Sheet-fed printing press with a drying dryer for sheets printed by a non-impact printing unit

Abstract

Sheet-fed printing press with a dryer (17) for drying sheets printed by a non-impact printing unit (13), wherein the dryer (17) is designed as a hot air dryer and / or as a dryer drying by IR radiation, wherein a cooling device (36) is immediately arranged downstream of the dryer (17) in the transport direction (T) of the sheets, wherein a delivery unit (29) is arranged at the end of a transport path through the sheet-fed printing press, depositing the sheets in a stack (32), wherein a cooling capacity of the cooling device (36) is set by a control device, wherein the controlled variable of the control carried out by the control device for setting the cooling capacity is a temperature of the sheets in the stack (32) of the delivery unit (29), wherein the control device is designed such that it performs a setpoint / actual value comparison.wherein the actual value is provided to the control device by a temperature sensor in the delivery unit (29) and the setpoint is fixed or adjustable at the control device, characterized in that a drying capacity of the dryer (17) upstream of the cooling device (36) is set by the control device, wherein the controlled variable of the control carried out by the control device for setting the drying capacity of the dryer (17) is a moisture content of the printed dried sheets, wherein the control device is designed such that it performs a further setpoint / actual value comparison, wherein the relevant actual value is provided to the control device by a moisture sensor detecting the moisture content of the sheets and the setpoint is fixed or adjustable at the control device,wherein a control variable for adjusting the dryer capacity is / are the quantity of blown-in hot air and / or the temperature of the blown-in hot air and / or the intensity of the IR radiation and / or the duration of the IR radiation, wherein the control device is configured such that, depending on the further setpoint / actual value comparison performed, it outputs a control step specification to at least one actuator providing the dryer capacity of the dryer (17), and wherein the control device is configured such that it calculates the relevant control variable and the associated control steps with regard to their respective magnitude and / or their respective direction of action and / or selects them on the basis of an algorithm or characteristic curve field stored in the control device.

Description

[0001] The invention relates to a sheet-fed printing machine with a sheet-drying dryer printed by a non-impact printing device according to the preamble of claim 1.

[0002] The machine arrangement described below, forming a sheet-fed printing press for processing sheet-shaped substrates (hereinafter referred to as sheets), comprises several machine units arranged sequentially in the transport direction of the sheets, with at least one of these machine units having a transport device that moves the sheets along a linear transport path. This transport device is preferably designed as at least one conveyor belt on which the sheets are transported individually, one after the other. While resting on the at least one conveyor belt, the individual sheets are held in place by a suction force, i.e., by a holding force caused by a suction flow, in a frictional or force-fit manner. The suction force is typicallyrealized by a vacuum applied to the respective arc, adjusted with reference to the surrounding barometric air pressure by means of a suction device.

[0003] Such a transport device is arranged in the sheet-processing machine assembly, specifically in a dryer that dries the sheets. The dryer is therefore designed, in particular, as a continuous dryer for single-layer sheets. In a preferred embodiment, a cooling unit for conditioning and / or chilling the sheets heated in the dryer follows the dryer. A suction belt table, for example, is arranged downstream of the cooling unit.

[0004] US 2017 / 0 355 201 A1 is a sheet-fed printing machine with the features of the preamble of claim 1.

[0005] DE 10 2016 207 397 A1 discloses a sheet-fed printing machine with a sheet-drying dryer printed by a non-impact printing device.

[0006] The CN 1 10 884 263 A is a removable dryer for a sheet-fed printing press, wherein the dryer capacity of the dryer is set by a control device, wherein the control variable of the control performed by the control device to set the dryer capacity of the dryer is a moisture content of the printed sheets to be dried.

[0007] US 2012 / 0 162 304 A1 states that a dryer is designed to heat printed sheets to 60°C to 80°C and a cooling device is designed to cool the sheets heated in the dryer to 15°C to 30°C.

[0008] DE 39 43 466 A1 is a device for stacking leaf-like substrates with a removable drying unit and cooling device, wherein the drying unit as a whole is pivotably mounted about an axis.

[0009] The invention is based on the objective of creating a sheet-fed printing machine with a dryer for drying sheets printed by a non-impact printing device, whereby a reliable onward transport of the sheets dried in the dryer is ensured.

[0010] The problem is solved according to the invention by the features of claim 1. The dependent claims each describe advantageous embodiments and / or further developments of the solution found.

[0011] The advantages achievable with the invention consist in particular of ensuring reliable onward transport of the sheets dried in the dryer. Further advantages are evident from the following description.

[0012] Exemplary embodiments of the invention are shown in the drawings and are described in more detail below.

[0013] They show: Fig. 1 a sheet-fed printing machine with at least a non-impact printing unit, a dryer and a cooling unit; Fig. 2 a side view of the cooling device with several cooling modules; Fig. 3 an enlarged side view of a cooling module of the cooling device; Fig. 4 A top view of a guide surface of a cooling module of the cooling device.

[0014] Fig. Figure 1 shows an example of the sheet-fed printing press mentioned at the beginning. Viewed in the transport direction T of the sheets, the sheet-fed printing press first has a sheet feeder 01 in which a first stack 02 of sheets is ready for processing. The sheets are preferably rectangular substrates made of paper, cardboard, or corrugated board. Paper, cardboard, and corrugated board differ in their respective basis weight, i.e., the weight in grams per square meter of these sheets. Paper has a basis weight between 30 g / m². 2and 150 g / m² 2 Cardboard has a basis weight between 150 g / m² 2 and 600 g / m² 2 and cardboard with a basis weight of more than 600 g / m² 2 The sheets can also each be a substrate made of a plastic and / or designed as a thin sheet. The sheet feeder 01 can also be designed as a magazine feeder comprising several first stacks 02.

[0015] A sheet separator 03, also referred to as a suction head, grasps each of the stacked sheets successively from above and feeds these sheets, e.g., by means of a first vibrating gripper 04 and optionally a transfer drum 34 cooperating with the first vibrating gripper 04, in a sequence of separated sheets to, e.g., a first coating unit 05, wherein this first coating unit 05 is designed, e.g., as a primer application unit. The first coating unit 05 has a transport cylinder 06, designed, e.g., as a printing cylinder, and, e.g.,A printing cylinder 07, cooperating with this transport cylinder 06, has an application roller 08 attached to or at least adjustable against this printing cylinder 07, preferably in the form of an anilox roller, wherein at least one doctor blade 09 or a chambered doctor blade system 09 extends in the axial direction of the application roller 08 for optimal metering of a coating material to be applied to the surface of the sheets. The transport cylinder 06 transports the sheets held on its outer surface along a curved, in particular arc-shaped, transport path. The first coating device 05 applies the coating material, e.g., a primer, to one of the two sides of the sheets either completely or only at certain, i.e., previously determined, locations. The sheets are then transferred from the transport cylinder 06 of the first coating device 05, e.g.,by means of a preferably continuously circulating first gripper system 11, in particular a first chain conveyor, and e.g. at least one first conveyor belt 12, the sheets are transferred to a non-impact printing device 13, wherein the first gripper system 11 and the first conveyor belt 12 cooperate during the transfer of the sheets to the non-impact printing device 13, such that the first gripper system 11 delivers the sheets to the first conveyor belt 12, which has a linear transport section, and the transfer of the sheets to the non-impact printing device 13 takes place from the first conveyor belt 12. The first conveyor belt 12 is preferably designed as a continuously circulating endless belt. In an advantageous embodiment, a first dryer 14 is provided in the area of ​​the first gripper system 11 for drying the sheets coated in the first coating device 05, wherein this dryer 14 is, for example,is designed as a hot air dryer and / or as a dryer that dries using IR radiation or UV radiation.

[0016] The non-impact printing unit 13 typically comprises several, e.g., four, independently controllable inkjet printing units, each of which applies a different printing color to the side of the sheet previously coated, e.g., in the first coating unit 05, to create a preferably multi-colored printed image. In the sheet-fed printing press described here as an example, the non-impact printing unit 13 preferably has a second conveyor belt 16, so that the sheets are printed by the inkjet printing units while resting on this second conveyor belt 16. The second conveyor belt 16 is preferably designed as a continuous, circulating belt. Downstream of the non-impact printing unit 13, in the transport direction T of the sheets, a second dryer 17 is arranged for drying the printed sheets, this second dryer 17 also being, e.g.,The second dryer 17 is designed as a hot air dryer and / or as a dryer drying by IR radiation. The second dryer 17 has a transport device 18 which transports the sheets translationally in a lying position, i.e. along a linear transport path. This transport device 18 is located in the [unclear text]. Fig. In the sheet-fed printing press shown as an example, a third conveyor belt 18 is configured. This third conveyor belt 18 is also preferably configured as a continuous, circulating belt. The transport device 18 of the second dryer 17 in this example preferably transfers the dried sheets to a suction belt table 19, from which the sheets are transferred, for example, by means of a second vibrating gripper 21 and optionally a transfer drum 33 cooperating with the second vibrating gripper 21, to a second coating device 22. The second coating device 22 is configured, for example, as a coating device, wherein this second coating device 22 applies a coating material, e.g., a varnish, in particular to a printed image previously created in the non-impact printing device 13. The second coating device 22 again has, for example, a transport device for the sheets to be transported.A transport cylinder 23 designed as a printing cylinder, wherein, for example, a printing cylinder 24 interacts with this transport cylinder 23, with an application roller 26 preferably in the form of an anilox roller, which is attached to or at least attachable to this printing cylinder 24, and wherein at least one doctor blade 27 or a chambered doctor blade system 27 extends in the axial direction of the application roller 26. The first transport belt 12 and / or the second transport belt 16 and / or the third transport belt 18 are each preferably designed as a circulating flat belt and, moreover, preferably as a suction belt, wherein the suction belt has a perforation at least in sections.

[0017] The sheets are then transported from the transport cylinder 23 of the second coating unit 22, e.g., by means of a preferably continuously rotating second gripper system 28, in particular a second chain conveyor, to a delivery unit 29, wherein the sheets processed in this exemplary sheet-fed printing press described are placed by the second gripper system 28 in the delivery unit 29, preferably in a second stack 32. In an advantageous embodiment, a third dryer 31 is provided in the area of ​​the second gripper system 28 for drying the sheets coated in the second coating unit 22, wherein this third dryer 31 is designed, e.g., as a hot air dryer and / or as a dryer drying by IR radiation or by UV radiation. The delivery unit 29 can also be designed as a multi-stack delivery unit comprising several second stacks 32. The Fig. The exemplary machine arrangement shown is designed as a digital printing press for use in an industrial printing process, particularly for the mass production of printed materials. This sheet-fed printing press sequentially feeds individual sheets from the sheet feeder 01 to the delivery 29 at a transport speed of several thousand sheets per hour, e.g., between 2,500 and 10,000 sheets per hour. Along at least one of the linear transport paths, adjacent sheets in their transport direction T, i.e., sheets that follow directly one another in the sequence, are separated from each other by a gap. This gap is significantly smaller than the length of the sheets extending in the transport direction T and is only a few millimeters, e.g., approximately 20 mm.

[0018] During a pass through a dryer 17, which is dried, for example, by hot air and / or IR radiation, sheets previously printed in a non-impact printing unit 13 and lying flat on a conveyor belt 18 are subjected to a very high heat input. This causes the dried sheets to deform, i.e., to curl up, and thus lose their flatness on the conveyor belt 18, at least partially. The curling of the dried sheets can reach such an extent that the sheet loses its adhesion to the conveyor belt 18 of the dryer 17 and, if the conveyor belt 18 is designed as a suction belt, can no longer be held in place by the suction force exerted on it. Consequently, the sheet is no longer transported in a oriented position.Furthermore, curled sheets provided at the dryer 17 outlet can no longer be reliably picked up by a transport device downstream of the dryer 17 in the transport direction T of the sheets, e.g., by the transport device of a cooling unit 36 ​​or a suction belt table 19, due to inadequate gripping. In the aforementioned machine arrangement with multiple transport devices, this leads to a malfunction very quickly, especially when such sheets follow one another at a transport speed of several thousand sheets per hour, e.g., at a transport speed in the range between 2,500 and 10,000 sheets per hour. The cause of the inadequate gripping of the curled sheets lies primarily in the fact that the bending resistance forces inherent in the curl of the sheets in question cannot be overcome by a height-dependent suction force exerted by a suction belt.However, to avoid damaging a printed image previously applied to the top side of the sheets in question in the non-impact printing unit 13, it is forbidden to force sheets that are curled at the aforementioned points in the machine arrangement described here into a flat position, e.g. by means of a mechanical hold-down device.

[0019] The sheets, which are heated considerably by the drying process in the dryer 17, also heat up the devices that transport them further, in particular the conveyor belt 18 of the transport device in question, possibly to such an extent that this conveyor belt 18 stretches and thereby loses its tension and consequently its straight running.

[0020] Furthermore, as the sheets, which are significantly heated by the drying process in dryer 17, cool down, condensation forms on cooler components, such as transport rollers 38, in the transport equipment downstream of dryer 17. This is because sheets previously printed by the non-impact printing unit 13 and dried in dryer 17 exhibit increased evaporation of water and solvents contained in the applied printing ink. These vapors then condense on cold components, leading to sometimes substantial condensation in the machine units downstream of dryer 17, such as a suction belt table 19, a second coating unit 22 (e.g., a coating unit), and / or the delivery unit 29.

[0021] Therefore, the problem is, on the one hand, to dry the sheets printed by the non-impact printing device 13 as quickly as possible by means of heat input in the dryer 17, but on the other hand, to avoid undesirable effects due to excess heat energy in the machine units downstream of the dryer 17.

[0022] Therefore, as in the Fig. Figure 1 shows a proposed arrangement of a cooling device 36 directly downstream of the dryer 17 in the transport direction T of the sheets. This cooling device 36 is either integrated into the frame of the dryer 17 or designed as an independent machine unit in its own frame, separate from the dryer 17. The transport device 18 of the dryer 17, designed as a conveyor belt 18, can also extend continuously through the cooling device. Preferably, however, the cooling device 36 is arranged in a separate frame and has a conveyor belt belonging solely to the cooling device 36 and thus separate from the dryer 17. At the outlet of the cooling device 36, the sheets, heated in the dryer 17 to significantly more than 80°C and now cooled, for example, to 30°C, are preferably transferred to a suction belt table 19.

[0023] Again Fig. Figure 2, which shows a side view of the cooling device, states that the cooling device 36 has at least one cooling module 37, preferably several cooling modules 37 arranged in series along, for example, a linear transport path, above a conveying level E in which sheets are conveyed flat through the cooling device 36. Each cooling module 37 is, for example, removable from a frame and / or arranged to be hinged together with its frame, thereby improving accessibility to the respective cooling module 37, for example, for its cleaning and / or maintenance. This is particularly advantageous when a conveying device designed as an endlessly circulating conveyor belt forms the conveying level E for the sheets in the cooling device 36, i.e.,If the conveying level E is preferably formed by a conveyor belt 18 extending through the cooling device 36, then the arrangement of the relevant cooling module 37 in a frame that can be removed and / or in a hinged frame is very advantageous with regard to maintenance of the relevant conveyor device and / or any necessary removal of sheets. This conveyor belt 18 is designed either as a conveyor belt of the dryer 17 that also extends through the cooling device 36, or as a conveyor belt belonging solely to the cooling device 36, with the cooling device 36 in the latter embodiment being arranged in its own frame, i.e., separate from the dryer 17.

[0024] The cooling module 37 in question is preferably designed to use air as a coolant, e.g., ambient air or cooled air. As shown in particular by the Fig. As shown in Figure 3, each of the cooling modules 37 of the cooling device 36 is designed, for example, as a blow box 41, wherein the respective blow box 41 is designed to direct the cooling medium onto the surface of the sheets to be cooled. The respective blow box 41 is designed, in particular, such that it forms a narrow gap S with a gap width of, for example, 8 mm to 35 mm, preferably 20 mm, with a guide surface 42 to the surface of the sheets to be cooled, and / or that the cooling medium directed onto the surface of the sheets to be cooled flows over the surface of the sheets to be cooled as a pressure flow from the inside out. Perforations are arranged, for example, as blow nozzles 43 in the guide surface 42 of the respective blow box 41. Fig. 4), wherein the cooling medium is blown onto the surface of the respective sheet to be cooled through these nozzles 43. These nozzles 43, which are in particular designed as round nozzles, are arranged, for example, symmetrically to a center line M extending in the transport direction T of the sheet to be transported by the cooling device 36. In addition to the nozzles 43, Venturi nozzles 49 are arranged, for example, in the guide surface 42 of the respective blowing box 41, which ensure a defined removal of the heated air blown in by the nozzles 43.

[0025] The guide surface 42 of the respective blow box 41 is arranged at such a height above the surface of the sheets to be cooled that the cross-section of an outer annular gap, through which a volume flow of the coolant exits from the gap S, is smaller than or nearly equal to the sum of the cross-sectional areas of all the openings of the blow nozzles 43 in the guide surface 42. This further increases the pressure in the pressure flow and promotes energy exchange with the hot surface of the sheets to be cooled. The annular gap formed between the guide surface 42 of the respective blow box 41 and the surface of the sheets to be cooled thus becomes the actual throttling cross-section for the flow system of the cooling device 36.

[0026] If the cooling device 36 has a multiple arrangement of cooling modules 37 ( Fig. 2), wherein these cooling modules 37 are arranged along the relevant transport route above the conveying level E of the sheets to be cooled, separating joints 39 between adjacent individual cooling modules 37 are designed such that the respective separating joint 39 offers a particularly step-shaped cross-sectional expansion for the highly arched leading edge of a sheet to be cooled, which is guided in contact with the edge along the respective guide surface 42, so that the raised leading edge of a sheet to be cooled can never catch in one of the separating joints 39, creating a stop.

[0027] The cooling device 36 is preferably designed to cool its transport device. In particular, the lower return section 44 of this conveyor belt 18 is actively cooled. For this purpose, as shown in the Fig.As can be seen in Figure 2, the lower section 44 of the conveyor belt 18 is guided through a flow chamber 48, open at the section inlet 46 and the section outlet 47, e.g., in the form of a tunnel, so that this flow chamber 48 encloses the lower section 44 of the conveyor belt 18. A gaseous fluid flows through this flow chamber 48, preferably flowing along both the top and bottom of the lower section 44 of the conveyor belt 18. Preferably, the flow chamber 48 is blown with cold air, and this cold air flows around the lower section 44 of the conveyor belt 18 as cooling air. In the flow chamber 48, the flow direction of the fluid, e.g., the cooling air, is opposite to the direction of travel of the lower section 44 of the conveyor belt 18.Alternatively or additionally, it can be provided that the transport device of the cooling device 36, which transports the sheets to be cooled, has transport rollers 38, wherein these transport rollers 38 are actively cooled by a roller cooling system using, for example, water as a cooling medium.

[0028] In a particularly advantageous embodiment of the cooling device 36, its cooling capacity is set by a control device, wherein the controlled variable of the control performed by this control device for setting the cooling capacity is the temperature of the sheets in the stack 32 of the delivery unit 29. The control device performs a setpoint / actual value comparison, whereby the actual value is provided to the control device by a temperature sensor in the delivery unit 29, and the setpoint is fixed or adjustable at the control device. Depending on the setpoint / actual value comparison performed, the control device then outputs a control step value to at least one actuator providing the cooling capacity of the cooling device 36.

[0029] Furthermore, it can be provided that the drying capacity of the dryer 17, which is located upstream of the cooling unit 36, is set by the control unit, wherein the controlled variable of the control performed by this control unit to adjust the drying capacity of the dryer 17 is, for example, the moisture content of the printed, dried sheets. The control unit, in turn, performs a setpoint / actual value comparison, whereby the actual value is provided by a moisture sensor on the control unit that detects the moisture content of the sheets, and the setpoint is fixed or adjustable on the control unit. Depending on this further setpoint / actual value comparison, the control unit then outputs a control step value to at least one actuator that provides the drying capacity of the dryer 17. Since this dryer 17 is designed, for example, as a hot air dryer and / or as a dryer that dries by IR radiation, it is necessary to...These are control variables for adjusting this dryer performance, e.g., the amount of hot air blown in and / or the temperature of the hot air blown in and / or the intensity and / or the duration of the IR radiation. The control device is preferably designed such that it calculates at least one of the aforementioned control variables and the associated control steps with regard to their respective magnitude and / or direction of action and / or selects them based on an algorithm or characteristic curve array stored in the control device.

[0030] The proposed cooling device 36, located directly downstream of the dryer 17, is designed to reduce the surface temperature of the printed sheets dried in the dryer 17 and to reduce any residual moisture remaining in the sheets. This straightens the sheets and improves their flatness, making them easier to process further. The sheets processed in the cooling device 36 then transfer very little heat energy to downstream machine units. This also reduces condensation on components in downstream machine units. Reference symbol list 01 Bow feeder 02 first stack 03 Sheet separator 04 first swing gripper 05 first coating facility 06 Transport cylinders 07 Printing cylinder 08 Application roller 09 Doctor blade; chamber doctor blade system 10 - 11 first gripper system 12 conveyor belt 13 Non-Impact Printing Device 14 first dryer 15 - 16 conveyor belt 17 second dryer 18. Transport equipment; conveyor belt 19 Suction belt table 20 - 21 second swing gripper 22 second coating unit 23 transport cylinders 24 printing cylinders 25 - 26 Application roller 27 doctor blades; chamber doctor blade system 28 second gripper system 29 Display 30 - 31 third dryer 32 second stack 33 Transfer drum 34 Transfer drum 35 - 36 Cooling unit 37 Cooling module 38 Transport roller 39 Separation joint 40 - 41 blowboxes 42 Guide surface 43 Blower nozzle 44 lower tower 45 - 46 Tower inlet 47 Tower outlet 48 Flow chamber 49 Venturi nozzle E funding level M Center line S gap T Transport direction

Claims

Sheet-fed printing press with a dryer (17) for drying sheets printed by a non-impact printing unit (13), wherein the dryer (17) is designed as a hot air dryer and / or as a dryer drying by IR radiation, wherein a cooling device (36) is immediately arranged downstream of the dryer (17) in the transport direction (T) of the sheets, wherein a delivery unit (29) is arranged at the end of a transport path through the sheet-fed printing press, depositing the sheets in a stack (32), wherein a cooling capacity of the cooling device (36) is set by a control device, wherein the controlled variable of the control carried out by the control device for setting the cooling capacity is a temperature of the sheets in the stack (32) of the delivery unit (29), wherein the control device is designed such that it performs a setpoint / actual value comparison.wherein the actual value is provided to the control device by a temperature sensor in the delivery unit (29) and the setpoint is fixed or adjustable at the control device, characterized in that a drying capacity of the dryer (17) upstream of the cooling device (36) is set by the control device, wherein the controlled variable of the control carried out by the control device for setting the drying capacity of the dryer (17) is a moisture content of the printed dried sheets, wherein the control device is designed such that it performs a further setpoint / actual value comparison, wherein the relevant actual value is provided to the control device by a moisture sensor detecting the moisture content of the sheets and the setpoint is fixed or adjustable at the control device,wherein a control variable for adjusting the dryer capacity is / are the quantity of blown-in hot air and / or the temperature of the blown-in hot air and / or the intensity of the IR radiation and / or the duration of the IR radiation, wherein the control device is configured such that, depending on the further setpoint / actual value comparison performed, it outputs a control step specification to at least one actuator providing the dryer capacity of the dryer (17), and wherein the control device is configured such that it calculates the relevant control variable and the associated control steps with regard to their respective magnitude and / or their respective direction of action and / or selects them on the basis of an algorithm or characteristic curve field stored in the control device. Sheet-fed printing press according to claim 1, characterized in that the control device is designed such that, depending on the target / actual value comparison performed, it outputs a setting step specification to at least one actuator providing the cooling capacity of the cooling device (36). Sheet-fed printing machine according to claim 1 or 2, characterized in that the dryer (17) heats the printed sheets to more than 80°C and the cooling device (36) is designed to cool the sheets heated in the dryer (17) down to 30°C. Sheet-fed printing machine according to claim 1 or 2 or 3, characterized in that the cooling device (36) is either integrated into a frame of the dryer (17) or is designed in a separate frame as an independent machine unit.

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