EP2844595B1 - Method for forming bag packs, and corresponding machine - Google Patents

Description

Technical area

The present invention relates to a method of forming packets of bags, in particular of flexible and long bags, at the output of a production line of said continuous. It relates to a machine implementing such a method.

In the description below, references in brackets ( [] ) refer to the list of references at the end of the text.

State of the art

A certain type of bag is made of flexible material such as paper, plastic film or a combination of both and is intended in particular for the packaging of food products such as bread or bulk products. The size of the bag is adapted to its use, so that some bags have a long and narrow shape. This is the case, for example, bags intended for packing bread sticks.

These bags are produced on a production line that starts from a roll sheet, then forms a roll that is flattened, cut and closed at one end by a glued flap. In some cases, a flap is also formed at the opposite end to the closed one. The bag comes out of this chain flat on a conveyor belt, the flap being located forward and projecting away from the conveyor belt, as shown in FIG. figure 3 .

In some configurations, the bag is driven vertically to a receiving table on which a stack of bags is formed. The battery pushes a bracket that holds one end of the stack. The document DE 20 2004 005723 U1 [ ¹ ] shows such a configuration. Such a provision is satisfactory when the arrival speed of the bags is not not too high and that the bags have a good intrinsic behavior that derives from the weight of the film and dimensional relationships. This is not the case for long-form bags. These bags have an outfit that is not enough to stand against the square.

Also known is a stack forming machine having a conveyor extending horizontally above a receiving table. The conveyor pinches a leading edge of an arriving bag and takes it over the reception table to release it when the bag is entirely above the reception table. The bag is then stopped by a stop in the axis of displacement of the bags. Such a machine is limited in speed by the fact that beyond a certain speed, the bags are deformed and damaged when arriving against the stop.

The document WO 91/08974 A1 [ ² ] shows a paperboard cutting and stacking machine. After cutting, the sheets are accelerated to scroll on a table separately. Means of forming recovery can slow down the sheets and arrange them in recovery. The set of leaves then move at a reduced speed. The sheets are then transported by means of transport to a reception table. The leaves come to a stop against a cleat and pile up on the reception table.

When the battery is full, the machine must be stopped in order to remove the stack of sheets or evacuate the receiving table with the stack and replace the table with a new table. Such an installation is not suitable for bag production because some bags produced in the transient shutdown and recovery phases that are imposed for the evacuation of the battery may not meet the quality requirements and must be downgraded. .

Other methods and machines for forming packets of bags are disclosed in US 3908527A and US 3390619 A1 . The invention aims to provide a method and a machine for forming packets of bags, especially long format bags, at high speed and without interruption of the production of the bags during the evacuation packages.

Description of the invention

With these objectives in view, the subject of the invention is a method of forming packages of flat bags in which a continuous line of bags moving in a forward direction is received, the bags are brought over receiving table on which the bags are stacked by being stopped in the direction directed in advance by a stop, characterized in that transforms the queue of continuous bags into a line of overlapping bags before stacking them, and a separation of the bags above the reception table is effected by separating means comprising a separation device, during which the separation device is introduced by a movement in a direction of separation perpendicular to the plane of the bags. between a predecessor bag and a follower bag in the overlapping queue so that when the follower bag comes to rest against the stop, it is supported at least partially by the yens of separation.

There are thus means for retaining above the receiving table the bags that continue to be produced while the bags stacked to the predecessor bag are evacuated. The collection of the bags makes it possible to obtain a significant reduction in the speed of movement of the bags. The separation device, by being introduced from above the line of bags, can be put in place very quickly, without risking a collision with a moving bag whose speed has already been reduced. The bags that continue to be produced are stored above the trailing bag that is retained, it is not necessary to interrupt their production. This makes it possible to guarantee permanent conditions for the production of the bags and to limit the dispersion of the characteristic properties of the bags. The separation device can be implemented automatically, for example after the passage of a predetermined number of bags since the start of production or the previous bag evacuation operation. The packets that are thus formed are formatted reproducibly and parameterizable. Moreover, as the speed of movement of the bags has been reduced by the recovery, it no longer constitutes a limitation of the rate of production of the bags. It is thus possible to reach high speeds while forming simple packs to handle.

In particular, the follower bag and the predecessor bag are moved at least at the rear edges of the bags, and, the separation means comprising a separation table, is introduced the separation table in the direction in advance between the predecessor bag and the follower bag to support the follower bag. The separation table supports the follower bag and those that stack on it very safely. The introduction of the separation table can be done even if the follower bag is still partially supported on the predecessor bag. The installation is easily adapted to bags of different lengths by simply changing the stroke of the separation table.

According to a first embodiment, the separation device is introduced to a first level and until the predecessor bag is in abutment, then the separating device is moved to a second level while maintaining the rear edge. the follower bag by a flexible blade protruding in the direction directed in advance, to separate the follower bag and the predecessor bag at the rear edges. At the first level, the separation device maintains the conditions allowing the predecessor bag to reach the stop, thus avoiding pressure on said bag. The combination of the flexible blade and the separating device then makes it possible to obtain the spacing of the bags, at least at the rear edge, when the device forces the rear edges of the bags under the predecessor bag to pass beyond the flexible blade, while the follower bag is retained after the passage of the separation device. This creates a space in which the separation table can be introduced. The first and second level can represent a position or a force. Strength has the advantage of being able follow the continuous stacking of the bags. The position has the advantage of being easier to control.

According to a second embodiment, also using the separation table, the follower bag and the predecessor bag are moved apart by lowering the receiving table, the separating device supporting the rear edge of at least the follower bag. In this configuration, the space is created by lowering the receiving table that supports the bag package surmounted by the predecessor bag. The separation table can then be introduced to support the bags along their entire length.

According to an additional step, after the introduction of the separation table, the separation device is continued by retracting. The follower bag and the bags that follow it are thus supported by the separation table, while the separation device can resume its place, waiting to separate the next packet. The retraction is for example a movement perpendicular to the direction directed in advance and to the separation movement. The separation device is thus released to be able to resume a position in which the device is ready to start a cycle again.

According to a third embodiment, the follower bag is supported by the separation device essentially over the entire length of the bag, and the receiving table is lowered, the separation device supporting the follower bag. In this case, the separation table is dispensed with, the support of the bags being provided solely by the separation device. This embodiment has the advantage of requiring fewer organs, however the separation device must be calibrated to receive and support the follower bag over most of its length. The support parts of the follower bag must be able to be adapted to the length of the bags. This can be done by providing different sets of support parts.

According to an improvement, the position of the separation device is continuously adjusted to maintain the upper level of the bag stack on the follower bag at a constant level. We thus maintain the same receiving conditions of the bags as and when the pack of bags, when it is supported by the separation device.

Likewise, the position of the receiving table is continuously adjusted to maintain the top level of the bag stack at a constant level. This applies when the receiving table supports a pack of bags on which new bags pile up.

According to an improvement, the upper level of the stack is held against higher means of transport placed above the reception table and accompanying the bags arriving on the stack in the direction directed in advance to the stop. The upper means of transportation help the bags at the top of the stack to reach the stopper, especially when the top level of the stack is kept constant by moving the receiving table, which also maintains a slight pressure between the stack and the higher means of transport.

In a complementary step, after the follower bag is supported, the receiving table is lowered, the pack of bags supported by the reception table is evacuated, the reception table is raised and the separation means are retracted to transfer the bag. follower on the reception table. We thus find a position similar to that at the beginning of the cycle. The formed package can then be processed in a variety of ways, by being manually taken over for wrapping, being manually or automatically circled, or being automated palletized.

In particular, the separation device is moved in a square cycle in a plane perpendicular to the direction oriented in advance, one of the movements of the square cycle being the introduction of the separation device. Such a movement can easily be implemented by the combination of two translation guide systems. We must understand the square cycle as the succession of translation steps, and not as the trajectory actually described by the device of separation. This one is rather rectangular, but it could also be a parallelogram.

According to a constructive arrangement, the first transfer means move at a speed lower than the arrival speed of the bags at a distance from one another, a reel upstream of the first transfer means moves the rear edge of a first bag in a folding direction perpendicular to the plane of the bags until a second bag that follows the first bag covers the rear edge of the first bag. By thus making a line of bags overlap, greatly reduces the speed thereof, so that they can be handled more easily later. The use of a reel is one of the possible ways to obtain this recovery.

According to an improvement, a brake near and downstream of the reel plate the first bag against the first transfer means near the rear edge of said first bag. By slowing the bag upstream, it avoids putting the bag in axial compression which could flambé the bag.

According to a further improvement, the bags are coated recovery against the first transfer means by a roller, the bag passing under the roller after being braked by the brake. This ensures that the recovery bags are driven by the first transfer means.

In the case where each bag has a tab not glued folded to be folded on a first side of the bag, the bags are placed so that they reach the first means of transfer the tongue forward and the first face oriented in the direction of drawdown . The tongue is thus held against the bag that precedes and has no risk of catching with another bag, even by sliding on the previous bag during stacking.

The invention also relates to a machine for forming packets of bags receiving a continuous line of bags moving in one direction oriented in advance, a receiving table on which the bags are stacked by being stopped by a stop, the machine being characterized in that it comprises means for slowing down to receive the continuous line of bags and form a line of bags in recovery on first transfer means, separating means receiving the queue of overlapping bags from the first transfer means and comprising a separating device sliding in a movement perpendicular to the plane of the bags between a retracted position and a position separation device for introducing between a predecessor bag and a follower bag in the separation position so that, when the follower bag comes to stop against the stop, it is supported by the separation means, and in that the machine implements the method as described above.

In a particular configuration, the machine comprises means for reversing the tab bags, the turning means comprising a pair of reversing transport means delimiting between them a path drawing about a half-turn. Some bag making machines provide a queue of bag whose first face, on which the tabs are intended to fold down, is oriented upwards. It is then necessary to return them so that the first face is placed opposite the first means of transfer.

Brief description of the figures

• la figure 1 est une vue de côté d'une machine conforme à un mode de réalisation de l'invention ;
• la figure 2 est une vue du détail II de la figure 1 ;
• la figure 3 est une vue schématique de la disposition des sacs en provenance d'une machine de fabrication desdits sacs ;
• la figure 4 est une vue schématique des sacs mis en recouvrement ;
• les figures 5 et 6 sont des vues schématiques de côté de l'empilement des sacs dans des phases particulières du procédé selon l'invention ;
• les figures 7 à 11 sont des vues schématiques en coupe selon la ligne VII-VII de la figure 6, selon différentes étapes du procédé selon l'invention ;
• la figure 12 est une vue similaire à la figure 6 pour un deuxième mode de réalisation de l'invention ;
• la figure 13 est une vue similaire à la figure 6 pour un troisième mode de réalisation mode de réalisation de l'invention.

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

• the figure 1 is a side view of a machine according to an embodiment of the invention;
• the figure 2 is a detail view II of the figure 1 ;
• the figure 3 is a schematic view of the arrangement of the bags from a machine for manufacturing said bags;
• the figure 4 is a schematic view of the bags being recovered;
• the figures 5 and 6 are schematic side views of the stack of bags in particular phases of the method according to the invention;
• the Figures 7 to 11 are schematic sectional views along line VII-VII of the figure 6 according to different steps of the process according to the invention;
• the figure 12 is a view similar to the figure 6 for a second embodiment of the invention;
• the figure 13 is a view similar to the figure 6 for a third embodiment of the invention.

DETAILED DESCRIPTION

In the following description, the top and bottom refer to the orientations in the normal position of use of the machine. The front edge of the bag is the one that comes first in the direction of movement of the bag, the rear edge being opposite to the front edge.

First embodiment

A bagpack forming machine, according to a first embodiment of the invention and shown on the figures 1 and 2 , is intended to receive bags 1 of a bag making machine, not shown, out of which the bags 1 are delivered one by one, flat in a continuous line, the bags 1 being separated from each other by a small gap d, as shown on the figure 3 . The continuous queue arrives in the packet forming machine according to a path symbolized by the arrow F1 on the figure 1 . The bags 1 comprise for example a tongue 10 along a front edge 11 which is first in the direction of advance of the line of bags 1. The tongue 10 is folded on a first side 13 of the bag without being glued which is oriented towards the up out of the manufacturing machine. The packet forming machine has turning means 2 for placing the bags 1 with the first face 13 facing downwards, slowing means 3 for receiving the continuous line of returned bags 1 and forming a line of bags 1 in recovery moving in a direction oriented in advance F3 on first transfer means 31, and a receiving table 4 on which the bags 1 in recovery from the first transfer means 31 are stacked by being stopped by a stop 5.

The turning means 2 comprise a pair of reversing transport means 21, 22 delimiting between them a turning course drawing about a half-turn. This turning course extends from one end to the other of the packet forming machine passing into the lower part of the machine and then relying on a wheel 23 which performs the U-turn, shown on the part left of the figure 1 , to end in a substantially horizontal direction of travel, from left to right on the figure 1 . The overturning conveyance means 21, 22 conventionally comprise one or more parallel conveyor belts, looped, guided by rotary mounted rollers some of which perform the drive, in a manner not detailed here. For the sake of simplification of the description only, it is considered that each element of the pair of transport means comprises only one conveyor belt. The bands of the first and second reversing conveyance means 21, 22 of the pair face each other on the reversal path of the bags 1, so as to grip them, then follow a respective first and second return path 211, 221. .

Referring to the figure 2 the first turning conveyance means 21 comprise a first roller 212 which guides the first conveyor belt and directs it towards the first return path 211. The first roller 212 is placed so as to be substantially tangent to the first conveyor 21 a horizontal plane tangential to the wheel 23, the first return path 211 being oriented at this level downwards. On the other hand, the second turning conveyor means 22 comprise a second roller 222 which guides the second conveyor belt and directs it towards the second return path 221. The second roller 222 is placed so as to be substantially tangent to the tangent horizontal plane. at the wheel 23, the second return path 221 being oriented at this level upwards. The second roller 222 is closer to the wheel 23 than the first roller 212, so as to leave free a transfer zone Z above the first conveyor belt.

The slowing means 3 comprise the first transfer means 31, the second transfer means 32, a reel 33 and a thrust roller 34. The first transfer means 31 comprise a conveyor belt, part of which extends by having a face 310 facing upwards in a plane in continuity with the overturning conveyance means 2. The conveyor belt also has a ramp 311, rising in the direction of the forward direction F3, just after the first roller 212. The reel 33 is placed opposite this ramp 311. The reel 33 has a shaft 331 rotatably mounted along a transverse axis in the direction of the arrow F2, that is to say in a direction accompanying the movement of the bags 1 in the forward direction F3. The reel shaft 33 further comprises blades 332 curved upstream, that is to say opposite the arrow F2. The path of the blades 332 extends in the area between the ramp 311 and the trajectory of the bags 1 in the forward direction F3.

The second transfer means 32 have a portion which extends above the transfer zone Z and in the direction of advance above the first transfer means 31. They comprise several conveyor belts leaving between them passages for the blades 332 of the reel 33. The brake 35 is located near and downstream of the reel 33, facing the end of the ramp 311. It also comprises a shaft 351. rotatably mounted and a cam 352 protruding from the shaft. The brake 35 and the reel 33 comprise drive means, not shown, which drive them synchronously.

The roller 34 is rotatably mounted freely about an axis also transverse. Its support 340 is mounted mobile in translation so as to be placed at an adjustable distance from the reel 33. The roller 34 remains in support towards the first transfer means 31.

The first and second transfer means 31, 32 separate at a nose 36 above the reception table 4. The reception table 4 could be flat, but in this case, it comprises a series of bars 40 arranged parallel to each other in a substantially horizontal plane and in a transverse direction. The reception table 4 is slidably mounted vertically. The machine also comprises a transfer table 6, parallel to the receiving table 4, to receive the packets formed and supported by the receiving table 4. The transfer table 6 has grooves in which the bars are housed when the table of reception 4 is in its lowest position. The machine further comprises an ejection grid 7 movable in a transverse direction to slide the formed package and deposited on the transfer table 6 to a transverse position in which it can be resumed, manually or by means not detailed here.

The machine further comprises separation means 8 comprising a separation device 80 and a separation table 81. The separation device 80 is placed just downstream and above the nose 36, at the outlet of the transfer means 31, 32. It comprises two subassemblies, each subassembly comprising a finger 801 extending transversely, as shown in particular in FIG. figure 7 . The separation device 80 is movable in translation in a vertical direction, between a retracted position and a separation position, each finger 801 being movable transversely to move away from or close to each other synchronously.

The separation table 81 is mounted movable in translation in the direction of advance between a withdrawal position, as shown in FIG. figure 5 , and a supportive position, as shown on the figures 1 and 6 . In the retracted position, the separation table 81 is housed under the first transfer means 31, a front portion 810 of the table being set back from the nose 36 with respect to the forward direction F3. In the support position, the separation table 81 extends above the reception table 4 after sliding in the forward direction F3.

The separation means 8 also comprise a flexible blade 82 extending horizontally under the nose 36 and above the plane of the separation table 81 and protruding in the direction of advance.

The packet forming machine further comprises a stop 5 for stopping the bags 1 above the receiving table 4. The stop 5 has an abutment face 50 extending vertically facing the nose 36. It is adjustable in position to adjust the distance between the nose 36 and the stop face 50 depending on the length of the bags 1 to stack.

The package forming machine also comprises upper transport means 9 placed above the receiving table 4. They have a horizontal face oriented downwards and intended by its movement to accompany up to the stop 5 bags 1 arriving on the stack in the F3 direction. The upper transport means 9 comprise for example two belts 90 in a loop.

Operation of the first embodiment

The line of bags 1 from the manufacturing machine arrives in the direction of the arrow F1 so that the bags 1 are individually supported by the turning means 21, 22, between the conveyor belts. The bags 1 follow the turning course and arrive in the transfer zone, the first face 13 being oriented downwards.

The transfer means 31, 32 are driven at a much lower speed than the overturning transport means 21, 22. Typically, the linear speed ratio is 10 to 1. This ratio is provided either mechanically by coupling the means of rotation. respective drive, either by a differentiated control of electric motors.

A first bag 1a that arrives from the overturning transport means 21, 22 remains substantially at the same speed as its rear edge has not left the transfer zone. When the rear edge 12 is above the ramp 311, the blades 332 of the reel 33 push said edge 12 downwards, in a direction of folding perpendicular to the plane of the bags 1. The first bag 1 began to slow, from It is in contact with the first transfer means 31. A second bag 1b, following the first bag 1a, then covers the rear edge 12 of the first bag 1a by sliding into the curved portion of the blades 332. reel 33 retracts while continuing its rotation in the direction of the arrow F2. The brake 35, turning in the same direction, presses the first bag 1a to press against the first transfer means 31 near the rear edge 12 of said first bag 1a. It is then at the same speed as the first transfer means 31 while remaining tensioned during the braking operation. The second bag 1b can continue to advance rapidly, thereby covering the first bag 1a, as shown in FIG. figure 4 . The reel 33 and the brake 35 rotate bag by passage 1. Their drive means are thus specifically controlled, since this rhythm must be adapted to the length of the bags 1 and the interval between them.

The bags 1 in recovery are pressed against the first transfer means 31 by the roller 34, the first bag 1 passing under the roller 34 after being braked by the brake 35. They then arrive at the nose 36.

Referring to figures 5 and 7 , the bags 1 are stacked on the reception table 4, the fingers 801 of the separation device 80 being in position The bags 1 that arrive slide on the top of the stack of bags 1 which is formed. The stop 5 stops the bags 1 when they arrive against the abutment face 50, while the upper means of transport 9 accompany the bags 1 still overlapping towards the stop 5. During this accumulation phase, the receiving table 4 progressively descends in order to maintain the upper level of the bag stack 1 at a constant level, and thus to keep the bags 1 in contact with the upper means of transport 9.

When a packet P of a predetermined number of bags 1 is on the reception table 4, the separation device 80 is piloted in a separation direction F4 perpendicular to the plane of the bags 1 towards a separation position up to a first level so that the fingers 801 are introduced between a predecessor bag 1c and a follower bag 1 d, as shown in FIG. figure 8 . The predecessor bag 1 c and the follower bag 1 d continue their advance movement until the predecessor bag 1 c abuts.

Then the separating device 80 is moved to a second level by passing through the flexible blade 82 which retracts and then resumes its place by keeping the trailing edge 12d of the follower bag 1d, in order to separate the follower bag 1d and the bag predecessor 1 c at the rear edges 12c, 12d. The rear edges 12 of the bags 1 in the package P on the reception table 4 are a little compressed down. The separation table 81 is then introduced in the forward direction F3 into the open space between the predecessor bag 1c and the follower bag 1d, as shown in FIGS. figures 6 and 9 . The follower bag 1 d is then supported by the separation table 81. The fingers 801 of the separating device 80 are piloted so that they move apart in a transverse direction and disengage from the bags 1, as shown in FIG. figure 10 the separating device 80 is raised upwards to the retracted position and the fingers 801 are put back into the initial position, which constitutes, with the downward movement until second level, a square cycle movement. The position reached is shown on the figure 11 .

At the same time, the reception table 4 is lowered to transfer the packet P of bags 1 onto the transfer table 6 and the packet P of bags 1 is evacuated using the ejection grid 7, as shown in FIG. the figure 10 . When the ejection grille 7 has returned to position, the reception table 4 is raised and the separation table 81 is retracted to transfer the follower bag 1d to the reception table 4. A new package formation cycle is started again.

Second embodiment

The second embodiment of the invention, shown schematically on the figure 12 differs from the first embodiment in that the machine does not have a flexible blade. Preferably, the fingers 801 'of the separating device 80' extend over a greater length in the direction of advance.

In operation, after the device has reached the first level, the follower bag 1d and the predecessor bag 1c are moved apart by lowering the receiving table 4, the separating device 80 'supporting the rear edge 12d at least of the follower bag 1d. The separation table 81 is then introduced under the follower bag 1d. We find at this moment the same situation as in the first mode realization and one pursues in the same way.

Third embodiment

The third embodiment, shown schematically on the figure 13 , differs from the first embodiment in that the machine does not have a flexible blade or separation table. Furthermore, the fingers 801 "of the separating device 80" extend over a length substantially corresponding to the length of the bag.

In operation, after reaching the first level by the separation device 80 ", the fingers 801" support the follower bag 1d essentially over the entire length of the bag. We adjust the position of separation device 80 "continuously to maintain the upper level of the bag stack 1 on the follower bag 1d at a constant level.

It is then possible to lower the reception table 4 until transferring the packet of bags 1 onto the transfer table 6. Once the package P has been evacuated, the reception table 4 is raised under the follower bag 1d and the fingers 801 are retracted. "of the separation device 80" in order to transfer the follower bag 1d and the bags 1 above it on the reception table 4.

List of references

1. [ ¹ ] DE 20 2004 005723 U1: published on August 18, 2005
2. [ ² ] WO 91/08974 A1: published June 27, 1991

Claims (17)

1. A method for forming packs of flat bags (1) wherein a continuous line of bags (1) moving in an oriented direction of advance (F3) is received, the bags (1) are moved above a receiving table (4) on which the bags (1) are stacked while being stopped in the oriented direction of advance (F3) by an abutment (5), characterized in that the continuous line of bags (1) is converted into a line of overlapped bags (1) before stacking them, and in that the bags (1) are separated above the receiving table (4) by separating means (8) including a separating device (80), operation during which the separating device (80) is inserted by a movement in a separating direction (F4) perpendicular to the plane of the bags (1) between a preceding bag (1c) and a following bag (1d) in the overlapped line such that, when the following bag (1d) stops against the abutment (5), it is at least partially supported by the separating means (8).
2. The method according to claim 1, wherein the following bag (1d) is separated from the preceding bag (1c) at least at the level of the rear edges of the bags (1) and, the separating means (8) including a separating table (81), the separating table (81) is inserted in the oriented direction of advance (F3) between the preceding bag (1c) and the following bag (1d) to support the following bag (1d).
3. The method according to claim 2, wherein the separating device (80) is inserted up to a first level and until the preceding bag (1c) is in abutment, then the separating device (80) is moved to a second level maintaining the rear edge (12d) of the following bag (1d) by a flexible blade (82) protruding in the oriented direction of advance (F3) to separate the following bag (1d) and the preceding bag (1c) at rear edges (12c, 12d).
4. The method according to claim 2, wherein the following bag (1d) is separated from the preceding bag (1c) by lowering the receiving table (4), the separating device (80) supporting the rear edge (12d) of at least the following bag (1d).
5. The method according to one of claims 2 to 4, wherein, after the insertion of the separating table (81), the process continues by retracting the separating device (80).
6. The method according to claim 1, wherein the following bag (1d) is supported by the separating device (80") essentially over the complete length of the bag, and the receiving table (4) is lowered, the separating device (80") supporting the following bag (1d).
7. The method according to one of claims 1 to 6, wherein the position of the separating device (80) is continually adjusted to maintain the upper level of the stack of bags (1) on the following bag (1d) at a constant level.
8. The method according to claim 1, wherein the position of the receiving table (4) is continuously adjusted to maintain the upper level of the stack of bags at a constant level.
9. The method according to one of claims 1 to 8, wherein the upper level of the stack is maintained against upper transport means (9) placed above the receiving table (4) and accompanying the bags (1) arriving on the stack in the oriented direction of advance (F3) up to the abutment (5).
10. The method according to one of claims 1 to 9, wherein the receiving table (4) is lowered after the following bag (1d) is supported, the pack (P) of bags (1) supported by the receiving table (4) is evacuated, the receiving table (4) is moved up and the separating means (8) are retracted to transfer the following bag (1d) on the receiving table (4).
11. The method according to one of claims 1 to 10, wherein the separating device (80) is moved according to a square cycle in a plane perpendicular to the oriented direction of advance (F3), one of the movements of the square cycle being the insertion of the separating device (80).
12. The method according to one of claims 1 to 11, wherein the first transfer means (31) move at a speed lower than the arrival speed of the bags (1) at a distance from each other, a folding back member (33) upstream of the first transfer means (31) moves the rear edge (12) of a first bag (1a) in a folding back direction perpendicular to the plane of the bags (1) until a second bag (1b) which follows the first bag (1a) covers the rear edge (12) of the first bag (1a).
13. The method according to claim 12, wherein a brake (35) near to and downstream of the folding back member (33) press the first bag (1a) against the first transfer means (31) near the rear edge (12) of said first bag (1a).
14. The method according to claim 13, wherein the overlapped bags (1) are pressed against the first transfer means (31) by a roller (34), the bag passing under the roller (34) after having been braked by the brake (35).
15. The method according to claim 1, wherein each bag including a tab (10) not glued folded to be pressed down on a first face (13) of the bag, the bags (1) are placed so that they reach the first transfer means (31) the tab (10) at the front and the first face (13) oriented in the folding back direction.
16. A machine for forming packs of bags (1) receiving a continuous line of bags (1) moving in an oriented direction of advance (F3), a receiving table (4) on which the bags (1) are stacked being stopped by an abutment (5), the machine being characterized in that it includes braking means (3) to receive the continuous line of bags (1) and form a line of overlapped bags (1) on first transfer means (31), separating means (8) receiving the line of overlapped bags (1) from the first transfer means (31) and comprising a separating device (80) sliding with a movement perpendicular to the plane of the bags (1) between a retraction position and a separation position to be inserted between a preceding bag (1c) and a following bag (1d) in separation position such that, when the following bag (1d) stops against the abutment (5), it is supported by the separating means (8) and in that the machine carries out the method according to one of claims 1 to 15.
17. The machine according to claim 16, characterized in that it includes turn-over means (2) to carry out the method according to claim 15, the turn-over means (2) including a pair of turn-over transport means (21, 22) delimiting between them a trajectory describing approximately a U-turn.

Images