BACKGROUND

[0001] Printing systems may comprise media loading devices to receive different types of media. In use, a media loading device moves a loaded media to a print zone in which a printing operation is to be performed over the media. Some media loading devices are capable of loading media in a roll-to-sheet configuration, a sheet-to-sheet configuration, a roll-to-sheet configuration, or a sheet-to-roll configuration. In some examples, a media loading device may have multiple configurations, thereby enhancing the overall flexibility of the media loading device by increasing its loading capabilities.

BRIEF DESCRIPTION OF THE DRAWINGS [0002] Features of the present disclosure are illustrated by way of example and are not limited in the following figure(s), in which like numerals indicate like elements, in which:

[0003] FIG. 1 shows a schematic drawing of a media handling device loading a media, according to an example;

[0004] FIG. 2 shows a schematic drawing of the media handling device of FIG. 1 generating a first buckle;

[0005] FIG. 3 shows a schematic drawing of the media handling device of FIG. 2 releasing the first buckle;

[0006] FIG. 4 shows a schematic drawing of the media handling device of FIG. 3 generating a second buckle;

[0007] FIG. 5 shows a schematic drawing of the media handling device of FIG. 4 releasing the second buckle;

[0008] FIG. 6 shows a schematic of a media handling device comprising a skew sensor, according to an example;

[0009] FIG. 7 shows a method to deskew a media, according to an example; [0010] FIG. 8 shows a flowchart illustrating a method to compare a corrected skew with a threshold skew, according to an example; and [0011] FIG. 9 shows a computer-readable medium comprising instructions, according to an example. DETAILED DESCRIPTION

[0012] For simplicity and illustrative purposes, the present disclosure is described by referring mainly to examples. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. It will be readily apparent, however, that the present disclosure may be practiced without limitation to these specific details. In other instances, some methods and structures have not been described in detail so as not to unnecessarily obscure the present disclosure.

[0013] Throughout the present disclosure, the terms "a" and "an" are intended to denote at least one of a particular element. As used herein, the term "includes" means includes but not limited to, the term "including" means including but not limited to. The term "based on" means based at least in part on.

[0014] Media handling devices are used to move a media from an input region to an output region. Such media handling devices may be part of a printing system or may be a complementary device to be installed and used by the printing system. In use, media handling devices move a loaded media from an input region through a media path towards an output region such as a print zone in which printing operations are to be performed. The input region may be, for instance, a media tray in which sheets of media are stacked, a leading-edge of a media roll, an input slot tray in which users may manually insert a media sheet, amongst others.

[0015] Since different media configurations are possible, media handling devices may load media configurations such as a roll-to-sheet configuration, a sheet-to-sheet configuration, a roll-to-sheet configuration, or a sheet-to-roll configuration. In order to provide a media handling device capable to receive multiple media configurations, some media handling devices comprise movable sets of rollers such that the media handling device is configured to receive a specific media configuration.

[0016] As previously explained, to perform a printing operation over a media, a media handling device conveys the media from an input region to an output region such as a print zone. Hence, an aspect of the media handling devices is to deliver the media to the output region in an accurate manner, i.e. , having an appropriate alignment and an appropriate position to start subsequent operations such as a printing operation or a cutting operation. If the media is not properly aligned, for instance be skewed with respect to an expected position, when the media is delivered to start the subsequent operation, the result of such operation will diverge with respect to the expectations of the user.

[0017] As used herein, the term “skew” will be used to refer to a difference between an expected alignment of a media within a media path and an actual alignment of the media within the media path. A media may be considered as “skewed” upon exceeding a maximum acceptable skew, for instance, a skew between 0,15° and 0,25 °, such as 0,17°.

[0018] In order to provide accurate and reliable positioning of a media within the print zone, printing systems may comprise skew sensors to determine a media skew. By determining a position of the media, skew sensors can determine the presence of skew, for instance, by measuring a skew angle between an expected alignment and an actual alignment. An example location for the skew sensor may be nearby the input region of the media handling device. If a skew is detected for the loaded media, users can easily correct its position and/or its orientation. However, locating the skew sensor next to the input region does not assure that the media will still be properly positioned when reaching the output region, for instance, the print zone. As a result, a subsequent operation, for instance a printing performed over the skewed media may not satisfy the expectations of the user. An alternative location of the skew sensor that may provide more reliable measurements may be nearby the output region, for instance upstream an entrance of the print zone or an entrance to a cutting zone. However, upon a media skew is determined, since the media position and/or orientation may not be automatically corrected at that stage, the users may be requested to perform an assistance operation such as manually extracting the media from the printing system.

[0019] Among the reasons that may contribute to a poor alignment of a media, examples comprise a bad positioning of the media in an input region of the media handling device, a skew derived from a media movement through the media handling device, or the presence of external elements within the media path. Since some media paths have a large length, an input skew in the input region of the media handling device is increased to a larger output skew when the media is delivered in the output region.

[0020] In order to provide an aligned media to an output region, methods to reduce media skew may be used. In the same way, systems and devices may be used so as to correct the alignment of a media.

[0021] According to an example, a media handling device comprises rollers to move a media within a media path from an input region to an output region. Once the media reaches the input region, the rollers rotate such that the media is moved towards the output region in which a subsequent operation is to be performed on the media. The media handling device defines a media path for the media, the media path extending along the rollers and delimited by an upper media guide. In an example, the rollers comprise a first set of rollers and a second set of rollers, wherein the first set of rollers is rotatable about a first rotation axis and the second set of rollers is rotatable about a second rotation axis. The second set of rollers, and consequently, the second rotation axis of the second set of rollers, is movable towards the media to a first position and away from the media to a second position. In the first position (alternatively referred to as engaged position), the second set of rollers is positioned adjacent to the media path, i.e. , the second set of rollers is capable of contacting a media moving through the media path. In the second position (alternatively referred to as disengaged position), the second set of rollers is moved away from the media path, i.e., the second set of rollers is not capable of contacting a media moving through the media path.

[0022] According to some examples, the rollers of a media handling device may be used to correct a misalignment of the media, i.e., a media skew. By exerting forces towards the media, the reaction forces generated by the media may provide a movement of the media such that its alignment is corrected. In an example, the rollers of the media handling device may be used to generate a buckle within the media handling device. By releasing the buckle, a resulting force may correct the position of the media within the media path. In other examples, additional buckles may be created once a first buckle is released. By subsequently generating and releasing buckles, the alignment of the media within the media path is improved.

[0023] Throughout the description, the term “buckle” will be used to refer to the result of moving a leading-edge of a media towards a trailing edge, moving the trailing edge towards the leading edge, or moving both edges towards their opposite edge. The movement may be generated by subjecting the media to at least a force. When generating a buckle, a media may be bent, folded, crumpled, curved, warped, or flexed so that a crest, wave, undulation, bump, or loop is generated. Upon the release of the buckle, a media back tension of the buckle may cause a movement in at least one of the leading-edge and the trailing edge of the media.

[0024] Referring now to FIG. 1 , a schematic drawing representing a lateral view of a media handling device 100 is shown. The media handling device 100 comprises a first set of rollers 110 rotatable about a rotation axis, a second set of rollers 120 movable between two positions, an upper media guide 130, and a controller 140. The media handling device 100 may be used to deskew a media 102. The media 102 is to move through a media path 101 between the first and second set of rollers and delimited by the upper media guide 130 of the media handling device 100. In particular, the media 102 is to move through the media path 101 from an input region 100a to an output region 100b of the media handling device 100. In order to deskew the media, the media handling device 100 may perform a series of operations on the media such that the media is aligned, i.e. , deskewed.

[0025] In FIG. 1 , the second set of rollers 120 is movable towards the media 102 to a first position 121a and away from the media 102 to a second position 121 b. At the first position 121a, the second set of rollers 120 is capable of pinching a media moving through the media path 101. At the second position 121 b, the second set of rollers 120 is away from the media path 101 , i.e., at a position in which the media is depinched. In FIG. 1 , due to the second set of rollers 120 is located upstream of the first set of rollers 110, a media moving through the media path 101 reaches a nip region of the second set of rollers 120 before reaching a nip region of the first set of rollers 110. In some examples, the first position 121a is referred to as a pinch position and the second position 121b is referred to as a depinch position.

[0026] To drive the first set of rollers 110, the media handling device 100 may comprise a first motor (not shown in FIG. 1 ). The first motor may be, for instance, an electrical motor or a servo-controlled direct current (DC) motor. By driving the first motor, the first set of rollers 110 rotate in a first rotation direction such as a clockwise rotation and a second rotation direction such as a counterclockwise rotation direction. When rotating the first set of rollers 110 in the counterclockwise direction, a forward movement for the media provided. When rotating the first set of rollers 110 in the clockwise direction, a backward movement for the media is provided. In FIG. 1 , the first set of rollers 110 rotates in a counterclockwise direction 112a and the second set of rollers rotates in a counterclockwise direction 122a. As a result of the rotations, the media 102 advances to the output region 100b of the media handling device 100 through the media path 101. To uniformly move the media 102 through the media path 101 , the first set of rollers 110 and the second set of rollers 120 move at the same speed. Flowever, in other examples, each of the first set of rollers 110 and the second set of rollers 120 may rotate at different angular speeds based on a relationship between radii. In order to simplify the representation, in FIG. 1 the rollers are represented as having the same radius. Flowever, in some other examples, the media handling device 100 may advance the media 102 to the output region 100b by rotating the first set of rollers 110 in the counterclockwise direction 112a while the second set of rollers is positioned at the second position 121b.

[0027] In FIG. 1 , the media handling device 100 further comprises an actuator module 123 mechanically connected to the second set of rollers 120. The actuator module 123 is to move the second set of rollers 120 between the first position 121a and the second position 121 b. In addition, the actuator module 123 transmits a mechanical force to the second set of rollers 120 to rotate the rollers. The controller 140 may selectively control the rotation of the first set of rollers 110 and the second set of rollers 120. Furthermore, controller 140 controls the actuator module 123 to move the second set of rollers 120 between the first position 121a and the second position 121b. [0028] It should be noted, that even though in FIG. 1 the rotation directions are referred to as clockwise and counterclockwise, these directions are merely indicative and, depending on the position of the media handling device 100, rotation directions could be the opposite. In other examples, the rotation directions may be defined as a first rotation direction and a second rotation direction, wherein the second rotation direction results in a forward movement of the media and the first rotation direction results in a backwards movement of the media, being the first rotation direction opposite to the second rotation direction. [0029] Throughout the description, the mechanical connection between mechanical elements such as the actuator module, motors or rollers or the transmission of mechanical force within the actuator module may for example take place using one or more gears, one or more belts, one or more pulleys, one or more chains, one or more cables, one or more cams, one or more crank, one or more shaft, one or more clutch, one or more lever, one or more swing arms, one or more mechanical switches, or a combination thereof.

[0030] Referring now to FIG. 2, a lateral view of a media handling device 200 generating a first buckle 203 is shown. The media handling device 200 corresponds to the media handling device 100 previously explained in reference to FIG. 1 . In FIG. 2, the first set of rollers 110 pinches the media 102 at a first nip region 231 while rotating in a clockwise direction 212b so that a leading-edge of the media is substantially parallel to the rotation axis of the first setoff rollers 110. At the same time, the second set of rollers 120 pinches the media 102 at a second nip region 232. In order to pinch the media 202, the second set of rollers 120 is positioned at the first position, i.e. , the engaged position. In an example, the second set of rollers 120 is locked so that it cannot rotate, and hence, the clockwise rotation 212b of the first set rollers 110 generates the first buckle 203 under the upper media guide 130. To lock the second set of rollers 120, the actuator module mechanically connected to the second set of rollers 120 may prevent a rotation of the second set of rollers 120. In other examples, the actuator module may transmit a minimum torque to the second set of rollers 120 such that the second set of rollers 120 does not rotate because of the media back tensions. The minimum torque may be selected, for instance, based on a type of media loaded in the media handling device 200. In other examples, to generate the first buckle 203, the second set of roller 120 may rotate in an opposite direction to the clockwise direction rotation 212b of the first set of rollers 110, i.e. , a counterclockwise direction.

[0031] In the example of FIG. 2, the first set of rollers 110 rotates in the clockwise direction 212b until a leading-edge of the media 202 is behind the first nip region 231. As a result of the rotation in the clockwise direction 212b, the leading-edge of the media 202 is left substantially parallel to a rotation axis of the first set of rollers 110. However, in other examples, the first set of rollers 110 may rotate a predefined number of revolutions in the clockwise direction 212b wherein the predefined number of revolutions is calculated to ensure that the leading-edge of the media is behind the nip region 231. In some other examples, the media handling device 200 may comprise a sensor to determine that the leading-edge of the media 202 is behind the first nip region 231 . In further examples, the predefined number of revolutions is selected based on a type of media loaded in the media handling device 200, wherein the type of media is determined based on a series of media characteristics associated to the media, such as density, stiffness, thickness, length, amongst others.

[0032] In further examples, the first set of rollers 110 may be driven by a servo- controlled motor. To determine that the first buckle 203 has been generated, a media back tension of the media 102 may be calculated based on a difference between an estimated speed and an actual speed of the first set of rollers 110. Since the rotational speed of the servo-controlled motor is transmitted to the first set of rollers 110, the differences with respect to the estimated speed may be associated to a resistance force of the media 102, i.e., a media back tension. If the media back tension is greater than a threshold tension, the first buckle 203 is considered to be generated. In some other examples, a voltage of the servo- controlled motor may be measured while the first set of rollers 110 are rotating at an angular speed. By measuring the voltage changes while rotating the first set of rollers 110, a first buckle generation may be determined. Upon the voltage reaches a steady state, i.e., the voltage is constant over a period of time, the first buckle is considered to be generated. [0033] In some other examples, the media handling device 200 further comprises a first set of idle rollers and a second set of idle rollers attached on a surface of the upper media guide 230. The first set of idle rollers and the second set of idle rollers may be used to nip the media in the first nip region 231 and the second nip region 232, respectively.

[0034] Referring now to FIG. 3, a media handling device 300 upon releasing a first buckle is shown. The media handling device 300 corresponds to the media handling devices 200 previously explained in reference to FIG. 2. Once the first buckle has been generated, the first set of rollers 110 is locked so that a rotation is prevented. Then, the actuator module moves the second set of rollers 120 from the first position to the second position 121 b thereby releasing the first buckle of FIG. 2. By moving the second set of rollers 120 to the second position 121 b, the media 102 is depinched and a backwards movement 304 of the media 102 is obtained. The backwards movement 304 releases the media back tension of the media 102, and a first skew re-alignment is performed while the leading-edge of the media 202 remains aligned with the first nip region.

[0035] In some examples, the generation of the first buckle and its subsequent release by depinching the media is managed by the controller 140. As described above, controller 140 is to control the rotation of each of the first set of rollers 110 and the second set of rollers 120. Once a media skew is determined, controller 140 controls the generation of a buckle by controlling the rotation of each of the first set of rollers 110 and the second set of rollers 120. When media has high stiffness, the controller 140 may generate smaller buckles. In a similar way, smaller buckles may be generated, for instance, when deskewing thicker medias. In an example, the smaller buckle is generated by rotating the first set of rollers in the clockwise direction and additionally rotating the second set of rollers 120 in the clockwise direction, being an angle rotated by the second set of rollers 120 lower than an angle rotated by the first set of rollers 110. By providing an additional angular rotation in the first set of rollers 110 with respect to the second set of rollers 120, the difference in angles will generate a smaller buckle when compared to buckles generated by rotating an angle the first set of rollers 110 in the clockwise direction. [0036] Referring now to FIG. 4, a media handling device 400 generating a second buckle 405 is shown. The media handling device 400 corresponds to the media handling device 300 previously explained in FIG. 3. In FIG. 4, to generate a second buckle 405, the second set of rollers 120 rotates in a counterclockwise direction 122a. Because the media 102 is pinched by the second set of rollers 120, the second buckle 405 is generated under the upper media guide 130 of the media handling device 400. In an example, the first set of rollers 110 may be locked so that the media 102 is fixed at the nip region 231. In other examples, the first set of rollers 110 rotates in an opposite direction to the counterclockwise direction 122a of the second set of rollers 120 while the second set of rollers 120 is generating the second buckle 405, i.e. , the first set of rollers 110 rotates in a clockwise direction. In other examples, the motor driving the first set of rollers 110 may apply a minimum torque to the first set of rollers 110 such that the media 102 does not move beyond the nip region 231 of the first set of rollers 110.

[0037] In order to generate the second buckle 405, the second set of rollers 120 may rotate in the counterclockwise direction 122a a specific distance. The specific distance may be limited, for instance, by the available space under the upper media guide 130 for generating the second buckle 4Fi05. Such a distance may be obtained, for example, by rotating the second set of rollers 120 a certain angle, for instance by rotating at an angular speed over a time period so that a number of revolutions is obtained. Upon the second set of rollers 120 has been rotated the certain angle, the second buckle 405 is considered to be generated. In other examples, the generation of the second buckle 405 may be based on a media back tension received from the media 102. The media back tension may be determined, for instance, by using the readings of the actuator module driving the second set of rollers 120, as previously explained in reference to other examples. In other examples, the specific distance may be defined, for instance, by a length of the media. Longer medias may be capable of generating bigger buckles compared to shorter medias.

[0038] As previously explained in FIG. 2, the generation of a buckle may be controlled by monitoring differences when using a servo-controlled motor. Therefore, when the actuator module that drives the second set of rollers 120 comprises a servo-controlled motor, the media back tension may be determined based on the differences between an expected number of revolutions and an actual number of revolutions. The differences may be obtained for instance, by reading a voltage of the servo-controlled motor. By determining a difference between the number of revolutions (or an expected voltage and an actual voltage), a media back tension may be calculated by the controller 140. Then, if the media back tension value is greater than a threshold media back tension, the second buckle 405 is considered to be generated. In other examples, the media back tension of the media may be calculated based on angular speed differences. In an example, the servo-controlled motor is set at a reference voltage associated with an angular speed that results in a reference force towards the media 102. However, because the second buckle 405 is being generated, an actual angular speed is lower than the angular speed associated with the reference voltage because a counterforce of the media 102 exerted to the second set of rollers 120. By reading the differences between the angular speed and the actual angular speed, a media back tension associated with the second buckle 405 may be determined.

[0039] Referring now to FIG. 5, a media handling device 500 releasing the second buckle is shown. The media handling device 500 corresponds to the media handling devices 400 previously explained in FIG. 4. In FIG. 5, the controller 140 controls the actuator module to move the second set of rollers 120 to a second position 121b in which the second set of rollers 120 is moved away from the media, thereby releasing the second buckle. In addition, the first set of rollers 110 rotate in a counterclockwise direction 112a so that the media 102 is pinched in the first nip region 231 and a forward movement 506 is obtained. Upon releasing the second buckle, a second skew re-alignment of the media 102 is performed. In some examples, the rotation and the movement of the second set of rollers to the second position 121 b are performed at the same time. In other examples, the rotation of the first set of rollers 110 in the counterclockwise direction 112a may be performed before moving the second set of rollers 120 to the second position 121 b. In some other examples, the rotation is performed after moving the second set of rollers 120 to the second position 121 b. [0040] According to some examples, a media handling device may comprise a skew sensor to determine a skew of the media. Once a media skew is determined, the first set of rollers and the second set of rollers may rotate in a counterclockwise direction and in a clockwise direction in order to generate/release the first buckle and the second buckle. Once the second buckle is released, the skew sensor may determine if a corrected skew falls within a skew threshold. If the corrected skew is determined to be within the skew threshold, the media is moved to the output region of the media handling device. However, if the corrected skew is determined to be outside the skew threshold, the media handling device may generate/release a third buckle and a fourth buckle in order to further correct the corrected skew of the media. In the same way, if a subsequent corrected skew determined after release of the fourth buckle is outside the threshold, the operations may be repeated. Upon a determined number of repetitions are performed, such as N repetitions (where N may be, for instance, 2, 3, 4, or 5), an error warning may be triggered by the media handling device.

[0041] Referring now to FIG. 6, a schematic drawing representing a lateral view of a media handling device 600 having a skew sensor 650 is shown. The media handling device 600 comprises a first set of rollers 610, a second set of rollers 620, an upper media guide 630, a controller 640, and the skew sensor 650. As previously explained, the controller 640 is to control rotation of each of the first set of rollers 610 and the second set of rollers 620, wherein the rollers are rotatable in a first rotation direction (clockwise direction) and a second rotation direction (counterclockwise direction). An actuator module 623 is configured to move the second set of rollers 620 towards a media to an engaged position 621a (in which the second set of rollers 620 is capable of pinching the media) and away from the media to a disengaged position 621 b. The media handling device 600 is to receive a media in an input region 600a. Upon receiving the media, the media moved towards an output region 600b through a media path 601 extending along the first and second set of rollers and delimited by the upper media guide 630 of the media handling device 600. In FIG. 6, media handling device 600 comprises a first set of idle rollers 631 and a second set of idle rollers 632, wherein both the first set of idle rollers 631 and the second set of idle roller 632 may be attached on a surface of the upper media guide 630. As previously explained, the rollers nip the media in a first nip region 631 and a second nip region 632. As a result, in FIG. 6, the first set of rollers 610 and the first set of idle rollers 631 nip the media at the first nip region 631 and the second set of rollers 620 and the second set of idle rollers 632 nip the media at the second nip region 632 when the second set of rollers 620 is at the engaged position 621a.

[0042] In some examples, the media handling device 600 may generate and release a first buckle and a second buckle, as previously explained in the description. For example, the media handling device 600 may determine a skew using the skew sensor 650 and, based on the determined skew, may trigger some of the actions previously explained in reference to FIGs. 2 to 5. Upon the second buckle is released, the skew sensor 650 may determine a corrected skew value. If the corrected skew value is outside a skew threshold range, the actions of FIGs. 2 to 5 may be repeated over the media. Once the actions have been carried out, the skew sensor 650 may determine a subsequent corrected skew.

[0043] In some other examples, the skew sensor 650 may determine if a skew exceeds a maximum skew value. If the skew is greater than the maximum skew value, an error may be triggered by controller 640 of the media handling device 600. In an example, the maximum skew value is between 1 ° and 3°, such as 1 ,15°.

[0044] According to some examples, a printing system to receive a media comprises a media handling device and a print engine. The media handling device may be, for instance, one of the media handling devices 100 and 600 previously explained in FIGs. 1 and 6. The media handling device, as previously described, is to receive the media in an input region and to output the media in an output region. The print engine is to receive the media from the output region of the media handling device, wherein the media handling device is to correct a skew of the media. In an example, the print engine may perform printing operations on the media upon receiving the media from the output region. By using a printing system comprising one of the media handling devices previously described, a correction of a media skew is performed before performing printing operations over the media. Hence, the usage of a media handling device along with a print engine allows users to get a more reliable printing system, at least in terms of media skew.

[0045] According to other examples, a media handling device may be used to perform a method to deskew a media. In an example, a method is to be performed in a system comprising a first roller and a second roller upstream the first roller, wherein the second roller is movable towards the media to an engaged position and away from the media to a disengaged position. The first roller may correspond, for instance, to the first set of rollers of the media handing device. The second roller may correspond, for instance, to the second set of rollers of the media handling device. As previously explained in other examples, the engaged position may be alternatively referred to as a first position of the second set of rollers and the disengaged position may be alternatively referred to as a second position of the second set of rollers.

[0046] Referring now to FIG. 7, a method 700 to deskew a media is shown. Method 700 may be performed, for instance, by using a system such as one of the media handling devices previously explained. The system may comprise a first roller, and a second roller upstream the first roller, wherein the second roller is movable between an engaged position and a disengaged position. At block 710, method 700 comprises moving the second roller to the engaged position. During the engaged position, the second roller is capable of contacting a media moving through the media path. Hence, as a result of the movement of the second roller to the engaged position, the media is pinched by the second roller. At block 720, method 700 comprises rotating a first roller in a first rotation direction thereby generating a first buckle. The first rotation direction may be, for instance, the clockwise direction 212b previously explained in reference to the first set of rollers 110 in FIG. 2. In an example, rotating the first roller in a first rotation direction comprises rotating the first roller until a leading-edge of the media is behind a nip region associated with the first roller. In other examples, rotating a first roller in a first rotation direction comprises rotating the first roller in the first rotation direction, determining a number of revolutions of the first roller, comparing the number of revolutions to a maximum number of revolutions, and stopping the first roller rotation upon the number of revolutions of the first roller exceeds the maximum number of revolutions. Then, at block 730, method 700 comprises moving the second roller to the disengaged position. As a result of the disengagement, the media is depinched, thereby releasing the first buckle. Because of the release of the media back tension of the first buckle, the media experiences a backwards movement. At block 740, method 700 comprises moving the second roller to the engaged position. By moving the second roller to the engaged position, the media is pinched. At block 750, method 700 comprises rotating the second roller in a second rotation direction thereby generating a second buckle, being the second rotation direction opposite to the first rotation direction. The second rotation direction may be, for instance, the counterclockwise direction 122a previously explained in FIG. 1. In an example, rotating the second roller in the second rotation direction comprises rotating the second roller a certain angle. In other examples, the angle is selected based on the type of media. In some examples, a series of certain angles associated with a series of types of media may be stored in a memory, for instance in the form of a look-up table. Based on the type of media loaded in the media handling device, a certain angle value may be obtained from the look-up table. At block 760, method 700 comprises moving the second roller to the disengaged position. The movement of the second rollers to the disengaged position releases the second buckle. As a result of the release of the media back tension of the second buckle, a second re-alignment of the media is obtained. Then, at block 770, method 700 comprises rotating the first roller in the second rotation direction. The rotation of the first roller in the second rotation direction advances the media beyond the nip region. In an example, block 760 and block 770 may be alternatively performed in a different order. In other examples, block 760 and block 770 are performed at the same time. In other examples, a delay time may be introduced between block 760 and 770.

[0047] As previously explained, during generation of the first buckle and/or the second buckle, the rotation of the opposite roller may be locked. In an example, method 700 further comprises locking a second roller rotation while generating the first buckle, and locking a first roller rotation while generating the second buckle. The rotation may be locked by controlling a corresponding driving motor to provide a minimum torque so that a position of the media in the nip region is locked. In other examples, the rotation may be locked by setting a motor at a voltage so that rotation is locked. In some other examples, instead of locking the rotation, the opposite roller may be rotated in an opposite rotation direction to the roller generating the buckle. For instance, when the first roller is rotating in the first direction to generate the first buckle, the second roller may rotate in the second direction.

[0048] In some examples, blocks 710 and 720 may correspond to the media handling device 200 of FIG. 2, block 730 may correspond to the media handling device 300 of FIG. 3, blocks 740 and 750 may correspond to the media handling device 400 of FIG. 4, and blocks 760 and 770 may correspond to the media handling device 500 of FIG. 5. Flowever, in other examples blocks 710 to 770 may be performed by using the media handling device 600 of FIG. 6.

[0049] In other examples, the system may further comprise a skew sensor to determine a skew of the media. Method 700 may further comprises determining a skew of the media, comparing the skew to a threshold skew, and triggering an error warning if the skew is greater than a maximum skew. In some other examples, comparing the skew to the threshold skew further comprises reading from a memory data associated to the loaded media and determining the threshold skew based on the data associated to the loaded media. Then, if the media is determined to have a skew greater to the determined threshold skew, an error warning is triggered. In an example, the threshold skew is a skew value between 1° and 3°, such as 1,16°.

[0050] According to an example, a method to deskew a media may further comprise determining a corrected skew of a media upon the second buckle is released and comparing the corrected skew of the media to a threshold skew. If the corrected skew of the media is greater than the threshold skew, the method comprises repeating the steps associated with blocks 710 to 770. The method may further comprise triggering an error warning if the steps associated with blocks 710 to 770 are repeated a determined number of times, for instance, 3 times. In an example, the corrected skew may be determined at block 770 by using a skew sensor.

[0051] Referring now to FIG. 8, a flowchart representing method 800 is shown. Method 800 comprises performing the method 700 previously explained in FIG. 7. Upon performing method 700, at block 801 , method 800 comprises determining a corrected skew of the media. Then, at block 820, the corrected skew of the media is compared with a threshold skew. If the corrected skew is equal or lower than the threshold skew, at block 804, method 800 comprises rotating the first roller in a second rotation direction to move the media. The media may be moved, for instance, to an output region of the system. In other examples, the media is moved beyond the nip region. If the corrected skew is greater than the threshold skew, at block 803, method 800 comprises comparing number of times that the method 700 has been executed over the media. If the number of times that method 700 has been executed is lower than a determined amount of times (for instance, N), method 800 comprises repeating the blocks 700, 801 , and 802. Every time that block 800 is repeated, the number of times that the method 900 has been executed over the media is increased by one. Upon the number of times reaches the determined amount of times, at block 805, method 800 comprises triggering an error warning. In an example, the determined number of times may be stored in a memory. In other examples, the determined number of times may vary for each media type, wherein a look-up table is available for different media types associated to types of media having different media characteristics. Examples of media characteristics comprise media density, media stiffness, media thickness, media length, media width, amongst others.

[0052] In some examples, the error warning is displayed on a display of a system. For instance, if method 800 is performed by using a printing system, the printing system may comprise a display in which the error warning is shown. Then, users may perform corrective actions over the printing system to extract the skewed media.

[0053] According to some examples, methods 700 and 800 are performed by using a system such as a printing system to receive a media. As described above, a printing system may comprise a media handling device and a print engine. The media handling device may be, for instance, one of the media handling devices previously explained in the description. The media handling device, as previously described, is to receive the media in an input region and to output the media in an output region. The print engine is to receive the media from the output region of the media handling device, wherein the media handling device is to correct a skew of the media. In an example, the print engine may perform printing operations over the media upon receiving the media from the output region. By using a printing system comprising one of the media handling devices previously described, a skew correction over the media is performed before performing printing operations over the media.

[0054] According to some examples, a computer-readable medium may comprise instructions that, when executed a processor, cause a system such as a media handling device or a printing system comprising a media handling device to perform a series of actions. Examples of computer-readable medium comprise any non-transitory tangible medium that can embody, contain, store, or maintain instructions for use by a processor. Computer-readable media include, for example, electronic, magnetic, optical, electromagnetic, or semiconductor media. More specific examples of suitable computer-readable media include a hard drive, a random access memory (RAM), a read-only memory (ROM), memory cards and sticks, and other portable storage devices.

[0055] Referring now to FIG. 9, a computer-readable medium 900 comprising instructions is shown. The instructions, when executed by a processor, cause a system comprising a first set of rollers downstream a second set of rollers to execute a series of actions. At block 910, the instructions cause the system to determine a presence of a media within the media path extending along the first set of rollers and the second set of rollers and delimited by an upper media guide. In order to determine the presence of the media, the system may comprise a sensor such as a presence sensor. In other examples, the presence of a media is determined by a skew sensor, wherein the skew sensor is to determine a skew of the media. At block 920, the instructions cause the system to move the second set of rollers to an engaged position. As explained above, the second set of rollers is movable towards the media to an engaged position and away from the media to a disengaged position. At block 930, the instructions cause the system to rotate the first set of rollers in a first rotation direction to generate a first buckle. The first rotation direction may be, for instance, the clockwise direction 212b previously explained in reference to the first set of rollers 110 in FIG. 2. Since the second set of rollers is pinching the media, a trailing edge of the media is fixed and the first buckle is generated. In an example, the second set of rollers is rotated in a second rotation direction opposite to the first rotation direction while the first set of rollers is generating the first buckle. In other examples, the instructions may further cause the system to lock a rotation of the second set of rollers while the first set of rollers is rotating in the first rotation direction to generate the first buckle. In further examples, the actuator module mechanically connected to the second set of rollers transmits a minimum torque to the second set of rollers such that the rotation of the second set of rollers is prevented. At block 940, the instructions cause the system to move the second set of rollers to the disengaged position. The movement of the second set of rollers releases the first buckle, thereby providing a backwards movement that aligns the media. Then, at block 950, the instructions cause the system to move the second set of rollers to the engaged position. Once the second set of rollers pinches the media, at block 960, the instructions cause the system to rotate the second set of rollers in the second rotation direction, being the second rotation direction opposite to the first rotation direction. In an example, the second rotation direction of the second roller corresponds to the counterclockwise direction 121a previously explained in the media handling device 100 of FIG. 1 . In a similar way to the generation of the first buckle, the opposite roller may be operated such that the second buckle is properly generated. In some examples, the computer-readable medium 900 may comprise further instructions to cause the system to rotate the first set of rollers in the first rotation direction while the second set of rollers is rotating in the second direction to generate the second buckle. At block 970, the instructions cause the system to move the second set of rollers to the disengaged position. The movement results in a release of the second buckle, thereby resulting in a forward movement that aligns the media that reduces the skew. In other examples, the instructions may further comprise instructions cause the system to rotate the first set of rollers in the second rotation direction to move the media beyond the nip region.

[0056] In some examples, the computer-readable medium 900 may comprise further instructions to cause the system to determine a skew of the media, compare the skew with an allowable skew value, and trigger an error if the skew is greater than the maximum skew. By triggering the error, the system can prevent defects over the media such as inappropriate alignment or high skew values that may result in media jams. The skew may be determined, for instance, based on the readings of a skew sensor. In other examples, a corrected skew may be determined for the media upon releasing the second buckle. Upon determination, the corrected skew may be compared with the allowable skew value. If the corrected skew is greater than the allowable threshold value, the instructions may further comprise repeating blocks 910 to 970 so that the corrected skew of the media is reduced.

[0057] In some other examples, the rotation of each of the first set of rollers and the second set of rollers is performed based on predefined speeds over a time period or a number of revolutions. In an example, at block 930, rotate the first set of rollers in the first rotation direction comprises rotate the first set of rollers in the first rotation direction at an angular speed, determine a difference between an actual angular speed and the angular speed, the actual angular speed being measured with a sensor, and calculate a media back tension of the media based on the difference. If the media back tension is greater than a threshold media back tension, the first buckle is considered to be generated. In an example, the sensor is an optical encoder capable of determining an angular speed of the first set of rollers.

[0058] What has been described and illustrated herein are examples of the disclosure along with some variations. The terms, descriptions, and figures used herein are set forth by way of illustration only and are not meant as limitations. Many variations are possible within the scope of the disclosure, which is intended to be defined by the following claims (and their equivalents) in which all terms are meant in their broadest reasonable sense unless otherwise indicated.