Lifting suction device control method

Abstract

The invention relates to a method for controlling the tilting movement (17) of a lifting suction device (6) of a sheet feeder (2), wherein the tilting movement (17) is adjusted during machine operation, the tilting movement (17) being automatically adjusted by a servo drive (19), and the servo drive (19) being controlled by a controller (16) for this purpose based on sensor measurement values ​​(22). A contour sensor (10) can be used as the sensor.

Description

Technical Field

[0001] The invention relates to a method for controlling the tilting movement of a lifting suction unit of a sheet feeder, wherein the tilting movement is readjusted during operation of the machine. Background Art

[0002] Sheet feeders (such as those of printing presses and die-cutting machines) are equipped with suction heads, which include a separating suction device and a conveying suction device. The separating suction device is also known as a lifting suction device, while the conveying suction device is known as a dragging suction device.

[0003] DE 10 2016 114 920 A1 describes a position joint operatively connected to a separating suction machine, wherein adjustment of the position joint causes an adjustment of the angle of the active surface of the separating suction machine relative to the stack surface plane. The position joint is designed to be adjustable in order to change its position during operation of the sheet-fed printing press. Summary of the Invention

[0004] The object of the present invention is to provide an alternative method for controlling the tilting movement of a lifting suction device of a sheet feeder.

[0005] This object is achieved by a method for controlling the tilting movement of a lifting suction device of a sheet feeder, wherein the tilting movement is supplemented during machine operation, the tilting movement is automatically supplemented by a servo drive, and the servo drive is controlled for this purpose by a controller based on measured values ​​of a sensor.

[0006] An advantage of the method according to the invention is that this supplementary adjustment does not require any operator intervention.

[0007] There are several possible improvement options:

[0008] As the sensor, a profile sensor can be used.

[0009] The profile sensor may be a 2D profile sensor.

[0010] The contour sensor can be directed toward the top and the back of the sheet stack.

[0011] Based on the measured values, a median and / or average value can be determined in a control loop. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Advantageous developments also emerge from the following description and the accompanying drawings.

[0013] The accompanying drawings show:

[0014] Figure 1 : Sheet feeder;

[0015] Figure 2 : Sheet separation device;

[0016] Figure 3 : sheet stack outline; and

[0017] Figure 4 : Regulation loop. DETAILED DESCRIPTION

[0018] The printing press 1 includes a sheet feeder 2 having a sheet separator or suction head 3 that separates printing sheets 5 from a sheet stack 4. The suction head 3 includes a separating or lifting suction device 6 for lifting the printing sheets 5 from the sheet stack 4 and a transport or pulling suction device 7 for transporting the printing sheets 5 in a transport direction 8. The suction head 3 has a probe 9 for detecting the sheet stack 4. A profile sensor 10 (laser scanner), in particular a 2D profile sensor, is arranged in the center of the suction head 3 or in the area of ​​the probe 9.

[0019] The contour sensor 10 emits a laser beam 11 and has a measuring range 12. The contour sensor 10 is directed obliquely from above toward the rear edge 13 of the sheet stack 4, so that the measuring range 12 detects a portion of the top 14 and a portion of the rear side 15 of the sheet stack 4. The measuring range 12 forms a vertical line on the rear side 15 of the sheet stack 4.

[0020] The contour sensor 10 is connected to an electronic controller 16, which controls the tilting movement 17 of the lift suction unit 6 about a pivot axis 18. The pivot axis 18 runs horizontally and orthogonally to the conveying direction 8. To this end, the controller 16 is connected to a servo drive 19, which drives the tilting movement 17. The servo drive 19 can induce the tilting movement 17 via a mechanism. Suitable mechanisms are described in DE 102 22 056 A1 and DE 10 2016 114 920 A1, the relevant disclosures of which are incorporated into this specification. The tilting movement 17 adjusts the angular orientation of the suction surface 20 of the lift suction unit 6 relative to the top 14 of the sheet stack 4.

[0021] In the region of the rear edge 13, the course of the upper side 14 may deviate from the horizontal plane. The upper side 14 can be lowered towards the rear edge 13 or (as Figure 3 As shown) rises at an angle α. Figure 3In the figure, a indicates the position of the trailing edge 13, and b indicates the height of the sheet stack 4. The tilted position can be caused by damage to the sheet stack 4, extremely uneven printing of the corresponding printing sheets 5 in the sheet stack 4, moisture in the sheet stack 4, or a lower wedge in the sheet stack 4. As the height b of the sheet stack 4 decreases during the printing run, the magnitude of the angle α can change. During the ongoing printing run, the magnitude of the tilting movement 17 is automatically adapted to this change by the controller 16, so that the suction surface 20 of the lifting suction device 6 always rests parallel to the top side 14 on the uppermost printing sheet 5 of the sheet stack 4. This adaptation is preferably performed continuously / steplessly.

[0022] Figure 4 A control circuit 30 is shown, which varies the angle of the tilting movement 17 as a function of the angle α of the profile of the top side 14. The profile sensor 10 locally measures the height profile 21 of the sheet stack 4 once per machine revolution (one machine revolution corresponds to one full revolution of the plate cylinder of the printing press; a machine revolution corresponds to the sheet transport rhythm).

[0023] This measurement takes place after the pull-type suction device 7 has transported the previously separated printed sheet 5 out of the field of view of the profile sensor 10 and before the lift-type suction device 6 removes the next printed sheet 5 to be separated from the sheet stack 4. The software associated with the profile sensor 10 analyzes the height profile in real time and outputs a measured value 22 (angle) regarding the tilted position of the top side 14.

[0024] The n (number) most recently measured tilt position states are digitally stored in a memory 23 of the controller 16. The controller 16 includes a median and / or average filter, which is used to calculate the median and / or average value 24 of the n most recently measured tilt position states from the stored values. This reduces the impact of outliers and measurement errors on system reliability. If fewer than n measured values ​​are available (e.g., at press startup), the median and / or average value 24 is calculated using only the existing measured values.

[0025] This difference is determined from the median and / or mean value 24 and the current tilt angle 25 of the lift suction unit 6, resulting in an actual parallelism deviation 26 between the suction surface 20 of the lift suction unit 6 and the top of the stack. From the actual parallelism deviation 26 and the normally zero setpoint parallelism deviation 27, a control difference 28 of a controller 29 is determined, which controls the actuator 19.

[0026] When the printing material is very thin, it can be advantageous that the lifting suction device 6 tilts backward with respect to the stacking surface to reach the peeling effect. In addition, this dynamic tilting can be turned off (abgeschaltet) completely, and what replaces it is the tilting angle of pre-given static state.

[0027] In a variant not shown in detail in the figures, two such contour sensors are provided instead of a central contour sensor 10 , one of which is arranged to the right of the center of the suction head 3 as viewed in the transport direction 8 and the other to the left of the center of the suction head 3 .

[0028] Reference Signs List

[0029] 1 printing press

[0030] 2-sheet feeder

[0031] 3 suction tips

[0032] 4-sheet stack

[0033] 5 printing sheets

[0034] 6 Lifting suction device

[0035] 7 Pull-type suction device

[0036] 8 Conveying direction

[0037] 9 Probe

[0038] 10 Profile Sensor

[0039] 11 Laser beam

[0040] 12 Measuring range

[0041] 13 Back edge

[0042] 14 upper side

[0043] 15 dorsal

[0044] 16 Controller

[0045] 17 Tipping Movement

[0046] 18 Swing axis

[0047] 19 Servo Drive

[0048] 20 Suction surface

[0049] 21 Height Profile

[0050] 22 Measurements

[0051] 23 Memory

[0052] 24 Median and / or mean of stored values

[0053] 25 tilt angle

[0054] 26 Actual Parallelism Deviation

[0055] 27 Rated parallelism deviation

[0056] 28 Regulation difference (Regeldifferenz)

[0057] 29 Regulator

[0058] 30 Regulation loop

[0059] a The position of the rear edge

[0060] b Height of the sheet stack

[0061] α angle

Claims

1. A method for controlling the tilting movement (17) of a lifting suction device (6) of a sheet feeder (2), in which printed sheets (5) are separated from a sheet stack (4) and conveyed in a conveying direction (8), wherein: The tilting movement (17) is further adjusted during the operation of the machine, It is characterized by: The tilting movement (17) is automatically supplemented by the servo drive (19), and The servo drive (19) is controlled by a controller (16) for this purpose according to the measured values ​​(22) of the sensor, wherein a contour sensor (10) is used as the sensor, the contour sensor (10) emitting a laser beam (11) and having a measuring range (12), the contour sensor (10) being directed obliquely from above toward a rear edge (13) of the sheet stack (4) facing away from the transport direction (8), so that the measuring range (12) detects a part of the upper side (14) and a part of the rear side (15) of the sheet stack (4), wherein the The measuring range (12) forms a vertical line on the back side (15) of the sheet stack (4), and wherein the measured value (22) is the angle (α) at ​​which the upper side (14) of the sheet stack (4) descends or rises relative to the horizontal plane toward the rear edge (13), and the servo drive (19) drives the lifting suction device (6) in a tilting movement (17) about a swing axis (18) running horizontally and orthogonally to the conveying direction (8), so that the tilting angle of the tilting movement (17) changes as the angle (α) changes.

2. The method according to claim 1, It is characterized by: The profile sensor (10) is a 2D profile sensor.

3. The method according to claim 1 or 2, It is characterized by: In a control loop (30), a median and / or average value (24) is derived from the measured values ​​(22).

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