, the separators can serve as support to facilitate stack handling.

According to one variant, the glue layer is made with a repositionable glue. The bag can then be opened and closed several times by the user.

According to another variant, the glue layer is made with a definitive glue. This creates a security closure of the bag, the opening requiring the bag to be torn.

We use the classic flat bag manufacturing process in which we add a step for laying a non-stick layer and a step for laying a layer of glue which is thus brought together and to form the stack of bags. as described previously.

According to a first embodiment of the method, the bag is closed by gluing a second tab from the second wall to the first wall, the layer of glue is deposited on the non-stick layer before the formation of the stack, and the glue layer is transferred to the second wall of the adjacent bag during the formation of the stack. This configuration concerns bags whose legs are an extension of different walls. With known folding devices, the sections are driven on a drum and a transverse blade is approached which forces the second tab into a groove to fold the tab. Previously, glue was placed on the wall opposite to that extended by the second leg. The second tab is then folded down following the rotation of the drum and is brought into contact with the glued surface, so as to stick the second tab and close the bottom of the bag. Thus, the second tab is always in the extension of the wall which comes into contact with the drum on the upper part of the latter, to be able to glue the opposite wall and carry out the folding.

In the first embodiment, the wall opposite to that which extends the first tab is the first wall which must receive the anti-adhesive layer. However, it is not possible to glue the second wall upstream of the drum, because the bags are supported by this second wall during their transport. The layer of glue would inevitably come into contact with the rollers or strips used for this transport, which would cause the bags to stick to these elements and is not acceptable. Also, it is proposed to deposit the layer of glue on the non-stick strip which is oriented upwards, and that this is transferred to the second wall and adheres there when the bags are stacked.

According to a first variant, a strip comprising a fixing layer, a substrate, the release layer and the glue layer is deposited on the first wall, the strip being deposited on the first wall on the side of the fixing layer. The removal of the release layer and the adhesive layer are carried out simultaneously, which makes it possible to use a single device for the removal of the release layer and the adhesive layer. The strip is prepared specifically for application, by depositing on the substrate the fixing layer on one side, and the glue layer on the other side which carries the non-stick layer. This band is manipulated by non-stick treated rollers which come into contact with the side carrying the layer of glue and which deposit the strip on the wall of the bag. The adhesion properties are chosen such that the strip remains stuck to the wall by the fixing layer and the adhesive layer detaches from the rollers which carry it and remains on the strip.

Optionally, the adhesive layer is protected by a siliconized protective sheet which allows the strip to be pressed during application and which is removed immediately afterwards.

According to a second variant, a strip comprising a fixing layer, a substrate and the release layer is deposited on the first wall, and in a following step the glue layer is deposited on the release layer. This variant allows the use of a more standard self-adhesive strip with the corresponding installation device and leaves the choice of the nature of the glue for the glue layer.

According to a variant, the layer of glue is deposited downstream of the closure of the bottom of the bag. Depending on the existing machines that we would like to adapt to implement this process, it may be interesting to deposit the glue at this phase of the process.

BRIEF DESCRIPTION OF THE FIGURES

• ▷ la figure 1 est une vue en perspective d'une pile de sac conforme à un premier mode de réalisation ;
• ▷ la figure 2 est une vue similaire à la figure 1 d'une pile de sacs conforme à un deuxième mode de réalisation ;
• ▷ la figure 3 est une vue d'un sac isolé de la pile de la figure 1, vu du côté de la première face ;
• ▷ la figure 4 est une vue du sac de la figure 3, vu du côté de la deuxième face ;
• ▷ la figure 5 est une vue schématique d'une machine pour fabriquer une pile de sacs conformes au premier mode de réalisation de l'invention ;
• ▷ la figure 6 est une vue partielle en coupe de la pile de la figure 1,
• ▷ la figure 7 est une vue similaire à la figure 5 d'une machine pour fabriquer une pile de sacs conformes au deuxième mode de réalisation de l'invention.

Other advantages may still appear to those skilled in the art on reading the examples below, illustrated by the appended figures, given for illustrative purposes, among which:

• ▷ the figure 1 is a perspective view of a stack of bags according to a first embodiment;
• ▷ the figure 2 is a view similar to the figure 1 a stack of bags conforming to a second embodiment;
• ▷ the Figure 3 is a view of an isolated bag from the pile of the figure 1 , seen from the side of the first face;
• ▷ the Figure 4 is a view of the bag of the Figure 3 , seen from the side of the second face;
• ▷ the Figure 5 is a schematic view of a machine for manufacturing a stack of bags conforming to the first embodiment of the invention;
• ▷ the Figure 6 is a partial sectional view of the stack of the figure 1 ,
• ▷ the Figure 7 is a view similar to the Figure 5 of a machine for manufacturing a stack of bags conforming to the second embodiment of the invention.

DETAILED DESCRIPTION

A stack P of flexible bags 10 according to a first embodiment of the invention, is shown on the figure 1 . Each bag 10 of the pile P comprises, as shown on the figures 3 and 4 , a first flexible wall 11 extended by a first tab 13 to a first 101 of the ends of the bag 10 and a second flexible wall 12 adjacent to the first wall 11 and from which the first tab 13 protrudes. The bag 10 further comprises a second tab 14 coming from the second wall 12 folded and glued to the first wall 11 to close the bag 10 at the second end 102, opposite the first end 101, as shown on the Figure 3 .

The stack P comprises connection means 9 between each bag 10. These connection means 9 comprise a non-stick layer 91 on the first wall 11 of a first bag 10, as shown in the Figure 3 , and a layer of glue 92 ensuring a temporary connection with the anti-adhesive layer 91 and which also adheres to the second wall 12 of the bag 10 adjacent to the first bag 10, as shown in the figure 4 . The layer of glue 92 is capable of sticking the first tab 13 to the second wall 12 after the bag 10 has been detached from the stack P in order to close the first end 101 of the bag 10.

The non-stick layer 91 is for example carried by a strip attached to the first wall 11, as shown in the Figure 6 .

In a second embodiment of the invention, the stack P' comprises separators S separating a predetermined number of bags 10', as shown in the figure 2 . Each separator is fixed by gluing to one of the bags surrounding it. In this example, the bags 10' are envelope bags, that is to say that the first 13' and the second tab 14' come from the first wall, only the second wall 12' being visible on the figure 2 .

The glue layer 92 can be made with a repositionable glue or with a permanent glue.

A machine for manufacturing pile P of bags 10, as shown in the Figure 5 , comprises in a manner known per se a station 4 for forming a hose 1 from a strip of a flexible material 1a such as raw or pre-printed paper, an aluminum or plastic film or equivalent or a mixture of these materials. The strip of material 1a is unwound from a spool onto a reel, not shown. It can be printed beforehand or when it comes out of the dispenser. The hose 1 is formed with or without bellows, but this characteristic has no impact on the invention. The machine then successively comprises, in the direction of transport of the hose 1 indicated by the arrow F1, a pair of holding rollers 3, a pair of tearing rollers 6, a bottom forming station 7 then a stacking station 8 for form the pile P of bags 10.

To specifically implement a method according to the invention, the machine further comprises first depositing means 2 for depositing the non-stick layer 91 and second depositing means 5. The first depositing means 2 are for example provided for deposit a strip 93 of self-adhesive silicone paper, that is to say comprising a fixing layer 930 which is brought into contact with the hose 1 to be deposited there. In an example not shown, glue is first deposited on the hose, then the silicone strip 93 is deposited on the glued area to be glued there, the non-stick face 91 remaining visible. The document GB390455 shows an example of a process for depositing a paper reinforcement on a hose which can be used here for removing the non-stick strip.

The strip 93 comprises for example the fixing layer 930, a substrate 931 and the anti-adhesive layer 91, the strip 93 being deposited on the first wall 11 on the side of the fixing layer 930.

The second deposition means 5 are designed to deposit a layer of glue 92 on the silicone strip, that is to say on the non-stick layer 91.

The operation of the machine is now described in broad terms, the details of the manufacture of a bag 10 being already known. The strip of flexible material 1a is unrolled, provided with lines of transverse perforations at regular intervals then formed into a hose 1. The hose 1 receives the anti-adherent layer 91 by the first depositing means 2 on a first wall 11 of the hose then is separated into sections 1b at the front of the hose 1 by the combination of the action of the pairs of holding rollers 3 and pullers 6, in a manner known per se. The separation is carried out along the lines of perforations which have been provided in such a way that the first flexible wall 11 of the hose 1, in the upper part, is extended by a first tab 13 to a first 101 from the ends of the bag 10 towards the rear of the section, and a second tab 14 extends the second wall 12, in the lower part of the hose at the second end 102 towards the front of the section. A layer of glue 92 is deposited on the anti-adhesive layer 91 by the second deposition means 5. In a manner known per se, the second tab 14 is folded over the first wall 11 and glued in order to close the bag 10 by the bottom forming device 7. Finally, the bags 10 arrive at the stacking station 8 where they are stopped in a vertical position, the first wall 11 of the bag 10 which arrives being placed along the second wall 12 of the bag 10 who preceded him. When the bags 10 are thus side-by-side, the layer of glue 92 carried by the anti-adhesive layer 91 comes into contact with the second wall 12 of the previous bag 10 and adheres there. The battery P according to the invention is thus constituted.

In a second embodiment outside the invention, the bags 10' are of the envelope type, also called pouch, that is to say that the two legs extend the first wall, as shown in the figure 2 . In the known manufacturing process for this type of bag 10', the first wall is in the lower position, and the second wall 12' in the upper position. The machine, as shown on the Figure 7 , is modified by the insertion of an additional pair of rollers 6', between the pairs of holding rollers 3 and tearing rollers 6, and an additional tearing step removes waste at the first end 101 of the section of hose 1b in order to form the first tab 13' as an extension of the first wall in the lower position.

In this configuration, the first depositing means 2' operate on the first wall, therefore in the lower position, to deposit the non-stick layer 91, while the second depositing means 5' always act in the upper part, to deposit the layer of glue 92 on the second wall 12'. When the bag 10' arrives at the stacking station, the previous bag 10' presents its first wall 11, provided with the anti-adhesive layer 91, which assembles with the glue layer 92 on the second wall 12' of the bag 10' which arrives to form the connecting means 9. Intermittently, the separators S are deposited on the bag downstream of the bottom forming device 7 by third depositing means 50.

The invention is not limited to the embodiments which have been described by way of example. The second depositing means could be integrated into the bottom forming device 7 in order to deposit the glue layer 92 at the latest in the path of the bag 10. Likewise, the first depositing means 2 could be placed after the tearing rollers 6 or also integrated into the bottom forming device 7. In this case, the strip which is deposited on the first wall 11 may comprise the fixing layer 930, the substrate 931, the anti-adhesive layer 91 and the glue layer 92, the strip being deposited on the first wall 11 on the side of the fixing layer. In order to make it possible to handle the strip, it is protected by a protective sheet which is removed after placing the strip on the section of hose. The bags presented are flat, but they could just as easily be provided with side gussets, formed during the formation of the hose.

Claims (5)

1. Bag manufacturing process for forming a stack (P, P') whereby a tube is made with a strip of flexible material, a portion of tube is separated at the front of the tube forming a first flap (13) at the rear of the portion of tube, the first flap (13) prolonging the first wall (11) of the portion beyond the end of the second wall (12) adjacent to the first wall (11), a bag (10) is formed with each portion of tube by closing the front of the portion of tube (1b) by bonding a second flap (14) extending from the second wall (12) on to the first wall (11), and a stack (P, P') of bags (10) is formed, the first wall (11) of the first of the bags (10) being against the second wall (12) of the adjacent second bag (10) attached to the first bag by means of attachment (9), characterised by the fact that an anti-adhesive coating (91) is applied to the first wall (11) of the first bag (10) and a coat of adhesive (92) is applied to the anti-adhesive coating (91) before the formation the stack (P) and thus forming the means of attachment (9), and the coat of adhesive (92) is transferred on to the second wall (12) of the adjacent bag (10) when the stack (P) is formed, the coat of adhesive (92) being able to bond the first flap (13) on to the second wall (12) after the bag (10) has been detached from the stack (P, P').
2. Process as per claim 1 whereby a strip (93) comprising an attachment layer (930), a substrate (931), the anti-adhesive coating (91) and the coat of adhesive (92), is applied to the first wall (11), the strip (93) being applied on to the first wall (11) on the attachment coating (930) side.
3. Process as per claim 7 whereby a strip (93) comprising an attachment layer (930), a substrate (931) and the anti-adhesive coating (91), is applied to the first wall (11), and in the next step the coat of adhesive (92) is applied on to the anti-adhesive coating (91).
4. Process as per one of the claims 1 to 3 whereby the coat of adhesive (92) is applied downstream of the closing of the bottom of the bag (10).
5. Machine for manufacturing flexible bags including a tube-forming device (4) for forming a tube from a strip of flexible material (1a), a separation device (3, 6) for separating a portion of tube (1b) at the front of the tube (1) while forming a first flap (13) to the rear of the portion of tube, the first flap (13) prolonging the first wall (11) of the portion beyond the end of the second wall (12) adjacent to the first wall (11), a bag-bottom forming device (7) for forming a bag (10) with each portion of tube by closing the front of the portion of tube by bonding a second flap (14) extending from the second wall (12) on to the first wall (11), the coat of adhesive (92) is transferred on to the second wall (12) of the adjacent bag (10) when the stack (P) is formed, and a stacking device (8) for forming a stack (P) of bags (10), the first wall (11) of the first of the bags (10) being against the second wall (12) of the adjacent second bag (10), the machine being characterised by the fact it includes a first means of application (2) for applying an anti-adhesive coating (91) on to the first wall (11) of the first bag (10), and a second means of application (5) for applying a coat of adhesive (92) on to the anti-adhesive coating (91) before the formation of the stack in such a way that the coat of adhesive (92) is transferred on to the second wall (12) of the adjacent bag (10) when the stack (P) is formed, the machine acting according to the process according one of the claims 1 to 4.

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