Printing device for individually printing webs or sheets of printing substrates

Abstract

A printing device for individually printing webs or sheets of printing substrates according to the ink jet principle comprises a plurality of identical printing units (2, 2.1, 2.2) that can be individually positioned transversely, every printing unit comprising two print heads (23, 24) and being suitable to form a separate printing region or, together with one or more neighboring printing units, to form a common, continuous printing region without ink voids.

Description

[0001] The present invention relates to a printing device for individually printing on web-shaped or sheet-shaped printing materials according to the preamble of claim 1.

[0002] Particularly in the fields of paper processing and the manufacture of boxes and containers from greyboard or corrugated board, printing devices are known that are suitable for individually printing predetermined areas of a web or sheet of substrate. The substrate is guided in a horizontal plane along a printhead that remains stationary during the printing process. The printhead usually operates on the inkjet principle.

[0003] It is often unnecessary to print the entire surface of a substrate. Printing a strip is usually sufficient. For cost reasons, WO2016174643A1 suggests using a printhead with a print width significantly smaller than the width of the substrate. The printhead's print width determines the maximum width of the printable strip.

[0004] Document WO 2011 / 157282 A1 discloses a printing device according to the preamble of claim 1.

[0005] To allow for product-dependent variation of the printable area's position, a printhead positioning device is proposed. For this purpose, the printhead is mounted in the machine frame by means of a transversely arranged linear guide. Along this guide, the printhead can be freely positioned perpendicular to the feed direction of the substrate.

[0006] The printhead is mounted in a carriage which, in addition to components for supplying and controlling the printhead, also includes a feed drive. A gear in this feed drive engages with a rack fixed to the frame, which runs parallel to the linear guide.

[0007] The maximum printable width in a single pass is determined by the printhead. The cost of a printhead increases disproportionately with its print width. Therefore, efforts are made to use printheads with the smallest possible print width. This correspondingly limits the design possibilities of the printed image, especially when multiple, separate print images are printed across the printhead.

[0008] In contrast, the object of the present invention is to provide a printing device, in particular for printing on cardboard or corrugated board or similar materials, by means of which the aforementioned disadvantages can be avoided in a technically simple manner using cost-effective means.

[0009] The stated problem is solved according to the invention in a generic printing device with the features of the characterizing part of claim 1. Advantageous embodiments of the invention are characterized by the features specified in the dependent claims.

[0010] According to the invention, the printing device comprises a plurality of printing units, the printing units being arranged side by side in the material flow direction. Each of the printing units can be individually positioned along a linear guide by means of a feed device transverse to the material flow direction.

[0011] Using multiple printing units with small print widths significantly expands the design possibilities of the printed image at low cost, as they can be freely positioned relative to each other perpendicular to the material flow direction. The positions of the printable strips on the substrate can be selected within a wide range.

[0012] Furthermore, the large number of identical printheads leads to redundancy, thus increasing the availability of the printing device.

[0013] Each pressure unit consists of a frame that houses a primary reservoir (serving as the main supply), a secondary reservoir (serving as a buffer), and a pump for supplying the pressurized fluid. The frame can also serve as a housing.

[0014] The frame of the printing unit accommodates at least two printheads. The printheads are oriented in the same printing direction and aligned with the same printing plane. The printing plane corresponds to a plane defined by the substrate. The use of a large number of identical printheads with a relatively small print width allows for easy adaptation to different customer requirements by adjusting the number of identical printing units.

[0015] Preferably, the printheads of a printing unit are arranged transversely offset from one another. In this way, the printheads can print a wider track together. In an advantageous embodiment, the printing areas of the printheads of the same printing unit adjoin each other directly in the transverse direction. This maximizes the area that can be printed with just one printing unit. In a particularly advantageous embodiment, the printheads are arranged transversely such that their individual printing areas slightly overlap. This prevents defects in the printed image due to geometric tolerances.

[0016] An advantageous arrangement of the printheads in a printing unit that is offset in the direction of material flow is beneficial. This allows for a simple and sufficiently robust design of the printheads and their mountings, particularly in the case of transversely adjacent printing areas.

[0017] A particularly advantageous feature is the offset contour of the printing units when viewed from the printing plane. The printheads of each unit are offset from one another longitudinally and transversely within each leg of the offset. Using a common guide rail, this allows the printing units to be positioned transversely in such a way that several adjacent units together form a continuous, uninterrupted printing area. This achieves a very high degree of variability in the printing areas within a compact design.

[0018] The delivery devices enable the printing units to be individually and automatically positioned in a transverse direction. For this purpose, each printing unit has a delivery drive with a controllable motor. Alternatively, a single delivery drive can be used that temporarily acts on a single printing unit.

[0019] The invention is then explained with reference to the figures, to which reference is made for all details not mentioned in the description, using an exemplary embodiment. The figures show: Fig. 1 Perspective view of a printing device with three identical printing units; Fig. 2 View of a printing device with three identical printing units facing opposite the printing direction; Fig. 3 View of a pressure unit in a transverse direction.

[0020] In Fig. 1 Three identical pressure units 2.1, 2.2, 2.3 of a printing device are shown. The representation of three pressure units 2.1, 2.2, 2.3 is merely an example. Depending on the application, the printing device can also have two or any number of pressure units 2.1, 2.2, 2.3.

[0021] The printing units 2.1, 2.2, 2.3 are fixedly arranged in a machine frame 1 for the printing process. The substrate (not shown) is moved along the printheads 23, 24 in a material flow direction 100. The material flow direction 100 is horizontal and defines the longitudinal axis of the printing device. A transport device 60 of a known type is provided for feeding the substrate. Fig. 1 und Fig. 2 The figures only show a section of this transport device 60 arranged in the machine frame 1.

[0022] The printing units 2.1, 2.2, 2.3 are mounted in the machine frame 1 by means of linear guides 31. The guide carriages 33 are attached to the printing units 2.1, 2.2, 2.3. Together, they are mounted on two parallel guide rails 32. The guide rails 32 are oriented transversely to the material flow direction 100. This allows the printing units 2.1, 2.2, 2.3, and thus their printing areas 201, 202, 203, 204, to be positioned in a transverse direction 200. The changes in position are Fig. 2 The double arrows indicate this. The printing units 2.1, 2.2, 2.3 are arranged side by side with respect to the material flow direction 100°.

[0023] The printheads 23, 24 of the print units 2.1, 2.2, 2.3 form a common print plane. This is identical to the substrate plane 1000 defined by the substrate. In the Fig. 1 In the illustrated embodiment, a vertical printing direction 300 from bottom to top is provided. Other printing directions are also possible, such as from top to bottom.

[0024] The structure of a single printing unit 2, 2.1, 2.2, 2.3 is illustrated below using an example. Fig. 3 The following is explained. Two identical printheads 23, 24 are mounted in the same orientation within a common frame 20. Each is capable of simultaneously generating a multitude of adjacent print dots in a common printing direction 300. The arrangement of these print dots runs as a line in a transverse direction 200 and defines the print widths 201, 202, 203.1, 203.2, 203.3. The two printheads 23, 24 are offset from each other both in the material flow direction 100 and in the transverse direction 200.

[0025] A primary pressure medium reservoir 21 is attached to the frame 20. This can be operated as described in Fig. 1 and Fig. 3 The system consists of several containers. The primary reservoir 21 is connected via suction lines (not shown) to a pump 25 located inside the frame 20, which serves as a housing. On the pressure side, the pump 25 is connected via lines (also not shown) to a secondary pressure medium reservoir 22. This supplies the printheads 23 and 24 with pressure medium via lines (also not shown).

[0026] The rate of change in the instantaneous delivery of printing medium by the printheads 23, 24 can be significantly greater than the dynamics of the pump 25 allow, depending on the print image to be produced and the transport speed of the substrate. The secondary reservoir 22, arranged at the same vertical height as the printheads 23, 24, is suitable for buffering such short-term fluctuations in printing medium demand. It allows for more consistent and therefore gentler operation of the pump 25. The secondary reservoir 22 is considerably smaller than the primary reservoir 21.

[0027] On one side of the frame 20 pointing in the material flow direction 100, two guide carriages 33 of the linear guides 31 are attached. They are arranged one above the other and aligned parallel to each other.

[0028] A feed device 30 allows the printing unit 2, 2.1, 2.2, 2.3 to be positioned along the linear guide 31 in a transverse direction 200. For this purpose, a rack 35 is arranged parallel to the linear guide 31 in the machine frame 1. The gear 36 of a feed drive 34 engages with this frame-mounted rack 35. The gear 36 is located on the frame 20 of the printing unit 2, 2.1, 2.2, 2.3 and is driven by a controllable motor 37. The controllable motor 37 of the feed drive 34 is mounted inside the printing unit 2, 2.1, 2.2, 2.3. It is connected via cables to a central control unit 70 of the printing device.

[0029] Adjacent pressure units 2, 2.1, 2.2, 2.3 can be positioned relative to each other in a transverse direction 200 by means of the positioning device 30 such that the pressure areas 201, 202, 203, 204 have a predetermined distance 205 from each other. The smallest possible distance is achieved when the two adjacent pressure units 2, 2.1, 2.2, 2.3 are brought to a stop position.

[0030] Manufacturing and assembly tolerances result in different positioning of the transverse printing areas 203.1, 203.2, 203.3 of the printing units 2, 2.1, 2.2, 2.3 relative to each other in this block configuration. To compensate for these differences, spacer plates 38 are provided between the printing units 2, 2.1, 2.2, 2.3. The spacer plates 38 are each attached to the frame 20 of a printing unit 2, 2.1, 2.2, 2.3. Their thickness is selected such that the transverse positioning of the printing areas 203.1, 203.2, 203.3 of two adjacent printing units 2, 2.1, 2.2, 2.3 relative to each other corresponds to a predetermined dimension.

[0031] Alternatively, the spacer plates 38 can be designed to be adjustable by means of pressure-release screws or other adjustable spacer elements such as clampable eccentrics can be used.

[0032] Also housed in the frame 20, which is designed as a housing, are electronic components 26 required for controlling the printheads 23, 24. These electronic components 26 are also connected to the control unit 70 of the printing device.

[0033] Each printhead 23, 24 forms a transverse track 221, 222 by moving along the linear guide 31, which defines the printable area. The first printhead 23 forms a first transverse track 221, and the second printhead 24 forms a second transverse track 222. Both tracks 221, 222 are necessarily parallel to each other and to the linear guide 31. In the material flow direction 100, the tracks 221, 222 are spaced 220 apart, a distance determined by the arrangement of the printheads 23, 24 within the printing unit 2, 2.1, 2.2, 2.3. The first tracks 221 of adjacent printing units 2, 2.1, 2.2, 2.3 are identical. Likewise, the second tracks 222 of the adjacent printing units 2, 2.1, 2.2, 2.3 are identical.

[0034] The printing area 201, 202 of a printhead 23, 24 within its track 221, 222 results from the design of the printhead 23, 24 and its transverse position. The printheads 23, 24 of a printing unit 2, 2.1, 2.2, 2.3 are arranged in the transverse direction 200 such that their printing areas 201, 202 adjoin each other. To reliably prevent defects in the print, the two printing areas 201, 202 of a printing unit 2, 2.1, 2.2, 2.3 overlap slightly, forming a first overlap 211.

[0035] If two adjacent pressure units 2, 2.1, 2.2, 2.3 are positioned in a block arrangement relative to each other, they form a common pressure area 204. This arrangement is described in Fig. 2 This is illustrated using the two printing units 2.1 and 2.2 and is transferable to all adjacent printing units 2, 2.1, 2.2, 2.3. Analogous to the first printing area 201 of the first printhead 23 and the second printing area 202 of the second printhead 24 of the same printing unit 2, 2.1, 2.2, 2.3, the printing areas 203.1, 203.2, 203.3 of adjacent printing units 2, 2.1, 2.2, 2.3 adjoin each other directly. They can also overlap and form a second overlay 212 to prevent defects in the printed image.

[0036] The printing units 2, 2.1, 2.2, 2.3 each have a [missing information] in the substrate plane. Fig. 2 The dotted, offset contour 27 is shown. The offset allows the printheads 23, 24 of each printing unit 2, 2.1, 2.2, 2.3 to be arranged offset from one another in the material flow direction 100 and in the transverse direction 200, such that, as in Fig. 2The first printing area 201 of a first printhead 23 is shown to directly adjoin the second printing area 202 of a second printhead 24 of the adjacent printing unit 2.2. As an alternative to a simple offset, the contour 27 can have a toothed profile. Reference symbol list

[0037] 1 Frame 2 Printing unit 2.1 First printing unit 2.2 Second printing unit 2.3 Third printing unit 20 Frame 21 Primary reservoir 22 Secondary reservoir 23 First printhead 24 Second printhead 25 Pump 26 Electronic components 27 Contour in substrate plane 30 Feeding device 31 Linear guide 32 Guide rail 33 Guide carriage 34 Feed drive 35 Rack and pinion 36 Gear 37 Controllable motor 38 Spacer plate 60 Transport device 70 Control 100 Material flow direction 200 Transverse direction 201 Printing area of ​​the first printhead 202 Printing area of ​​the second printhead 203.1 Printing area of ​​the first printing unit 203.2 Printing area of ​​the second printing unit 203.3 Printing area of ​​the third printing unit 204 Common fourth printing area 205 Distance between adjacent Print areas 211 First overlap within a print unit 212 Second overlap between two print units 220 Distance in material flow direction 221 First transverse track 222 Second transverse track 300 Print direction 1000 Substrate level

Claims

1. A printing device for individually printing webs or sheets of printing substrates in accordance with the inkjet principle, wherein the printing substrate defines a printing substrate plane, and wherein said printing device comprises at least • a machine frame (1), • a transport device (60) that is designed for transporting the printing substrate in an essentially linear material flow direction (100) within the one printing substrate plane, • two identical printing units (2, 2.1, 2.2, 2.3) that are arranged behind one another in a direction (200) extending transverse to the material flow direction (100), wherein each of the at least two printing units (2, 2.1, 2.2, 2.3) has a frame (20) and, arranged in the frame (20), at least • a first print head (23) that is designed and can be controlled in such a way that it is suitable for dispensing and transferring liquid printing medium to the printing substrate in a predefined manner, • a primary reservoir (21) for storing a first quantity of liquid printing medium, • a secondary reservoir (22) for storing a second quantity of liquid printing medium, and • a pump (25) for conveying the liquid printing medium, wherein the at least one primary reservoir (21), the at least one secondary reservoir (22) and the at least one pump (25) are with respect to the liquid printing medium connected to one another and to the at least one first print head (23) in an effectively conveying manner in order to supply the at least one first print head (23) with liquid printing medium, wherein the at least two printing units (2, 2.1, 2.2, 2.3) respectively have at least one second print head (24), wherein the first and the second print head (23, 24) of the same printing unit (2, 2.1, 2.2, 2.3) are respectively accommodated in a common frame (20) of the printing unit (2, 2.1, 2.2, 2.3), and wherein the printing planes of the at least two print heads (23, 24) of a printing unit (2, 2.1, 2.2, 2.3) are identical to the same printing substrate plane (1000), characterized in that the printing regions (203.1, 203.2) of at least two directly adjacent printing units (2.1, 2.2) alternately form at least in the transverse direction (200) either a common and uninterrupted printing region (204), wherein the individual printing regions (203.1, 203.2) of the at least two directly adjacent printing units (2.1, 2.2) directly follow one another or partially overlap and respectively form a second overlapping region (212) or printing regions (204) that are separated from one another.

2. The printing device according to claim 1, characterized in that the at least two print heads (23, 24) of the same printing unit (2, 2.1, 2.2, 2.3) are arranged offset to one another in the transverse direction (200) in such a way that their printing regions (201, 202) partially overlap in the transverse direction (200) and form a first overlapping region (211).

3. The printing device according to claim 2, characterized in that the printing regions (201, 202) of a printing unit (2, 2.1, 2.2, 2.3) respectively correspond to a multiple of the overlap (211) of the printing regions (201, 202) in the transverse direction (200).

4. The printing device according to claim 1, characterized in that the at least two print heads (23, 24) of the same printing unit (2, 2.1, 2.2, 2.3) are arranged relative to one another in the transverse direction (200) in such a way that their printing regions (201, 202) directly follow one another in the transverse direction (200).

5. The printing device according to one of the preceding claims, characterized in that the at least two printing units (2, 2.1, 2.2, 2.3) are respectively accommodated in the common machine frame (1) so as to be individually movable in the transverse direction (200).

6. The printing device according to claim 5, characterized by at least one respective positioning device (30) of the at least two printing units (2, 2.1, 2.2, 2.3), wherein each positioning device (30) has at least one controllable motor (37) that communicates with the controller (70) of the printing device.

7. The printing device according to claim 5, characterized by a common positioning device of the at least two printing units (2, 2.1, 2.2, 2.3) with at least one controllable motor that communicates with the control (70) of the printing device, wherein the common positioning device is alternately operatively connected to one of the at least two printing units (2, 2.1, 2.2, 2.3).

8. The printing device according to one of the preceding claims, characterized in that the at least one secondary reservoir (22) of the at least two printing units (2, 2.1, 2.2, 2.3) is respectively arranged vertically at essentially the height of the at least two print heads (23, 24) of the same printing unit (2, 2.1, 2.2, 2.3).

9. The printing device according to one of claims 5 to 8, characterized in that at least one of the frames (20) of at least a first printing unit (2.1) of the at least two printing units (2, 2.1, 2.2, 2.3) has at least one spacer (38), wherein the at least one spacer (38) is arranged so as to face a second printing unit (2.2) arranged adjacent to the first printing unit (2.1) such that the spacer (38) limits the variable distance between the print heads (23, 24) of the first printing unit (2.1) and the print heads (23, 24) of the adjacent second printing unit (2.2) to a minimum size.

10. The printing device according to one of the preceding claims, characterized in that at least two print heads 23, 24 of the same printing unit (2, 2.1, 2.2, 2.3) are offset to one another in the material flow direction (100) in the common frame (20) in such a way that their printing regions are spaced apart from one another by a distance (220) in the material flow direction (100).

11. The printing device according to one of the preceding claims, characterized in that the at least two printing units (2, 2.1, 2.2, 2.3) respectively have such a cranked or toothed contour (27) in the printing substrate plane (1000) that these contours (27) of two adjacent printing units (2, 2.1, 2.2, 2.3) engage into one another.

Images