Procedure for filing sheets

Abstract

Method for depositing sheets (1) transported in a delivery of a sheet-processing machine, wherein gripper carriages (3) guided around the delivery transport sheets (1) along a sheet conveying path, wherein a sheet brake (6) with rotating and / or circulating sheet brake elements (6.1) is arranged upstream of a delivery pile (2) on the sheet conveying path and the sheet brake (6) has a sensor device (6.3), wherein the distance between two successive sheets (1), namely the sheet (1) decelerated by the sheet brake (6) to the following sheet, is determined by means of the sensor device (6.3) and an evaluation device, and the determined distance is used to control devices influencing the sheet delivery, wherein the sheet brake (6) comprises a sheet brake element (6.1) and a height-adjustable catcher element (6.2) arranged upstream of this in the sheet travel direction (BLR), and the height of the catcher element (6.2) is adjusted such that the sheets (1) do not fall below a minimum distance from one another.

Description

[0001] The invention relates to a method for depositing sheets.

[0002] With the sheet brakes currently in use, there is a risk of sheet contact between the sheet being deposited, which is already traveling at a reduced speed due to the sheet brake, and the following sheet, which is still being transported at machine speed. This contact results in damage to the trailing edge of the braked sheet and the leading edge of the following sheet. This contact then causes skew and, in extreme cases, overshoot, which can lead to poor stack formation or even an emergency stop of the press. Furthermore, the sheets can rub against each other.

[0003] DE 196 20 938 C2 discloses a method for smear-free stacking of printed sheets on a stack. A code that can be read by a reflective sensor can be assigned to a circulating belt. Devices in the delivery can be controlled from the position information of the circulating belt. A disadvantage of this solution is that a brake cam offers only a small sheet contact surface, which is insufficient for proper sheet braking. Furthermore, contact between the sheets cannot be prevented.

[0004] EP 1 108 671 B1 discloses a sheet braking system for a delivery of a sheet-processing machine. An upstream sensor sends a signal to terminate the braking process, and a downstream sensor sends a signal to re-accelerate the braking band. The disadvantage of this solution is that only a limited suction area is available for the braking band, which prevents optimal sheet deceleration.

[0005] Sheet contact with the sheet brake cannot be detected or prevented by the sensors.

[0006] DE 10 2004 022 237 A1 discloses a sheet brake in the sheet delivery of a printing press. Sensors are used at specific times to detect sheets that have not been transported away. The aim is to prevent a sheet being deposited from remaining in the suction groove of the sheet brake, thus rendering it ineffective for subsequent sheets. Waste, sheet stoppers, and overshoots are to be detected in a timely manner. The disadvantage of this solution is that a sheet brake with a continuous suction bar touches the entire surface of a sheet being deposited and is therefore not suitable for double-sided sheets.

[0007] DE 196 34 910 B4 discloses a method for depositing sheets onto a stack. It proposes a control system that allows the sheet depositing speed to be varied such that no damage is visible on the leading edge of the sheet when it hits the leading edge stops. The disadvantage of this solution is that it only repairs damage that occurs when the leading edges of the sheets hit the leading edge stops. It is not possible to prevent damage and errors caused by sheet contact.

[0008] DE 200 08 731 U1 shows a printing press, in particular a sheet-fed offset printing press, wherein an optically designed sheet travel monitoring device detects the actual spatial position of a sheet above a sheet guide element and an evaluation unit compares the actual spatial position of the sheet with an ideal spatial position with the aid of pattern recognition and, in evaluating this comparison, controls at least one device for influencing the sheet travel.

[0009] DE 10 2005 006 925 A1 shows a sheet transfer arrangement, wherein a blowing tube device is provided in a transverse gap section located between an end region of a sheet guiding device and a sheet brake, the blowing effect of which on a printed sheet running over the transverse gap section can be adjusted depending on the course of the respective sheet over the transverse gap section.

[0010] DE 10 2008 042 901 A1 shows a sheet brake of a sheet processing machine, in particular a printing press, and a method for depositing sheets, wherein brake bands are provided for decelerating the sheets, wherein suction rings and brake bands are arranged one after the other in the sheet travel direction.

[0011] The invention is therefore based on the object of further improving the filing process for sheets.

[0012] According to the invention, this object is achieved by a method having the features of the independent method claim. Advantageous embodiments will become apparent from the description and the drawings.

[0013] The invention has the advantage that improved sheet storage is achieved.

[0014] Preferred embodiments have the advantage of reliably preventing sheet contact between the sheet being deposited and the following sheet. This prevents damage to the leading and trailing edges of the sheets. The risk of skewed sheets and overshoots is further reduced. Operator errors are also reduced, as the existing sheet depositing devices are automatically adjusted based on the measurement results. This also reduces setup times and waste.

[0015] A preferred embodiment of the invention has the advantage that only a single sensor is required. This sensor is preferably arranged at one of the braking stations, particularly preferably at the centrally located braking station. With this sensor, the trailing edge of the sheet can be detected at a predetermined time. Based on the predetermined time, it is assessed whether the trailing edge of the sheet has slipped on the suction belt during the depositing process. From these measured values, the sheet brake can be adjusted, in particular the suction air shutoff and the belt speed can be adjusted. Furthermore, the location of the leading edge of the following sheet, which is still held in place by the gripper carriage, is known. A respective distance can be determined from the measured values ​​of the sensor and the location of the next leading edge of the sheet, which is known to the machine control system.After determining this distance between the trailing edge of the sheet to be deposited and the leading edge of the subsequent sheet, the devices responsible for sheet depositing are adjusted or readjusted based on the measurement result. These devices are preferably modified in such a way that, depending on the grammage, sheet format, etc., damage-free sheet depositing is always achieved.

[0016] The aim of the invention should always be to ensure sufficient space between the sheets for contact-free sheet delivery. However, if a guaranteed distance is not possible, for example with large sheet formats, the elements influencing sheet delivery are modified such that overlapping delivery is achieved. Here, too, the distance between the trailing edge of the braked sheet and the leading edge of the following sheet, which is guided above the trailing edge, can be determined. The location of this leading edge is known due to the fixation in the gripper systems of the gripper carriages, and the trailing edge of the leading sheet is detected by the sensor. In this preferred embodiment of the invention, contact-free sheet delivery is achieved by height-adjustable catcher elements arranged upstream of the sheet braking elements. These catcher elements can be controlled in such a way that contact with the sheets is reliably prevented.Raising the following sheet also improves the sensor's ability to detect the trailing edge of the sheet to be braked.

[0017] The sensor device can contain any sensor for detecting sheet edges. For example, an optical sensor, in particular a CCD array, or an ultrasonic sensor can be used. Other sensors for detecting sheet edges can also be used. Using the evaluation device, a distance value between two consecutive sheets can be determined from the detected sensor values. Machine data can also be fed to the evaluation device. In this development, simplified evaluation and trend analysis can be carried out, since the exact location of the trailing edge of the sheet is detected for a predetermined machine angle. Alternatively, a CCD camera can be used, which also enables skew sheet detection.

[0018] The sensor is preferably arranged in the area of ​​the effective depositing speed. Additional sensors can also be used to improve measurement uncertainty or evaluate other process settings. In a further development of the invention, provision is made for an additional sensor to be assigned to a different braking station. This second sensor is preferably arranged at the height of the first sensor and can be of identical construction. Using the two or more sensors, a skew on the sheet brake can be detected. A skew can be caused, for example, by two suction belts that are worn to different degrees. If such a skew is detected, a warning message is generated or an adjustment process is started automatically.In particular, if a skew curve is detected by at least two sensors, the detected skew of the curve can be compensated by differentiating the belt speed of the individual braking stations.

[0019] Devices for influencing sheet delivery include, for example, suction air control of the sheet brake, drive speed of the sheet brake elements, suction and blow air in the delivery, gripper opening point for the gripper carriages, control of catcher elements, etc. In particular, the determined distance between the sheets is used to correct the gripper opening point, the suction belt speed, particularly preferably to correct the acceleration ramp of the suction belts, and the control of catcher elements. Catcher elements, such as suction rings or suction belts, can thus be driven in an optimized manner at an irregular speed, rotating or revolving according to the sensor values. In a further development, sheet conveying systems can also be driven at variable speeds, such that the distance between the sheets is adjustable.For example, such a change in distance can be achieved by linear drives of the gripper carriages or by speed-variable sheet transfer systems in front of or in the delivery.

[0020] The invention will be explained below by way of example. The accompanying drawings schematically illustrate: Fig. 1: Delivery of a sheet-fed printing press with a sheet brake arranged in front of a delivery pile, wherein the sheet brake is assigned a sensor for determining the distance between the successive sheets; Fig. 2: Top view of the delivery pile with the sheet brake arranged upstream with respect to the sheet travel direction; Fig. 3: Preferred design of a sheet brake with catcher elements controlled by sensor values.

[0021] The Fig. 1 shows a delivery of a sheet-processing machine, in this case a sheet-fed rotary printing press operating according to the offset process. The delivery contains a sheet conveyor system that transports sheets 1 that have been printed, varnished, processed, etc., in the printing press to a delivery pile 2. 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 3 are arranged. The gripper carriages 3 contain sheet fixing systems with which the sheets 1 to be transported are gripped at the leading edge. The gripper carriages 3 are guided by the delivery chains on a gripper carriage track 3.1 in the sheet travel direction BLR up to over the delivery pile 2, where the gripper carriages 3 release the sheets 1 for deposit. Sheet guide plates 4, which guide the sheets 1 on their way to the delivery pile 2, are preferably arranged on the sheet conveyor path.An air cushion can be formed between sheet guide plate 4 and sheet 1.

[0022] A sheet brake 6 is arranged in front of the delivery pile 2, which takes the sheets 1 to be deposited from the gripper carriages 3 and, after the sheets have been released, decelerates them from machine speed to delivery speed. The sheet brake 6 contains at least two braking stations that are set on the lateral edge of the sheets 1 or on print-free corridors. After deceleration by the sheet brake 6, the sheets 1 are aligned at leading edge stops 5 and neatly deposited on the delivery pile 2. The delivery pile 2 is lowered by a pile lifting drive (not shown) during the sheet deposit process in such a way that the delivery pile surface forms an at least approximately constant deposit level for the incoming sheets 1. The printing press can preferably be switched between the straight printing and perfecting printing modes.

[0023] The sheet brake 6 arranged upstream of the delivery pile 2 has sheet braking devices assigned to each braking station. In the illustrated embodiment, each sheet braking device contains a suction belt 6.1 that is guided circumferentially over deflection rollers and a drive wheel. A suction plate having a suction channel is arranged between the deflection rollers, over which the suction belt 6.1 sweeps. The suction belt 6.1 has suction openings through which, in conjunction with a negative pressure present in the suction channel, a suction effect is created on the sheets 1. These suction belts 6.1 are driven preferably discontinuously by a drive (not shown). The drive is preferably dynamic and periodic between at least approximately the machine speed and the delivery speed. Alternatively, the suction belts 6.1 can also be driven at a constant speed below the machine speed. Instead of suction belts 6.1 Rings can also be inserted.

[0024] The sheet brake 6 further includes catcher devices arranged upstream of the sheet braking devices in the sheet travel direction BLR. The catcher elements are preferably designed as suction rings 6.2 and are arranged in alignment upstream of the suction belts 6.1. Suction rings 6.2 and suction belts 6.1 are assigned to a common braking station. In a further development of the invention, the suction rings 6.2 are designed to be tilt-adjustable for adjusting the sheet transverse tension. The suction rings 6.2 can be driven frictionally by sheet contact or by a separate drive.

[0025] The sheet brake 6 further contains a sensor device and an evaluation device (not shown), with which the distance between two consecutive sheets 1 can be determined. For this purpose, the sensor device preferably has a sensor 6.3, with which the edges of the sheets 1 are detected. The sensor 6.3 is preferably designed as an optical sensor. The sensor device is preferably further connected to a machine control system via the evaluation device, whereby the evaluation device can also be integrated into the machine control system. A control loop for adjusting the devices influencing the sheet deposit is established via the machine control system. The sheet depositing process can be influenced via the machine control system after evaluating the signals supplied by the sensor 6.3. Alternatively, the sensor 6.3 of the sensor device interact via the evaluation device with a separate control or regulating device for influencing the devices. For example, the transverse tensioning by the suction rings 6.2, the negative pressure applied to the suction belt 6.1 and / or suction ring 6.2, the speed of the suction belts 6.1 and / or suction rings 6.2, the position of the suction rings 6.2, a blower device arranged above the sheet conveying path, and / or the gripper opening point for the gripper carriages 3 can be controlled.

[0026] The Fig. 2 shows the delivery pile 2 in plan view with the sheet brake 6 and sheet guide plate 4 arranged upstream in the sheet travel direction BLR. The suction rings 6.2 of the sheet brake 6 are arranged diverging with respect to the sheet travel direction BLR for cross-sheet tensioning. The sensor 6.3 is assigned to the braking station arranged centrally with respect to the sheet width. The sensor 6.3 is preferably permanently assigned to the braking station and can be positioned accordingly. The sensor 6.3 is arranged here in the area of ​​the deflection roller of the suction belt 6.1, which is located downstream in the sheet travel direction BLR. The sensor 6.3 is positioned where the trailing edge of the sheet to be braked has the shortest distance to the leading edge of the following sheet during the braking process. The cable connections of the sensor 6.3 are not shown. Alternatively, the data can also be transmitted wirelessly to the evaluation device.

[0027] The Fig.Figure 3 shows, in a preferred embodiment of the invention, a sheet brake 6 in a delivery of a sheet-fed offset printing press. In addition to the sheet braking devices, the sheet brake 6 contains height-adjustable catcher elements, which here are designed as suction rings 6.2. A lifting device is assigned to the suction rings 6.2, with which the suction rings 6.2 can be adjusted between at least two vertically spaced positions. Preferably, each suction ring 6.2 is assigned a respective lifting device. The lifting device can be a pneumatic cylinder, for example. Alternatively, several or all of the catcher elements can be height-adjusted together.

[0028] The sensor device or evaluation device is connected to the respective lifting devices via the machine control system or the separate control or regulating device. The lifting devices are controlled by the machine control system or the control or regulating device in such a way that a subsequent sheet is transported in a plane that is at a vertical distance from the sheet 1 to be braked in order to avoid sheet contact. If the trailing edge of the sheet is detected by the sensor 6.3 and the sheet 1 to be braked by the sheet brake 6 has left the suction belt 6.1, the suction rings 6.2 are lowered by the lifting devices. The suction rings 6.2 take the suctioned subsequent sheet downwards and bring it into contact with the downstream suction belts 6.1.

[0029] How it works: By means of the gripper carriages 3 guided along the gripper carriage track 3.1, sheets 1 are transported along the sheet conveyor path to the delivery pile 2. The gripper carriages 3 guide the sheets 1 over the sheet brake 6 arranged upstream of the delivery pile 2, which sucks up the sheets 1 with suction belts 6.1 and possibly suction rings 6.2 and decelerates them after release by the respective gripper carriage 3. While a sheet 1 lying on the suction belts 6.1 is decelerated, the following sheet 1, transported at machine speed by the next gripper carriage 3, approaches.

[0030] Sensor 6.3 and the evaluation device determine the distance between sheet 1 decelerated by sheet brake 6 and the following sheet. For this purpose, the trailing edge of the decelerated sheet 1 and, if applicable, the leading edge of the following sheet are detected. In a preferred embodiment, only the trailing edge of the decelerated sheet 1 is detected and compared to the known location of the leading edge of the following sheet. The distance can be determined qualitatively or quantitatively.

[0031] The evaluation device can determine the distance between sheets 1 using image processing means, such as image processing software, if the sensor device provides an evaluable image. Alternatively, the evaluation device can link the data provided by the sensor device with supplied machine data and thus determine the distance.

[0032] The machine control system or the control or regulating device controls the devices influencing the sheet depositing process in such a way that the distance between the sheets 1 does not fall below a minimum distance. The minimum distance is adjustable in each case and prevents contact between the sheets 1, even when the sheets are guided overlapping. All devices influencing the depositing process can be controlled and adjusted by the machine control system or the control or regulating device. In a further preferred embodiment, the larger format sheets 1 are deposited by preventing sheet contact between the sheets 1 at the sheet brake 6 through the controlled lifting of the catcher elements.

[0033] Using the measurement data provided by sensor 6.3, the evaluation unit can also perform a trend analysis, which allows for early adjustment of the sheet depositing process. Furthermore, the data can be saved and used for subsequent jobs. The data can also be used for quality assurance purposes. The minimum distance between two consecutive sheets 1 can also be used as an additional control criterion for other control algorithms. List of reference symbols used 1 sheet 2 display stacks 3 gripper trolleys 3.1 Gripper carriage track 4 sheet guide plate 5 Front edge stop 6 Bow brake 6.1 Suction belt 6.2 Suction ring 6.3 Sensor BLR sheet running direction

Claims

[1] Method for depositing sheets (1) transported in a delivery of a sheet-processing machine, wherein gripper carriages (3) guided around the delivery transport sheets (1) along a sheet conveying path, wherein a sheet brake (6) with rotating and / or circulating sheet brake elements (6.1) is arranged upstream of a delivery pile (2) on the sheet conveying path and the sheet brake (6) has a sensor device (6.3), wherein the distance between two successive sheets (1), namely the sheet (1) decelerated by the sheet brake (6) to the following sheet, is determined by means of the sensor device (6.3) and an evaluation device, and the determined distance is used to control devices influencing the sheet delivery, wherein the sheet brake (6) comprises a sheet brake element (6.1) and a height-adjustable catcher element (6.2) arranged upstream of this in the sheet travel direction (BLR), and the height of the catcher element (6.2) is adjusted such that the sheets (1) do not fall below a minimum distance from one another.

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