Removable wiper unit for print head maintenance unit

Abstract

To improve a print head maintenance operation for a printer including a wiper unit.SOLUTION: A wiper unit 70 includes: a housing 90; and a plurality of rollers 74 to 81, of which two rollers 74 and 81 are constituted to hold rolls 73, 82 of a rolled-up wiper medium 72 and the remaining rollers 75 to 80 of the plurality of rollers 74 to 81 define a path for conveying the wiper medium 72 between the two rollers 74 and 81. The path defined by the rollers 74 to 81 has negative bending and the negative bending extends at least partially outside the housing 90.SELECTED DRAWING: Figure 15

Description

[Technical Field]

[0001] The present invention relates to a wiper unit for a printhead maintenance unit of a printer, and to a printer equipped with such a wiper unit. [Background technology]

[0002] Printers, particularly sheet printers, may include printhead arrays, commonly referred to as pagewide arrays. Such arrays include multiple printheads extending over a print medium support surface. A transport mechanism is provided for moving the print medium along the printhead array during continuous operation as the printheads eject ink droplets onto the print medium to form an image. The printheads are stationary during ejection and define a print area spanning the width of the print medium. Droplets are ejected from nozzles located in one or more nozzle plates within the printhead array. During operation, ink or other contaminants may accumulate on the nozzle plate, potentially preventing reliable ejection from the nozzles. For example, nozzles may become (partially) blocked, or droplet size or trajectory may be affected by interaction with accumulated ink as droplets exit their respective nozzles. It is known to perform periodic or general maintenance of printhead arrays to at least partially clean one or more nozzle plates. Cleaning can be performed in a variety of ways, such as wiping, spraying, ultrasonic cleaning, suction, etc. It is also known to provide a maintenance unit or station adjacent to the print medium support surface for performing maintenance. When maintenance is required, the printhead array is moved to the location of a maintenance unit where one or more cleaning actions are performed.

[0003] In particular, the nozzle plate may be wiped clean by swiping a wiper medium across the printhead array. It is known to provide the wiper medium in a roll, which is unspooled to provide a constantly clean wiping surface for the nozzle plate. When the roll is depleted, replacement is required. Summary of the Invention

[0004] SUMMARY OF THE INVENTION It is an object of the present invention to improve printhead maintenance operations for printers, particularly printers equipped with wiper units.

[0005] According to the present invention, there are provided a wiper unit for a maintenance unit of a printer as set forth in claim 1 and a print head maintenance unit as set forth in claim 15. The wiper unit is - housing; - a plurality of rollers, two of which are configured to hold a roll of wound up wiper medium, and the remaining rollers define a path for transporting the wiper medium between the two rollers.

[0006] The path defined by the rollers comprises a negative curvature, the negative curvature being characterized by extending at least partially outside the housing.

[0007] Two rolls may be present inside the housing, on an unwind roller and a take-up roller, respectively. The wiping medium is unspooled from the unwind roller to the take-up roller via a path determined by multiple rollers. In the wiping section, the wiping medium extends outside the housing, preferably above the wiper unit during use. Furthermore, the wiper unit exposes a portion of the wiping medium in the wetting section, where wetting fluid may be applied to the wiping medium via a wetter provided in the printhead maintenance unit. The negative bend bends inward deeper into the housing toward the center of the bend. This results in a compact embodiment that can be quickly and efficiently loaded and unloaded from the printhead maintenance unit. This achieves the objectives of the present invention.

[0008] More specific optional features of the invention are set out in the dependent claims.

[0009] In embodiments, the portion of the negative curvature that extends at least partially outside the housing faces a wiping section of the path where the wiper medium contacts the printhead array, where the wiper medium forms the highest point of the wiper unit during use. The negative curvature curves toward the side of the wiper unit where the wiping section is located.

[0010] In an embodiment, the rollers define a substantially Z-shaped section in the path of the wiper media, the Z-shape having a negative curvature. An upper leg of the Z-shape in use extends toward the wiping section. A sloped middle leg of the Z-shape preferably forms the wetting section.

[0011] The negative curvature is defined by three rollers arranged such that the path of the wiper media extends toward the wiping section of the path between a first pair of the three rollers and away from the wiping section between a second pair of the three rollers, In the Z-shape, the middle leg of the Z faces the wiping section, while the bottom leg in use faces the opposite way, preferably facing the take-up roller at the end of the path.

[0012] In an embodiment, the housing includes a curved portion that curves away from the negative bend in the path of the wiper medium on the outside of the housing. Near the exposed portion of the negative bend, a recess is provided in the side plate of the housing so that the exposed portion is out of the housing when viewed in a direction parallel to the axis of the roller. Thus, the individual exposed wetted sections of the wiper medium are easily accessible to the wetter.

[0013] In an embodiment, the wiper unit further comprises a force pinch mechanism, the force pinch mechanism comprising: - at least one roller among the rollers (75-77), - pivotable relative to the housing, - It is pre-tensioned to provide a substantially constant tension to the wiper medium during use.

[0014] The forcing pinch mechanism ensures a constant and stable force driving the wiping section against the printhead array. The wiping section is preferably defined by at least one roller on the forcing pinch mechanism. The forcing pinch mechanism can pivot, so that the at least one roller moves away from or toward the printhead array during use. During use, the wiper medium is tensioned on the at least one roller, driving it away from the printhead array. The forcing pinch mechanism is pre-tensioned with a force that is, on average, greater than the force exerted by the wiper medium, so that the at least one roller is driven against the printhead array. Preferably, the forcing pinch mechanism is also pre-tensioned with a force that, during use, directs the at least one roller away from the printhead array in the event of a loss of tension in the wiper medium. This latter pre-tension is less than the first-mentioned pre-tension, so that the resulting total pre-tension is biased toward the printhead array.

[0015] In an embodiment, at least one roller is a toothed roller, and the teeth of the toothed roller are configured to directly contact the wiper medium. The toothed roller forms a wiping section where the wiper medium is brought into contact with the printhead array. The teeth may be continuous, like a gear, or may be provided in a pattern. The free ends of the teeth are spaced apart from each other so that the wiper medium is not compressed thereat, allowing for efficient capture and retention of fluids, including wetting fluid, ink, and other (liquid) contaminants. The at least one roller may be formed of any suitable material, such as rubber, plastic, metal, etc.

[0016] In an embodiment, the plurality of rollers comprises convex rollers configured to define a substantially Z-shaped curve in the path and to drive the wiper medium toward the centerline of the path. The convex rollers are mounted such that the wiper medium is always aligned toward the middle of the path, thereby preventing the wiper medium from exiting the path.

[0017] In an embodiment, the wiper unit further comprises a lamella roller comprising a plurality of spaced apart thin plates. Downstream of the wiping section, the lamella roller receives the wiped wiper medium across the printhead array. The lamella roller guides the wiped / soiled wiper medium to a take-up roller. The thin plates exert a force only locally on the wiped / soiled wiper medium with a substantially line contact. This prevents or reduces fluid from being forced out of the wiper medium.

[0018] In an embodiment, the wiping medium further includes a locking mechanism removably securable onto the take-up roller of a number of rollers. The locking mechanism includes a cylindrical body insertable into the take-up roller and a locking protrusion provided on each hinge plate. The hinge plate is configured to drive each locking protrusion into a locking opening of the take-up roller to secure the locking mechanism to the take-up roller. The roll of the take-up roller needs to be replaced when it reaches its capacity. Replacement is preferably performed quickly and efficiently. The individual rolls also contain wiper fluid contaminated with ink or other components and should therefore be handled with appropriate care. The locking mechanism secures the roll onto the take-up roller during use. The locking protrusion forms a click mechanism with an opening in the take-up roller, so that the locking mechanism is secured when the locking protrusion clicks into the opening. The locking mechanism can be easily released by moving the hinge plate.

[0019] In an embodiment, the locking mechanism includes a flange member extending radially beyond the body and the fixed projection, such that the flange can be locked between the fixed projection and the flange member. In use, the flange is provided on one side of the roll on the take-up roller. The flange includes a central opening through the cylinder into which the lock is inserted. In another embodiment, the hinge plate extends past the flange member in the axial direction defined by the cylindrical body, and the flange member is wider than and cannot pass through the central opening. The flange is held in place between the flange member and the fixed projection, and the fixed projection acts as a click mechanism, snapping into place on the flange after passing through the central opening.

[0020] In an embodiment, the locking mechanism further comprises a rotation handle on the flange member for rotating the locking mechanism. The hinge plates extend past the flange member and are arranged so that they can be pressed toward each other using one hand to thereby release the locking mechanism. Using the rotation handle, the hinge plates can be placed into a preferred release position.

[0021] In an embodiment, a release mechanism is provided on the housing, the release mechanism comprising opposing pressing members arranged to bring the free ends of the hinge plates together to release the locking mechanism from the take-up roller. By bringing the release members together, the hinge plates are pressed together, thereby releasing the locking mechanism. Because the release mechanism is on the housing, the housing does not need to be opened or removed to release the locking mechanism.

[0022] In an embodiment, the release mechanism comprises an elastically deformable ring having two opposing pressure members, such that in the absence of pressure on the pressure members, the ring returns to its rest state and the pressure members are driven apart, not interfering with the hinge plates, so that the locking mechanism remains securely locked.

[0023] In an embodiment, the wiper unit is formed as a cassette that is removably mountable in a holding portion of the printhead maintenance unit, such that the cassette can be quickly placed in or removed from the printhead maintenance unit.

[0024] The present invention further relates to a printhead maintenance unit that uses the above-described wiper unit in any of its embodiments.

[0025] Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. [Brief explanation of the drawings]

[0026] The present invention will become more fully understood from the detailed description given hereinafter and the accompanying drawings, which are given by way of example only and are therefore not limiting of the invention. [Figure 1] 1 is a schematic cross-sectional view of a printer having a printhead maintenance unit. [Figure 2] FIG. 2 is a top view of the printer of FIG. 1 with the printhead maintenance unit in its rest position. [Figure 3] FIG. 2 is a top view of the printer of FIG. 1 with the printhead maintenance unit moving laterally through its operating range. [Figure 4] FIG. 4 is a detailed perspective view of the print head maintenance unit of FIGS. 1 to 3. [Figure 5] FIG. 5 is a detailed perspective view of a drive assembly for moving the printhead maintenance unit of FIG. 4. [Figure 6]FIG. 10 is a detailed side view of the drive assembly with the printhead maintenance unit in the wiper unit loading position defined by a raised rack section. [Figure 7] FIG. 10 is a detailed side view of the drive assembly with the printhead maintenance unit's wetter in a lowered, spaced apart wetter position defined by the lower rack section. [Figure 8] FIG. 8 is an enlarged side view of the first rack segment of the drive assembly in the situation of FIG. 7. [Figure 9] FIG. 8 is an enlarged side view of the cam mechanism of the drive assembly in the situation of FIG. 7. [Figure 10] FIG. 10 is a detailed side view of the drive assembly with the wetter in a further lowered and spaced apart wetter position defined by the lower rack section. [Figure 11] FIG. 10 is a detailed side view of the drive assembly with the wetter in a wetting position defined by a run-out rack section. [Figure 12] FIG. 10 is a further detailed perspective view of a drive assembly for moving the printhead maintenance. [Figure 13] FIG. [Figure 14] FIG. 2 is a side view of the wiper unit with a portion of the housing removed. [Figure 15] FIG. [Figure 16] FIG. 4 is a perspective view of a forced pinch mechanism of the wiper unit. [Figure 17] FIG. 2 is an exploded perspective side view of the wiper unit. [Figure 18] FIG. 2 is a perspective view of a lamella roller of the wiper unit. [Figure 19] FIG. 4 is a perspective view of a locking mechanism of the wiper unit. [Figure 20] FIG. 4 is a side view of the locking mechanism of the wiper unit. [Figure 21] FIG. 2 is a perspective view of a flange of the wiper unit. [Figure 22]FIG. 10 is a side view of the locking mechanism engaged with the take-up roller of the wiper unit. [Figure 23] FIG. 2 is a perspective view of a release mechanism of the wiper unit. DETAILED DESCRIPTION OF THE INVENTION

[0027] The present invention will now be described with reference to the accompanying drawings, wherein the same reference numerals are used throughout the several views to identify the same or similar elements.

[0028] Printhead maintenance on the print media support surface FIG. 1 shows a sheet printer 1. A sheet is fed from an input module 2 into a transport path 3. The transport path 3 transports the sheet past a printhead array 5, which includes multiple printhead units arranged next to each other in a transport direction X. The transport path 3 below the printhead assembly 5 is formed by an endless belt 6. The belt 6 is provided with openings so that negative pressure can be applied to the sheet via suction chambers 7. Downstream of the printhead assembly 5, the transport path 3 passes through a fuser unit 8. The fuser unit 8 is configured to strengthen the liquid ink that solidifies on the sheet. The fuser unit 8 includes one or more emitters therein for emitting heat or energy, such as heat, heated air, or radiation, toward the sheet. The fuser unit 8 faces a transport belt 10 with corresponding suction boxes 9. Downstream of the fuser unit 8, an output switch 13 is provided for selectively directing the sheet toward an output module 14 or to a duplex path 11. The fully printed sheet is passed to the output module 14. Sheets requiring duplex printing are passed to a duplex path 11 where they are inverted by an inverter device 12. The inverted sheets are then inserted at an input switch 4 so that they can return to the printhead assembly 5.

[0029] A printhead maintenance unit 20 is provided adjacent to the printhead array 5. The printhead maintenance unit 20 is configured to clean the printheads in the printhead array 5. Each printhead includes a nozzle plate with nozzles formed therein, through which marking fluid or ink is ejected. Marking fluid may accumulate and remain on the nozzle plate, which can affect reliable droplet ejection, particularly if the marking fluid accumulates around or at the nozzle. The maintenance unit 20 is configured to at least partially remove the accumulated marking fluid from the nozzle plate. Additionally, the maintenance unit 20 may include a wiper assembly that can be moved along the printhead array to wipe the nozzle plate. However, it will be understood that other maintenance devices, such as a sprayer, brush, ultrasonic cleaner, etc., may be applied instead of wiping.

[0030] FIG. 2 shows the maintenance unit 20 in its rest position R. The rest position is beside the printhead assembly 5 in the lateral direction Y, which is perpendicular to the transport direction X and lies in the plane of the transport path 3. The transport path 3 is defined by the belt 6, which also forms the print medium support surface. The printhead array 5 is a so-called page-wide printhead array, which defines an operating range W. The operating range W preferably covers most of the width of the belt 5 in the lateral direction Y. In its rest position R, the maintenance unit 20 is adjacent to the printhead assembly 5, preferably within 10 to 20 centimeters, but does not interfere with the jetting operation of the printhead array 5.

[0031] FIG. 3 shows the maintenance unit 20 moving in the lateral direction Y along the printhead assembly 5. The maintenance unit 20 moves out of a rest position R and into an operating range W. The maintenance unit 20 is configured to move along the entire operating range W to wipe all of the nozzles in the printhead array 5. This results in a compact structure because the dimensions of the maintenance unit 20 in the lateral direction Y are generally smaller than the dimensions of the printhead array 5. During wiping, the printhead array 5 is stationary and has the same lateral position as during printing. The range of movement of the maintenance unit 20 overlaps and / or is similar to the print range in which the printhead assembly 5 is arranged to print.

[0032] FIG. 4 is a more detailed view of the maintenance unit 20. The maintenance unit 20 comprises a wetter 22 configured to hold a plurality of wiper units 70. Although only a single wiper unit 70 is shown in FIG. 4, it will be understood that a similar wiper unit 70 may be provided at each of the wiper unit holding locations. Each wiper unit location is provided with an individual wetting device in the form of a wetting roller 24. The wetter 22 is provided with a wetting fluid channel extending in the conveying direction X. Wetting fluid flows through the wetting fluid channel so that it is provided to each individual wetting roller 24. A wetting fluid source (not shown), for example a fluid reservoir with a pump, is connected to the wetting fluid channel.

[0033] A separate wiper unit 70 is provided at the leftmost wiper unit location. The wiper unit 70 includes a wiper medium 72, such as tissue, sheet, or paper, for cleaning the nozzle plate. In FIG. 4 , the wiper medium 72 is provided in roll form inside the wiper unit 70 so that it can be unspooled during wiping to prevent smearing of marking fluid on the nozzle plate. The wiper unit 70 can be fixed to the wetter 22 so that it moves together with the wetter 22. A drive assembly 30 is provided for moving the wetter 22 and the wiper unit 70 in the lateral direction Y.

[0034] Drive Assembly The drive assembly 30 is shown in detail in Figure 5. The drive assembly 30 comprises a first drive wheel 26 in the form of a gear coupled to a guide roller 28. The guide roller 28 has a smooth outer surface, and the first drive wheel 26 is a gear or cog with teeth. The first drive wheel 26 and the guide roller 28 are mounted on a support shaft 27. The support shaft 27 is rotatably mounted on a support structure 25. The support structure 25 in Figure 5 is formed as a plate. The wetter 22 is mounted on the support structure 25. The wetter 22 is rigidly connected to the support structure 25 by screws.

[0035] The first drive wheel 26 engages with a gear rack 31. The gear rack 31 is rigidly connected to a printer frame 39. The printer frame 31 is stationary during operation. By rotating the first drive wheel 26, the wetter 22 and wiper unit 70 can be moved in the lateral direction Y. The gear rack 31 has multiple sections, and a raised rack section 32 is provided at the end closest to the rest position P. The raised rack section 32 is located above a run-out rack section 36. The run-out rack section 36 is parallel to the lateral direction Y and extends above the print medium support surface of the belt 6. The raised rack section 32 is formed by a first gear rack section separate from the second gear rack section, which includes the run-out rack section 36. The second gear rack segment is preferably a linear or straight gear rack. The first gear rack segment further comprises a lower rack section 35, which is parallel to and at the level of the run-out rack section 36. Between the raised rack section 32 and the lower rack section 35, there is an inclined rack section 33 to partially overcome the height difference between these two sections 32, 35. Between the inclined rack section 33 and the lower rack section 35, there is an inclined missing-tooth section 34. The missing-tooth section 35 extends downward in the lateral direction Y to the level of the lower rack section 35. The missing-tooth section 35 is substantially free of teeth that can engage with the teeth of the first drive wheel 26. The missing-tooth section 35 allows the first drive wheel 26 to transition smoothly from the raised rack section 32 to the lower rack section 35, while enabling a space-efficient construction. When the first drive wheel 26 moves in the lateral direction Y, it descends the inclined rack section 33, passes through the missing tooth section 35, and engages with the lower rack section 35.

[0036] The movement of the first drive wheel 26 is defined by a gear rack 31. This movement is guided by a guide roller 28. The guide roller 26 is mounted adjacent to the first drive wheel 26 on the same support shaft 26 as the first drive wheel 26 in the conveying direction X. The path of the guide roller 26 is limited by guides formed by limiters 38, 40-42 mounted on or within a printer frame 39. The printer frame 39 surrounds the guide roller 28 in the conveying direction X. This prevents the first drive wheel 26 from moving out of the gear rack 31 in the conveying direction X. Furthermore, the upward movement of the guide roller 28 is limited by upward movement limiters 40-42. The upward movement limiters 40-42 extend above the path of the guide roller 28 and ensure that the first drive wheel 26 cannot move upward out of engagement with the gear rack 31. With respect to the horizontal rack sections 32, 36, the upward movement limiters 40, 42 extend parallel to the lateral direction Y. Above the tilted rack section 33, a separate upward movement limiter 41 is also tilted. The tilted upward movement limiter 41 is positioned so that the first drive wheel 26 remains engaged with the gear rack 31 when the tilted rack section 33 is lowered or raised. In Figure 5, the upward movement limiters 40-42 are formed as bent portions of a plate that forms the printer frame 39.

[0037] FIG. 6 shows the maintenance unit 20 in a loading position in which the wiper unit 70 can be removed and / or inserted into the maintenance unit 20. In the loading position, the first drive wheel 26 is positioned on the raised rack section 32. As a result of this raised position, the support structure 25 is also pivoted to the raised position. Furthermore, the wetter 22 connected to the support structure 25 is also moved to the raised position. This positions the wetter 22 and its wetting device 24 away from the wiper unit 70. This allows the wiper unit 70 to slide out of the maintenance unit 70 by moving it in the opposite direction to the lateral direction Y. A rod mechanism 55 is provided to support the wetter 22. The rod mechanism 55 is configured to maintain the wetter 22 substantially horizontal to prevent leakage of the wetting fluid from the wetting fluid channel. The rod mechanism 55 moves downward together with the wetter 22 between FIGS. 6 and 7.

[0038] The wiper unit 70 is loaded by inserting it into the wiper unit holder 60. A wiper unit holder 60 is provided for each individual printhead unit. The wiper unit holder 60 includes a wiper unit support 29, and the wiper unit 70 is supported by the maintenance unit 20. The wiper unit holder 60 includes a wiper unit support frame that moves with the wetter 22. As shown in FIG. 12 , the wiper unit support frame may include rollers that allow the wiper unit 70 to be quickly and easily inserted into and retracted from the wiper holder 60.

[0039] A cam mechanism 51 is provided for moving the wetting device 24 into contact with the wetting medium 72 as it moves in the lateral direction Y. A driven wheel 52 is mounted on a cam arm, which is pivotable about a cam shaft 53. The driven wheel 52, cam arm, and cam shaft 53 move with the first drive roller 26 as it moves in the lateral direction Y. A cam surface 50 is provided stationary relative to the gear rack 31. The cam surface 50 has a first surface section with a protrusion 52 and a second surface section 46 that is inclined relative to the vertical direction Z. The cam mechanism 51 is described in detail below with reference to Figures 7 to 10.

[0040] FIG. 7 shows the maintenance unit 20 with the first drive wheel 26 in its first lower position. Compared to FIG. 6, the first drive wheel 26 is driven to move in the lateral direction Y, thereby descending the inclined rack section 33. Initially, the first drive wheel 26 moves over the raised rack section 32, where it is limited by the upward movement limiter 40. The upward movement limiter 40 prevents the guide roller 28 from moving upward, preventing the first drive wheel 26 from losing contact with the gear rack 31. The first drive wheel 26 then reaches the inclined rack section 33, where it begins to descend the gear rack 31. To allow the first drive wheel 26 to pass through the lower transition section, a missing tooth section 34 is provided at the transition section, as shown in FIG. 8. The missing tooth section 34 is sufficiently small so that the first drive wheel 26 can simultaneously maintain contact with the teeth of the inclined rack section 33 and the lower rack section 35. During this downward movement, the tilt limiter 41 prevents the first drive wheel 26 from disengaging from the gear rack 31. FIG. 7 shows a gap G in the upward movement limiter 40 facing the missing tooth section 34. The gap G is between the tilt limiter 41 and the run-out limiter 42, which extends above the missing tooth section 36. The gap G provides sufficient freedom so that the first drive wheel 26 can pass through the missing tooth section 34. If a limiter were provided at the position of the gap G, the first drive wheel 26 would get caught between the teeth of the gear rack 31 and the upward movement limiter 40 and become stuck there.

[0041] As the first drive wheel 26 descends, the support shaft 27 moves downward, pivoting the support structure 25 downward. This forces the wetter 22 downward so that the wetter 22 is at its operating level and remains there during the wiping operation. In response, the rod mechanism 55 moves to carry the wetter 22 downward while maintaining it substantially horizontal to prevent spillage of wetting fluid.

[0042] During this movement, the driven wheel 52 of the cam mechanism 51 follows the substantially horizontal surface section 45 of the cam surface 50, thereby preventing the cam mechanism 51 from operating, as shown in FIG. 9 . The substantially horizontal surface section 45 is flat or level except for a single protrusion 44. The driven wheel 52 runs up to the protrusion 44 included in this section 45, which prevents the first drive wheel 26 from disengaging from the gear rack 31 when the first drive wheel 26 is in gap G in the upward travel limiter 40. At gap G, the first drive wheel 26 is not prevented by the upward travel limiter 40 from disengaging from the gear rack 31. Instead, the cam mechanism 51 prevents the first drive wheel 26 from disengaging from the gear rack 31. When in the protrusion 44, the cam mechanism 51 applies a reaction force F to the first drive wheel 26. w , which urges the first drive wheel 26 towards the missing tooth section 34. The protrusion 44 is in the form of a slight bump. The bump is large enough to allow the cam mechanism 51 to act as a brake to prevent uncontrolled rotation of the first drive wheel 26. When the first drive wheel 26 rotates upward relative to the lateral direction Y in the inclined gear section 33, it exerts an upward force F up Through interaction with the gear rack 31, the first drive wheel 26 is further driven by a reactive outward force F out , which may drive the first drive wheel 26 out of contact with the teeth of the gear rack 31 when in gap G. The protrusion 44 is subjected to a normal force F n F n is the normal force required to overcome the protrusion 44. The shape of the protrusion 44 creates an accompanying reaction force Fw It also provides the reaction force F w is the outward force F out Conversely, the protrusion 44 generates a reaction force F w is the outward force F out The driven wheel 52 cannot pass the projection 44 without additional driving force from the motor. out is the reaction force F w , the first drive wheel 26 is thereby prevented from losing contact with the gear rack 31 at gap G because the first drive wheel 26 is connected to driven wheel 52. It will be appreciated that the above mechanism also prevents the first drive wheel 26 from losing contact with the gear rack 31 when the first drive wheel 26 is driven to descend on an individual section. When descending, the weight of the structure provides an additional force that urges the first drive wheel 26 against the gear rack 26.

[0043] FIG. 10 shows the first drive wheel 26 transitioning from the first gear rack segment to the horizontal second gear rack segment formed by the run-out rack section 36. The first drive wheel 26 is at the level shown in FIG. 7, and therefore the wetter 22 is at the same level as in FIG. 7. The driven wheel 52 of the cam mechanism 51 has passed the protrusion 44 but still remains on the horizontal surface section 45. Movement is controlled by driving the first drive wheel 26. It will be understood that in all of FIGS. 4-10, the maintenance unit 20 may still be considered to be in its rest position. The maintenance unit 20 in these figures is still in a non-wiping mode.

[0044] FIG. 11 shows the first drive wheel 26 advancing further into the run-out rack section 36. In FIG. 11, the maintenance unit 20 enters its wiping mode. The wetter 22 is then moved relative to the wiper unit 70 so that the wetting device 24 contacts the wetting medium 72. The wetting medium 72 is thereby actively wetted by wetting fluid supplied through the wetting fluid channel within the wetter 22. The relative movement between the wetter 22 and the wiper unit 70 is controlled by a cam mechanism 51. In FIG. 11, the driven wheel 52 engages the inclined cam surface 46, thereby actuating the cam arm. The movement of the cam arm urges the wetter 22 and the corresponding wetting section (WE in FIG. 14) of the wiping medium 72 together. The movement is defined by a rod mechanism 55 configured to maintain the wetter 22 substantially horizontal during movement. As shown in FIG. 10, the wiper unit 70 defines a wetting portion 73 to which the wetting medium 72 is exposed. In the wetting section 73 , the wetter 22 engages the wetting medium 72 and transfers wetting fluid to the wetting medium 72 .

[0045] In FIG. 11 , the maintenance unit 20 is in its wiping mode and moves through its operating range W. The wetter 22 actively wets the wiper medium 72, which is wiped along the nozzle plate of the printhead assembly 5 with its wiping section (WI in FIG. 14 ). The wiper medium 72 unspools during lateral movement, so that each section of the nozzle plate is wiped with a clean portion of the wiper medium 72. The ink-laden wiper medium 72 spools away from the printhead. It will be appreciated that, in the contact area, the speed of the wiper medium 22 relative to the printer frame 39 is preferably equal to or (slightly) greater than the speed of the first drive wheel, wiper unit 70, and / or wetter 22.

[0046] FIG. 12 shows the drive wheels of the drive assembly 30. Note that all of the movements in FIGS. 4-11 are controlled in this example by a single motor driving a motor wheel 60. The motor wheel 60 drives a first drive wheel through multiple transmission wheels 58, 59. In FIG. 12, all of the wheels 26, 58-60 are interconnected gears, specifically double gears, where the number of teeth on the receiving wheel is different from the number of teeth on the connected wheel. This allows for the appropriate speeds to be achieved.

[0047] wiper unit A single wiper unit 70 is shown in FIG. 13. The wiper unit 70 is formed as a removable cassette capable of holding a roll of wiping medium 72. The wiper unit 70 allows the wiper medium 72 to be spooled so that it wipes across the nozzle plate. The wiper medium 72 is rewound onto a second roll 82. The roll 82 is disposed inside a housing 90 that forms the outer body of the wiper unit 70. The housing 90 is provided with a grip 92 that allows the wiper unit 70 to be easily manually removed from its individual holding location by pulling the grip 92 in the direction opposite to the lateral direction Y when the maintenance unit 20 is in the (un)loaded position of FIG. 6.

[0048] The path of the wiping medium 72 through the wiper unit 70 is shown in Figures 14 and 15. Figure 14 shows the wiper unit 70 without one of the side panels forming the housing 90. The wiping medium 72 is provided as a first roll 73 on a first roller 74. A limiter 83 may be provided to maintain the shape and position of the first roll 73. From the first roll 73, the wiping medium 72 extends over multiple convex rollers 75-78, resulting in a portion of the wiping medium 72 extending outside the housing 92. The diameter of the convex rollers 75-78 is larger in the middle of each roller 75-78 in the conveying direction than at its ends. The diameter gradually decreases toward each end. This convex shape, combined with the bend in the path of the wiping medium 72 provided by the convex rollers 75-78, continuously guides the wiping medium 72 between these rollers 75-78. Thus, the position of the wiper medium 72 is limited without the need for an active or automated control mechanism.

[0049] The convex rollers 75-78 further define a wetting section WE, where the wetter 22 can apply wetting fluid to the wiper medium 72. In the wetting section WE, the wiper medium 72 extends outside the housing 90. A curved recess 95 is provided in the side plate of the housing 90 to allow the wetter 22 to engage with the wiper medium 72 in the wetting section WE. The convex rollers 75-78 define a negative turn section in the path of the wiper medium 72. Inside this negative turn section, a portion of the wiper medium 72 is exposed and therefore accessible to the wetter 22. Thus, when the printhead maintenance unit 20 is in its wetting position of FIG. 11 , the wiper medium 72 is wetted in the negative turn section. The wiper medium 72 is wetted between the central convex rollers 76 and 77. Downstream of the first central convex roller 76, the wiper medium 72 is provided with wetting fluid during the wetting operation.

[0050] The downstream convex rollers 77-78 interact with a forcing pinch mechanism 100 via the wiper medium 72. The forcing pinch mechanism 100 provides a substantially constant tension to the wiper medium 72 during operation. The forcing pinch mechanism 100 is shown in detail in FIG. 16. The forcing pinch mechanism 100 comprises a frame 102 pivotally or rotatably mounted to the housing 90. The frame 102 is pivotable about an axis extending in the conveying direction X and passing through an axis opening 106. The axis opening 106 defines a pivot arm 105 that defines the movement of the frame 102. The pivot arm 105 is rigidly fixed to the frame 102 by a fixing means 111. The frame 102 is further connected to the housing 90 by spring elements 108, 109. The spring elements 108, 109 are pretensioned in both directions of movement of the frame 102 about the axis within the axis opening 106. In FIG. 16 , more spring elements 108 are provided on one side compared to a single spring element 109 on the opposite side. During operation, the wiper medium 72 is generally under tension, which acts against the spring elements 108. An opposing spring element 109 is provided when the tension is temporarily reduced. Effectively, the combined spring elements bias the force pinch mechanism 100 toward the printhead array 5. Furthermore, the movement of the frame 102 may be limited to a predetermined range by, for example, a limiting opening 104 that engages a stop rigidly attached to the housing 90 to define an end position for the movement of the frame 102. Such a stop may be formed, for example, by a particular convex roller 77.

[0051] In FIG. 16 , the forcing pinch mechanism 100 further includes a toothed roller 79 that defines a wiping section WI. In the wiping section WI, the wiper medium 72 wipes across the printhead array during a cleaning operation. The toothed roller 79 includes teeth that extend in the transport direction X during use, resembling tiny toothed gears. The toothed roller 79 is the first roller to contact the wiper medium 72 that has wiped ink or contaminants from the nozzle plate. By only locally pressing on the wiper medium 72, the toothed roller 79 prevents or reduces the likelihood of fluid being squeezed out of the wiper medium 72. The toothed roller 79 is rigidly connected to the frame 102 by a panel 110.

[0052] As shown in FIG. 17, the wiper medium 72 extends from a toothed roller 79 onto a lamella roller 80. The lamella roller 80 is shown in FIG. 18. The lamella roller 80 has a shaft 85 that extends in the conveying direction X during use. The shaft 85 is provided with a number of lamellas 86. Each of the lamellas is shaped as a circular disk. The disks are spaced apart along the conveying direction X. The (outer) lamellas may have a reduced diameter towards the ends. The lamellas 86 prevent fluid from being forced out of the wiper medium 72. Pressure on the wiper medium 72 is applied only locally at the lamellas 86, not in the areas between them. This prevents contaminated wiper fluid from being forced out of the wiper medium 72.

[0053] FIG. 17 shows the mounting of the take-up roller 81 for the second roll 82. The take-up roller 81 extends through the second roll 82. On the right side, the take-up roller 81 is provided with a gear 109 for rotating the roll 82. The gear 109 is driven by a motor wheel 108. On the left side in the conveying direction X, the second roll 82 is confined by a flange 107. It will be understood that a similar flange may be provided between the second roll 82 and the gear 109. The flange 107 is fixed to the take-up roller 81 by a locking mechanism 110. The locking mechanism 110 is arranged to interact with a release mechanism 120 provided on the housing part 93. The housing parts 92, 93 form a housing 90 that encloses the rolls 73, 82.

[0054] The locking mechanism 110 is shown in FIGS. 19-21. The locking mechanism 110 includes a cylindrical body 111. The body 111 is provided with a flange member 114 near one of its ends. The flange member 114 extends perpendicular to the main axis of the body 111. The locking mechanism 110 includes a click mechanism formed by a locking protrusion 118 attached to a hinge plate 113. The hinge plate 113 allows the locking protrusion 118 to move toward and away from the main axis of the body 111. The hinge plate 113 is formed in the wall of the body 111 by an internal recess. In the neutral position of the hinge plate 113, the locking protrusion 118 extends radially beyond the body 111. A similar locking protrusion 118 with the hinge plate 113 is provided on the opposite side of the body 111. Between the flange members 114, recesses 117 are provided, through which the free ends of the hinge plates 113 extend beyond the flange members 114 opposite the conveying direction X. A ring-shaped opening 115 is provided between these free ends to receive the end of the take-up roller 81. A rotation handle 116 is provided on the flange members 114 at the level of this ring. The rotation handle 116 is shaped so that it can be easily engaged to rotate the locking mechanism 110. As shown in FIG. 21 , the flange 107 has a central opening into which the cylindrical body 111 fits. The flange members 114 are wider and cannot pass through the central opening. On the opposite side of the flange 107, a fixing protrusion 119 extends beyond the radius of the body 111, so that the flange 107 is fixed between the fixing protrusion 119 and the flange members 114. The fixing protrusion 119 is provided on each of these hinge plates 112, which is configured to pivot inward when the cylindrical body 111 moves through the central opening of the flange 107. The fixing projections 119 and the locking projections 118 are provided with angled portions to help press the hinge plates 112, 113 inward. On the side facing the flange member 114, the fixing projections 119 and the locking projections 118 are provided with flat abutment surfaces that act as stops.

[0055] 22 shows the locking mechanism 110 engaged with the take-up roller 81. The take-up roller 81 has a hollow cylindrical roller body 98, with an opening 99 formed in a position corresponding to the locking projection 118 of the locking mechanism 110. The cylindrical body 111 of the locking mechanism 110 is inserted into the roller body 98 through the flange 107. The cylindrical body 111 rotates so that the locking projection 118 is positioned in the opening 99. The hinge plate 113 then resumes its rest position, driving the locking projection 119 through the opening 99, thereby securing the locking mechanism to the take-up roller 81.

[0056] The locking mechanism 110 can be released from the take-up roller 81 by a release mechanism 120. The release mechanism 120 is secured to the housing part 93 by a clamp 112. The release mechanism 120 includes an elastically deformable ring 121 having opposing pressure members 123. Each pressure member 123 is provided with a finger grip 124 for easy engagement by an operator. In their rest positions, the pressure members 123, as well as the free ends of the hinge plates 113, face each other. A rotation handle 116 can be used to rotate the locking mechanism 110 in the correct orientation relative to the release mechanism 120. When the pressure members are moved toward each other, the hinge plates 113 are forced inward, which moves the locking projections 118 out of the openings 99 in the take-up roller 81, allowing the locking mechanism 110 to slide off the take-up roller 81. This allows the second roll 82 on the take-up roller 81 to be removed and an unused roll to be loaded.

[0057] While specific embodiments of the present invention have been illustrated and described herein, those skilled in the art will recognize that various alternative and / or equivalent implementations exist. It should be understood that the exemplary embodiment or exemplary embodiments are examples only and are not intended to be limiting in any way in scope, applicability, or configuration. 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, and it should be understood that various changes can be made in the function and arrangement of elements described in the exemplary embodiments without departing from the scope as set forth in the appended claims and their legal equivalents. In general, this application is intended to cover any adaptations or variations of the specific embodiments discussed herein.

[0058] In this document, the terms "comprises," "comprising," "includes," "including," "including," "containing," "having," and any variations thereof are intended to be understood in an inclusive (i.e., non-exclusive) sense, and it is understood that the processes, methods, devices, apparatuses, or systems described herein are not limited to those features or portions or elements or steps that are enumerated, but may include other elements, features, portions, or steps that are not expressly enumerated or that are inherent to such processes, methods, articles, or apparatuses. Furthermore, as used herein, the terms "a" and "an" are understood to mean one or more, unless expressly stated otherwise. Furthermore, the terms "first," "second," "third," etc. are used merely as labels, and are not intended to impose or establish numerical requirements on a particular ranking of the importance of those objects.

[0059] The 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 invention, and all such modifications which would be obvious to those skilled in the art are intended to be included within the scope of the following claims.

Claims

1. A wiper unit (70) for a maintenance unit (20) of a printer (1), the wiper unit (70) comprising: a housing (90), a plurality of rollers (74-81), two of which rollers (74, 81) are configured to hold a roll (73, 82) of wound up wiping medium (72), and the remaining rollers (75-80) define a path for transporting said wiping medium (72) between said two rollers (74, 81); A wiper unit (70) characterized in that the path defined by the rollers (74-81) comprises a negative curvature (B), the negative curvature extending at least partially outside the housing (90).

2. 2. The wiper unit (70) of claim 1, wherein the negative curvature (B) is defined by three rollers (75-77), the three rollers (75-77) being arranged such that the path of the wiper medium (72) extends towards a wiping section of the path between a first pair (75, 76) of the three rollers (75-77) and away from the wiping section between a second pair (76, 77) of the three rollers (75-77).

3. 3. A wiper unit (70) as described in claim 1 or 2, wherein the housing (90) has a curved portion that curves away from the portion of the negative bend (B) in the path of the wiper medium (72) outside the housing (90).

4. 4. The wiper unit (70) according to claim 1, further comprising a force pinch mechanism (100), the force pinch mechanism (100) comprising: - at least one roller (79) of said rollers (75-77), - pivotable relative to said housing (90), - a wiper unit (70) that is pre-tensioned so as to provide a substantially constant tension to said wiping medium (72) during use.

5. 5. The wiper unit (70) of claim 4, wherein the at least one roller (79) is a toothed roller, and the teeth of the toothed roller are configured to directly contact the wiper medium (72).

6. 6. The wiper unit (70) of claim 1, wherein the plurality of rollers (74-81) comprise convex rollers (75-78), the convex rollers (75-78) defining a substantially Z-shaped curve in the path and configured to drive the wiping medium (72) to a centerline of the path.

7. 7. The wiper unit (70) of any one of claims 1 to 6, further comprising a lamella roller (80) comprising a plurality of spaced apart lamellae (86).

8. 8. The wiper unit (70) according to claim 1, further comprising a locking mechanism (110) fixable on a take-up roller (81) of the plurality of rollers (74-81), the locking mechanism (110) comprising a cylindrical body (111) insertable into the take-up roller (81) and locking projections (118) respectively provided on hinge plates (113), the hinge plates (113) configured to drive the respective locking projections (118) into locking openings (99) of the take-up roller (81) to fix the locking mechanism (110) to the take-up roller (81).

9. 9. The wiper unit (70) of claim 8, wherein the locking mechanism (110) further comprises a flange member (114), the flange member (114) extending beyond the main body (111) and the fixing projection (119) such that the flange (107) is fixable between the fixing projection (119) and the flange member (114).

10. 10. The wiper unit (70) of claim 9, wherein the hinge plate (113) extends past the flange member (114) in an axial direction defined by the cylindrical body (111).

11. 10. The wiper unit (70) according to claim 8 or 9, wherein the locking mechanism (110) further comprises a rotation handle (116) on the flange member (114) for rotating the locking mechanism (110).

12. 12. The wiper unit (70) according to any one of claims 9 to 11, wherein a release mechanism (120) is provided on the housing (90), the release mechanism (120) comprising opposing pressing members (123) arranged to bring free ends of the hinge plates (113) together to release the locking mechanism from the take-up roller (81).

13. 13. The wiper unit (70) according to claim 12, wherein the release mechanism (120) comprises an elastically deformable ring (121).

14. 14. The wiper unit (70) according to any one of claims 1 to 13, wherein the wiper unit (70) is formed as a cassette that is removably attachable to a holding portion of a print head maintenance unit (20).

15. A printhead maintenance unit (20) comprising at least one holding site for a wiper unit (70) according to any one of claims 1 to 14.

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