EP4733076A1

EP4733076A1 - Winding up print media with a relatively high or low bending stiffness

Info

Publication number: EP4733076A1
Application number: EP24208647.8A
Authority: EP
Inventors: Luuk ROUMEN; Marcus H.G.W. Hees
Original assignee: Canon Production Printing Holding BV
Current assignee: Canon Production Printing Holding BV
Priority date: 2024-10-24
Filing date: 2024-10-24
Publication date: 2026-04-29

Abstract

An improved method for winding print media (5-7) onto a take-up roller (33) which allows for a wider range print media to be tightly wound up, specifically with a wider range of bending stiffnesses. The method comprises the steps of:
- forming a blouse (28) in the print medium (5-7) upstream of the take-up roller (33);
- clamping the print medium (5-7) by means of a clamp (30) between the blouse (28) and the take-up roller (33), when the print medium (5-7) is fed into the blouse (28) and when the take-up roller (33) is prevented from rotating;
- releasing the clamp (30) when the take-up roller (33) is rotated to wind up print medium (5-7) from the blouse (28),
characterized by the step of rotating the take-up roller (33) to adjust a tension in the print medium (5-7) between the blouse (28) and the take-up roller (33) while clamping the print medium (5-7).

Description

BACKGROUND OF THE INVENTION

1. Field of the invention

The invention relates to a method for winding a print medium onto a take-up roller and to a roll printer.

2. Description of Background Art

A roll printer comprises an input roller from which a print medium is unspooled past a print station towards a take-up roller, where the print medium is re-wound. Certain roll printers comprise a blouse former between the print station and the take-up roller. The blouse former locally forms a U-shape in the print medium, thereby decoupling the respective sides of the print medium across the blouse former from one another. This prevents pulling forces from driving the take-up roller from displacing the portion of the print medium at the print station. This prevents wrongly positioning portions of the image on the print medium, which could otherwise have lead to visible print artifacts. Such a roll printer is known from e.g. NL2030547 , EP3366481 , and/or US9884491 . In such a printer the print medium is wound up onto the take-up roller via the steps of:

forming the blouse in the print medium upstream of the take-up roller;
clamping the print medium by means of a clamp between the blouse and the take-up roller, when the print medium is fed into the blouse and the take-up roller is prevented from rotating; and
releasing the clamp when the take-up roller is rotated to wind up print medium from the blouse.

When the clamp engages the print medium, the take-up roller is prevented from rotating to maintain a constant tension in the print medium between the clamp and the take-up roller. The take-up roller is rotated while the clamp has released the print medium to prevent excessive tension in the print medium. For a significant range of print media this method results in tightly wound rolls.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved method of winding up print media in a roll printer, specifically a method with an increased media range, even more specifically a method suited for also winding up print media with a relatively low and/or high bending stiffness, as compared to the above described range of print media.
In accordance with the present invention, a method of winding up print media on a take-up roller according to claim 1 and a roll printer according to claim 11 are provided.
The method comprises the steps of:

forming a blouse in the print medium upstream of the take-up roller;
clamping the print medium by means of a clamp between the blouse and the take-up roller, when the print medium is fed into the blouse and when the take-up roller is prevented from rotating; and
releasing the clamp when the take-up roller is rotated to wind up print medium from the blouse.

The method is characterized by the step of rotating the take-up roller to adjust a tension in the print medium between the blouse and the take-up roller while clamping the print medium with the clamp.
It is the insight of the inventors that print media with a relatively low and high bending stiffness require an adjustment in the tension in the portion between the clamp and the take-up roller to allow them to be wound up tightly, without deformation, and/or damage. It is the further insight of the inventors that this tension adjustment can be achieved by a limited rotation of the take-up roller while the clamp locally holds the print medium in place. For example, for print media with a relatively high bending stiffness, the take-up roller may be rotated in the winding direction to increase the tension to straighten and/or pull taut the portion of such print medium between the clamp and the roller. After that tensioning, the print medium can continue to be fed into the blouse, while the take-up roller maintains its angular position. After that the clamp can be released while rotating the take-up roller to wind print medium onto the take-up roller. This prevents or reduces the risk of loosely wound rolls. For print media with a relatively low bending stiffness, the take-up roller may be rotated opposite to the winding direction to decrease the tension to reduce the forces on the portion of such print medium between the clamp and the roller while the clamp is on the print medium. This prevents damage and/or deformation. It will be appreciated that for certain print media, for example those with a print medium bending stiffness in between the respective low and high bending stiffnesses, winding may be performed as described previously without rotating the take-up roller while the clamp is closed to locally adjust the tension in the print medium. This ensures that tightly wound rolls can be achieved for a wider range print media of different bending stiffnesses. Thereby the object of the present invention has been achieved.
More specific optional features of the invention are indicated in the dependent claims.
In an embodiment, while the clamp engages and fixes the print medium the following steps are performed:

the step of rotating the take-up roller to adjust a tension in the print medium between the blouse and the take-up roller while clamping the print medium; and
a step of feeding print medium into the blouse.

Printing preferably occurs at a relatively constant or regular speed, causing print medium to be fed into a blouse former at a substantially constant rate (at least on average over time). When the clamp fixes the print medium at the downstream side of the blouse former, the blouse increases in size. While the clamp locally secures the print medium, the take-up roller is also momentarily rotated to locally adjust the tension. This can be achieved by either pulling on the print medium with respect to the clamp or releasing a small amount of print medium towards the clamp. Both steps are performed in between a step of moving the clamp into its clamping position to locally fix the print medium and a step of moving the clamp out of its clamping position to release the print medium.
In an embodiment, an angle through which is take-up roller is rotated while the clamp is closed is smaller than an angle through which is take-up roller is rotated while the clamp is released from the print medium. At least 90%, preferably at least 95%, even more preferably at least 99% (as measured in time or in angular range), of the total rotation of the take-up roller, regardless of the direction, is performed while the clamp is open. The rotation when the clamp is closed is relatively small and serves the adjust the tension to suitably arrange the print medium for the next winding step.
In an embodiment, while the clamp is disengaged from the print medium, the following steps are performed:

rotating the take-up roller, so that the blouse is reduced; and
winding print medium onto the take-up roller.

When the clamp is free of the print medium, the take-up roller is rotated fast enough to pull print medium from the blouse former onto the take-up roller. Thereby, the blouse reduces in size, as per unit time more print medium leaves the blouse former than is fed into it. Note that therein preferably, the blouse former comprises a downstream support which exerts friction on the print medium, so that it is tensioned between the blouse formed and the take-up roller due to the local drag on the print medium at said support, resulting in tightly wound rolls.
In an embodiment, a majority or substantially the full print medium is wound up while the clamp is disengaged from the print medium. The majority of winding up the print medium occurs while the clamp is free of the print medium. While the clamp is closed, the take-up roller may be rotated to locally tension the print medium, wherein a small amount of print medium is wound up, but this is amount is less than 10%, preferably less than 5%, very preferably less than 3%, and even more preferably less than 1% of the print medium, specifically the length thereof.
In an embodiment, the method further comprises the step of selecting between two winding modes, which are:

a first winding mode for a first media type, wherein the take-up roller is prevented from rotating as long as the clamp clamps the print medium; and
a second winding mode for a second media type, which comprises the step of rotating the take-up roller to adjust a tension in the print medium between the blouse and the take-up roller while clamping print medium.

Print media of the first media type are wound tightly due to the friction exerted by the downstream support during winding as the clamp is open. Closing the clamp, fixes such print media with suitable tension to ensure tight winding. Print media of the second media type are either too stiff or weak in terms of bending stiffness to achieve tightly wound rolls in the first winding mode. For such print media, the second winding mode is applied. In this second winding mode, after closing the clamp, the tension between the clamp and the take-up roller is locally adjusted to within a suitable range. For example, relatively stiff print media are tensioned additionally while the clamp is closed by rotating the take-up roller over a limited angle in the winding direction. Relatively weak print media are additionally reduced in tension while the clamp is closed by rotating the take-up roller a limited angle opposite to the winding direction.
In an embodiment, a bending stiffness of the first media type is different from that of the second print media type. The second print media type comprises print media with a bending stiffness significantly above or below that of print media of the first print media type. Specifically, the bending stiffness of the first media type is greater than that of the second media sub-type and smaller than that of the first media sub-type.
In an embodiment, the method further comprises the step of driving the print medium past a print station by means of a driving roller upstream of the print station. The print medium is pushed by means of a driving roller over a print surface facing the print station. The blouse in the blouse former decouples the portion of the print medium on the print surface from the take-up roller. Pulling forces from the take-up roller do not displace the portion of the print medium on the print surface, ensuring reliable printing.
In an embodiment, the method further comprises the step of reciprocally moving a carriage over the print medium to print an image on the print medium. The printer is preferably a roll printer, specifically a scanning inkjet printer.
In another aspect, the present invention provides a roll printer with a user interface. The user interface comprises means for selecting between the different winding modes, for example in the forms of one or more selectors on the user interface. Preferably, the selector is a visual indicator which can be manipulated to switch modes, such as a button, slider, selection box, pull down menu, etc.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the present invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:

Fig. 1 is a schematic side of a roll printer in the step of loading a new print medium;
Fig. 2 is a schematic side of the roll printer in the step of attaching a new print medium to the take-up roller, as well as in the step of cutting the print medium;
Fig. 3 is a schematic side of the roll printer in the step of increasing the blouse as the clamp is closed;
Fig. 4 is a schematic side of the roll printer in the step of detecting that the blouse has reached a bottom end point of its allowed range;
Fig. 5 is a schematic side of the roll printer in the step of detecting that the blouse has reached a top end point of its allowed range in a first winding mode;
Fig. 6 is a schematic side of the roll printer in the step of detecting that the blouse has reached a top end point of its allowed range in a first winding sub-mode of a second winding mode;
Fig. 7 is a schematic side of the roll printer in the step of closing the clamp followed by rotating the take-up roller in a first winding sub-mode of a second winding mode;
Fig. 8 is a schematic side of the roll printer in the step of stopping the rotating the take-up roller after locally adjusting the tension in a first winding sub-mode of a second winding mode;
Fig. 9 is a schematic side of the roll printer in the step of stopping the rotating the take-up roller after locally adjusting the tension in a second winding sub-mode of a second winding mode; and
Fig. 10 is a diagram illustrating the steps of a method of winding up a print medium.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described with reference to the accompanying drawings, wherein the same reference numerals have been used to identify the same or similar elements throughout the several views.
Fig. 1 illustrates a roll printer (1) for printing on a print medium 5 supplied from an input roller 2. The print medium 5 is provided in roll form on the input roller 2. The input roller 2 is rotatable around its axis by means of a drive 3 to unspool the print medium 5 from its roll form. The print medium 5 is then transported to the main driving roller 8, which further transports the print medium 5 to the print surface defined by the suction chamber assembly 10. The suction chamber assembly 10 comprises one or more suction chambers 11, which can be supplied by a negative pressure by means of a suction source 12, such as a pump or fan. The top side of the suction chamber assembly 10 preferably defines a flat print surface facing the print station 14, for example formed by a perforated plate. The print station 14 comprises a carriage 15 reciprocally movable along a beam 16 to print an image on the print medium 5 in swaths. The carriage 25 comprises one or more inkjet printheads. It will be appreciated that a page-wide printhead array may be applied as well and that the transportation of the print medium 5 may be step-wide or continuous.
Downstream of the suction chamber assembly 10 a blouse former 20 is positioned. The blouse former 20 allows a substantially free-hanging segment to be locally formed in the print medium 5. Such a blouse is generally U-shaped, though the exact shape may vary dependent on e.g. the stiffness of the print medium 5. The top side of the blouse former 20 is defined by supports 21, 22. In between the supports 21, 22, the print medium 5 is allowed to sink down under the influence of gravity in an approximate U-shape. U-shape herein is defined as a downward oriented turn at a bottom side, which turn on either side ends in two legs, which extend upwards. The legs need not be parallel and need not be straight. Thereto little to no tension is locally present in the print medium 5. The downstream support 22 is provided with a clamp 30. The clamp 30 can be moved by means of its actuator 31 between a clamping position and a remote position. In the clamping position, the clamp 30 locally holds the print medium 5 in place by clamping it between the downstream support 22 and the clamp 30. Print medium 5 is fed into the blouse former 20 from the print station 14, thus increasing the size of the blouse when the clamp 30 is in its clamping position (also referred to as 'closed'). Blouse sensors 25, 27 are provided to determine the size of the blouse. Downstream of the blouse former 20, a winder is provided for winding up the print medium 5 onto a take-up roller 33. The take-up roller 33 comprises a drive for rotating the take-up roller 33.
Fig. 1 illustrates the roller printer 1 during a step of loading a new print medium 5. The print medium 5 is unwound from the input roller 2 and extended over the suction chamber assembly 10 towards the take-up roller 33. Initially in Fig. 1, the print medium 5 passes the blouse former 20 without forming a blouse. The blouse former 20 may comprise means for initially letting the leading edge of the print medium pass between the supports 21, 22 without it sinking in between the supports 21,22. For example, a pivotable plate may initially support the print medium and then pivot to allow the print medium to drop in between the supports 21, 22.
In Fig. 2, the leading edge of the print medium 5 has been secured to the take-up roller 33. The roll printer 1 is then configured for winding up the print medium 5. The clamp 30 is actuated to its clamping position, as shown in Fig. 2. The print medium 5 is then locally held between the clamp 30 and the downstream support 22 and can locally not move further.
As printing continues print medium 5 is unspooled from the input roller 2 and fed via the print station 14 into the blouse former 20 by means of the driving roller 8. While the clamp 30 is in its clamping position, this feeding of the print medium 5 increases the size of the blouse 28 in the blouse former 20. The blouse 28 is substantially U-shaped with a bottom turn at its lower side. The blouse 28 provides a decoupling buffer in the print medium 5 which prevents pulling forces from the drive 34 of the take-up roller 33 from disturbing the position of the print medium 5 under the print station 5. Two blouse sensors 25, 27 are provided in the blouse former 20 to determine the size of the blouse 28, as it is preferred to keep the size of the blouse 28 within a predetermined range: if too large the blouse will contact the floor and, if too small, the blouse 28 will reduce or loose its de-coupling function. In Fig. 3, the blouse sensors 25, 27 are optical detectors, such as photo-diodes, positioned at different height to detect passage of the bottom part of the blouse 28. It will be appreciated that any suitable sensors may be applied, such as a camera, a laser distance sensor, etc. Alternatively, the size of the blouse 28 may be calculated from the rotations of different rollers 2, 8, 33. In the example here, the blouse 28 is controlled to maintain its lower portion between the top and bottom blouse sensor 25, 27, with the exception of the start and end of the respective print job.
Fig. 4 illustrates the bottom part of the blouse 28 reaching the bottom portion of its allowed range, as defined by the bottom blouse sensor 25. When the bottom detector 25 detects that blouse 28 is about to drop below the allowed range, the clamp 30 is actuated to move to its remote position (also referred to as 'open'), as shown in Fig. 4. In the remote position, the clamp 30 does not obstruct movement of the print medium 5, which can pass freely over the downstream support 22, though said support 22 exerts some friction, resulting in drag which locally tensions the print medium 5 while winding. After opening the clamp 30, the drive 34 of the take-up roller 33 is activated to start winding up the print medium 5. The take-up roller 33 (when activated) rotates on average faster (in terms of media displacement) than the input roller 2 and the driving roller 8, so that print medium 5 is taken up out of the blouse former 20 and wound onto the take-up roller 33. In consequence, the blouse 28 reduces in size. The bottom position of the blouse effectively moves upwards until it reaches the top blouse sensor 27.
In Fig. 5, winding up the print medium 5 is stopped when the bottom blouse sensor 27 detects that the blouse has reached the top of its allowed range. This detection triggers the actuator 31 to move the clamp 30 to the clamping position, again locally securing the print medium 5 on the downstream support 22. The drive 34 of the take-up roller 33 is also stopped. Subsequently, the blouse 28 begins to increase again and the process in Figs. 3 to 5 is repeated as long as the print job continues. Upon completion of the respective print job, the print medium 5 is pulled tight across the supports 21, 22, allowing the print medium to be cut, for example between the supports 21, 22, which results in the situation as in Fig. 2. Therein, the clamp 30 holds the print medium 5 locally in place, so that cutting does not result in unwinding of the wound up print medium 5 at the take-up roller 33.
The roll printer 1 is configured to operate in two main winding modes. The first winding mode is selected for print media of a relatively medium bending stiffness. Print media of this bending medium stiffness form a first print media type, which generally applies to majority of the print media applied, though it may vary per application of the roll printer 1 and the exact configuration of the roll printer 1. In addition, a second print media type may be applied, which print media type comprises print media with a bending stiffness deviating from the indicated medium bending stiffness. This print media type comprises two sub-types: a first media sub-type which includes print media with a relatively high bending stiffness, which is greater than the respective medium bending stiffness, and a second media sub-type which includes print media with a relatively low bending stiffness, which is smaller than the respective medium bending stiffness. The first media sub-type may include very thick or rigid print media, such as heavy paper, coated paper, etc. The second media sub-type may include light-weight paper, thin foils, etc.
It will be appreciated that bending stiffness can be expressed in any suitable format or units, such as N/m. Preferably bending stiffness is defined as the resistance of a print medium against bending deflection/deformation. It may for example be a function of the Young's modulus, the second moment of area of the print medium's cross-section about a bending axis, and a length of the print medium, specifically when adapted for planar bodies.
In the first winding mode, the drive 34 of the take-up roller 33 is activated only when the clamp 30 is in its remote position. When the clamp 30 is pressed against the print medium 5, the take-up roller 33 is prevented from rotating. The drag from the downstream support 22 during winding with the clamp 30 open is sufficient to achieve tightly wound rolls for this media type. It will be appreciated that while the take-up roller 33 is stationary, power may be applied to the drive 34 to have it exert a torque on the take-up roller 33 to prevent it from rotating due to the tension in the print medium 5. Print media of the first media type can be wound up in this manner, so that it results in a tightly wound and straight roll. It was found that winding up print media of the second print media type in the first winding mode generally would not result in tightly wound rolls. When using the second print media type, rolls would become loosely wound, too tightly wound, and/or damage to the print medium occurred.
It was the insight of the inventors that different bending stiffnesses resulted in different behavior between the blouse and the winder. To address these issues, a distinction was made between the first and second print media types. Since print media of the second print media type have a bending stiffness resulting in winding issues in the first winding mode, a second winding mode is selected in case print media of the second media type are chosen. The second winding mode may be selected manually via user interface 40 by selecting a corresponding winding mode selector 41-43. Fig. 1 illustrates the selection of the first winding mode by activating the first winding mode selector 41. In this first winding mode, the drive 34 of the take-up roller 33 is prevented from rotating when the clamp 30 is in contact with the print medium 5. Alternatively, the selection of the winding mode may be performed automatically e.g. when a certain print medium 5-7 is selected or defined, for example via print job information or when selecting a print medium 5-7 from a pre-defined media catalogue. In the catalogue a winding mode has been defined for each available print medium 5-7.
In the second winding mode, the drive 34 of the take-roller 33 is momentarily activated to rotate the take-up roller 33 to adjust the tension in the print medium 6, 7 between the downstream support 22 and the take-up roller 33. It is the further insight of the inventors that the tension should be dependent on the relatively bending stiffness of the print media 6, 7. This is achieved by the direction wherein the take-up roller 33 is rotated when the clamp 30 is in its clamping position being dependent on the bending stiffness. Print media of the first media sub-type have a relatively high bending stiffness and when these are selected, the roll printer 1 operates in a first winding sub-mode, wherein the drive 34 is controlled to briefly increase the tension in the print medium 6 between the downstream support 22 and the take-up roller 33.
In the first winding sub-mode, the roll printer 1 operates as shown in Figs. 1 to 5, but with an additional step when the situation in Fig. 5 has been reached. This is illustrated in Fig. 6, wherein a stiff print medium 6 with a relatively high bending stiffness is loaded onto the printer 1. During printing, the blouse 28 has been formed as in Figs. 2 to 3, followed by the opening of the clamp 30 and rotating the take-up roller 33 to wind up print medium onto the take-up roller 33. Fig. 6 illustrates that when the blouse 28 has reached a level where it triggers the upper blouse sensor 27, the clamp 30 is closed, so that it presses the stiff print medium 6 onto the downstream support 22. The high bending stiffness of the stiff print medium 6 has caused the stiff print medium 6 to bend away from the shortest path between the downstream support 22 and the take-up roller 33, despite the drag exerted by the downstream support 22 during winding. In the first winding sub-mode of the second winding mode, the drive 34 of the take-up roller 33 is controlled to rotate the take-up roller 33 further in the winding direction to pull straight the bended segment when the clamp 30 has been closed, as indicated in Fig. 7. It will be appreciated that herein the take-up roller 33 is rotated momentarily over a limited angle, sufficient to pull taut the stiff print medium 6 between the clamp 30 and the take-up roller 33. After that, the take-up roller 33 maintains a fixed rotational position until the bottom blouse sensor 25 detects the lower part of the blouse 28, which is followed by the process explained for Figs. 2 to 4. As shown in Fig. 6, the selection of the first winding sub-mode is indicated by its respective selector 42 on the user interface 40.
For the second media sub-type, the inventors determined that after reaching the situation in Fig. 4, the clamp 30 will close, but the tension between the clamp 30 and the take-up roller 33 should be reduced for print media 7 of the second media sub-type. These print media 7 of relatively low bending stiffness may deform or damage under excess tension. In the second winding sub-mode of the second winding mode, the take-up roller 33 is driven opposite to the winding direction to reduce unwind a small amount of low stiffness print medium 7 from the take-up roller 33 to reduce the tension 33 between the take-up roller 33 and the closed clamp 30. This is illustrated in Fig. 9. This opposite rotation when the clamp 30 is closed may be relatively small, so over a limited angle. The angle may be media-dependent, e.g. dependent on its bending stiffness, or a pre-determined angle may be used. After this rotation to adjust the tension, the take-up roller 33 is fixed in its rotational position until the clamp 30 is opened to further wind the print medium 7.
Fig. 10 shows the steps of the method of winding print media 5-7 on the roll printer 1. In step i, the winding mode is determined. The winding mode is selected based on the bending stiffness of the print media 5-7. The winding mode may be selected manually via the user interface 40 or automatically derived from print job information. In case the print medium 5 has a relatively medium or regular bending stiffness, the first winding mode WM1 is selected. Therein, the medium bending stiffness print medium 5 is loaded and attached to the take-up roller 33 as in Figs 1 and 2, followed by the formation of a blouse 28. During printing the steps ii to iv are repeated to keep the blouse 28 between the level defined by the blouse sensors 25, 27. In step ii, the clamp 30 is in its clamping position while the take-up roller 33 is prevented from rotating. Printed medium stiffness print medium 5 is fed into the blouse 28 increasing its size as shown in Fig. 3. This continues until the bottom blouse sensor 25 detects the blouse 28, thereby triggering step iii: the clamp 30 is moved to its remote position and the take-up roller 33 is rotated, so that the medium stiffness print medium 5 is wound up onto the take-up roller 33. Therein, the print medium 5 is wound tightly as it is tensioned due to the drag it experiences from the downstream support 22. It will be appreciated that herein the medium bending stiffness print medium 5 may continue to be fed into the blouse 28 at the same rate as in step ii, but that the take-up roller 33 will rotate sufficiently fast to still decrease the blouse size. Step iii continues until the blouse 28 triggers the top blouse sensor 27. Detection at the top blouse sensor 27 starts step iv, wherein the clamp 30 is moved from its remote position to the clamping position. In addition, rotation of the take-up roller 33 is stopped at the moment the clamp 30 is moved, so that the take-up roller 33 does not rotate while the clamp 30 is closed. Closing the clamp 30 in step iv is directly followed by step ii, wherein the blouse 28 is increased. Steps ii to iv are repeated until completion of the print job. Then, the step ix if tightening the print medium 5 over the supports 21, 22 is performed, leading to the situation in Fig. 2. The input roller 3 does not rotate, preventing print medium from being fed into the blouse 28, so that a winding action as in step iii moves the blouse upwards, but in this case the print medium 5 in the blouse former 20 is allowed to move past the top blouse sensor 27, so that it can be pulled taught. In step x, the taut print medium 5 is then cut by moving a cutting knife between the supports 21, 22. During cutting the clamp 30 is closed to keep the print medium 5 at the take-up roller 33 wound up. An operator or attachment device may subsequently secure the trailing edge to the roll of print medium 5.
When a stiff print medium is selected, the first winding sub-mode WSM1 is activated. The first winding sub-WSM1 mode includes the same steps ii to iv, as explained for the first winding mode WM1. However for these stiff print media 6, the first winding sub-mode WSM1 includes additional steps v and vi. After pressing the clamp 30 onto the print medium 6 in step iv, the take-up roller 33 is rotated over a limited range in step v. In step v, this rotation is in the winding direction, which is the same direction as in step iii. As the clamp 30 holds the print medium 6 locally in place, rotating the take-up roller 33 in step v results in a local tensioning or tightening of the print medium 6 between the clamp 30 and the take-up roller 33, as shown in Figs. 7 and 8. The rotation of the take-up roller 33 while the clamp 30 is closed is limited to a relatively small angle, preferably less than 45 degrees, very preferably less than 30 degrees, even more preferably less than 15 degrees. Step v is followed by step vi, stopping the rotation of the take-up roller 33 while the clamp 30 is closed onto the print medium 6. It will be appreciated that step v may follow directly after step iv, but alternatively it may follow after a certain waiting period. It will further appreciated that steps vi and v may be performed while print medium 6 is fed into the blouse 28. Steps ii to vi are repeated until completion of the print job, followed by tightening as in step ix and cutting as in step x.
When a low stiffness print medium is selected, the second winding sub-mode WSM2 is activated. The second winding sub-WSM2 mode includes the same steps ii to iv, as explained for the first winding mode WM1. In addition, the second winding sub-mode WSM2 includes a step vii of rotating the take-up roller 33 while the clamp 30 is closed and a step viii of stopping rotation of the take-up roller 33 when the clamp 30 is closed. This steps vii and viii are respectively similar to steps v and vi with the difference that the take-up roller 33 is rotated opposite to the winding direction. In step vii, a small portion of the low stiffness print medium 7 is unwound from the take-up roller 33 to locally reduce the tension in said print medium 7 between the clamp 30 and the take-up roller 33. Step viii is a similar stopping step as step vi, but in this case a rotation opposite to the winding direction is stopped. This results in locally reducing the tension in the low stiffness print medium 7, preventing deformation and/or damage due to excess tension. After completing the print job, tightening and cutting in steps ix and x are performed.
Although specific embodiments of the invention are illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations exist. It should be appreciated that the exemplary embodiment or exemplary embodiments are examples only and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents. Generally, this application is intended to cover any adaptations or variations of the specific embodiments discussed herein.
It will also be appreciated that in this document the terms "comprise", "comprising", "include", "including", "contain", "containing", "have", "having", and any variations thereof, are intended to be understood in an inclusive (i.e. non-exclusive) sense, such that the process, method, device, apparatus or system described herein is not limited to those features or parts or elements or steps recited but may include other elements, features, parts or steps not expressly listed or inherent to such process, method, article, or apparatus. Furthermore, the terms "a" and "an" used herein are intended to be understood as meaning one or more unless explicitly stated otherwise. Moreover, the terms "first", "second", "third", etc. are used merely as labels, and are not intended to impose numerical requirements on or to establish a certain ranking of importance of their objects.
The present invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

Claims

A method for winding a print medium (5-7) onto a take-up roller (33) comprising the steps of:
- forming a blouse (28) in the print medium (5-7) upstream of the take-up roller (33);

- clamping the print medium (5-7) by means of a clamp (30) between the blouse (28) and the take-up roller (33), when the print medium (5-7) is fed into the blouse (28) and when the take-up roller (33) is prevented from rotating;

- releasing the clamp (30) when the take-up roller (33) is rotated to wind up print medium (5-7) from the blouse (28),
characterized by the step of rotating the take-up roller (33) to adjust a tension in the print medium (5-7) between the blouse (28) and the take-up roller (33) while clamping the print medium (5-7).
The method according to claim 1, wherein while the clamp (30) engages and fixes the print medium (5-7), the following steps are performed:
- the step of rotating the take-up roller (33) to adjust a tension in the print medium (5-7) between the blouse (28) and the take-up roller (33) while clamping the print medium (5-7); and

- a step of feeding print medium (5-7) into the blouse (28).
The method according to any of the previous claims, wherein while the clamp (30) is disengaged from the print medium (5-7), the following steps are performed:
- rotating the take-up roller (33), so that the blouse (28) is reduced; and

- winding print medium (5-7) onto the take-up roller (33).
The method according to any of the previous claims, wherein a majority or substantially the full print medium (5-7) is wound up while the clamp (30) is disengaged from the print medium (5-7).
The method according to any of the previous claims, further comprising the step of selecting between two winding modes (WM1, WM2), which are:
- a first winding mode (WM1) for a first media type, wherein the take-up roller (33) is prevented from rotating as long as the clamp (30) clamps the print medium (5-7); and

- a second winding mode (WM1) for a second media type, which comprises the step of rotating the take-up roller (33) to adjust a tension in the print medium (5-7) between the blouse (28) and the take-up roller (33) while clamping print medium (5-7).
The method according to claim 5, wherein a bending stiffness of the first media type is different from that of the second print media type.
The method according to claim 5 or 6, wherein the second winding mode comprises a first and a second winding sub-mode (WSM1, WSM2), wherein respectively:
- for the first media sub-type the take-up roller (33) is rotated in a winding up direction as during winding to increase a tension in the print medium (5-7) between the blouse (28) and the take-up roller (33) while clamping print medium (5-7); and

- for the second media sub-type the take-up roller (33) is rotated opposite to the winding direction to decrease a tension in the print medium (5-7) between the blouse (28) and the take-up roller (33) while clamping print medium (5-7).
The method according to any of the claims 5 to 7, wherein a bending stiffness of the first media type greater than that of the second media sub-type and smaller than that of the first media sub-type.
The method according to previous claims, further comprising the step of driving the print medium (5-7) past a print station (14) by means of a driving roller (8) upstream of the print station (14).
The method according to any of the previous claims, further comprising the step of reciprocally moving a carriage (15) over the print medium (5-7) to print an image on the print medium (5-7).
A roll printer (1) configured to performed the method according to any of the claims 5 to 10, further comprising a user interface (40) configured for selecting one of the first and second print modes.