Digital printing machine with a thermal fusing unit

Abstract

A digital printing machine includes a thermal fixing unit (1) for fixing ink to a substrate (2). The fixing unit (1) is arranged on a curved deflection section (3) that deflects the substrate (2). The deflection section (3) has a U-shaped transport gap (4) in which the substrate (2) is transported. The transport gap (4) lies between a concave contact surface (5) and a convex contact surface (6). The substrate (2) is in contact with both the concave contact surface (5) and the convex contact surface (6) when the fixing unit (1) transfers heat to fix the ink to the substrate (2).

Description

[0001] The present invention relates to a digital printing machine comprising a thermal fixing device for fixing ink onto a substrate.

[0002] In such digital printing machines, the fixing device serves to solidify the ink of the printed image onto the substrate.

[0003] For example, US 11 633 963 B2 describes a fixing device for use in a printing system.

[0004] The purpose of the invention is to create another digital printing machine.

[0005] The problem is solved by a digital printing machine comprising a thermal fixing device for fixing ink onto a substrate, characterized in that the fixing device is arranged on a curved deflection section that deflects the substrate, that the deflection section has a U-shaped transport gap in which the substrate is transported, that the transport gap lies between a concave contact surface and a convex contact surface, and that the substrate is in contact with the concave contact surface and the convex contact surface when the fixing device transfers heat to fix the ink onto the substrate.

[0006] One advantage of the printing press according to the invention is that it has a particularly compact design and therefore only requires a small footprint, thus saving space in the printing room.

[0007] The compact design is achieved by arranging the fixing device not on a linear section of the substrate transport path, but on the curved deflection section of the substrate transport path.

[0008] The following training courses are available individually or in any combination: The concave contact surface can be formed by a conveyor belt located on the outside of the deflection section. The convex contact surface can be formed by a conveyor belt located inside the deflection section. The external conveyor belt can be guided by a concave belt guide. The concave belt guide can be heated, e.g., by heating fluid. The concave belt guide can be designed as a flexible, curved plate. This flexible plate can be pressed against the outer conveyor belt by a spring. The spring allows the flexible plate to be held under tension. The internal conveyor belt can be guided by a convex belt guide. The convex belt guide can be heated, e.g., by heating fluid. The outer conveyor belt can be driven at a faster speed than the inner conveyor belt, so that the concave contact surface has a higher surface velocity than the convex contact surface. Within an arc conveyor path, the deflection section can be located between a first arc conveyor belt and a second arc conveyor belt.

[0009] Further information can also be obtained from the following description of an exemplary embodiment and the associated drawing.

[0010] The only figure in it shows a section of a digital printing machine with a deflection section.

[0011] A digital printing press prints on sheet-shaped substrate 2 using an inkjet printing process. The substrate 2 is transported along a sheet transport path in the directions indicated by thick arrows 22 from a first sheet conveyor belt 13 to a substantially U-shaped deflection section 3 of the sheet transport path and from the deflection section 3 to a second sheet conveyor belt 14. The first sheet conveyor belt 13 is part of a drying section for lightly drying the substrate 2 before the actual ink fixation. The second sheet conveyor belt 14 is part of a cooling section for cooling the substrate 2 after ink fixation. Ink fixation is carried out by means of a fixing device 1 in the area of ​​the deflection section 3 by applying heat to the printed ink.

[0012] The deflection section 3 is formed by an outer conveyor belt 7 and an inner conveyor belt 8, which define a transport gap 4 between them. Thin arrows 23 indicate the directions of rotation of the two curved conveyor belts 13, 14 and the two conveyor belts 7, 8. The outer conveyor belt 7 is guided by rollers, including a drive roller 15 for driving the outer conveyor belt 7, a tension roller 16 loaded by a spring 21 for tensioning the outer conveyor belt 7, and deflection rollers 17 pivotally mounted in guides 18 for deflecting the outer conveyor belt 7 at the entrance and exit of the transport gap 4.The internal conveyor belt 8 is also guided by rollers, including a central roller 20 arranged coaxially in the center 19 of the deflection section 3, which serves as a drive roller to drive the internal conveyor belt 8, and deflection rollers 25 for deflecting the internal conveyor belt at the entrance and exit of the transport gap 4.

[0013] The drive roller 15 drives the outer conveyor belt 7 at a speed such that there is no speed difference between the concave contact surface 5 and the front side of the substrate 2 facing it in the transport gap 4. Simultaneously, the central roller 20 drives the inner conveyor belt 8 at a speed such that there is no speed difference between the convex contact surface 6 and the back side of the substrate 2 facing it in the transport gap 4. To ensure that both contact surfaces 5 and 6 rotate without slippage against the substrate 2, the concave contact surface 5, which has a radial distance from the center point 19 approximately corresponding to the thickness of the substrate 2, is driven slightly faster than the convex contact surface 6.

[0014] The inner conveyor belt 8 slides on a stationary convex belt guide 11. The convex belt guide 11 is rigid and has the shape of a ring segment. The outer conveyor belt 7 slides on an adjustable concave belt guide 9. The concave belt guide 9 has the shape of a curved plate or a bowl. The concave belt guide 9 is made of a flexible or elastic material that conducts heat well, such as a metal sheet or spring steel.

[0015] One end of the concave belt guide 9 is attached to a frame 24, and a spring 12 pulls at its other end. When the substrate 2 is in the transport gap 4, the tension exerted by the tension roller 16 on the section of the outer conveyor belt 7 located between the deflection rollers 25, which forms the concave contact surface 5, presses the concave contact surface 5 onto the substrate 2 and the substrate 2 onto the convex contact surface 6. This causes the substrate 2 to pass through the transport gap 4 in contact with both conveyor belts 7 and 8 on both sides. The substrate 2 is thus in heat-transferring contact with both the concave contact surface 5 and the convex contact surface 6.The force of the spring 12 adjusts the concave belt guide 9 towards the convex belt guide 11, so that the concave belt guide 9 nestles against the outer conveyor belt 7 while maintaining permanent contact with it.

[0016] A first piping system 26 for heating fluid 10, e.g., hot water, is arranged on the concave belt guide 9. The heating fluid 10 is circulated in the first piping system 26, which is part of a closed loop. The first piping system 26 can consist of a single, meandering pipe or of several pipes connected in parallel. The concave contact surface 5 is located on one front side of the concave belt guide 9, and the first piping system 26 is arranged on one rear side of the concave belt guide 9. The first piping system 26 is a pipe system that can be, for example, glued, soldered, or welded to the sheet metal of the concave belt guide 9. The first piping system 26 transfers its heat via the concave belt guide 9 to the external conveyor belt 7.

[0017] A second piping system 27 for heating fluid 10, e.g., hot water, is arranged on the convex belt guide 11. The heating fluid 10 is circulated in the second piping system 27. The second piping system 27 can be integrated into the same circuit as the first piping system 26 or into a different circuit. The second piping system 27 can consist of a single, meandering pipe or of several parallel pipes. The second piping system 27 is arranged within the convex belt guide 11 close to the convex contact surface 6 or even flush with the latter. The second piping system 27 can be formed by pipes cast into the convex belt guide 11 or by bores machined into the convex belt guide 11. The second piping system 27 transfers its heat to the inner conveyor belt 8.

[0018] The first conduit system 26 and the second conduit system 27 form a heating element for heating both sides of the substrate 2 and the ink printed on the substrate 2 – which may include several different colored inks – with the aim of fixing the ink to the substrate 2. This heating element thus functions as a component of the thermal fixing device 1 for ink fixation. This fixing device 1 is located in the section of the sheet transport path where the printed sheets are deflected from an original direction to an antiparallel opposite direction. This is the aforementioned deflection section 3, which can run along the sheet transport path in a circular arc, elliptical shape, or other curved form. Each sheet is thermally treated by the fixing device 1 during its passage through the deflection section 3.The fixing device 1, which also includes the belt guides 9, 11 and the conveyor belts 7, 8, operates according to the contact principle, whereby heat transfer takes place via body contact.

[0019] The following modifications are possible: In a modification, the first piping system 26 and / or the second piping system 27 is replaced by an electric heater. In a further modification, the concave belt guide 9 is omitted. Here, one or more of the rollers 15, 16, 17 are heated and transfer their heat to the outer conveyor belt 7. This acts as an intermediate heat storage device and transfers the heat absorbed by the roller(s) in the transport gap to the substrate 2. For this purpose, the outer conveyor belt 7 can be made of metal and, for example, be a steel belt. Reference symbol list 1 Fixing device 2. Printing material 3 Deflection section 4 Transport gap 5 concave contact surfaces 6 convex contact surfaces 7 external conveyor belt 8 internal conveyor belt 9 concave belt guide 10 Heating fluid 11 convex band guide 12 springs 13 first bow conveyor belt 14 second bow conveyor belt 15 Drive roller 16 Tension roller 17 Deflection roller 18 handlebars 19 Center 20 Central roller 21 spring 22 Arrow (direction of transport) 23 Arrow (direction of rotation) 24 frame 25 Deflection roller 26 first piping system 27 second line system QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 11 633 963 B2

[0003]

Claims

[1] Digital printing machine comprising a thermal fixing device (1) for fixing ink onto a substrate (2), characterized by , that the fixing device (1) is arranged on a curved deflection section (3) which deflects the printing material (2), that the deflection section (3) has a U-shaped transport gap (4) in which the printing material (2) is transported, that the transport gap (4) lies between a concave contact surface (5) and a convex contact surface (6), and that the substrate (2) is in contact with the concave contact surface (5) and the convex contact surface (6) when the fixing device (1) transfers heat to fix the ink to the substrate (2). [2] Digital printing machine according to claim 1, characterized by . that the concave contact surface (5) is formed by a conveyor belt (7) located on the outside of the deflection section (3), and that the convex contact surface (6) is formed by a conveyor belt (8) located inside the deflection section (3). [3] Digital printing machine according to claim 2, characterized by , that the external conveyor belt (7) is guided through a concave belt guide (9) which is heated. [4] Digital printing machine according to claim 3, characterized by , that the concave belt guide (9) is heated by heating fluid (10). [5] Digital printing machine according to claim 2, characterized by , that the internal conveyor belt (8) is guided through a convex belt guide (11) which is heated. [6] Digital printing machine according to claim 5, characterized by , that the convex belt guide (11) is heated by heating fluid (10). [7] Digital printing machine according to claim 2, characterized by, that the external conveyor belt (7) is guided by a concave belt guide (9) which is designed as a flexible plate that is curved. [8] Digital printing machine according to claim 7, characterized by , that the flexible plate is pressed against the external conveyor belt (7) by a spring (12), and that the flexible plate is held under tension by the spring (12). [9] Digital printing machine according to claim 2, characterized by , that the outer conveyor belt (7) is driven in a circulating manner faster than the inner conveyor belt (8), so that the concave contact surface (5) has a higher surface velocity than the convex contact surface (6). [10] Digital printing machine according to any one of claims 1 to 9, characterized by , that within an arc transport path the deflection section (3) is arranged between a first arc transport belt (13) and a second arc transport belt (14).

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