Sheet brake of a sheet processing machine, in particular a printing machine, and a method for depositing sheets

Abstract

Sheet brake of a sheet-processing machine, in particular a printing press, with suction rings (4) which are axially adjustable for displacement onto pressure-free corridors and for acting on sheets (2) conveyed in the sheet travel direction (BLR), wherein the suction rings (4) are arranged divergingly in the sheet travel direction (BLR) for transversely tightening the sheets (2), characterized in that brake bands (5) are provided for decelerating the sheets (2), wherein suction rings (4) and brake bands (5) are arranged one after the other in the sheet travel direction (BLR) and that the suction rings (4) can be driven in rotation by sheet contact.

Description

[0001] The invention relates to a sheet brake of a sheet processing machine, in particular a printing machine, according to the preamble of the first claim and to a method for depositing sheets.

[0002] In the deliveries of sheet-fed rotary printing presses, the sheets are picked up by gripper carriages from the last printing cylinder at their leading edge and then guided to the required guide quality of the sheet-producing sheet guide plates up to the delivery pile. There, the opening gripper releases the leading edge, allowing the pneumatic sheet brake on the underside of the sheet to initiate sheet deceleration. The lines of action of the friction forces introduced by the sheet brake lie on the designated pressure-free corridors, i.e., the sheet brake is divided into individual stations so that their force application points can be positioned axially in the respective pressure-free corridors, so that the blanks in between are left without wiping or scratching and without any loss of quality. The disadvantage of this is the "sagging" of the sheets between the individual stations. This leads to: - smearing contact with adjacent cross parts, e.g. the guide plate edge - more air inclusions in the stack due to the necessary greater drop height - Slipping of the curve side edges from the outer individual stations with resulting loss of braking force.

[0003] The result is poor stack edge quality and scratched sheets.

[0004] The reason for this axial shortening of the arch width projected onto the conveyor plane lies primarily in the oblique tension buildup of thin arches, which experience a point-by-point braking force application by the individual stations of the arch brake, leading to a stretching along the line of action of the force, which in turn also causes transverse stress components in the arch. This means that the tensioning of the arches during braking causes greater sagging between the braking stations.

[0005] Various patents attempt to solve this problem using a variety of approaches. However, none of the existing solutions achieves axial tightening of the arch to the point of extension.

[0006] DE 44 35 988 A1 discloses a device for braking sheets. This device takes the trailing edges of the sheets at the sheet conveying speed and releases them for storage at a delayed rate. The device contains a discontinuously driven braking belt that interacts with a suction device, which comes into at least partial contact with the sheet and thus decelerates it. A disadvantage of this solution is that discontinuously driven suction rings or suction belts arranged in the sheet conveying direction cannot prevent the sheets from sagging because they cannot tighten them transversely. Thus, components such as the weight of the sheets and blown air from above cause the sheets to sag.

[0007] DE 34 12 180 A1 discloses a device for depositing sheets onto a delivery pile, and DE 103 55 261 A1 discloses a sheet-processing rotary printing press with a sheet brake. Both documents propose a pneumatic catcher arrangement upstream of the sheet brake, which safely collects the sheets fed by the sheet conveying system and transfers them to the sheet brake. A disadvantage of these solutions is that there is no transverse tensioning of the sheets being deposited. Consequently, the problems caused by sheet sagging also occur here.

[0008] DE 10 2005 012 881 A1 discloses a sheet guiding device for a printing press in which a pneumatic guide element is arranged directly upstream of each suction roller in the conveying direction of the printed sheets. A central guide element assigned to a central suction roller directs the blowing air approximately parallel to the printed sheets, while the lateral guide elements direct the blowing air diagonally outward and opposite to the conveying direction of the printed sheets. This is intended to achieve precise guidance of the printed sheets and increase the braking effect of the sheet brake. The disadvantage of this solution is that the blowing air negatively influences the sheets' ability to react to the sheet brake. There is no effective cross-sheet tightening.

[0009] DE 10 2006 015 578 A1 discloses a sheet brake for a printing press with brake elements diverging in the sheet travel direction for transversely tensioning the printing substrate sheets. This brake element is characterized by the fact that the brake elements are driven in rotation at uneven speeds. The brake elements are advantageously designed as bands or belts. A disadvantage of this solution is that the diagonally arranged brake elements require a wider pressure-free corridor. In this case, the inclined position of the suction belt, limited by the width of the corridor, is simply not sufficient to achieve transverse tensioning of the sheets to the desired stretched position.

[0010] DE 39 39 212 A1 discloses a sheet guiding and braking device in printing press deliveries. It proposes arranging several sheet guiding rods with longitudinal grooves in front of inclined suction rollers. Like the suction rollers, the longitudinal grooves are inclined outwards from the center of the machine at an angle α0 to α nWhile angled friction edges in the sheet guide and / or pre-suction devices do reduce the sagging effect somewhat, their effectiveness is significantly limited, as the transverse force required to tighten the sheets simultaneously exacerbates the cause by increasing the longitudinal force caused by the friction edge. Another disadvantage of angled suction wheels or suction belts that rotate / circulate at depositing speed is that they suck in the sheets well in advance of the gripper opening to build up the necessary vacuum. This unnecessarily tightens the sheets to be deposited before they are slowed down. This also increases the sagging of the sheets.

[0011] DE 10 2006 035 559 A1 shows a sheet brake system for braking printed sheets, wherein a roller axis is arranged eccentrically offset relative to one or each rotation axis of each brake element.

[0012] DE 42 39 561 A1 shows a chain conveyor of a sheet-fed printing press.

[0013] DD - PS 88 799 shows a delivery device on sheet-processing machines with a pneumatic sheet brake, wherein two or more suction rollers known per se are arranged at a horizontal and vertical distance from one another and their peripheral speeds are equal or slightly different from one another.

[0014] The invention is therefore based on the object of providing a device and a method with which improved transverse tightening and braking of the sheets is achieved with minimal pressure-free corridors.

[0015] According to the invention, the object is achieved by a device having the features of the 1st claim and a method having the features of the 9th claim.

[0016] The invention has the advantage that the suction rings can be positioned at a very high angle with minimal pressure-free corridors, resulting in more effective axial sheet tightening. The braking forces achieved by the brake bands ensure optimal braking, enabling precise sheet placement even at higher sheet conveying speeds.

[0017] A preferred embodiment of the invention has the advantage that the sheets are first sufficiently taut laterally by inclined pre-suction rings before being transferred to the brake bands in the best possible flatness. The brake bands are preferably dynamically driven, so that longitudinal tautness of the sheets, which causes sagging, is largely avoided. The suction rings are preferably arranged at an angle of 2° to 20° to the sheet travel direction. An angle between 10° and 15° is particularly preferred.

[0018] The invention achieves a significant simplification of the sheet brake in a surprisingly simple manner, as the suction belts can be positioned straight, eliminating the need to compromise on the axial stabilization of the belts from a belt design perspective. Pressure-free corridors can thus be minimized.

[0019] A preferred development of the invention has the advantage that the sheets are safely picked up by pre-suction rings that can be raised intermittently and reliably guided to the brake bands. This timing ensures reliable suction of the sheets without the aid of the blown air from above, which is so detrimental to the sagging behavior. Any interference with subsequent sheets is also reliably avoided.

[0020] The invention will be explained below by way of example. The accompanying drawings illustrate this schematically: Fig. 1: Side view of the delivery of a sheet-fed rotary printing press with brake bands and pre-suction rings in front of the delivery stack; Fig. 2: Top view of the boom storage area with brake bands and inclined pre-suction rings; Fig. 3: Embodiment with pre-suction rings that can be raised intermittently, the pre-suction rings being shown in the sheet receiving position; Fig. 4: Embodiment according to Fig. 3 with pre-suction rings shown in the sheet transfer position.

[0021] The Fig. 1 shows, in a preferred embodiment of the invention, a delivery of a sheet-processing machine, in this case a sheet-fed rotary printing press operating according to the offset process. The delivery comprises a sheet conveyor system which transports the sheets 2 that have been printed, varnished, processed, etc., in the printing press to a delivery stack 6. This sheet conveyor system is designed as a chain conveyor system with two delivery chains, each guided laterally on the frame, between which gripper carriages 1 are arranged. The gripper carriages 1 contain sheet fixing systems with which the sheets 2 to be transported are gripped at the leading edge. The delivery chains guide the gripper carriages 1 on a gripper carriage track 1.1 in the sheet travel direction BLR up to above the delivery stack 6, where the gripper carriages 1 release the sheets 2 for deposit.Sheet guide plates 3 are preferably arranged on the sheet conveyor path, which guide the sheets 2 on their way to the delivery pile 6. An air cushion can be formed between the sheet guide plate 3 and the sheets 2. A sheet brake is arranged in front of the delivery pile 6, which takes the sheets 2 to be delivered from the gripper carriages 1 and, after the sheets have been released, decelerates them from machine speed to delivery speed. The sheet brake contains at least two braking stations, which are placed on the side edge of the sheets 2 or on print-free corridors. After deceleration by the sheet brake, the sheets 2 are aligned at leading edge stops (not shown) and neatly deposited on the delivery pile 6. The printing press can be switched between straight printing and perfecting and back-to-back printing modes.

[0022] The sheet brake arranged upstream of the delivery pile 6 comprises two functional components. The first functional component consists of pre-suction rings 4 arranged across the sheet width, which are arranged diverging relative to the sheet travel direction BLR for cross-sheet tensioning. The pre-suction rings 4 are positioned on pressure-free corridors and are constantly driven by a rotary drive 4.1 at at least approximately the machine speed. The rotation speed of the pre-suction rings 4, which rotate about an axis, is preferably between 95% and 100% of the machine speed. If the rotary drive 4.1 is to be omitted, the pre-suction rings 4 can alternatively be driven by the sheet contact.

[0023] The second functional part of the sheet brake consists of brake bands 5 arranged across the sheet width, which are arranged downstream of the pre-suction rings 4 in the sheet travel direction BLR. Preferably, each pre-suction ring 4 is followed by a brake band 5, which is thus positioned parallel to the sheet travel direction BLR on the same pressure-free corridor. Each brake band 5 runs over at least two deflection rollers, between which a suction box is arranged. A band or belt with openings can be used as the brake band 5. However, it could also have two seals forming a suction channel, which can be designed, for example, as two narrow round cords. Fig. 1, the brake bands 5 are shown interacting with three deflection pulleys. One of these deflection pulleys is designed as a drive pulley, which is driven by a brake drive 5.1.

[0024] The brake bands 5 are driven by the brake drive 5.1 such that the brake bands 5 located above the suction box move in the sheet travel direction BLR. The brake bands 5 are driven dynamically and periodically between the machine speed and the depositing speed. In this preferred dynamic operation, the brake drive 5.1 is synchronized with the machine control system via a control unit (not shown). In alternative embodiments, a constant speed below the machine speed can also be selected for the brake bands 5. Alternatively, it can also be provided to also drive the pre-suction rings 4 dynamically between the machine speed and a lower speed. The drive of the pre-suction rings 4 can be controlled independently of the constant or dynamic drive of the brake bands 5.The suction air supply to the pre-suction rings 4 and the brake bands 5 can also be adjusted and regulated separately. In further embodiments, the brake bands 5 can also assume a slight inclination to further increase the transverse sheet tension. This inclination can be adjustable so that it is only used when necessary. In a further development, the deflection rollers of the brake bands 5 adjacent to the delivery stack 6 are cyclically lowered in order to bring the sheets 2 closer to the surface of the delivery stack 6 during the braking process.

[0025] The Fig. Figure 2 shows the delivery stack 6 in plan view with the sheet brake and sheet guide plate 3 arranged upstream in the sheet travel direction BLR. The pre-suction rings 4 of the sheet brake can be seen, which are arranged outwards at an angle to the sheet travel direction BLR. The angle formed between the direction of rotation of a pre-suction ring 4 and the sheet travel direction BLR is, for example, 10°. The brake bands 5 arranged serially downstream of the pre-suction rings 4 in the sheet travel direction BLR are arranged parallel to the sheet travel direction BLR. If a pre-suction ring 4 is used centrally in the delivery stack 6, this pre-suction ring 4 is also arranged parallel to the sheet travel direction BLR, as shown in Fig. 2. Further pre-suction rings 4 and / or brake bands 5 can be arranged across the sheet width. The inclination of all pre-suction rings 4 to the sheet travel direction BLR can be the same or increase towards the outside. In a preferred development of the invention, the inclination of the pre-suction rings 4 can be adjustable. This inclination adjustment can be carried out manually or controlled by an automatic adjustment mechanism from the control center of the printing press. The pre-suction rings 4 can thus be adjusted according to the parameters of the current print job. The pre-suction rings 4 can also be adjusted according to sensor values. The inclination adjustment of the pre-suction rings 4 can be combined with their axial adjustment. In alternative embodiments not shown, the suction belts can also be arranged upstream of the suction rings in the sheet conveying direction.

[0026] The Fig. 3 and Fig. 4 show, in a preferred embodiment of the invention, a delivery device with pre-suction rings 4 that can be raised intermittently, this device otherwise corresponding to the device described above. The lifting movement of the pre-suction rings 4 is realized by a lifting drive 4.2, which can be controlled independently of the rotation drive 4.1 of the pre-suction rings 4. By means of the lifting drive 4.2, the pre-suction rings 4 can be moved at least between a sheet receiving position ( Fig. 3) and a sheet transfer position ( Fig.4). In the sheet take-over position, the distance between the pre-suction rings 4 and the gripper carriage track 1.1 of the gripper carriage 1 is minimized so that the pre-suction rings 4 come into contact with the sheets 2 transported by the gripper carriage 1. The suction air from the pre-suction rings 4 ensures secure contact between the sheets 2. The subsequent lowering movement of the pre-suction rings 4 takes the sheet 2 downwards so that the sheet 2 is quickly and safely applied to the braking bands 5. While the sheets 2 are in contact with the pre-suction rings 4, the desired axial transverse tightening of the sheets 2 takes place. The braking bands 5 then take over the deceleration of the sheets 2 from machine speed to delivery speed.

[0027] How it works: By dividing the functions of the sheet brake into a first functional part, pre-suction rings 4, with the main function of axial tightening, and a second functional part, brake bands 5, with the main function of braking, the previously contradictory technical requirements are brought together in a simple manner according to the invention. The transverse tightening of the sheets 2 achieved by the pre-suction rings 4 can be maximized by a very large inclination without the need for wider corridors. By rotating the pre-suction rings 4 at almost machine speed, additional tightening of the sheets 2, which would promote sheet sag, is avoided. If the pre-suction rings 4 are raised in cycles, the sheets 2 are guided reliably to the brake bands 5 even without the blast air from above, which promotes sheet sag.

[0028] The brake bands 5 are preferably arranged parallel to the sheet travel direction BLR, thereby ensuring narrow, pressure-free corridors. The parallel brake bands 5 also do not form any inclined friction edges that would promote sheet sagging. By taking over the sheets at machine speed, the preferably dynamically driven brake bands 5 prevent the sheets 2 from being tightened, which would promote sheet sagging, but still apply the necessary braking force for the sheets 2. The required sheet braking is transferred to the sheets 2 by the decelerating brake bands 2, ensuring reliable braking of the sheets 2, which have been perfectly axially and transversely tightened by the pre-suction rings 4. After the sheet has been deposited, the brake bands 5 are accelerated back to machine speed in order to be able to take over the next sheet 2. List of reference symbols used 1 gripper trolley 1.1 Gripper carriage track 2 sheets 3 sheet guide plate 4 pre-suction rings 4.1 Rotation drive 4.2 Lifting drive 5 brake band 5.1 Brake drive 6 boom stacks BLR sheet running direction

Claims

[1] Sheet brake of a sheet-processing machine, in particular a printing press, with suction rings (4) which are axially adjustable for displacement to pressure-free corridors and which act on sheets (2) conveyed in the sheet travel direction (BLR), wherein the suction rings (4) are arranged diverging in the sheet travel direction (BLR) for transversely tightening the sheets (2), characterized by that brake bands (5) are provided for decelerating the sheets (2), wherein suction rings (4) and brake bands (5) are arranged one after the other in the sheet travel direction (BLR) and that the suction rings (4) can be driven in rotation by sheet contact. [2] Sheet brake according to claim 1, characterized by that the diverging inclination of the suction rings (4) is adjustable. [3] Sheet brake according to one of claims 1 and 2, characterized by that the suction rings are designed as pre-suction rings (4) and are arranged in alignment upstream of the brake bands (2) in the sheet travel direction (BLR). [4] Sheet brake according to one of the preceding claims, characterized by that the brake bands (5) are arranged parallel to the sheet travel direction (BLR). [5] Sheet brake according to one of the preceding claims, characterized by that the brake bands (5) can be driven discontinuously. [6] Sheet brake according to claim 5, characterized by that the brake bands (5) can be driven periodically between machine speed and deposit speed. [7] Sheet brake according to claim 3, characterized by that the pre-suction rings (4) can be moved between at least two positions. [8] Sheet brake according to claim 7, characterized by that the pre-suction rings (4) and / or deflection rollers of the brake bands (5) assigned adjacent to a delivery stack (6) are movable in cycles between a sheet receiving position and a sheet transfer position. [9] Method for depositing sheets in a sheet-processing machine, wherein the sheets (2) are essentially only transversely stretched by a sheet brake on a first conveyor section of rotating suction rings (4) arranged at an angle of 2° to 20° to the sheet travel direction (BLR) and driven by sheet contact in a rotational manner at at least approximately the sheet travel speed, and said transversely stretched sheets (2) are essentially only decelerated on a second conveyor section by brake bands (5) arranged serially downstream of the suction rings (4) and parallel to the sheet travel direction (BLR), wherein the inclination of the suction rings (4) is adjustable.

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