System for wrapping pallets loaded with articles with a film

Abstract

The invention relates to a system (100) for wrapping pallets (P) loaded with articles with a film that can be pulled off a film reel (F). The system (100) comprises a winding device (1), wherein the winding device (1) has at least one support frame (3) having a winding arm (4) which is rotatably arranged thereon about an axis of rotation (RA), and having an unwinding unit (5). The winding arm (4) can be driven by a motor (10) which is connected to a control unit (8) of the system (100) and can be controlled in an open-loop or closed-loop manner. The unwinding unit (5) of the rotatable winding arm (4) has at least one reel chuck (6) for receiving the film reel (F) in a supporting manner and at least one roller arrangement (7) having at least one first roller (R1) and one second roller (R2) for guiding and pretensioning the film. At least the first roller (R1) can be driven by means of at least one first roller motor (11) which can be controlled in an open-loop and / or closed loop manner and is connected to the control unit (8) of the system (100). A motor speed of the motor (10) is detected. A film requirement per revolution of the winding arm (4) is determined depending on a circumference of the loaded pallet (P) to be wrapped. Depending on the detected motor speed of the motor (10) and the film requirement per revolution of the winding arm (4), a speed of the first roller motor (11) is adjusted by means of a control routine executed in the control unit (8) in such a way that a predefined film tension is maintained.

Description

[0001] System for wrapping pallets loaded with articles with a film

[0002] The invention relates to a system for wrapping pallets loaded with articles with a film.

[0003] Pallets are used for transporting and storing items arranged on them. To prevent items from falling or sliding off the pallets, the loaded pallets can be wrapped with film, so that the arrangement of the items on the pallet is fixed by the elastic deformation of the film – sometimes also called stretch film. In the following, the assembly of pallet and the items arranged on it will generally be referred to simply as a pallet, encompassing the items themselves.

[0004] Various devices are available for wrapping pallets loaded with goods using film. In one design, a pallet is placed on a rotating platform, and the pallet is wrapped with film by rotating it relative to a stationary wrapping device. Alternatively, film can be moved around a stationary pallet by a movable device, for example, with rotary arm wrappers. Such arm wrappers may include a support frame to which a rotating wrapping arm is attached. An unwinding unit is provided on the wrapping arm, so that the unwinding unit moves around the goods to be wrapped, such as pallets and / or goods, by rotating the wrapping arm.

[0005] Typically, pallets have a base that is not circular, but rectangular, for example. This results in a prismatic shape for the combination of pallet and items, rather than a cylindrical one. The lateral edges of the prism extend vertically from the corners of the pallet and are defined by the combination of items arranged on the pallet.

[0006] When a wrapping unit is moved around a pallet to wrap the pallet and its contents with film, a non-circular pallet shape causes the radial distance between the pallet / items and the wrapping unit to change during each rotation of the wrapping unit. Consequently, if the film is supplied by the wrapping unit at a constant speed, the film tension changes. For example, there will be higher tension in the film at the corners of the pallet than on the sides. Simultaneously, the film tension changes when the speed at which the wrapping unit moves around the pallet is altered.

[0007] To maintain a predefined film tension, it is necessary to increase and / or decrease the film supply speed during each rotation of the unwinding unit around the pallet, depending on the position and rotational speed. For this purpose, a control system can be provided in which the film tension is measured and adjusted based on a target / actual value comparison.

[0008] In some prior art embodiments, sensors are used to measure film tension. However, a problem arises because the speed at which the sensors can acquire measurements and the speed at which the sensor signals can be processed are too slow to ensure reliable control of the film tension. In particular, the rotational speed and frequency at which the unwinding unit moves during pallet rewinding are too high to allow for reliable detection of the film tension using sensors.

[0009] The object of the present invention is therefore to provide a system that enables reliable maintenance of film tension in an unwinding unit, even when the unwinding unit is operated at different speeds or when pallets with different geometries are to be wrapped with film. The system should also be inexpensive to manufacture and easy to adapt. This object is achieved by the system according to claim 1. Further advantageous aspects, details, and embodiments of the invention will become apparent from the dependent claims, the description, and the drawings. The present invention relates to a system for wrapping pallets loaded with articles with a film that can be peeled from a film spool. The system comprises a winding device, wherein the winding device has at least one support frame with a winding arm rotatably arranged thereon about a pivot axis and comprising an unwinding unit.The winding arm can be driven by a controllable and / or adjustable motor connected to a control unit of the system. The control unit can communicate with the motor and receive signals about its operation, such as measurement values. The control unit, the motor, and the signal connection can also be configured so that the control unit can send control signals to the motor, for example, to control its speed.

[0010] The unwinding unit of the rotating winding arm comprises at least one spool chuck for supporting the film spool and at least one roller assembly with at least one first roller and one second roller for guiding and tensioning the film. At least the first roller can be driven by at least one controllable and / or adjustable first roller motor connected to the system's control unit. Similar to the motor for driving the winding arm, the first roller motor can be in signal communication with the control unit, whereby the control unit can receive signals from the first roller motor and / or send control signals to the first roller motor via this signal connection.

[0011] The motor speed is recorded. The film requirement per revolution of the winding arm is determined based on the circumference of the loaded pallet to be wrapped. The film requirement per revolution of the winding arm is specifically defined as the film length required to completely wrap the loaded pallet and can preferably be expressed in meters per wrap. Depending on the recorded motor speed and the film requirement per revolution of the winding arm, a control routine implemented in the control unit adjusts the speed of the first roller motor to maintain a predefined film tension. The film tension can be expressed, for example, as a percentage. It describes the tension that occurs in the film when less film is supplied by the unwinding unit.The film is supplied more slowly than would be necessary due to the rotation of the winding arm and the geometry of the objects to be wrapped.

[0012] By executing the control routine, a predefined film tension can be maintained based on the detected motor speed of the arm and the film requirement per revolution of the winding arm, without the need for complex sensors to measure and regulate the film tension. Because complex sensors are eliminated, a system built and controlled according to the principle described above can be manufactured more cost-effectively. Furthermore, there is no need to calibrate the measuring instruments to a specific application. Instead, adaptation to a specific application, such as the shape or dimensions of the objects to be wrapped, can be achieved directly through interaction with the control unit, for example, via a human-machine interface (HMI). This makes the system more versatile than other systems known in the prior art.At the same time, the control routine reliably maintains a predefined film tension, even if the speed at which the unwinding unit moves around the pallet changes. A particularly advantageous feature of this system is that it allows for precise adjustment and maintenance of the predefined or desired film tension, even at high winding speeds.

[0013] The control routine can preferably have access to information characterizing the shape of the objects to be wrapped, such as the outline of the items or the pallet. This information can be used, for example, to determine the film requirement per revolution of the wrapping arm. The information can be stored in the control unit. Alternatively, or in addition to this information—similar to the dimensions of the pallet to be wrapped—it can be determined by the control routine itself or transmitted to the control unit by a system user, for example, using an HMI. Because the film tension is controlled taking into account the motor speed of the motor driving the wrapping arm, the control routine can also be used when the wrapping arm rotates at different angular velocities or rotational speeds in different applications.The predefined film tension can still be maintained.

[0014] For example, with a predefined constant film tension, the speed of the first roller motor can be increased if the motor speed of the other motor is increased. With a predefined constant film tension, the speed of the first roller motor can be decreased if the motor speed of the other motor is decreased. The speed of the first roller motor can be increased with a predefined constant film tension when wrapping a corner of a non-round pallet. The speed of the first roller motor can be decreased with a predefined constant film tension when wrapping a side of a non-round pallet.

[0015] If, for example, it is predefined that the film tension should be reduced, the speed of the first roller motor can generally be increased. If, for example, it is predefined that the film tension should be increased, the speed of the first roller motor can generally be reduced.

[0016] The speed of the first roller motor can be increased if a higher film output per revolution is required, provided the other parameters remain unchanged. Conversely, the speed of the first roller motor can be decreased if a lower film output per revolution is required, provided the other parameters remain unchanged.

[0017] In a preferred embodiment, the motor speed is determined by measuring the motor frequency, and the motor speed is then calculated from this frequency using a control routine executed in the control unit. The motor speed can be measured, for example, starting from a known or measured motor frequency, taking into account the motor's design, such as the motor type, the number of pole pairs, and / or the motor slip. For this purpose, formulaic relationships describing the motor's operation can be used. Additionally or alternatively, the motor's operation can be investigated, for example, during a commissioning phase, and correlations between the motor speed and the motor frequency can be determined, such as a machine characteristic curve, which can then be used to determine the motor speed based on the motor frequency.The correlations can be linearized at one or more preferred operating points of the system. These relationships can be stored in the control unit, for example, in the form of a lookup table, a function, or a neural network trained with various machine parameters. This allows the relationships to be used when the control routine is executed to determine the motor speed. By determining the motor frequency and speed, measuring the motor speed or RPM becomes unnecessary. The system can therefore react quickly to changes in motor speed and is less expensive to manufacture.

[0018] Preferably, the rotational speed of the winding arm and / or the time required for one rotation of the winding arm are determined from the motor's rotational speed by means of a control routine executed in the control unit. This determination can be made taking into account machine parameters, such as the gear ratio between the motor and the winding arm. The rotational speed can be determined, for example, in rpm (revolutions per minute) or rps (revolutions per second).

[0019] In a preferred embodiment, the control routine executed in the control unit further takes into account the circumference of the first and / or second roller to adjust the speed of the first roller motor. This allows for more precise control of the predefined film tension. Preferably, the second roller can be driven by a second roller motor connected to the system's control unit, which can be controlled and / or regulated. A signal connection can also exist between the second roller motor and the control unit, enabling the transmission of (command) signals between the roller motor and the control unit.

[0020] The first and second roller motors can be operated independently. In this case, the rotational speed of the second roller can be set and controlled independently of the rotational speed of the first roller, and vice versa. The second roller motor thus allows the rotational speed of the second roller to be adjusted independently of the rotational speed of the first roller, depending on the operating conditions. If the first and second roller motors drive their respective first and second rollers at different rotational speeds, pre-stretching of the film can occur.

[0021] Pre-stretched films – sometimes also called pre-stretched films – have their thickness reduced through pre-stretching, which simultaneously lengthens the film. A pre-stretched film can therefore cover a greater distance compared to a non-pre-stretched film. The amount of film required to wrap a certain arrangement of items on pallets is therefore lower with a pre-stretched film than with a non-pre-stretched film.

[0022] Alternatively, the first and second rollers can be mechanically coupled and driven together by the first roller motor. For example, a gear ratio can be provided between the first and second rollers, so that the rotational speed of the first roller is in a certain ratio to the rotational speed of the second roller. In this case, if the first roller is driven by the first roller motor, the second roller rotates at a predetermined speed determined by the gear ratio. Because the rotational speed of the first roller can differ from that of the second roller, this embodiment is also suitable for providing pre-stretching of the film. At the same time, it is characterized by a particularly simple design.In a preferred embodiment, a definable pre-stretch of the film in the roll assembly can be set using the control routine implemented in the control unit. By adjusting the pre-stretch via the control unit, the system can be quickly adapted to different operating conditions. This eliminates the need for a complex reconfiguration of the unwinding unit, which would be required, for example, to change the diameter ratio of the first roll to the second roll. Instead, the rotational speed of the first roll motor relative to the second roll motor can be adjusted by the control unit.

[0023] Preferably, to set the definable pre-stretch, the first and second rollers are driven at different rotational speeds, with the first and second rollers having an identical diameter. This allows the pre-stretch to be set and adjusted particularly easily.

[0024] It is particularly preferred that, for a pre-stretch of 100%, the first roll is driven at twice the speed of the second roll. For a pre-stretch of 200%, the first roll can be driven at three times the speed of the second roll. For a pre-stretch of 300%, the first roll can be driven at four times the speed of the second roll. These pre-stretch values ​​have proven particularly advantageous because, for many of the films used in the prior art, a good compromise between stability and elongation is achieved. In this context, it should be noted that, in the present sense, a pre-stretch of 100% means that the film is stretched to approximately twice its unstretched length.Similarly, a "pre-stretch of 200%" corresponds to an extension of the film to approximately three times its unstretched length, and a "pre-stretch of 300%" corresponds to an extension to approximately four times its unstretched length. If the first and second rollers can be driven independently, the pre-stretch value can be dynamically adjusted or regulated during the wrapping process. The same is possible if the gear ratio between the first and second rollers is dynamically adjustable, for example, by means of a switchable gearbox. This allows the pre-stretch—and thus the length and thickness of the film—to be dynamically adjusted, for example, if some items on the pallet are to be wrapped with a stronger, more durable layer of film than others.This might be the case, for example, if items are heavy and slipping or falling off can only be prevented by a firm and durable film wrapping. For lighter items, on the other hand, a thinner, weaker, and less durable wrapping may suffice to hold the items together and on the pallet. Accordingly, the film thickness can be selected appropriately by adjusting the pre-stretch. Adjusting the pre-stretch during the wrapping process can also reduce overall film consumption.

[0025] Preferably, the control routine implemented in the control unit can be used to determine the film requirement per unit of time – for example, in meters per minute – from the specified film requirement per revolution of the winding arm – for example, specified in meters per wrap. A feed rate of the film dispensed by the unwinding unit can then be set, whereby the feed rate is lower, in particular approximately 20% lower, than the film requirement per unit of time. The interaction between the feed rate at which the film is supplied and the film requirement influences the film tension, as explained above. As already explained, the film requirement per unit of time is not constant during one revolution of the unwinding unit around a pallet if the pallets have a non-circular cross-section.Especially with non-round pallets, the feed rate can be varied during one revolution around the pallet to ensure a uniform film tension. For example, the film feed rate can be increased when wrapping the corners of a rectangular pallet and decreased when wrapping the sides. Preferably, the predefined film tension is a constant value or a range of values. A film tension of 20% has proven particularly advantageous. Alternatively, the film tension can be dynamically adjusted during the wrapping process, similar to the pre-stretch described above. For instance, more delicate items located in the upper part of the pallet can be wrapped with less film tension than heavier, more robust items in the lower part of the pallet.This prevents damage to the more delicate parts, while at the same time ensuring that the more robust items are firmly bound together and preventing the items from slipping or falling off the pallet.

[0026] In a preferred embodiment, a stretch film made of a thermoplastic material, in particular polyethylene, is used, wherein the film has a thickness in the range between 8 pm and 40 pm. The use of such a stretch film has proven particularly advantageous because the film is well suited to the requirements of wrapping pallets loaded with articles.

[0027] Preferably, the unwinding unit, provided on a vertically extending arm section of the winding arm, is arranged so as to be movable up and down on the vertically extending arm section and, in particular, is movable in the vertical direction by means of a controllable and / or adjustable drive connected to the control unit of the system. In this way, the vertical movement of the unwinding unit can be coordinated with the rotary movement of the winding arm by the control unit sending corresponding control signals. In particular, the film tension and pre-stretch generated or maintained by the control routine can also be coordinated with the vertical position and / or the vertical positioning of the unwinding unit.

[0028] The invention further relates to a control routine for controlling a predefined film tension when wrapping pallets loaded with articles with a film that can be peeled from a film spool. Preferably, at least one step of the control routine, and more preferably the essential steps, is computer-implemented. The control routine can be executed by a control unit used in a system according to one of the embodiments described above.

[0029] The tax routine can include any combination of the following steps:

[0030] - Detection of the motor speed of a motor for driving the winding arm by the control unit;

[0031] - Determining the amount of film required per revolution of the wrapping arm depending on the circumference of the loaded pallet to be wrapped;

[0032] - Adjusting the speed of the first roller motor depending on the detected motor speed and the film requirement per revolution of the winding arm by means of a control routine executed in the control unit, so that a predefined film tension is maintained.

[0033] For example, the speed of the first roller motor can be increased if a higher film output is required, provided the other parameters remain unchanged. Conversely, the speed of the first roller motor can be increased if the predefined film tension is to be reduced, provided the other parameters remain unchanged. If, on the other hand, the predefined film tension is to be increased while the other parameters remain unchanged, the speed of the first roller motor can be reduced.

[0034] To determine the motor's speed, its frequency can be calculated, and from this, its rotational speed can be derived. The rotational speed can then be converted into a motor speed. Equations for this purpose can be stored in the control unit. For example, the motor frequency can be determined by measurement or provided to the control unit by a user.

[0035] From the motor's rotational speed, the rotational speed of the winding arm and / or the time required for one rotation of the winding arm can be determined. This can take into account factors such as the gear ratio between the motor and the winding arm and / or the geometric characteristics of the winding arm. Furthermore, the circumference of the first and / or second roller can be considered to adjust the speed of the first roller motor.

[0036] The geometric shape of the pallet and / or the items loaded onto the pallet can also influence the speed of the first roller motor. For example, if the film is wrapped around an edge of the pallet or the items on it, the speed of the first roller can be increased to maintain the film tension at the predefined value. If the film is wrapped around a flat surface, the speed of the first roller can be decreased so that the film tension does not fall below the predefined value.

[0037] The film tension can preferably be adjusted to a constant value or range of values.

[0038] One aspect of the invention further relates to a computer program comprising instructions which, when the program is executed by a computer, cause it to perform at least one step of the control routine just described.

[0039] Although some aspects of the invention have been described in connection with the control unit, these aspects also constitute a description of the corresponding control routine, wherein a functional unit of the control unit, or more generally, a device, corresponds to a process step or a function of a process step. Similarly, aspects described within the context of a process step also constitute a description of a corresponding functional unit, element, or property of a corresponding device.

[0040] The control unit can be a local computing device (e.g., a personal computer, laptop, tablet computer, or mobile phone) with one or more processors and one or more memory devices. The control unit can be a distributed computing system (e.g., a cloud computing system with one or more processors or one or more memory devices distributed across different locations, for example, a local client and / or one or more remote server farms and / or data centers). The control unit can comprise any circuit or combination of circuits. In one embodiment, the control unit can comprise one or more processors, which can be of any type.The term "processor" is understood to mean any type of computing circuit, such as a microprocessor, microcontroller, complex instruction set (CISC) microprocessor, reduced instruction set (RISC) microprocessor, very long instruction word (VLIW) microprocessor, graphics processor, digital signal processor (DSP), multi-core processor, field-programmable gate array (FPGA), or any other type of processor or processing circuit. Other types of circuitry that may be included in the control unit may be a custom-designed circuit, an application-specific integrated circuit (ASIC), or similar, such as one or more circuits (e.g., a communications circuit) for use in wireless devices such as mobile phones, tablet computers, laptop computers, two-way radios, and similar electronic systems.The control unit may include one or more storage devices, which may contain one or more storage elements suitable for the specific application, such as main memory in the form of random access memory (RAM), one or more hard disks, and / or one or more drives that handle removable media, such as CDs, flash memory cards, DVDs, and the like. The control unit may also include some type of human-machine interface, a display device, one or more speakers, and a keyboard and / or controller, which may include a mouse, trackball, touchscreen, voice recognition device, or any other device that allows a system user to input information into and receive information from the control unit.

[0041] Some or all steps of the control routine can be performed by (or using) a hardware device, such as a processor, a microprocessor, a programmable computer, or an electronic circuit. In some embodiments, one or more of the key process steps can be performed by such a device. Depending on specific implementation requirements, embodiments of the invention can be implemented in hardware or software.The implementation can be carried out using a non-volatile storage medium such as a digital storage medium, for example a floppy disk, DVD, Blu-ray disc, CD, ROM, PROM, EPROM, EEPROM, or FLASH memory, on which electronically readable control signals are stored. These signals interact (or can interact) with a programmable computer system to execute one of the control routines described herein. Therefore, the digital storage medium can be computer-readable.

[0042] Some embodiments according to the invention include a data carrier with electronically readable control signals that can interact with a programmable computer system so that the control routines described herein are carried out.

[0043] In general, embodiments of the present invention can be implemented as a computer program product with instructions, wherein the instructions lead to the execution of one of the control routines described herein when the computer program product runs on a computer. The instructions, or the program code containing the instructions, can, for example, be stored on a machine-readable medium.

[0044] Further developments, advantages, and possible applications of the invention will also become apparent from the following description of exemplary embodiments and from the figures. All features described and / or illustrated are, individually or in any combination, fundamentally the subject matter of the invention, irrespective of their compilation in the claims or their cross-reference. The content of the claims is also incorporated into the description.

[0045] The invention is explained in more detail below with reference to exemplary embodiments shown in the figures. Figure 1 shows a simplified and schematic partial representation of an embodiment of a system with a winding device in a perspective view (showing only parts or components of the rotary arm winding system relevant to the present invention);

[0046] Fig. 2 shows a simplified and schematic representation in more detail of an embodiment of an unfolding unit in a perspective view;

[0047] Fig. 2a is a highly simplified and only roughly schematically sketched cross-section of the unwinding unit of figure 2 (with a film web located in the roller arrangement);

[0048] Fig. 3 shows a simplified and schematic representation of a pallet with a round base when wrapped with foil;

[0049] Fig. 4 shows a simplified and schematic representation of a pallet with a rectangular base when wrapped with film; and

[0050] Fig. 5 shows a flowchart of an embodiment of a control routine for controlling a predefined film tension.

[0051] For identical or similarly acting elements of the invention, identical reference numerals are used in the figures, where expedient. Furthermore, for the sake of clarity, only reference numerals necessary for describing the respective figure are shown in the individual figures. The invention is also presented in the figures only as a schematic view to illustrate its operation. In particular, the illustrations in the figures serve only to explain the basic principle of the invention. For the sake of clarity, not all components of the device are shown. Figure 1 shows a simplified and schematic partial representation of an embodiment of a system 100 with a winding device 1 in a perspective view. In particular, only those parts or components are shown in the figure.Components of the system 100 and the winding device 1 that are relevant to the explanation of the present invention are shown and specified. It is understood that the system 100 and the winding device 1 comprise further components that have been omitted for the sake of simplicity. Figure 2 shows, in simplified and schematic form, a more detailed perspective view of an embodiment of an unwinding unit 5, which is also present in Figure 1.

[0052] In the illustrated embodiment, system 100 has a winding device 1 designed as a rotary arm winding device 1. The winding device 1 is thus designed as a rotating winding device 1 with a winding arm 4 rotatably arranged on a support frame 3 or driven to rotate about a vertical axis of rotation RA, and serves to wrap pallets P loaded with articles with a film that is pulled from a film spool F during the wrapping of the pallet P (see Figure 2 for a representation of the film spool F).

[0053] The wrapping film is, for example, a stretchable film made of a plastic material, specifically a so-called stretch film, which is wrapped around the pallet P with a predetermined tension to stabilize the items on the pallet P. This stabilization can involve, firstly, fixing the items to each other so that individual items do not fall or slide off the pallet P. Secondly, the items can also be fixed to the pallet P by simultaneously wrapping the pallet P and the items on it with the film.

[0054] The pallets P loaded with articles are, for example, pallets P with several layers of respective assembled and / or grouped containers in a respective layer arrangement, in particular containers filled with beverages, such as cans, bottles or the like, whereby the containers within a respective layer may be loose or as container bundles.

[0055] The present winding device 1 and the system 100 comprising such a winding device 1 can therefore be understood as part or component of a packaging system, in particular in the beverage industry, and as such forms a packaging machine.

[0056] The loaded pallets P can be conveyed to and from a working area of ​​the wrapping device 1 in a general transport or conveying direction by means of a designated transport or conveying device, for example by means of a belt conveyor such as a roller belt or chain belt. In the working area, in particular in a space within the support frame 3, the pallet P remains stationary during the wrapping process and is rotated around by the rotating wrapping arm 4 to be wrapped with the film.

[0057] The rotating winding arm 4 is rotatably mounted with a horizontally extending arm section 4.1 on a top side of the support frame 3, in particular on a horizontal support strut, and points vertically downwards with a vertically extending arm section 4.2 which adjoins the horizontally extending arm section 4.1 at a right angle and has a free end.

[0058] A vertically movable unwinding unit 5 is arranged on the vertically extending arm section 4.2 of the rotating winding arm 4. A film spool F is carried over this unwinding unit. As the pallet P is wrapped, the unwinding unit 5 pulls the film from the film spool F and applies the film to the pallet P.

[0059] The unwinding unit 5 of the rotatable winding arm 4 has at least one spool chuck 6 for supporting the film spool F and at least one roller assembly 7 equipped with several rollers for guiding the film during winding. The unwinding unit 5 with the roller assembly 7 can, for example, be designed in a manner known to those skilled in the art. The system 100 further includes a motor 10, which is designed to drive the winding arm 4. Preferably, the motor 10 is arranged on the support frame 3 and interacts with the horizontally extending arm section 4.1 of the winding arm 4 in such a way that the latter can be set in rotation by the motor 10. For this purpose, the motor 10 can have a transmission, for example a gearbox 13, which modifies the rotary motion provided by the motor 10 such that it is suitable for moving the winding arm 4.

[0060] The roller arrangement 7 comprises at least a first roller R1 and a second roller R2 (see Figures 2, 2a). The first roller R1 and the second roller R2 guide and tension the film web FB unwound from the film roll F. The first roller R1 serves to control the film tension contained in the film to be applied to the pallet P. If there is a certain relative movement between the first roller R1 and the second roller R2, for example, if the first roller R1 rotates faster than the second roller R2, a pre-stretch of the film web FB can be induced and adjusted in addition to the film tension.

[0061] The first roller R1 is driven by a first roller motor 11, which causes the first roller R1 to rotate. The first roller motor 11 is controllable and / or adjustable. Consequently, the rotational speed of the first roller motor 11 can be influenced by a corresponding signal supplied to it, thereby adjusting the tension in the film web FB, with which the pallet P is wrapped.

[0062] In the illustrated embodiment, a second roller motor 12 is provided, which can cause the second roller R2 to rotate independently of the movement of the first roller R1. The second roller motor 12 is controllable and / or adjustable. A corresponding signal to the second roller motor 12 can rotate the second roller R2, thereby adjusting, among other things, the pre-tension of the film web FB. In certain embodiments, a fixed gear ratio between the first roller R1 and the second roller R2 can be specified, resulting in a constant relative speed between the first roller R1 and the second roller R2 and thus a constant pre-tension of the film. The motor 10 and the roller motors 11 and 12 are in signal communication S with a control unit 8 of the system 100.The control unit 8 is configured to send control commands to the motor 10 and the roller motors 11, 12 via the signal connection S and to receive signals from the motor 10 and the roller motors 11, 12. The signal connection S can be wired or wireless. The control unit 8 can evaluate information from the system 100, such as system parameters or measured values ​​recorded in the system 100, and based on this, determine control signals which are then sent via the signal connection S to the motor 10 and / or to at least one of the roller motors 11, 12 in order to control and / or regulate the movement of the winding arm 4, the tension with which the film is applied to the pallet P, and / or the pre-stretch of the film.

[0063] The control unit 8 can execute a control routine to maintain a predefined film tension. As part of this routine, the motor speed of motor 10, which rotates the winding arm 4, is measured. Depending on the circumference P of the pallet to be wrapped, the film requirement per revolution of the winding arm 4 is calculated. Based on the motor speed of motor 10 and the film requirement per revolution, the speed of the first roller motor 11 is adjusted to maintain the predefined film tension.

[0064] To determine the motor speed of motor 10, a motor frequency can be calculated, from which the rotational speed of motor 10 is then determined using the control routine. Based on the rotational speed of motor 10, the control routine can determine the number of revolutions of the winding arm 4 and / or the time for one revolution of the winding arm 4. For this purpose, a known gear ratio between the motor speed of motor 10 and the movement of the winding arm 4, which is caused by the rotation of motor 10, can be used. Additionally, the circumference of the first roller R1 and / or second roller R2 can be taken into account.

[0065] When adjusting the speed of the first roller motor 11, the shape of the pallet P (i.e. the base area of ​​the pallet P) and / or the shape of the articles arranged on the pallet P can also be taken into account, as is made clear by the following explanations in connection with Figures 3 and 4.

[0066] Figure 3 shows a schematic top view of a pallet P with a circular base, which is wrapped with a film web FB supplied by an unwinding unit 5 of a winding device 1. The circle surrounding the pallet P denotes the orbit U of the unwinding unit 5. During the winding process, the unwinding unit 5 moves along the orbit U, while film is continuously supplied at a certain feed rate to wrap the pallet P and the items arranged on the pallet P with the film.

[0067] Due to the circular base, the film requirement supplied by the unwinding unit 5 for wrapping pallet P during one revolution remains constant throughout the entire rotation. The film requirement per revolution corresponds to the circumference of pallet P or the circumference of the assembly formed by the items arranged on pallet P. Because the film requirement is constant along the circulation path U, the film web FB can be supplied at a constant feed rate during one revolution around pallet P, while simultaneously maintaining a substantially constant film tension.

[0068] In contrast, Figure 4 schematically shows a pallet P with a rectangular base being wrapped with a film web FB in a top view. Here, too, the orbit U of the unwinding unit 5 is marked by a circular path. Due to the rectangular base of the pallet P, the distance between the edges of the pallet P and the orbit U is not constant around the entire circumference. The corners of the pallet P are closer to the orbit U than the midpoints of the pallet's sides. If the film web FB is fed into the unwinding unit 5 at a constant feed rate, the applied film tension changes during one revolution of the unwinding unit 5 around the pallet P, with the film tension being greatest in the region of the pallet's corners.To ensure constant film tension, the film web FB must be supplied more quickly by the unwinding unit 5 when a corner of the pallet is wrapped. The supply speed must be reduced when a side of the pallet P is also wrapped. However, even with a rectangular pallet P, the total film requirement per revolution is determined by the pallet's circumference and is therefore constant.

[0069] Figure 5 shows a flowchart of an embodiment of a control routine for maintaining a predefined film tension in an unwinding unit 5. The control routine can be executed, for example, by a control unit 8 of a system 100. The control routine can, for example, comprise the following steps a) to f), whereby individual steps that are not essential for the operation of the control routine can be omitted or replaced by equivalent steps. Likewise, several steps can be combined into one step.

[0070] In step a), the motor frequency of motor 10 is determined. Based on the motor frequency, the rotational speed of motor 10 is determined in step b), for example, in RPM. In step c), the rotational speed of the winding arm 4 is determined based on the rotational speed of motor 10. From this, in step d), the time required for the unwinding unit 5, attached to the winding arm 4, to complete one full rotation around the pallet P can be determined.

[0071] Between steps d) and e), a user input B is read by the control routine, which describes the geometry of the palette P, i.e., for example, the perimeter of the palette P and, optionally, the shape or base area of ​​the palette P.

[0072] In step e), taking into account the geometry of the first roller R1, the speed at which the first roller R1 must rotate is calculated so that a sufficient quantity of film is supplied to wrap the pallet P with film under the specified film tension. For example, the circumference of roller R1 can be determined from its diameter and incorporated into the speed calculation. From the required rotational speed of roller R1, in step f), a roller motor speed is determined, for example, using a known gear ratio between roller R1 and the first roller motor 11. This motor speed is required to unwind the film spool F and wrap the film around the pallet P with the specified tension. The determined speed of the roller motor 11 is then applied.The control unit 8 sends a corresponding control signal to the roller motor 11, which causes the roller motor 11 to rotate at the determined speed.

[0073] By means of the control routine executable in the control unit 8, the speed of the roller motor 11 can be adjusted based on a motor frequency or motor speed of the motor 10 and based on the geometry of the pallet P, so that a predetermined value for the film tension can be maintained even when the rotational speed of the unwinding unit 5 changes, whereby the value for the film tension can, for example, be kept essentially constant.

[0074] System 100, particularly due to the control routine implemented in control unit 8, offers the advantage that the winding device 1 can be operated at different winding speeds, with the film tension reliably maintained at a predefined value at each winding speed. A winding device 1 therefore allows for flexible adaptation to different operating conditions of a packaging system by dynamically adjusting the winding speed, thereby achieving energy savings.

[0075] The invention has been described above using exemplary embodiments. It is understood that numerous modifications or adaptations are possible without departing from the underlying inventive concept. List of reference numerals

[0076] 1 winding device

[0077] 3 support frame

[0078] 4 winding arm

[0079] 4.1 horizontal arm section

[0080] 4.2 vertically running arm section

[0081] 5 unwinding unit

[0082] 6 coil chucks

[0083] 7 Role arrangement

[0084] 8 Control unit

[0085] 10 Motor of the winding arm

[0086] 11 first roller motor

[0087] 12 second roller motor

[0088] 13 gearboxes

[0089] 100 System

[0090] B User input

[0091] F foil spool

[0092] FB foil web

[0093] P pallets

[0094] RA axis of rotation

[0095] R1 first role

[0096] R2 second role

[0097] S signal connection

[0098] U orbit of the unwinding unit

Claims

Patent claims 1. System (100) for wrapping pallets (P) loaded with articles with a film that can be peeled from a film spool (F), comprising a winding device (1), wherein the winding device (1) has at least one support frame (3) with a winding arm (4) rotatably arranged thereon about a pivot axis (RA) and having an unwinding unit (5), wherein the winding arm (4) is driveable via a controllable and / or adjustable motor (10) connected to a control unit (8) of the system (100), wherein the unwinding unit (5) of the rotatable winding arm (4) has at least one spool chuck (6) for supporting the film spool (F) and at least one roller arrangement (7) with at least one first roller (R1) and a second roller (R2) for guiding and tensioning the film, wherein at least the first roller (R1) is driven by means of at least one controllable and / or adjustable first roller motor connected to the control unit (8) of the system (100). (11) is propellable, - where a motor speed of the motor (10) is recorded, - wherein the film requirement per revolution of the wrapping arm (4) is determined depending on the circumference of the loaded pallet (P) to be wrapped, - wherein, depending on the detected motor speed of the motor (10) and the film requirement per revolution of the winding arm (4), a speed of the first roller motor (11) is adjusted by means of a control routine executed in the control unit (8) such that a predefined film tension is maintained.

2. System (100) according to claim 1 , characterized in that a motor frequency is determined to detect the motor speed of the motor (10) and a rotational speed of the motor (10) is determined from this by means of the control routine executed in the control unit (8).

3. System (100) according to claim 2, characterized in that a number of revolutions of the winding arm (4) and / or a time period for one revolution of the winding arm (4) is determined from the rotational speed of the motor (10) by means of the control routine executed in the control unit (8).

4. System (100) according to one of the preceding claims, characterized in that, for adjusting the speed of the first roller motor (11), the control routine executed in the control unit (8) further takes into account the circumference of the first and / or second roller (R1 , R2).

5. System (100) according to one of the preceding claims, characterized in that the second roller (R2) can be driven by means of a second roller motor (12) connected to the control unit (8) of the system (100) which can be controlled and / or regulated.

6. System (100) according to claim 5, characterized in that the first and the second roller motor (11 , 12) can be operated independently of each other.

7. System (100) according to one of claims 1 to 4, characterized in that the first and second rollers (R1 , R2) are mechanically coupled and can be driven jointly via the first roller motor (11 ).

8. System (100) according to one of the preceding claims, characterized in that a definable pre-stretch of the film in the roll arrangement can be set by means of the control routine executed in the control unit (8).

9. System (100) according to claim 8, characterized in that, for setting the definable pre-stretch, the first roller (R1 ) and the second roller (R2) are driven with different rotational speeds, wherein the first roller (R1 ) and the second roller (R2) in particular have an identical diameter.

10. System (100) according to claim 9, characterized in that for a pre-stretch of the film of 100% the first roller (R1 ) is driven at twice the speed of the second roller (R2), or that for a pre-stretch of the film of 200% the first roller (R1 ) is driven at three times the speed of the second roller (R2) is driven, or that for a pre-stretch of the film of 300% the first roller (R1) is driven at four times the speed of the second roller (R2).

11. System (100) according to one of the preceding claims, characterized in that, by means of the control routine executed in the control unit (8), a film requirement per unit of time is determined from the determined film requirement per revolution of the winding arm (4) and a feed rate of the film dispensed by the unwinding unit (5) is set, wherein the feed rate is lower, in particular about 20% lower, than the film requirement per unit of time.

12. System (100) according to one of the preceding claims, characterized in that the predefined foil tension is a constant value or a constant range of values.

13. System (100) according to one of the preceding claims, characterized in that the film used is a stretch film made of a thermoplastic material, in particular polyethylene, wherein the film has a thickness in a range between 8 pm and 40 pm.

14. System (100) according to one of the preceding claims, characterized in that the unwinding unit (5) provided on a vertically extending arm section of the winding arm (4) is arranged to be movable upwards and downwards on the vertically extending arm section and is in particular movable in a vertical direction by means of a controllable and / or adjustable drive connected to the control unit (8) of the system (100).

Images