Machine arrangement with several processing stations, each processing a sheet

Abstract

Machine arrangement with several processing stations, each processing sheets, wherein these processing stations are arranged one behind the other in the transport direction (T) of the sheets, wherein at least one of these processing stations has a transport device (18) for transporting the sheets lying down along a linear transport path, wherein this transport device (18) is designed to transport individual sheets in a sequence immediately following one another, spaced apart from each other by a gap, wherein a suction belt table (19) is arranged downstream of this transport device (18) for transporting the sheets lying down along a linear transport path, characterized in that the transport device (18) arranged upstream of the suction belt table (19), which transports the sheets lying down along a linear transport path,The suction belt table (19) is designed to transport individual sheets in a sequence, each with a sheet gap measuring approximately 20 mm, wherein the suction belt table has a catching device (58) with a catching position assumed as a result of actuation for individual sheets in a sequence, wherein the catching device (58) in its catching position catches and stacks sheets supplied to the suction belt table (19) by the transport device (18), which transports the sheets lying down along a linear transport path and is located upstream of the suction belt table (19), before each transfer to a transport device downstream of the suction belt table (19), wherein a control unit (71) is provided, wherein this control unit (71) actuates the catching device (58) depending on a fault that has occurred in a processing station downstream of the suction belt table (19),that the catching device (58) assumes its catching position, wherein in the catching position at least one stop surface (66) of the catching device (58) is arranged to penetrate the arch gap.

Description

[0001] The invention relates to a machine arrangement with several processing stations, each processing a sheet, according to the preamble of claim 1.

[0002] The suction belt table described below is a machine unit for use in a machine arrangement for processing sheet-shaped substrates (referred to as sheets for short), wherein such a machine arrangement comprises several machine units arranged one after the other in the transport direction of the sheets. At least two of these machine units each have transport devices for transporting the sheets. A suction belt table serves to transport processed or to-be-processed sheets along a linear transport path in the machine arrangement, with these sheets being transported individually resting on at least one conveyor belt. 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 typicallyThis is achieved by applying a vacuum to the respective arc, adjusted with reference to the surrounding barometric air pressure by means of a suction device.

[0003] In a preferred application, the suction belt table is arranged in a sheet-processing machine arrangement in the transport direction of the sheets, downstream of a dryer that dries the sheets. In a further embodiment, a cooling section for air-conditioning and / or conditioning the sheets heated in the dryer follows the dryer, so that the suction belt table is only arranged downstream of the cooling section.

[0004] A machine arrangement of the aforementioned type, whether with or without a cooling section after the dryer, typically comprises several processing stations arranged one behind the other in the transport direction of the sheets, each acting on the sheets. Each of these processing stations is designed, for example, as a machine unit within this sheet-processing machine arrangement. As mentioned, the suction belt table can be located directly after the dryer, so that no further processing station is arranged between the dryer and the suction belt table, or it can be located after the cooling section following the dryer. In the machine arrangement considered here as the preferred embodiment, at least the transport device of the dryer upstream of the suction belt table or of the associated cooling section is designed as a transport device that moves the sheets horizontally along a linear transport path.The dryer is therefore specifically designed as a continuous dryer for sheets in single layers.

[0005] A further transport device, located downstream of the suction belt table in the transport direction of the sheets, is designed as a transport device that moves the sheets along a curved, in particular circular arc-shaped, transport path. This further transport device is preferably arranged directly after the suction belt table; that is, no further processing station is arranged between the suction belt table and the downstream transport device in the machine arrangement in question. The sheets to be transported by this machine arrangement thus change from a linear transport path to a curved, in particular circular arc-shaped, transport path after leaving the suction belt table. As will be shown below, a change from a linear transport path to a curved, in particular circular arc-shaped, transport path on a suction belt table is sometimes very problematic.

[0006] DE 10 2016 207 397 A1 discloses a sheet processing machine arrangement with a suction belt table arranged after a dryer for drying the sheets.

[0007] DE 10 2018 201 921 A1 discloses a sheetfed offset printing machine with several processing stations that transport sheets linearly, each of which has a suction belt table.

[0008] DE 101 46 919 C1 discloses a front edge stop as a catching device, wherein this catching device catches and stacks sheets.

[0009] The invention is based on the objective of creating a machine arrangement with several processing stations, each processing sheets, wherein a suction belt table is provided, wherein successive individual sheets can be caught and stacked on the suction belt table before being transferred to a transport device downstream of the suction belt table.

[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 the fact that the catching device allows sheets to be caught and stacked on the suction belt table before they are transferred to a transport device downstream of the suction belt table. Further advantages will become apparent 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 suction belt table in a sheet processing machine arrangement; Fig. 2 a side view of the suction belt table according to Fig. 1; Fig. 3 a top view of the in the Fig. 2 suction belt table shown; Fig. 4 a side view of a catching device integrated into the suction belt table; Fig. 5 the trapping device of the Fig. 4 in their parked position; Fig. 6 the trapping device of the Fig. 4 in their catching position; Fig. 7 an excerpt from the Fig. 2 with the trapping device in its trapping position; Fig. 8 a pneumatic circuit for the operation of the trap; Fig. 9 a diagram of the stroke of the cylinder piston of a pneumatic cylinder driving the catching device; Fig. 10 a diagram of the speed of the cylinder piston during operation of the trapping device; Fig. 11 a diagram of the acceleration of the cylinder piston during operation of the trapping device; Fig. 12 a diagram showing the course of the piston force of the cylinder piston during operation of the catching device; Fig. 13 a schematic representation of a circuit for eliminating a frictional or force-fit connection of sheets held on the suction belt table; Fig. 14 an excerpt from the in the Fig. 3 suction belt table shown in a top view; Fig. 15 a guiding device between two conveyor belts arranged one after the other in the direction of transport of the bows; Fig. 16 a starting situation for the function of the control device; Fig. 17 the control device at the beginning of its activation; Fig. 18 the activated guidance device; Fig. 19 the guiding device during the takeover of a bow; Fig. 20 an excerpt from the in the Fig. 3 top view of the suction belt table with a nozzle arrangement shown; Fig. 21 an excerpt from the in the Fig. 2 Side view of the suction belt table shown.

[0014] An example of the aforementioned machine arrangement is shown in the Fig. Figure 1 illustrates such a machine arrangement. This type of machine arrangement is known, for example, from DE 10 2016 207 397 A1. The sheet-processing machine arrangement chosen as an example has, viewed in the transport direction T of the sheets, 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 and 30 g / m². 2 and 150 g / m² 2 Cardboard has a basis weight between 150 g / m² 2 and 600 g / m² 2and 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 be designed as a thin sheet. The sheet feeder 01 can also be designed as a magazine feeder comprising several first stacks 02.

[0015] A suction head 03 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, e.g., designed as a printing cylinder, and, e.g., a printing cylinder 07 cooperating with this transport cylinder 06, with an application roller 08 attached to, or at least adjustable to, this printing cylinder 07, preferably in the form of an anilox roller, wherein, for optimal metering of a coating material to be applied to the surface of the sheets, at least one doctor blade 09 or a chambered doctor blade system 09 extends in the axial direction of the application roller 08.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 side of the sheets, either completely or only at specific, i.e., predetermined, locations. The sheets are then transferred from the transport cylinder 06 of the first coating device 05, e.g., by means of a first gripper system 11, in particular a first chain conveyor, and e.g.,Sheets are transferred from at least one first conveyor belt 12 to a non-impact printing unit 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 unit 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 sheets are transferred to the non-impact printing unit 13 from the first conveyor belt 12. The first conveyor belt 12 is preferably designed as a continuous, circulating 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 unit 05, wherein this dryer 14 is designed, for example, as a hot air dryer and / or as a dryer that dries by IR radiation or UV radiation.

[0016] The non-impact printing unit 13 typically has at least four independently controllable inkjet printing units, each of which applies a different printing color to the side of the sheet previously coated, for example, in the first coating unit 05, to create a preferably multi-colored printed image. In the machine arrangement 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, for example,The second dryer 17 is designed as a hot air dryer and / or as a dryer drying by IR radiation or by UV 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 exemplary machine arrangement shown in Figure 1, 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 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.transport cylinder 23 designed as a printing cylinder, wherein, for example, a printing cylinder 24 with an application roller 26 attached to or at least attachable to this printing cylinder 24, preferably in the form of an anilox roller, interacts with this transport cylinder 23, wherein at least one doctor blade 27 or a chambered doctor blade system 27 extends in the axial direction of the application roller 26.

[0017] The sheets are then transported from the transport cylinder 23 of the second coating unit 22, e.g., by means of a second gripper system 28, in particular a second chain conveyor, to a delivery point 29, wherein the sheets processed in this exemplary machine arrangement are placed by the second gripper system 28 in the delivery point, 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 that dries by IR radiation or by UV radiation. The delivery point 29 can also be designed as a multi-stack delivery point comprising several second stacks 32. The Fig. 1. The exemplary machine arrangement shown is designed as a digital printing machine for use in an industrial printing process, in particular for the production of printed products in mass production.

[0018] Fig. Figure 2 shows a side view of the suction belt table 19, as it is used, for example, in a machine arrangement according to the Fig. 1 is arranged. The transport direction T of the arcs is in the Fig. 2 from right to left. Thus, 19 individual sheets are sequentially fed to the suction belt table from one side in the Fig. 2. The transport device 18, only partially shown, is fed at a transport speed of several thousand sheets per hour, e.g., approximately 10,000 sheets per hour. In this process, sheets adjacent to each other in their transport direction T, i.e., those following directly one another in the sequence, are spaced apart 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. In the preferred embodiment shown here, the transport device 18, which is arranged upstream of the suction belt table 19 in the transport direction T of the sheets, belongs to a dryer 17, this dryer 17 being configured according to the design shown in the Fig. In the exemplary machine arrangement shown in Figure 1, a second dryer 17 is present, wherein the sheets are transported translationally, i.e., along a linear transport path, by this transport device 18, lying down, in particular on a conveyor belt. The suction belt table 19 initially receives each individual sheet in a conveying plane defined by the transport device 18 upstream of this suction belt table 19 and conceptually extended in the transport direction T of the sheets, wherein this conveying plane is preferably horizontally oriented. In the further course of the transport path of the sheets, the conveying plane E19 ( Fig. 4) The suction belt table 19, with respect to the horizontal conveying plane of the transport device 18 arranged upstream of this suction belt table 19, has a downward inclination at an acute angle in the range between 5° and 30°, preferably in the range between 15° and 25°. At the end of the transport path determined by the suction belt table 19, each sheet strikes with its leading edge in the transport direction T against front marks 36 of the oscillating gripper 21 arranged downstream of the suction belt table 19, wherein this oscillating gripper 21 is in the Fig. Figure 1, an exemplary machine arrangement, shows a second oscillating gripper 21. Each sheet is individually transferred from this oscillating gripper 21 to a transfer drum 33 that interacts with this oscillating gripper 21. The sheets are completely braked at the leading edges and aligned in register.

[0019] In its preferred embodiment, the suction belt table 19 has a scooping device for transporting sheets. Above the conveying plane E19 of the suction belt table 19, the scooping device comprises a box-shaped housing, the so-called blow box 37, which preferably extends over the entire width of the sheets, i.e., transversely to the transport direction T of the sheets. Within the blow box 37, on its side facing the conveying plane E19 of the suction belt table 19 in the transport direction T of the sheets, several blow nozzles are arranged one behind the other. In the preferred embodiment, at least two rows of several blow nozzles, each arranged side by side, are arranged one behind the other in the transport direction T of the sheets and transversely to the transport direction T of the sheets. Each blow nozzle's direction of air is essentially parallel to the conveying plane E19 of the suction belt table 19 and opposite to the transport direction T of the sheets.The respective blowing direction of the blowing nozzles is determined, for example, by at least one guide surface arranged and / or integrally formed on the respective blowing nozzle, which channels the flow of the blowing air. The respective guide surface is designed, for example, as a ramp projecting from the blowing box 37 on the side of the blowing box 37 facing the conveying plane E19 of the suction belt table 19. The blowing air flowing from the respective blowing nozzles is preferably controlled, for example, by adjustable pneumatic valves, e.g., in terms of timing and / or intensity, wherein the valves are controlled, for example, by a preferably digital control unit 71 that executes a program. The valves are switched, for example, by the control unit 71, particularly in a cycle, wherein a cycle duration and / or a cycle frequency is / are preferably set as a function of the feed rate of the sheets supplied to the suction belt table 19.Valves controlled in a cycle by a preferably digital control unit 71 are also called cycle valves.

[0020] In the transport direction T of the sheet, a baffle plate 38 is arranged in an area between the conveying plane E19 of the suction belt table 19 and the side of the blow box 37 facing this conveying plane E19, upstream of the first blow nozzle or the first row of blow nozzles. The baffle plate 38 shields the leading edge of a subsequent sheet, i.e., a sheet that directly follows a sheet lifted by the blowing air from at least one of the blow nozzles of the blow box 37, from the suction effect caused by the blow nozzles arranged in the blow box 37. The sheet lifted from the conveying plane E19 of the suction belt table 19 by at least one of the blow nozzles or rows of blow nozzles of the blow box 37 channels the blowing air flowing from the at least one blow nozzle of the blow box 37 and directs this blowing air over the surface of the baffle plate 38 facing the blow box 37.The baffle plate 38 preferably has a concave curvature at its end located in the direction of airflow, this curvature giving the blown air an outflow direction away from the conveying plane E19 of the suction belt table 19, i.e., directed away from it. The baffle plate 38 prevents the leading edge of a sheet directly following a sheet lifted by the blown air from at least one of the blow nozzles from being affected until the lifted sheet, through its own movement or feed in the transport direction T, exposes the blow nozzle or row of blow nozzles first reached by this sheet in its transport direction T with its rear end. To prevent the leading edge of the sheet directly following a sheet lifted by the blown air from at least one of the blow nozzles from being prematurely exposed due to the effect of the blow nozzle or row of blow nozzles exposed by the rear end of the preceding sheet, the baffle plate 38 provides a concave curvature.When the series of blow nozzles is raised, the blowing air of the respective blow nozzle or blow nozzle series is switched off by means of the respective associated valve depending on the progress of movement or feed of the arc currently being raised from the conveying level E19 of the suction belt table 19, which is directly preceding an arc located between the bulkhead 38 and the conveying level E19 of the suction belt table 19.

[0021] A sheet lifted by the blow nozzles or blow nozzle rows is raised above the conveying level E19 of the suction belt table 19 to a specific floating height, determined, for example, by a distance from the side of the blowing box 37 facing the conveying level E19 of the suction belt table 19, due to the suction effect (Venturi effect) caused by the respective blowing air. This floating height depends on the intensity of the respective blowing air and / or on the mass of the sheet in question and / or on the transport speed of the sheet in question. To prevent sheets of, for example, large mass and / or high transport speed from vibrating and fluttering during their transport in the conveying level E19 of the suction belt table 19, a support plate is preferably provided in the area between the conveying level E19 of the suction belt table 19 and the side of the blowing box 37 facing this conveying level E19. B.A support plate, e.g., in the form of an air-permeable grid, is arranged at an acute angle to the side of the blow box 37 facing the conveying plane E19 of the suction belt table 19. The sheet, lifted by the suction of the blowing air and placed against the support plate, is guided there in a smooth motion, i.e., without fluttering, in its transport direction T along this support plate. In the conveying plane E19 of the suction belt table 19, at least in one area opposite the blow box 37, there are preferably several openings 39 ( Fig. 3) provided, through which air flows under the currently lifted sheet to equalize the pressure. These openings 39 are, for example, circular with a diameter in the range of a few millimeters. In addition, several suction chambers 41, controllable in their respective flow-related effects, are arranged below the conveying level E19 of the suction belt table 19. These suction chambers 41 are preferably arranged one behind the other in the transport direction T of the sheet and, for example, can be switched individually and independently of each other in their respective pressure by means of a suction device controlled by the control unit 71.

[0022] Fig. Figure 3 shows a top view of the area in the Fig. 2 suction belt table 19 shown. The transport direction T of the sheets is as shown in the Fig. 2 from right to left. Individual sheets are sequentially fed to the suction belt table 19 by a transport device that conveys the sheets translationally, in particular by a transport device belonging to a dryer 17. The sheets each rest on at least one conveyor belt 18, preferably on several, e.g., on two conveyor belts 18 arranged parallel to each other in the transport direction T of the sheets. These conveyor belts 18 are each designed, for example, as endlessly circulating flat belts. At the transition from the transport device upstream of the suction belt table 19 to this suction belt table 19, a guide device 42 extending transversely to the transport direction T of the sheets is arranged, preferably with several lifting nozzles 43 arranged in at least one row. In the transport direction T of the sheets, at least one transfer belt 44 then follows, which, for example,The conveyor belt is a circumferential flat belt arranged in the central region of the conveying plane E19 of the suction belt table 19 and is also preferably designed as a suction belt, wherein the suction belt has at least partial perforation. In the transport direction T of the sheet, after the transfer belt 44 or in its effective area, at least one kink 46 follows in the conveying plane E19 of the suction belt table 19, preferably for a gradual curvature of the previously, e.g., horizontal conveying plane, several successive kinks 46; 47, wherein at each of these kinks 46; 47 the conveying plane E19 of the suction belt table 19 experiences, optionally, a further downward inclination with an acute angle in the range between 5° and 30° relative to the previous orientation of the conveying plane. In the area described in the... Fig. 2 and Fig. In the example shown in Figure 3, two successive kinks 46 and 47 are depicted, the first kink 46 being located within the effective area of ​​the transfer belt 44 and the second kink 47 being arranged at a short distance of less than one arc length in the transport direction T of the arc downstream of the transfer belt 44. In the conveying plane E19 of the suction belt table 19, for example, two ramp belts 48, preferably in the form of continuous belts, preferably each designed as a suction belt, are arranged symmetrically to its center line M, spanning the distance between the kinks 46 and 47.The ski jump conveyors 48 are pivotably mounted at their rear end in the transport direction T of the bows, which is thus the first end reached by a bow brought in, in particular, by the receiving conveyor 44, so that these ski jump conveyors 48 can be pivoted obliquely upwards out of the previous conveying level E19 of the suction conveyor table 19 at an acute angle opening in the transport direction T of the bows and, in their extended operating state, form an erected ramp for the bows to be transported. In the . Fig. Figure 2 shows the skid belts 48 in their normal operating state, i.e., not swung out and preferably flush with the remaining conveying plane E19 of the suction belt table 19. In a preferred embodiment, at least in the respective longitudinal edge regions of the area of ​​the conveying plane E19 of the suction belt table 19 spanned by the skid belts 48, several nozzles 49, preferably each designed as a Venturi nozzle, are arranged.

[0023] Above the conveying level E19 of the suction belt table 19, a catching blower 51 extending transversely to the transport direction T of the bow is arranged at a distance A51 ( Fig. 2 and Fig. 3), wherein this catching blower 51 has several blow nozzles arranged in a row extending over the entire width B19 of the conveying plane E19 of the suction belt table 19. Below the catching blower 51, in the conveying plane E19 of the suction belt table 19, particularly in its central region, a switching area 52 extending in the transport direction T of the arc and having several suction bores 53 begins.The suction bores 53 in the switching area 52 form and open a flow-related connection to at least one of the preferably several suction chambers 41 arranged below the conveying level E19 of the suction belt table 19, wherein these suction chambers 41 are switched, or at least switchable, by the control unit 71, in particular individually and independently of one another, with respect to their respective pressure, so that a vacuum can be set, or at least adjustable, in this switching area 52 by means of the suction bores 53 and by the respective adjustment of the pressure in the respective suction chamber 41 in the conveying level E19 of the suction belt table 19. The suction bores 53 arranged in the switching area 52 are, for example, arranged symmetrically to the center line M of the conveying level E19 of the suction belt table 19 in several, for example, two rows and each designed, for example, as a suction cup utilizing the Bernoulli effect. In the transport direction T of the arc, the switching area 52 is adjoined, for example, by...In a manner overlapping with the switching area 52, at least one feed belt 54, in particular designed as a suction belt, is attached, wherein the suction belt has at least a section of perforation, and wherein the at least one feed belt 54 extends in the transport direction T of the sheets preferably to below the blowing box 37 of the under-shrinking device. The at least one feed belt 54 is preferably designed as a continuous, circulating belt. In a preferred embodiment, for example, several, e.g., two, feed belts 54 are provided symmetrically to the center line M of the conveying plane E19 of the suction belt table 19. The area that extends in the conveying plane E19 of the suction belt table 19 opposite the blowing box 37 and in which preferably several openings 39 (. Fig. 3) are provided, through which air flows under a bow currently lifted by the under-shrinking device for pressure equalization, the bow extends at least partially along the edge in the conveying plane E19 of the suction belt table 19 in the transport direction T to the at least one feed belt 54.

[0024] In the transport direction T of the sheets, after the at least one feed belt 54 and / or after the under-shrinking device in the conveying plane E19 of the suction belt table 19, brake belts 56, preferably each designed as a continuous belt and arranged symmetrically to its center line M, follow the at least one feed belt 54 and / or the under-shrinking device in the conveying plane E19 of the suction belt table 19. These brake belts have the function of reducing the respective transport speed of the sheets brought forward before their transfer to a transport device immediately downstream of the suction belt table 19, e.g. a vibrating gripper 21.The sheets, preferably with reduced transport speed, are then gripped by a rotating or at least rotatable suction roller 57 as they continue their movement in the transport direction T. This suction roller 57 extends transversely to the transport direction T of the sheets, preferably at least over the entire width of the sheets or over the entire width B19 of the suction belt table 19. Each sheet then passes successively and individually, held by the suction roller 57, with its leading edge in the transport direction T, i.e., its front edge, against, for example, the front marks 36 of the oscillating gripper 21 immediately downstream of the suction belt table 19.Through the interaction of the under-shrinking device, the brake bands 56, the suction roller 57 and the front marks 36 of the vibrating gripper 21, the sheets, which were previously transported individually, one behind the other with a gap between them, are transferred into a shingle stream before these sheets are transferred to a transport device immediately downstream of the suction belt table 19, e.g. to a vibrating gripper 21, in order to then be transported rotaryally in a machine arrangement comprising this suction belt table 19, e.g. designed as a digital printing machine, to a coating device 22, e.g. to a coating device 22 designed as a painting device and through it.

[0025] In the operation of such a machine arrangement, particularly in the industrial printing process of a digital printing press, malfunctions can occur from time to time for various reasons in a processing station downstream of the suction belt table 19, e.g., a coating unit 22. A serious malfunction in such a processing station results in the abrupt interruption of the transfer of sheets to the transport unit downstream of the suction belt table 19. This operating condition constitutes a stop. In the event of a stop, sheets in transit within the machine arrangement must be collected and stacked very quickly and effectively. However, in a machine arrangement comprising a digital printing press, it is not possible, due to the design constraints, particularly the lack of sufficient vertical space, to implement this in a processing station upstream of the suction belt table 19, such as a coating unit 22.In a first coating unit 05, or in the non-impact printing unit 13, or in one of the dryers 17 downstream of the non-impact printing unit 13, a large number of sheets transported in rapid succession, i.e., at high transport speed and closely spaced, are to be collected and stacked one after the other. It is not a satisfactory solution to arrange an ejection device in the transport direction T of the sheets after the dryer 17 downstream of the non-impact printing unit 13 and before the suction belt table 19, whereby this ejection device, upon reaching a stop, directs all sheets still exiting the dryer 17 downstream of the non-impact printing unit 13 under the suction belt table 19 and deposits them there. This is because the sheets are only deposited there in a more or less orderly fashion. This solution also has the disadvantage that sheets collected under the suction belt table 19 can only be removed again under ergonomically very unfavorable conditions.Furthermore, there is hardly any possibility of arranging the necessary conveying elements in the area of ​​the discharge device for the transfer of the flow of individual sheets from the dryer 17 during trouble-free operation. Without such suitable conveying elements, however, there is a risk of loss of the holding force with which the sheets, which are usually considerably warped due to the heat input during drying, are held. A disruption in the transport of the sheets would result. Therefore, the task arises to catch and stack the sheets on the suction belt table 19 before they are transferred to the transport device downstream of the suction belt table 19. However, it must be noted that it is not possible to implement continuous under-shrinking for stacking at the under-shrinking device of the suction belt table 19.This is because the nozzles, which act by suction from above on the trailing edge of the relevant sheet to create under-scaling, are ineffective at the latest with an immediately following sheet, since the preceding sheet is not transported away when the sheets are collected and thus shields the suction effect on the next sheet below.

[0026] A suction belt table 19 with a catching device 58 is therefore proposed, by which the catching device 58 catches and stacks successive individual sheets on the suction belt table 19 before they are transferred to a transport device downstream of the suction belt table 19. In a preferred embodiment, this suction belt table 19, which preferably has an undercutting device, is arranged in the transport direction T of the sheets after a dryer 17 downstream of a non-impact printing device 13. In a particularly preferred embodiment, the suction belt table 19 is arranged in a machine arrangement at a point where the sheets are transferred from a linear transport section immediately upstream of this suction belt table 19 to a curved, in particular arc-shaped, transport section immediately downstream of this suction belt table 19.

[0027] The proposed catching device 58 has a push-crank mechanism, the coupling of which has at least one stop surface 66 for the bows to be caught. Details of the catching device 58 and its operation are described below with reference to the Fig. 4, Fig. 5 to Fig. 6 described.

[0028] Fig. Figure 4 shows an exemplary side view of the catching device 58. This catching device 58 is, as long as it is inactive, i.e., not actuated by the control unit 71, arranged below the conveying level E19 of the suction belt table 19, preferably at approximately an arc length extending in the transport direction T of the sheet from a line drawn perpendicular to the conveying level E19 of the suction belt table 19 by the catching blower 51 at a distance A51, at the end of the switching area 52 of this suction belt table 19 which has suction bores 53. The catching device 58 has a drive 59, which is preferably designed as a double-acting pneumatic cylinder 81, the cylinder piston 82 of which can be pressurized with compressed air on both sides ( Fig. 8) A bidirectionally linearly movable piston rod 61 of the pneumatic cylinder 81 is connected to a crank 62 designed as an angle lever via a pivot point G61. The crank 62 is rotatably mounted in a pivot point D62 fixed in the suction belt table 19. The angle lever crank 62 has a short lever and a longer lever. The short lever connects the pivot point G61, where the piston rod 61 of the pneumatic cylinder 81 is connected to the crank 62, to the pivot point D62 of the crank 62. The crank 62 is, in turn, connected to a coupling 63 via a pivot point G62. The longer lever of the crank 62 extends between its pivot point D62 and the pivot point G62 where the crank 62 is connected to the coupling 63.The coupling 63 and the crank 62 driving the coupling 63 together form a push-crank mechanism, wherein an end point E2 of the coupling 63, facing away from the drive 59 of the catch device 58, is bidirectionally linearly movable along a path 64 arranged parallel to the conveying plane E19 of the suction belt table 19. The end point E2 of the coupling 63, facing away from the drive 59 of the catch device 58, and the pivot point D62 of the crank 62 therefore lie on a straight line G64 connecting them, this straight line G64 being parallel to the conveying plane E19 of the suction belt table 19.

[0029] The coupling 63 has at least one stop surface 66 for catching bows in a region between its end point E1, which faces the drive 59 of the catching device 58, and the pivot point G62, where the crank 62 is connected to the coupling 63. The stop surface 66 is therefore preferably a component of the coupling 63. The stop surface 66 is preferably made of a plastic, e.g., a polyamide (abbreviation PA) or a thermoplastic such as polyoxymethylene (abbreviation POM).

[0030] In a preferred embodiment, the sliding crank mechanism has a central sliding crank, meaning that the three in the Fig. The segments G62-D62, G62-E2, and G62-E1 shown in the diagram are each of equal length, and the endpoints E1 and E2 of the coupling 63, together with the pivot point G62 located between them, all lie on a straight line G63 connecting the endpoints E1 and E2 of the coupling 63. The short lever and the longer lever of the crank 62 are designed such that their length ratio to each other is such that they translate a movement triggered by the drive 59 of the catch 58 and acting on the coupling 63 into a faster motion. The transmission ratio i into a faster motion is preferably at least 1:5 (i = 0.2).

[0031] In connection with the Fig. 5, Fig. 6 to Fig. Figure 7 shows the function of the trapping device 58. Fig. 2 and Fig. Figure 5 shows the arresting device 58 in its inactive, i.e., unactuated, starting or parked position, in which the at least one stop surface 66 formed on the coupling 63 is arranged below the conveying plane E19 of the suction belt table 19. Thus, the sheets can pass the suction belt table 19 unhindered in its conveying plane E19, which in the Fig. 5 is indicated by two consecutive directional arrows. As can be seen from the Fig. As can be seen in Figure 5, the piston rod 61 of the pneumatic cylinder 81 forming the drive 59 of the catch device 58 is extended by applying compressed air to this pneumatic cylinder 81, and the end point E2 of the coupling 63, which is furthest away from the drive 59 of the catch device 58, assumes its position furthest from the drive 59 of the catch device 58 on the track 64.

[0032] The Fig. 6 and Fig. Figure 7 shows the arresting device 58 in its arresting position. In the arresting position, the at least one stop surface 66, preferably formed on the coupling 63, penetrates a corresponding opening 67, e.g., a slot-shaped one. Fig. 3) the conveying plane E19 of the suction belt table 19 and, by means of a pivoting movement, positions itself from a previously inclined position at a preferably acute angle to the conveying plane E19 of the suction belt table 19 preferably perpendicular to this conveying plane E19 ( Fig. 6 and Fig. 7), so that sheets transported on the suction belt table 19 collide with at least one stop surface 66, which projects approximately 50 mm from the conveying plane E19 of the suction belt table 19 (see directional arrows in the Fig. 6) and are thus caught and prevented from progressing further in the transport direction T. Successively transported sheets, each striking the erected stop surface 66, are placed on top of each other in the transport direction T in front of the erected stop surface 66 and thus stacked. In the catch position, the piston rod 61 of the pneumatic cylinder 81, which forms the drive 59 of the catch device 58, is retracted by applying compressed air to this pneumatic cylinder 81, and the end point E2 of the coupling 63, which is furthest away from the drive 59 of the catch device 58, assumes its position on the track 64 closest to the drive 59 of the catch device 58.

[0033] Fig. Figure 7 shows an excerpt from the Fig. 2 with skid belts 48, which are shown in their operating state, angled obliquely upwards from the previous conveying level E19 of the suction belt table 19, opening at an acute angle in the transport direction T of the arc, and with a catching blower 51 activated, e.g., by the control unit 71, the activation of which in the Fig. 7 is indicated by a blow direction arrow directed towards the conveying level E19 of the suction belt table 19.

[0034] If the operating condition that causes a stop occurs, namely a serious malfunction in a processing station downstream of the suction belt table 19, e.g., a coating unit 22, of the machine arrangement comprising the suction belt table 19, resulting in the abrupt interruption of the transfer of sheets to the transport unit downstream of the suction belt table 19, then the catching device 58 is switched to its catching position by automatically, in particular program-controlled, actuating the drive 59 of the catching device 58 by a control unit 71, typically by the control unit 71 that also controls other, preferably all, functions of the suction belt table 19. This control unit 71 also controls, for example, the valves of the blow box 37 ( Fig. 2) Simultaneously with the actuation of the catch device 58, the transport speed of the sheets can be reduced, for example, by reducing the respective transport speed of the transport devices upstream of the catch device 58 in the transport direction T of the sheets. Even if the transport speed of one of the transport devices upstream of the catch device 58 in the transport direction T of the sheets is not reduced immediately upon actuation of the catch device 58, e.g.If the transport speed of the skid belts 48 and / or the feed belt 54 is reduced, the negative pressure set in the relevant suction chamber 41 by means of a suction device 72 controlled by the control unit 71 is switched off in every case. This suction chamber 41 is fluidically connected to the relevant switching area 52 by means of the suction bores 53 formed in the conveying plane E19 of the suction belt table 19 and overlaps at least partially with a plan view of the stack of sheets to be caught. Then, the at least one stop surface 66 of the catching device 58 is inserted into a gap between the trailing edge of a preceding sheet and the leading edge of the first subsequent sheet to be caught.For this purpose, the control unit 71 actuates at least one pneumatic switching valve 86, preferably simultaneously two pneumatic switching valves 86; 87, so that the piston rod 61 of the pneumatic cylinder 81 forming the drive 59 of the catch device 58 is retracted.

[0035] In an advantageous embodiment, this pneumatic cylinder 81 has a bottom chamber 68 and a bearing chamber 69 separated from the bottom chamber 68 by a cylinder piston 82 rigidly connected to the piston rod 61, wherein a first pneumatic switching valve 86 is connected to the bottom chamber 68 and a second pneumatic switching valve 87 is connected to the bearing chamber 69. These two switching valves 86 and 87 are each controlled by the control unit 71 of the catch device 58. In a first embodiment, the bottom chamber 68 can be pressurized by barometric pressure. In another embodiment, the bottom chamber 68 can have a differential pressure greater than the barometric pressure and less than the pressure in the bearing chamber 69. In a preferred embodiment, the piston rod 61 of the pneumatic cylinder 81, which forms the drive 59 of the catch device 58, is retracted by pressurizing the bearing chamber 69, e.g., to 7 bar.During the retraction of the piston rod 61 of the pneumatic cylinder 81, the cylinder piston 82 works against compressed air pre-charged in the bottom chamber 68, e.g., at 2 bar. This compressed air can escape in a throttled manner via the open pneumatic switching valve 86 of the bottom chamber 68 and, if necessary, via a subsequent throttle valve 91. The braking effect of this counter-pressure only begins relatively late, so that the movement of the cylinder piston 82, and thus also of the piston rod 61, initially experiences a very high acceleration with a resulting velocity before the movement of the cylinder piston 82 is slowed at its end by the actively clamped column of air, and the residual velocity is reduced by an end-position damping element 83; 84 of the pneumatic cylinder 81.This very fast movement of the cylinder piston 82 is greatly increased by the crank 62 to the coupling 63 arranged in a central push-crank position, preferably with a transmission ratio i to the faster speed of at least 1:5 (i = 0.2).

[0036] The proposed push-crank mechanism makes it possible to move the at least one stop surface 66 of the catch device 58 into the catch position even at high sheet transport speeds of several thousand sheets per hour, e.g., approximately 10,000 sheets per hour, through a sheet gap measuring, for example, only about 20 mm. The reaction time achievable with the proposed push-crank mechanism thus significantly exceeds the switching times of simple folding and / or sliding mechanisms, which are driven, for example, by switching magnets or directly, i.e., without a gear, by a pneumatic cylinder 81. A further advantage of the solution is that the proposed push-crank mechanism is comparatively simple and space-saving.

[0037] This results in a machine arrangement with several processing stations, each handling sheets, wherein these processing stations are arranged one behind the other in the transport direction T of the sheets, wherein at least one of these processing stations has a transport device 18 for transporting the sheets lying down along a linear transport path, wherein this transport device 18 is designed to transport individual sheets in a sequence immediately following one another, spaced apart from each other by a gap, wherein a suction belt table 19 is arranged downstream of this transport device 18 for transporting the sheets lying down along a linear transport path, wherein the suction belt table 19 has a catching device 58 with a catching position assumed as a result of an actuation for individual sheets following one another in a sequence, wherein the catching device 58 in its catching position is determined by the transport device 18,The suction belt table 19, which transports the sheets lying down along a linear transport path and is located upstream of the suction belt table 19, catches and stacks the sheets fed to the suction belt table 19 before each transfer to a transport device downstream of the suction belt table 19. A control unit 71 provided for the suction belt table 19 actuates the catching device 58 depending on a fault occurring in a processing station downstream of the suction belt table 19, such that the catching device 58 assumes its catching position. In the preferred embodiment, the transport device 18 upstream of the suction belt table 19, which transports the sheets lying down along a linear transport path, belongs to a dryer 17. This dryer 17 is, for example, downstream of a processing station designed as a non-impact printing device 13. The suction belt table 19 is also preferably downstream of a coating device 22.In particular, a processing station designed as a coating unit is arranged upstream of the coating unit 22. The coating unit 22, as a transport device for sheets to be transported, has in particular a transport cylinder 23, wherein a printing cylinder 24 preferably interacts with this transport cylinder 23 and has an application roller 26 attached to, or at least attachable to, this printing cylinder 24, wherein at least one doctor blade 27 or a chambered doctor blade system 27 extends in the axial direction of the application roller 26. This machine arrangement is designed to transport the sheets at a transport speed preferably of several thousand sheets per hour, in particular of about 10,000 sheets per hour. The transport device 18, arranged upstream of the suction belt table 19, which transports the sheets lying down along a linear transport path,The individual arcs, which follow each other immediately in a sequence, are each designed to transport the material with an arc gap preferably measuring approximately 20 mm.

[0038] This results in a suction belt table 19 for individually transporting arc-shaped substrates lying down, wherein the suction belt table 19 is arranged between a transport device arranged upstream of the substrates in the transport direction T and a correspondingly downstream transport device, wherein the suction belt table 19 has a catching device 58 with a catching position assumed as a result of its actuation for individual substrates following one another in a sequence, wherein the catching device 58 in its catching position catches substrates supplied to the suction belt table 19 by the upstream transport device before their respective transfer to the transport device downstream of the suction belt table 19, i.e. prevents them from progressing in the transport direction T and preferably stacks them.The transport device upstream of the suction belt table 19 has a translational transport section for the individually lying, arc-shaped substrates to be transported, and / or the transport device downstream of the suction belt table 19 has a rotary transport section or a translational transport section for the arc-shaped substrates to be transported. A control unit 71, in particular a digital one, is provided, wherein this control unit 71 actuates the gripping device 58 depending on a disturbance that has occurred along the transport section belonging to the transport device downstream of the suction belt table 19, such that the gripping device 58 assumes its gripping position.The catching device 58 has at least one pivotable stop surface 66 for substrates to be caught, wherein the stop surface 66 is arranged below a conveying level E19 of the suction belt table 19 when the catching device 58 is not actuated by the control unit 71, and is pivoted through an opening 67 in the conveying level E19 of the suction belt table 19 and positioned perpendicular to this conveying level E19 when the catching device 58 is actuated by the control unit 71, so that substrates transported on the suction belt table 19 collide with the at least one stop surface 66 projecting from the conveying level E19 of the suction belt table 19. In its preferred embodiment, the catching device 58 has a push-pull drive, wherein the push-pull drive has a coupling 63 and a crank 62 interacting with the coupling 63, the crank 62 being driven by a drive 59.The crank 62 is rotatably mounted in a pivot point D62 fixed in the suction belt table 19. The crank 62 is designed as an angled lever and has a short lever and a longer lever. The short lever connects a pivot point G61, where the drive 59 engages the crank 62, with the pivot point D62 of the crank 62. The longer lever of the crank 62 extends between its pivot point D62 and a pivot point G62, where the crank 62 is connected to the coupling 63. The length ratio of the short and longer levers of the crank 62 is such that they amplify a motion acting on the coupling 63 from the drive 59 of the catch device 58. The amplification ratio i is preferably at least 1:5.An endpoint E2 of the coupling 63, facing away from the drive 59 of the catching device 58, is bidirectionally linearly movable along a path 64 arranged parallel to the conveying plane E19 of the suction belt table 19. The endpoint E2 of the coupling 63, facing away from the drive 59 of the catching device 58, and the pivot point D62 of the crank 62 are arranged on a straight line G64 connecting these two points, this straight line G64 being parallel to the conveying plane E19 of the suction belt table 19. The at least one stop surface 66 for substrates to be caught is formed in a region between an endpoint E1 of the coupling 63 facing the drive 59 of the catching device 58 and the pivot point G62, at which the crank 62 is connected to the coupling 63.The sliding crank mechanism preferably has a central sliding crank in which the three sections G62-D62; G62-E2; G62-E1 are each of equal length and the endpoints E1; E2 of the coupling 63, together with the pivot point G62 located between them, are all arranged on a straight line G63 connecting the endpoints E1; E2 of the coupling 63. The drive 59 of the catch device 58 is advantageously designed as a double-acting pneumatic cylinder 81, wherein this pneumatic cylinder 81 has a bottom chamber 68 and a bearing chamber 69 separated from the bottom chamber 68 by a cylinder piston 82 rigidly connected to its piston rod 61. The bearing chamber 69 is arranged at the end of the pneumatic cylinder 81 that faces the pivot point G61 where the drive 59 engages the crank 62.The bottom chamber 68 is located at the end of the pneumatic cylinder 81 that is furthest from the pivot point G61, where the drive 59 engages the crank 62. A first pneumatic switching valve 86 is connected to the bottom chamber 68, and a second pneumatic switching valve 87 is connected to the bearing chamber 69. These two switching valves 86 and 87 are each controlled by the control unit 71 of the catch device 58. The bottom chamber 68 is either pressurized by barometric pressure or it has a differential pressure greater than the barometric pressure and less than the pressure in the bearing chamber 69. The piston rod 61 of the pneumatic cylinder 81 is retracted by pressurizing the bearing chamber 69, for example, to 7 bar. The cylinder piston 82 of the pneumatic cylinder 81 works against the bottom chamber 68, e.g., when the piston rod 61 of the pneumatic cylinder 81 is retracted.Compressed air pre-charged to 2 bar, wherein this compressed air is provided from a compressed air source 93 connected to the bottom chamber 68.

[0039] A suction belt table 19 is also provided for the horizontal transport of individual arc-shaped substrates in a conveying plane E19, wherein the suction belt table 19 has a catching device 58 and at least one ramp belt 48, wherein the catching device 58 and the at least one ramp belt 48 are each controlled by a control unit 71 and are optionally configured to assume one of two different operating states, wherein, with reference to the catching device 58 and the at least one ramp belt 48, the first operating state is an inactive operating state and the second operating state is an activated operating state, wherein the catching device 58 in its activated state has at least one stop surface 66 for substrates to be caught, positioned perpendicular to the conveying plane E19 of the suction belt table 19.wherein the at least one ramp belt 48 is arranged in the transport direction T of the substrates by at least one substrate length extending in the transport direction T of the substrates in front of the at least one stop surface 66 which is positioned perpendicular to the conveying plane E19 of the suction belt table 19, wherein the at least one ramp belt 48, in its activated state, is pivoted obliquely upwards out of the conveying plane E19 of the suction belt table 19 with its end directed in the transport direction T of the substrates at an acute angle opening in the transport direction T of the substrates. The suction belt table 19 is arranged between a transport device arranged upstream in the transport direction T of the substrates and a correspondingly downstream transport device.wherein the transport device upstream of the suction belt table 19 has a translational transport section for the individually horizontally transported arc-shaped substrates and / or the transport device downstream of the suction belt table 19 has a rotary transport section or a translational transport section for the arc-shaped substrates to be transported. Advantageously, in an area extending in the transport direction T of the substrates between the erected stop surface 66 of the catching device 58 and the at least one ramp belt 48 pivoted obliquely upwards at an acute angle out of the conveying plane E19 of the suction belt table 19, a catching blower 51 with several blow nozzles arranged in a row extending transversely to the transport direction T of the substrates is arranged above the conveying plane E19 of the suction belt table 19.wherein the capture blower 51, in its activated state, blows air from its nozzles, e.g., vertically in the direction of the conveying plane E19 of the suction belt table 19. The control unit 71 actuates the capture device 58 depending on a disturbance that has occurred along the transport section belonging to the transport device downstream of the suction belt table 19, such that the capture device 58 sets its at least one stop surface 66 for substrates to be captured perpendicular to the conveying plane E19 of the suction belt table 19 and / or this control unit 71 actuates the at least one ramp belt 48 depending on the disturbance that has occurred along the transport section belonging to the transport device downstream of the suction belt table 19, such thatthat at least one ramp belt 48 is pivoted obliquely upwards at an acute angle out of the conveying plane E19 of the suction belt table 19 and / or this control unit 71 actuates the catch blower 51 depending on the disturbance that has occurred along the transport path belonging to the transport device downstream of the suction belt table 19, such that the catch blower 51 blows air from its nozzles in the direction of the conveying plane E19 of the suction belt table 19. The suction belt table 19 is preferably designed such thatthat, in the transport direction T of the substrates, a blow box 37 of an under-shelving device belonging to the suction belt table 19 is arranged above the conveying level E19 of the suction belt table 19 after the catching device 58. In addition, in the transport direction T of the substrates, in front of the at least one ramp belt 48 at the transition from the conveying device upstream of the suction belt table 19 to this suction belt table 19, a guide device 42 extending transversely to the transport direction T of the substrates with several lifting nozzles 43 is arranged, for example. Also, in the area extending below the conveying level E19 of the suction belt table 19, in the transport direction T of the substrates between the erected at least one stop surface 66 of the catching device 58 and the at least one ramp belt 48 pivoted obliquely upwards at an acute angle out of the conveying level E19 of the suction belt table 19, for example at least one suction chamber 41 is arranged, for example.wherein the respective suction chamber 41 is set or at least adjustable in its respective pressure by the control unit 71, wherein a vacuum is set or at least adjustable by the control unit 71 to the respective suction chamber 41 in the conveying level E19 of the suction belt table 19 by means of suction bores 53 formed in the conveying level E19 of the suction belt table 19. The vacuum set in the conveying level E19 of the suction belt table 19 by means of the suction chamber 41 is switched off in the event of a fault occurring along the transport section belonging to the transport device downstream of the suction belt table 19. The control unit 71 is preferably designed such thatthat it reduces the transport speed of the substrates, at least in the transport device arranged upstream of the trapping device 58 in the transport direction T of the substrates. Preferably, two ramp belts 48 arranged parallel to each other in the transport direction T of the arc are provided in the form of continuous, circulating belts, wherein these two ramp belts 48 are arranged symmetrically to the center line M of the conveying plane E19 of the suction belt table 19.

[0040] In the following, it is assumed that a pneumatic drive 59, controlled by the control unit 71, actuates the catching device 58. As already described, in the case of a stopper, due to the high transport speed of several thousand sheets per hour transported in the conveying level E19 of the suction belt table 19, e.g., approximately 10,000 sheets per hour, and the relatively small gap of, e.g.,Only about 20 mm is required between individual sheets that follow each other directly in their transport direction T. The at least one stop surface 66 of the catching device 58 is set up in a very short time in the conveying plane E19 of the suction belt table 19 and thus inserted into the linear transport path of the sheets. This effectively prevents the transfer of further sheets fed to the suction belt table 19 after the at least one stop surface 66 of the catching device 58 has been set up to a curved, in particular arc-shaped, transport path of a transport device downstream of the suction belt table 19. With these short switching times, a cylinder piston 82 in a pneumatic cylinder 81 exerts such a large impulse on the internal stops of this pneumatic cylinder 81, due to the kinetic energy achieved, that these stops are worn out and thus destroyed in a very short time.Therefore, there is a need for a solution for improved damping at the inner stops of the pneumatic cylinder 81, so that this pneumatic cylinder 81 has sufficient wear resistance and thus the most unrestricted possible operating time in the described use.

[0041] As from the Fig. As can be seen from Figure 8, it is therefore proposed that a pneumatic circuit be provided for the operation of the double-acting pneumatic cylinder 81 of the catch device 58, which controls the movement of the cylinder piston 82 such that the cylinder piston 82 experiences positive acceleration in the first half of its stroke and negative acceleration in the second half of its stroke following the first half. This pneumatic cylinder 81 has a bottom chamber 68 and a bearing chamber 69 separated from the bottom chamber 68 by the cylinder piston 82, the cylinder piston 82 being rigidly connected to the piston rod 61. The bearing chamber 69 is located at the end of the pneumatic cylinder 81 that faces the pivot point G61 where the drive 59 engages the crank 62.The bottom chamber 68 is arranged at the end of the pneumatic cylinder 81 that is furthest from the pivot point G61, where the drive 59 engages the crank 62. The cylinder piston 82 preferably has an end-position damping element 83; 84 on each side. The pneumatic circuit described in detail below achieves a controlled acceleration phase and a controlled deceleration phase over the entire stroke of the cylinder piston 82 by changing a dynamic pressure equilibrium in the two chambers 68; 69 of the pneumatic cylinder 81.

[0042] The pneumatic circuit comprises a first pneumatic switching valve 86 and a second pneumatic switching valve 87, both switching valves 86 and 87 being preferably electrically actuated by the control unit 71. In one of their switching positions, both switching valves 86 and 87 are each connected to their respective compressed air source 93.

[0043] Fig. Figure 8 shows the operating position of the pneumatic cylinder 81 in which the piston rod 61 of the pneumatic cylinder 81, which forms the drive 59 of the catch device 58, is retracted and thus the catch device 58 is activated, meaning that the stop surface 66 of the catch device 58 is positioned in the conveying plane E19 of the suction belt table 19. A pressure reducer 88 is preferably installed upstream of at least the switching valve 86 for the bottom chamber 68 in order to build up a defined initial back pressure in the bottom chamber 68 when the compressed air flows out. A pressure reducer 89 can also be installed upstream of the switching valve 87 for the storage chamber 69.Additionally, a throttle valve 91 is arranged downstream of the switching valve 86 of the bottom chamber 68. This throttle valve 91, whose cross-section is preferably adjustable, is used to influence the outflow velocity of the compressed air from the bottom chamber 68 and thus the dynamic pressure profile in the pneumatic cylinder 81 and consequently the speed of the cylinder piston 82. It may also be provided, for example, that a throttle valve 92 is arranged in the air outlet from the bearing chamber 69 of the pneumatic cylinder 81 to limit the speed of the cylinder piston 82. The throttle valve 91 of the bottom chamber 68 and, optionally, the throttle valve 92 of the bearing chamber 69 are only used when compressed air flows out of the respective chamber 68 / 69 into the atmosphere.

[0044] Before the locking device 58 is activated, the bearing chamber 69 of the pneumatic cylinder 81 is preferably depressurized, i.e., it is pressurized, for example, to a pressure equal to barometric pressure. In an alternative embodiment, however, the bearing chamber 69 of the pneumatic cylinder 81 can also be pressurized via the pressure reducer 89, optionally to a pressure greater than barometric pressure, e.g., to a pressure corresponding to the pressure in the bottom chamber 68, preferably to a pressure of, for example, 2 bar. When the pressure set in both chambers 68 and 69 is equal, the cylinder piston 82 is held in a stable end position. In the bottom chamber 68, which is pressurized with compressed air, e.g., to 2 bar, a pressure-controlled mass of air is provided, which is required to decelerate the movement of the cylinder piston 82 when the locking device 58 is activated.The activation of the catching device 58, by the insertion of its at least one stop surface 66 into a gap between the trailing edge of a preceding sheet and the leading edge of the first subsequent sheet to be caught, is effected by the simultaneous actuation of the two switching valves 86 and 87 by the control unit 71. This fills the storage chamber 69 with compressed air from its compressed air source 93 at a pressure exceeding 5 bar, in particular at a pressure of, for example, 7 bar. The air in the bottom chamber 68, pre-pressurized to approximately 2 bar, can then escape into the atmosphere via the throttle valve 91, resulting in a pressure differential of approximately 5 bar and thus a corresponding force on the cylinder piston 82, which sets this cylinder piston 82 in motion.Controllable via the air mass enclosed in the bearing chamber 69 and the opening cross-section of the throttle valve 91, the braking effect is activated such that the movement of the cylinder piston 82 initially experiences a very high acceleration with a resulting velocity, before this movement of the cylinder piston 82 is largely decelerated at the end by the actively clamped air column, and only a remaining residual velocity of less than, for example, 10% of the previously reached maximum possible velocity is decelerated at the end-position damping element 83 of the pneumatic cylinder 81. When the catch device 58 is activated, the cylinder piston 82 is accelerated over the first half of its stroke and decelerated over its second half. In the first half of its stroke, the cylinder piston 82 reaches its maximum possible velocity. In the theoretically ideal case, the cylinder piston 82 arrives at its respective end position at zero velocity.In real-world operation, however, this is not achieved. Therefore, the small remaining residual energy must be dissipated at the respective end-position damping element 83; 84. This very rapid movement of the cylinder piston 82 is transmitted by the crank 62 to the coupling 63, which is preferably arranged in a centrally located push-crank position, via a high gear ratio.

[0045] The described pneumatic circuit and the exemplary pressure settings make it possible to bring the at least one stop surface 66 of the catching device 58 into a catching position even at the aforementioned high sheet transport speed through the very narrow sheet gap. Advantageously, the solution presented avoids high shock loads and peak loads throughout the entire kinematic system. This is because the clamped air column, which dampens the drive movement of the cylinder piston 82 at the end, particularly in the bottom chamber 68, effectively prevents damage to the cylinder base. Furthermore, a secure end position of the cylinder piston 82 in its retracted state is achieved without additional mechanical elements and thus without additional costs. The pressure reduction in the bearing chamber 69 also results in energy savings and a reduction in potential leakage.

[0046] The Fig. 9, Fig. 10, Fig. 11 to Fig. Figure 12 illustrates, by way of example, in a diagram over time t plotted on the abscissa, the dynamic behavior of some physical quantities with reference to the cylinder piston 82 of the pneumatic cylinder 81 during a switching operation, when the catching device 58 of the suction belt table 19 in question is moved from its initial position to its catching position, in particular by a control signal from the control unit 71. Fig. Figure 9 shows a change in position of the cylinder piston 82 between its two end positions in the pneumatic cylinder 81. The stroke z, and thus the travel of the cylinder piston 82, is shown here, for example, as 10 mm. Fig. Figure 10 shows, by way of example, the velocity v of the cylinder piston 82 during its movement along the positioning path z. Fig. Figure 11 shows, by way of example, the corresponding acceleration a with which the cylinder piston 82 performs its movement along the stroke z. In the Fig. Figure 12 then shows, by way of example, the piston force F exerted by the cylinder piston 82.

[0047] As described, a suction belt table 19 is provided for the horizontal transport of individual arc-shaped substrates in a conveying plane E19, wherein the suction belt table 19 has a catching device 58 with at least one stop surface 66 for substrates to be caught, which in its catching position is positioned in the conveying plane E19 of the suction belt table 19, wherein this at least one stop surface 66 is positioned in the catching position by a double-acting pneumatic cylinder 81 from an inactive starting position of the catching device 58 by a movement of its cylinder piston 82, wherein this pneumatic cylinder 81 has a bottom chamber 68 and a bearing chamber 69 separated from the bottom chamber 68 by the cylinder piston 82, wherein a pneumatic circuit is provided for controlling the movement of the cylinder piston 82.The pneumatic circuit comprises a first pneumatic switching valve 86 connected to the bottom chamber 68 and a second pneumatic switching valve 87 connected to the bearing chamber 69, both switching valves 86 and 87 being preferably electrically actuated by the control unit 71. The catch device 58 has a sliding crank mechanism driven by the piston 82 of the pneumatic cylinder 81, as described above. The movement of the piston 82 is controlled by the control unit 71 such thatthat the cylinder piston 82 experiences positive acceleration in the first half of its stroke and negative acceleration in the second half of its stroke following the first half. A pressure reducer 88 is arranged upstream of at least the first switching valve 86 connected to the bottom chamber 68. A throttle valve 91, preferably adjustable in its opening cross-section, is also arranged downstream of at least the first switching valve 86 connected to the bottom chamber 68. The opening cross-section of the throttle valve 91 is adjusted, for example, by the control unit 71, such that the movement of the cylinder piston 82 at the end of the second half of its stroke exhibits a residual velocity of less than 10% of the maximum velocity previously achieved in the first half of its stroke. The cylinder piston 82 preferably has an end-position damping element 83; 84 on each side.wherein the residual velocity of the cylinder piston 82 remaining at the end of the second half of its stroke is braked at the respective end-position damping element 83; 84. In the inactive starting position of the catch device 58, at least the bottom chamber 68 of the pneumatic cylinder 81 is pressurized to a pressure greater than the barometric pressure, preferably to a pressure of, for example, 2 bar. To set the catch position of the catch device 58, the control unit 71 switches the first switching valve 86, connected to the bottom chamber 68, into a position that discharges the air mass from the bottom chamber 68, and simultaneously switches the second switching valve 87, connected to the bearing chamber 69, so that the bearing chamber 69 is pressurized with compressed air at a pressure of more than 5 bar.

[0048] In connection with the Fig. Section 2 describes that the suction belt table 19 has a switching area 52 extending in the transport direction T of the sheets, with several suction bores 53, wherein several suction chambers 41, controllable in their respective flow-related effects, are preferably arranged below the transport level E19 of the suction belt table 19. These suction chambers 41 are preferably arranged one behind the other in the transport direction T of the sheets and are, in particular, individually and independently switched or at least switchable in their respective pressure.It was also explained that the suction bores 53 in the switching area 52 form a fluid-technical connection to at least one of the preferably several suction chambers 41 arranged below the conveying level E19 of the suction belt table 19, wherein in this switching area 52 a vacuum is set or at least adjustable at the suction bores 53 in the conveying level E19 of the suction belt table 19 by means of a suction device 72 controlled by the control unit 71 in the respective suction chamber 41. This vacuum causes a sheet lying on the at least one feed belt 54 in the conveying level E19 of the suction belt table 19 to be held by friction or force. This is because the switching area 52 overlaps at least partially with the plan view of the sheet to be caught. The feed belt 54 in question is, for example,The suction belt is designed as an endlessly circulating suction belt, wherein the suction belt has at least a section perforation so that the negative pressure set at the suction bores 53 in the conveying plane E19 of the suction belt table 19 can act on the overlying sheet through the respective feed belt 54. Preferably, the feed belt 54 is designed as a flat belt or a flat belt.

[0049] When a stopper is activated and the at least one stop surface 66 of the catching device 58 is moved into its catching position, the frictional or force-fit connection between the respective feed belt 54 and the sheet resting on it must be released very quickly, because otherwise the sheet resting on the feed belt 54 would be crumpled upon impact with the at least one stop surface 66 of the catching device 58, which projects from the conveying plane E19 of the suction belt table 19. This is particularly important at a transport speed of several thousand sheets per hour, e.g., approximately 10.At 000 sheets per hour, it is neither possible to eliminate the negative pressure set in the relevant suction chamber 41 by means of the suction device 72 controlled by the control unit 71, and thus the holding force acting on the sheet lying on the respective feed belt 54, nor to stop the respective feed belt 54 itself in time before the sheet strikes the at least one stop surface 66 of the catch device 58. To prevent damage to a sheet lying on the respective feed belt 54 when a stopper is activated and is the first to strike the at least one stop surface 66 of the catch device 58 projecting from the conveying plane E19 of the suction belt table 19, it is therefore necessary to eliminate the aforementioned frictional engagement.to release the force connection more quickly compared to switching off the suction device 72 of the relevant suction chamber 41 and / or compared to stopping the relevant feed belt 54.

[0050] As from the Fig. As can be seen from Figure 13, it is therefore proposed that at least one pneumatically actuated valve 74, controlled by a control unit 71, be arranged in a supply line 73 pneumatically connecting the suction chamber 41 to the respective suction bores 53, wherein the actuated valve 74 interrupts the pneumatic connection when the trap 58 is moved into its trap position. In a preferred embodiment, the actuated valve 74 is designed such that, simultaneously with the interruption of the pneumatic connection between the suction chamber 41 and the respective suction bores 53, a section of the supply line 73 between the actuated valve 74 and the respective suction bores 53 is vented with barometric pressure or with a pressure increased by 3% to 10%, preferably by 5%, compared to the barometric pressure.The transport speed of the sheets corresponds to a cycle time in which immediately successive sheets reach the position of the at least one stop surface 66 of the catching device 58, which projects from the conveying plane E19 of the suction belt table 19. The switching time of the relevant indexing valve 74 is shorter than the cycle time of immediately successive sheets and is preferably in the range between 20 ms and 100 ms, particularly 40 ms. The switching time of the relevant indexing valve 74 is the time beginning at the time of its actuation until the point at which the relevant indexing valve 74 has stably switched from its first operating position to its second operating position.The control unit 71 is preferably designed such that it puts the relevant pulse valve 74 into the state that interrupts the pneumatic connection between the relevant suction chamber 41 and the respective suction bores 53 by the duration of a pulse time earlier than an actuation of the trapping device 58.

[0051] The advantage of this solution is that, in the event of a stopper being triggered, even the first sheet caught by the catching device 58 is not compressed or crumpled. Rather, the arrangement of at least one pulse valve 74, controlled by the control unit 71, in the supply line 73 between the relevant suction chamber 41 and the respective suction bores 53 ensures that the catching process is independent of any unavoidable overrun of the at least one feed belt 54 after the detection of the stopper and / or a continuous suction effect of the relevant suction chamber 41.

[0052] As already mentioned in connection with the Fig. 1, Fig. 2 to Fig. As explained in section 3, several sheets are fed to the suction belt table 19 by a transport device located immediately upstream of the suction belt table 19. These sheets are transported one after the other along a linear transport path, lying individually at least in this transport device and on the suction belt table 19, each with a narrow gap between them. In the preferred embodiment, the transport of these sheets is carried out by means of several conveyor belts arranged one after the other in the transport direction T of the sheets, starting with the circulating conveyor belt 18 of the transport device located immediately upstream of the suction belt table 19, via at least one transfer belt 44 belonging to the suction belt table 19, which is, for example, designed as a circulating flat belt preferably arranged in the central region of the conveying plane E19 of the suction belt table 19. In the transport direction T, the sheet is, for example,Two parallel ramp belts 48, e.g., in the form of continuous circulating belts, are arranged, followed by at least one feed belt 54, in particular designed as a suction belt, and, e.g., two parallel brake belts 56, each designed as a continuous circulating belt. At each transition from a continuous circulating belt - e.g.,In a transition between two successive machine units, such as from a non-impact printing unit 13, a dryer 17, or a suction belt table 19 to another machine unit, wherein at least one of these machine units has a transport device in the form of a circulating endless belt, a discontinuity exists in the mechanical support of the sheets to be transported in the conveying plane E19 of the sheets due to a gap in this conveying plane E19 with a width that is large relative to the thickness of the sheets, in the range, for example, between 1 mm and 5 mm, and wherein this discontinuity is particularly noticeable at a high transport speed of several thousand sheets per hour, e.g., of about 10.The risk of operational disruption is present at 000 sheets per hour. This is because, during the transport of sheets lying on a circulating belt, there is a danger that the leading edge of the sheet, due to its adhesion to the conveyor belt at the end of the transport path, will be deflected into the discontinuity at the end of the conveyor belt's travel distance by means of the deflecting roller 76. This prevents the sheet from being transported further and makes it an obstacle for subsequent sheets. This problem exists particularly at all transitions if at least one of the conveyor belts acting at the transition has a width extending transversely to the transport direction T of the sheets of at least 25% of the width of the sheets to be transported. In the preferred embodiment, this is also the case, for example, at the transition from the conveyor belt immediately upstream of the suction belt table 19, e.g.,The transport device belonging to a dryer 17 to this suction belt table 19 is the case.

[0053] It is therefore proposed to replace the discontinuity in the mechanical support of the sheets to be transported in the conveying plane E19 with a pneumatic pressure force. This is achieved by arranging a guide device 42, extending transversely to the transport direction T of the sheets, with preferably several lifting nozzles 43 arranged in at least one row, at the transition from the transport device immediately upstream of, for example, the suction belt table 19 to this suction belt table 19. This guide device 42 with its multiple lifting nozzles 43 is arranged in the transport direction T of the sheets, particularly upstream of the at least one ramp belt 48 at the transition from the transport device upstream of the suction belt table 19 to this suction belt table 19.

[0054] Fig. Figure 14 shows, as an example, a top view of a section of the, e.g., in connection with the Fig. 3. The suction belt table 19 described below. An arc-shaped substrate, preferably a printed sheet, referred to as sheet 77, is transferred to the suction belt table 19 in a conveying plane E19 due to its translational movement on a circulating conveyor belt 18 belonging, for example, to a dryer 17. A rotating deflecting roller 76 is arranged below the conveying plane E19 of the suction belt table 19 and preferably flush with this conveying plane E19 at the top. The deflecting roller moves the conveyor belt 18 in the transport direction T of the sheets 77 and deflects the sheet 77 at the end of the transport device immediately upstream of the suction belt table 19. During their transition from the transport device immediately upstream of the suction belt table 19 to the suction belt table 19, the sheets 77 must overcome a discontinuity 78 located in the conveying plane E19 in their mechanical support. Transferred sheets 77 are, for example,the material is captured by a transfer belt 44 belonging to the suction belt table 19, wherein this transfer belt 44 is designed, for example, as a circumferential flat belt arranged in the central area of ​​the conveying plane E19 of the suction belt table 19 and / or as a suction belt. Following the transfer belt 44 in the transport direction T of the arc 77 are, for example, two parallel ramp belts 48, for example, in the form of continuous circumferential belts.

[0055] Fig. Figure 15 schematically and in a highly simplified manner shows, by way of example, a guide device 42 arranged in a discontinuity 78 relating to the mechanical support of the sheets 77 to be transported, with at least one lifting nozzle 43, preferably with several lifting nozzles 43, wherein this discontinuity 78 is arranged, for example, between a circulating conveyor belt 16 belonging to a non-impact printing device 13 and a circulating conveyor belt 18 belonging to a dryer 17. A sheet 77 transported in the transport direction T tends to be drawn with its leading edge into a gap extending transversely to the transport direction T of the sheets 77 at the discontinuity 78 in the periphery of the deflecting roller 76 as a result of the rotation of the deflecting roller 76, thus causing a malfunction. Such a discontinuity 78 in the mechanical support of the sheets 77 to be transported consists of a gap in the Fig. 1. An exemplary digital printing machine transporting sheets 77 horizontally is shown at several positions, e.g. at the respective transition to and after the non-impact printing unit 13 and at the transition from the dryer 17 to the suction belt table 19.

[0056] The Fig. 16, Fig. 17, Fig. 18 to Fig. Section 19 explains the operation of the guide device 42, arranged in such a discontinuity 78, which transports a sheet 77 lying down, at the transition of the sheets 77 from the non-impact printing unit 13 to a dryer 17 immediately downstream of the non-impact printing unit 13. These explanations also apply analogously to all other positions where a guide device 42 of the generic type is arranged or at least can be arranged in the machine arrangement in question, preferably designed as a digital printing machine.

[0057] Fig. Figure 16 shows the initial situation for the function of the guide device 42 arranged in the discontinuity 78. A sheet 77 resting on the circulating conveyor belt 16 belonging to the non-impact printing device 13 reaches the discontinuity 78 with its leading edge at the transition of the sheets 77, e.g., from the conveyor belt 16 of the non-impact printing device 13 to a conveyor belt 18 of a dryer 17 immediately downstream of the non-impact printing device 13.The guide device 42 has a tapered profile element 79 extending transversely to the transport direction T of the sheets 77, preferably in the form of a doctor blade, wherein the tip of this profile element 79 is preferably arranged approximately tangentially opposite to the transport direction T of the sheets 77 towards the conveyor belt 16 of the non-impact printing device 13, wherein the tip of this profile element 79 is spaced apart from the conveyor belt 16 of the non-impact printing device 13, which is deflected by the rotating deflecting roller 76, by a gap, wherein this gap has a width that is larger than the thickness of the sheets 77, in the range, for example, between 1 mm and 5 mm. At least one lifting nozzle 43 opening towards its tip is arranged in the profile element 79, through which the lifting nozzle 43, when the guide device 42 is activated, for example, by the control unit 71, e.g., Fig. 17. The air jet, indicated by a directional arrow, is directed, or at least can be directed, against the conveyor belt 16 of the non-impact printing device 13, which is deflected at the deflecting roller 76. In the state of the Fig. In the activated guide device 42 shown in section 17, the sheet 77 lying on the conveyor belt 16 of the non-impact printing device 13 has shifted due to the rotation of the deflecting roller 76 compared to the position shown in the Fig. The initial situation shown in Figure 16 increasingly approaches the gap formed for the guide device 42, whereby the leading edge of the relevant arc 77 continues to follow the curvature of the deflecting roller 76 in a manner potentially provoking an operational disruption.

[0058] As from the Fig. 18 and Fig. As can be seen in Figure 19, the air jet blown out of the at least one lifting nozzle 43 arranged in the profile element 79 during activation of the guide device 42 flows against the conveyor belt 16 of the non-impact printing device 13, which is deflected at the deflecting roller 76. This air jet strikes the conveyor belt 16 in such a way that the direction of the core jet of this air jet intersects the circular circumference of the deflecting roller 76 as a secant. Furthermore, this air jet is directed towards the conveyor belt 16 in such a way that a free upper boundary of this air jet, facing the leading edge of the relevant sheet 77, neither intersects nor exceeds a tangent between the circumference of the deflecting roller 76 and the relevant lifting nozzle 43 of the guide device 42.The air jet directed against the convex surface of the conveyor belt 16 of the non-impact printing device 13, which is deflected at the deflecting roller 76, is deflected there by the curvature of the deflecting roller 76 in the direction of the approaching leading edge of the sheet 77 in question. This air jet, which follows the curvature of the deflecting roller 76 due to the Coanda effect and is transformed into a wall flow, finally releases the leading edge of the sheet 77 in question from the conveyor belt 16 of the non-impact printing device 13. Fig. 18) and, as the deflection roller 76 continues to rotate, the leading edge of the sheet 77 in question is lifted more and more away from the conveyor belt 16 of the non-impact printing device 13 due to the resulting back pressure ( Fig. 19), so that the leading edge of the sheet 77, which is still mostly resting on the conveyor belt 16 of the non-impact printing device 13, is lifted onto the profile element 79 and thus onto the guide device 42 during its further transport.

[0059] Once the leading edge of the relevant sheet 77 rests securely on the profile element 79, the guide device 42 is preferably deactivated, e.g., by the control unit 71, by switching off the air jet flowing from the at least one lifting nozzle 43. The air jet flowing from the at least one lifting nozzle 43 is thus preferably active in a pulsed manner, with this pulse being synchronized with the arrival of the leading edge of the respective sheet 77 at the deflecting roller 76 of the conveyor belt 16 deflected by this deflecting roller 76.An air jet flowing from the at least one lifting nozzle 43 of the guide device 42 is therefore preferably maintained only until the leading edge of the respective sheet 77 has passed the gap at the discontinuity point 78 located in the periphery of the deflecting roller 76 and extending transversely to the transport direction T of the sheets 77, and the leading edge of the respective sheet 77 has been lifted onto the profile element 79 of the guide device 42.

[0060] This results in a machine arrangement with several processing stations, each processing sheets 77, wherein these processing stations are arranged one after the other in the transport direction T of the sheets 77, wherein at least one of these processing stations has a first transport device for transporting the sheets 77 along a linear transport path with at least one endlessly circulating conveyor belt 16 deflected by a rotating deflecting roller 76, wherein this first transport device is configured to transport individual sheets 77 lying on its at least one conveyor belt 16 in a sequence of immediately successive sheets 77, wherein a second transport device or a suction belt table 19 is arranged downstream of this processing station having the first transport device, which also transports the sheets 77 lying on at least one endlessly circulating conveyor belt 18 along a linear transport path.wherein at the point of transfer of the sheets 77 to be transported from the conveyor belt 16 of the first transport device either to the conveyor belt 18 of the second transport device following in the transport direction T of the sheets 77 or to the suction belt table 19 in a conveying plane E19 of these sheets 77 to be transported, a discontinuity point 78 is formed in the mechanical support of these sheets 77 to be transferred, wherein the deflecting roller 76, which deflects the at least one conveyor belt 16 of the first transport device, is arranged at the discontinuity point 78 in the mechanical support of the sheets 77 to be transferred. At this discontinuity point 78, a guide device 42 extending transversely to the transport direction T of the sheets 77 with a tapered profile element 79 is arranged,wherein the tip of this profile element 79 is directed opposite to the transport direction T of the arc 77 towards the conveyor belt 16 of the first transport device, wherein at least one lifting nozzle 43 is arranged in the profile element 79, the lifting nozzle 43 being designed to open towards the tip of this profile element 79. The tip of the profile element 79 is spaced apart from the conveyor belt 16 of the first transport device, which is deflected at the rotating deflecting roller 76, by a gap.wherein this gap has a width between 1 mm and 5 mm that is larger than the thickness of the sheets 77. In a preferred embodiment, several lifting nozzles 43 are arranged in a row extending transversely to the transport direction T of the sheets 77 in the profile element 79. When the guide device 42 is activated, e.g., by a control unit 71, an air jet flowing from the orifice of the respective lifting nozzle 43 is directed, or at least can be directed, towards the conveyor belt 16 of the first transport device, which is deflected at the deflecting roller 76. This air jet is directed towards the conveyor belt 16 such that a core jet of this air jet intersects the circumferential line of the deflecting roller 76 as a secant. The air jet in question is also, in particular, oriented such that a free,The upper boundary of this air jet, facing the leading edge of a sheet 77 transported on the conveyor belt 16 of the first transport device, neither intersects nor crosses a tangent between the circumferential line of the deflecting roller 76 and the respective lifting nozzle 43 of the guide device 42. The guide device 42 is activated by the control unit 71. The control unit 71 activates the guide device 42, for example, in a timed manner, with this time being synchronized with the arrival of the leading edge of the respective sheet 77 at the deflecting roller 76 of the conveyor belt 16 of the first transport device, which is deflected by this deflecting roller 76. The guide device 42 is therefore preferably designed to maintain the air jet flowing from the respective lifting nozzle 43 only as long as...until the leading edge of the respective sheet 77 has passed the gap at the discontinuity point 78, located in the periphery of the deflecting roller 76 and extending transversely to the transport direction T of the sheets 77, and the leading edge of the respective sheet 77 has been lifted by the air jet flowing from the respective lifting nozzle 43 to the tip of the profile element 79 of the guide device 42. The deflecting roller 76, which deflects the at least one conveyor belt 16 of the first transport device, and the guide device 42 together with its profile element 79 are each arranged below the conveying level E19 of the sheets 77 to be transported and preferably flush with this conveying level E19 at the top. Since the machine arrangement in its preferred embodiment is designed as a digital printing machine,The processing station comprising the first transport device is designed either as a non-impact printing device 13, as a dryer 17, or as a cooling section.

[0061] During a pass through a dryer 17, which e.g., uses 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, and thus lose their flatness, 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 is no longer transported in a oriented manner. As a result, curled sheets provided at the exit of the dryer 17 can be transferred by a receiving belt 44 of a transport unit immediately downstream of the dryer 17 in the transport direction T of the sheets, which, for example,Sheets belonging to a suction belt table 19 or to a cooling section can no longer be reliably picked up due to inadequate gripping. In a machine arrangement with multiple transport devices, this leads very quickly to an operational disruption, especially when such sheets follow one another at a transport speed of several thousand sheets per hour, e.g., approximately 10,000 sheets per hour. The cause of the inadequate gripping of the curled sheets lies particularly in the fact that the bending resistance forces inherent in the curling of the sheets in question cannot be overcome by a height-dependent suction force exerted by a suction belt. This problem of the unreliable pickup of sheets curled at their edges, especially at their respective leading edges, by a suction belt can also occur in the conveying plane E19 of the suction belt table 19 at a kink 46; 47, where a curvature of the previously, e.g.,horizontal conveying plane is formed (. Fig. 2 and Fig. 3) However, to avoid damaging a printed image previously applied to the top of the sheets in question in the non-impact printing unit 13, it is forbidden to force sheets that are curled at the points mentioned in the machine arrangement described here to a flat position from above, e.g. by means of a mechanical hold-down device.

[0062] In order to establish the necessary frictional or force-fit connection between a sheet, which is particularly curved by heat input, and a suction belt, and to transport this sheet with the suction belt in a positionally accurate manner, it is proposed to utilize the physical phenomenon of the aerodynamic paradox, particularly with regard to the lateral edge regions of a highly curved leading edge of a sheet to be taken over by a suction belt and / or of a sheet to be transported by a suction belt.

[0063] The solution found is explained using the suction belt table 19 described above as an example. Fig. 20 shows a magnified section from the one in the Fig. Figure 3 shows a suction belt table 19 in a top view, wherein this section relates in particular to an arrangement of nozzles 49 in an area between one of the two ramp belts 48 arranged parallel to each other in the transport direction T of the sheets and an edge 94 extending longitudinally to the transport direction T of the sheets and laterally delimiting the conveying plane E19 of the suction belt table 19. The ramp belts 48, as well as the at least one transfer belt 44 arranged upstream of them in the transport direction T of the sheets, are preferably designed in the form of continuous belts, in particular each as a suction belt, wherein the respective suction belt is in a pneumatic operative connection with a suction device 72 and, as a result of its at least partial perforation, can exert a suction force on a sheet placed on it. The transport direction T of the sheets is in the Fig. 20 indicated by a directional arrow. One blowing direction of the nozzles 49 arranged in the aforementioned area, i.e., one flow direction of an airflow exiting these nozzles 49, is, for example, directed in the transport direction T of the arc. In a preferred and in the Fig. In the embodiment shown in Figure 20, the blowing direction of the nozzles 49 arranged in this area is either orthogonal to the edge 94 laterally bounding the conveying plane E19 of the suction belt table 19 or inclined at 45° in the transport direction T of the arc towards the edge 94 laterally bounding the conveying plane E19 of the suction belt table 19. It can also advantageously be provided that the blowing direction of a first subset of the nozzles 49 is, for example, orthogonal to the edge 94 laterally bounding the conveying plane E19 of the suction belt table 19, and the blowing direction of a second subset of the nozzles 49 is, for example, inclined at 45° in the transport direction T of the arc towards the edge 94 laterally bounding the conveying plane E19 of the suction belt table 19.

[0064] Fig. 21 shows an excerpt from the one in the Fig. Figure 2 shows a side view of the suction belt table 19. It is intended that sheets fed to the suction belt table 19, particularly from a dryer 17, are to be picked up by at least one transfer belt 44 and transported further in the conveying level E19 of the suction belt table 19. In particular, in the area of ​​the at least one transfer belt 44, as well as in the area of ​​the ramp belts 48 of the suction belt table 19 downstream of the at least one transfer belt 44 in the transport direction T of the sheets, or in the transport direction T of the sheets directly following a discontinuity 78 in the mechanical support of the sheets to be transported, e.g., between the at least one transfer belt 44 belonging to the suction belt table 19 and a circulating conveyor belt 18 belonging to a dryer 17, several nozzles 49 are arranged ( Fig. 3 and Fig. 20). These nozzles 49 are in particular designed as Venturi nozzles and are connected to a compressed air source 93 by means of a pneumatically connecting supply line 96. In a preferred embodiment, a control valve 97 for adjusting and / or regulating the pressure of an airflow exiting the respective nozzle 49 is arranged in the supply line 96 connecting at least one of the nozzles 49 to the compressed air source 93. In a particularly advantageous embodiment, a pulse valve 74, controlled, for example, by the control unit 71, is arranged in the supply line 96 connecting at least one of the nozzles 49 to the compressed air source 93 between the respective control valve 97 and the respective nozzle 49. Such a pulse valve 74 is preferably controlled by the control unit 71 such that at least one of the nozzles 49 is supplied with compressed air precisely at the moment when the leading edge of a sheet to be transported overlaps with the respective nozzle 49.The supply of compressed air to the relevant nozzle 49 is interrupted by the control unit 71, in particular, when the leading edge of the sheet to be transported is covered by a nozzle 49 nearest to the sheet in the transport direction T. Furthermore, it is provided that the supply of compressed air to the nozzles 49 arranged in the plan view of a sheet to be caught is interrupted by means of the relevant control valve 74 when the catching device 58 of the suction belt table 19 is switched to its catching position.

[0065] This results in a suction belt table 19 with at least one endlessly circulating transfer belt 44 designed as a suction belt for receiving sheets transported individually in a conveying plane E19 from a conveyor belt 18 of a dryer 17, which is arranged directly upstream of the suction belt table 19 in the transport direction T of the sheets, wherein the suction belt table 19 has an arrangement of several nozzles 49 in its conveying plane E19 at least in an area between the at least one transfer belt 44 extending longitudinally to the transport direction T of the sheets and an edge 94 laterally delimiting the conveying plane E19 of the suction belt table 19, wherein these nozzles 49 are each designed as Venturi nozzles,wherein a flow direction of at least a first subset of the nozzles 49 arranged in the aforementioned area is directed in the transport direction T of the arc and / or wherein a flow direction of at least a second subset of the nozzles 49 arranged in the aforementioned area is directed orthogonally to the edge 94 laterally bounding the conveying plane E19 of the suction belt table 19 and / or wherein a flow direction of at least a third subset of the nozzles 49 arranged in the aforementioned area is inclined at 45° to the transport direction T of the arc towards the edge 94 laterally bounding the conveying plane E19 of the suction belt table 19. In addition, at least one kink 46; 47 can be formed in the conveying plane E19 of the suction belt table 19 in the transport direction T of the arc downstream of the at least one transfer belt 44,wherein at each of these kinks 46; 47 the conveying plane E19 of the suction belt table 19 experiences a downward inclination at an acute angle in the range between 5° and 30° relative to the previous orientation of the conveying plane, wherein the arrangement of nozzles 49 formed in the area between the at least one transfer belt 44 and the edge 94 laterally bounding the conveying plane E19 of the suction belt table 19 extends beyond the respective kink 46; 47 in the transport direction T of the sheets. In the aforementioned area or in the areas successive in the transport direction T of the sheets, the nozzles 49 are arranged, for example, in several rows extending transversely to the transport direction T of the sheets. Fig. 3 and Fig. 20).

[0066] The nozzles 49 are each connected to a compressed air source 93 by means of a pneumatically connecting supply line 96, wherein a control valve 97 is preferably arranged in at least one of the supply lines 96 connecting the nozzles 49 to the compressed air source 93 for adjusting and / or regulating the pressure of an airflow exiting the respective nozzle 49. In a preferred embodiment, a pulse valve 74 is arranged in the supply line 96 connecting the nozzles 49 to the compressed air source 93 between the control valve 97 and the nozzle 49. The control valve 97 and / or the pulse valve 74 are controlled by a control unit 71. The pulse valve 74 is activated by the control unit 71, in particular, when the leading edge of a sheet to be transported overlaps with the nozzle 49.The relevant timing valve 74 is deactivated by the control unit 71, in particular, when the leading edge of the sheet to be transported is covered by a nozzle 49 nearest the sheet in the transport direction T. In a particularly preferred embodiment, the suction belt table 19 has a catching device 58 with the features described above for catching sheets, wherein the relevant timing valve 74 is deactivated by the control unit 71 when the catching device 58 is switched to its catching position.

[0067] Since the nozzles 49 are each designed as a Venturi nozzle, they generate a suction force acting on a sheet to be transported, which is many times greater in magnitude than a holding force generated by the suction flow on a suction belt arranged in the conveying plane E19 of the suction belt table 19, which is provided to hold a sheet lying flat on the respective suction belt.

[0068] Furthermore, the width of the area containing the nozzles 49, extending transversely to the transport direction T of the sheet, is significantly larger than the width of the suction belt extending transversely to the transport direction T of the sheet. Therefore, the width of the area containing the nozzles 49, lying outside the width of the suction belt, is in a much more favorable ratio to the width of the curved leading edge of the sheet. Consequently, the effective area formed by the nozzles 49 and acting on the curved leading edge of the sheet is significantly larger than the effective area of ​​the suction belt acting on the curved leading edge of the sheet. The larger the respective effective area, the better the bending resistance forces inherent in the curvature of the sheet can be overcome.Since the effect of the suction flow of the respective suction belt is height-dependent and decreases with increasing height, i.e., the distance between the suction belt and the sheet to be transported, the nozzles 49, designed as Venturi nozzles, can cause the curved leading edge of the sheet to be drawn forward until it enters the effective range of the suction flow of the respective suction belt. Once the curved leading edge of the sheet is sufficiently deep within the effective range of the suction flow of the respective suction belt due to the action of the nozzles 49, this suction flow may be strong enough to draw the curved leading edge of the sheet over the remaining height and onto the suction belt, thus creating the frictional or force-fit connection necessary for precise positioning and transport of the sheet.In a preferred embodiment, the control unit 71 is thus designed such that it first supplies the nozzles 49 with compressed air, and only afterwards, i.e. with a time delay, does a suction force exerted on the sheet by the at least one transfer belt 44 designed as a suction belt begin to act. Reference symbol list 01 Bow feeder 02 first stack 03 Suction head 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 front mark 37 blowboxes 38 bulkhead 39 Opening 40 - 41 Suction chamber 42 Guidance device 43 Lifting nozzle 44 Transfer Volume 45 - 46 first bend 47 second bend 48 ski jump ribbon 49 nozzle 50 - 51 catching blowers 52 switching range 53 Suction bore 54 Feed belt 55 - 56 Brake band 57 Suction roller 58 Catching device 59 Drive 60 - 61 Piston rod 62 crank 63 couplings 64 lane 65 - 66 Stop surface 67 Opening 68 floor chamber 69 Storage room 70 - 71 Control unit 72 Suction device 73 Supply line 74-stroke valve 75 - 76 Deflection roller 77 sheets 78 Discontinuity point 79 Profile element 80 - 81 pneumatic cylinders 82 cylinder pistons 83 End position damping element 84 End position damping element 85 - 86 first pneumatic switching valve 87 second pneumatic switching valve 88 pressure reducers 89 pressure reducers 90 - 91 Throttle valve 92 Throttle valve 93 Compressed air source 94 Rand 95 - 96 Supply line 97 Control valve a acceleration F piston force i Translation ratio M Center line t time T Transport direction v speed z parking path A51 distance B19 width D62 pivot point E1 Endpoint E2 Endpoint E19 funding level G61 Joint point G62 joint point G63 Straight G64 Straight

Claims

Machine arrangement with several processing stations, each processing sheets, wherein these processing stations are arranged one behind the other in the transport direction (T) of the sheets, wherein at least one of these processing stations has a transport device (18) that transports the sheets lying down along a linear transport path, wherein this transport device (18) is designed to transport individual sheets in a sequence immediately following one another, spaced apart from each other by a gap, wherein a suction belt table (19) is arranged downstream of this transport device (18) that transports the sheets lying down along a linear transport path, characterized in that the transport device (18) arranged upstream of the suction belt table (19), which transports the sheets lying down along a linear transport path,The suction belt table (19) is designed to transport individual sheets in a sequence, each with a sheet gap measuring approximately 20 mm, wherein the suction belt table has a catching device (58) with a catching position assumed as a result of actuation for individual sheets in a sequence, wherein the catching device (58) in its catching position catches and stacks sheets supplied to the suction belt table (19) by the transport device (18), which transports the sheets lying down along a linear transport path and is located upstream of the suction belt table (19), before each transfer to a transport device downstream of the suction belt table (19), wherein a control unit (71) is provided, wherein this control unit (71) actuates the catching device (58) depending on a fault that has occurred in a processing station downstream of the suction belt table (19),that the catching device (58) assumes its catching position, wherein in the catching position at least one stop surface (66) of the catching device (58) is arranged to penetrate the arch gap. Machine arrangement according to claim 1, characterized in that the transport device (18) arranged upstream of the suction belt table (19), which transports the sheets lying down along a linear transport route, belongs to a dryer (17) or to a cooling section or to another processing station. Machine arrangement according to claim 2, characterized in that the dryer (17) is arranged downstream of a processing station designed as a non-impact printing device (13). Machine arrangement according to claim 1 or 2 or 3, characterized in that the suction belt table (19) is arranged upstream of a processing station designed as a coating device (22), in particular as a painting device. Machine arrangement according to claim 4, characterized in that the coating device (22) has a transport cylinder (23) as a transport device for sheets to be transported, wherein a printing cylinder (24) is arranged to interact with this transport cylinder (23), wherein an application roller (26) is attached to or at least attachable to this printing cylinder (24), wherein at least one doctor blade (27) or a chambered doctor blade system (27) extends in the axial direction of the application roller (26). Machine arrangement according to claim 4 or 5, characterized in that a vibrating gripper (21) and a transfer drum (33) cooperating with the vibrating gripper (21) are arranged between the suction belt table (19) and the coating device (22), wherein the transfer drum (33) transfers the sheets to the coating device (22). Machine arrangement according to claim 1 or 2 or 3 or 4 or 5 or 6, characterized in that this machine arrangement is designed to transport the sheets at a transport speed of several thousand sheets per hour, in particular of about 10,000 sheets per hour.

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