A roll printer comprising a slipping enabler

Abstract

A compact device to prevent or reduce the formation of wrinkles in print media during roll-to-roll printing on a printer comprising an endless transport belt is provided. The printer (1) comprises: - a transporter (7) for transporting a print medium (20, 27) from a feed roller (11) via an upstream roller (12) along a printing assembly (2) to a take-up roller (16), wherein the upstream roller (12) defines a turn in the print medium (20, 27), characterized by a slipping enabler (30) positionable at the upstream roller (12) between the print medium (20, 27) and the upstream roller (12) with during use moving surfaces on opposite sides of the slipping enabler (30), so that the slipping enabler (30) remains substantially stationary while the print medium (20, 27) and the upstream roller (12) move.

Description

BACKGROUND OF THE INVENTION1. Field of the invention

[0001] The invention relates to a roll printer and to a method of printing.2. Description of Background Art

[0002] The invention relates to a roll printer. Roll printers may operate in a roll-to-roll print mode, wherein a print medium is unwound from a feed roller, passed along a printing assembly, and re-wound at a take-up roller. The print medium generally extends upwards from the feed roller towards an upstream roller, around which the print medium is curved onto a horizontal plane and extends towards the printing assembly. The upstream roller may be one of a plurality of support rollers, which support an endless transport belt, which moves the print medium past the printing assembly. It was found that wrinkles could be introduced into the print medium by its passage over the upstream roller.SUMMARY OF THE INVENTION

[0003] It is an object of the invention to provide an improved roll printer, specifically one wherein wrinkling is reduced and / or prevented.

[0004] In accordance with the present invention, a roll printer according to claim 1, a transporter for a roll printer according to claim 12, and a method of printing according to claim 13 are provided.

[0005] The roll printer comprises: a feed roller configured to feed a print medium from a roll; a printing assembly configured to print an image on the print medium fed by the feed roller; a take-up roller configured to take up the print medium printed by the printing assembly;

[0006] The transporter is configured for transporting a print medium along the printing assembly and comprises an upstream roller defining a turn in the print medium.

[0007] The transporter is characterized in that a slipping enabler is positioned at the upstream roller and is configured to support a side of the print medium facing the upstream roller, wherein the slipping enabler remains substantially stationary while the print medium and the upstream roller move.

[0008] It is an insight of the inventor that wrinkles in the print media are caused by local velocities differences between the portion of the print medium over the upstream roller and the portion extending along the printing assembly. It is the further insight of the inventor that the velocity at the upstream roller will be similar if there locally the print medium is substantially and / or significantly decoupled from the forces of the transporter. The inventor further realized that this decoupling can be achieved in a simple and compact manner by positioning a slipping enabler at the upstream roller between the print medium and the transporter, such that the print medium and the transporter can slide along it at the upstream roller.

[0009] The slipping enabler during use is in contact with two moving surfaces on opposite sides of the slipping enabler. One moving surface is formed by the print medium, which is generally on top of the slipping enabler. The other moving surface is formed by the transporter, specifically a portion thereof located at the upstream roller. The other moving surface generally engages the bottom side of the slipping enabler during use. The slipping enabler during use is arranged to remain its position, while allowing the print medium and the transporter to move along it in the vicinity of the upstream roller. The slipping enabler has at least one fixed point, which remains stationary with respect to the moving surfaces. The slipping enabler locally decouples or disengages the print medium from the transporter, locally allowing for different velocities. This allows the path of the print medium to be substantially similar or the same when the slipping enabler is present, as compared to when it would be absent. This results in a compact and low-costs solution to prevent or reduce wrinkles in print media. Thereby the object of the present invention has been achieved.

[0010] More specific optional features of the invention are indicated in the dependent claims.

[0011] In an embodiment, the slipping enabler is in direct contact with the during use moving surfaces, which then slide past the slipping enabler. The slipping enabler contacts the print medium and the transporter, while allowing these to slide past it, while the slipping enabler maintains its position.

[0012] In an embodiment, the moving surfaces are positioned on opposite sides of the slipping enabler during use. The print medium is preferably on a top side of the slipping enabler, while the transporter moves along a downwards facing side of the slipping enabler. The slipping enabler extends between the print medium and the transporter.

[0013] In an embodiment, the turn defined by the upstream roller orients the print medium in a horizontal orientation. Before the upstream roller the print medium preferably extends upwards, while after the upstream roller the print medium moves in a horizontal direction.

[0014] In a preferred embodiment, the transporter further comprises an endless belt extending over a suction chamber assembly, and wherein the slipping enabler is positionable at the upstream roller between the belt and the print medium, so that the slipping enabler remains substantially stationary while the print medium and the belt move. The transporter is formed by an endless suction transport belt, to which the print medium is locally and releasably fixed by suction, so that the print medium can be moved by driving the belt. The belt is supported on rollers, one which is the upstream roller, which defines a turn or bend in the belt. The belt has a finite thickness, which positions the print medium at a distance from the circumference of the upstream roller. The further away from this circumference, the greater the velocity difference with respect to the circumferential velocity of the upstream roller will be. The velocity of the belt after the upstream roller is equal to the velocity of a neutral or middle line of the belt, roughly halfway between the upper and lower surfaces of the belt at the upstream roller. The velocity of the outer surface of the belt at the print medium at the upstream roller will thus be different than that of the interface between the belt and the upstream roller, due to the thickness of the belt. The velocity of the outer surface of the belt is also greater than the velocity of the neutral line, and thus greater than that of the belt and the print medium at the printing assembly. The wrinkling effects of this velocity difference can be reduced or negated by providing the slipping enabler, so that it covers the portion of the belt in contact with the upstream roller.

[0015] In an embodiment, the slipping enabler is positionable between the belt and the print medium, so that it extends in a contact area of the turn, where the print medium would contact the belt in absence of the slipping enabler. In case a belt is applied, the contact area corresponds to at least the area where the upstream roller contacts the belt. The contact area extends preferably over at least the angle of the turn in the print medium at the upstream roller. Preferably, the contact area extends over an angle of at least 90° around an axis of the upstream roller. The slipping enabler does preferably not extend substantially along the during use horizontal portion of the print medium at the print medium support surface. For example, the slipping enabler may not extend beyond the upstream roller in a transport direction of the print medium.

[0016] In an embodiment, the slipping enabler further comprises a slip sheet with a width corresponding to a width of the upstream roller. The print medium is decoupled from the transporter at the upstream over substantially its full width. This is achieved by a slip sheet with a width at least that of the print medium. Preferably, the width of the slip sheet corresponds to and / or scales with that of the upstream roller. Width herein in measured in a lateral perpendicular to the transport direction.

[0017] In an embodiment, the slip sheet is flexible, so that it can conform to a radius of the upstream roller. The slip sheet is deformable or pliable, so that when positioned over the upstream roller, it assumes the local radius of the surface beneath it. Said radius is defined by the transporter, for example by the radius of the upstream roller, optionally plus the thickness of the belt.

[0018] In an embodiment, the slip sheet is formed of a smooth and low frictional material. Both moving surfaces slide along the slip sheet with relatively little friction. Thereto, the surfaces of the slip sheet have been selected to have a low coefficient of friction in the interaction with respective surfaces. Preferably, the slip sheet is formed of a plastic material, for example PVC, PET, polypropene, mylar, etc. It is further preferred that the slip sheet is relatively thin, e.g. less than 5 mm, preferably less than 3 mm, very preferably less than 2 mm, and even more preferably less than 1 mm.

[0019] In an embodiment, the slip sheet is securable to a slip holder, which slip holder is positioned in a V-shaped region, wherein the belt and the print medium are coming together at the upstream roller. The print medium is supplied from a feed roller, which feed roller is remote from the belt. From the feed roller the print medium extends towards the upstream. The belt also extends towards the upstream roller, but at a different angle as compared to the print medium. The belt and the print medium preferably come together at the upstream roller. The slip holder is preferably stationary with respect to the moving surfaces and engages an upstream portion or edge of the slip sheet. The slip holder may comprise one or more fasteners for a quick and easy securing and releasing of the slip sheet. To provide a compact printer, the slip holder is positioned, so that the path of the print medium is substantially the same as to when the slip sheet is absent as compared to when the slip sheet is applied. The slip holder is positioned adjacent the upstream roller upstream of where the print medium first contacts the belt. The slip holder is arranged there in between the print medium and the belt.

[0020] In an embodiment, the printer is configured to operate in a roll-to-roll print mode, wherein the slipping enabler is applied to convey the print medium over the upstream roller and in a rigid print mode, wherein the slipping enabler is arranged remote from the print medium. The printer can be controlled in a roll-to-roll print mode as well as a rigid print mode. In the latter print mode, print media are not supplied from the feed roller, but fed horizontally towards the upstream roller in the form of individual sheets.

[0021] The present invention further relates to a transporter for use in a roll printer the according to any of the previous claims, which transport comprises: an upstream roller defining a turn in the print medium; a slipping enabler positionable at the upstream roller and configured to support the print medium, such that that the slipping enabler remains substantially stationary while the print medium and the upstream roller move.

[0022] The transporter may be configured as in any of the above described embodiments.

[0023] The present invention further relates to a method of printing comprising the steps: transporting a print medium from a feed roller via an upstream roller along a printing assembly to a take-up roller, wherein the upstream roller defines a turn in the print medium.

[0024] The method is characterized by the step of a slipping enabler remaining substantially stationary, while two opposing surface it is in contact with slide past it, wherein one of the opposing surfaces is formed by the print medium and the slipping enabler is positioned at the upstream roller between the print medium and the upstream roller. The path of the print medium during roll-to-roll printing comprises a turn at the upstream roller. At this this turn, the slipping enabler is positioned between the upstream roller and the print medium. This allows the print medium to slip locally while over the upstream roller. Thereby, the velocity of the print medium at the turn is determined by and similar to the velocity of the print medium downstream of the upstream roller. This reduce and or prevents wrinkling. The slipping enabler may be configured as any of the above described embodiments. Preferably, the other moving surface is formed by the transporter at the upstream roller, very preferably by a belt running over the upstream roller.

[0025] 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

[0026] 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, cross-sectional view of a printer in a roll-to-roll print mode; Fig. 2 is an enlarged schematic, cross-sectional view of the printer in Fig. 1; Fig. 3 is an enlarged schematic, cross-sectional view of the printer in Fig. 1 with a slipping enabler in its operational position; Fig. 4 is a further enlarged schematic, cross-sectional view of the respective section in Fig. 2; Fig. 5 is a schematic top-down view of a section of the printer in Figs. 3 and 4; Fig. 6 is a schematic, cross-sectional view of the printer in Fig. 1 in a rigid media print mode; Fig. 7 is a schematic, cross-sectional view of another embodiment of a roll-to-roll printer; and Fig. 8 is a diagram illustrating the steps of a method of printing on the printer in Figs. 1 to 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] 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.

[0028] Figure 1 illustrates a printer 1. The printer 1 comprises a printing assembly 2. The printing assembly 2 comprises a printing carriage 4. The printing carriage 4 is mounted on a support beam 3. The carriage 4 is arranged to move reciprocally along the support beam 3. The print head carriage 4 is provided with one or more printheads. The printheads are preferably inkjet printheads which are arranged for jetting one or more droplets onto a print medium 20. A fixation unit 5 may be provided adjacent to the printing assembly 2. The fixation unit 5 may be provided with one or more emitters 6. The emitter 6 may be configured for emitting energy in the form of radiation and or heat. This facilitates and / or improves the hardening of the ink onto the print medium 20.

[0029] The printer 1 further comprises a transporter 7. The transporter 7 comprises an endless belt 8. The belt 8 is supported on a plurality of rollers 12 to 15. The belt 8 is provided with a plurality of openings 9 which allow air to pass through the belt. 8. Between the upstream roller 12 and the downstream roller 13, the belt 8 defines a print medium support surface 10. The print medium supports surface 10 faces the printing assembly 2. On the opposite side of the belt 8 with respect to the printing assembly 2, a suction chamber assembly 18 is provided. The suction chamber assembly 18 is part of a suction holder 17, which is arranged to hold the print medium 20 against the print medium support surface 10 by means of a negative pressure applied in the suction chamber assembly 18. The negative pressure may be applied to the suction chamber assembly 18 by means of a suction source 19 connected to it. The suction source 19 may be formed by a pump or fan. The belt 8 may be formed of any suitable material, such as plastic or metal. The belt 8 may be provided with the openings 9 by means of punching, perforation, et cetera, or be formed of an inherently porous material, such as a mesh or grid material.

[0030] The transporter 7 is configured to transport print medium 20 from a feed roll 21 to a take-up roll 22. The feed roll 21 is provided on a feed roller 11 on the upstream side of the transporter 7. A take up roll 22 is provided on the downstream side of the transporter 7 on a take up roller 16. The print medium 20 extends from the feed roller 21 to the take up roll 22 via the belt 8. By driving the belt 8 the print medium 20 is transported past the printing assembly 2. during printing the print medium 20 is securely held to the belt 8 by means of the negative pressure so that the two move together.

[0031] In Figure 1, the printer 1 operates in a roll-to-roll print mode wherein the print medium 20 extends as a web between the feed roll 21 and the take up roll 22. In another print mode, the printer 1 may be configured to transport rigid print media such as panels, sheets, cardboard, thick plates.

[0032] Figure 2 illustrates a close up view of the upstream roller 12 with the belt 8 and the print medium 20. In the straight section over the suction chamber assembly 18, the belt 8 and the print medium 20 move at the same first velocity V1. The velocity V1 is controlled by the upstream roller 12 which is driven at a predetermined speed. Thereto, the upstream roller 12 may be provided with a drive or motor. Alternatively or similarly, the downstream roller 13 may be provided with a drive or motor. As shown in Figure 2, the upstream roller 12 is driven with a circumferential velocity V3. Due to the thickness of the belt 8, the velocity V1 at the neutral line NL of the belt 8 is greater than that of the circumferential velocity V3. The velocity V2 at the outer surface of the belt 8 is greater than the velocity V1 at the neutral line NL. The inner surface of the belt 8 in consequence moves with the upstream roller 12 at the third velocity V3. The outer surface of the belt 8 however, moves at a greater velocity V2, while the neutral line NL moves an the first velocity V1 in between the second and third velocities V2, V3. This is a consequence of the finite thickness of the belt 8. The effective radius of the outer surface of the belt 8 is greater than that of the inner surface of the belt 8 with respect to the rotation axis of the upstream roller 12. As a result, the outer surface of the belt 8 moves at a slightly greater velocity V2 than its inner surface (which moves at the third velocity V3). The print medium 20 at the upstream roller 12 also moves there at the greater velocity V2. Where the belt 8 leaves the upstream roller 12, the velocity of the print medium 20 returns to the first velocity V1, which is the velocity V1 of the neutral line NL. Locally the print medium 20 is slowed down. As illustrated in Figure 2, this may result in a ply 23 in the print medium 20 at the position where the belt 8 leaves the upstream roller 12. The ply 23 is the result of material of the print medium 20 accumulating at the indicated position. This ply 23 has formed as a wrinkle in the print medium 20. The ply 23 is then transported over the suction chamber assembly 18 to the printing assembly 2. There this ply 23 could result in a print artifact and / or contact with the printheads.

[0033] Figure 3 illustrates the slip holder 30 being positioned between the belt 8 and the print medium 20. The slip holder 30 extends between the belt 8 and the print medium 20 in at least the area wherein in Figure 2, the print medium 20 was in contact with the belt 8 at the upstream roller 12. The slip holder 30 comprises a slip sheet 31, which is connected to a slip holder 32. The slip holder 32 is connected to a frame of the printer 1. The slip holder 32 is stationary during use. The slip sheet 31 is secured to the slip holder 32, so that movement of the slip sheet 31 with the belt 8 is prevented. The slip sheet 31 is preferably formed of a flexible, low friction material. The slip sheet 31 is able to conform to the radius of the belt 8 at the upstream roller 12 in the contact area CA. The surface of the slip sheet 31 is so that the print medium 20 is able to slip over it with little or no resistance. In addition, the belt 8 is able to slip underneath the slip sheet 31 with little to no friction. The slip sheet 31 may be formed of any suitable material, such as a plastic or metal sheet. Other suitable materials such as foils or composite materials may be applied as well.

[0034] The slip sheet 31 decouples movement from the print medium 20 from that of the belt 8 at the upstream roller 12. This allows the print medium 20 at the upstream roller 12 to move with a different velocity than that of the outer surface of the belt 8. In consequence, at the upstream roller 12, the print medium 20 moves with the first velocity V1, whereas the outer surface of the belt 8 still moves with the greater velocity V2. The velocity of the print medium 20 over the upstream roller 12 thus matches the velocity V1 of the print medium 20 at the straight section over the suction chamber assembly 18. At the respective turn and beyond it, the velocity of the print medium 20 is thus essentially constant and equal to the first velocity V1. No material of print medium 20 then accumulates where the belt 8 leaves the upstream roller 12. The formation of plies 23 is thus prevented. The print medium 20 passes to the printing assembly 2 free of wrinkles.

[0035] It will be appreciated that the slip sheet 31 extends over preferably the full width of the print medium 20. In one example, the slip sheet 31 has a width substantially equal to that of the upstream roller 12. The slip holder 32 may be formed of any suitable holding device such as a frame fixation unit, clamp, etc.

[0036] Figure 4 illustrates an enhanced close-up of the area around the upstream roller 12 with the belt 8 extending over it. The inner surface of the belt 8 is in contact with the outer circumferential surface of the upstream roller 12. As shown in Figure 4, the outer surface of the belt 8 is stretched with respect to the inner surface. The outer surface of the belt 8 moves at the greater velocity V2 as compared to its inner surface which travels at the third velocity V3. The neutral line NL in between the upper and lower surfaces of the belt 8 moves at the first velocity V1, which determines the velocity V1 of the belt 8 and the print medium 20 after the upstream roller 12 and at the printing assembly 2. At the upstream roller 12, the slip sheet 31 is in direct contact with the belt. 8. The low friction surface of the slip sheet 31 allows the belt 8 to slip underneath it. The slip sheet 31 itself is held in place by the slip holder 32. The print medium 20 slips over the outer surface of the slip sheet 31. The inner surface of the slip sheet 31 facing the upstream roller 12 is in direct contact with the outer surface of the belt 8. While the outer surface of the belt 8 slips past the inner surface of the slip sheet 31 at the second velocity V2, the print medium 20 slips over the outer surface of the slip sheet 31 at the first velocity V1. Herein the slip sheet 31 is in direct contact on opposite sides with both the belt 8 and the print medium 20. The slip sheet 31 is preferably a smooth sheet which allows the print medium 20 and the belt 8 to slip past it with minimum friction in the contact area CA. The slip sheet 31 is further flexible so that it confirms to the radius of the outer surface of the belt 8. In addition, the slip sheet 31 is preferably smooth and flexible so that it does not damage or deform the print medium 20.

[0037] Fig. 5 shows the printer 1 from above. The print medium 20 extends from the feed roller 11 to the belt 8. On the left side of Fig. 5 the print medium 20 extends upwards in the height direction Z. Once the print medium is on the belt 8 it becomes parallel to the horizontal plane defined b the transport direction X and the lateral direction Y. In Fig. 5, the slip holder 32 is positioned slightly upstream of the respective side of the belt 8. From the slip holder 32, the slip sheet 31 initially extends upwards onto the belt 8 where it is inserted between the belt 8 and the print medium 20. The slip sheet 31 extends over the belt 8 from the upstream side to just beyond the upstream roller 12. The slip sheet 31 remains in position, as it is secured by the slip holder 32. The slip sheet 31 preferably ends just upstream of the suction chamber assembly 18. Alternatively, the slip sheet 31 may extend over a section of the suction chamber assembly 18, where the suction is very low or turned off.

[0038] Fig. 5 illustrates the relative widths of the different components in the lateral direction Y. the feed roller 11 and the upstream roller 12 have the largest width, so to support the belt 8. The belt 8 determines the maximum, allowed width of the print media 20, which preferably do not exceed the width of the belt 8. Generally, the belt 8 is selected to be slightly wider than the widest print medium 20. The width of the slip sheet 31 is preferably at least as wide as that of the applied print medium 20. In the example in Fig. 5, the slip sheet 31 is at least the width of the widest print medium 20 and no wider than the belt 8.

[0039] In Figures 1 to 5, the printer 1 operates in a role to role print mode. As shown in Figure 6, the printer 1 may also be configured to operate in a second print mode. In the second print mode, the transporter 7 is arranged to transport rigid print media. Examples of rigid print media 25 may be panels, boards, cardboard, etcetera. In the second print mode in Figure 6, the feed roll 22 is not utilized. In addition, the slip sheet 31 has been removed from the slip holder 32. Preferably the slip sheet 31 is releasably connected to the slip holder 32. The slip holder 32 may provide releasable fasteners which allow for a quick and easy removal of the slip sheet 31. Examples of such fasteners are click mechanisms, magnetic fasteners, clamps, etcetera. It will be appreciated that the slip holder 32 itself may also be entirely removable. This allows for fast and easy switching between the roll-to-roll print mode and the rigid print mode. It will be appreciated that the slip enabler 30 allows for a compact and low-cost configuration of the printer 1. The slip sheet 31 as well as the slip holder 32 may be formed of low-cost materials. The footprint of the printer 1 is also not increased substantially by the addition of the slip enabler 30. The slip holder 32 is positioned adjacent the upstream roller 12 in a V-shaped area directly upstream of the contact area CA. The V-shape is defined by the print medium 20 and the belt 8 extending towards one another. The print medium 20 extends substantially vertically while the belt 20 is locally inclined. It will be appreciated that all the respective descriptions are when viewed in a lateral direction perpendicular to a transport direction of the belt. The lateral direction is further preferably horizontal during use.

[0040] Figure 7 illustrates another embodiment of a printer 100. In Figure 7 the transporter 107 does not extend the belt 108 over the upstream roller 112, in contrast to e.g. in Figure 1. In Figure 7, the print medium 27 is in direct contact with the print medium support surface 110 formed by the suction chamber assembly 118. In this example, the top surface of the suction chamber assembly 118 is provided with openings to apply a negative pressure to the print medium 27 via the belt 108. The print medium 27 is supported directly on the suction chamber assembly 118. In Figure 7, a relatively thick print medium 27 has been provided on the printer 100. A print medium 27 of such a relatively great thickness may experience similar issues as discussed for Figure 2. To avoid the formation of plies 23, a slipping enabler 30 is positioned between the upstream roller 112 and the print medium 27. This allows the print medium 27 to move at a different velocity than the outer surface of the upstream roller 112. As explained previously, this avoids the formation of plies and wrinkles in the print medium 27. The slipping enabler 30 may be configured similarly to any of the above described embodiments.

[0041] Fig. 8 illustrates the step of a method of printing. In step i, it is determined that the printer 1 is to operate in a roll-to-roll print mode. In the roll-to-roll print mode, the print medium 20 is provided in roll or web form and is unwound from the feed roll 21 to the take-up roll 22. In between these rolls 21, 22, the print medium 20 extends over the print medium support surface 10, where it is printed by the printing assembly 2. Alternatively, the printer 1 may operate in a rigid print mode, wherein the print media are provided in sheet form, such as for example panels, boards, etc. In the rigid print mode, the rolls 21, 22 are idle or not used.

[0042] In step ii, when in the roll-to-roll print mode, it is determined whether the slipping enabler 30 is required for the respective print job. This may be done e.g. based on media type information prescribed in the print job. In case a print medium requiring the slipping enabler 30 is required, the operator may be informed by means of a prompt on a user interface connected to the printer 1. The prompt instructs the operator to check for the presence of the slipping enabler 30 in the printer 1. In the roll-to-roll print mode, the upstream roller defines a turn in the path of the print medium 20.

[0043] In step iii, the slipping enabler 30 is enabled in the printer 1. In case, the slip sheet 31 was not previously present, the slip sheet 31 is mounted onto the slip holder 32. The slip sheet 31 may be locked, clamped, or otherwise secured to the slip holder 32. The slip sheet 31 is then positioned so that it extends upwards and over the upstream roller 12. Preferably, the slip sheet 31 is sufficiently long, so that it remains in position over the upstream roller 12 despite gravity.

[0044] In step iv, the print medium 20 is loaded and brought towards the print medium support surface 10 and consequently to the take-up roller 16. The print medium 10 is therein positioned on and over the slip sheet 31 at the upstream roller 12. The tension in the print medium 10 forces the slip sheet 31 in the direction of the upstream roller 12. In the example in Fig. 3, the slip sheet 31 is inserted directly between the belt 8 and the print medium 20, while in Fig. 7 the opposite sides of the slip sheet 31 directly contact respectively the upstream roller 112 and the print medium 27.

[0045] In step v, printing is started, which includes moving the print medium 20 past the printing assembly 2. Where in Fig. 3, the print medium 20 is moved by being held to the belt 8 via a negative pressure, in Fig. 7, the print medium 27 is pulled by means of a downstream roller and / or the take-up roller.

[0046] Step v comprises step vi, which is the slipping of the slip sheet 31 with respect to the print medium 20. The material of the slip sheet 31 is selected, so that it has a low frictional interaction with the print medium 20. Preferably, a smooth, plastic foil is used, which allows the print medium 20 to easily slide over it. Similarly, the slip sheet 31 allows its underlying surface to slip past it as well. During printing, the position of the slip sheet 31 is fixed by means of the slip holder 32, while the respective surfaces in contact with the top and bottom surfaces of the slip sheet 31 move. In Fig. 3, the belt 8 slippingly moves along the slip sheet 31, while in Fig. 7 the upstream roller 12 slides along the bottom surface of the slip sheet 31 in a cyclic motion. It is noted that the movement of the print medium 20 and the other moving components may be step-wise or continuous. This continues until printing has been completed in step x. The process may then be repeated from step i for a new print medium.

[0047] In case in step ii, it is determined that the slipping enabler 30 is not required, then the slipping enabler 30 in step vii is removed or its absence it confirmed. The slip sheet 31 may therein be removed from the slip holder 32, while the slip holder 32 remains mounted in the printer 1. Preferably, the removal is swiftly performed by releasing the lock, clamp, or other securing mechanism fixing the slip sheet 31 to the slip holder 32. It will be appreciated that if in step i, it is determined that the print 1 will operate in its rigid print mode, the workflow proceeds directly to step iii.

[0048] In step viii, print media not requiring the slipping enabler 30 are loaded. Such media may for example be the rigid sheets 27 shown in Fig. 6. Alternatively or additionally, there may be certain roll media that do not require the slipping enabler 30. This may include roll media not compatible with use of the slipping enabler 30.

[0049] In step ix the print media are respectively transported and printed without contact with the slip sheet 31. This continues until the print job is completed in step x, whereafter the process may be repeated from step i.

[0050] 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.

[0051] 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.

[0052] 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.Reference numbers

[0053] 1, 100Printer 2Printing assembly 3Support beam 4Carriage comprising at least one printhead 5Fixation unit 6Emitter 7, 107Transporter 8, 108Belt 9Plurality of openings 10, 100Print medium support surface 11Feed roller 12, 112Upstream roller 13Downstream roller 14First support roller 15Second support roller 16Take-up roller 17Suction holder 18, 118Suction chamber assembly 19Suction source 20First print medium (web) 21Feed roll 22Take-up roll 23Plie 25Second print medium 27Third print medium (thick web) 30Slipping enabler 31Slip sheet 32Slip holder V1First velocity V2Second velocity V3Third velocity NLNeutral line

Claims

1. A roll printer (1) comprising: - a feed roller (11) configured to feed a print medium (20, 27) from a roll; - a printing assembly (2) configured to print an image on the print medium fed by the feed roller (11); - a take-up roller (16) configured to take up the print medium (20, 27) printed by the printing assembly (2); - a transporter (7) configured for transporting the print medium (20, 27) along the printing assembly (2) and comprising an upstream roller (12) defining a turn in the print medium (20, 27), characterized in that a slipping enabler (30) is positioned at the upstream roller (12) and is configured to support a side of the print medium (20, 27) facing the upstream roller (12), wherein the slipping enabler (30) remains substantially stationary while the print medium (20, 27) and the upstream roller (12) move.

2. The roll printer (1) according to claim 1, further comprising a slip holder (32) which holds the slipping enabler (30) stationary while the print medium (20, 27) and the upstream roller (12) move with respect to the slipping enabler (30).

3. The roll printer (1) according to any of the previous claims, wherein the slipping enabler (30) is in direct contact with the during use moving surfaces, which then slide past the slipping enabler (30).

4. The roll printer (1) according to any of the previous claims, wherein the transporter (7) comprises an endless belt (8) extending over a suction chamber assembly (18), and wherein the slipping enabler (30) is positionable at the upstream roller (12) between the belt (8) and the print medium (20, 27), so that the slipping enabler (30) remains substantially stationary while the print medium (20, 27) and the belt (8) move.

5. The roll printer (1) according to claim 4, wherein the slipping enabler (30) is positionable between the belt (8) and the print medium (20, 27), so that it extends in a contact area (CA) of the turn, where the print medium (20, 27) would contact the belt (8) in absence of the slipping enabler (30).

6. The roll printer (1) according to claim 5, wherein the contact area (CA) extends over an angle of at least 90° around an axis of the upstream roller (12).

7. The roll printer (1) according to any of the previous claims, wherein the slipping enabler (30) comprises a slip sheet (31) with a width corresponding to a width of the upstream roller (12).

8. The roll printer (1) according to claim 7, wherein the slip sheet (31) is flexible, so that it can conform to a radius of the take-up roller (12).

9. The roll printer (1) according to claim 7 or 8, wherein the slip sheet (31) is formed of a smooth and low frictional material.

10. The roll printer (1) according to claim 2 and any of the claims 7 to 9, wherein the slip sheet (31) is securable to the slip holder (32), which slip holder (32) is positioned in a V-shaped region, wherein the belt (8) and the print medium (20, 27) are coming together at the upstream roller (12).

11. The roll printer (1) according to claim any of the previous claims, wherein the printer (1) is configured to operate in a roll-to-roll print mode, wherein the slipping enabler (30) is applied to convey the print medium over the upstream roller (12) and in a rigid print mode, wherein the slipping enabler (30) is arranged remote from the print medium (25).

12. A transporter (7) for use in a roll printer (1) the according to any of the previous claims, which transport (7) comprises: - an upstream roller (12) defining a turn in the print medium (20, 27); - a slipping enabler (30) positionable at the upstream roller (12) and configured to support the print medium (20, 27), such that that the slipping enabler (30) remains substantially stationary while the print medium (20, 27) and the upstream roller (12) move.

13. A method of printing comprising the steps: - transporting a print medium (20, 27) from a feed roller (11) via an upstream roller (12) along a printing assembly (2) to a take-up roller (16), wherein the upstream roller (12) defines a turn in the print medium (20, 27), characterized by the step of a slipping enabler (30) remaining substantially stationary, while two opposing surface it is in contact with slide past it, wherein one of the opposing surface is formed by the print medium (20, 27) and the slipping enabler is positioned at the upstream roller (12) between the print medium (20, 27) and the upstream roller (12).

14. The method according to claim 13, wherein the slipping enabler (30) comprises a slip holder (32) which holds a slip sheet (31) stationary while the print medium (20, 27) and the upstream roller (12) move with respect to it.

Images