Thermoforming packaging machine and method for fine positioning of a film transport chain

Abstract

The invention relates to a thermoforming packaging machine (1) comprising at least one transport chain (9) which grasps a bottom film (8) and transports it in a transport direction (R) for each main work cycle, and at least one drive unit (18) for driving the transport chain (9) in the transport direction (R), wherein, for fine positioning of the transport chain (9) in an area of ​​at least one work station of the thermoforming packaging machine (1), a pairing of several chain links (16) of the transport chain (9) driven in the transport direction (R) by means of the drive unit (18) with a separately driven toothing (17, 17') can be produced.

Description

The present invention relates to a thermoforming packaging machine for the fine positioning of a film transport chain according to claim 1. Furthermore, the present invention relates to a corresponding method according to claim 12. On thermoforming packaging machines, film transport chains used to transport a bottom film fed in as a web have limited positioning accuracy. Experience has shown that this is influenced by several factors, such as wear on the transport chains caused by abrasion on the rollers, chain elongation, which is particularly associated with fluctuating, i.e., intermittent, tensile loads, manufacturing-related dimensional deviations of the chain links, uneven wear of the lateral transport chains used on both sides, film tension acting on the transport chains via the bottom film clamped between the transport chains, or temperature-related expansion effects of the transport chains. Positioning inaccuracies of the underlayer film caused by the film transport chains can be particularly problematic for packaging formats with reduced flange dimensions, so-called efficiency formats. These formats require extremely high positioning accuracy within each workstation during processing on the thermoforming packaging machine to ensure high-quality packaging. Therefore, it is crucial to guide the troughs formed at the beginning of the thermoforming packaging machine precisely to the subsequent workstations along the transport chain. This ensures that the processes taking place within them, such as sealing and cutting operations, can be carried out with the required accuracy. Failure to do so can result in inaccurate seals, potentially even being trimmed, thus increasing the reject rate. In particular, it has become apparent that with long thermoforming packaging machines and correspondingly long transport chains, the weight of the transport chains makes it technically very difficult to precisely feed the film web clamped between them to the respective workstations, and especially to reliably position it with repeatable accuracy to achieve a consistent production result. Generally speaking, the longer the film transport chains, the more difficult they are to guide and position accurately. WO2024 / 089186A1 discloses a thermoforming packaging machine in which the web clamping devices attached to the film transport chains have pins that engage in a thread of a threaded spindle mounted next to the transport chain. This allows the transport chain to be driven by the web clamping devices attached to it via the threaded spindle and / or the web clamping devices to be kept at least at a distance from each other. However, the manufacturing effort and the weight of the transport chain increase considerably due to the pins provided on the individual web clamping devices. Furthermore, the threaded spindle for driving and / or guiding the web clamping devices is mounted below them in an area required for the production and transport of the troughs formed in the film web.In this area, the installation space is limited due to the clamped packaging material, making it difficult to position the threaded spindle without additional material consumption. In particular, the inward engagement of the pins in the spindle's thread can generate bending moments on the outwardly offset chain links of the transport chains, potentially leading to undesirable lateral loading of the film transport chains. Thread guidance, especially when it runs along the entire length of the machine, requires increased lubrication, which can be problematic for hygienic operation. Another issue is that as the chain elongates, the pins on the material web clamping devices no longer align with the thread pitch in the threaded spindle, potentially increasing undesirable friction effects during chain guidance. WO2007 / 090678A1 discloses a thermoforming packaging machine on which the elongation of transport chains used on it can be detected by means of a measuring device. Depending on the length measurement, the feed movement of this thermoforming packaging machine can be adjusted in a controlled manner. DE102006006523A1 discloses that the problem of chain elongation of a transport chain used in thermoforming packaging machines can be solved by using several transport chains arranged in series, i.e. several short transport chains. EP2740679A1 discloses a thermoforming packaging machine in which, depending on the detected position of the packaging format arriving in front of a sealing station, the sealing station can be aligned accordingly in a positionally accurate manner in order to be able to process this packaging format precisely in the following work cycle by means of its realignment. US2005 / 0056720A1 discloses a thermoforming packaging machine in which lateral transport chains arranged on both sides can be driven together via intervening, torsionally rigid coupling axes. DE102021126067A1 discloses a guide profile for lateral transport chains used on a thermoforming packaging machine, in which both a forward and a return movement of the transport chains can be guided with reduced load. DE 26 04 861 A1 discloses a device with which a film web made of plastic is fed to an intermittently operated forming station of a thermoforming machine. The object of the invention is to provide, starting from the prior art described above, a thermoforming packaging machine and a method along which, or with which, the transport of an underlayer web can be carried out more precisely using cost-effective, simple technical means. This problem is solved by means of a thermoforming packaging machine according to claim 1 and by means of a method for fine positioning of a transport chain according to claim 12. Advantageous further developments of the invention are given by the respective subject matter of the dependent claims. The thermoforming packaging machine according to the invention comprises at least one transport chain that grips a base film and transports it in one direction for each main work cycle. Furthermore, the thermoforming packaging machine according to the invention comprises at least one drive unit for driving the transport chain in the transport direction. The invention provides that, for fine positioning of the transport chain in an area of ​​at least one work station of the thermoforming packaging machine, a pairing of several chain links moving along the work station, of the transport chain driven in the transport direction by means of the drive unit, with a separately driven toothed section can be produced. The coupling of the teeth with multiple chain links means that the teeth engage in the clear width or pitch between the pins of the transport chain, enabling precise positioning of the chain links at a distance and within the vertical operating plane of the transport chain in the area of ​​the workstation. Through the coupling between the chain links and the teeth that can be produced according to the invention—that is, the resulting positive engagement of the teeth with the chain links—the transport chain can be precisely positioned, at least in the area of ​​a workstation of the thermoforming packaging machine, within its operating or drive plane, i.e., within the plane in which the transport chain is driven. This allows the chain links, aligned by the coupling, to be guided directly at the workstation into a desired target position.This makes it possible to hold the transported underlay or the held troughs with the highest precision and under a desired tension for a work process within the workstation. Because the toothing engages positively with the chain links directly at the workstation location in the invention—that is, the mating of the chain links and the toothing occurs within the workstation area—the workstation has an auxiliary mechanism that engages positively between the chain links of the transport chain to assist the movement of the driven transport chain in the transport direction when feeding the clamped film web into a desired target position within the workstation. The positive locking created between the chain links gripped by the toothing allows them to be automatically aligned with each other, enabling precise positioning of the clamped underlayer film. This results in a more accurate manufacturing process. The inventive engagement of the teeth with the chain links in the area of ​​the workstation ensures that no transverse load acts on the paired chain links. The positive locking effect created by the teeth allows the chain links to be stabilized both in and across the production direction, so that they hold the bottom film in a precise position within the workstation. Preferably, the toothing is formed by a comb, a drive chain, or at least one gear that can roll in the transport direction and engages with the moving chain links. These technical means can be optimally engaged with the moving chain links of the transport chain and can support the driving of the transport chain in the transport direction in such a way that the engaged chain links of the transport chain are precisely aligned in the area of ​​the workstation and brought precisely to the target position or held there, so that the underlay held by the transport chain can be precisely positioned for a work operation at the workstation. According to one embodiment, the toothing is formed by several gears within the workstation that are paired with the chain links from below and / or from above. It would be conceivable for these gears to engage intermittently with the transport chain, at least temporarily, while the chain is being slowed down until it reaches a target position within the workstation. It would be possible that, for the production of the teeth, the gears paired with the chain links from above within the workstation are positioned offset from the gears paired with the chain links from below, in order to engage alternately along the transport chain. According to one embodiment, the workstation comprises a lower tool part and an upper tool part, in particular a lower sealing tool part and an upper sealing tool part. Preferably, the teeth are formed on the lower tool part and / or on the upper tool part of the workstation. In particular, the teeth can be engaged with the chain links inserted into the workstation by means of a lifting movement of the lower tool part and / or the upper tool part, i.e., brought into positive engagement. It would be advantageous if the workstation for each work process had at least one adjustable tool, such as a sealing tool and / or a cutting tool, and if the toothing, acting as a leading tooth pattern to create the mating with the chain links, could be moved. This would allow the underlayer to be precisely aligned relative to the tool before it is processed within the workstation. In particular, the toothing is mounted in a way that allows it to be adjusted relative to the workstation in the transport direction. This enables the position of the toothing relative to the workstation to be changed. Specifically, the toothing can support the feed movement of the transport chain in the transport direction by engaging with the chain and moving together with it in the transport direction. Most importantly, the toothing can be moved along the transport direction in such a way that, when coupled with the chain links, it precisely pushes them into a desired target position through positive engagement. The toothing moves along with the coupled chain links in the transport direction to precisely position them and bring them into the target position, ensuring that the bottom film is precisely aligned and tensioned at the latest when it reaches the target position. One embodiment of the invention provides that the toothing is adjustable in the transport direction by means of a linear drive. A servomotor or pneumatic linear drive would be conceivable for adjusting the toothing in the transport direction. As an auxiliary drive, the linear drive can be controlled synchronously with the drive unit of the transport chain to assist the drive unit in moving the transport chain into the workstation. Preferably, the linear drive is mounted in a height-adjustable manner. This allows the adjustable toothing, in particular the comb adjustable by the linear drive, to be moved into and out of the chain links. The mating of the chain links with the toothing could thus be achieved intermittently, resulting in gentle operation of the conveyor chain. One variant envisions that the teeth can be mated with the chain links from either below or above. Regardless of whether the teeth engage the chain links from below or above, they allow for precise positioning within their drive plane. It would be conceivable that teeth formed by an adjustable, mounted comb could be mated with the chain links from below. Alternatively, teeth formed by a driven drive chain or a rolling gear moving in the transport direction could be mated with the chain links from above to ensure precise alignment. According to one embodiment of the invention, the mating of the chain links with the teeth can be intermittently established in the area of ​​the workstation. This can lead to reduced wear of the chain links. In particular, the teeth can be adjusted during a feed movement of the transport chain from a position in which they are spaced apart from the chain links to a position in which they are mated with the chain links, i.e., engage with them in a positive-locking manner. Preferably, the engagement of the chain links with the teeth can be achieved at least temporarily during intermittent braking of the transport chain. This allows the moving teeth to engage synchronously with the driven chain links only at the end of a feed cycle, precisely positioning them along a braking ramp of the transport chain until they come to a standstill, in a positive-locking engagement with the desired chain pitch. The teeth engaged between the chain links act as spacers to prevent the chain links from being driven into the workstation under compressive stress. According to one embodiment, the coupling of the chain links with the teeth can be achieved even before intermittent braking processes of the transport chain, for example, in advance during a tensile (start-up) movement of the transport chain. This may facilitate the engagement of the teeth with the chain links. It would be conceivable that the toothing at the target position of the film feeder remains engaged with the chain links at least temporarily during a work process of the workstation, in order to keep them positively locked for the work process. It would be conceivable to create a coupling between the chain links and the teeth, at least temporarily, during intermittent start-up phases of the transport chain. In this design, the teeth could assist the drive unit of the transport chain at the beginning of the film feed, thus making it easier to overcome the high initial starting torque required to start the transport chain. One variant provides that a pairing between the teeth and the chain links can be produced along at least five, preferably along at least ten chain links, in order to align the transport chain along these chain links by means of a positive engagement. In particular, the teeth are made of plastic. This allows for gentle handling, enabling precise positioning of the transport chain within the workstation. Preferably, the engagement length for the mating is variable. This allows the mating between the chain links and the teeth to be selected so that the engagement length can be adapted to a process length or process format within the workstation. It would be conceivable to select the engagement length for the mating such that it corresponds at least to the process length of the format being handled in the workstation, in order to enable fine positioning of the chain links within the workstation area over the entire length of the format. The invention provides that the workstation functions as either a sealing station or a cutting station. Processes are carried out at these stations that particularly benefit from precise positioning of the transport chain, i.e., accurate positioning of the bottom film, in order to produce high-quality packaging. Specifically, the precise holding of the bottom film by means of the transport chain allows for the creation of precise sealing seams at these stations, or for the precise cutting of packaging so that the sealing seams are not cut. It would be conceivable that, along the thermoforming packaging machine, for the fine positioning of the transport chain at several workstations, a pairing of multiple chain links of the transport chain, driven in the transport direction by the drive unit, with their respective, separately driven teeth, could be produced. In particular, the fine positioning of the transport chain is carried out at a sealing station, a cross-cutting station, and possibly also at a longitudinal cutting station of the thermoforming packaging machine. Thus, the work processes carried out at these stations lead to precise results. It would be conceivable to create the coupling in a preliminary stage of the transport chain. Creating the coupling directly in the preliminary stage of the transport chain means that, at least in the area of ​​the workstation where precise positioning of the transport chain is required, lateral loads cannot be transferred to the transport chain due to the positive engagement. The coupling in the preliminary stage of the transport chain thus ensures that the engaged chain links align precisely with each other within the drive plane of the preliminary stage and can be held there. Preferably, the coupling can be established in the upstream section of the transport chain at the level of a sealing station of the thermoforming packaging machine. This creates a central drive for the transport chain along the thermoforming packaging machine, which can be used to assist the chain feed, at least intermittently. It would be conceivable to incorporate at least one omega deflection in the return run of the conveyor chain. This would allow a supported lower run of the conveyor chain to be guided over it. It would also be conceivable to configure the omega deflection as a tensioning device for setting a desired chain tension. One variant proposes that, depending on the vertical load on the toothing generated and detected during the positive engagement, the chain tension, generated by the omega deflection, can be dynamically adjusted. In this variant, the toothing is also used as part of a measuring device to detect increasing sag in the transport chain, based on which the omega deflection automatically increases the chain tension. The vertical load can be detected, for example, at a bearing of a drive unit configured to power the toothing, such as a servo motor. One embodiment provides that the toothing is part of a fine-adjustment unit that can be moved along a closed cam track. Along the cam track, this fine-adjustment unit can be moved section by section as a module so that it engages with the chain links, i.e., is paired with them, in order to precisely position them in the area of ​​the workstation. It can then be moved along a subsequent section of the cam track so that it disengages, i.e., is decoupled from the chain links, allowing them to continue moving with minimal wear. In other words, along the closed cam track, the toothing is only used section by section or temporarily to form the pairing with chain links in the area of ​​the workstation.This enables precise positioning of the chain links within the workstation, particularly in their target position where it is most needed to accurately position the chain links for the processes taking place there. Subsequently, releasing the chain links—that is, extending the teeth from the chain links—leads to a wear-reduced progression of the chain links. It would be conceivable for the fine adjustment unit to be located on a lower and / or upper tool part of the workstation. It is conceivable that the workstation incorporates a guide for the transport chain. This guide could be located on the inner side of the transport chain facing the underlayment and / or on the outer side facing away from the underlayment. It is possible that the toothed engagement and the guide within the workstation would work together to precisely align the chain links at a target position. Furthermore, the invention relates to a method for the fine positioning of a transport chain in an area of ​​at least one workstation of a thermoforming packaging machine according to the invention. According to the invention, a pairing of several chain links of the transport chain, driven in the transport direction by a drive unit, is produced along the workstation with a separately driven toothed section. This allows the driven transport chain, and in particular its chain links, to be positively engaged by the toothed section driven in the workstation area, enabling it to be driven without lateral load. Furthermore, the positive engagement ensures that the chain links align themselves with each other in such a way that they can be precisely moved into the workstation to a desired target position, thus accurately positioning the clamped underlay film for the processes taking place within it. By creating a mating between the toothed section and the chain links of the transport chain in the workstation area, i.e., through the resulting positive engagement, the transport chain can be precisely fine-tuned within its drive or operating plane, allowing the gripped underlay film to be held in the correct position at the workstation for the processes taking place within it.As a logical consequence, work processes at the workstation can then be carried out more precisely in order to produce high-quality packaging. Preferably, the coupling of the chain links with the teeth is intermittently performed in the area of ​​the workstation, particularly during intermittent braking processes of the transport chain. This enables gentle operation of the transport chain. The invention relates to the use of a driven toothing for a pairing with several chain links of a driven transport chain at at least one workstation according to the invention of a thermoforming packaging machine for fine positioning of the transport chain at the workstation of the thermoforming packaging machine. An advantageous variant is achieved by using a servomotor-driven chain drive with a toothed carrier chain, a servomotor-rotatable, linearly movable gear with teeth, and / or a comb with teeth driven by a linear drive for fine positioning of the transport chain at the workstation of the thermoforming packaging machine. The present invention is explained in more detail with reference to exemplary embodiments shown in the figures. These show: Fig. 1 an intermittently operating thermoforming packaging machine in perspective view, Fig. 2 a thermoforming packaging machine shown in side view in schematic representation, Figs. 3, 4 to 5 schematically depicted devices for fine positioning of a transport chain in the area of ​​a sealing station of the thermoforming packaging machine, Fig. 6 a transport chain of the thermoforming packaging machine with omega deflection in the return, and Fig. 7 a chain drive for fine positioning of a transport chain of a thermoforming packaging machine. Identical components are consistently labelled with the same reference symbols in the figures. Fig. 1 shows a perspective view of a packaging machine configured as an intermittently operating thermoforming packaging machine 1. This thermoforming packaging machine 1 has a forming station 2, a sealing station 3, a cross-cutting station 4, and a longitudinal cutting station 5, arranged in this order in a transport direction R on a machine frame 6. On the infeed side of the machine frame 6 is a feed roller 7 from which a bottom film 8 is unwound. Furthermore, the thermoforming packaging machine 1 has a transport chain 9 that grips the bottom film 8 and transports it further in the transport direction R for each main work cycle, in particular transport chains or clamping chains 9 arranged on both sides. In the illustrated embodiment, the forming station 2 is designed as a thermoforming station in which cavities M (see Fig. 2) are formed into the base film 8 by thermoforming, for example, using compressed air and / or vacuum. The forming station 2 can be configured such that several cavities are formed side by side in the direction perpendicular to the transport direction R. A filling section or insertion area 10 is provided downstream of the forming station 2 in the transport direction R, in which the cavities M formed in the base film 8 are filled with product. The filling of the cavities M can be carried out manually by an operator. The sealing station 3 has a hermetically sealable chamber 3a in which the atmosphere in the recesses M can be evacuated or replaced by gas purging with an exchange gas or with a gas mixture before sealing with a top film 12 dispensed from a top film receptacle 11. The cross-cutting device 4 can be designed as a punch that cuts the bottom film 8 and the top film 12 in a direction transverse to the transport direction R between adjacent troughs M. The cross-cutting device 4 operates in such a way that the bottom film 8 is not cut across its entire width, but at least in one edge area remains intact. This allows for controlled onward transport through the conveyor chain 9. The longitudinal cutting station 5 can have a knife arrangement with which the bottom film 8 and the top film 12 are cut between adjacent troughs M and at the lateral edge of the bottom film 8 in the transport direction R, so that individual packages V are present behind the longitudinal cutting station 5. The right and left transport chains 9 of the thermoforming packaging machine 1, which grip the bottom film 8 on both sides, can each be in the form of a roller chain. The two transport chains 9 are each protected on the outside by a side panel 13 of the thermoforming packaging machine 1. The thermoforming packaging machine 1 also has a control unit 14. Its function is to control and monitor the processes taking place in the thermoforming packaging machine 1. A display device 15 serves to visualize and / or influence the process sequences in the thermoforming packaging machine 1 for or by an operator. The thermoforming packaging machine 1 is shown in a schematic side view in Fig. 2. The lateral transport chains 9 are assembled from chain links 16 and, as mentioned, can be roller chains to transport the bottom film 8 along the thermoforming packaging machine 1 in the transport direction R. To grip the bottom film 8, the lateral transport chains 9 can be equipped with spring-loaded clamping devices. It is crucial that the transport chains 9 guide the bottom film 8 precisely into the workstations of the thermoforming packaging machine 1 and hold it in the correct position for the work processes taking place therein. If this is not the case, then sealing seams will be produced inaccurately in the sealing station 3, or sealing seams will be trimmed in the cross-cutting station 4 or the longitudinal cutting station 5. With increasing operating time of the transport chains 9, it is likely that production defects resulting from positioning inaccuracies will increase. Fig. 2 shows a schematic representation of a toothed section 17 in the area of ​​the sealing station 3. The toothed section 17 is configured to engage with several chain links 16 of the transport chain 9 in the area of ​​the sealing station 3. This engagement provides a positive locking grip on the transport chain 9, at least temporarily, in the area of ​​the sealing station 3, allowing its chain links 16 to align precisely in order to position the bottom film 8 with a predetermined tension and orientation in the sealing station 3. The toothing 17 is therefore configured for the fine positioning of the transport chain 9 in the area of ​​the sealing station 3. For this purpose, the toothing 17 can be adjusted or moved from a position P1 that is decoupled or spaced apart from the transport chain 9 to a position P1 in which it forms a pairing with several chain links 16 of the transport chain 9. This pairing occurs in the area of ​​the sealing station 3, so that the chain links 16 paired with the toothing 17 align themselves with each other in order to position the bottom film 8, clamped by the transport chain 9, precisely within the sealing station 3. To engage with the chain links 16, the toothing 17 can be adjusted and raised in the transport direction R. To release the engagement, i.e., to disengage the resulting positive connection, the toothing 17 can be lowered and returned to its initial position in the opposite direction to the transport direction R. The adjustability of the toothing 17 is schematically represented in Fig. 2 by a double crosshair. The respective movements can be at least partially superimposed to establish the engagement. The toothing 17, schematically depicted in Fig. 2, can be used to support a drive unit 18 for the transport chain 9 (see, for example, Fig. 3) in order to move the transport chain 9 into the sealing station 3. The toothing 17 therefore serves as an auxiliary drive for the drive unit 18 to precisely position the chain links 16 of the transport chain 9 for work processes taking place within the sealing station 3. This is achieved by the toothing 17 engaging the chain links 16 in a positive-locking manner before they reach their target position and accompanying them, at least partially, along the transport direction R to the target position, i.e., by pushing them along. The transport chains 9 are designed to transport the underlay 8 in the transport direction R according to a predetermined feed movement, for example according to a v / t roof profile, for each main work cycle. This feed movement consists of at least an accelerated start-up phase, in which the transport chains 9 are accelerated from a standstill, and a deceleration phase, in which the transport chains 9 are braked to come to a stop in the desired target position. During the start-up phase, the transport chains 9 are subjected to tensile stress. During the braking phase, the tensile stress on the transport chains 9 decreases, possibly even temporarily becoming a compressive stress. This can cause the chain links 16 to shift relative to each other. Therefore, in the area of ​​the workstations of the thermoforming packaging machine 1, the bottom film 8 clamped by the transport chains 9 may be positioned inaccurately. Against this background, the engagement of the teeth 17 with the chain links 16 of the transport chain 9 in the area of ​​the sealing station 3 helps to arrange the chain links 16 precisely, at least in this working area, so that the undersheet 8 can be held in a positionally accurate position within the sealing station 3. A toothing 17' comparable to toothing 17 is also provided for the cross-cutting station 4 in Fig. 2. The toothing 17' can be adjusted between position P1' and position P2' such that it engages positively with chain links 16 of the transport chain 9 in the area of ​​the cross-cutting station 4 in order to align them precisely with each other in the area of ​​the cross-cutting station 4 and to position them accurately at a target position within the cross-cutting station 4, so that the clamped lower film 8 is also tensioned in the correct position for cutting the film web within the cross-cutting station 4. The toothing 17, 17' shown in Fig. 2 can each form a pairing with several chain links 16 of the transport chain 9, driven in the transport direction R by means of the drive unit 18, in the respective areas of the sealing station 3 and the cross-cutting station 4 of the thermoforming packaging machine 1, in order to transport these chain links 16 into the respective work stations and hold them in position with precision in order to position the bottom film 8 clamped on the transport chain 9 with precision. Fig. 3 shows a schematic representation of the toothing 17 in the form of a comb 19, the position of which is adjustable relative to the sealing station 3. In particular, Fig. 3 shows that the comb 19 is height-adjustable by means of a lifting mechanism 30 and adjustable in and against the transport direction R by means of a linear drive 20 in order to engage intermittently with the chain links 16 of the transport chain 9, i.e., to be moved between the positions P1 and P2 shown in Fig. 1. It is conceivable that the comb 19 could be paired with the chain links 16 of the transport chain 9 upstream of the sealing station 3, viewed in the transport direction R, in order to then move into the sealing station 3 together with these links by activating the linear drive 20, so that the linear drive 20 acts as an auxiliary drive to support the drive unit 18. According to Fig. 3, the driven toothing 17 could therefore be used as a central drive supplementing the drive unit 18 along a leading section 21 of the transport chain 9. Fig. 3 shows in a dashed line representation that the comb 19 can either alternatively or additionally be coupled to the chain links 16 from above in order to position them precisely in the area of ​​the sealing station 3. It is conceivable that the two combs 19 shown schematically in Fig. 3, i.e., the lower and the upper comb 19, could form a claw coupling, gripping the chain links 16 from below and above and transporting them into the sealing station 3 to position them precisely. Fig. 4 shows a schematic representation of the toothing 17 being formed by a driven drive chain 22. The drive chain 22 can have a belt with teeth 32 (see Fig. 7) and is preferably mounted so as to be movable in and against the transport direction R and height-adjustable in order to produce intermittent engagement with the chain links 16. The drive chain 22 can be in the form of a chain drive. The lower run formed by the drive chain 22 in Fig. 4 can be positively engaged with the chain links 16 in order to position them precisely within the sealing station 3. It would also be conceivable for the drive chain 22 to be positively engaged with the chain links 16 upstream of the sealing station 3 and to move into the sealing station 3 together with them in the transport direction R, so that they can be positioned precisely within it. Fig. 5 shows that the toothing 17 is formed by a gear 23 that can roll along the transport chain 9 in the transport direction R and engages with the moving chain links 16. As the gear 23 rolls along the chain links 16, these can be aligned relative to each other within the sealing station 3 to hold the clamped underfilm 8 in precise position. The rolling of the gear 23 along the chain links 16 can begin outside the sealing station 3 to reliably align them until they reach the target position. Fig. 6 shows that an omega deflection or omega guide 25 is provided in a return section 24 of the transport chain 9. This omega deflection 25 can be configured as a tensioning device. In particular, it would be possible for the omega deflection 25 to dynamically react to a sag in the transport chain 9 detected via the comb 19 by adjusting a preset tension of the transport chain 9 accordingly, for example by changing the position of a gear inserted thereon. Fig. 7 shows the teeth 17 formed by the drive chain 22 in engagement with some chain links 16 in an isolated view. The drive chain 22 can be driven by a servo drive 26 via a gear pair 31a, 31b to drive the chain links 16, which are positively coupled to the drive chain 22, in the transport direction R. It would be conceivable for the drive chain 22 to be height-adjustable and movable in and against the transport direction R. This would make it possible to engage the drive chain 22 intermittently with the chain links 16, particularly during braking. Fig. 7 further shows an engagement length L according to which seven teeth 32 of the drive chain 22 are coupled with the chain links 16.

Claims

Thermoforming packaging machine (1), comprising at least one transport chain (9) which grasps a bottom film (8) and transports it in a transport direction (R) for each main work cycle, and at least one drive unit (18) for driving the transport chain (9) in the transport direction (R), wherein, for fine positioning of the transport chain (9) in an area of ​​at least one work station of the thermoforming packaging machine (1), a pairing of several chain links (16) of the transport chain (9) driven in the transport direction (R) by means of the drive unit (18) with a separately driven toothing (17, 17') can be produced, characterized in that the work station is a sealing station (3) or a cutting station (4, 5). Thermoforming packaging machine according to claim 1, characterized in that the toothing (17, 17') is formed by a comb (19), by a drive chain (22) or by at least one gear (23) which is rollable in the transport direction (R) and engages in the moving chain links (16). Thermoforming packaging machine according to one of the preceding claims, characterized in that the toothing (17, 17') is adjustable relative to the work station in the transport direction (R). Thermoforming packaging machine according to one of the preceding claims, characterized in that the toothing (17, 17') is adjustable in the transport direction (R) by means of a linear drive (20). Thermoforming packaging machine according to claim 4, characterized in that the linear drive (20) is mounted in a height-adjustable manner. Thermoforming packaging machine according to one of the preceding claims, characterized in that the toothing (17, 17') can be paired with the chain links (16) from below and / or from above. Thermoforming packaging machine according to one of the preceding claims, characterized in that in the area of ​​the work station the pairing of the chain links (16) with the teeth (17, 17') can be produced intermittently, preferably at least temporarily during intermittent braking operations of the transport chain (9) and / or at least temporarily during intermittent start-up operations of the transport chain (9). Thermoforming packaging machine according to one of the preceding claims, characterized in that an engagement length (L) for the mating is variable. Thermoforming packaging machine according to one of the preceding claims, characterized in that along the thermoforming packaging machine (1) for fine positioning of the transport chain (9) at several workstations of the thermoforming packaging machine (1) a pairing of several chain links (16) of the transport chain (9) driven in the transport direction (R) by means of the drive unit (18) with respective, separately driven teeth (17, 17') can be produced. Thermoforming packaging machine according to one of the preceding claims, characterized in that the pairing can be produced in a forward run (21) of the transport chain (9) and / or at least one omega deflection (25) is provided in a return run (24) of the transport chain (9). Thermoforming packaging machine according to one of the preceding claims, characterized in that the toothing (17, 17') is part of a fine adjustment unit movable along a closed cam track. Method for fine positioning of a transport chain (9), characterized in that in an area of ​​at least one work station configured as a sealing station (3) or as a cutting station (4,5) of a thermoforming packaging machine (1) a pairing of several chain links (16) of the transport chain (9) driven in the transport direction (R) by means of a drive unit (18) is produced with a separately driven toothing (17, 17'). Method according to claim 12, characterized in that the pairing of the chain links (16) with the teeth (17, 17') is produced intermittently in the area of ​​the work station, in particular during intermittent braking processes of the transport chain (9). Use of a driven toothing (17, 17') for a pairing with several chain links (16) of a driven transport chain (9) at at least one workstation of a thermoforming packaging machine (1) configured as a sealing station (3) or as a cutting station (4, 5), in particular use of a servomotor-driven chain drive with a drive chain (22) having the toothing (17, 17'), a servomotor-rotatable, linearly movable gear (23) having the toothing (17, 17'), and / or a comb (19) having the toothing (17, 17') that can be driven by means of a linear drive (20), for fine positioning of the transport chain (9) at the workstation of the thermoforming packaging machine (1).

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