Folding device

Abstract

A folding device (1) for folding an end of a packaging material around a slurry bale, the folding device comprising: at least two folding arms (5a-d, 6a-b, 7a-d), each comprising at its end a contact element (8a-d; 9a; 10a-b) of a substrate (10a-b); at least two electric actuators (11a-d, 11a '-d', 12a-b, 12a '-b', 13a-b, 13a '-b', 14a-b, 14a '-b') each arranged to co-act with the one or more folding arms to displace its contact elements for contact with the packaging material to fold the packaging material around the edge of the pulp bale; and a control unit (15) arranged in electrical contact with the at least two electric actuators and arranged to determine, for each electric actuator, at least one operating parameter, including a position parameter and / or a force parameter and / or a speed parameter, the control unit is configured to control at least one electric actuator using the at least one operating parameter. A corresponding method is also provided.

Description

Technical Field

[0001] The invention relates to the field of folding devices for folding ends of a packaging material around a pulp bale, the packaging material being arranged around the periphery of the pulp bale and having a length greater than the length of the pulp bale so that the ends of the packaging material extend beyond the opposite ends of the pulp bale. Background Art

[0002] Folding devices for folding the ends of packaging material around pulp bales are known in the art. One example of such a folding device is the Valmet bale folder, which comprises a plurality of folding arms actuated by hydraulic actuators, which fold the packaging material around the edges of the pulp bale. Although such devices offer high performance and low cycle times, a disadvantage is the need to manually adjust the folding arms / hydraulic actuators, e.g. during servicing of the folding device or when a different bale size is to be used. This is time consuming and poses safety issues, as the operator needs to enter the safety zone of the folding device. Summary of the invention

[0003] An object of the present invention is to provide a folding device which at least partially solves or improves the above-mentioned problems.

[0004] These and other objects are achieved by the invention by means of a folding device according to the independent claims.

[0005] According to a first aspect of the invention, there is provided a folding apparatus for folding ends of a packaging material around a pulp bale when positioned at a bale folding region in the folding apparatus. The packaging material is arranged around the periphery of the pulp bale and has a length greater than the length of the pulp bale so that the ends of the packaging material extend beyond the opposite ends of the pulp bale. The folding apparatus comprises: at least two folding arms, each comprising a contact element at its end; at least two electric actuators, each arranged to cooperate with one or more of the folding arms to displace its contact element so as to contact the packaging material to fold the packaging material around the edge of the pulp bale; and a control unit arranged in electrical contact with the at least two electric actuators and arranged to determine at least one operating parameter for each electric actuator, the operating parameter comprising a position parameter associated with the position of one or more contact elements and / or a force parameter associated with or indicative of an actuator torque or force and / or a speed parameter associated with or indicative of a rotational or displacement speed of the electric actuator, wherein the control unit is configured to control at least one electric actuator using the at least one operating parameter.

[0006] In other words, the folding device comprises a bale folding area, which may also be referred to as a bale folding position, in which the pulp bale will be positioned when folding. The device also comprises at least two folding arms, which are preferably arranged at opposite sides of the bale folding area. The folding arms may be displaceable and / or rotatable, for example, they are rotatable in a sense about an axis of rotation or a ball joint, wherein the axis of rotation or the ball joint is optionally displaceable. At least one or each of the folding arms comprises a contact element, which may be arranged at or near its end. The contact element is suitable for contacting with the packaging material to fold the packaging material around the edge of the pulp bale. The device also comprises at least two electric actuators, for example one electric actuator per folding arm. Each electric actuator is arranged to act together with one or more folding arms to displace its contact element. The control unit is arranged to be in wired or wireless contact with at least two electric actuators to control them. The control unit is arranged to determine at least one operating parameter for at least one or each electric actuator, the operating parameter comprising a position parameter associated with the position of one or more contact elements and / or a force parameter indicating the torque or force of the actuator and / or a speed parameter indicating the rotation or displacement speed of the electric actuator. The control unit is configured to control at least one or each electric actuator using the at least one operating parameter, i.e. the control unit uses the at least one operating parameter to feedback control the electric actuator. It should be understood that the perimeter of the pulp bale refers to the perimeter in a plane substantially perpendicular to the length direction of the pulp bale. The pulp bale can be described in shape as a rectangular cuboid, wherein the packaging material extends around the perimeter to cover its long face (i.e. the longer side / face extending in the length direction of the pulp bale). It should be understood that the packaging material can be formed by one, two or more sheets of packaging material. The length of the packaging material is greater than the length of the pulp bale, so that not only the long face / side is covered, but also the end of the packaging material extends beyond the opposite end of the pulp bale. The contact elements may be described as being adapted to each contact an end of the wrapping material extending beyond the opposite end of the pulp bale to fold the ends of the wrapping material towards / onto the respective ends of the pulp bale.

[0007] The present invention is based on the insight of using an electric actuator instead of a hydraulic actuator, which allows or facilitates controlling the actuator based on at least one measured or determined operating parameter, such as position and / or actuator torque / force and / or speed. Such operating parameter-based control of the actuator, which may also be referred to as feedback control, may reduce or eliminate the need for manual adjustment of the folding arm. Another advantage of an electric actuator instead of a hydraulic actuator is reduced energy consumption, since the electric actuator consumes energy only when actuated. Another advantage is that cycle times may be shortened, since having a (precisely controllable) electric actuator and knowing the position of each contact element allows the electric actuator to be actuated in such a way that the contact elements precisely pass each other. Current hydraulic actuators require larger margins to avoid collisions between contact elements.

[0008] It is to be understood that the directions referred to herein are defined relative to the folding device, wherein the bale folding area is defined as horizontal. For example, lateral movement therefore refers to movement including movement in a horizontal direction.

[0009] In various embodiments, one or more of the at least two electric actuators each comprises an electric motor, wherein the control unit is configured to determine the position parameter using data obtained from one or more position sensors connected to the electric motor and / or to the folding arm connected thereto. The position sensor(s) may be a pulse sensor(s) directly or indirectly connected to the shaft of the electric motor. Accurate knowledge of the position of the contact element provides several advantages. For example, when different bale sizes are to be used, the start and stop positions may be adjusted. In addition, the position of each actuator / contact element may also be monitored during operation of the device and used for feedback control.

[0010] In various embodiments, the electric motor is connected to the corresponding folding arm via a gearbox for rotating the folding arm. For example, the folding arm rotates around a rotation axis that coincides with the output shaft of the gearbox.

[0011] In other embodiments, the electric motor forms part of a mechanical linear actuator connected to a corresponding folding arm.The mechanical linear actuator may be a screw actuator, such as a moving nut linear actuator.

[0012] In various embodiments, at least one or each of the electric motors is controlled using a variable frequency drive (VFD) controller, which may also be referred to as an inverter.

[0013] In various embodiments, the control unit is configured to determine at least one target displacement parameter of one or more of the electric actuators. The folding device may also include a human-machine interface HMI arranged to communicate with the control unit, wherein the HMI is configured to receive a user input including at least one target displacement parameter or a user input indicating the target displacement parameter, and transmit one or more signals indicating the user input to the control unit, and wherein the control unit is configured to determine at least one target displacement parameter using one or more signals. At least one target displacement parameter may be one or more of a starting position (starting position of a contact element or actuator member), an end position (end position of a contact element or actuator member), a rotation speed (rotation speed of a folding arm or electric motor shaft), a displacement speed (displacement speed of a folding arm or linear actuator), an actuator torque, and an actuator force. The target displacement parameter may also be referred to as a target parameter value, such as a target starting position and an end position, a target speed / torque / force, etc. The HMI may be a device that communicates with the control unit by wire or wirelessly. Alternatively, the HMI may be software suitable for execution on a handheld device or a computer.

[0014] In various embodiments, the folding device comprises four folding arms which are arranged symmetrically around the bale folding region, for example at opposite corners of the bale folding region, wherein a corresponding electric actuator of each of the four folding arms is arranged to co-act therewith, such that contact elements of the four folding arms are displaceable into the bale folding region independently of one another to contact the packaging material at corresponding edges of the pulp bale. The four folding arms are preferably displaceable laterally into the bale folding region, i.e. displaceable in a substantially horizontal plane. It will be appreciated that, although a corresponding electric actuator of each of the four folding arms is arranged to co-act therewith, it is also foreseeable to provide one or more additional electric actuators, each co-acting with one or more of the four folding arms.

[0015] In various embodiments, the control unit is configured to determine whether the pulp bale is misaligned based on at least one operating parameter of each electric actuator cooperating with the four folding arms, and if so, to control at least one of the electric actuators cooperating with the four folding arms in response to the misalignment. The control unit may be configured to determine whether the pulp bale is misaligned by comparing the at least one operating parameter with a corresponding target displacement parameter (or maximum value) of each electric actuator cooperating with the four folding arms. For example, the position parameter (operating parameter) of each actuator / contact element may be compared with the corresponding end position (target displacement parameter), and if, for example, two of the position parameters are within a predetermined interval from the corresponding end position, while the other two position parameters are outside the interval, it may be determined that the pulp bale is misaligned. Alternatively or additionally, a force parameter (operating parameter) indicative of an actuator torque may be compared to a corresponding (target) actuator torque (target displacement parameter) or a predetermined (or user-adjustable via the HMI) maximum torque, and if, for example, two of the force parameters differ from the corresponding actuator torque by less than a predetermined amount, while the other two force parameters differ by a greater amount, then it may be determined that the pulp bale is misaligned. In response to a determination that the pulp bale is misaligned, various control actions are possible. For example, if the force parameters indicative of the actuator torques of two diagonally opposed actuators have reached their corresponding actuator torques, but have not yet reached their corresponding end positions, then the control unit may attempt to align the pulp bale by further increasing the torques of the two actuators until the end positions are reached.

[0016] In various embodiments, two lower folding arms or two groups of lower folding arms are symmetrically arranged at opposite sides of the bale folding area, wherein, for each of the two lower folding arms or groups of lower folding arms, at least one electric actuator is arranged to cooperate therewith so that the contact element(s) connected thereto are vertically displaceable from below towards the bale folding area (and above the bale folding area) to contact the packaging material at the corresponding lower edge of the pulp bale.

[0017] In various embodiments, two upper folding arms or two groups of upper folding arms are symmetrically arranged at opposite sides of the bale folding area, wherein, for each of the two upper folding arms or groups of upper folding arms, at least one electric actuator is arranged to cooperate therewith so that the contact element(s) connected thereto are vertically displaceable from above towards the bale folding area to contact the packaging material at the corresponding upper edge of the pulp bale.

[0018] It should be understood that the contact elements of the lower and upper folding arms are not necessarily displaceable only in a vertical direction, such as along a plumb line. For example, the folding arms are usually rotatable about a rotation axis at their ends, which means that the contact elements connected thereto are displaced along a curved path, i.e. not only in a vertical direction.

[0019] In various embodiments, a rotating device, which may also be referred to as a turntable, is arranged at the pulp folding area and comprises a rotatable contact member adapted to engage with the pulp bale to rotate the pulp bale, for example, 90 degrees, when positioned at the pulp bale folding area. The rotating device may comprise one or more electric, pneumatic or hydraulic actuators to rotate the contact member. The one or more actuators are advantageously electrically connected directly or indirectly to a control unit to control them.

[0020] In various embodiments, for each of the two lower or upper folding arms or folding arm groups, at least one electric actuator is arranged to cooperate therewith so that the contact element is laterally displaceable, wherein the control unit is configured to, before controlling the rotation device to rotate the pulp bale to a position in which the ends of the packaging material face the two folding arms, control the electric actuators cooperating with the two folding arms or folding arm groups to:

[0021] - displacing (raising or lowering) the contact element to a vertical level above the bale folding area (vertical level below the height of the pulp bale), and then

[0022] - Displacing the contact elements of the two folding arms towards each other to push the opposite sides of the pulp bale until a target position is reached, which target position is determined according to the pulp bale size.

[0023] According to a second aspect of the invention, there is provided a method of controlling an electric actuator of a folding device for folding an end of a packaging material around a pulp bale, the folding device comprising: at least two folding arms, each comprising a contact element at an end thereof; and at least two electric actuators, each arranged to cooperate with one or more of the folding arms to displace its contact element into contact with the packaging material, thereby folding the packaging material around an edge of the pulp bale,

[0024] The method includes:

[0025] - for each electric actuator, determining at least one operating parameter, the operating parameter comprising a position parameter associated with the position of one or more contact elements and / or a force parameter indicative of an actuator force or torque and / or a position or velocity parameter indicative of a position or velocity of the actuator or of the folding arm;

[0026] - controlling at least two electric actuators using said at least one operating parameter.

[0027] In various embodiments of the method according to the second aspect of the invention, the method further comprises determining at least one target displacement parameter of one or more (or each) electric actuator by receiving a user input including at least one target displacement parameter or a user input indicating the parameter from the HMI. The at least one target displacement parameter may be one or more of a starting position (starting position of the contact element or actuator member), an end position (end position of the contact element or actuator member), a rotational speed (rotational speed of the folding arm or electric motor shaft), a displacement speed (displacement speed of the folding arm or linear actuator), an actuator torque and an actuator force.

[0028] In various embodiments of the method according to the second aspect of the invention, the method further comprises determining whether the pulp bale is misaligned and, if so, responding to the misalignment to at least one of the electric actuators cooperating with the four folding arms, wherein the determination of whether the pulp bale is misaligned is made by comparing at least one operating parameter with a corresponding target displacement parameter (or maximum value) of each electric actuator cooperating with the four folding arms.

[0029] According to a third aspect of the present invention, there is provided a data processing apparatus comprising means for executing the method according to the second aspect of the present invention or an embodiment thereof.

[0030] According to a fourth aspect of the present invention, there is provided a computer program product comprising instructions which, when executed by a computer, cause the computer to perform a method according to the second aspect of the present invention or an embodiment thereof.

[0031] According to a fourth aspect of the present invention, there is provided a computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to perform a method according to the second aspect of the present invention or an embodiment thereof.

[0032] The features of the above-described embodiments can be combined in any practical manner to form embodiments having these feature combinations. Further, all features and advantages of the embodiments described above with reference to the first aspect of the present invention can be applied to the corresponding embodiments of the second, third, fourth and fifth aspects of the present invention, and vice versa. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The above and other aspects of the present invention will now be described in more detail using the accompanying drawings, which show currently preferred embodiments of the present invention, in which:

[0034] Figure 1 An embodiment of a folding device according to the first aspect of the invention is shown;

[0035] Figure 2 Shown with Figure 1The same embodiment (without the control unit and HMI), and a schematic diagram of a pulp bale entering a folding device, and

[0036] Figure 3 Shows Figure 1 and 2 A detailed view of one side of the Fold device in the iPhone 7. DETAILED DESCRIPTION

[0037] Figure 1-3 An embodiment of a folding device according to the first aspect of the present invention is shown. The folding device 1 is configured to (see Figure 2 ) folds the ends of the packaging material 2 (e.g. 2a-d, corresponding ends being present at opposite ends of the pulp bale) around the pulp bale 3 when positioned at the bale folding area 4 in the folding apparatus. Figure 2 As shown, the wrapping material is arranged around the periphery of the pulp bale and has a length greater than the length of the pulp bale so that ends of the wrapping material (e.g. 2a-d) extend beyond opposite ends of the pulp bale (e.g. 3a). The folding device comprises folding arms 5a-d, 6a-b, 7a-d, each comprising a contact element 8a-d; 9a; 10a-b at its end.

[0038] The four folding arms 5a-d are arranged symmetrically around the bale folding area 4 at its opposite corners. A corresponding electric actuator (each comprising an electric motor 11a-d and a gearbox 11a'-d') of each of the four folding arms is arranged to rotate the folding arm so that the contact elements 8a-d of the four folding arms are laterally displaceable into the bale folding area independently of each other to contact the corresponding edge (e.g. 3", see Figure 2 ) is in contact with the packaging material. In other words, each contact element 8a-d is in contact with one end of the packaging material (e.g., 2a, 2c, see Figure 2 ) to fold this end towards / onto one end of the pulp bale (e.g. 3a). The contact elements 8a-d are connected to the respective folding arms 5a-d in a rotatable / pivotable manner about a rotation axis parallel to the rotation axis of the folding arms 5a-d. The spring is arranged for preloading the contact elements into the shown position. Assuming a horizontal arrangement of the folding device (wherein the bale folding area is horizontal), the mentioned rotation axis is substantially vertical.

[0039] The two lower folding arms 6a-b are symmetrically arranged at opposite sides of the bale folding area 4, wherein for each of the two lower folding arms, an electric actuator (each comprising an electric motor 12a-b and a gear box 12a'-b') is arranged to rotate the folding arms 6a-b so that a contact element (e.g. 9a, arm 6b comprises a corresponding contact element not shown in the figure) is vertically displaceable from below towards the bale folding area to contact a corresponding lower edge of the pulp bale (e.g. 3', see Figure 2 ). In other words, each contact element (e.g. 9a) contacts one end (e.g. 2d) of the packaging material to fold / fold this end towards / onto one end (e.g. 3a) of the pulp bale. The contact element (e.g. 9a) is connected to the corresponding folding arm 6a-b in a rotatable / pivotable manner about a rotation axis parallel to the rotation axis of the folding arms 6a-b. The spring is arranged for preloading the contact element into the shown position, as shown. Figure 3 Assuming a horizontal arrangement of the folding device (with the bale folding area being horizontal), the mentioned axis of rotation is essentially horizontal.

[0040] Two sets of upper folding arms 7a-b, 7c-d are symmetrically arranged at opposite sides of the bale folding area, wherein, for each of the two sets of upper folding arms, one electric actuator (each comprising an electric motor 13a-b and a gear box 13a'-b') is arranged to rotate the folding arm so that the contact elements 10a-b connected thereto are vertically displaceable from above toward the bale folding area to contact the packaging material at the corresponding upper edge of the pulp bale. In other words, each contact element (10a, 10b) contacts one end (e.g. 2b) of the packaging material to fold the end toward / onto one end (e.g. 3a) of the pulp bale.

[0041] The folding apparatus further comprises a rotating device 17 which is arranged to engage with the pulp bale 3 when positioned at the bale folding area 4 to rotate said pulp bale.

[0042] The folding apparatus further comprises a conveying arrangement comprising two chains 18a-b arranged to convey the pulp bales from an inlet of the folding apparatus to a bale folding area and further to an outlet of the folding apparatus. Figure 2 In the video, bales can be seen at the entrance to the folding equipment.

[0043] The four folding arms are connected in pairs with a lower folding arm and an upper folding arm at opposite sides of the bale folding area to the sliding device (e.g. 19a-b, see Figure 3 The slides are displaceable towards and away from each other by means of respective electric actuators (13a-a', 14a-a') in electrical contact with the control unit. Figure 3As shown, the electric motor 14a is coupled to the slide via a rack and pinion arrangement to convert the rotational movement of the motor into a linear movement of the slide. Thus, when the corresponding electric actuator of the slide is actuated, the rotation axis of the folding arm connected thereto is displaced towards or away from the bale folding area (laterally). By actuating the electric actuator of the corresponding folding arm, it is further rotated to achieve a lateral or vertical displacement of its contact element.

[0044] A control unit 15 is arranged in electrical contact with each electric motor 11a-b, 12a-b, 13a-b, 14a-b (the motors located on one side of the device are indicated by dashed lines). The control unit is arranged to determine three operating parameters for each electric actuator: a position parameter (associated with the position of the contact element affected by the actuator), a force parameter indicative of the torque of the electric motor and a speed parameter indicative of the rotational speed of the electric motor. The control unit is configured to control the electric motor / actuator using the operating parameters.

[0045] The control unit 15 is configured to determine position and speed parameters using data obtained from the position sensor, which is a pulse sensor connected to the shaft of the respective electric motor. The force parameter is determined using the current output to the respective electric motor, which current is known by the control unit.

[0046] The rotating device 17 is pneumatically driven (not shown in the figure), and the pneumatic drive is also electrically controlled by the control unit 15.

[0047] The folding device also includes a human machine interface HMI 16, which is in electrical communication with the control unit. The control unit 15 is configured to determine the target displacement parameters of each electric actuator: the starting and ending positions of its contact elements, the rotation speed and the motor torque. The HMI is configured to receive a user input indicating the displacement parameters and transmit a signal indicating the user input to the control unit. The control unit is configured to use the signal to determine the target displacement parameters.

[0048] When the pulp bale enters the folding device, it usually enters with its long side parallel to the conveying arrangement, such as Figure 2. When the pulp bale has been delivered to the center of the bale folding area 4, with its center at the rotating device 17, an optional alignment procedure can be performed. In this procedure, the control unit 15 commands the electric motors 12a-b to raise the contact elements of the two lower folding arms 6a-b and the contact elements connected thereto (e.g. 9a) to a vertical level above the bale folding area, and then controls the electric motors 14a-b to displace the slides so that the contact elements of the two lower folding arms are displaced toward each other to push the opposite sides of the pulp bale (to align the pulp bale) until a target position is reached, which target position is determined based on the pulp bale size. The alignment procedure is completed by controlling the electric motors 12a-b and 14a-b to return to their previous positions. Afterwards, the control unit 15 controls the rotating device 17 to rotate the pulp bale 90 degrees so that the ends of the packaging material face both sides. Afterwards, the control unit controls the electric motors 14a, 14b to displace the slide towards the pulp bale, and then activates the electric motors 11a-d to displace the contact elements 8a-d laterally, i.e. in a substantially horizontal plane, to contact the packaging material, thereby folding it around the upright edge (e.g. 3") of the pulp bale. Afterwards, the electric motors 12a-b are controlled to displace the lower contact element (e.g. 9a) upwards along a curved path (defined by the length of the folding arms) to contact the packaging material, thereby folding it around the corresponding lower edge (e.g. 3'). When the contact elements 8a-d, 9a come into contact with the packaging material, they pivot about their rotation axis (against the preload of the spring). Afterwards, the electric motors 13-ab are controlled to displace the upper contact elements 10a, 10b downwards along a curved path to come into contact with the packaging material, thereby folding it around the respective upper edge of the pulp bale. Finally, the electric motors 14a, b are controlled again to displace the slide away from the pulp bale, and the finished pulp bale with the folded packaging material is conveyed out of the folding device using the conveying arrangement 18a-b.

[0049] While controlling the corresponding electric motors, the control unit repeatedly determines the operating parameters (position, speed and force) and repeatedly compares the operating parameters with target displacement parameters and / or limit values ​​such as maximum torque. For example, when it is determined that the position parameters of the electric actuator are within a predetermined interval from the end position, the control unit stops the movement. In addition, the control unit can be configured to determine whether the pulp bale is misaligned, for example by comparing the position parameters (operating parameters) of the contact elements 8a-d with the corresponding end positions (target displacement parameters), and if, for example, two of the position parameters are within a predetermined interval from the corresponding end position, while the other two position parameters are outside the interval, it can be determined that the pulp bale is misaligned. In response to the determination that the pulp bale is misaligned, various control actions can be taken. For example, if the force parameters indicating the actuator torques of two diagonally opposite actuators have reached the corresponding actuator torques, but have not yet reached their corresponding end positions, the control unit can attempt to align the pulp bale by further increasing the torques of the two actuators until the end position is reached. Alternatively, all actuators may be controlled back to their initial positions and the slurry rotated back 90 degrees and the alignment procedure described above may then be performed.

[0050] The above description and the accompanying drawings should be regarded as non-limiting examples of the present invention. Those skilled in the art recognize that several changes and modifications may be made within the scope of the present invention. In particular, although a total of four folding arms and contact elements are provided at each side of the folding device, it is foreseeable within the scope of the present invention that fewer folding arms may be used. For example, the upper folding arm 6a and the lower folding arm 10a may be replaced by a single folding arm, the axis of rotation of which is vertically displaceable using an additional movable actuator, so that the packaging material can be folded around the upper and lower edges. Correspondingly, the folding arms 5a, 5b may be replaced by a single folding arm. Further, the sliding device and the corresponding actuator may be omitted. Furthermore, by selecting a starting position of the contact elements 8b, 8d with larger spacing, the folding device may be arranged to receive a contact with the upper and lower edges at its entrance. Figure 2 . In such an embodiment, the rotation device can be omitted. Furthermore, the control unit can be configured to determine less than three operating parameters, such as only position parameters. Furthermore, the above-mentioned springs for preloading the contact elements can be replaced by pneumatic cylinders or other devices with corresponding functions. Furthermore, although the sliding device is shown as comprising wheels rolling in a track / profile to allow its displacement, different arrangements are also feasible, such as comprising sliding blocks.

Claims

1. A folding device (1) for folding ends (2a-d) of a packaging material (2) around a pulp bale (3) when positioned at a bale folding area (4) in the folding device, the packaging material being arranged around the periphery of the pulp bale and having a length greater than the length of the pulp bale so that the ends (2a-d) of the packaging material extend beyond the opposite ends (3a) of the pulp bale, The folding device include: - at least two folding arms (5a-d, 6a-b, 7a-d), each comprising a contact element (8a-d; 9a; 10a-b); at least two electric actuators (11a-d, 11a'-d', 12a-b, 12a'-b', 13a-b, 13a'-b', 14a-b, 14a'-b'), each arranged to cooperate with one or more of the folding arms to displace a contact element thereof so as to come into contact with the packaging material to fold the packaging material around an edge (3', 3") of the pulp bale; - a control unit (15), which is in electrical contact with the at least two electric actuators and is arranged to determine at least one operating parameter for each electric actuator, the operating parameter comprising a position parameter associated with the position of one or more contact elements and / or a force parameter indicating an actuator torque or force and / or a speed parameter indicating a rotational or displacement speed of the electric actuator, wherein the control unit is configured to control the at least two electric actuators using the at least one operating parameter.

2. The folding device according to claim 1, It is characterized in that One or more of the at least two electric actuators each comprises an electric motor (11a-d, 12a-b, 13a-b, 14a-b), wherein the control unit (15) is configured to determine the position parameters using data obtained from one or more position sensors connected to the electric motor and / or the folding arm connected thereto.

3. The folding device according to claim 2, It is characterized in that The electric motors are connected to corresponding folding arms via gearboxes (11a'-d', 12a'-b', 13a'-b', 14a'-b') for rotation of the folding arms.

4. The folding device according to claim 2, It is characterized in that The electric motor forms part of a mechanical linear actuator connected to a corresponding folding arm.

5. Folding device according to any one of the preceding claims, It is characterized in that The control unit (15) is configured to determine at least one target displacement parameter of one or more of the electric actuators, and wherein the folding device further comprises a human-machine interface (HMI) (16) arranged to communicate with the control unit, wherein the HMI is configured to receive a user input including the at least one target displacement parameter or a user input indicating the target displacement parameter, and transmit one or more signals indicating the user input to the control unit, and wherein the control unit is configured to determine the at least one target displacement parameter using the one or more signals.

6. The folding device according to claim 5, It is characterized in that The at least one target displacement parameter includes at least one of a starting position, an ending position, a rotational speed, a displacement speed, an actuator torque, and an actuator force.

7. Folding device according to any one of the preceding claims, It is characterized in that The invention comprises four folding arms (5a-d) which are symmetrically arranged around the bale folding area (4), wherein a corresponding electric actuator (11a-d, 11a'-d') of each of the four folding arms is arranged to cooperate therewith so that contact elements (8a-d) of the four folding arms are laterally displaceable into the bale folding area independently of each other to contact the packaging material at a corresponding edge (3") of the pulp bale.

8. The folding device according to claim 7, It is characterized in that The control unit (15) is configured to determine whether the pulp bale (3) is misaligned based on at least one operating parameter of each electric actuator (11a-d, 11a'-d') cooperating with the four folding arms (5a-d), and if so, to control at least one of the electric actuators cooperating with the four folding arms in response to the misalignment.

9. The folding device according to claim 8, It is characterized in that The control unit (15) is configured to determine whether the pulp bale (3) is misaligned by comparing at least one operating parameter with a corresponding target displacement parameter for each electric actuator (11a-d, 11a'-d') cooperating with the four folding arms (5a-d).

10. A folding device according to any one of the preceding claims, It is characterized in that Two lower folding arms (6a-b) are symmetrically arranged at opposite sides of the bale folding area (4), wherein for each of the two lower folding arms, at least one electric actuator (12a-b, 12a'-b') is arranged to cooperate therewith so that the contact element (9a) is vertically displaceable from below towards the bale folding area to contact the packaging material at the corresponding lower edge (3') of the pulp bale.

11. A folding device according to any one of the preceding claims, It is characterized in that Also included is a rotating device (17) arranged to engage with the pulp bale (3) to rotate the pulp bale when positioned at the bale folding area (4), the rotating device being electrically controlled by the control unit (15).

12. A folding device according to claim 11 as appended to claim 10, in, For each of the two lower folding arms (6a-b), at least one electric actuator (14a-b, 14a'-b') is arranged to cooperate therewith so that the contact element (9a) is laterally displaceable, wherein the control unit is configured to: before controlling the rotation device to rotate the pulp bale, control the electric actuator (12a-b, 12a'-b', 14a-b, 14a'-b') cooperating with the two folding arms to: - raising the contact elements (9a) of the two folding arms to a vertical level above the bale folding area (4), and then - moving the contact elements (9a) of the two folding arms towards each other to push opposite sides of the pulp bale.

13. Method for controlling an electric actuator of a folding device for folding an end of a packaging material around a bale of pulp, the folding device include: - at least two folding arms (5a-d, 6a-b, 7a-d), each comprising a contact element (8a-d; 9a; 10a-b); and at least two electric actuators (11a-d, 11a'-d', 12a-b, 12a'-b', 13a-b, 13a'-b', 14a-b, 14a'-b'), each arranged to cooperate with one or more of the folding arms to displace a contact element thereof so as to come into contact with the packaging material to fold the packaging material around an edge (3', 3") of the pulp bale, The method includes: - for each electric actuator, determining at least one operating parameter, said operating parameter comprising a position parameter associated with the position of one or more contact elements and / or a force parameter indicative of an actuator force or torque and / or a position or velocity parameter indicative of a position or velocity of the actuator or of the folding arm; - controlling said at least two electric actuators using said at least one operating parameter.

14. A data processing apparatus comprising means for executing the method as claimed in claim 13.

15. A computer program product comprising instructions which, when executed by a computer, cause the computer to perform the method as claimed in claim 13.

16. A computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to perform the method of claim 13.

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