Sheet transport device and method for transporting sheets by means of a sheet transport device

Abstract

Sheet transport device comprising a revolving gripper carriage (1) with an air guide element (3) which is movable along a sheet guide element (7) connected to an air supply device, wherein the sheet guide element (7) contains blow air openings (10), wherein the blow air openings (10) arranged in the sheet guiding element (7) generate a blow air flow (12) with at least one component (13) in the sheet conveying direction (BFR) and wherein means for adjusting this blow air flow (12) are provided, wherein the flow around the gripper carriage is adjusted by changing the blow air flow (12), wherein the air guiding element (3) has a jamming nose (4) located in the region of the gripper carriage half facing the sheet guiding element (7), wherein the part of the air guiding element (3) facing away from the sheet guiding element (7) and the part facing the sheet guiding element (7) are arranged at an acute angle to each other on the accumulation nose (4) and wherein the blowing air exiting from the blowing air openings (10) is adjustable such that it flows out at a speed increased compared to the sheet conveying speed.

Description

[0001] The invention relates to a sheet transport device comprising a revolving gripper carriage with an air guide element and a method for transporting sheets by means of a sheet transport device.

[0002] In the deliveries of sheet-fed printing presses, the airflow around a gripper carriage causes considerable problems at high speeds. The frontmost point of the gripper carriage, the so-called stagnation nose for profiles, divides the air masses, so that the air volume ◯ is directed below the dam nose under the impact track and ◯ is guided over this impact path above the dam nose.

[0003] Generally, the air gap is higher than the impact path, so that more air is trapped beneath the arch than can be accommodated under equalized pressure. As a result, the arch is lifted out.

[0004] The upper airflow breaks off at the edge of the gripper carriage and creates a turbulent low-pressure area, which lifts the sheet.

[0005] The problem of a gripper carriage with air flow also leads to a fluttering movement of the sheet being transported, which subsequently strikes machine elements, which in turn leads to undesirable smearing. Various prior art approaches attempt to solve this problem.

[0006] DE 33 08 907 A1 and DE 196 24 136 B4 describe various front spoilers for gripper carriages designed to prevent air from flowing under the sheet being transported. The disadvantages of these solutions are that an air deflector or sealing nose poses a risk of collision, and a brush strip is subject to constant abrasion, which negatively impacts the moving components in the delivery. Optimal sheet guidance is therefore not possible.

[0007] EP 0 949 177 B1 and JP 6 - 270392 A disclose a front spoiler for gripper carriages that can be moved with the gripper fingers. The disadvantage of this solution is that the risk of collision with sheet guiding elements cannot be completely eliminated, and insufficient undercurrent of the sheet being transported does not allow for optimized sheet guidance. Influencing the sheet guidance, especially in the important convex and concave sheet guiding areas, is not possible at all.

[0008] DE 198 47 399 A1 discloses a front spoiler that can be controlled independently of the movement of the gripper fingers, and DD-PS 160 435 discloses a controllable rear spoiler for gripper carriages. The disadvantages of these solutions are that the moving components require increased manufacturing and maintenance costs and that they increase the mass of the gripper carriage, which has a detrimental effect at higher speeds, especially in deflection areas.

[0009] DE 33 08 844 A1 discloses a gripper carriage with a teardrop-shaped cross-section that offers improved aerodynamic performance. The disadvantage of this solution is that the symmetrical teardrop-shaped cross-section creates excessive undercurrent for the gripper carriage, causing the sheet to flutter. Adjustment options for the sheet guidance are not provided.

[0010] JP 2003 - 176057 A discloses a gripper carriage with air guiding elements that have an almost completely drop-shaped cross-section. Here, the air can flow laminarly above and below the sheet to be transported. A disadvantage of this solution is that the air guiding elements projecting above the sheet prevent drying and powder application to the underlying sheet areas. Furthermore, no sheet guiding elements are disclosed.

[0011] EP 0 252 602 A1 discloses a gripper carriage with a spoiler for air guidance. The disadvantage of this solution is that only the air flowing directly over the gripper carriage is affected. An interaction with a sheet guide element is not disclosed.

[0012] DE 102 55 948 B3 already discloses an advantageous grabber carriage featuring an at least approximately teardrop-shaped cross-section and a rear spoiler. The disadvantage of this solution is that the sloping cross-section reduces the stability of the grabber carriage. The high dam nose also causes excessive undercurrents around the grabber carriage.

[0013] From DE 36 22 515 A1, it is known that an air stream directed by a guide plate of a gripper carriage onto a sheet guide element can be absorbed through suction openings in the sheet guide element. A suction effect is also achieved when the sheet guide element is subjected to blast air. The disadvantage of this solution is that the shape of the guide plate directs the entire air stream beneath the sheet being transported, resulting in significant sheet movement. This prevents floating guidance. Adjustment to different printing conditions is also not possible.

[0014] Furthermore, sheet guide elements with an adjustable blast air supply are also known from the prior art (DE 44 27 448 A1). These sheet guide elements direct the blast air directly onto the sheet to support and guide the sheet and influence its position. A deliberately selected feedback effect of the blast air on the airflow around the gripper carriage is not yet known. To date, satisfactory results in sheet transport under all possible printing conditions have not been achieved.

[0015] DE 10 2010 001 806 B4 shows a delivery of a sheet-processing machine with a gripper carriage movable along a sheet guide, wherein an air guide element spans a cross member in the area facing away from the sheet guide in such a way that the air guide element and / or the cross member form a sharp separation edge for the air flow.

[0016] The invention is therefore based on the object of creating an improved sheet transport device and an improved method for transporting sheets, which allow an optimization of the sheet guidance.

[0017] According to the invention, this object is achieved by a device having the features of the independent device claim and a method having the features of the independent method claim. Advantageous embodiments emerge from the subclaims, the description, and the drawings.

[0018] The invention has the advantage that the airflow around the gripper carriage is improved in such a way that it no longer has any harmful effects on the sheet guidance and can simultaneously be used for sheet guidance.

[0019] The essence of the invention is to adjust the blast air flow directed toward the underside of the sheet in the sheet conveying direction in such a way that the partial air flow flowing under the gripper carriage is limited, thus ultimately adjusting the air flow around the gripper carriage. The air flow around the gripper carriage can thus be optimized and adjusted and modified as required.

[0020] Preferred embodiments of the invention have the advantage that sheet guidance is achieved without significant deviation from the design guidelines, and the sheet can be moved in the best possible flatness over the sheet guide elements. The particularly steady position of the sheet prevents smearing on the sheet guide elements and ensures a homogeneous powder distribution on the sheet. Another advantage is that the blast air used from above has no effect on the good guidance quality, which improves powdering and drying.

[0021] According to the invention, the airflow around the gripper carriage is utilized for sheet travel in such a way that a homogeneous air flow balance is achieved when flowing around the gripper carriage. Air flow balance means the distribution of the air flow around the gripper carriage with the goal of achieving approximately the same air flow volumes above and below the impact path after flowing around the gripper carriage, with balanced pressure conditions, as they were distributed before the gripper carriage.

[0022] According to the invention, the gripper carriage contains a dam nose which acts as a defined air divider for the air flowing towards the gripper carriage. For this purpose, the air guiding element is specifically designed asymmetrically, deviating from the droplet-shaped form. The dam nose is arranged in the part of the gripper carriage facing the sheet guiding element, so that the partial air quantity flowing under the gripper carriage is limited. The dam nose is also at a defined distance from the sheet guiding element, which enables optimized air distribution across the entire sheet conveying section. The dam nose is arranged at such a distance from the sheet guiding element that contact with the sheet guiding element is excluded, even on convex and concave sheet guiding sections. This improves the air flow in all sheet conveying areas without moving components. Further preferably, the air guiding element is designed to be many times thinner-walled than a cross member of the gripper carriage which ensures stability.For the air guide element, a material with a lower density than that of the traverse is preferably used in order to minimize the mass of the gripper carriage.

[0023] The lower-lying air dam also secures the partial airflow flowing over the gripper carriage, which is then directed by a rear spoiler into the space behind the gripper carriage with lower air pressure. This partial airflow is necessary to create pressure equalization behind the gripper carriage. The rear spoiler is preferably designed to run parallel to the sheet conveying direction in some areas so that the partial airflow deflected upwards by the air guide element is captured and calmed. This reduces turbulence. The section of the rear spoiler adjacent to the sheet conveying direction is angled to the sheet conveying direction so that the relatively laminar flowing partial airflow is directed into the area behind the gripper carriage.

[0024] According to the invention, the precise air distribution around the gripper carriage is achieved by the blast air openings in the sheet guide elements, which, in conjunction with the gripper carriage moving over them, influence the air flow. The blast air flowing through the blast air openings is adjustable in such a way that it influences the partial air flow beneath the gripper carriage. This ultimately allows the air flow beneath the sheet to be adjusted, allowing the sheet position to be adjusted during sheet transport. This adjustability to printing conditions includes, in particular, settings for the substrates used, the current press speed, the applied printing or varnish quantities, and other substrate properties, such as sheet widths, grammage, surface properties, and more.

[0025] The blast air openings are preferably designed such that they expel a blast air stream exclusively with a component in the sheet conveying direction and a component toward the respective lateral sheet edge in the corresponding resulting blast air direction. In particular, no blast air is discharged with a component counter to the sheet conveying direction. The blast air openings are designed as blast air nozzles and are preferably shaped as Venturi nozzles. A blast air stream is expelled from the Venturi nozzles at an angle of between 30° and 75°, preferably between 60° and 65°, to the sheet conveying direction. Further preferably, the blast air is adjustable along the sheet conveying path, for example, can be reduced upstream of the sheet brake. Adjustment in specific areas across the sheet width is also provided.If alternative air blast openings are used, the component of the air blast directed in the sheet conveying direction can be adjusted using a variable air blast direction. Movable nozzles, for example, can be used here.

[0026] In addition to this change in the component of the blast air flow exiting in the sheet conveying direction, other means for adjusting the blast air flow can also be used. The means for adjusting the blast air flow preferably comprises adjusting the pressure supplied to the sheet guide element via the control of the compressed air generator or intermediate valves. Furthermore, the cross-section of one or more blast air openings can also be changed, or areas with blast air openings can be deactivated. Alternatively, the means can also include a bypass line that can be activated or deactivated.

[0027] According to one embodiment of the invention, the gripper carriage is constructed in at least two parts, with a cross member providing stability and an air guiding element associated therewith being provided. The gripper carriage further comprises a rear spoiler which improves air guidance and is attached to the cross member or the air guiding element via connecting webs. The cross member preferably consists of a profile arranged in the rear gripper carriage area, oriented substantially perpendicular to the sheet conveying direction, and a profile connected to this profile and further away from the sheet guiding element, oriented substantially in the sheet conveying direction. Both profile parts together form a T-profile. This profile increases the flexural rigidity. The maximum gripper carriage height is formed in the area of ​​the rear gripper carriage on the cross member. The air guiding element is guided from the retaining nose with a continuously increasing cross-section up to the maximum gripper carriage height.The air guide element can be detachably connected to the cross member and, in a further development of the invention, is attached to the cross member so that it can be exchanged for other air guide elements.

[0028] The invention will be explained below by way of example. The accompanying drawings illustrate this schematically: Fig. 1: Embodiment of a gripper carriage and further development of a gripper carriage for transporting sheets along a sheet guide plate in side view; Fig. 2: Perspective view of a gripper carriage and a sheet guide plate containing venturi nozzles; Fig. 3: Top view of a gripper carriage guided over a sheet guide plate with Venturi nozzles; Fig. 4: Further development of a sheet guide plate with Venturi nozzles and a central nozzle row.

[0029] The Fig. 1 shows two gripper carriages 1 moving in a sheet conveying direction BFR on a sheet conveying path along a sheet guide element. The gripper carriages 1 are arranged in the delivery (not shown in detail) of a sheet-processing machine, in particular a sheet-fed printing press or sheet-fed offset rotary printing press, and transport sheets 8 from a last cylinder of the machine to a delivery stack arranged in the delivery. The gripper carriages 1 are guided circumferentially by chains guided laterally on the delivery frame and have movable gripper fingers for gripping the sheets 8 at an edge.

[0030] Each gripper carriage 1 contains a cross member 2 extending across the machine width between the chains, which ensures the stability of the gripper carriage 1. This cross member 2 is designed as a T-profile and comprises a first partial profile aligned perpendicular to the sheet conveying direction BFR, and a second partial profile spaced further from the sheet guide element, which has a cross-section extending approximately in the sheet conveying direction BFR. This configuration ensures high bending strength. Furthermore, gripper stops are assigned to the cross member 2, which interact with the movably mounted gripper fingers. The gripper fingers are spaced apart from one another and fixedly assigned to a gripper shaft, which is controlled by a roller lever.

[0031] A gripper carriage 1 grips each sheet 8 at its leading edge and takes it over to an upstream sheet conveying system, for example a printing cylinder or drum of the last printing, coating, drying, or finishing unit. The sheet 8 is transported along the sheet conveying path. Sheet guiding elements, which here are designed as sheet guide plates 7, are arranged below the sheet conveying path. Blast air openings are integrated into the sheet guide plates 7. The blast air openings are designed here as blast air nozzles. The blast air openings are connected to a compressed air supply (not shown). The compressed air supply supplies the blast air openings with controllable or adjustable compressed air. The blast air exits the blast air openings below the sheet 8 to be transported.

[0032] In the Fig. 1 shows an embodiment of a gripper carriage 1 having an air guide element and a rear spoiler 5. The air guide element is designed as an air guide profile 3 or air guide shield for actively creating a defined air flow around the gripper carriage 1. The air guide profile 3 extends across the entire width of the gripper carriage and enables the most laminar flow of the air to be guided. The air guide profile 3 is arranged upstream of the cross member 2 and has a dam 4, which divides the air flowing towards the gripper carriage 1 in the air flow direction 9 into a partial air volume flowing over the gripper carriage 1 and a partial air volume flowing under the gripper carriage 1. The dam 4 is arranged at a defined distance from the sheet guide track such that the partial air volume flowing under the gripper carriage 1 is limited from the outset. The majority of the air volume is therefore directed upwards over the gripper carriage 1.The air guide profile 3 is designed to be at least approximately parallel to the sheet guide element on the side facing the sheet guide element and has recesses for the gripper fingers. On the side facing away from the sheet guide element, the air guide profile 3 is designed to rise continuously from the retaining nose 4 with an aerodynamically closed surface. The air guide profile 3 has a cross-section that continuously rises up to the cross member 2 and is firmly or detachably connected to the cross member 2 in the area of ​​the maximum gripper carriage height.

[0033] Further in the Fig. 1, the trailing gripper carriage 1 is shown as a further development with an additional front spoiler 6. This front spoiler 6 reduces the distance formed to the sheet guide element, so that the partial air flow flowing in below the gripper carriage 1 is further reduced compared to the retaining nose 4. This results in a smaller underflow of the sheet 8, so that less blow air is required from the blow air openings of the sheet guide elements to set the ideal levitation for the sheet 8. This front spoiler 6 is preferably made of elastic material and / or spring-mounted to prevent sheet damage in the area of ​​the sheet brake in the event of sheet contact with a preceding sheet 8 that is to be braked.

[0034] Both the gripper carriage 1 shown as the first embodiment and the gripper carriage 1 shown as a further development have a rear spoiler 5 arranged at a distance from the air guide profile 3, by means of which the partial air flow flowing over the gripper carriage 1 is directed into the area behind the respective gripper carriage 1. In this case, the cross-section of the gripper carriage 1 and thus the gripper carriage height are not reduced. The rear spoiler 5 preferably has a region parallel to the sheet conveying direction BFR and an adjoining region angled at an obtuse angle to the sheet conveying direction BFR. The obtuse angle between the two regions below the rear spoiler 5 can, for example, be in a range of 100° to 150°, in particular 135°. The transition between the regions can be rounded.

[0035] The gripper carriages 1 shown each have an air guide profile 3 with a stagnation nose 4, wherein this stagnation nose 4 is assigned to the gripper carriage half facing the sheet guide plate 7, but preferably to the gripper carriage quarter facing the sheet guide plate 7. The air guide profile 3 is preferably formed in one piece, wherein the parts of the air guide profile 3 arranged above and below the stagnation nose 4 are arranged at an acute angle to one another at the stagnation nose 4. The stagnation nose 4, as an edge in the air guide profile 3, represents a defined air divider. The air guide profile 3 thus has an asymmetrical cross-section that deviates from the drop-shaped cross-section. At a drop-shaped cross-section, the stagnation point of the air can move, so that no reproducible partial air flow can be achieved below the printing substrate.

[0036] The Fig. Figure 2 shows the gripper carriage 1 guided over the sheet guide plate 7 in the sheet conveying direction BFR. The sheet guide plate 7 shows the blast air openings designed as Venturi nozzles 10. Furthermore, the resulting air flow direction 12 of the blast air exiting the Venturi nozzles 10 is shown, with a blast air component directed partially in the sheet conveying direction BFR. This partial air flow direction 13 from the Venturi nozzles 10 in the sheet conveying direction BFR counteracts the partial air flow flowing in below the retaining nose 4 and displaces it depending on the existing blast air setting.

[0037] The Fig. Figure 3 shows a top view of the gripper carriage 1 guided over the sheet guide plate 7. The sheet guide plate 7 contains the Venturi nozzles 10, which generate a fan of blown air directed outwards towards the sheet edge. The resulting air flow directions 12 from the Venturi nozzles 10 each contain a partial air flow direction 13 in the sheet conveying direction BFR and a partial air flow direction 14 transverse to the sheet conveying direction BFR. The partial air flow direction 13 in the sheet conveying direction BFR counteracts the partial air flow flowing under the gripper carriage 1. This component is adjusted in such a way that the flow around the gripper carriage improves and thus an optimized levitation of the sheets 8 is achieved. The resulting air flow direction 12 exits the Venturi nozzles 10 at an angle between 30° and 75°, in particular exactly 63°, to the sheet conveying direction BFR.The proportion of blown air exiting the Venturi nozzles 10 in the sheet conveying direction BFR is preferably adjusted such that it exits at a speed that is higher than the sheet conveying speed.

[0038] The Fig.4 shows a preferred development of a sheet guide plate 7 with a central row of nozzles 11 arranged centrally to the sheet guide plate 7 and oriented in the sheet conveying direction BFR. This central row of nozzles 11 directs blown air to the underside of the sheet independently of the other blown air openings in order to prevent evacuation of the central region by the remaining outwardly directed blown air flow. This blown air emerging from the central row of nozzles 11 supports the sheet 8 in the central region. Blown air emerges from the central row of nozzles 11 vertically and / or in the sheet conveying direction BFR. Venturi and / or other blown air nozzles can be used in combination. Preferably, the blown air of the central row of nozzles 11 is separately adjustable or controllable so that this additional setting can also be used to optimize the airflow around the gripper carriage. An improvement in sheet guidance is thus further provided.In the illustrated development, it is additionally provided to arrange individual nozzles or, specifically, a row of nozzles at a different angle in the sheet guide plate 7. Here, the blast air openings, arranged as the penultimate row in the sheet conveying direction BFR, are also oriented toward the sheet edge at an angle of between 20° and 30°, in particular 27°, to the sheet conveying direction BFR. The other Venturi nozzles 10 are arranged at an angle of 60°, but can preferably be arranged at an angle of approximately 63°.

[0039] How it works: According to the invention, the air flow balance during the flow around the gripper carriage 1 is achieved by a low-set dam nose 4, co-directed Venturi nozzles 10, which reduce the underflow of the gripper carriage 1, and a rear spoiler 5. The rear spoiler 5 directs the stalling flow across the front upper surface of the sheet, thus minimizing the height and extent of the negative pressure area. In a further development, the underflow of the gripper carriage 1 is further reduced by an additional front spoiler 6, allowing for a hovering guide with reduced blowing air.

[0040] The blast air flow can be adjusted and re-adjusted in sections in the sheet feed direction (BFR) and / or across the press width, so that the floating guidance of the sheets can always be optimized. The blast air flow in the sheet feed direction (BFR) from the blast air openings of the sheet guide elements is preferably reduced for lighter grammage substrates and increased for heavier grammage substrates. Furthermore, the blast air flow can be adjusted depending on the press speed, etc. Corresponding parameter values ​​are stored for reuse for specific jobs or to be used as a default setting. If sensors are used to control the sheet guidance, the floating guidance adjustment process can be further automated. List of reference symbols used 1 gripper trolley 2 traverses 3 Air guide profile 4 Waterlogging nose 5 rear spoiler 6 front spoiler 7 sheet guide plate 8 sheets 9 Air flow direction 10 Venturi nozzles 11 middle nozzle row 12 resulting air flow direction from Venturi nozzles 13 Proportional air flow direction from Venturi nozzles in sheet conveying direction 14 proportional air flow direction from Venturi nozzles transverse to the sheet conveying direction BFR sheet feed direction

Claims

[1] Sheet transport device comprising a revolving gripper carriage (1) with an air guide element (3) which is movable along a sheet guide element (7) connected to an air supply device, wherein the sheet guide element (7) contains blow air openings (10), wherein the blow air openings (10) arranged in the sheet guiding element (7) generate a blow air flow (12) with at least one component (13) in the sheet conveying direction (BFR) and wherein means for adjusting this blow air flow (12) are provided, wherein the flow around the gripper carriage is adjusted by changing the blow air flow (12), wherein the air guiding element (3) has a jamming nose (4) located in the region of the gripper carriage half facing the sheet guiding element (7), wherein the part of the air guiding element (3) facing away from the sheet guiding element (7) and the part facing the sheet guiding element (7) are arranged at an acute angle to each other on the accumulation nose (4) and wherein the blowing air exiting from the blowing air openings (10) is adjustable such that it flows out at a speed increased compared to the sheet conveying speed. [2] Device according to claim 1, characterized by that the blowing air stream (12) exits at an angle between 30° and 75° or between 60° and 65° to the sheet conveying direction (BFR) towards the sheet edge. [3] Device according to claim 1 or 2, characterized by that the blow air openings (10) are designed as Venturi nozzles (10). [4] Device according to claim 1, 2 or 3, characterized by that the blowing air flow (12) can be adjusted by the means depending on parameters. [5] Device according to claim 1, 2, 3 or 4, characterized bythat the blowing air flow (12) can be adjusted by the means depending on the sheet thickness, the sheet format and / or the machine speed. [6] Device according to at least one of the preceding claims, characterized by that the air guiding element (3) of the gripper carriage (1) has a continuously increasing cross-section in the region of the gripper carriage half facing away from the sheet guiding element (7). [7] Device according to at least one of the preceding claims, characterized by that the gripper carriage (1) has a rear spoiler (5) spaced from the air guiding element (3) which is arranged at an angle to the sheet conveying direction (BFR) at least in some areas. [8] Method for transporting sheets (8) by means of a sheet transport device, wherein the sheet transport device contains a gripper carriage (1) with an air guiding element (3) and the gripper carriage (1) is moved along a sheet guiding element (7) connected to an air supply device and the sheet guiding element (7) contains blowing air openings (10), wherein a partial air quantity is guided between the gripper carriage (1) and the sheet guide element (7) by the air guide element (3) during the movement of the gripper carriage (1) and wherein blown air is generated via the blown air openings (10) in such a way that the flow around the gripper carriage and thus the sheet guidance is adjusted, wherein the blowing air openings (10) are designed as Venturi nozzles (10) and wherein the proportion of blowing air exiting the Venturi nozzles (10) and directed in the sheet conveying direction (BFR) is adjusted such that it exits at a speed which is higher than the sheet conveying speed.

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