Method and machine for forming bag packs

According to a method for forming packs of flat bags, a continuous line of bags moving in an oriented direction of advance is received. The bags are moved onto a receiving table on which the bags are stacked while being stopped from moving in the oriented direction of advance by an abutment. The continuous line of bags is converted into a line of overlapped bags before stacking the latter, and the bags are separated on the receiving table by separating means comprising a separating device. During this operation, a separating device is inserted by a movement in the separating direction perpendicular to the plane of the bags between a preceding bag and a following bag in the overlapped line in such a way that, when the following bag stops against the abutment, it is supported at least partially by the separating means.

This application claims priority to International Application No. PCT/FR2013/050962 filed May 2, 2013 and French Patent Appln. No. 1254075 filed May 3, 2012; the entire contents of each are incorporated herein by reference.

BACKGROUND

The invention relates to a method for forming packs of flat bags, in particular flexible and long bags, continuously leaving a production line of the said bags. It concerns a machine carrying out such a method.

SUMMARY

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

These bags are produced on a production line which starts with a rolled sheet, then forms a bead which is flattened, cut and closed at one end by a glued flap. In certain cases, a flap is also formed at the end opposite to the one which is closed. The bag leaves this line flat on a conveyor belt, the flap being located towards the front and protruding from the conveyor belt as shown onFIG. 3.

In certain configurations, the bag is driven vertically to a receiving table on which a stack of bags forms. The stack pushes on a square which maintains an end of the stack. Document DE 20 2004 005723 U1 shows such a configuration. Such an arrangement gives satisfaction when the speed at which the bags arrive is not too high and when the bags have a good intrinsic strength which comes from the basis weight of the film and the dimensional ratios. This is not the case for bags with a long shape. These bags have a strength which is not sufficient to stay upright against the square.

A stack forming machine comprising a conveyor extending horizontally above a receiving table is also known. The conveyor grips a front edge of a bag which arrives by pinching it and brings it above the receiving table to release it when the bag is completely above the receiving table. The bag is then stopped by an abutment in the movement axis of the bags. Such a machine is limited in speed by the fact that, above a certain speed, the bags distort and are damaged when they arrive against the abutment.

Document WO 91/08974 A1 shows a cardboard sheet cutting and stacking machine. After cutting, the sheets are accelerated to move on the table in a separate manner. Overlapping forming means allow the sheets to be slowed down and arranged in an overlapped manner. All of the sheets then move at reduced speed. The sheets are then transported by transport means to a receiving table. The sheets arrive in abutment against a cleat and are stacked on the receiving table.

When the stack is complete, the machine must be stopped to remove the stack of sheets or to evacuate the receiving table with the stack and replace the table with a new table. Such an installation is not appropriate for the production of bags due to the fact that certain bags produced in the transitory stop and restart phases which are imposed for the evacuation of the stack may not be in compliance with the quality requirements and must be downgraded.

The aim of the invention is to provide a method and a machine to form packs of bags, in particular long bags, at high rate and without interruption in the production of the bags during the evacuation of the packs.

With these targets in mind, the object of the invention is a method for forming packs of flat bags wherein a continuous line of bags moving in an oriented direction of advance is received, the bags are moved onto a receiving table on which the bags are stacked being stopped from moving in the oriented direction of advance by an abutment, characterised in that the continuous line of bags is transformed into a line of overlapped bags before stacking the latter, and the bags are separated on the receiving table by separating means comprising a separating device. During this operation, the separating device is inserted, by a movement in a separating direction perpendicular to the plane of the bags, between a preceding bag and a following bag in the overlapped line such that, when the following bag is stopped against the abutment, it is at least partially supported by the separating means.

Means are thus provided to retain on the receiving table the bags which continue to be produced while the bags stacked up to the preceding bag are evacuated. The overlapping of the bags allows a high reduction in the movement speed of the bags to be obtained. The separating device, by being inserted via the top of the line of bags, can be put into place very rapidly, without risking collision with a moving bag, the speed of which has already been reduced. The bags which continue to be produced are stored above the following bag which is retained and there is no need to interrupt their production. This allows permanent conditions to be guaranteed for the production of the bags and allows the dispersion of the characteristic properties of the bags to be limited. The separating device can be operated automatically, for example, after the passage of a predetermined number of bags since the start of the production or the previous bag evacuation operation. The packs thus formed are formatted in a reproducible and parameterisable manner. Also, as the movement speed of the bags has been reduced by the overlapping, it no longer comprises a limit for the bag production rate. High rates can therefore be reached whilst forming packs simple to handle.

In a particular manner, the following bag and the preceding bag are separated at least at the rear edges of the bags and, the separating means comprising a separating table, the separating table is inserted in the oriented direction of advance between the preceding bag and the following bag to support the following bag. The separating table supports the following bag and those which are stacked above in a very dependable manner. The insertion of the separating table can be done even if the following bag still partially bears against the preceding bag. The installation is easily adapted to bags of different lengths by simply modifying the travel of the separating table.

According to a first embodiment, the separating device is inserted up to a first level and until the preceding bag is in abutment, then the separating device is moved up to a second level maintaining the rear edge of the following bag by a flexible blade protruding in the oriented direction of advance to separate the following bag and the preceding bag at the rear edges. At the first level, the separating device maintains the conditions allowing the preceding bag to reach the abutment, therefore avoiding the exertion of a pressure on the said bag. The combination of the flexible blade and of the separating device then allows the separation of the bags to be obtained, at least at the rear edge, when the device forces the rear edges of the bags under the preceding bag to pass over the flexible blade, whereas the following bag is retained after passing the separating device. A space is thus created in which the separating table can be inserted. The first and second levels can represent a position or a force. The force has the advantage of being able to follow the continuous stacking of the bags. The position has the advantage of being simpler to control.

According to a second embodiment, also using the separating table, the following bag is separated from the preceding bag by lowering the receiving table, the separating device supporting the rear edge of at least the following bag. In this configuration, the space is created by lowering the receiving table which supports the bag pack surmounted by the preceding bag. The separating table can then be inserted to support the bags over their complete length.

According to an additional step, after the insertion of the separating table, the separating device is then retracted. The following bag and the bags which follow are thus accommodated by the separating table whilst the separating device can return to its place, waiting to separate the next pack. The retraction is for example a movement perpendicular to the oriented direction of advance and to the separating movement. The separating device is thus freed so that it can return to a position in which the device is ready to restart a cycle.

According to a third embodiment, the following bag is supported by the separating device essentially along the complete length of the bag and the receiving table is lowered, the separating device supporting the following bag. In this case, there is no separating table, the support of the bags being ensured only by the separating device. The advantage of this embodiment is that it requires fewer components; however the separating device must be calibrated to receive and support the following bag over the major part of its length. It must be possible to adapt the following bag support parts 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 continuous separating device is adjusted to maintain the upper level of the stack of bags on the following bag at a constant level. Thus the same bag receiving conditions are maintained as and when the bag pack is made up, when it is supported by the separating device.

Also, the position of the receiving table is continuously adjusted to maintain the upper level of the stack of bags at a constant level. This applies when the receiving table supports a bag pack onto which new bags are stacked.

According to an improvement, the upper level of the stack is maintained against upper transport means placed above the receiving table and accommodating the bags arriving on the stack in the oriented direction of advance up to the abutment. The upper transport means help the bags in the upper part of the stack to reach the abutment, particularly when the upper level of the stack is maintained constant by the movement of the receiving table which also maintains a light pressure between the stack and the upper transport means.

In a complementary step, after the following bag is supported, the receiving table is moved down, the bag pack supported by the receiving table is evacuated, the receiving table is moved up and the separating means are retracted to transfer the following bag to the receiving table. Thus a return is made to a position similar to the one at the start of the cycle. The formed pack can then be dealt with in various ways, by being taken manually to be packaged, by being strapped in a manual or automatic manner, or being palletized in an automated manner.

In a particular manner, the separating device is moved according to a square cycle in a plane perpendicular to the oriented direction of advance, one of the movements of the square cycle being the insertion of the separating device. Such a movement can easily be implemented by the association of two translation guide systems. The square cycle must be understood as a succession of translation steps and not as the trajectory really described by the separating device. The trajectory is more or less rectangular but 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 each other, a press down member upstream of the first transfer means moves the rear edge of a first bag in a press down direction perpendicular to the plane of the bags until a second bag which follows the first bag overlaps onto the rear edge of the first bag. By thus making a stack of overlapped bags, the speed of the said bags is reduced to a great extent, so that they can be handled later more easily. The use of a press down member is one of the possible means to obtain this overlapping.

According to an improvement, a brake near to and downstream of the press down member places the first bag against the first transfer means near to the rear edge of the said first bag. By slowing down the bag upstream, the bag is not submitted to axial compression which could cause the bag to buckle.

According to an additional improvement, the overlapped bags are placed against the first transfer means by a roller, the bag passing under the roller after it has been braked by the brake. Thus it is ensured that the overlapped bags are driven by the first transfer means.

In the case where each bag includes a folded unstuck flap to be pressed down onto the first face of the bag, the bags are placed so that they reach the first transfer means with the flap forwards and the first face oriented in the press down direction. The flap is thus maintained against the preceding bag and there is no risk of it being caught on another bag, even by sliding on the previous bag during the stacking.

The object of the invention is also a machine for forming packs of bags receiving a continuous line of bags moving in an oriented direction of advance, a receiving table on which the bags are stacked being stopped by an abutment, the machine being characterised in that it includes braking means to receive the continuous line of bags and form a line of overlapped bags on the first transfer means, the separating means receiving the line of overlapped bags from the first transfer means and comprising a separating device sliding according to a movement perpendicular to the bag plane between a retracted position and a separation position to be inserted between a preceding bag and a following bag in separation position in such a way that, when the following bag stops against the abutment, it is supported by the separating means and in that the machine uses the method as described above.

In a particular configuration, the machine comprises means for turning over bags with flaps, the turnover means including a pair of turnover transport means delimiting between them a trajectory describing approximately a U-turn. Certain bag production machines supply a line of bags where the first face, onto which the flaps are intended to be pressed down, is oriented upwards. They must then be turned over so that the first face will be placed opposite the first transfer means.

DETAILED DESCRIPTION

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

A machine for forming packs of bags, in compliance with a first embodiment of the invention and shown onFIGS. 1 and 2, is intended to receive bags1from a bag production machine, not shown, at output of which the bags1are delivered one by one, flat in a continuous line, the bags1being separated from each other by a small interval d, as shown onFIG. 3. The continuous line arrives at the pack forming machine along a path symbolized by arrow F1onFIG. 1. The bags1comprise, for example, a flap10along a front edge11which arrives first in the feed direction of the line of bags1. The flap10is pressed onto a first face13of the bag without being glued, the flap being oriented upwards on leaving the production machine. The pack forming machine comprises turnover means2to place the bags1with the first face13oriented downwards, braking means3to receive the continuous line of turned over bags1and to form a line of overlapped bags1moving in an oriented direction of advance F3on the first transfer means31, and a receiving table4on which the overlapped bags1from the first transfer means31are stacked being stopped by an abutment5.

The turnover means2comprise a pair of turnover transport means21,22delimiting between them a turnover trajectory describing approximately a U-turn. This turnover trajectory extends from one end of the pack forming machine to the other passing via the lower part of the machine then pressing against a wheel23which makes the U-turn, represented on the LH part ofFIG. 1, to finish in an advance direction substantially horizontal, from the left to the right onFIG. 1. The turnover transport means21,22comprise in a conventional manner one or more conveyor belts parallel to each other, in loop form, guided by rollers rotationally mounted some of which ensure the drive, in a manner not detailed here. For description simplification reasons only, it is considered that each element of the pair of transport means comprises only one conveyor belt. The belts of the first and second turnover transport means21,22of the pair are opposite each other on the turnover trajectory of the bags1, in order to grip them, then respectively follow a first and a second return trajectory211,221.

Referring toFIG. 2, the first turnover transport means21comprise a first roller212which guides the first conveyor belt and orientates it towards the first return path211. The first roller212is placed to the substantially tangent to a horizontal plane tangent to the wheel23, the first return trajectory211being oriented at this level downwards. Moreover, the second turnover transport means22comprise a second roller222which guides the second conveyor belt and orientates it towards the second return trajectory221. The second roller222is placed in a manner substantially tangent to the horizontal plane tangent to the wheel23, the second return trajectory221being oriented at this level upwards. The second roller222is nearer to the wheel23than the first roller212to leave free a transfer zone Z above the first conveyor belt.

The braking means3comprise the first transfer means31, the second transfer means32, a press down member33and a stop roller34. The first transfer means31comprise a conveyor belt a part of which extends presenting a face310oriented upwards in the continuity plane of the turnover transport means2. The conveyor belt also has a ramp311, rising in the oriented direction of advance F3, just after the first roller212. The press down member33is placed opposite this ramp311. The press down member33comprises a shaft331rotationally mounted along a transversal axis in the direction shown by arrow F2, that is in a direction accompanying the movement of the bags1in the oriented direction of advance F3. The shaft of the press down member33also comprises blades332curved upstream, that is in the direction opposite to arrow F2. The trajectory of the blades332extends in the zone included between the ramp311and the trajectory of the bags1in the oriented direction of advance F3.

The second transfer means32have a part which extends above the transfer zone Z and in the direction of advance above the first transfer means31. They comprise several conveyor belts leaving passages between them for the blades332of the press down member33. The brake35is located in the vicinity and downstream of the press down member33, opposite the end of the ramp311. It also comprises a rotationally mounted shaft351and a cam352protruding from the shaft. The brake35and the press down member33comprise drive means, not shown, which drive it in a synchronous manner.

The roller34is freely rotationally mounted around an axle also transversal. Its support340is movably mounted in translation to be placed at an adjustable distance in relation to the press down member33. The roller34remains in contact in the direction of the first transfer means31.

The first and second transfer means31,32separate at the level of a nose36above the receiving table4. The receiving table4can be flat but, here, it comprises a set of bars40placed parallel to each other in a plane substantially horizontal and in a transverse direction. The receiving table4is vertically slidingly mounted. The machine also comprises a transfer table6, parallel to the receiving table4, to receive the formed packs and supported by the receiving table4. The transfer table6comprises slots in which the bars are housed when the receiving table4is in its lowest position. The machine also comprises a mobile ejection grid7in a transverse direction to make the formed and deposited pack slide on the transfer table6to a transverse position where it can be picked up, manually or by means not detailed here.

The machine also comprises separating means8including a separating device80and a separating table81. The separating device80is placed just downstream and above the nose36, at the outlet of the transfer means31,32. It comprises two subassemblies, each subassembly comprising a finger801extending transversally, as shown in particular onFIG. 7. The separating device80is translationally mobile in a vertical direction, between a retraction position and a separation position, each finger801being transversally mobile to move away from or towards each other in a synchronous manner.

The separating table81is mounted translationally mobile in the advance direction between a retraction position, as shown onFIG. 5, and a support position, as shown onFIGS. 1 and 6. In retraction position, the separating table81is housed under the first transfer means31, a front part810of the table being set back from the nose36in relation to the oriented direction of advance F3. In support position, the separating table81extends above the receiving table4, after sliding in the oriented direction of advance F3.

The separating means8also comprise a flexible blade82extending horizontally under the nose36and above the plane of the separating table81and protruding in the advance direction.

The pack forming machine also comprises an abutment5to stop the bags1above the receiving table4. The abutment5has an abutment face50extending vertically with regard to the nose36. Its position is adjustable to adjust the distance between the nose36and the abutment face50according to the length of the bags1to be stacked.

The pack forming machine also comprises upper transport means9placed above the receiving table4. They have a horizontal face oriented downwards and intended by its movement to accompany up to the abutment5the bags1arriving on the stack in the oriented direction of advance F3. The upper transport means9comprise for example two looped belts90.

The line of bags1from the production machine arrive in the direction of arrow F1in such a way that the bags1are handled individually by the turnover transport means21,22, between the conveyor belts. The bags1follow the turnover trajectory and arrive in the transfer zone, the first face13being oriented downwards.

The transfer means31,32are driven at a speed much lower than the turnover transport means21,22. Typically, the linear speed ratio is 10 to 1. This ratio is ensured either mechanically by coupling the respective drive means, or by a differentiated control of electric motors.

A first bag1awhich arrives from the turnover transport means21,22remains substantially at the same speed whilst its rear edge has not left the transfer zone. When the rear edge12is above the ramp311, the blades332of the press down member33push the said edge12downwards, in a press down direction perpendicular to the plane of the bags1. The first bag1abegins to slow down, due to the fact that it is in contact with the first transfer means31. A second bag1b, following the first bag1a, then covers the rear edge12of the first bag1aby sliding into the curved part of the blades332. The press down member33retracts continuing its rotation in the direction of arrow F2. The brake35, by turning in the same direction, presses on the first bag1ato place it against the first transfer means31in the vicinity of the rear edge12of the said first bag1a. It is then at the same speed as the first transfer means31remaining tensioned during the braking operation. The second bag1bcan continue to advance rapidly thus overlapping onto the first bag1a, as shown onFIG. 4. The press down member33and the brake35make a rotation by passage of bag1. Their drive means are thus controlled specifically as this rhythm must be adapted to the length of the bags1at the interval separating them.

The overlapped bags1are placed against the first transfer means31by the roller34, the first bag1apassing under the roller34after having been braked by the brake35. They then arrive at the nose36.

In reference toFIGS. 5 and 7, the bags1are stacked on the receiving table4, the fingers801of the separating device80being in retraction position, above the bags1. The bags1, which arrive, slide onto the top of the stack of bags1which forms. The abutment5stops the bags1when they come into contact with the abutment face50, whilst the upper transport means9accompany the bags1still overlapped towards the abutment5. During this accumulation phase, the receiving table4descends gradually to maintain the upper level of the stack of bags1at a constant level and thus maintain the overlapped bags1in contact with the upper transport means9.

When a pack P with a predetermined number of bags1is on the receiving table4, the separating device80is driven in a separating direction F4perpendicular to the plane of the bags1towards a separating position up to a first level so that the fingers801are inserted between a preceding bag1cand a following bag1das shown onFIG. 8. The preceding bag1cand the following bag1dcontinue their advance movement until the preceding bag1cis in abutment.

Then, the separating device80is moved to a second level passing the flexible blade82which retracts then returns to its position maintaining the rear edge12dof the following bag1d, to separate the following bag1dand the preceding bag1cat the rear edges12c,12d. The rear edges12of the bags1in the pack P on the receiving table4are slightly compressed downwards. The separating table81is then inserted in the oriented direction of advance F3into the open space between the preceding bag1cand the following bag d as shown onFIGS. 6 and 9. The following bag1dis then supported by the separating table81. The fingers801of the separating device80are driven so that they move away in a transverse direction and disengage from the bags1, as shown onFIG. 10, the separating device80is moved upwards up to the retraction position and the fingers801return to the initial position, which comprises, with the downward movement to the second level, a square cycle movement. The position reached is shown onFIG. 11.

At the same time, the receiving table4is moved downwards to transfer the pack P of bags1to the transfer table6and the pack P of bags1is evacuated by means of the ejection grid7, as shown onFIG. 10. When the ejection grid7returns to its place, the receiving table4is moved upwards and the separating table81is retracted to transfer the following bag1dto the receiving table4. A new pack forming cycle starts.

The second embodiment of the invention, shown schematically onFIG. 12, is different from the first embodiment by the fact that the machine does not include flexible blades. Preferentially, the fingers801′ of the separating device80′ extend over a longer length in the advance direction.

In operation, after the device has reached the first level, the following bag1dis moved away from the preceding bag1cby lowering the receiving table4, the separating device80′ supporting the rear edge12dat least of the following bag1d. The separating table81is then inserted under the following bag1d. At this time, the situation is the same as in the first embodiment and the operation continues in the same manner.

The third embodiment, shown schematically onFIG. 13, is different from the first embodiment by the fact that the machine includes no flexible blades or separating table. Moreover, the fingers801″ of the separating device80″ extend over a length corresponding practically to the length of the bag.

In operation, after the first level has been reached by the separating device80″, the fingers801″ support the following bag1dessentially over the complete length of the bag. The position of the separating device80″ is continually adjusted to maintain the upper level of the stack of bags1on the following bag1dat a constant level.

The receiving table4can then be lowered to transfer the pack of bags1onto the transfer table6. Once the pack P has been evacuated, the receiving table4is moved upwards under the following bag1dthen the fingers801″ of the separating device80″ are retracted to transfer the following bag1dand the bags1above the latter onto the receiving table4.