Sheet feeder and method for operating a sheet feeder

Abstract

Sheet feeder (02) for a sheet processing machine (01) with a sheet separator (18) comprising a separating suction cup (19), wherein the separating suction cups (19) are arranged to be vertically displaceable, wherein at least one first sheet guide element (31) forms an at least approximately horizontal guide surface in a plane of the raised separating suction cups (19) and wherein at least one second sheet guide element (32) is provided to form a stabilizing deformation of a raised sheet (33) deviating from the plane, characterized in that one or more second sheet guide elements (32) extending in the transport direction (T) of the sheets (33) are designed with a curvature facing the raised sheet (33).

Description

[0001] The invention relates to a sheet feeder for a sheet processing machine with a sheet separator comprising a separating suction cup and a method for operating a sheet feeder of a sheet processing machine with a sheet separator comprising a separating suction cup.

[0002] Sheetfed printing presses often experience problems with sheet separation and flaking at the sheet feeder as the speed increases. This results in inaccurate sheet placement on the feeder table (suction belt table) and interruptions in the sheet feed due to skewed sheets and misaligned sheets in the sheet feeder. Productivity decreases.

[0003] The precise separation of thinner materials, such as paper under 100 g / m², is usually the most challenging. 2However, this is also difficult with statically charged materials at increasing speeds. The sheets are not sufficiently lifted and separated from the stack by the separating blower. Therefore, the sheet does not move precisely towards the transport roller (infeed roller) via the suction cups. The sheet being transported partially adheres to the stack and, due to the forward movement, forms waves in the front area (towards the leading edge), which cause sheet shortening and, subsequently, an inaccurate sheet split.

[0004] Up to now, sheet singulation has been ensured as effectively as possible using large amounts of separating air and special nozzles. Blowing elements on the stack edges support this process. However, depending on the material and the speed, singulation problems still occur.

[0005] One possibility is the use of additional high-pressure separating blowers. However, the system of blowing compressed air from the trailing edge of the stack to the leading edge has its limitations, as it consumes an extremely large amount of air and the fanned-out sheets at the trailing edge are attracted to each other due to the high air velocity. Additionally, the weight of the sheets already running under the indexing roller hinders the separation of the sheet being lifted. Therefore, the air jet never reliably penetrates the lifted sheet all the way to the leading edge.

[0006] From DE 35 31 889 A1, a top-discharging separating and feeding device for the successive separation and transport of sheet-like material is known, comprising a vacuum device positioned above the leading edge of the stack to apply a vacuum force sufficient to capture the uppermost sheet-like material from the stack, and a wave device to corrugate the sheet-like material as it is fed from the stack. A wave rail is attached to or formed on the underside of the vacuum chamber and causes sheets received by the vacuum chamber to bend during corrugation, so that if a second sheet is still adhering to the sheet already received by the vacuum chamber, the corrugation causes the second sheet to detach and fall back.

[0007] From DE 199 17 405 A1 a method and a device for singulating flexible flat objects are known, wherein the objects are lifted from a stack and the lifted objects are transported in a transport direction and wherein each object is aligned into a target position while it is in a partially lifted state.

[0008] From WO 2008 / 028498 A1, a handling device and a method for singulating and feeding sheet blanks are known, wherein a sheet blank is grasped at the rear stacking edge by push elements in an upper receiving plane and advanced, and wherein the sheet blank sucked in by suction elements is stripped from the suction elements and fed to a receiving device.

[0009] DE 198 32 847 A1 discloses a method and a device for singulating flexible, flat objects, wherein an adhesive effect is built up that progresses in the transport direction and attracts the object in order to lift it off.

[0010] JP 2009073631 A shows a sheet feeder of a sheet-fed printing machine and a sheet-fed printing machine, wherein a first sheet guide is arranged on the upper side of a sheet conveying path and is attached to the lower side of a separating device, wherein the base end of a second sheet guide is connected to the first sheet guide in a vertically rotatable manner by a connecting shaft and wherein the tip of the second sheet guide extends to one side of a sheet conveying device.

[0011] The invention is based on the objective of creating an alternative sheet feeder or an alternative method for operating a sheet feeder. In particular, the productivity of the sheet feeder or the sheet-processing machine is to be increased.

[0012] The problem is solved according to the invention by the features of an independent claim.

[0013] The advantages achievable with the invention consist in particular of providing an alternative sheet feeder or an alternative method for operating a sheet feeder. In particular, the productivity of the sheet feeder or the sheet-processing machine is increased. A corresponding sheet-processing machine, especially a printing press, with such a sheet feeder is also provided.

[0014] In particular, a special sheet guide, preferably in a wave-like shape, can stabilize the lifted or to-be-separated sheet in the transport direction, preventing it from shortening and ensuring it is conveyed precisely to the feeder table, especially to the infeed roller with indexing rollers. A wave-like deformation of the sheet (analogous to corrugated cardboard packaging) increases sheet stability. This results in relatively high stiffness, even with thin or lightweight materials.

[0015] Preferably, the sheet to be lifted and separated is separated using assisted airflow, whereby the lifted and deformed sheet can be transported more easily in the transport direction due to the increased stiffness. Several such deformations, such as waves, can also be created in the lifted sheet, thereby increasing its stiffness, similar to corrugated sheet metal. The deformation, in particular the formation of waves, of the lifted sheet occurs especially in the area of ​​its trailing edge, which has been lifted by suction cups, and can extend towards its leading edge or run in the same direction. Furthermore, the sheet guide could additionally be equipped with blowing openings, for example, air-jet nozzles, to hold and guide the lifted sheet at the guide elements, analogous to an air-assisted sheet guide plate.In this process, a raised bow can be given a bow direction through the blowing openings, for example high-pressure nozzles, and preferably glide along the bow guide on a cushion of air while suspended.

[0016] Advantageously, an easily adjustable sheet feeder is provided, which ensures reliable sheet feeding despite varying paper and stack qualities, preferably at all speeds of a sheetfed press. Incorrect settings can thus be compensated for. In particular, this can increase the machine's productivity.

[0017] Exemplary embodiments of the invention are shown in the drawings and are described in more detail below.

[0018] They show: Fig. 1 a sheetfed offset printing press with a sheet feeder; Fig. 2 an enlarged view of a bow feeder in side view; Fig. 3 An enlarged view of a bow anchor in front view.

[0019] The Fig. Figure 1 shows a machine, for example a printing press 01, in particular a sheet-fed printing press, specifically a sheet-fed offset rotary printing press, preferably in a modular or in-line configuration. The printing press 01 is specifically designed and equipped for printing on sheet-shaped substrates, for example, paper. Preferably, the printing press 01 includes, in addition to a sheet feeder 02 for feeding sheets to be processed, particularly as a stack, a sheet feeder 03, one or more printing units 04, for example, a perfecting unit 05, optionally one or more coating units 06, and a sheet delivery unit 07 for depositing the processed sheets, particularly into a stack. Alternatively, the printing press 01 can also have any other number of units or any special equipment and / or be designed as a perfecting press.

[0020] For processing, sheets are taken from a fed stack in the sheet feeder 02 and transported in the direction T towards the sheet feeder 03. In particular, a sheet-shingle stream of partially overlapping sheets is formed before the sheets are individually accelerated in the sheet feeder 03 and fed to the first printing unit 04 at machine speed. In the printing units 04, and optionally the perfecting unit 05 and the coating unit 06, the sheets are clamped at the leading edge by sheet guide cylinders and transferred by gripper engagement to the sheet delivery unit 07, where they are processed, in particular printed and / or coated. The sheet delivery unit 07 preferably contains a chain conveyor system that takes the processed sheets, in particular from a sheet guide cylinder of the last coating unit 06, and transports them to a stack for placement.

[0021] In the printing units 04, impression cylinders 08 are arranged, which clamp the leading edges of the sheets by means of gripper systems and transport them during their rotation. In each printing unit 04, the impression cylinder 08 forms a printing gap with an adjacent blanket cylinder 09, through which the sheets are transported. A blanket cylinder 09 carries a rubber blanket and is functionally connected to a plate cylinder 10. A plate cylinder 10 carries a printing plate, which is inked with printing ink during a printing process by inking rollers (not shown) of an inking unit. The machine, in particular printing press 01, can be operated via a control station 11, which provides access to the machine control system.

[0022] The Fig. Figure 2 shows an enlarged side view of a sheet feeder 02 of a sheet-processing machine, for example, the printing press 01 described above. The sheet feeder 02 has a frame 12 and a stacking lifting device held by the frame 12, which raises or lowers a stacking support plate 14, in particular by means of lifting chains 13. A pallet 15 is preferably arranged on the stacking support plate 14, on which a stack 16 of sheets to be processed, individually stacked on top of each other, is arranged. The stack of sheets 16 can be placed onto the stacking support plate 14 by means of the pallet 15. The stack of sheets 16 is generally aligned against a front stop 17 with respect to its leading edge, which points in the transport direction T. The sheet feeder 02 could also be equipped with a non-stop device for the uninterrupted feeding of stacks of sheets 16 on non-stop system pallets.

[0023] The sheet feeder 02 comprises a sheet separator 18, held in particular by the upper frame 12, for the machine-cycle singulation and transport of the uppermost sheets of the sheet stack 16 in the transport direction T. The sheet separator 18 is associated with separating suction cups 19 (also called lifting suction cups) and transport suction cups 20 (also called trailing suction cups) for the purpose of singulation and transport of the singulated sheets in the transport direction T. The separating suction cups 19 are mounted so as to be vertically movable and are positioned between a lowered position, in which the uppermost sheet of the sheet stack 16 is in contact with it, and an upper position, in which the separating suction cups 19 lie in a horizontal plane with the transport suction cups 20.

[0024] The separating suction cups 19 preferably each comprise a downwardly open suction cup made of a flexible plastic, open towards the sheet stack 16, which are connected at their upper end to a common vacuum source. The vacuum must be sufficient to ensure that the suction cups adhere securely to the sheet to be lifted from the sheet stack 16, but it must not be so strong as to pull the sheet into the suction cup and thereby deform it. If not all suction cups of the separating suction cups 19 are in contact with a sheet to be lifted, the airflow over an uncovered suction cup can prevent the vacuum required for lifting from being reached in the other suction cups. For reliable lifting of a sheet, it is therefore important that all separating suction cups 19 come into contact with it simultaneously. For this purpose, each separating suction cup 19 can be movable relative to the sheet separator 18 by means of its own drive, in particular a linear actuator.Preferably, a common frame in which all separating suction cups 19 are held is movable relative to the sheet separator 18 by means of a fast, powerful main actuator to suction the sheet from the sheet stack 16 and lift it along the trailing edge. To compensate for unevenness on the top of the sheet stack 16 and to ensure simultaneous contact of all separating suction cups 19 with the sheet to be lifted, the separating suction cups 19 can be adjustable relative to the frame by means of auxiliary actuators, the latter being slower and having a smaller stroke than the main actuator.

[0025] Furthermore, the sheet feeder 02, in particular the sheet separator 18, preferably includes at least one probe foot 21, which is movable, in particular, between a holding position pressing against the rear edge of the sheet stack 16 and a rest position located outside the stack's footprint. In the rest position, the probe foot 21 can be raised relative to the holding position and moved behind the rear edge of the sheet stack 16 in the opposite direction of transport T.In the holding position, the at least one push button foot 21 is placed when the uppermost sheet of the sheet stack 16 has been lifted by the separating suction cups 19 along the rear edge, in order to prevent underlying sheets of the sheet stack 16 from being stirred up, when at least one trailing edge blower 22, preferably arranged behind the rear edge at the level of the top of the sheet stack 16, blows air in the transport direction T into the gap open between the sheet lifted by the separating suction cups 19 and the rest of the sheet stack 16.

[0026] A sheet lifted by the separating suction cups 19 is transferred in the common plane to the transport suction cups 20, which perform a predominantly vertical, intermittent movement in and against the transport direction T. Like the separating suction cups 19, the transport suction cups 20 have flexible suction cups which are pressurized with negative pressure after the separating suction cups 19 are lifted, in order to draw the lifted sheet towards them. Simultaneously, the separating suction cups 19 are no longer pressurized with negative pressure, so that they release the already lifted sheet. The air blown under the lifted sheet by the at least one trailing edge blower 22 in the transport direction T lifts the sheet, which is raised at its trailing edge, from the sheet stack 16 across its entire surface and forms an air cushion under the sheet. The sheet is then transported on this cushion in the transport direction T, driven by the horizontal movement of the transport suction cups 20.

[0027] The sheet feeder 02 preferably further comprises a sheet flap 23, which is also pivotably held and displaced by a flap shaft 24 in machine-cycle intervals, i.e., for each individual sheet transported. The sheet flap 23 is arranged at the leading edge of the sheet stack 16, for example, in extension of the front stop 17 above the front stop 17. To clear the transport path for the sheet transported by the transport suction cups 20, the sheet flap 23 is displaced from a vertical position to an at least approximately horizontal position, so that the transported sheet can be moved in the transport direction T over the sheet flap 23.

[0028] Furthermore, the sheet feeder 02 comprises a feeder table 25, preferably a belt table, for example with at least one first roller and a second roller around which at least one suction belt is guided. The first roller, which is downstream of the sheet flap 23, can be assigned at least one indexing roller (not shown), which is preferably moved vertically in sync with the machine cycle and thus ensures that the transported sheets are positioned against the feeder table 25. From the feeder table 25, the forming sheet flux is transported to the feeder table 26 of the sheet feeder 03 and there, at a feeder line, is accelerated, for example by a vibrating gripper system 27, and fed to a feeder drum 28, which feeds the sheet to the impression cylinder 08 of the first printing unit 04. The vibrating gripper system 27 thus also performs a movement in sync with the machine cycle, i.e., the vibrating gripper system 27 completes a full forward and backward movement for each individual sheet.One machine cycle thus corresponds exactly to one revolution of a single-revving shaft or a single-sized cylinder, for example the feed drum 28, of the machine, in particular the printing press 01.

[0029] Preferably, the sheet feeder 02, to assist in singulating and / or transporting the sheets, has first side-edge blowers 29 on the lateral edge of the sheet stack 16, preferably in the region of the top edge of the sheet stack 16, which direct at least one jet of air or a fan of air transversely to the transport direction T onto the top edge of the sheet stack 16. The first side-edge blowers 29 can, for example, be positioned as required via flexible blow tubes with nozzles. Alternatively or additionally, second side-edge blowers 30 can be provided, which can preferably also be located on the lateral edge of the sheet stack 16, preferably in the region of the top edge of the sheet stack 16. The second side-edge blowers 30 can, for example, be spaced downstream of the first side-edge blowers 29 in the transport direction T.The second side-edge blowers 30 can each include a contact surface for the side edge of the sheet stack 16 and have one or more blowing air openings from which blowing air is introduced in the upper region of the side edge of the sheet stack 16. The first side-edge blowers 29 and the second side-edge blowers 30 can be operated continuously or intermittently with positive pressure. The sheet feeder 02 can have additional loosening blowers (not shown) for loosening the sheets of the sheet stack 16.

[0030] The Fig.Figure 3 shows an enlarged view of a sheet feeder 02 of a sheet-processing machine, for example, the sheet feeder 02 described above in a front view, i.e., viewed in the transport direction T of the sheets. The sheet feeder 02 has first sheet guide elements 31, for example, flat metal sheets, which form a guide surface for sheets from above in the plane of the preferably fully raised separating suction cups 19 or the transport suction cups 20. Preferably, a plurality of first sheet guide elements 31 are arranged in the plane between the transport suction cups 20 or across the width of the sheet feeder 02. Furthermore, the sheet feeder 02 has at least one second sheet guide element 32 for forming a stabilizing deformation of a sheet 33 lifted by the separating suction cups 19, deviating from the horizontal plane.

[0031] Preferably, a plurality of second bow guide elements 32 are arranged spaced apart from one another, particularly between the transport suction cups 20. The second bow guide elements 32 can extend in the transport direction T and be designed with a curve facing the raised bow 33. The second bow guide elements 32 can be curved elements such as corrugated sheet metal. The second bow guide element(s) 32 impart a wave-like deformation to a raised bow in the transport direction T, so that this raised bow is a stabilized bow 33. The first bow guide elements 31 and the second bow guide elements 32 form a common bow guide for each stabilized bow 33 raised by the separating suction cups 19, particularly extending in and transversely to the transport direction T.The extension of the arch guide in the transport direction T can, for example, correspond to at least half the arch length. Preferably, the first arch guide element(s) 31 and / or the second arch guide element(s) 32 are arranged in a fixed or immovable position.

[0032] In particular, one or more first sheet guide elements 31 and / or one or more second sheet guide elements 32 are arranged above a region of the trailing edge of a sheet stack 16 located in the sheet feeder 02, especially in the region of the sheet separator 18. The first sheet guide elements 31 and / or the second sheet guide elements 32 can also extend above the transport path up to the sheet flap 23 or be designed to taper off in the transport direction T. Furthermore, the separating suction cups 19 and / or transport suction cups 20, which are designed especially adjacent to a second sheet guide element 32, can be designed to be displaceable about a pivot axis oriented in the transport direction T, such that they adapt to a profile of the stabilized sheet 33.Furthermore, one or more first bow guide elements 31 and / or one or more second bow guide elements 32 may also have blow openings, in particular slot nozzles, in the surface facing the raised stabilized bow 33.

[0033] Operating principle: During operation, loosening blowers loosen the sheet stack 16, while separating blowers, in particular trailing edge blowers 22 and / or side edge blowers 29, 30, separate the sheet drawn in and lifted by the separating suction cups 19 from the sheet stack 16, such that the lifted sheet reaches the sheet guide consisting of the first sheet guide element(s) 31 and the second sheet guide element(s) 32. When the sheet lifted by the separating suction cups 19 reaches the sheet guide, it is deformed by the surface of the second sheet guide element(s) 32 and gains stiffness in the sheet travel direction or transport direction T, so that a stabilized sheet 33 is formed.

[0034] The sheet can be drawn around the second sheet guide elements 32, for example, by two or four separating suction cups 19 and / or transport suction cups 20 per side. These second sheet guide elements 32 are positioned slightly lower than the uppermost position of the separating suction cups 19. The sheet is given its shape or deformation by the second sheet guide elements 32, which are particularly round and robustly designed, before it is conveyed in the sheet travel direction or transport direction T. The degree of deformation depends on the height of the sheet guide relative to the position of the separating suction cups 19. Even a slight inclination of the separating suction cups 19 or transport suction cups 20 directly adjacent to the second sheet guide elements 32 can influence the sheet tension and thus the intensity of the deformation. The separating air, especially from the trailing edge blower 22, assists in deformation of the sheet towards the leading edge.This means that the arc is not only stiffened in the area of ​​the separating suction cups 19 or transport suction cups 20.

[0035] If the sheet guide, in particular the first sheet guide elements 31 or the second sheet guide elements 32, are provided with additional air blowing openings, especially with air slot nozzles, the applied air blowing can hold and guide the stabilized sheet 33 on the guide elements. The stabilized sheet 33 can, for example, have a sheet travel direction defined by high-pressure nozzles and preferably float on a cushion of air along the sheet guide. Holding and guiding the stabilized sheet 33 on the sheet guide also supports the removal of the forming sheet flake. The special sheet guide, especially in a wave shape, stabilizes the sheet to be cut in the printing direction or transport direction T so that it cannot shorten and is conveyed precisely to the feed table 25, in particular the infeed roller with indexing rollers.The increased stiffness of the stabilized arch 33 makes it easier to transport it forward in the transport direction T. Reference symbol list 01 Printing press 02 Bow feeder 03 Archery 04 Printing work 05 Reversing device 06 Paint Shop 07 Sheet display 08 Counterpressure cylinders 09 Rubber blanket cylinders 10 plate cylinders 11 Control Center 12 frame 13 lifting chains 14 Stacking support plate 15 pallets 16 stacks of sheets 17 Front stop 18 sheet separators 19 vacuum cleaners 20 transport vacuums 21 Pushbutton base 22 back-edge blowers 23 Arch flap 24 flap shaft 25 Investor table 26 Laying table 27 swing grippers 28 Attachment drum 29 first side-edge blowers 30 second side edge blowers 31 first bow guide elements 32 second bow guide elements 33 stabilized bow T Transport direction

Claims

[1] Sheet feeder (02) for a sheet processing machine (01) with a sheet separator (18) comprising a separating suction cup (19), wherein the separating suction cups (19) are arranged to be vertically displaceable, wherein at least one first sheet guide element (31) forms an at least approximately horizontal guide surface in a plane of the raised separating suction cups (19) and wherein at least one second sheet guide element (32) is provided to form a stabilizing deformation of a raised sheet (33) deviating from the plane, characterized by , that one or more second arch guide elements (32) extend in the transport direction (T) of the arch (33) with a curve facing the raised arch (33). [2] Sheet feeder (02) according to claim 1, wherein the sheet separator (18) further comprises transport suction cups (20) for transporting the raised sheet (33) in the transport direction (T) and a plurality of first sheet guide elements (31) are arranged in the plane between the transport suction cups (20) and / or over the width of the sheet feeder (02). [3] Sheet feeder (02) according to claim 1 or 2, wherein a plurality of second sheet guide elements (32) are arranged spaced apart from each other between transport suction cups (20). [4] Bow feeder (02) according to claim 1, 2 or 3, wherein first bow guide elements (31) and second bow guide elements (32) form a common bow upper guide for the raised bow (33) with an extension in and transverse to the transport direction (T) of the bow (33). [5] Sheet feeder (02) according to claim 1, 2, 3 or 4, wherein one or more first sheet guide elements (31) and / or one or more second sheet guide elements (32) are arranged above a region of a trailing edge of a stack of sheets (16) located in the sheet feeder (02) and / or in the region of the sheet separator (18). [6] Sheet feeder (02) according to claim 1, 2, 3, 4 or 5, wherein one or more first sheet guide elements (31) and / or one or more second sheet guide elements (32) have at least one pneumatic opening in the surface facing a sheet stack (16). [7] Sheet feeder (02) according to claim 1, 2, 3, 4, 5 or 6, wherein separating suction cups (19) and / or transport suction cups (20) are displaceable about a pivot axis oriented in the transport direction (T) of the sheet (33). [8] Sheet feeder (02) according to claim 1, 2, 3, 4, 5, 6 or 7, wherein separating suction cups (19) and / or transport suction cups (20) adjacent to a second sheet guide element (32) are displaceable about a pivot axis oriented in the transport direction (T) of the sheet (33). [9] Sheet feeder (02) according to claim 1, 2, 3, 4, 5, 6, 7 or 8, wherein the sheet feeder (02) comprises a feeder table (25) with a transport roller forming a transport path for the stabilized sheet (33) and at least one indexing roller. [10] Method for operating a sheet feeder (02) of a sheet processing machine (01) with a sheet separator (18) comprising a separating suction cup (19), wherein the separating suction cups (19) are vertically displaced for singulating sheets (33) of a sheet stack (16) and wherein at least one first sheet guide element (31) forms an at least approximately horizontal guide surface in a plane of the raised separating suction cups (19), characterized by, that at least a second arc guide element (32) imposes a wave-shaped deformation on an arc (33) lifted by the separating suction cups (19), stabilizing the lifted arc (33) in the transport direction (T). [11] Method according to claim 10, wherein several first bow guide elements (31) and several second bow guide elements (32) form a common bow upper guide for guiding the raised bow (33) in the transport direction (T). [12] Method according to claim 10 or 11, wherein the at least one first bow guide element (31) and / or the at least one second bow guide element (32) has at least one pneumatic opening and a blowing air supply is applied, so that the raised bow (33) is guided by means of an air cushion. [13] Method according to claim 10, 11 or 12, wherein the at least one first sheet guide element (31) and / or the at least one second sheet guide element (32) has at least one blow air opening and a blow air is applied depending on the substrate and / or machine speed. [14] Method according to claim 10, 11, 12 or 13, wherein the stabilized sheet (33) is transported on a transport path between a transport roller and at least one indexing roller of a feeder table (25) of the sheet feeder (02). [15] Method according to claim 10, 11, 12, 13 or 14, wherein the sheet feeder (02) feeds sheets (33) with a basis weight of less than 100 g / m² 2 and / or statically chargeable materials are processed.

Images