EP3795519A1 - Device for supplying a machine with continuous film - Google Patents

Abstract

Device for supplying a machine with continuous film 4, 4 ', comprising at least one unwinder from a reel 1, 1' of said film 4, 4 'and motorized drive means for the film 4, 4'. The motorized film drive means comprise at least one endless belt conveyor 2 comprising means for maintaining the film 4, 4 'in adhesion contact with the strip 2, said holding means applying only to the fraction. path of the strip 2 supporting the film 4, 4 '.

Description

The present invention relates to a device for supplying a machine with a fine material in a continuous strip, of film type for example but not exclusively of plastic, comprising at least one unwinder of a reel of said film and motorized drive means. to convey the latter to said machine. By way of example, the machines concerned can be thermoformers, traysealers, packaging machines, etc.

The invention therefore makes use of techniques in the field of conveying a material in a continuous strip for supplying a machine with a continuous material, the particularly mechanical properties of which are suitable for their subsequent processing in said machine. Thus, for example, in the case of a thermoformer or a traysealer, the film of the reel may be made of plastic material, such as polypropylene, polyethylene, polyvinyl chloride (PVC) or the like.

Very generally, the film is fed by unwinding a reel mounted on a feed device, which essentially comprises a shaft on which the reel, the central portion of which is hollow, is placed horizontally and rotates freely. . In order for the feeding to take place under satisfactory conditions, the tension of the strip resulting from the unwinding is an important parameter: the strip of film must be supplied with a constant tension to the input of said packaging machine.

On existing machines, unwinding is done with a drum motor which pulls the film from the reel and conveys it to the machine located downstream in the production line. To maintain the required tension, provision is made for the drum motor to be covered with a special coating, designed to allow the film to adhere correctly to the drum to allow the latter to drive it. The problem is that the quality of this adhesion itself depends on the input tension on said drum and that the working mode of this type of machine, involving cyclic operations, quite commonly results in releases of the upstream belt. , in particular due to the fact that the unwinder does not generally stop its rotation at the precise moment of stopping the motor driving the drum. In other words, the mechanical inertia of the unwinder leads in practically all cases to a time lag between the respective stops of the motorized drum and of the unwinder, resulting in the aforementioned loosening of the strip, which no longer presents a tension d. sufficient entry near the drum. Under these conditions, a slippage occurs each time the drive drum is restarted, which results in degrading, over time, the coating allowing the adhesion of the film, progressively amplifying the problem.

To respond to this drawback, it has been proposed to place a backing roller at the level of the drive drum, but this solution is not optimal in terms of safety, and it appreciably complicates the passage of the film. In addition, among the possible uses of these films and of the processing machines that they supply, there are many food applications. However, during filming operations in areas involving the food production chain, for reasons relating to hygiene, the films must not be driven from the side which will potentially be in contact with the food. The technically possible counter-roller solution is therefore unsuitable in practice in a number of applications.

Another solution proposed in the prior art consists in placing the drive drum directly in contact with the reel being unwound, in the immediate vicinity of the unwinder. From an industrial efficiency standpoint, however, such a configuration has the drawback of making it more difficult to load / change coils of raw material, whereas this is, as will be seen in more detail below, of an important stake in the operation of a continuous film supply chain such as in the invention. Moreover, due to the direct contact with the wound film, there is the drawback cited against the previous solution in the hypothesis of use in the food industry.

The object of the present invention is to overcome the drawbacks of the state of the art, in particular those which are mentioned previously in connection with particular solutions or applications, by proposing a device for supplying a machine with continuous plastic film having motorized film drive means which make it possible in particular to guarantee a permanent operating voltage, and can be implemented without contact with one of the sides of the film, making them compatible with film processing machines used in the film. food industry. It should also be noted that the solutions recommended by the invention do not in any way interfere with the operations of changing film reels, and appreciably improve the continuity of the processes when replacing an exhausted reel.

To these effects, the present invention, which relates very precisely to a device for supplying a machine with continuous film, firstly and conventionally comprises at least one unwinder of a reel of said film and motorized film drive means. . It is then such that the motorized film drive means comprise at least one endless belt conveyor supporting the film and comprising means for maintaining the film in adhesion contact with the strip, said holding means applying only to the portion of the path of the strip supporting the film, said strip having a width at least equal to that of the film and the holding means being applied over at least the width of the film.

The means for maintaining the film in contact with the strip are therefore only exerted on a portion of the path of the endless strip, that during which there is actually support of the film by the strip. This excludes the solutions, deemed unsatisfactory, of the prior art using an adherent coating, since they require that the entire strip be coated. This also rules out solutions of the type shown in the document. US2006 / 0130435 , which shows endless bands applied on top of a plastic film, which are not a drive means and do not support the film, but are only intended to prevent the side borders from falling down by gravity. On the contrary, the invention supports the entire width of the strip, which it keeps quite flat.

More precisely, the holding means may comprise, within the framework of the invention, means for generating a depression at the level of the path fraction of the strip supporting the film, acting in combination with the fact that the strip comprises perforations distributed over its surface. The efforts aimed at pressing the film against the strip are obtained, in the useful support zone for the film, by suction of the latter on the conveyor belt, suction which ceases as soon as contact with adhesion is no longer necessary, at the outlet of the film. belt conveyor. The precision of action of such a solution is much higher than what can be obtained by a adhesive coating, due to the delimitation of the zone of exercise of the plating of one (the film) on the other (the tape). Furthermore, no wear, mechanical or otherwise, is to be feared in this configuration.

More precisely still, the means for generating a vacuum can consist of at least one vacuum chamber. Each box used in the solutions constructed according to the present invention is placed in such a way that the depression is exerted at the level of one side of the box which covers, at least in width, the surface of the strip, and is located in the immediate vicinity. of the face of the strip which is not intended to come into contact with the film: the perforations then transmit the suction force to said film and help to press it into contact with the other face of the strip which carries it .

According to one possible configuration, the endless belt conveyor of the invention comprises two rotating drums around which the belt is wound, located at its two ends along an axis collinear with the driving direction of the film, at least one of said drums being driven by motor means, and at least one vacuum chamber being placed between said drums. These delimit in practice the portion of the path of the strip supporting the film. The support strip of the film being stretched between the two drums, it in fact has a portion of planar appearance of length substantially equal to the distance between the axes of the drums.

According to a possible variant, the supply device of the invention may comprise a belt conveyor with two juxtaposed vacuum chambers in the direction of driving the film, respectively an inlet box and an outlet box. The existence of these two juxtaposed boxes is particularly useful for managing the end of a roll and the arrival of the free end of a new roll of film, with a view to making their connection if possible in masked time, seen from the treatment process implemented by a machine downstream of the device supply of the invention. At the very least, the idea is to get closer to such a functioning in masked time.

To this end, and according to one possibility, the advantages of which will appear more particularly in the following, in order to detect the end of the roll of a film, the device of the invention may include a pressure detector at least in the inlet box. .

In this hypothesis, the measurement of the pressure variations in the input box makes it possible to detect whether there is still film which runs, or on the contrary if the reel is exhausted. Alternatively, if pressure sensors are placed in the two boxes, which is also possible, it is the pressure variation between the two boxes which is measured: when one of them is no longer covered by the film and that the other still is. We can then trigger the shutdown of the supply and change the feed film.

According to another possible variant, said device of the invention may comprise two belt conveyors aligned along the driving direction of the film, each comprising a single vacuum chamber, means for synchronizing the driving speed of the bands of the two. carriers then being provided. Preferably, the two conveyors are identical, which means that they each comprise two drums and an endless belt.

The synchronization means can be mechanical, or alternatively be electronic, and then synchronize the speed of electric motors driving a drum of each conveyor.

Motorized means conventionally consist of asynchronous motors operating with variable speed drives, or of brushless self-piloted synchronous motors, known as “brushless” motors. A film cutting device can optionally be placed between the two aligned conveyors, providing an additional function possibly required by the processing implemented downstream in the production line.

Furthermore, according to a possibility specific to the invention, the motorized film drive means, in this case the endless belt conveyor (s), are associated with a film reserve loop placed at the outlet of said means, and consisting of at least one axis roller offset from the film drive plane on the belt conveyor (s). More precisely, this reserve loop may include a plurality of idle rollers, the axes of which are staggered. This additional function is in particular provided to facilitate the realization in masked time of the operation of joining films coming from two separate rolls. The rollers of the reserve loop can moreover be arranged and / or designed to have an effect on the tension of the film leaving the drive means, as will be seen below.

• suite à la détection d'une différence de niveau de vide dans les caissons à dépression, arrêt du transporteur à bande de sorte que l'extrémité finale du film puisse être positionnée à la jonction entre les deux caissons ;
• changement de film et positionnement de l'extrémité libre du nouveau film au niveau de ladite jonction ;
• collage des deux extrémités de film l'une à l'autre ;
• redémarrage du convoyeur à bande.

The present invention secondarily relates to a method of continuously supplying a machine with film by means of a supply device as explained previously, characterized by the following steps:

• following the detection of a difference in vacuum level in the vacuum chambers, stopping the conveyor belt so that the final end of the film can be positioned at the junction between the two chambers;
• changing the film and positioning the free end of the new film at said junction;
• gluing of the two film ends to each other;
• restarting the conveyor belt.

Finally, the invention also relates to a packaging line comprising a machine, such as a graphic arts machine, packaging machine, a thermoformer or a traysealer, fed with a strip by a supply device as developed. above, and in particular allowing the implementation of a process for continuously feeding such a machine, within the framework of such a line, by connecting films from separate spools.

Other objects and advantages of the present invention will become apparent during the description which follows relating to embodiments which are given only by way of indicative and non-limiting examples.

• [Fig.1] montre schématiquement un transporteur à deux caissons à dépression ;
• [Fig.2] est une représentation schématique d'une version à deux transporteurs à bande d'un dispositif d'approvisionnement en film à deux bobines selon l'invention ;
• [Fig.3] illustre l'état du dispositif lorsqu'on arrive en fin d'une bobine de film en cours d'alimentation du dispositif de l'invention ; et
• [Fig.4] représente schématiquement le traitement opéré pour raccorder le film d'une autre bobine à l'extrémité finale du film issu de la bobine d'alimentation en cours.

The understanding of this description will be facilitated in particular by referring to the accompanying drawings and in which:

• [ Fig. 1 ] schematically shows a conveyor with two vacuum chambers;
• [ Fig. 2 ] is a schematic representation of a two belt conveyor version of a two reel film supply device according to the invention;
• [ Fig. 3 ] illustrates the state of the device when reaching the end of a film reel being fed to the device of the invention; and
• [ Fig. 4 ] schematically represents the processing carried out to connect the film of another reel to the final end of the film coming from the current supply reel.

With reference to the various figures, the supply device of the invention, which is designed to supplying film to a processing machine, for example a thermoforming machine, mainly consists of a reel 1, 1 'of raw material, that is to say in this case of film of plastic material, and means motorized drives, in this case an endless belt conveyor 2. Preferably, but not restrictively, the invention will find its application in the supply of packaging machines on a packaging line. However, the present invention will also find its application in the field of supplying graphic arts machines, for example in the field of printing or the like (see below).

The drive module is more particularly shown in figure 1 and comprises two vacuum boxes 5 and 6, box 6 being the input box, in the direction of travel of the film, while box 5 is the output box. As can be seen in this figure, the two boxes 5, 6 are juxtaposed, at the same level, and their "active" sides, that is to say capable of generating the depression which can attract the film and press it against the strip 2, are practically in contact with the inner face of the strip 2. The perforations in the strip 2, regularly distributed over the entire surface of said strip 2, make it possible to transmit the force of attraction on the outer face of the strip 2, that on which the film 4 (see the following figures) is transported, without compromising the support capacities of said strip 2. One of the two drums 7, 8 is motorized, for example by means of an asynchronous motor or alternatively to the by means of a self-piloted brushless synchronous motor, easy to control electronically. In the hypothesis of the invention, it is the drum 7 which is for example a motor and serves as a drive drum for the strip 2 according to the speed impelled by the motor which drives it, while the drum 8 serves as a drive drum. return roller for the endless belt. In this case, the endless belt 2 turns in the direction of the arrow F, which also shows the direction of travel of film 4, 4 'on tape 2.

The following figures 2 to 4 show in a more precise and complete manner the film supply device of the invention, based on the drive module described above. So the figure 2 shows that the supports of the main 1 and secondary 1 'reel comprise shafts 3, 3' fixed to a frame 100 so that a strip 4, 4 'can freely unwind from each of the reels 1, 1' towards the means motorized drives described above, capable of tensioning said strip 4, 4 'under the conditions mentioned at the start of the description. In the figure 2 , in particular, the film 4 'feeding the belt conveyor 2 comes from the secondary reel 1' and passes through an intermediate roller 10 free to rotate.

Although the supply device according to the invention can be used in a production line for any type of packaging, a preferred destination is in the food sector. In this case, the reel 1, 1 'consists of a film 4, 4', for example of polypropylene, or of polyethylene, or of polyvinyl chloride or the like. The packaging machine, not shown, can then, as mentioned, be a thermoforming machine or the like.

It should be noted as mentioned that the invention can also be used in rather distant fields, such as printing or the field of textiles and in this case, the coil 1, 1 'is rather made up of a winding of a technical equivalent of "film" - in the sense of a strip of negligible thickness compared to its other dimensions - of paper or fabric. The supply device then operates substantially in the same way.

The device of the invention is shown with, at the output, a reserve loop 9 of film 4, which allows the film processing machine 4 located downstream to continue to operate although there is a supply disruption to the device of the invention, for example if one of the reels 1, 1 'is finished, when the film 4, 4 'they store is exhausted. The lower roller 90 of this reserve loop can moreover be used to give the film 4, 4 'a tension at the output of the belt conveyor device 2. The vacuum chambers 5, 6 are shown with different dimensions, the one (box 5) being larger than the other (box 6): the reason for this difference, which is linked to the tension of the film 4, 4 ', will be explained below.

When the film 4 'of one of the reels 1, 1' is used up, for example that of the reel 1 'as on the figures 3 and 4 , the assembly is fed with film 4 coming from the other reel, in this case the main reel 1. When a significant variation in the vacuum levels in the vacuum chambers 5, 6 is detected, by comparison of the values from the vacuum sensors placed in these boxes, in a variant with two sensors, or when the vacuum level of the inlet box 6 varies significantly, in a variant with a single sensor, indicating the absence of film, the drum motor 7 is stopped, stopping the motor which controls it. The final free end of the film is then positioned at the edge of the outlet vacuum box 5 adjoining the inlet box 6. If said motor is a self-piloted brushless synchronous motor, this positioning is carried out automatically, due to the precision of the motor control. In the case of an asynchronous motor, it is up to the operator to carry out the positioning. This is what appears in figure 3 .

The vacuum chambers 5, 6 remain in operation and active even in the event of the end of the film 4, 4 'from the reels 1, 1', and the final end of the reel 1 is therefore maintained - without necessarily stopping the downstream processing machine by varying the length of strip allowed by the reserve loop 9 - on the conveyor belt 2, at the level of the vacuum chamber 5. At the same time, the initial free end of the new film 4 from the main reel 1 is placed to in turn feed the belt 2 of the conveyor of the drive module. The free end of the new film 4 is positioned on the endless belt 2 above the inlet box 6, with the end edge placed in line with said edge separating the two boxes 5, 6. It remains there. also due to the attraction exerted by said box 6, still in action. Then the two free ends are connected and glued to each other using an adhesive strip 40 placed transversely, that is to say arranged perpendicular to the axis of movement marked by the arrow F of the figure 1 , as shown in figure 4 . The drive means, in this case the conveyor belt 2, are then restarted by restarting the motor controlling the drum motor 7, the continuity of the downstream treatment process being able, as said, to be preserved if the reserve loop 9 is sufficient. .

In this case, the downstream thermoformer continues to operate normally by being supplied with film 4, 4 'which it "draws" from the reserve loop 9. In the event of a higher film, for example printable, for the same thermoformer, the same protocol is reproduced in a device whose casing 100 is a little different, with a more vertical structure. To ensure that the positioning of the two ends of the films 4, 4 'can be done correctly, it may be necessary to cut the final end of the film 4, 4' placed on the vacuum chamber 5.

In terms of sizing, it should be noted that the input tension in the machine can be of the order of 5 kg (see in figure 4 ), in certain applications, in particular using a downstream thermoforming machine. The film retaining zone 4, 4 'delimited by the vacuum chamber 5 must therefore be compatible with this value. Conversely, the box 6 must maintain a film which is not subjected to any tension. This may explain their difference in sizing.

But this is not the only possible configuration, the output voltage must in reality be adjustable, and can also be low, in other applications, for example upstream of bagging machines with elastic film. In fact, and more generally, one can easily modulate, within the framework of the invention, the differential between the input and output voltages, so as to adapt as finely as possible to the use which is made of the device. of the invention. The adjustment of the dissociation of said voltages is in practice an important characteristic of the invention, and must be able to cover a wide spectrum, possibly going up to an input voltage which can be zero and a low output voltage, or conversely include two rather high voltages. It is usage in the downstream process that dictates the settings made.

The supply device of the invention, in addition to its character adapted to the hygienic requirements of certain industries, is also moreover particularly adapted to industrial constraints since it appreciably improves the management of film reel changes. The suction zones used to manage the tension of the film being fed finally constitute a very flexible means of combining the tension requirement and the junction requirements between reels without disturbing the operation of the production line.

Claims (14)

Device for supplying a machine with continuous film 4, 4 ', comprising at least one unwinder of a reel 1, 1' of said film 4, 4 'and motorized drive means for the film 4, 4', characterized in that the motorized film drive means comprise at least one endless belt conveyor 2 supporting the film 4, 4 'and comprising means for maintaining the film 4, 4' in adhesion contact with the belt 2, said holding means applying only to the portion of the path of the strip 2 supporting the film 4, 4 ', said strip 2 being of a width at least equal to that of the film 4, 4' and the holding means applying over at least the width of the film 4, 4 '. Device for supplying a machine with film 4, 4 'according to the preceding claim, characterized in that the holding means comprise means 5, 6 for generating a vacuum at the level of the path fraction of the strip 2 supporting the film 4, 4 ', and in that the strip 2 has perforations distributed over its surface. Device for supplying a machine with film 4, 4 'according to the preceding claim, characterized in that the means for generating a vacuum consist of at least one vacuum chamber 5, 6. Device for supplying a machine with film 4, 4 'according to the preceding claim, characterized in that the belt conveyor 2; 2 'endless comprises two rotary drums 7, 8 around which the strip 2 is wound, located at its two ends along an axis defined by the direction of drive of the film 4, 4', at least one of said drums 7, 8 being trained by motor means, at least one vacuum chamber 5, 6 being placed between said drums 7, 8. Device for supplying a machine with film 4, 4 'according to the preceding claim, characterized in that it comprises a belt conveyor 2 with two vacuum chambers 5, 6 juxtaposed in the driving direction F of the film 4, 4 ', respectively an input box 6 and an output box 5. Device for supplying a machine with film 4, 4 'according to the preceding claim, characterized in that it comprises a pressure detector at least in the inlet box 6. Device for supplying a machine with film 4, 4 'according to Claim 4, characterized in that it comprises two belt conveyors 2 aligned in the direction of drive F of the film 4, 4', each comprising a single box 5; 6 with vacuum, means for synchronizing the driving speed of the bands 2 of the two conveyors being provided. Device for supplying a machine with film 4, 4 'according to the preceding claim, characterized in that the synchronization means are mechanical. Device for supplying a machine with film 4, 4 'according to the preceding claim, characterized in that the synchronization means are electronic, and synchronize the speed of electric motors driving a drum 7, 8 of each conveyor. Device for supplying a machine with film 4, 4 'according to one of Claims 7 to 9, characterized in that a device for cutting the film 4, 4' is placed between the two aligned conveyor belts 2. Device for supplying a machine with film 4, 4 'according to one of the preceding claims, characterized in that the motorized drive means of the film 4, 4' are associated with a reserve loop 9 of film 4, 4 'placed at the outlet of said means, and consisting of at least one roller with an axis offset with respect to the film drive plane 4, 4' on the conveyor (s) to belt 2. Device for supplying a machine with film 4, 4 'according to the preceding claim, characterized in that the reserve loop 9 comprises a plurality of idle rollers, the axes of which are staggered. Method of continuously supplying a machine with film 4, 4 'by means of a supply device according to the preceding claims, characterized by the following steps: - following the detection of a difference in vacuum level in the vacuum chambers 5, 6, stopping of the conveyor belt 2 so that the final end of the film 4 'can be positioned at the junction between the two chambers 5 , 6; - change of film 4 and positioning of the free end of the new film 4 at said junction; - Bonding of the two ends of film 4, 4 'to one another; - restart of the belt conveyor 2. A packaging line comprising a machine, such as a graphic arts machine, packaging machine, a thermoformer or a traysealer, supplied with film 4, 4 'by a supply device according to any one of claims 1 to 12.

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