SHEET-FED PRINTING PRESS HAVING A DRYER FOR DRYING SHEETS PRINTED BY A NON-IMPACT PRINTING DEVICE

Abstract

In some examples, a sheet-fed printing press includes a dryer for drying sheets printed by a non-impact printing device. A cooling unit is directly downstream from the dryer in the transport direction, and includes a cooling module above a conveying plane. The cooling module uses air as a cooling medium, and may include a blower module with blower nozzles that blow the cooling medium onto the surface of the sheets being cooled. The blower module forms, with a guide surface, a gap with respect to the surface of the sheet being cooled. The guide surface of the blower module is arranged at a height above the surface of the sheet being cooled so that the cross-section of an outer annular gap, through the cooling medium exits, is smaller than or almost equal to a sum cross-section across all opening surfaces of the blower nozzles in the guide surface.

Claims

1-40. (canceled)

41. A sheet-fed printing press comprising a dryer (17) drying sheets (64) printed by a non-impact printing device (13), the dryer (17) being configured as a hot air dryer and/or as a dryer drying by infrared (IR) radiation, a cooling unit (36) being arranged directly downstream from the dryer (17) in a transport direction (T) of the sheets (64), the cooling unit (36) comprising at least one cooling module (37) above a conveying plane (E) in which the sheets (64) are conveyed through the cooling unit (36) lying flat, and the relevant cooling module (37) being configured so as to use air as the cooling medium, characterized in that each of the cooling modules (37) of the cooling unit (36) is configured in each case as a blower module (41), the respective blower module (41) being configured so as to guide the cooling medium in each case onto the surface of the sheets (64) to be cooled, the respective blower module (41) comprising blower nozzles (43), the cooling medium being blown by these blower nozzles (43) onto the surface of the respective sheet (64) to be cooled, the respective blower module (41) being configured so as to form, with a guide surface (42), a gap (S37) with respect to the surface of the relevant sheet (64) to be cooled, the guide surface (42) of the respective blower module (41) being arranged at such a height above the surface of the relevant sheet (64) to be cooled that the cross-section of an outer annular gap, through which a volume flow of the cooling medium exits the gap (S37), is smaller than or almost equal to a sum cross-section across all opening surfaces of the blower nozzles (43) in the guide surface (42).

42. The sheet-fed printing press according to claim 41, characterized in that the gap (S37) formed with the guide surface (42) with respect to the surface of the relevant sheet (64) to be cooled has a gap width of 8 mm to 35 mm.

43. The sheet-fed printing press according to claim 41, characterized in that a transport device comprising a conveyor belt is provided, this conveyor belt being configured to transport the printed sheets (64) individually lying flat and forming the conveying plane (E) for the sheets (64) to be conveyed lying flat through the cooling unit (36).

44. The sheet-fed printing press according to claim 41, characterized in that the respective blower module (41) is configured in such a way that the cooling medium that is guided onto the surface of the sheets (64) to be cooled passes over the surface of the sheets (64) to be cooled as a pressure flow from the inside to the outside.

45. The sheet-fed printing press according to claim 41, characterized in that the blower nozzles (43) of the relevant blower module (41) are in each case arranged symmetrically with respect to a center line (M) extending in the transport direction (T) of the sheets (64) to be transported through the cooling unit (36) and/or that, in addition to the blower nozzles (43), Venturi nozzles (49) are arranged in the guide surface (42) of the respective blower module (41), the Venturi nozzles (49) ensuring a defined removal of the air that is blown in by the blower nozzles (43) and is being heated up.

46. The sheet-fed printing press according to claim 41, characterized in that the dryer (17) is configured to heat the printed sheets (64) in each case to more than C, and the cooling unit (36) is configured to cool the sheets (64) heated in the dryer (17) to 30° C.

47. The sheet-fed printing press according to claim 43, characterized in that the conveyor belt (18) is configured to transport the printed sheets (64) individually lying flat through the cooling unit (36) on a run running in the transport direction (T) of the sheets (64), the cooling unit (36) being configured so as to cool the return run (44) of the conveyor belt (18) transporting the sheets (64).

48. The sheet-fed printing press according to claim 41, characterized in that the transport device of the cooling unit (36) comprises transport cylinders (38), these transport cylinders (38) being cooled by a cylinder cooling mechanism.

49. The sheet-fed printing press according to claim 41, characterized in that a cooling power of the cooling unit (36) is adjusted by a control unit.

50. The sheet-fed printing press according to claim 49, characterized in that a dryer power of the dryer (17) arranged upstream from the cooling unit (36) is adjusted by the control unit, the control variable of the control carried out by the control unit for adjusting the dryer power of the dryer (17) being a moisture content of the printed sheets (64) to be dried, a control variable for adjusting the dryer power being the amount of hot air that is blown in 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.

51. The sheet-fed printing press according to claim 50, characterized in that the control unit is configured so as to carry out a target/actual value comparison, the relevant actual value being provided by a moisture sensor, detecting the moisture content of the sheets (64), at the control unit, and the target value being fixedly or adjustably predefined at the control unit.

52. The sheet-fed printing press according to claim 41, characterized in that the dryer (17), on its side facing the surface of the respective sheets (64) to be dried, comprises a guide surface (61) that is arranged spaced apart from the surface of these sheets (64) and has a multiplicity of nozzles (62), each of these nozzles (62) in each case having an opening cross-section through which hot air flows or at least can flow.

53. The sheet-fed printing press according to claim 42, characterized in that the hot air flowing onto the surface of the sheets (64) flows out through a gap opening formed between the guide surface (61) and the surface of the sheets (64), the surface area of the gap opening through which the hot air flowing onto the surface of the sheets (64) flows out being smaller than the total surface area of all opening cross-sections of the nozzles (62) directing hot air at the surface of the sheets (64).

54. The sheet-fed printing press according to claim 41, characterized in that the dryer (17) comprises multiple drying modules (54) that are continuously arranged in a row in the transport direction (T) of the sheets (64), at least one infrared radiation source (63) that is directed at the surface of the relevant sheet (64) to be dried being arranged in each case between adjacent drying modules (54).

55. The sheet-fed printing press according to claim 52, characterized in that a gap (S17), in the form of an annular gap, is formed along a drying section, which is formed between the guide surface (61) of the dryer (17) and the conveyor belt (18) of the dryer (17), for sheets (64) to be transported through the dryer (17) and to be dried, this gap (S17) having a gap width between 8 mm and 35 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Exemplary embodiments of the invention are illustrated in the drawings and will be described in greater detail below. The drawings show:

[0027] FIG. 1 a sheet-fed printing press comprising at least one non-impact printing device, a dryer, and a cooling unit;

[0028] FIG. 2 a side view of the cooling unit comprising multiple cooling modules;

[0029] FIG. 3 an enlarged side view of a cooling module of the cooling unit;

[0030] FIG. 4 a top view onto a guide surface of a cooling module of the cooling unit;

[0031] FIG. 5 a drying module of the dryer arranged in the sheet-fed printing press downstream from the non-impact printing device;

[0032] FIG. 6 a drying module of this dryer having introduced channels;

[0033] FIG. 7 different cross-sectional surfaces of infrared radiation sources;

[0034] FIG. 8 various arrangements of the infrared radiation sources;

[0035] FIG. 9 different designs for integrating the infrared radiation sources into the dryer; and

[0036] FIG. 10 a drying module comprising an integrated infrared radiation source.

DETAILED DESCRIPTION

[0037] FIG. 1 shows an example of the aforementioned sheet-fed printing press. Viewed in the transport direction T of the sheets, the sheet-fed printing press first comprises a sheet feeder 01, in which a first pile 02 of sheets is awaiting processing. The sheets are preferably rectangular substrates made of paper, paperboard, or cardboard. The paper, paperboard and cardboard differ in terms of their respective weight referred to as grammage, i.e., the weight of these sheets in grams per square meter. The grammage of paper is between 30 g/m.sup.2 and 150 g/m.sup.2, that of paperboard is between 150 g/m.sup.2 and 600 g/m.sup.2, and that of cardboard is more than 600 g/m.sup.2. However, the sheets can also in each case be embodied as a substrate made of a plastic material and/or as a thin panel made of, e.g., a metallic material. The sheet feeder 01 can also be configured as a magazine feeder comprising multiple first piles 02.

[0038] A feeder head 03, which is also referred to as suction head, consecutively grips each of the stacked sheets from the top and feeds these sheets, e.g., by means of a first rocking gripper 04, and possibly a transfer drum 34 cooperating with the first rocking gripper 04, in a sequence of sheets separated from each other, e.g., to a first coating device 05, wherein this first coating device 05 is configured, e.g., as a primer application device. The first coating device 05 comprises a transport cylinder 06, configured, e.g., as a printing cylinder, and e.g., a printing unit cylinder 07 cooperating with this transport cylinder 06, comprising a forme roller 08, preferably in the form of an anilox roller, that is placed against, or at least can be placed against, this printing unit cylinder 07, wherein at least one squeegee 09 or a chamber doctor blade system 09 extends in the axial direction of the forme roller 08 for optimally metering a coating substance to be applied to the surface of the sheets. The transport cylinder 06 transports the sheets held on its outer cylindrical surface along a curved, in particular circular arc-shaped transport section. The first coating device 05 applies the coating substance, e.g., a primer, on one of the two sides of the sheets either across the entire surface area or only in certain, i.e., in previously defined, locations, i.e., partially. The sheets are then transferred from the transport cylinder 06 of the first coating device 05, e.g., by means of a preferably continuously revolving first gripper system 11, in particular a first chain conveyor, and, e.g., at least one first conveyor belt 12, 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, and more particularly in such a way that the first gripper system 11 turns the sheets in each case over to the first conveyor belt 12 comprising a linear transport section, wherein a 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 configured as a revolving continuous belt. In an advantageous embodiment, a first dryer 14 drying the sheets coated in the first coating device 05 is provided in the region of the first gripper system 11, wherein this dryer 14 is configured, e.g., as a hot air dryer and/or as a dryer drying by IR radiation or by UV radiation.

[0039] The non-impact printing device 13 generally comprises multiple, e.g., four, ink jet printing devices, which can each be controlled independently of one another, wherein each of these ink jet printing devices, for creating a preferably multi-color print image, in each case applies a different printing ink onto the side of the sheets which, e.g., was previously coated in the first coating device 05. The non-impact printing device 13 preferably comprises a second conveyor belt 16 in the sheet-fed printing press described by way of example here, so that the sheets are printed by the ink jet printing device while they rest on this second conveyor belt 16. The second conveyor belt 16 is preferably configured as a revolving continuous belt. A second dryer 17 drying the printed sheets is arranged downstream from the non-impact printing device 13 in the transport direction T of the sheets, wherein this second dryer 17 is likewise configured, e.g., as a hot air dryer and/or as a dryer drying by IR radiation. The second dryer 17 comprises a transport device 18, which transports the sheets lying flat in a translatory manner, i.e., along a linear transport section. This transport device 18 is configured as a third conveyor belt 18 in the sheet-fed printing press shown by way of example in FIG. 1. The third conveyor belt 18 is also preferably configured as a revolving continuous belt. The transport device 18 of the, in this example, second dryer 17 preferably transfers the dried sheets to a suction belt feed table 19, which is generally arranged directly downstream therefrom and from which the sheets are transferred, e.g., by means of a second rocking gripper 21, and possibly a transfer drum 33 cooperating with the second rocking gripper 21, to a second coating device 22. The second coating device 22 is configured, e.g., as a varnishing unit, wherein this second coating device 22 applies a coating substance, e.g., a varnish, in particular to a print image previously created in the non-impact printing device 13. The second coating device 22, in turn, comprises a transport cylinder 23 configured, e.g., as a printing cylinder, serving as the transport device for sheets to be transported, wherein, e.g., a printing unit cylinder 24 including a forme roller 26 that is placed against, or at least can be placed against, this printing unit cylinder 24, preferably in the form of an anilox roller, cooperates with this transport cylinder 23, wherein at least one squeegee 27 or a chamber doctor blade system 27 extends in the axial direction of the forme roller 26. The first conveyor belt 12 and/or the second conveyor belt 16 and/or the third conveyor belt 18 are in each case preferably configured as a revolving flat belt, and moreover preferably as a suction belt, wherein the suction belt has a perforation at least in sections.

[0040] The sheets are then transported from the transport cylinder 23 of the second coating device 22, e.g., by means of a preferably continuously revolving second gripper system 28, in particular a second chain conveyor, to a delivery 29, wherein the sheets processed in this sheet-fed printing press, described by way of example, are preferably deposited by the second gripper system 28 in the delivery 29 in a second pile 32. In an advantageous embodiment, a third dryer 31 drying the sheets coated in the second coating device 22 is provided in the region of the second gripper system 28, wherein this third dryer 31 is configured, e.g., as a hot air dryer and/or as a dryer drying by IR radiation or by UV radiation. The delivery 29 can also be configured as a multi-pile delivery comprising multiple second piles 32.

[0041] The machine system shown by way of example in FIG. 1 is configured as a digital printing press for use in an industrial printing process, in particular for mass-producing printed products. Starting at the sheet feeder 01, individual sheets are sequentially guided through this machine system forming a sheet-fed printing press to the delivery 29 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. In the process, individual sheets that are transported along at least one of the linear transport sections and adjoin one another in their transport direction T, i.e., directly follow one another in the sequence, are in each case spaced apart from each other by a gap. This gap is significantly smaller than a length of the sheets extending in the transport direction T of the sheets and is only a few millimeters, e.g., approximately 20 mm.

[0042] When passing through a dryer 17 drying, e.g., by hot air and/or by IR radiation, sheets lying flat individually on a conveyor belt 18, which were previously printed in a non-impact printing device 13, are subjected to very high heat input, as a result of which these dried sheets deform, i.e., in particular curl up, and thereby at least partially lose their flat position on the conveyor belt 18. Curling-up of the dried sheets can be so extensive that the relevant sheet loses its adhesion to the conveyor belt 18 of the dryer 17 and, when the conveyor belt 18 is configured as a suction belt, can no longer be held by means of suction force exerted at the suction belt. As a result, the relevant sheet is, at a minimum, no longer transported with positional accuracy. It is also possible for curled-up sheets provided at the exit of the dryer 17 to no longer be reliably received by a transport device arranged downstream from the dryer 17 in the transport direction T of the sheets, e.g., by the transport device of a cooling unit 36 or of a suction belt feed table 19, due to inadequate detection, which in the aforementioned machine system comprising multiple transport devices in particular very quickly results in a disruption of the operation 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 detection of the curled-up sheets is, in particular, that the bending resistance forces inherent in the curl of the relevant sheets are not overcome by a height-dependent suction force that is exerted by a suction belt. To avoid that a print image that has previously been applied to the upper side of the relevant sheets in the non-impact printing device 13 becomes damaged, however, forcing the sheets that have curled-up, at the aforementioned locations in the machine system described here, into a flat position, e.g., by means of a mechanical hold-down device, is not an option.

[0043] The sheets that have become heated to a high degree in the dryer 17 as a result of the drying process, however, also heat the devices that ensure their advancement, in particular the conveyor belt 18 of the relevant transport device, and more particularly in some circumstances to such an extent that this conveyor belt 18 expands and consequently loses its tension and, with this, its directional stability.

[0044] Moreover, when the sheets that have been advanced and heated to a high degree in the dryer 17 as a result of the drying process cool down, condensation water precipitates on cooler, e.g., metallic, components, such as transport cylinders 38, of transport devices arranged downstream from the dryer 17. The reason is that there is increased evaporation of water and solvents contained in the applied printing ink in sheets that have been previously printed by the non-impact printing device 13 and dried in the dryer 17. This evaporation then precipitates on cold components, leading to massive condensation water, in some instances, in the machine units arranged downstream from the dryer 17, such as a suction belt feed table 19, a second processing device 22, e.g., configured as a varnishing unit, and/or the delivery 29.

[0045] As a result, the problem arises that, on the one hand, sheets printed by the non-impact printing device 13 must be dried as quickly as possibly by heat input in the dryer 17 and, on the other hand, undesirable effects due to excess thermal energy must be avoided in machine units arranged downstream from the dryer 17.

[0046] For this reason, as is illustrated in FIG. 1, it is provided to arrange a cooling unit 36 directly downstream from the dryer 17 in the transport direction T of the sheets, wherein this cooling unit 36 is either integrated into the stand of the dryer 17 or embodied in a dedicated stand, i.e., a stand separate from the dryer 17, as a self-contained machine unit. The transport device 18 of the dryer 17 configured as a conveyor belt 18 can also continuously extend through the cooling unit. Preferably, however, the cooling unit 36 is arranged in a dedicated stand and has a conveyor belt that is only assigned to the cooling unit 36 and is therefore separate from the dryer 17. At the exit of the cooling unit 36, the sheets that were heated in the dryer 17 to considerably more than 80° C. and have now been cooled, e.g., to 30° C., are preferably received by a suction belt feed table 19.

[0047] As can be derived from FIG. 2, which shows a side view of the cooling unit, the cooling unit 36, above a conveying plane E in which sheets are conveyed lying flat through the cooling unit 36, comprises at least one cooling module 37, preferably multiple cooling modules 37 that are continuously arranged in a row along an e.g., linear transport section. Each cooling module 37 is, e.g., removably inserted into a frame and/or arranged, together with its frame, so as to be foldable in a stand of the relevant cooling unit 36, improving the accessibility of the relevant cooling module 37, e.g., for cleaning and/or maintenance work. In particular when a transport device configured as a continuously revolving conveyor belt forms the conveying plane E for the sheets in the cooling unit 36, i.e., when the conveying plane E is preferably embodied by a conveyor belt 18 extending through the cooling unit 36, the arrangement of the relevant cooling module 37, in which it is removably inserted into a frame and/or arranged in a foldable frame, is very advantageous with respect to maintenance work of the relevant transport device and/or a possibly required removal of sheets. This conveyor belt 18 is either configured as a conveyor belt of the dryer 17 which extends through the cooling unit 36, or as a conveyor belt that is only assigned to the cooling unit 36, wherein the cooling unit 36 in the latter variant embodiment is arranged in a dedicated stand, i.e., a stand separate from the dryer 17.

[0048] The relevant cooling module 37 is preferably configured to use air as the coolant, e.g., ambient air or cooled air. As is shown in particular in FIG. 3, each of the cooling modules 37 of the cooling unit 36 is, e.g., configured in each case as a blower module 41, wherein the respective blower module 41 is configured so as to guide the cooling medium in each case onto the surface of the sheets to be cooled. The respective blower module 41 is configured so as to form, with a guide surface 42, a narrow gap S37 with respect to the surface of the sheets to be cooled, wherein its gap width is, e.g., 8 mm to 35 mm, preferably 20 mm. It is also preferably provided that in each case cooling medium that is guided onto the surface of the sheets to be cooled passes over the surface of the sheets to be cooled as a pressure flow from the inside to the outside. Perforations, e.g., serving as blower nozzles 43 (FIG. 4), are arranged in the guide surface 42 of the respective blower module 41, wherein the cooling medium is blown by these blower nozzles 43 onto the surface of the respective sheet to be cooled. These blower nozzles 43, which in particular are configured as round nozzles, are arranged, e.g., symmetrically with respect to a center line M extending in the transport direction T of the sheets to be transported through the cooling unit 36. In addition to the blower nozzles 43, Venturi nozzles 49, e.g., can be arranged in the guide surface 42 of the respective blower module 41, which ensure a defined removal of the air that is blown in by the blower nozzles 43 and is being heated up.

[0049] The guide surface 42 of the respective blower module 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 the gap S37, is less than or almost equal to the sum cross-section across all opening surfaces of the blower nozzles 43 in the guide surface 42, so that the pressure in the pressure flow is further increased, and the energy exchange with the hot surface of the sheets to be cooled is favored. The annular gap formed between the guide surface 42 of the respective blower module 41 and the surface of the sheets to be cooled thus becomes the actual constriction cross-section for the flow system of the cooling unit 36.

[0050] When the cooling unit 36 comprises a multiple arrangement of cooling modules 37 (FIG. 2), wherein these cooling modules 37 are arranged along the relevant transport section, in each case above the conveying plane E of the sheets to be cooled, joints 39 are formed between adjacent individual cooling modules 37 in such a way that the respective joint 39 for the curled-up leading edge of a sheet to be cooled, which is guided with contact in edge guidance along the respective guide surface 42, provides an, in particular step-shaped, cross-sectional expansion so that the turned-up leading edge of a sheet to be cooled can never become caught in one of the joints 39, halting the operation.

[0051] The cooling unit 36 is preferably configured so as to cool its transport device. In particular, the lower return run 44 of this conveyor belt 18 is actively cooled. For this purpose, as is apparent from FIG. 2, the lower run 44 of the conveyor belt 18 is guided through a flow space 48 that is open in the run inlet 46 and in the run outlet 47, e.g., in the form of a tunnel, so that this flow space 48 encloses the lower run 44 of the conveyor belt 18. A gaseous flow agent flows through this flow space 48, wherein this flow agent preferably flows along both the upper side and the underside of the lower run 44 of the conveyor belt 18. Preferably, cold air is blown through the flow space 48, and this cold air flows as cooling air around the lower run 44 of the conveyor belt 18. In the flow space 48, the flow direction of the flow agent, e.g., of the cooling air, is oriented counter to the running direction of the lower run 44 of the conveyor belt 18. As an alternative or in addition, it may be provided that the transport device of the cooling unit 36 which transports the sheets to be cooled comprises transport cylinders 38, wherein these transport cylinders 38 are actively cooled by a cylinder cooling mechanism using, e.g., water as the cooling medium.

[0052] In a very advantageous embodiment of the cooling unit 36, its cooling power is adjusted by a control unit, wherein the control variable of the control carried out by this control unit for adjusting the cooling power is a temperature of the sheets in the pile 32 of the delivery 29. The control unit carries out a target/actual value comparison, wherein the actual value is provided by a temperature sensor in the delivery 29 at the control unit, and the target value is fixedly or adjustably predefined at the control unit. The control unit then outputs an adjustment increment specification to at least one actuator providing the cooling power of the cooling unit 36, as a function of the target/actual value comparison that was carried out.

[0053] Moreover, it may be provided that a dryer power of the dryer 17 arranged upstream from the cooling unit 36 is adjusted by a control unit, wherein the control variable of the control carried out by the control unit for adjusting the dryer power of the dryer 17 is, e.g., a moisture content of the printed sheets to be dried. The control unit, in turn, carries out a target/actual value comparison, wherein the actual value is provided by a moisture sensor, detecting the moisture content of the sheets, at the control unit, and the target value is fixedly or adjustably predefined at the control unit. The control unit then outputs an adjustment increment specification to at least one actuator providing the dryer power of the dryer 17, as a function of this further target/actual value comparison that was carried out. Since this dryer 17 is configured, e.g., as a hot air dryer and/or as a dryer drying by IR radiation, a control variable for adjusting this dryer power is, e.g., the amount of hot air that is blown in 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. The control unit is preferably configured so as to calculate at least one of the aforementioned control variables and the associated adjustment increments with respect to their respective magnitude and/or their respective direction of action and/or so as to select at least one of the aforementioned control variables and the associated adjustment increments based on an algorithm or a family of characteristics stored in the control unit.

[0054] The above-described cooling unit 36 arranged directly downstream from the dryer 17 is configured so as to reduce the surface temperature of the printed sheets dried in the dryer 17 and reduce a residual moisture that remains in the sheets. As a result, the curl of the sheets is decreased, and the sheets regain a flat position that is much easier to process. The sheets processed in the cooling unit 36 then introduce almost no thermal energy into downstream machine units. This also reduces condensation formed at components in downstream machine units.

[0055] To additionally improve also the efficiency of the dryer 17 arranged upstream from the cooling unit 36, and thereby the efficiency of the entire above-described sheet-fed printing press, measures are described hereafter for shortening the drying time required by the dryer 17 for drying the sheets printed in the sheet-fed printing press, and thereby speeding up production with the sheet-fed printing press or reducing the energy input required for the drying process.

[0056] As is apparent from the representative illustration in FIG. 5, the dryer 17 arranged in a sheet-fed printing press is configured in the form of at least one drying module 54, wherein the relevant drying module 54, on its side facing the surface of the sheet 64 to be dried and moved through the sheet-fed printing press in the transport direction T, comprises a guide surface 61, which extends across, e.g., a linear drying section, and has a multiplicity of nozzles 62, wherein each of these nozzles 62 in each case has an opening cross-section through which the hot air flows or at least can flow. In particular, an edge of a sheet 64 that is curled up from the flat position, i.e., turned-up, can be guided along the drying section through the dryer 17, at the guide surface 61 of the dryer 17. In the sheet-fed printing press printing and/or varnishing sheets 64, which is preferably configured as a digital printing press, the drying section of the dryer 17 is preferably configured to be planar and linear. The sheets 64 are preferably transported lying flat on at least one conveyor belt along the planar conveying section.

[0057] For forming a stream of the hot air flowing out of the nozzles 62, as is indicated in each case by directional arrows in FIGS. 5 and 6, different nozzles 62 having differently shaped opening cross-sections can be employed as needed and/or simultaneously, so as to remove by doctoring the moist air, by way of the pulse of the hot air jet, in the boundary layer directly above the surface of the sheet 64 to be dried, i.e., to remove it to as great an extent as possible, but at least to swirl it and thereby ensure an air exchange at the surface of the sheet 64 to be dried. In this way, the employed nozzles 62, which are arranged in or at the guide surface 61, are configured, e.g., as round nozzles or as slot-shaped nozzles or as Venturi nozzles.

[0058] It is possible, e.g., to use infrared emitters comprising a heating coil arranged in a glass tube or infrared halogen emitters comprising a heating coil arranged in a glass tube filled with halogen, as a radiation source 63 for an infrared radiation emitted by the dryer 17. Panel heaters comprising heating elements arranged in a planar manner are also suitable. A cross-sectional surface of such infrared radiation sources 63 is, e.g., configured in the form of a circle or an oval or as a twin tube or as a square or as a trapezoid, such as the different representations of the cross-sectional surface in FIG. 7 show by way of example. FIG. 8, by way of example, shows different arrangements of the infrared radiation sources 63. For example, the infrared radiation sources 63 can be arranged in the guide surface 61, e.g., transversely or longitudinally or obliquely with respect to the transport direction T of the moved sheet 64 or in the form of tiles.

[0059] FIG. 9, by way of example, shows two different designs for integrating the infrared radiation sources 63 into the relevant drying module 54 of the dryer 17. In the embodiment a) shown only schematically in FIG. 9, at least a portion of the guide surface 61 of the dryer 17 is made of e.g., glass, and is thus transmissive to infrared radiation, so that the infrared radiation emitted by the infrared radiation sources 63, as indicated by directional arrows, can penetrate the guide surface 61 of the dryer 17 in the direction of the sheet 64 to be dried. In the embodiment b) likewise shown only schematically in FIG. 9, at least a portion of the guide surface 61 of the dryer 17 is made of, e.g., a metallic material, e.g., a metal sheet, and thus does not allow infrared radiation to pass through, so that the guide surface 61 of the dryer 17 has apertures through which the infrared radiation emitted by the infrared radiation sources 63, as indicated by directional arrows, can radiate in the direction of the surface of the sheet 64 to be dried. In this second variant embodiment, it is important that the apertures are kept narrow, and the leading edge of the aperture is spaced a larger distance apart from the conveyor belt than the trailing edge of the aperture, so that a curled-up sheet leading edge, moving in edge guidance along the guide surface 61, cannot become caught at the leading edge of the aperture.

[0060] The hot air flowing onto the surface of the moved sheet 64 flows out through a gap opening formed between the guide surface 61 of the dryer 17 and the surface of the sheet 64 to avoid an accumulation of air, wherein this gap opening is configured, e.g., in the form of an annular gap. Additionally, it is also possible, e.g., for multiple channels 55 having a preferably circular cross-section to be introduced in the drying module 54 of the dryer 17 (FIG. 6), through which the moist air in the boundary layer directly above the surface of the sheet 64 to be dried is partially extracted. The channels 55 for partially extracting the moist air in the boundary layer directly above the surface of the sheet 64 to be dried are arranged in the guide surface 61 of the dryer 17, preferably in its edge regions extending parallel to the transport direction T of the moved sheet 64, which also has a positive effect on a guidance of the moved sheet 64 in correct positional arrangement along the drying section of the dryer 17. The drying process, which is caused by the radiant energy emitted by infrared radiation sources 63 primarily heating the surface of the sheet 64, but also causes heating with subsiding effect in its depth, is considerably supported by the described gap opening flow since, on the one hand, a volume flow of hot air that is heated to a considerably greater extent is provided at the surface of the sheet 64 to be dried and, on the other hand, the heat-moisture exchange between the moist surface of the sheet 64 to be dried and the gap flow is favored by the convection, which is expanded by pressure as a physical state variable, and thus by velocity. As a result, the dryer 17 becomes more efficient, while all energy input variables remain the same.

[0061] The dryer 17 preferably comprises multiple drying modules 54 that are continuously arranged in a row along an, e.g., linear transport section. Each of these drying modules 54 is arranged closely, e.g., above the transport device, configured as a continuously revolving conveyor belt, of the dryer 17 that is arranged directly downstream from the non-impact printing device 13 in the transport direction T of the sheets.

[0062] FIG. 10 shows a single one of the drying modules 54 arranged in the dryer 17. Above the guide surface 61, each of the drying modules 54 generally comprises a blower module 51 and an, in particular heat-resistant, fan 52 and an air guide baffle 53, serving as a heater element, wherein the heating element is used to heat the air that is caused to flow by the fan 52. Each sheet 64 to be dried is guided in a gap S17 extending between the guide surface 61 of the dryer 17 and the conveyor belt 18, wherein transport cylinders 59, e.g., supporting the conveyor belt, are arranged beneath the conveyor belt 18. The gap S17, which is in particular embodied as an annular gap, has a gap width between, e.g., 8 mm and 35 mm, preferably between 10 mm and 20 mm. In an embodiment that is not shown, at least one infrared radiation source 63, which is directed at the surface of the sheet 64 to be dried, is arranged in each case in a joint between drying modules 54 that are continuously arranged in a row adjacent to one another in the transport direction T of the sheets 64. On its side that is directed at the surface of the sheet 64 to be dried, the relevant infrared radiation source 63 is in particular covered in each case, e.g., with a protective glass 57, for guiding an edge of the sheet 64 that is curled up from the flat position, i.e., turned up. FIG. 10 shows a preferred embodiment of the drying modules 54, in which the respective infrared radiation source 63 directed in each case at the surface of the sheet 64 to be dried is integrated in a housing 58 of the relevant drying module 54. In a refinement of the previously illustrated drying module 54, an, in particular meander-shaped, beam trap is arranged in the flow path between the fan 52 and the air guide baffle 53, so that the fan 52 and the air guide baffle 53 are thermally decoupled.

[0063] Although the disclosure herein has been described in language specific to examples of structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described in the examples. Rather, the specific features and acts are disclosed merely as example forms of implementing the claims.