Device and method for controlling a tensile stress of a packaging material and packaging machine

Abstract

The invention relates to a device (1) for controlling a tensile stress of a packaging means in a packaging machine, comprising a clamping device (2) with two clamping elements (3, 3') arranged at a distance from one another, with the packaging means being guided therebetween, at least one actuator (7), and a control unit, wherein a position of at least one of the two clamping elements (3, 3') can be changed by the at least one actuator (7) based on a control signal from the control unit - while changing the distance between the two clamping elements (3, 3') - such that a clamping force acting on the packaging means with at least one of the two clamping elements (3, 3') can be controlled. Furthermore, a packaging machine for packaging a product with a packaging means and a method for controlling a tensile stress of a packaging means in a packaging machine are specified.

Description

[0001] The invention relates to a device for controlling a tensile stress of a packaging means in a packaging machine, comprising a clamping device with two clamping elements arranged at a distance from one another, wherein the packaging means is guided therebetween, at least one actuator and a control unit.

[0002] The present invention also relates to a packaging machine for packaging a product with a packaging means comprising such a device. Furthermore, the invention relates to a method for controlling the tensile stress of a packaging means in a packaging machine with such a device.

[0003] Packaging machines are used for the automated packaging of various goods using a packaging material. Such a packaging machine can be designed as a tying machine and comprise a positioning device for positioning the goods, a wrapping device for guiding the packaging material, such as a cord or thread, around the goods, and a knotting device for knotting the packaging material. In order for the packaging material to fit sufficiently tightly against the goods after packaging or tying, it may be necessary to provide a sufficiently high tensile stress on the packaging material during the packaging or tying process. For this purpose, the packaging machine can have a device for controlling the tensile stress, which slows down the pulling of the packaging material from the packaging material supply by the wrapping device.

[0004] Devices for controlling the tensile stress of a packaging material in a packaging machine have been known in practice for years.

[0005] For example, a device for packing, in particular tying, sheaves of grain with a string is already known from GB 1898 24,658 A. To slow down the string's retraction, the string provided from a string supply is clamped between a plate and a counterpart and pulled through during the tying process. The counterpart can be provided in the form of a rib or a flange on a frame structure of the device. Using a screw and a spring element arranged thereon, the desired clamping force acting on the plate can be manually adjusted. A wing nut is arranged on the screw for this purpose.

[0006] The desired tension of the packaging material depends in particular on the clamping force to be adjusted, the nature of the packaging material itself, and the goods to be packaged. The problem with existing devices is that the tension of the packaging material must be manually adjusted each time the goods or packaging material are changed, which is time-consuming. This can result in significant variations in the clamping forces or the tension of the packaging material.

[0007] The present invention is therefore based on the object of designing and developing a device of the type mentioned above in such a way that reliable adjustment of the tensile stress of the packaging material is ensured using simple structural means. Furthermore, a corresponding method for controlling the tensile stress of the packaging material and a corresponding packaging machine for packaging a product are to be specified.

[0008] According to the invention, the above object is achieved by a device for controlling a tensile stress of a packaging material in a packaging machine having the features of claim 1 and by a packaging machine having the features of claim 12. Furthermore, the above object is achieved by a method for controlling a tensile stress of a packaging material in a packaging machine having the features of claim 13.

[0009] According to this, the device comprises a clamping device with two clamping elements arranged at a distance from one another, wherein the packaging means is guided therebetween, at least one actuator and a control unit, wherein a position of at least one of the two clamping elements can be changed by the at least one actuator based on an actuating signal from the control unit - by changing the distance between the two clamping elements - in such a way that a clamping force acting on the packaging means with at least one of the two clamping elements can be controlled.

[0010] The packaging machine according to the invention for packaging a product with a packaging means comprises a device according to the invention.

[0011] The method according to the invention for controlling a tensile stress of a packaging material in a packaging machine with such a device comprises the steps: - transmitting at least one control signal by the control unit to the at least one actuator and - Changing the position of at least one of the two clamping elements and / or the actuating element by the at least one actuator based on the at least one actuating signal.

[0012] According to the invention, it was first recognized that the position of at least one of the two clamping elements can be reliably adjusted with high accuracy and reproducibility based on an actuating signal by means of the at least one actuator and the control unit. The actuating signal is assigned directly or indirectly to the position of at least one of the two clamping elements. The position can, in particular, represent a position specified by an operator. Since the position of at least one of the two clamping elements correlates with the clamping force or tensile stress of the packaging material, reliable and precise control of the clamping force or tensile stress of the packaging material is thus also possible.

[0013] The term “packaging material” is to be understood in the broadest sense within the scope of the present disclosure and includes binding materials such as cords, threads, cords, twines and yarns with any material composition, further includes strapping and banding materials such as plastic, paper, textile and metal bands, and includes flat packaging materials such as plastic and metal foils, paper and textile in roll form.

[0014] The term “control signal” is to be understood in the broadest sense within the scope of the present disclosure and relates to an electrical signal, wherein the electrical signal can be generated by the control unit and transmitted to the at least one actuator.

[0015] The term "actuator" is to be understood in the broadest sense within the scope of the present disclosure and refers to a device that converts an electrical signal or the control signal into a mechanical movement. In particular, the at least one actuator can be operated electrically, pneumatically, or hydraulically. Furthermore, the at least one actuator can comprise a linear actuator and / or a rotary actuator, wherein a linear movement, in particular along a straight line, can be generated using a linear actuator, and a rotary movement, in particular along a circular or elliptical path, can be generated using a rotary actuator.

[0016] The term "clamping force" is to be understood in the broadest sense within the scope of the present disclosure and refers to a force exerted on the packaging material by at least one of the two clamping elements, thereby having a braking effect when the packaging material is pulled forward during a packaging process. The braking effect is caused by frictional forces that depend on the surface quality of the clamping elements and the strength of the clamping force. A distinction can be made between two operating states: one in which the packaging material rests against only one of the two clamping elements, and one in which the packaging material rests against both clamping elements. In both cases, frictional forces are generated; if both clamping elements are in contact with the packaging material, a greater clamping force can be exerted on the packaging material.

[0017] The control unit can be connected to the at least one actuator via a physical line, such as a wired line, for exchanging, i.e., transmitting and receiving, data. Alternatively or additionally, it is conceivable for the control unit and the at least one actuator to be configured in such a way that an exchange of data is possible via wireless communication means, such as Bluetooth or WLAN.

[0018] The packaging machine can be designed in particular as a tying machine for tying a product with a packaging material, preferably a binding agent.

[0019] Consequently, the device according to the invention, the packaging machine according to the invention and the method according to the invention provide a device, a packaging machine and a method according to which a reliable adjustment of the tensile stress of the packaging means is ensured using structurally simple means.

[0020] Advantageously, at least one of the two clamping elements can be arranged to be linearly displaceable and / or pivotable to change its position. For this purpose, the device can have a suitable guide. This allows for a particularly simple construction that enables the clamping force or tensile stress to be controlled with high precision.

[0021] In a further advantageous manner, the at least one actuator can have a spindle drive and / or an electric motor for changing the position of at least one of the two clamping elements. The spindle drive can have a spindle, wherein the spindle can be designed as a threaded shaft. A spindle drive has, in particular, high positioning and repeatability accuracy and high drive rigidity, whereby the tensile stress of the packaging material can be controlled with high precision. Furthermore, large feed forces and thus high clamping forces can be realized with a spindle drive. An electric motor is easy to integrate into the device, cost-effective, and has high control accuracy.

[0022] It is further conceivable for the at least one actuator to have a movable actuating element, wherein the position of at least one of the two clamping elements can be changed directly or indirectly by the actuating element. In other words, the position of at least one of the two clamping elements can be changed directly or indirectly by a change in the position of the actuating element. It should be noted that the device can have a plurality of actuating elements, wherein one actuating element can be assigned to each actuator. The actuating element enables greater flexibility in the structural design of the device. The actuating element can represent a structural component of the at least one actuator, wherein the position of the actuating element can be changed directly by the drive of the at least one actuator, for example by the spindle drive.The actuating element itself can be directly or indirectly operatively connected to at least one of the two clamping elements. In particular, it is conceivable for the actuating element to be indirectly operatively connected to at least one of the two clamping elements for transmitting forces and / or torques via a mechanical transmission of any kind. The mechanical transmission can be designed in such a way that certain definable value ranges of the clamping force can be controlled with high precision.

[0023] According to an advantageous development, a spring element can be arranged between the actuating element and at least one of the two clamping elements, wherein a spring force acting parallel to the clamping force can preferably be exerted on at least one of the two clamping elements by the spring element. Thus, the position of at least one of the two clamping elements can be changed indirectly by the actuating element, wherein a mechanical transmission in the form of a spring element is arranged. The spring element makes it possible to control the position of at least one of the two clamping elements or the clamping force with a high degree of precision. This is because a displacement of the actuating element causes a smaller displacement of at least one of the two clamping elements due to the interposed spring.

[0024] In a further advantageous manner, the adjusting element can be arranged so that it can be linearly displaced and / or pivoted. For this purpose, the device can have a suitable guide. This allows for a particularly simple construction that enables the clamping force or tensile stress to be controlled with high precision.

[0025] It is also conceivable for a linear guide associated with the adjusting element to be arranged on at least one of the two clamping elements. This ensures that the adjusting element and the corresponding clamping element can be reliably displaced linearly relative to one another and that displacement in a transverse direction can be prevented.

[0026] According to an advantageous development, the at least one actuator can have a position sensor, in particular an inductive proximity switch, for detecting the position of at least one of the two clamping elements and / or the actuating element. This allows the position to be reliably determined, thereby increasing the positioning accuracy of one of the two clamping elements and / or the actuating element. A proximity switch makes it possible to detect when a limit position of one of the two clamping elements and / or the actuating element has been reached, which, for example, corresponds to a minimum or maximum travel path of the drive. Upon reaching the limit position, the drive can be switched off, thus preventing damage to the device due to a collision or overload.

[0027] In a further advantageous manner, at least one of the two clamping elements can have a flat clamping surface. This enables reliable clamping of the packaging material between the two clamping elements.

[0028] In a further advantageous manner, a target position of at least one of the two clamping elements and / or the actuating element can be controlled depending on at least one of the following definable parameters: tensile stress of the packaging material, type of packaging material, property of the packaging material, goods to be packaged, property of the goods to be packaged. Depending on at least one of the parameters or parameter values, a specific target position or a setting value of the target position of at least one of the two clamping elements and / or the actuating element can thus be defined. This can significantly reduce the effort required to set the desired tensile stress of the packaging material after a change in the type of packaging material or the goods. In addition, a high level of reproducibility of the clamping force or tensile stress of the packaging material to be set can be achieved.It is also conceivable for the control unit to have a memory, wherein at least one setting value for the target position and at least one associated parameter value can be stored in the memory. It is also conceivable for at least one of the parameters and / or the position of at least one of the two clamping elements and / or the actuating element to be visualized, for example, via a display screen, to increase user-friendliness.

[0029] Furthermore, it is conceivable for the control unit to have an operating unit for manual operation of the control unit, wherein the position can preferably be adjusted in steps and / or continuously. This enables particularly simple and efficient operation of the device by the user.

[0030] According to an advantageous development, at least two control signals can be transmitted, wherein the at least two control signals are assigned to different positions of at least one of the two clamping elements and / or the control element during a packaging process. One of the advantages achieved is that a temporally variable tensile stress of the packaging material can be provided during the packaging process. The tensile stress of the packaging material can be specifically adapted to the goods to be packaged and / or to definable phases of the packaging process.

[0031] Further advantages and aspects of embodiments of the present invention are explained below by way of example: - With the aid of at least one actuator, the device can be controlled by a motor, whereby referencing can be carried out via the position sensor in the form of an inductive proximity switch, i.e. an initiator. - At least one of the parameters and / or the position of at least one of the two clamping elements and / or the actuating element (setting parameters) can be visualized for the customer. - The setting parameters are reproducible. It is conceivable that different, defined setting values ​​could be stored for product-specific tensile stresses of the packaging material and for different packaging materials. This allows for customized packaging. Furthermore, a high level of user-friendliness can be achieved through verified pre-assignment of the various packaging material tensile stresses. This standardization of machine quality in production makes it easy to ensure internal quality assurance. - By controlling the clamping device over time, a tensile stress profile can be provided during the packaging process. - Overall, adaptive control of the packaging material's tension is enabled. Feedback of the current setting parameters can be generated for the operator, who can feel the directly associated increase or decrease in tension on the goods or packaged goods even when the tension is adjusted.

[0032] There are now various possibilities for advantageously embodying and developing the teaching of the present invention. For this purpose, reference is made, on the one hand, to the claims subordinate to claim 1 and, on the other hand, to the following explanation of preferred embodiments of the invention with reference to the drawing. In conjunction with the explanation of the preferred embodiments of the invention with reference to the drawing, generally preferred embodiments and developments of the teaching are also explained. The drawing shows: Fig. 1 in a schematic representation with a spatial view of a device according to an embodiment of the present invention, Fig. 2 in a further schematic representation with a spatial view of a device according to the embodiment in Fig. 1, Fig. 3 in a further schematic representation with a spatial view of a device according to the embodiment in Fig. 1, Fig. 4 shows a schematic, sectional view of a device according to the embodiment in Fig. 1 and Fig. 5 shows a schematic representation of steps of a method according to an embodiment of the present invention.

[0033] Fig. 1 shows a schematic representation with a spatial view of a device according to an embodiment of the present invention.

[0034] Fig. 2 shows in a further schematic representation with a spatial view a device according to the embodiment in Fig. 1.

[0035] Fig. 3 shows in a further schematic representation with a spatial view a device according to the embodiment in Fig. 1.

[0036] The Fig. 1, Fig. 2 and Fig. The device 1 shown in Figure 3 for controlling the tensile stress of a packaging material, in particular a binding material such as a cord, in a packaging machine comprises a clamping device 2 with two clamping elements 3, 3' arranged at a distance from one another. The clamping elements 3, 3' each have a flat clamping surface 4. The packaging material can be guided between the clamping elements 3, 3', although the packaging material is not shown in the figures. The clamping element 3 has a fastening section 5 for securing the device 1, in particular on and / or in a packaging machine. The fastening is effected using screws 6.

[0037] Furthermore, the device 1 has an actuator 7 and a control unit (not shown here). The control unit can be connected to the actuator 7 of the device 1 for data exchange via corresponding plug connections 8 arranged on the fastening section 5 (see in particular Fig. 2). The actuator 7 is secured to the clamping element 3 via screw connections 9, which has the fastening section 5.

[0038] The position of the clamping element 3' can be changed by the actuator 7 based on a control signal from the control unit—while changing the distance between the two clamping elements 3, 3'—in such a way that a clamping force acting on the packaging material with at least one of the two clamping elements 3, 3' can be controlled. The clamping element 3' is arranged to be linearly displaceable to change the position.

[0039] The actuator 7 has a spindle drive 10 with a spindle 11 and an electric motor 12 for changing the position of the clamping element 3'. The actuator 7 also has a movable adjusting element 13, wherein the position of the clamping element 3' can be changed indirectly by the adjusting element 13. A spring element 14 is arranged between the adjusting element 13 and the clamping element 3', wherein the spring element 14 can exert a spring force on the clamping element 3' acting parallel to the clamping force.

[0040] The adjusting element 13 is also arranged to be linearly displaceable, with a linear guide 15 with two guide rods 16 assigned to the adjusting element 13 being arranged on the clamping element 3'. The adjusting element 13 has two recesses 17 corresponding to the guide rods 16.

[0041] The actuator 7 has a position sensor 18 in the form of an inductive proximity switch (initiator) for detecting the position of the actuating element 13. Fig. 2 it can be seen that the position sensor 18 is fixed to the clamping element 3 via a mounting plate 19.

[0042] Using the device 1, a target position of the clamping element 3' and / or the actuating element 13 can be controlled depending on several definable parameters. The control unit has a memory, wherein at least one setting value of the target position and at least one associated parameter value can be stored in the memory.

[0043] Fig. 4 shows a schematic, sectional view of a device according to the embodiment in Fig. 1.

[0044] Out of Fig. 4 shows that the adjusting element 13 has a passage 20' for receiving the spindle 11 of the spindle drive 10. The passage 20' has an internal thread 22 corresponding to an external thread 21 of the spindle 11, so that the position of the adjusting element 13 can be changed by rotating the spindle 11 along it in a linear direction.

[0045] The clamping elements 3, 3' each have a passage 20'', 20''' for passing the spindle 11 through. Thus, the guided spindle 11 provides guidance for the clamping element 3', wherein the clamping element 3' is secured against displacement in a plane defined by the clamping surface 4.

[0046] The feedthroughs 20'', 20''' are not designed with internal threads, so that a direct change in the position of both clamping elements 3, 3' by the actuator 7 or the spindle 11 is not possible. Instead, a change in the position of the actuating element 13 or the clamping force is transmitted indirectly to the clamping element 3' via the spring element 14 arranged between the actuating element 13 and the clamping element 3'. The clamping force acts in a direction parallel to a longitudinal axis 23 of the spindle 11 and parallel to the spring force acting in the spring element 14. The magnitude of the spring force corresponds to the magnitude of the clamping force.

[0047] Fig. 5 shows a schematic representation of steps of a method according to an embodiment of the present invention.

[0048] In a first step S1, the user provides at least one parameter value, for example, a value for a desired tensile stress of the packaging material and a specific packaging material type. This can be done, for example, by entering the at least one parameter value into an input mask of an operating program, wherein the operating program can be implemented in the control unit itself or in a computer communicatively connected to the control unit.

[0049] In a step S2, the control unit can then access a position value stored in a memory for the position of at least one of the two clamping elements 3, 3' and / or the actuating element 13, which is associated with the input at least one parameter value. Alternatively, it is conceivable for the user to directly provide a desired position value for the position of at least one of the two clamping elements 3, 3' and / or the actuating element 13.

[0050] Subsequently, a control signal is transmitted by the control unit to the at least one actuator 7 (S3). The control signal corresponds to the position value of at least one of the two clamping elements 3, 3' and / or the control element 13 from step S2.

[0051] In step S4, the position of at least one of the two clamping elements 3, 3' and / or the actuating element 13 is changed by the at least one actuator 7 based on the actuating signal and the target position is approached.

[0052] With regard to further advantageous embodiments of the device according to the invention, the packaging machine according to the invention and the method according to the invention, reference is made to the general part of the description and to the appended claims in order to avoid repetition.

[0053] Finally, it should be expressly pointed out that the above-described embodiments of the device according to the invention, the packaging machine according to the invention and the method according to the invention serve only to explain the claimed teaching, but do not limit it to the embodiments. List of reference symbols 1 device 2 clamping device clamping element 4 clamping surface 5 Fastening section 3, 3' 6 screw 7 Actuator 8 plug connection 9 Screw connection 10 spindle drive 11 spindle 12 electric motor 13 Control element 14 Spring element 15 Linear guide 16 Guide rod 17 Deepening 18 Position sensor 19 Mounting plate 20', 20'', 20''' implementation 21 external threads 22 internal threads 23 Longitudinal axis of the spindle QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] GB 1898 24,658 A

[0005]

Claims

[1] Device (1) for controlling a tensile stress of a packaging means in a packaging machine, comprising a clamping device (2) with two clamping elements (3, 3') arranged at a distance from one another, the packaging means being guided therebetween, at least one actuator (7) and a control unit, wherein a position of at least one of the two clamping elements (3, 3') can be changed by the at least one actuator (7) based on a control signal from the control unit - by changing the distance between the two clamping elements (3, 3') - in such a way that a clamping force acting on the packaging means with at least one of the two clamping elements (3, 3') can be controlled. [2] Device (1) according to claim 1, characterized by that at least one of the two clamping elements (3, 3') is arranged to be linearly displaceable and / or pivotable in order to change the position. [3] Device (1) according to claim 1 or 2, characterized bythat the at least one actuator (7) has a spindle drive (10) and / or an electric motor (12) for changing the position of at least one of the two clamping elements (3, 3'). [4] Device (1) according to one of claims 1 to 3, characterized by that the at least one actuator (7) has a movable actuating element (13), wherein the position of at least one of the two clamping elements (3, 3') can be changed directly or indirectly by the actuating element (13). [5] Device (1) according to claim 4, characterized by that a spring element (14) is arranged between the adjusting element (13) and at least one of the two clamping elements (3, 3'), wherein preferably by the spring element (14) a spring force acting parallel to the clamping force can be exerted on at least one of the two clamping elements (3, 3'). [6] Device (1) according to claim 4 or 5, characterized by that the adjusting element (13) is arranged to be linearly displaceable and / or pivotable. [7] Device (1) according to one of claims 4 to 6, characterized by that a linear guide (15) associated with the actuating element (13) is arranged on at least one of the two clamping elements (3, 3'). [8] Device (1) according to one of claims 1 to 7, characterized by that the at least one actuator (7) has a position sensor (18), in particular an inductive proximity switch, for detecting the position of at least one of the two clamping elements (3, 3') and / or the actuating element (13). [9] Device (1) according to one of claims 1 to 8, characterized by that at least one of the two clamping elements (3, 3') has a flat clamping surface (4). [10] Device (1) according to one of claims 1 to 9, characterized bythat a target position of at least one of the two clamping elements (3, 3') and / or of the actuating element (13) can be controlled as a function of at least one of the following definable parameters: tensile stress of the packaging material, type of packaging material, property of the packaging material, goods to be packaged, property of the goods to be packaged. [11] Device (1) according to one of claims 1 to 10, characterized by that the control unit has an operating unit for manually operating the control unit, wherein the position is preferably adjustable in steps and / or continuously. [12] Packaging machine for packaging a product with a packaging means, comprising a device (1) according to one of claims 1 to 11. [13] Method for controlling a tensile stress of a packaging means in a packaging machine with a device (1) according to one of claims 1 to 11, comprising the steps: - transmitting (S2) at least one control signal by the control unit to the at least one actuator (7) and - Changing (S3) the position of at least one of the two clamping elements (3, 3') and / or the actuating element (13) by the at least one actuator (7) based on the at least one actuating signal. [14] Method according to claim 13, characterized by that at least two actuating signals are transmitted, wherein the at least two actuating signals are assigned to different positions of at least one of the two clamping elements (3, 3') and / or the actuating element (13) during a packaging process.

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