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 area 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, corrugated board, plastic, metal or composite material. State of the art

[0003] There are many dryers known for drying with blown air, especially with hot air, e.g. in sheet-processing offset printing presses.

[0004] DE10118757A1 discloses a printing machine with at least one dryer insert for drying substrate with hot air. In the inserted state, the dryer is connected to a blowing device and is supplied with blowing air by it.

[0005] German patent DE 102005010992B4 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. German patent DE 102006030371A1 shows a similar design, in which the nozzle tubes generate different volume flows, e.g., by means of different nozzle diameters.

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

[0007] The as yet unpublished European patent application number 23157023.5-1014 discloses a dryer for drying a substrate exposed to fluid, comprising an arrangement of a plurality of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

[0008] EP1921407A2 discloses a drying system with a heating device comprising an interior space with a radiation opening and a radiant element within the interior space. The device further includes a ventilation arrangement for supplying the interior space with a ventilation gas. The device may have a ceramic plate with cylindrical ventilation nozzles formed as bores in it. The ventilation arrangement is intended to generate a shielding, unidirectional flow from the inside to the outside. This is intended solely to prevent dust from entering the interior space from the outside and clogging the radiant element. The document does not indicate that the ventilation nozzles may have a shape other than a simple cylinder.

[0009] US2014 / 0245950A1 discloses a device for drying surfaces with a plurality of circular nozzles. One of the proposed embodiments uses multiply branched circular nozzles in which the total cross-section does not change in the longitudinal direction of the circular nozzles, i.e., there are no tapered sections, but only branching sections.

[0010] US2014 / 0150285A1 discloses a drying device with nozzles that direct airflow onto the material to be dried, wherein a central nozzle section branches into closed side chambers, while the cross-section of the central nozzle section remains unchanged.

[0011] EP 1 921 407 A2 discloses a generic device according to claim 1 for applying blown air to a substrate, comprising an arrangement of a plurality of round nozzles directed towards the substrate. However, the round nozzles do not have a tapered shape.

[0012] US patent 2014 / 0245950 discloses a device for drying with round nozzles, each of which has several branching tapers.

[0013] US 2014 / 0150285 Al also reveals a device for drying, but without round nozzles.

[0014] Despite all known measures, the problem of drying printed materials can still arise when the existing dryers and their round nozzles deliver the blown air at too low a speed, negatively impacting the drying result. This can occur particularly when – for example, due to sheet grippers – the distance to the printed material must be large. Depending on the specific circumstances, the heat and mass transfer coefficients may then be too low for adequate drying. An obvious, but expensive and therefore not preferred solution would be to install more powerful blowers. Technical task

[0015] 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 blown air, especially hot air, at a sufficiently high speed onto the sheets to be dried. This solution should preferably be easy to implement and cost-effective. Retrofitting existing devices should also be possible. Inventive solution to the problem

[0016] This problem is solved according to the invention by a device according to claim 1.

[0017] Advantageous and therefore preferred embodiments of the invention are evident from the dependent claims as well as from the description and the drawings.

[0018] A device according to the invention for applying blown air to a substrate, e.g. a dryer and in particular a hot air dryer, with an arrangement of a plurality of round nozzles directed towards the substrate, is characterized in that the round nozzles each have a first, a second and a third longitudinal section successively in the direction of flow 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 direction of flow from D1 to D3, that the first longitudinal section has a length L1, the second longitudinal section a length L2 and the third longitudinal section a length L3 and the second longitudinal section causes a taper of the round nozzle of width 2*B, wherein L2 ≥ B and wherein L3 > 2*L1 or L3 > 3*L1 or L3 > 4*L1. Advantageous forms and effects of the invention

[0019] The invention advantageously enables the directing of blown air, particularly hot air, at a sufficiently high speed onto the sheets to be dried. The solution according to the invention is also advantageously easy to implement and incurs only low costs. The invention advantageously allows for energy-saving and thus efficient drying, especially when processing water-based printing fluids. Furthermore, one embodiment of the invention allows for easy retrofitting. The invention is used, for example, in offset printing presses or digital printing presses.

[0020] It is well known that drying is 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 blowing air, and thus the heat transfer coefficient and mass transfer coefficient are best.

[0021] Preliminary experiments revealed the following: The free jet exiting conventional round nozzles is significantly slowed down after exiting; the less turbulent the air in the tube, the less it interacts with the surrounding air. This reduced interaction allows the free jet to strike the substrate at a higher velocity. So-called laminar nozzles (as applied for in the still unpublished European patent application number 23157023.5-1014) were identified as advantageous; these generate a largely laminar air jet.

[0022] As a result of continued and extensive testing and the knowledge gained therefrom, the round nozzles were further redesigned, tested, and ultimately optimized according to the invention. A round nozzle manufactured as a turned part, especially from aluminum, has surprisingly proven to be particularly advantageous. Its production is simpler and more cost-effective than, for example, production by welding two cylindrical parts together or by forming a single part, and is also more precise with regard to the required manufacturing tolerances.

[0023] The heat and mass transfer coefficient can be improved, i.e., increased, by the subdivision according to the invention, 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.

[0024] The invention allows for a low-resistance reduction of the diameter within a (e.g., hot air) round nozzle, thereby reducing the amount of (e.g., hot) air exiting from a (e.g., hot) air chamber connected to the nozzle and preferably pressurized, while simultaneously increasing the air discharge velocity. This ensures that the air impact on the substrate and thus the effectiveness, e.g., for drying dispersion varnish, remains at a high level. The significant advantage of this is that the energy efficiency of the device and, for example, the printing press in which the device is used, can be considerably improved. In the aforementioned tests, the dimensions were also determined.Dimensional ranges for the round nozzles (lengths, diameters, angles) were developed, which are advantageous for the required, energy-saving flow behavior between the nozzle and the substrate to be dried and spaced according to specifications.

[0025] The narrowing in the second longitudinal section occurs without branching, for example, into several parallel nozzle arms. The nozzle therefore has only one inlet and one outlet, and only one path between the inlet and outlet for the blowing air. The nozzle also has no side chambers. Further developments of the invention

[0026] Preferred embodiments of the invention as a device (hereinafter referred to as embodiments) are described below. These can also be combined with one another, unless technically precluded.

[0027] A further development can be characterized by a continuous decrease in the inner diameter D2 along the reduction. Another further development can be characterized by the reduction comprising a slope. A further development can be characterized by the reduction comprising a curve. A further development can be characterized by the presence of multiple reductions, preferably sequentially (with or without a gap between them) in the flow direction. Advantageously, the blown air is accelerated in the flow direction at the reduction(s).

[0028] Further training can be characterized by the following for the inner diameters: D1 > 1.2*D3 or D1 > 1.3* D3 or D1 > 1.4*D3 or D1 > 1.5*D3.

[0029] Further training can be characterized by the following: L3 ≥ 3* D3 or L3 ≥ 4* D3 or L3 ≥ 5* D3.

[0030] A further development can be characterized by the fact that the arrangement is a planar arrangement. A further development can be characterized by the fact that the round nozzles are aligned parallel to each other.

[0031] One further development can be characterized by the fact that the round nozzle comprises a tube and that the taper is formed on the tube. The tube may preferably be made of aluminum. Another further development can be characterized by the round nozzle comprising a tube and an insert within the tube, and that the taper is formed on the insert. The insert may preferably be made of stainless steel.

[0032] Further training can be characterized by the fact that the respective cross-section of the round nozzles in the first, second and third longitudinal section forms a circular ring.

[0033] A further development process can be characterized by the fact that the blowing air is temperature-controlled. A preferred further development process can be characterized by the fact that the blowing air is heated. The blowing air flowing out of the round nozzles primarily serves to dry the substrate.

[0034] A further development can be characterized by the arrangement of the round nozzles in rows. Another further development can be characterized by the arrangement of the round nozzles in a two-dimensional field generated from rows. A further development can be characterized by the field being a flat field; if the transport path of the substrate is curved, a correspondingly curved field can also be provided. According to the invention, segmented round nozzles can be arranged closer together in the field than undivided round nozzles. The heat and mass transfer coefficient can thus be further improved, i.e., increased.

[0035] A further training system can be characterized by the fact that the dryer comprises a chamber and that blown air is directed through the chamber to the round nozzles. The chamber can be subdivided, for example into an inlet area and an outlet area for blown air.

[0036] A training course can be characterized by the fact that the fluid is a printing ink, varnish, or ink. A training course can be characterized by the fact that the fluid is solvent-based. A training course can be characterized by the fact that the fluid is water-based. A training course can be characterized by the fact that the blown air is hot air.

[0037] A further training course may be distinguished by the fact that the round nozzles are made of aluminum. It may be stipulated that the round nozzles are manufactured as turned parts.

[0038] 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 combination with one another – further advantageous developments of the invention. Exemplary embodiments of the invention and figures

[0039] The Figures 1 to 4 The figures show preferred embodiments of the invention and its further developments. Corresponding features are identified by the same reference numerals in the figures. For clarity, some reference numerals that are repeated in the figures have been omitted.

[0040] Figure 1 The figure schematically shows a printing press with a device according to the invention with round nozzles, in particular a dryer or dryer insert.

[0041] A 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 substrate is treated with a fluid 2, preferably with a printing ink, varnish, or ink. The printing machine 3 preferably comprises a feeder 3a and a delivery unit 3b for sheets of substrate 1. The printing machine 3 comprises printing units 4 for treating the substrate with fluid 2, preferably at least four printing units 4a to 4d for printing with the four colors CMYK. The printing machine may additionally include one or more coating units. The printing machine 3 is preferably a sheet-fed offset printing machine of conventional design, i.e., the substrate 1 is transported along the printing units 4 by means of grippers 1b on cylinders and in the delivery unit 3b by means of grippers on chains with crossbeams.

[0042] The printing press 3 comprises a device 5, in particular a dryer 5 or a dryer insert 5, with a chamber 6 which is connected to a compressed air supply 7. The device 5 can be designed as a dryer insert connectable to the compressed air supply 7. The chamber 6 can be subdivided in a conventional manner. The compressed air supply provides compressed air 8, preferably hot air, and for this purpose comprises at least one blower. Several round nozzles 10 (compressed air nozzles) are arranged on the chamber 6, through which the compressed air 8 exits – preferably perpendicularly – onto the substrate 1. The round nozzles 10 are spaced 10a away from the substrate 1 to be dried. This spacer must be selected to be at least large enough to prevent a collision between the grippers 1b and the round nozzles 10. The compressed air 8 exits the round nozzles 10 essentially in a flow direction 14.

[0043] Figure 2shows a perspective view of a device according to the invention with round nozzles, in particular a dryer or dryer insert.

[0044] It can be seen that the device 5 has an arrangement 11 of round nozzles 10 for expelling blown air 8 on its underside – the side facing the substrate 1 to be dried. The round nozzles are preferably arranged regularly in several rows 12 or in a single array 13. The round nozzles 10 are designed as tubes 20, which can be attached to a sheet (or several, preferably parallel, sheets) on the underside of the dryer. The tubes can penetrate the sheet.

[0045] Figure 3Figure 1 shows 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 annular 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 opposing outlet 29b for the blowing 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.

[0046] 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 have different lengths L1, L2, and L3, as shown by way of example, with L3 preferably being greater than L1 greater than L2.

[0047] 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 (in section) designed 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).

[0048] Figure 4Figure 1 shows a sectional view of another preferred embodiment of a round nozzle of a device according to the invention. Here, the tapering 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," i.e., through the outlet 29b, into the tube 20 and up to a rim 21 of the insert 12, which is 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.

[0049] Below are some specific details for an example implementation: Nozzle inner diameter: tapering 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 slope 27 between 18 and 22°, preferably approximately 20°; and L2 approximately 5 mm, B approximately 2 mm. Reference symbol list

[0050] 1 Substrate, e.g., paper 1a Transport direction 1b Transport gripper 2 Fluid, e.g., printing ink or ink 3 Printing press 3a Feeder 3b Delivery 4 Printing units 4a-d Printing units 5 Device, in particular dryer 6 Chamber 7 Blown air supply 8 Blown air 9 Sheath flow 10 Round nozzle(s) 10a Spacing 11 Arrangement 12 (One-dimensional) rows 13 (Two-dimensional) field 14 Flow direction 20 Pipe 20a Flange 21 Insert 21a Edge 22 Cross-section, ring 23 First longitudinal section 24 Second longitudinal section 25 Third longitudinal section 26 Tapering 27 Incline 28 Curve 29a Inlet 29b Outlet D1 Inner diameter of first longitudinal section D2 Inner diameter of second longitudinal section D3 Inner diameter of third longitudinal section L1 Length of first longitudinal section L2 Length of second longitudinal section L3 Length of third longitudinal section B Width α Angle

Claims

1. Device for applying blast air to a printing substrate, with an arrangement (11) of a plurality of round nozzles (10) aligned with the printing substrate (1), 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 direction of flow (14) of the blast air (8), the inner diameter D1 of the first longitudinal section (23) being greater than the inner diameter D3 of the third longitudinal section (25), and the inner diameter D2 of the second longitudinal section (24) tapering from D1 to D3 in the direction of flow (14), in 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 and the second longitudinal section (24) causes a tapering of the round nozzle (10) of width 2xB, where L2 ≥ B and where L3 > 2xL1 or L3 > 3xL1 or L3 > 4xL1.

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

3. The device according to one of the preceding claims, characterized in that the taper (26) comprises a slope (27).

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

5. The device according to one of the preceding claims, characterized in that the following applies: D1 > 1.2xD3 or D1 > 1.3x D3 or D1 > 1.4xD3 or D1 > 1.5xD3.

6. The device according to one of the preceding claims, characterized in that the following applies: L3 ≥ 3x D3 or L3 ≥ 4x D3 or L3 ≥ 5x D3.

7. The device according to one of the preceding claims, characterized in that the round nozzle (10) comprises a tube (20) and in that the taper (26) is formed on the tube (20).

8. Device according to any one of the preceding claims 1 to 6, characterized in 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).

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

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