Device for applying blowing air to a printed material

Abstract

A device according to the invention for applying blown air to a printing substrate, e.g. a dryer and in particular a hot-air dryer, having an arrangement (11) of a plurality of round nozzles (10) directed onto the printing substrate (1), is characterized in that the round nozzles (10) each have a first, a second and a third longitudinal section (23, 24, 25) following one another in the flow direction (14) of the blown air (8), wherein the inner diameter D1 of the first longitudinal section (23) is greater than the inner diameter D3 of the third longitudinal section (25) and wherein the inner diameter D2 of the second longitudinal section (24) tapers from D1 to D3 in the flow direction (14). The invention advantageously makes it possible to direct blown air, in particular hot air, at a sufficiently high speed onto the sheets to be dried. The invention is used, for example, in offset printing or digital printing machines.

Description

invention

[0001] The invention relates to a device for applying blown air to a printing material having the features of the preamble of claim 1. field of technology

[0002] The invention lies in the technical field of the graphic industry and there in particular in the field of hot air drying of - preferably water-based - printing fluids such as paint, varnish, primer and / or liquid ink on sheet, web, film or label-shaped printing materials, preferably made of paper, cardboard, paperboard, plastic, metal or composite material. State of the art

[0003] There are many different dryers available for drying with blown air, especially with hot air, e.g. in sheet-fed offset printing machines.

[0004] DE10118757A1 discloses a printing press with at least one dryer insert for drying printing substrates with hot air. When inserted, the dryer is connected to a blower device and is supplied with blower air by this device.

[0005] DE102005010992B4 discloses a sheet-fed printing press with a hot-air dryer having a plurality of air nozzles arranged on a nozzle plate. The nozzles are supplied with air via a chamber. The air nozzles are designed as nozzle tubes or round nozzles. DE102006030371A1 shows something similar, with the nozzle tubes generating different volume flows, e.g., using different nozzle diameters.

[0006] US4854052 discloses a dryer with a nozzle which tapers towards the nozzle outlet opening.

[0007] The as yet unpublished European patent application number 23157023.5-1014 discloses a dryer for drying a printing substrate impinged with fluid, comprising an arrangement of a plurality of parallel aligned round nozzles and a blown air supply, wherein each round nozzle has a tube from which heated blown air flows out onto the printing substrate, wherein the tube is divided internally by means of at least one partition wall into at least two concentric regions, and wherein at least one of the regions is connected to the blown air supply.

[0008] When drying substrates, despite all known measures, the problem can still arise that the existing dryers, including their round nozzles, impinge the air onto the substrate at too low a speed, resulting in a deterioration of the drying result. This can occur particularly when the distance to the substrate must be large—for example, due to the presence of sheet grippers. Depending on the configuration, the heat and mass transfer coefficient may then be too low for sufficient drying. An obvious, but expensive and therefore not preferred, solution could be to install more powerful fans. Technical task

[0009] It is therefore an object of the present invention to provide an improvement over the prior art, which in particular makes it possible to direct blast air, especially hot air, at a sufficiently high speed onto the sheets to be dried. This solution should preferably be simple to implement and inexpensive. It should also be possible to easily retrofit already installed devices. Inventive solution to the problem

[0010] This object is achieved according to the invention by a device according to claim 1.

[0011] Advantageous and therefore preferred developments of the invention emerge from the subclaims as well as from the description and the drawings.

[0012] A device according to the invention for applying blown air to a printing material, for example a dryer and in particular a hot air dryer, with an arrangement of a plurality of round nozzles aligned with the printing material, is characterized in that the round nozzles each have a first, a second and a third longitudinal section in succession in the flow direction of the blown air, wherein the inner diameter D1 of the first longitudinal section is larger than the inner diameter D3 of the third longitudinal section and wherein the inner diameter D2 of the second longitudinal section tapers in the flow direction from D1 to D3. Advantageous embodiments and effects of the invention

[0013] The invention advantageously enables blast air, particularly hot air, to be directed at the sheets to be dried at a sufficiently high speed. The solution according to the invention is also advantageously simple to implement and involves only low costs. The invention advantageously enables energy-saving and thus efficient drying, particularly when processing water-based printing fluids. Furthermore, one of its developments allows for easy retrofitting. The invention is used, for example, in offset printing presses or digital printing presses.

[0014] Drying is known to be best when the air hits the substrate (the printing material) with high impact, because in this case the laminar boundary layer forming on the substrate surface is best "pierced" by the blown air and thus the heat transfer coefficient and mass transfer coefficient are best.

[0015] Tests prior to the invention showed the following: The free jet emerging from conventional round nozzles is significantly slowed down after its exit; the less turbulent the air in the tube is, the less it interacts with the ambient air. Reduced interaction allows the free jet to hit the printing substrate at a higher speed. So-called laminar nozzles (as filed in the as yet unpublished European patent application number 23157023.5-1014) were recognized as advantageous; these produce a largely laminar air jet. As a result of continued experiments and the knowledge gained thereby, the round nozzles were further redesigned, tested, and ultimately optimized according to the invention.

[0016] The heat and mass transfer coefficients can be improved, i.e., increased, by the inventive subdivision, thereby achieving advantageous energy savings. The interaction of the free jet with the ambient air is thus advantageously reduced. Disruptive turbulence can be prevented. A sufficiently high velocity can be generated and maintained in the central region of the free jet.

[0017] The invention allows for a low-resistance taper of the diameter within a (e.g., hot-air) round nozzle, thereby reducing the escaping (e.g., hot) air volume (and thus the energy required to generate the hot air) from a (e.g., hot) air chamber connected to the nozzle and preferably pressurized, while simultaneously increasing the air discharge speed, so that the air impact on the printing substrate and thus the effectiveness, e.g., for drying dispersion varnish, is maintained at a high level. This results in the major advantage of significantly improving the energy efficiency of the device and, for example, the printing press in which the device is used. Further developments of the invention

[0018] Preferred developments of the invention as a device (hereinafter referred to as "developments") are described below. These can also be combined with one another where this is not technically impossible.

[0019] A further development can be characterized by the inner diameter D2 decreasing continuously along the taper. A further development can be characterized by the taper comprising a bevel. Another development can be characterized by the taper comprising a curve. A further development can be characterized by the presence of several tapers, preferably one after the other (with or without spacing between them) in the direction of flow. At the taper(s), the blast air is advantageously accelerated in the direction of flow.

[0020] A further development can be characterized by the fact that the following applies to the inner diameter: D1 > 1.2*D3 or D1 > 1.3* D3 or D1 > 1.4*D3 or D1 > 1.5*D3.

[0021] A further development can be characterized in that the first longitudinal section has a length L1, the second longitudinal section has a length L2 and the third longitudinal section has a length L3.

[0022] A further development can be characterized in that the second longitudinal section results in a tapered round nozzle with a width of 2*B. A further development can be characterized in that the following applies: L2 ≥ B.

[0023] Further training can be characterized by the following: L3 ≥ 3* D3 or L3 ≥ 4* D3 or L3 ≥ 5* D3. Further training can be characterized by the following: L3 > 2*L1 or L3 > 3*L1 or L3 > 4*L1.

[0024] A further development can be characterized by a planar arrangement. A further development can be characterized by the circular nozzles being aligned parallel to one another.

[0025] One development may be characterized in that the round nozzle comprises a tube, and the taper is formed on the tube. Another development may be characterized in that the round nozzle comprises a tube and an insert in the tube, and the taper is formed on the insert.

[0026] A further development can be characterized in that the respective cross-section of the round nozzles in the first, second and third longitudinal sections forms a circular ring.

[0027] One development may be characterized by the fact that the blowing air is tempered. A preferred development may be characterized by the fact that the blowing air is heated.

[0028] A further development can be characterized by the round nozzles being arranged in rows. A further development can be characterized by the round nozzles being arranged in a two-dimensional array created from rows. A further development can be characterized by the array being a flat array; in the case of a curved transport path of the printing substrate, a correspondingly curved array can also be provided. Divided round nozzles according to the invention can be arranged closer together in the array than non-divided round nozzles. The heat and mass transfer coefficient can be further improved, i.e., increased, in this way.

[0029] A further development can be characterized by the dryer comprising a chamber, and by the blown air being guided through the chamber to the round nozzles. The chamber can be divided, for example, into an inlet and an outlet area for blown air.

[0030] A further development can be characterized by the fluid being a printing ink, a varnish, or an ink. A further development can be characterized by the fluid being solvent-based. A further development can be characterized by the fluid being water-based. A further development can be characterized by the blowing air being hot air.

[0031] The features and combinations of features disclosed in the above sections Technical Field, Invention and Further Developments as well as in the following section Exemplary Embodiments represent - in any desired combination with one another - further advantageous developments of the invention. Embodiments of the invention and figures

[0032] The Figures 1 to 4show preferred embodiments of the invention and its further developments. Corresponding features are provided with the same reference numerals in the figures. Recurring reference numerals have been partially omitted for clarity.

[0033] Figure 1 shows schematically a printing machine with a device according to the invention with round nozzles, in particular a dryer or dryer insert.

[0034] A printing substrate 1, preferably a sheet of paper, cardboard or film, is transported in a transport direction 1a. Transport grippers 1b are used for this purpose. During transport, the printing substrate is exposed to a fluid 2, preferably a printing ink, a varnish or an ink. The printing press 3 preferably comprises a feeder 3a and a delivery 3b for sheets of printing substrate 1. The printing press 3 comprises printing units 4 for applying fluid 2, preferably at least four printing units 4a to 4d for printing with the four colors CMYK. The printing press can additionally comprise one or more varnish units. The printing press 3 is preferably a sheet-fed offset printing press of conventional design, ie the printing substrate 1 is transported along the printing units 4 by means of grippers 1b on cylinders and in the delivery 3b by means of grippers on chains with cross members.

[0035] The printing press 3 comprises a device 5, in particular a dryer 5 or a dryer insert 5, with a chamber 6 connected to a blown air supply 7. The device 5 can be designed as a dryer insert connectable to the blown air supply 7. The chamber 6 can be subdivided in a conventional manner. The blown air supply provides blown air 8, preferably hot air, and for this purpose comprises at least one fan. Several round nozzles 10 (blown air nozzles) are arranged on the chamber 6, through which the blown air 8 exits onto the printing substrate 1, preferably vertically. The round nozzles 10 are spaced at a distance 10a from the printing substrate 1 to be dried. This distance must be selected to be at least large enough to prevent a collision of the grippers 1b with the round nozzles 10. The blown air 8 exits the round nozzles 10 essentially in a flow direction 14.

[0036] Figure 2shows a perspective view of a device according to the invention with round nozzles, in particular a dryer or dryer insert.

[0037] It can be seen that the device 5 has, on its underside facing the printing substrate 1 to be dried, an array 11 of round nozzles 10 for expelling blast air 8. The round nozzles are preferably arranged regularly in several rows 12 or collectively in an array 13. The round nozzles 10 are designed as tubes 20, which can be attached to a metal sheet (or several, preferably parallel, metal sheets) on the underside of the dryer. The tubes can penetrate the metal sheet.

[0038] Figure 3shows a sectional view of a preferred embodiment of a round nozzle of a device according to the invention. The round nozzle 10 comprises a tube 20 with a preferably circular cross-section 22 (shown next to the tube); its inner diameter is variable, i.e., decreasing, in the flow direction 14 at least in one longitudinal section. The tube 20 is preferably made of metal. The round nozzle 10 has an inlet 29a and an opposite outlet 29b for the blown air 8. In the region of the inlet 29a, a flange 20a is formed on the tube 20, which serves to mount the tube 20 to a wall of the chamber 6.

[0039] Between inlet 29a and outlet 29b, the round nozzle 10 comprises, in the flow direction 14, a first longitudinal section 23, a following second longitudinal section 24 and a further following third longitudinal section 25. The longitudinal sections can - as shown by way of example - have different lengths L1, L2 and L3, wherein preferably: L3>L1>L2.

[0040] The second longitudinal section is designed as a taper 26, i.e., the inner diameter decreases by 2*B in the region of the second longitudinal section 24. The inner wall in the region of the second longitudinal section 24 is designed (in section) as a slope 27; alternatively, instead of the slope 27 (shown again next to the tube), a curve 28 can also be implemented. The longitudinal sections can have inner diameters D1, D2, and D3, as shown by way of example, where: D3 <D2<D1 (mit veränderlichem D2).

[0041] Figure 4shows a sectional view of another preferred embodiment of a round nozzle of a device according to the invention. Here, the taper 26 is not formed on the tube 20, but on an insert 21 in the tube 20. The insert 21 can be inserted "from below", ie through the outlet 29b, into the tube 20 and up to an edge 21 of the insert 12 designed as a stop. The insert 21 can be made of metal and can be welded into the tube 20. The tube 20 together with the inserted insert 21 has the longitudinal sections L1, L2 and L3 and the inner diameters D1, D2 and D3 (comparable to the embodiment of the Figure 3 ) on.

[0042] Below are some concrete details for an example implementation: Nozzle inner diameter: tapered from approximately 16 to approximately 12 mm; nozzle spacing suitable for a working distance of approximately 80 mm (according to the VDI Heat Atlas); the length of the tapered side of the nozzle on the air outlet side (L3) is 3 to 5 times its diameter D3, so that the air flows out as laminarly and thus "far-reaching" as possible; pressure in chamber 6 between 1 and 50 mbar, preferably between 5 and 15 mbar; angle α of the bevel 27 between 18 and 22°, preferably approximately 20°; and L2 approximately 5 mm, B approximately 2 mm. List of reference symbols

[0043] 1Printing material, e.g. paper 1aTransport direction 1bTransport gripper 2Fluid, e.g. printing ink or ink 3Printing press 3aFeeder 3bDelivery 4Printing units 4a-dPrinting units 5Device, in particular dryer 6Chamber 7Blowing air supply 8Blowing air 9Sheath flow 10Round nozzle(s) 10aSpacing 11Arrangement 12(One-dimensional)Rows 13(Two-dimensional) Field 14Flow direction 20Tube 20aFlange 21Insert 21aEdge 22Cross-section, circular ring 23First longitudinal section 24Second longitudinal section 25Third longitudinal section 26Taper 27Bevel 28Curve 29aInlet 29bOutlet D1Inner diameter of first longitudinal section D2Inner diameter of second longitudinal section D3Inner diameter of third longitudinal section L1Length of first longitudinal section L2Length of second longitudinal section L3Length of third longitudinal section BWidth αAngle

Claims

1. Device for applying blown air to a printing material, with an arrangement (11) of a plurality of round nozzles (10) aligned with the printing material (1), characterized by that the round nozzles (10) each have a first, a second and a third longitudinal section (23, 24, 25) following one another in the flow direction (14) of the blown air (8), wherein the inner diameter D1 of the first longitudinal section (23) is greater than the inner diameter D3 of the third longitudinal section (25) and wherein the inner diameter D2 of the second longitudinal section (24) tapers from D1 to D3 in the flow direction (14).

2. Device according to claim 1, characterized by that the inner diameter D2 decreases continuously along the taper (26).

3. Device according to one of the preceding claims, characterized by that the taper (26) comprises a bevel (27).

4. Device according to one of the preceding claims, characterized by that the taper (26) comprises a curve (28).

5. Device according to one of the preceding claims, characterized by that applies: D1 > 1.2*D3 or D1 > 1.3* D3 or D1 > 1.4*D3 or D1 > 1.5*D3.

6. Device according to one of the preceding claims, characterized by that the first longitudinal section (23) has a length L1, the second longitudinal section (24) has a length L2 and the third longitudinal section (25) has a length L3.

7. Device according to one of the preceding claims 1, characterized by that the second longitudinal section (24) causes a tapering of the round nozzle (10) of width 2*B.

8. Device according to claim 7, characterized by that L2 ≥ B.

9. Device according to one of the preceding claims 6 to 8, characterized by that applies: L3 ≥ 3* D3 or L3 ≥ 4* D3 or L3 ≥ 5* D3.

10. Device according to one of the preceding claims 6 to 9, characterized by that applies: L3 > 2*L1 or L3 > 3*L1 or L3 > 4*L1.

11. Device according to one of the preceding claims, characterized by that the round nozzle (10) comprises a tube (20) and that the taper (26) is formed on the tube (20).

12. Device according to one of the preceding claims 1 to 10, characterized by that the round nozzle (10) comprises a tube (20) and an insert (21) in the tube (10) and that the taper (26) is formed on the insert (21).

13. Device according to one of the preceding claims, characterized by that the respective cross-section (22) of the round nozzles (10) in the first, second and third longitudinal sections (23, 24, 25) forms a circular ring (22).

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