Inkjet printing device having spacer means for at least one print head
Patent Information
- Application Number
- PCT/EP2026/050868
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-02-18
- Filing Date
- 2026-01-15
- Publication Date
- 2026-08-27
Smart Images
Figure EP2026050868_27082026_PF_FP_ABST
Abstract
Description
[0001] Inkjet printing device with spacer for at least one printhead
[0002] The present invention relates to an inkjet printing device for continuously printing on a web-shaped medium according to the preamble of claim 1.
[0003] Single-pass inkjet printing devices for printing on a web-shaped medium are known from the prior art, comprising a printing table with an upwardly curved, interrupted support surface for the medium, wherein a printing unit with several printheads spaced apart opposite the support surface is assigned to the support surface, wherein the inkjet printing device comprises a feed device for feeding the medium along the support surface in a feed direction.
[0004] During printing, nozzle failures in printheads occur sooner or later for various reasons. Individual nozzle failures can be compensated for using known software solutions. In this process, the faulty, non-functioning, or malfunctioning nozzles are deactivated, and the image data that was originally to be printed by these nozzles is redistributed to neighboring nozzles by ejecting droplets with a correspondingly larger volume.
[0005] There are web-like media to be printed whose width is less than the maximum print width of an array of printheads. Particularly when printing on such media, certain machine configurations and / or printing conditions lead to an increased failure rate of the printhead nozzles, which cannot be adequately compensated for by software-based methods.
[0006] In inkjet printing devices for the continuous printing of a web-like medium, it has been observed that the nozzle plates of certain printheads exhibit scratch marks that run essentially parallel to the feed direction of the web-like medium. The increased occurrence of defective nozzles is attributed to web-like media moving in the feed direction, whose side edges lie within the nozzle's operating area and are aligned parallel to the feed direction. This is particularly true because these edges sometimes protrude upwards from the contact surface in a cupped or U-shaped manner towards the nozzle plate, causing their typically sharp side edges to rub against the nozzle plate.
[0007] One explanation for the occasional lifting of the side edges of a material web when it is pulled over a support surface is the creation of compressive stresses and / or tensile stresses acting transversely to the direction of travel of the material web within the material web, which lead to an inhomogeneous transverse contraction of the material web.
[0008] This is particularly relevant when printheads with nozzle plates that are sensitive to abrasion have to be used for a specific purpose.
[0009] In this application, the term "material web" is to be understood as a synonym for the term "web-shaped medium".
[0010] When printing on laminated web media whose layers are held together by an adhesive, such as label roll stock, it has been observed that adhesive can ooze out from the edges of some media. If adhesive-coated edges rub against the nozzles of a nozzle plate, the nozzles are usually irreparably clogged and damaged. The adhesive oozing out can be attributed to various, though not always easily identifiable, causes. Typically, media rolls are cut from a wider roll, and the adhesive, which is not hard and rigid, can ooze out at these cut surfaces. It is assumed that improper storage, especially at higher temperatures, promotes this adhesive oozing out.Furthermore, it is suspected that mechanical stresses on media rolls and / or tensions that occur during the winding process of the medium also promote the oozing of the adhesive at the side edges of the media.
[0011] The problem of faulty nozzles is further exacerbated by improper handling of media rolls. Media rolls are sometimes stored on support surfaces in such a way that their winding axis is aligned parallel to the direction of gravity. If the support surface, especially the base, is not clean, dirt particles adhere to the bottom of the media roll and thus to the side edge of the media. When the side edge of the web-like media comes into contact with a printhead nozzle plate, these particles can clog the nozzles and increase the abrasion, particularly on a sensitive nozzle plate. Furthermore, improper handling of a media roll can cause small dents on its outer edge, which can also scratch the nozzle plates.Paper dust present on the side edges of a medium consisting of or comprising paper can also contribute to the problem of nozzle clogging and nozzle plate abrasion. When this application refers to a nozzle plate, it means the surface of the nozzle plate facing the medium or the medium's contact surface.
[0012] There is a need for an inkjet printing device that, in feed operation, provides protection for nozzle plates to be protected against abrasion by at least one side edge of the medium, aligned in the feed direction of the medium and especially occasionally protruding, against the nozzle plates in the area of the nozzle openings.
[0013] The object of the invention is therefore to provide an inkjet printing device which, in feed operation, enables protection of nozzle plates to be protected from being rubbed along by at least one side edge of the medium, which is aligned in the feed direction of the medium and in particular occasionally protrudes, against the nozzle plates in the area of the nozzle openings.
[0014] According to the invention, the problem is solved with an inkjet printing device comprising the features of claim 1. The respective dependent claims relate to further advantageous and, where applicable, additionally inventive embodiments.
[0015] The invention is based on the idea that an inkjet printing device comprises at least one spacer means for maintaining a distance of greater than zero between a side edge of the medium, which is aligned in the feed direction (V) and lies in the effective area of the nozzles of a nozzle plate of a printhead of the printing unit, and the nozzle plate, wherein the spacer means is arranged at least during the feed of the medium in the feed direction (V) at least in the effective area of the nozzles of the nozzle plate and thus between the nozzle plate and the side edge in a separating manner, so that even during printing the medium the medium is movable in the feed direction (V) relative to the spacer means.
[0016] The inkjet printing device according to the invention is an inkjet printing device for continuously printing a web-shaped medium with a printing table forming an interrupted support surface for the medium, wherein a printing unit is assigned to the interrupted support surface, which is spaced apart from the interrupted support surface, and with a feed device for feeding the medium along the support surface in a feed direction (V).
[0017] Accordingly, the inkjet printing device according to the invention is an inkjet printing device for continuously printing a web-shaped medium with a printing table forming an interrupted support surface for the medium, wherein a printing unit is assigned to the interrupted support surface, which is spaced apart from the interrupted support surface, and with a feed device for feeding the medium along the support surface in a feed direction (V).
[0018] According to the invention, the inkjet printing device comprises at least one spacer means for maintaining a distance of greater than zero between a side edge of the medium, which is aligned in the feed direction (V) and lies in the effective area of the nozzles of a nozzle plate of a printhead of the printing unit, and the nozzle plate, wherein the spacer means is arranged at least during the feed of the medium in the feed direction (V) at least in the effective area of the nozzles of the nozzle plate and thus between the nozzle plate and the side edge in a separating manner, so that even when printing the medium the medium is movable in the feed direction (V) relative to the spacer means.
[0019] This means that the spacer is designed and arranged in such a way that the side edge, even if it is bent upwards in the direction of the nozzles of the printhead in the corresponding effective area of the nozzles of the nozzle plate, is movable below the spacer relative to it.
[0020] Typically, the printing device comprises a web-shaped medium whose width is less than a maximum printing width.
[0021] In a preferred embodiment, the spacer is positioned at a distance from the nozzle plate. This improved design offers the advantage that the nozzle plate is not damaged by the spacer, and that unintentional adjustment of a printhead optimally configured in its degrees of freedom by the spacer is avoided. Furthermore, this allows the position of the spacer relative to the nozzle plate to be corrected during printing.
[0022] According to a preferred embodiment, the spacer is formed by a flat profile with flat sides and side edges extending between them, wherein the flat side facing the nozzle plate is aligned parallel to the nozzle plate, and wherein the flat profile is preferably a spring sheet.
[0023] The spacer can be designed to be adjustable relative to the printing unit in a direction perpendicular to the side edge and parallel to the interrupted contact surface. This design offers the advantage that the spacer can be adjusted and thus adapted to the width of the medium being printed, perpendicular to the feed direction.
[0024] Furthermore, it is possible that the spacer is designed to be height-adjustable relative to the nozzle plate.
[0025] In a preferred embodiment, the spacer is positioned at its end, which is parallel to the interrupted support surface and perpendicular to the side edge of the medium, via a bracket on a frame part of the printing table located below the interrupted support surface. This further development offers the advantage that a particularly simple and cost-effective construction can be achieved with this design of the spacer and its bracket.
[0026] The bracket can be supported on the frame part of the printing table by means of an adjustment device for adjusting the height of the bracket relative to the frame part.
[0027] Furthermore, it is possible that the adjustment device for adjusting the height of the bracket relative to the frame part includes at least one pressure element, preferably a compression spring guided on a guide element, which is clamped between the bracket and the frame part, such that it enables the corresponding height adjustability of the bracket.
[0028] Furthermore, it is possible that the spacer is attached to the holder at its ends, which are spaced apart from each other in the feed direction (V).
[0029] The spacer is preferably designed such that its ends, which are spaced apart from each other in the feed direction (V), do not protrude significantly beyond the underside of the print head facing the medium in the feed direction.
[0030] According to a preferred embodiment, the printing table comprises a web with several support elements oriented transversely to the feed direction (V) and spaced apart from one another, wherein the interrupted contact surface is formed by the support elements, and wherein preferably the web is a roller web and the support elements are cylindrical rollers. These further developments offer the advantage that the medium is less statically charged due to reduced friction than with a continuous contact surface, and that better printing quality can be achieved.
[0031] The interrupted support surface can have an arc-shaped cross-section along the transport direction, particularly in the form of a circular segment. This reduces the tendency of the side edges to lift compared to a flat support surface.
[0032] In a preferred embodiment, the feed device is designed such that it continuously moves the medium along the support surface in the feed direction (V) during the printing of the medium.
[0033] According to a preferred embodiment, the printing unit is designed to be height-adjustable relative to the printing table and thus also to the interrupted support surface, wherein the spacer is designed such that it can be positioned in a variably adjustable working position against one or more stationary support elements of the printing unit located upstream and downstream of the print head in the feed direction (V). This allows for a simple method or device for adjusting the height of the spacer.
[0034] In a preferred embodiment, the spacer is associated with an adjustment device for its adjustment in a direction perpendicular to the side edge and in a direction parallel to the interrupted support surface, wherein the frame part is part of the adjustment device.
[0035] In a particularly preferred embodiment, a support element of the support elements is associated with the print head, wherein the holder includes a recess which is designed to be able to enclose the support element without contact.
[0036] Furthermore, it is possible that the roller conveyor includes cover plates which are arranged in the spaces between the cylindrical rollers and below the interrupted support surface, partially covering the spaces upwards.
[0037] In a particularly preferred embodiment, the inkjet printing device comprises at least one sensor, preferably at least two sensors spaced apart from each other in the feed direction, which are designed to detect the movement of the side edge in a direction (Q) perpendicular to the side edge and parallel to the interrupted support surface, wherein the inkjet printing device is designed to compensate for the movement of the side edge by a corresponding movement of the spacer means.
[0038] These training courses offer the advantage that collisions between the holder and the medium can be prevented automatically.
[0039] According to a further preferred embodiment, the inkjet printing device comprises at least a second spacer means for maintaining at least a minimum distance between the second side edge of the medium, which is aligned in the feed direction (V) and lies in the effective area of the nozzles of a second printhead of the printing unit, and the second nozzle plate of the second printhead, wherein the second spacer means is arranged separating the second side edge, at least during the feed direction (V) of the medium, at least in the effective area of the nozzles of the second nozzle plate, and thus between the second nozzle plate and the second side edge, so that the medium is movable relative to the second spacer means in the feed direction (V) even during printing.
[0040] The invention will now be explained below using examples and figures.
[0041] Fig. 1 shows a schematic side view of a particularly preferred embodiment of the inkjet printing device according to the invention.
[0042] Fig. 2 shows a schematic side view of the printing table of the inkjet printing device according to Fig. 1.
[0043] Fig. 3 shows a schematic top view of the inkjet printing device according to Fig. 1. Fig. 4 shows a schematic front view in cross-section of the inkjet printing device according to Fig. 1.
[0044] Figure 1 shows a particularly preferred embodiment of the inkjet printing device according to the invention.
[0045] The first section (not shown) of the inkjet printing device comprises a device for unwinding a web-shaped medium 101 with a first winding core, a dancer roller, and several deflection rollers over which the medium 101 can be guided to a printing table 103. The unwinding device is part of a feed unit for advancing the medium 101 along a discontinuous support surface of the printing table 103 (see Fig. 2) in a feed direction (V) (see Fig. 1). The second section of the inkjet printing device comprises the printing table 103, which forms the discontinuous support surface for the medium 101. A printing unit 105, located at a distance opposite the discontinuous support surface, is associated with the discontinuous support surface. The printing unit comprises five printheads 109, 109', 109", 109'", 109"", and 109", as shown in Figures 3 and 4.
[0046] The printing table 103 comprises a roller conveyor with several support elements in the form of cylindrical rollers 119, 119', 119“, 119'“, 119““, 119““’, 119“““, 123, 125, oriented transversely to the feed direction (V) and spaced apart from each other, wherein the interrupted support surface is formed by the cylindrical rollers 119, 119', 119“, 119'“, 119““’, 119“““, 123, 125.
[0047] As can be seen from Figure 1, the interrupted support surface has a circular segment shape in its cross-section along the transport direction (V).
[0048] Figure 2 shows the printing table 103 from Figure 1, in which the interrupted support surface formed by the cylindrical rollers 119, 119', 119“, 119'“, 119““’, 119“““, 123, 125 for receiving the web-shaped medium 101 to be printed is represented as a fictitious, dotted arc line, which also bridges the free areas between the cylindrical rollers 119, 119', 119“, 119'“, 119““’, 119“““, 123, 125.
[0049] As a third section (not shown), the inkjet printing device includes several deflection rollers over which the medium 101 can be conveyed to a device for winding the medium 101 onto a second winding core.
[0050] As shown in Figures 1 and 3, the inkjet printing device comprises a spacer 107 for maintaining a distance greater than zero between a side edge 111 of the medium 101, oriented in the feed direction (V) and located in the effective area of the nozzles of a nozzle plate 113 of a printhead 109 of the printing unit 105, and the nozzle plate 113. The spacer 107 is arranged, at least during the feed of the medium 101 in the feed direction (V), at the side edge 111 located in the effective area of the nozzles of the nozzle plate 113 and thus between the nozzle plate 113 and the side edge 111, separating them, so that even during printing the medium 101, the medium 101 is movable in the feed direction (V) relative to the spacer 107.
[0051] Typically, the distance between the spacer and the nozzle plate is less than 1 millimeter, and the distance between the spacer and the medium to be printed is less than 2 millimeters. In a highly preferred embodiment, the distance between the spacer and the nozzle plate is approximately 0.3 mm, and the distance between the spacer and the medium to be printed is 1.1 mm, with the thickness of the flat profile being approximately 0.3 mm.
[0052] The spacer 107 is formed by a flat profile as a spring steel sheet with flat sides and side edges extending between them, the flat side facing the nozzle plate 113 being aligned parallel to the nozzle plate 113. As shown in Figure 1, the spacer 107 is spaced apart from the nozzle plate 113. This is also illustrated in Figure 4.
[0053] As shown in Figures 1 and 4, the spacer medium 107 is spaced apart from the nozzle plate 113.
[0054] The spacer 107 is adjustable relative to the printing unit 105 in a direction perpendicular to the side edge 111 and parallel to the interrupted support surface. As shown in Figure 4, the spacer 107 is held at its end, which is spaced apart from the interrupted support surface and perpendicular to the side edge 111 of the medium 101, by means of a bracket 115 on a frame part 117 of the printing table 103, which is spaced apart from and located below the interrupted support surface.
[0055] The spacer 107 is associated with an adjustment device for its adjustment in a direction perpendicular to the side edge 111 and parallel to the interrupted support surface, the frame part 117 being part of the adjustment device. The perpendicular direction with respect to the side edge 111 is indicated in Figures 3 and 4 by the double arrow(s) labeled Q.
[0056] The printing unit 105 is designed to be height-adjustable relative to the printing table 103 and thus also to the interrupted support surface, as shown in Figures 1 and 2, wherein the spacer 107 is designed in such a way that it can be placed in a variably adjustable working position on one or more stationary support parts 121, 12T of the printing unit 105 which are located downstream and upstream of the print head 109 in the feed direction (V).
[0057] The spacer 107 is designed to be height-adjustable relative to the nozzle plate 113. The bracket 115 of the spacer 107 is supported on the frame part 117 of the printing table 103 via an adjustment device for adjusting the height of the bracket 115 relative to the frame part 117. The adjustment device for adjusting the height of the bracket 115 comprises at least two compression springs 131, 13T guided on guide elements 126, 126', which are clamped between the bracket 115 and the frame part 117, such that they enable the height adjustability of the bracket 115.
[0058] As shown in Figures 1 and 2, the printhead 109 is associated with the support element 119 of the support elements 119, 119', 119“, 119'“, 119““'; 119“““, 123, 125, wherein the holder 115 includes a recess which is designed to be able to enclose one of the support elements 119 without contact.
[0059] As shown in Figure 4, the inkjet printing device comprises a second spacer 107' for maintaining a distance greater than zero between the second side edge 11T of the medium 101, which is aligned in the feed direction (V) and lies within the effective area of the nozzles of the second nozzle plate 113' of a second printhead 109' of the printing unit 105, and the second spacer 107', wherein the second spacer 107' is arranged separating the second side edge 111' at least during the feed direction (V) of the medium 101, and thus between the second nozzle plate 113' and the second side edge 11T, so that even during printing the medium 101 the medium 101 is movable in the feed direction (V) relative to the second spacer 107'.
[0060] Accordingly, the inkjet printing device according to a preferred embodiment comprises at least one spacer 107, 107' for maintaining a distance greater than zero between the side edges 111, 11T of the medium 101, which are oriented in the feed direction (V) and lie within the effective area of the nozzles of the respective nozzle plates 113, 113' of each printhead 109, 109' of the printing unit 105, and the respective nozzle plate 113, 113', wherein the respective spacer 107, 107' is arranged separating the respective side edge 111, 111', which lies within the effective area of the nozzles of the respective nozzle plate 113, 113', at least during the feed of the medium 101 in the feed direction (V), and thus between the respective nozzle plate 113, 113' and the respective side edge 111, 11T, so that even during printing of the Medium 101 is movable in the feed direction (V) relative to the respective spacer 107, 107'.
[0061] Finally, it should be noted that, for a better understanding of the structure of the inkjet printing device, some of its components have been shown not to scale and / or enlarged and / or reduced in size.
Claims
Claims:
1. Inkjet printing device for continuously printing a web-shaped medium (101) with a printing table (103) forming an interrupted support surface for the medium (101), wherein a printing unit (105) is assigned to the interrupted support surface, which is spaced apart from the interrupted support surface, and with a feed device for feeding the medium (101) along the support surface in a feed direction (V), characterized in that the inkjet printing device comprises at least one spacer (107) for maintaining a distance of greater than zero between a side edge (111) of the medium (101) oriented in the feed direction (V) and lying in the effective area of the nozzles of a nozzle plate (113) of a printhead (109) of the printing unit (105) and the nozzle plate (113).wherein the spacer (107) is arranged separating the side edge (111) located at least in the effective area of the nozzles of the nozzle plate (113) during the feed direction (V) of the medium (101), so that the medium (101) is movable relative to the spacer (107) in the feed direction (V) even when printing on the medium (101).
2. Inkjet printing device according to claim 1 characterized in that the spacer (107) is spaced apart from the nozzle plate (113).
3. Inkjet printing device according to claim 1 or 2 characterized in that the spacer (107) is formed by a flat profile with flat sides and side edges extending between them, wherein the flat side facing the nozzle plate (113) is aligned parallel to the nozzle plate (113).
4. Inkjet printing device according to at least one of the preceding claims, characterized in that the spacer (107) is designed to be adjustable relative to the printing unit (105) in a direction (Q) perpendicular to the side edge (111) and parallel to the interrupted support surface.
5. Inkjet printing device according to at least one of the preceding claims, characterized in that the spacer (107) is designed to be height-adjustable relative to the nozzle plate (113).
6. Inkjet printing device according to at least one of the preceding claims, characterized in that the spacer (107) is held at its end, which is arranged at a distance with respect to the interrupted support surface in a direction parallel to the interrupted support surface and perpendicular with respect to the side edge (111) of the medium (101), by means of a holder (115) on a frame part (117) of the printing table (103) which is arranged at a distance with respect to the interrupted support surface and below the interrupted support surface.
7. Inkjet printing device according to claim 6 characterized in that the holder (115) on the frame part (117) of the printing table (103) is supported on the frame part (117) by means of an adjustment device for adjusting the height of the holder (115) relative to the frame part (117).
8. Inkjet printing device according to at least one of the preceding claims, characterized in that the printing table (103) comprises a web with several support elements (119, 119', 119“, 119'“, 119““, 119““', 119“““, 123, 125) oriented transversely to the feed direction (V) and spaced apart from one another, wherein the interrupted support surface is formed by the support elements (119, 119', 119“, 119'“, 119“““, 119“““, 123, 125), and wherein preferably the web is a roller web and the support elements (119, 119', 119“, 119““, 119““’, 119“““, 123, 125) are cylindrical rollers.
9. Inkjet printing device according to at least one of the preceding claims, characterized in that the interrupted support surface is arc-shaped, in particular circular segment-shaped, in its cross-section along the transport direction (V).
10. Inkjet printing device according to at least one of the preceding claims, characterized in that the printing unit (105) is designed to be height-adjustable relative to the printing table (103) and thus also to the interrupted support surface, wherein the spacer (107) is designed in such a way that it can be positioned in a variably adjustable working position on one or more stationary support parts (121, 12T) of the printing unit (105) that are arranged downstream and upstream of the print head (109) in the feed direction (V).
11. Inkjet printing device according to at least one of the preceding claims, characterized in that the spacer (107) is associated with an adjustment device for its adjustment in a direction perpendicular to the side edge (111) and parallel to the interrupted support surface, wherein the frame part (117) is part of the adjustment device.
12. Inkjet printing device according to claim 8 relating to claim 6 or 7, characterized in that a support element (119) of the support elements (119, 119', 119", 119'", 119"", 119""'; 119""", 123, 125) is associated with the printhead (109), wherein the holder (115) comprises a recess designed to enclose the support element (119) without contact.
13. Inkjet printing device according to at least one of the preceding claims characterized in that the inkjet printing device comprises at least one sensor, preferably at least two sensors spaced apart from each other in the feed direction, which are designed to detect the movement of the side edge in a direction (Q) perpendicular to the side edge (111) and parallel to the interrupted support surface, wherein the inkjet printing device is designed to compensate for the movement of the side edge (111) by a corresponding movement of the spacer (107).
14. Inkjet printing device according to at least one of the preceding claims, characterized in that the inkjet printing device comprises at least one second spacer (107') for maintaining a distance greater than zero between the second side edge (11T) of the medium (101), which is aligned in the feed direction (V) and lies within the effective area of the nozzles of a second nozzle plate (113') of a second printhead (109') of the printing unit (105), and the second spacer (107'), wherein the second spacer (107') is arranged separating the second side edge (11T) at least during the feed of the medium (101) in the feed direction (V), and thus between the second nozzle plate (113') and the second side edge (11T), so that even during printing of the medium (101) the medium (101) is oriented in the feed direction (V) relative to the second spacer (107') is movable.