Digital printing machine with one print bar for inkjet printing

Abstract

A digital printing machine comprising a printing bar (2) for inkjet printing, characterized in that the printing bar (2) is adjustably mounted in a working position and a retracted position, that an adjustable roller (10) and a spring-loaded roller (9) form a first arrangement and are arranged opposite each other, that a rail (7) forms a second arrangement and is located between the adjustable roller (10) and the spring-loaded roller (9) when the printing bar (2) is moved into the working position, that the rail (7) is not located between the adjustable roller (10) and the spring-loaded roller (9) when the printing bar (2) is moved into the retracted position, and that one of the two arrangements is arranged on the printing bar (2) and the other of the two arrangements is arranged separately from the printing bar (2).

Description

[0001] The present invention relates to a digital printing machine comprising a printing bar for inkjet printing.

[0002] US Patent 2013 / 0307893 A1 describes such a digital printing machine. In this digital printing machine, bushings are arranged on a printing bar, and guide pins are arranged separately from the printing bar. When the printing bar is moved into a working position, the bushings are slipped over the guide pins.

[0003] The invention is based on the objective of creating another digital printing machine.

[0004] This problem is solved by a digital printing machine comprising a print bar for inkjet printing, characterized in that the print bar is adjustably mounted in a working position and a retracted position, that an adjustable roller and a spring-loaded roller form a first arrangement and are arranged opposite each other, that a rail forms a second arrangement and is located between the adjustable roller and the spring-loaded roller when the print bar is moved into the working position, that the rail is not located between the adjustable roller and the spring-loaded roller when the print bar is moved into the retracted position, and that one of the two arrangements is arranged on the print bar and the other of the two arrangements is arranged separately from the print bar.

[0005] Accordingly, either the rail can be attached to the pressure beam and the two rollers can be arranged separately from the pressure beam, or the two rollers can be attached to the pressure beam and the rail can be arranged separately from the pressure beam. The arrangement arranged separately from the pressure beam – in one case the rail and in the other case the two rollers – can be mounted on a frame relative to which the pressure beam is adjustable into the two positions.

[0006] The digital printing machine according to the invention is advantageous with regard to the maintenance of the printing bar. In the digital printing machine according to the invention, the mounting of the printing bar, in addition to the adjustments of the printing bar to the working position and the retracted position (which can be vertical adjustments), allows a horizontal adjustment of the printing bar to a maintenance position. Because the rail is moved, so to speak, outside the confines of the rollers when the printing bar is moved to the retracted position, the rollers cannot obstruct the adjustment of the printing bar from the retracted position to the maintenance position. When the printing bar is moved to the working position, the rail retracts into the roller arrangement formed by the rollers.

[0007] Additional advantages include the adjustable roller allowing for adjustment of the pressure beam perpendicular to the adjustment direction, and the spring-loaded roller enabling the elimination of bearing play.

[0008] The sub-requirements list advantageous further training opportunities.

[0009] In a further development advantageous for the positive-locking drive of the adjustable roller, the rail is combined with a rack and the adjustable roller is combined with a gear. Here, the gear can be in mesh with the rack when the pressure bar is in the working position, and disengaged when the pressure bar is in the retracted position.

[0010] In a further development that is advantageous with regard to very precise determination of the working position, the adjustable roller is adjustable towards and away from the spring-loaded roller by means of an adjustment device. The adjustment device can be an eccentric.

[0011] In a further development advantageous for synchronous operation of the two rollers, the gear is connected to another adjustable roller via a transmission, so that both adjustable rollers can be driven together by the rack and pinion via the gear. The transmission can be a bevel gear transmission with bevel gears.

[0012] In a further development that is advantageous with regard to freedom of play of the rail in the working position, the rail is clamped between the adjustable roller and the spring-loaded roller when the pressure beam is in the working position.

[0013] Further details can be found in the following description of exemplary embodiments and the accompanying drawing, which shows: Fig. 1. A fixed bearing and a sliding bearing for positioning a pressure beam, Fig. 2 an adjustable roller of the fixed bearing and an associated gear, Fig. 3 the gear in engagement with a rack of the pressure beam, Fig. 4 a rotation angle locking device of the gear designed as a spring, Fig. 5 a bevel gear drive for connecting the roller to another roller of the fixed bearing, Fig. 6 a rotation angle locking device of the gear designed as a spring-loaded rack and Fig. 7 a rotation angle locking device of the gear designed as a weight.

[0014] In the Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6 to Fig. 7 are corresponding elements designated with the same reference symbols.

[0015] In the Fig. Figure 1 shows a section of a digital printing press 1. The section shows a print bar 2, which carries a series of printheads 3 for inkjet printing. The series of printheads 3 runs perpendicular to a transport direction 4 of the substrate. The print bar 3 is supported at one end in a fixed bearing 5 and at the other end in a floating bearing 6 when the print bar 3 is in its operating position (so-called jetting position).

[0016] The fixed bearing 5 is formed by a rail 7 and four rollers 8, 9, 10, and 11, between which the rail 7 is clamped in the working position. The rollers 8 to 11 comprise two spring-loaded rollers 8, 9 and two adjustable rollers 10, 11. The spring-loaded rollers 8, 9 are each biased by a spring 40, which presses the spring-loaded roller against the rail 7 and the latter against one of the adjustable rollers 10, 11. One roller 9 of the spring-loaded rollers 8, 9, together with one roller 10 of the adjustable rollers 10, 11, forms a first pair of rollers that fixes the rail 7 in a direction X perpendicular to the transport direction 4. The other roller 8 of the spring-loaded rollers 8, 9 together with the other roller 11 of the adjustable rollers 10, 11 forms a second pair of rollers that fixes the rail 7 in a direction Y that is parallel to the transport direction 4.

[0017] The floating bearing 6 is formed by another rail 12 and a third pair of rollers, which, in the working position, fixes the other rail 12 in the Y direction. The third pair of rollers comprises a spring-loaded roller 13 and an adjustable roller 14. The two rails 7, 12 each have a cross-section with side surfaces on which the rollers run when the pressure beam 2 is moved into the working position. The adjustment of the pressure beam 2 into its working position takes place in a direction relative to the plane of the image. Fig. 1. Perpendicular direction. Each pair of rollers is assigned two parallel side surfaces of the respective rail 7, 12. The cross-section of the rails 7, 12 is rectangular; the rails 7, 12 are square rails. The rails 7, 12 extend in their longitudinal direction – thus, the direction perpendicular to the image plane is... Fig. 1. Perpendicular direction is meant – perpendicular to the longitudinal direction of the pressure bar 2 and perpendicular to the transport direction 4. The rails 7, 12 are attached to the pressure bar 2 and are inserted between the roller pairs when the pressure bar 2 is moved into its working position. When the pressure bar 2 is not in its working position and is instead in a position retracted from the substrate transport path, the rails 7, 12 are not enclosed between the roller pairs but are pulled out of them. Moving the pressure bar 2 into the working position and into the retracted position can be motor-driven, and the pressure bar 2 can be guided by a guide 47. The retracted position can be an intermediate position into which the pressure bar 2 is moved in order to subsequently move it horizontally in direction X from the area above the substrate transport path into a maintenance position.The rollers 8 to 11, 13 and 14 are each mounted in a frame 15, relative to which the pressure bar 2 is adjustable.

[0018] In the Fig. 2 are the pressure bar 2 and the adjustable roller 10 from the viewing direction 16 (compare Fig. 1) as shown. In this illustration, the printheads 3 arranged in a row on the print bar 2 and the nozzle plates 17 of the printheads 3, which serve to eject the ink, can be seen. It is also shown that the rail 7 is combined with a rack 18, wherein the rack 18 and the rail 7 are either manufactured in one piece or manufactured in two pieces and then joined together. The longitudinal direction of the rack 18, like the longitudinal direction of the rail 7, is parallel to a direction Z in which the print bar 2 can be adjusted into and out of the working position. As previously described, a side surface of the rail 7 forms a running surface or guide track 19 for the roller 10. A toothing 20 of the rack 18 projects beyond the guide track 19 in the X direction. A rolling line of the toothing 20 of the rack 18 can be coincident with the guide track 19 of the rail 7.

[0019] A gear 21 has teeth 22 that could, but need not, extend over the entire circumference of the gear 21. In the gear 21 shown, the teeth 22 extend only over a portion of the circumference. The gear 21 and the roller 10, which is coaxial with it, can either be manufactured in one piece or in two pieces and then joined together in a rotationally fixed manner. The teeth 22 of the gear 21 project radially beyond a circumferential running surface 23 of the roller 10. A pitch circle of the teeth 22 of the gear 21 can be coincident with the running surface 23 of the roller 10.

[0020] A return spring 24, acting as a rotation angle locking device, returns the gear 21 and the roller 10 to a specific rotational angle position in which a first tooth gap 25 of the toothing 22 of the gear 21 is correctly aligned to receive a first tooth 26 of the toothing 20 of the rack 18 when the pressure bar 2 is moved into the working position. The "first" tooth gap 25 and the "first" tooth 26 are so named because, when the pressure bar 2 is moved, they are the first to engage with each other, i.e., before all other tooth gaps and teeth. In this embodiment, the return spring 24 is designed as a helically wound tension spring. The specific rotational angle position is determined by a stop 27. A lever 28 is attached to the gear 21 and abuts the stop 27.Instead of the lever 28, another projection could also cooperate with the stop 27, which could be attached to or integrally formed on the gear 21 or the roller 10. In the illustrated embodiment, the lever 28 serves to abut the stop 27 and simultaneously as the point of force application for the return spring 24. A common axis of rotation 29 of the roller 10 and the gear 21 is mounted in an eccentric 30, which is pivotable about a rotary joint 31.

[0021] A scale 32 is arranged on the eccentric 30, from which the respective setting of the eccentric 30, and thus the current position of the roller 10, can be read. To secure the respective setting of the eccentric 30, it can be designed to be self-locking, e.g., as a self-locking eccentric bushing, or supplemented with a holding device, e.g., a clamping screw. By means of the eccentric 30, the position of the roller 10, and thus of the pressure bar 2, can be adjusted in the X direction (compare Fig. 1) be adjusted. This is necessary, for example, so that the pressure bar 2 has a correct position in direction X relative to a substrate transport device 33 and the substrate 34 on it. The substrate transport device 33 can be an endless conveyor belt or a drum, and the substrate can be a web or a sheet of paper or cardboard.

[0022] In the Fig. Figure 3 shows the interaction of the gear 21 with the rack 18 when adjusting the pressure bar 2 in the Z direction towards the substrate transport device 33 into the working position. For clarity, the adjustment device (eccentric 30, scale 32) and the stop 27 are not shown. The downward-moving rack 18 drives the gear 21, which in turn forces the roller 10 to rotate. This ensures that the running surface 23 of the roller 10 rolls smoothly on the guide track 19. During each rolling operation – regardless of the direction of rotation of the roller 10, i.e., both when lowering the pressure bar 2 into the working position and when raising the pressure bar 2 into the retracted position – the same surface point of the running surface 23 contacts the same surface point of the guide track 19. This is achieved by ensuring that always the first tooth 26, and no other tooth, engages in the first tooth gap 25.Thus, manufacturing tolerances of the running surface 23 and the guide track 19 are reproducibly applied with every movement, and these manufacturing tolerances are thereby compensated for during the alignment of the pressure beam 2. When the pressure beam 2 moves downwards into the... Fig. In the working position shown in Figure 3, the gear 21 and the roller rotate clockwise and the return spring 24 is tensioned. When the pressure beam 2 moves upwards into the position shown in Figure 3, the pressure beam 21 rotates clockwise and the return spring 24 is tensioned. Fig. In the retracted position shown in Figure 2, gear 21 and roller 10 rotate counterclockwise, and the return spring 24 is relaxed to a remaining preload. Roller 11 and roller 14, like roller 10, are equipped with a secondary gear. The rail 7 of the fixed bearing 5 can have, in addition to the rack 18 for the gear (secondary gear) 21 of roller 10, another rack for the secondary gear of roller 11, and the rail 12 of the floating bearing 6 has a rack for the secondary gear of roller 14. Rollers 11 and 14, like roller 10, are mounted in an eccentric and adjustable by means of this, but not in the X direction like roller 10, but in the Y direction.

[0023] In the Fig. Figure 4 shows a modification using the example of the adjustable roller 10, in which the lever 28 and the stop 27 are omitted. This is necessary for the correct engagement of the first tooth 26 in the first tooth gap 25 (compare Figure 4). Fig. 2) The required angular position of the gear 21 is ensured solely by the return spring 24, which is attached at one end to a fixed mounting point 35 on the frame 15 and at the other end to an eccentric mounting point 36 on the gear 21 or on the roller 10. The mounting points 35 and 36 can be pins for attaching eyelets located at the ends of the return spring 24. The return spring 24 is designed as a helically wound tension spring. The angular position required for correct gear engagement is determined by a minimum distance between the mounting points 35 and 36, and thus by a minimum tension in the return spring 24.

[0024] In the Fig. Figure 5 shows a further modification in which the gear of roller 11 and the rack intermittently meshing with this gear are omitted. A first bevel gear 37 is arranged coaxially with roller 10 and gear 21 and is rotationally fixed to them. A second bevel gear 38 is also arranged coaxially with roller 11 and is rotationally fixed to them. "Rotationally fixed to them" here refers to either a one-piece or a composite construction. The geometric axes of rotation of the two rollers 10 and 11, and thus of the two bevel gears 37 and 38, are perpendicular to each other. The two bevel gears 37 and 38 mesh with each other and together form a transmission for transmitting torque from gear 21 to roller 11.The two rollers 10 and 11, which have the same diameter, are driven together by the rack 18 via the gear 21, and the transmission (bevel gears 37 and 38) ensures synchronous operation of the two rollers 10 and 11 because the bevel gears 37 and 38 have the same diameter. The rack 18 and the gear 21 are therefore common drive elements for the rollers 10 and 11. Furthermore, in... Fig. 5 to recognize that the sprung rollers 8, 9 are rotatably mounted in linearly adjustable forks 39, which are loaded by the springs 40.

[0025] In the Fig. Figure 6 shows a further modification in which the correct rotational angle for the engagement of the first tooth 26 in the first tooth gap 35 is ensured by a further rack 41, which meshes permanently with the gear 21, i.e., not only when the pressure bar 2 is in the working position, but also when it is in the retracted position. The further rack 41 is guided in a linear guide 42 and moves antiparallel to the rack 18 when the rack 18 engages with the gear 21 and drives it, which in turn drives the further rack 41. The aforementioned correct rotational angle is determined by a stop 43, against which the further rack 41 is pressed by the return spring 24 when the rack 18 is disengaged from the gear 21.In this embodiment, the return spring 24 is a compression spring and is supported at one end on the frame 15 and at the other end on the further rack 41. With a correspondingly long further rack 41, the roller 10 can complete several revolutions while continuously rolling on the rail 7, e.g., during the adjustment of the pressure bar 2 with the rail 7 from the retracted position to the working position. During this adjustment from the retracted position to the working position, the return spring 24 is tensioned, and during the opposite adjustment from the working position to the retracted position, the return spring 24 is relaxed again until a residual preload remains.

[0026] In the Fig. Figure 7 shows a further modification in which toothed elements are omitted. Here, the spring 40 is a leaf spring or a leaf spring assembly and generates a clamping force to clamp the rail 7 between the rollers 9, 10, the clamping force being so high that the adjustable roller 10 rolls on the rail 7 with virtually no slippage. While in the previously described embodiments the reproducibly congruent rolling of the running surface 23 on the guide track 19 is ensured by means of the toothed elements via positive locking, in the embodiment shown in Fig. 7 is ensured by frictional engagement. An adjusting mass 44 is attached to the roller 10 at the eccentric mounting point 36. The weight of this mass holds the roller 10 in the shown rotational angle position as long as the roller 10 is out of rolling contact with the rail 7. When the pressure bar 2 is moved into the working position, the rail 7 moves into a gap 45 between the rollers 9 and 10. In doing so, the rail 7, via an insertion chamfer or ramp 46 formed at its end, pushes the spring-loaded roller 9 against the force of the spring 40 out of the adjustment path of the rail 7 and away from the adjustable roller 10. Fig. 10, so to the right.

[0027] In the Fig. 3, Fig. 4, Fig. 5, Fig. 6 to Fig. In the 7 illustrated embodiments, all adjustable rollers 10, 11 and 14 are each mounted in an eccentric 30, as shown in Fig. 2 shown using the example of roll 10, stored, even if this storage is not shown in the drawing.

[0028] In modifications not shown in the drawing, the eccentrics 30 are replaced by other adjustment devices, e.g. by adjustment screws with differential threads, by means of which the rotation axes of the adjustable rollers 10, 11 and 14 can be finely adjusted.

[0029] In all embodiments, the rail 7 of the fixed bearing 5 moves from the retracted position to the working position into the gap 45 (compare Fig. 7) between the four rollers 8 to 11 and the rail 12 of the sliding bearing 6 dips into the space between rollers 13 and 14. When the pressure bar 7 is in the retracted position, the two rails 7, 12 are outside the two spaces. Reference symbol list 1 digital printing machine 2 pressure bars 3 Printhead 4. Transport direction 5 fixed bearings 6 loose bearings 7 rail 8 spring-loaded roller 9 spring-loaded roller 10 adjustable casters 11 adjustable casters 12 more rails 13 spring-loaded roller 14 adjustable casters 15 frame 16 View direction 17 nozzle plate 18 Rack and pinion 19 Guide rail 20 gear teeth 21 gear 22 gearing 23 Running surface 24 Return spring 25 first gap in teeth 26 first tooth 27 attacks 28 levers 29 Rotation axis 30 eccentrics 31 Swivel joint 32 scale 33 Material transport device 34 Printing material 35 fixed mounting point 36 eccentric mounting point 37 first bevel gear 38 second bevel gear 39 Fork 40 springs 41 more rack and pinion 42 Linear guide 43 attacks 44 Adjustment dimensions 45 space 46 Inlet chamfer 47 Leadership x direction y direction z direction

Claims

A digital printing machine comprising a printing bar (2) for inkjet printing, characterized in that the printing bar (2) is adjustably mounted in a working position and a retracted position, that an adjustable roller (10) and a spring-loaded roller (9) form a first arrangement and are arranged opposite each other, that a rail (7) forms a second arrangement and is located between the adjustable roller (10) and the spring-loaded roller (9) when the printing bar (2) is moved into the working position, that the rail (7) is not located between the adjustable roller (10) and the spring-loaded roller (9) when the printing bar (2) is moved into the retracted position, and that one of the two arrangements is arranged on the printing bar (2) and the other of the two arrangements is arranged separately from the printing bar (2). Digital printing machine according to claim 1, characterized in that the rail (7) is combined with a rack (18) and the adjustable roller (10) is combined with a gear (21). Digital printing machine according to claim 2, characterized in that the gear (21) is in tooth engagement with the rack (18) when the printing bar (2) is in the working position, and is out of tooth engagement when the printing bar (2) is in the retracted position. Digital printing machine according to one of claims 1 to 3, characterized in that the adjustable roller (10) can be adjusted towards and away from the spring-loaded roller (9) by means of an adjustment device. Digital printing machine according to claim 4, characterized in that the adjustment device is an eccentric (30). Digital printing machine according to one of claims 2 to 5, characterized in that the gear (21) is connected to a further adjustable roller (11) via a transmission, so that the two adjustable rollers (10, 11) can be driven together by the rack (18) via the gear (21). Digital printing machine according to claim 6, characterized in that the transmission is a bevel gear transmission with bevel gears (37, 38). Digital printing machine according to one of claims 1 to 7, characterized in that the rail (7) is clamped between the adjustable roller (10) and the spring-loaded roller (9) when the printing bar (2) is in the working position.

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