CN109765632B

CN109765632B - Method for monitoring the operation of a sheet without an activation sensor

Info

Publication number: CN109765632B
Application number: CN201811329928.9A
Authority: CN
Inventors: S·克瑙夫; J·里茨; M·雅诺恰; N·R·诺瑞克
Original assignee: Heidelberger Druckmaschinen AG
Current assignee: Heidelberger Druckmaschinen AG
Priority date: 2017-11-10
Filing date: 2018-11-09
Publication date: 2020-10-20
Anticipated expiration: 2038-11-09
Also published as: CN109765632A; DE102017220039B3

Abstract

The invention relates to a method for detecting a missing sheet in a printing unit (7) of a sheet printing press by means of a measuring sensor (1) which detects a sheet (5) on a guide cylinder (2), wherein the detection of the sheet (5) is effected by the measuring sensor (1) as a function of an activation signal. The invention is characterized in that the activation signal is emitted by a controller (6) of the sheet-fed printing press, wherein the controller (6) calculates the correct time for emitting the activation signal taking into account at least the torsional state of the guide cylinder (2).

Description

Method for monitoring the operation of a sheet without an activation sensor

Technical Field

The invention relates to a method for detecting a missing sheet (Fehlbogen) in a printing unit of a sheet printing press by means of a measuring sensor which detects a sheet on a guide cylinder, wherein the sheet is detected by the measuring sensor on the basis of an activation signal.

Background

Such a method for detecting missing pages according to the generic type is known from the publication DE 102006019761 a 1. In this case, a sheet sensor is arranged in the circumferential region of the delivery cylinder/cylinder (bogenf ü hrendenen Zylinder) for detecting the sheet on the delivery cylinder. The sheet sensor is embodied as a reflective sensor. In this case, a reference surface is provided on the guide roller, which can be detected by a stationary reflection sensor. If the sheet is on the lead cylinder, the sheet covers the reference surface portion. Because the reflection characteristics of the sheet and the reference surface are different, the reflection sensor can determine from the reflected signal: whether an uncovered reference surface is detected or whether a page is located in the measuring area. In this case, when the sheet front edge on the reference surface enters the measuring area of the sensor, an intensity jump is generated, which is interpreted as a signal for the presence of a sheet. In order for the reflection sensor to also measure only the above-mentioned region of the reference surface, the position of the reference surface rotating together on the threading cylinder must then be synchronized with the position of the reflection sensor. This synchronization is achieved by means of a rotation angle sensor which is mounted on the flipper cylinder or on any other rotating body which is synchronized with this cylinder.

The problem with the above-described method is, however, that in this way and method a rotary encoder (Drehgeber) must be provided on each threading cylinder that should be monitored in order to obtain the required synchronization accuracy. In contrast, if the rotary encoder on each lead cylinder, which is monitored by means of the respective sensor, is eliminated, a signal must be derived from the coupled cylinder (or the rotating body), which may lead to deviations due to the only limited rigidity of the coupling in the gear train. In DE 102006019761 a1, however, these deviations are deliberately accepted by fitting a large reference surface on the guide roller and thus using a correspondingly large measuring region in which an intensity signal jump must occur for the presence of a sheet. However, this solution has the disadvantage that, for such large reference surfaces on the sheet-guiding drum, there is not always a suitable mounting position and, in addition, it is no longer possible to achieve an exact measurement of the position of the sheet front edge, but in principle only the conclusion that: whether the sheet edge is actually present in a relatively large area allows the sheet to be detected. The method of DE 102006019761 a1 is not suitable, however, for highly accurate measurement of the sheet edge in the gripper.

Alternatively, methods for detecting missing sheets are currently used, in which a small reflection surface is arranged in the passage of the sheet-guiding cylinder, wherein a signal is emitted for scanning the reflection area by a sheet-detecting sensor, which is realized by means of a second activation sensor (Aktivierungssensor) that detects the markings on the sheet-shaped cylinder individually. In this case, the activation sensor must be calibrated with very little tolerance, so that it sends the activation signal to the sheet-detecting sensor at the correct point in time, so that the sheet-detecting sensor in turn carries out the measurement process exactly at this point in time, at which the reflection surface in the path on the sheet-guiding cylinder is located below the sheet-detecting sensor. If this time synchronization does not properly match, the sheet detection sensor may perform an erroneous measurement outside the reflective surface on the lead cylinder and may report a missing sheet even if the sheet is accurately positioned on the reflective surface. However, the adjustment of such activation sensors is very complex in the production process and may also have to be repeated more often at the customer after the printing press has been built.

It is known from european patent EP 1820650B 1 to control a printing press by means of a torsion model (torsismodell). Such a controller comprises a computer in which a mathematical torsion model is stored in the form of software for describing the torsion state of the cylinders of the printing press which are coupled to one another in a rotatable mechanical manner. In this way, the controller of the printing press knows the exact angle of rotation of the respective cylinder in the printing press at all times, without the need to provide a rotary encoder on each cylinder for detecting the angle of rotation. In this way, the controller can perform a register adjustment or a setting of a front lay (vortermark) in the printing mechanism of the printing press precisely based on the calculated machine angle.

Disclosure of Invention

The object of the present invention is to provide a method for detecting missing sheets in a printing unit of a sheet printing press, which method allows missing sheets to be detected with a high degree of accuracy and which is sufficient to correctly trigger the detection of missing sheets with the aid of as few sensors as possible.

The object is achieved according to the invention by a method for detecting a missing sheet in a printing unit of a sheet printing press by means of a measuring sensor which detects a sheet on a guide cylinder, wherein the sheet is detected by the measuring sensor on the basis of an activation signal which is emitted by a controller of the sheet printing press, wherein the controller calculates a correct time for emitting the activation signal taking into account at least a torsional state of the guide cylinder. The advantageous design of the invention results from the preferred embodiments, the description and the figures.

The method according to the invention for detecting missing sheets can in principle be used for every sheet-fed printing press (e.g. offset printing and digital printing), in which method the sheets are transported on a guide cylinder. The detection of missing sheets is important to prevent the missing sheets from damaging the printing press on the transport path through the sheet printing press. For this reason, it is necessary to reliably detect missing errors of the sheets at several points in the sheet printing press, in order to be able to shut down the sheet printing press immediately in this case. On the other hand, false triggering should be avoided in order to avoid unnecessary standstill of the printing press in the case of sheets actually present. According to the invention, it is provided that the measuring sensor for detecting missing sheets uses an activation signal to carry out such a highly accurate measurement process, wherein the activation signal is no longer generated by the second activation sensor but is emitted by the machine controller of the sheet printing press. This has the advantage that no activation sensors to be set up in a complex manner are required, and in addition the machine controller of the sheet-fed printing press can be used to generate corresponding activation signals for carrying out a plurality of measurements on a plurality of guide cylinders. For this purpose, the machine controller calculates the correct time for the activation signal and takes into account the torsional state of at least the guide roller provided with the measuring sensor. In this way, the machine controller can now calculate the actual machine angle of the relevant page-guiding cylinder by means of the measuring sensor and thus also the appropriate point in time for the emission of the activation signal. To take account of the torsional state, the machine computer can use the torsional model known from patent document EP 1820650B 1. The use of an activation sensor for each monitored lead cylinder is no longer necessary, which leads to a considerable saving of sensors, in particular in long-format sheet printing presses with a plurality of printing units. However, the costly calibration work for the activation of the sensors is largely dispensed with.

In a first embodiment of the invention, it is provided that the controller uses a torsion model for calculating the activation signal taking into account at least the torsion state of the sheet-guiding cylinder, which torsion model is stored as a control program in the controller of the sheet-fed printing press. Such a torsion model is known in principle from EP 1820650B 1 and can also be used for other purposes for controlling Register or front Register marks (Register-odd vortermarker) in a printing press, which torsion model can then also be used for issuing an activation signal at the correct point in time in order to actuate a measuring sensor for detecting missing sheets. For this purpose, the rotation state of the printing press is represented in a software-based rotation model, so that the controller of the sheet printing press can access the current rotation state of the relevant lead cylinder at any time and can calculate the appropriate time for the activation signal to be emitted, taking into account the machine angle of the lead cylinder thus determined. The machine angle of the threading cylinder can thus be calculated at any time by means of a torsion model stored in the machine controller, and the corresponding activation signal can be derived taking into account the calculated machine angle. This calculation takes into account structural conditions, such as: the circumference of the flipper cylinder and the measuring position of the measuring sensor.

In a further embodiment of the invention, the torsion model takes into account, in addition to the torsion state of the guide cylinder, the torsion state of further cylinders of the sheet-fed printing press, which are mechanically coupled to the guide cylinder. In this way, a plurality of activation signals for further threading cylinders can be generated reliably, so that a plurality of activation signals for a plurality of threading cylinders having a respective measuring sensor for detecting missing sheets can be calculated by means of the same machine controller.

It is also provided that the controller takes into account the operating time of the measurement signal of the measurement sensor when calculating the correct time for the emission of the activation signal and accordingly triggers this time for the activation signal earlier. In particular, in the case of an ultrasonic sensor as the measuring sensor, the time of travel of the measuring signal from the ultrasonic sensor to the reflection surface (or to the sheet on the reflection surface) is not negligible. In this case, according to the invention, the machine controller is informed of the operating time, so that the machine controller can take this operating time of the measuring signal into account when calculating the time point for the emission of the activation signal. In this case, the associated operating time of the measurement signal can be stored individually for each measurement sensor of the machine controller, so that adaptation to different measurement sensors with different signal operating times is possible without problems. In this way, different measuring sensors can be used flexibly for the same sheet-fed printing press.

It is advantageously possible for the controller to detect the machine angle, which is supplied to the controller by at least one rotary encoder in the sheet-fed printing press, when calculating the correct time point for the emission of the activation signal. In this embodiment, the torsion model in the sheet-fed printing press obtains at least one actual measured value of the rotary encoder, so that the accuracy of the calculation of the actual machine angle can be improved by comparison with the actual signal on the rotary encoder. Therefore, for calculating the activation signal, the machine controller uses not only the model value of this machine angle of the respective threading cylinder, but also at least one machine angle actually measured by a rotary encoder present in the printing press. This approach can be improved by using an additional rotary encoder, but has the following disadvantages: the use of a plurality of rotary encoders results in corresponding costs. If a plurality of rotary encoders are to be used, it has proven advantageous if the rotary encoder closest to the threading cylinder, the measuring sensor of which is to be actuated by the activation signal, is evaluated for calculating the correct point in time for the emission of the activation signal.

It is also advantageously provided that the controller of the sheet-fed printing press takes into account the printing speed, the load state or the drive torque of the sheet-fed printing press when calculating the correct time for the activation signal. Naturally, all three conditions can also be considered simultaneously. The printing speed, the load state or the drive torque is entered into a torque model of the machine controller and used to calculate the torque state of the lead cylinder or cylinders as accurately as possible. The rotational speed in a printing press is largely dependent on the printing speed, the load state of the printing press and the drive torque of the printing press. It is therefore important to take these effects into account in the torsion model in order to be able to accurately calculate the torsion state of the printing press.

In a further embodiment of the invention, a deviation from the measured angle is determined in a learning process (Lernlauf) of the sheet-fed printing press, which corresponds to a difference between the measured angle at the time of the activation signal and the actual deviated measured angle in the learning process, and a correction value counteracting the difference is calculated and stored in the control unit. During this learning process, the machine runs idle without the substrate and the measuring sensor continues to detect at a fixed measuring rate: whether an object or reflector is identified. In this case, the transition from the state "unrecognized object" to the state "recognized object" defines the drum edge (or the position of the reflector of the measuring sensor). Since the reflector is arranged in the channel, the measurement angle is approximately 1 ° in front of the cylinder edge in order to detect a sheet projection in the gripper. For accuracy reasons, the machine can either rotate slowly or run the motion in small steps during the learning process. At the end of the learning process, the controller has detected the difference between the activation signal of the sensor and the measured position in units of machine angle "degrees" for all printing mechanisms. In this case, the deviation of the measured angle is taken into account with respect to the difference in time, which is dependent on the printing speed, the difference in time being determined by the machine controller. The machine controller is therefore programmed in such a way that, when the machine speed changes, the current value is calculated accordingly for this difference in time in order to ensure that the activation signal is triggered correctly.

Drawings

The invention will be further described and elucidated with reference to the following figures. The figures show:

FIG. 1 a: a sheet sensor and an activation sensor according to the prior art, wherein a sheet is detected;

FIG. 1 b: a sheet sensor and an activation sensor according to the prior art, wherein no sheet is detected;

FIG. 2 a: a sheet sensor having a premature activation signal, the sheet sensor not recognizing a sheet;

FIG. 2 b: a sheet sensor with an excessively late activation signal, which always recognizes the object; and

FIG. 3: according to the invention, the arrangement component comprises a sheet sensor which is triggered by an activation signal of the machine controller.

Detailed Description

Fig. 1a shows an example of a printing unit 7 of a sheet-fed printing press, which prints on a sheet-shaped printing material 5. The printing unit 7 of fig. 1a has a sheet position sensor 1, which sheet position sensor 1 is triggered by activation of a sensor 3 according to the prior art. The activation sensor 3 can be moved in the direction of the arrow in order to set the correct trigger time, so that a calibration (Justage) can be carried out. However, such calibration is time consuming and should be avoided. In the printing unit 7, the sheet position sensor 1 monitors the presence of the sheet 5 on the impression cylinder 2. For this purpose, a reflective surface 4 is provided in the path of the impression cylinder 2, in which path a sheet gripper for holding a sheet 5 is also provided, the reflective surface 4 being detectable by a stationary sheet position sensor 1. If the sheet position sensor 1 is an ultrasonic sensor, only the reflection surface 4 is required. In the case of using an optical sensor as the sheet position sensor 1, the reflection surface 4 is not required. In this case, if no sheet 5 is present, the sheet position sensor 1 receives either the light reflected by the sheet 5 or the light reflected by the cylinder background. Since the background reflection differs from the reflection of the sheet 5 in terms of intensity and direction, the sheet position sensor 1 can thus recognize the presence of the sheet 5. If a sheet 5 is located between the sheet position sensor 1 and the reflection surface 4, a corresponding signal is detected, which corresponds to the sheet 5 present. This state can be seen in fig. 1 b: no sheet 5 is present and thus no sheet 5 is present between the sheet position sensor 1 and the reflection surface 4 at the time point when this measuring sensor 1 is activated by the activation sensor 3.

Shown in fig. 2a and 2 b: what happens if the detection point in time is realized too early or delayed depending on the activation angle alpha. If the activation angle α is smaller than the actual correct measurement angle, the sheet position sensor 1 measures prematurely and unproductively, since the sheet position sensor 1 does not detect the sheet 5 via the reflection surface 4. In this case, the sheet position sensor 1 signals the missing sheet 5, even if the sheet 5 is actually present correctly on the impression cylinder 2. If the activation angle α is greater than the actual measurement angle, the measurement signal of the sheet position sensor 1, even in the absence of a sheet 5, does not reach the reflection surface 4 in order to signal the absence of a sheet, but rather reaches the cylinder surface of the impression cylinder 2, which leads to the recognition of a completely absent object. In this case, the sheet position sensor 1 detects the sheet 5 even if the sheet 5 is not present, since the sheet position sensor 1 cannot detect the empty reflection surface 4.

Fig. 3 shows a printing unit 7 of a sheet-fed printing press, which printing unit 7 has all components for carrying out the method according to the invention. Instead of the activation sensor 3, in fig. 3 the sheet position sensor 1 is merely coupled to the machine controller 6 and a corresponding activation signal is obtained by the machine controller 6. Additionally, in fig. 3, a rotary encoder 8 is provided in the printing unit 7, the rotary encoder 8 being used for: the torsion pattern present in the machine controller 6 is supplied with at least one actually measured machine angle of the sheet printing press. For this purpose, the rotary encoder 8 is likewise coupled to the machine controller 6. The machine controller 6 calculates the time at which the activation signal is emitted to the sheet position sensor 1 by means of a torsion model stored in the machine controller 6 in software and taking into account the machine angle of the rotary encoder 8. At this point in time, the measurement signal of the sheet position sensor 1 then arrives directly at the opposite reflection surface 4 on the impression cylinder 2 without the sheet 5 being present. In this case, the missing page is notified to the machine controller 6. In the case of a correct presence of a sheet 5, the signal of the sheet position sensor 1 does not reach the empty reflection surface 4, but rather detects the sheet 5 between the sheet position sensor 1 and the reflection surface 4, as is shown in fig. 1 in connection with the prior art.

Unlike fig. 1a and 1b, however, in fig. 3, the activation sensor 3 is no longer necessary, since the activation signal is generated only by the machine controller 6. The correct activation angle α is also taken into account by the machine controller 6, as are other influencing variables of the machine. In the machine control 6, the operating time of the signals of the sheet position sensor 1 is known and stored in each case, so that the signal operating time can likewise be taken into account in order to ensure the earlier triggering of the activation signal, which is necessary depending on the signal operating time. This is required in particular when ultrasonic sensors are used, since the measuring position continues to move by approximately 1 mm during the propagation of the sound waves due to the rotation of the impression cylinder 2. This means that, in particular at high speeds, a missing sheet 5 is no longer reliably detected. However, this enables the presence or absence of a missing sheet to be detected with high accuracy even in the above case, taking into account the operating time of the ultrasonic signal of the sheet position sensor 1.

The sheet-fed printing press can have a plurality of printing units 7, wherein one or more sheet position sensors 1 can be provided in each printing unit for detecting the sheets 5 on a sheet-guiding cylinder (e.g., impression cylinder 2). Here, however, it is not necessary to provide a rotary encoder 8 on each printing unit 7, but it suffices that: if the rotary encoder 8 is present in the machine, the signal of the rotary encoder 8 is supplied to the machine controller 6. For each cylinder to be monitored, the machine controller 6 then determines the respective machine angle in each printing unit 7 using the torsion model, and from this the correct triggering time for the respective activation signal can be calculated from the machine angle calculated for each sheet position sensor 1 and each printing unit 7. Thus, with the rotary encoder 8 and the machine controller 6: the appropriate activation signals are calculated correctly for the plurality of sheet position sensors 1 in the plurality of printing units 7.

List of reference numerals:

1 sheet position sensor

2 opposite pressing rollers

3 activating the sensor

4 reflective surface

5 pages

6 machine controller

7 printing mechanism

8 Rotary encoder

Angle of alpha activation

Claims

1. A method for detecting a missing sheet in a printing unit (7) of a sheet printing press by means of a measuring sensor (1) which detects a sheet (5) on a guide cylinder (2), wherein the detection of the sheet (5) is carried out by the measuring sensor (1) on the basis of an activation signal,

it is characterized in that the preparation method is characterized in that,

the activation signal is emitted by a controller (6) of the sheet printing press, wherein the controller (6) calculates a correct time point for emitting the activation signal taking into account at least a torsion state of the guide roller (2), such that the activation signal is emitted to the measuring sensor (1) at the correct time point for controlling the measuring sensor (1) to correctly trigger a detection process for missing sheets, and

the controller (6) takes into account the operating time of the measurement signal of the measurement sensor (1) when calculating the correct time for the emission of the activation signal and triggers the time of the activation signal accordingly early.

2. The method of claim 1, wherein the first and second light sources are selected from the group consisting of,

it is characterized in that the preparation method is characterized in that,

the controller (6) uses a torsion model for calculating the activation signal taking into account at least the torsion state of the guide cylinder (2), which torsion model is stored as a control program in the controller (6) of the sheet-fed printing press.

3. The method of claim 2, wherein the first and second light sources are selected from the group consisting of,

it is characterized in that the preparation method is characterized in that,

in addition to the torsional state of the guide cylinder (2), the torsional model also takes into account the torsional state of a further cylinder in the sheet-fed printing press, which is mechanically coupled to the guide cylinder (2).

4. The method according to one of claims 1 to 3,

it is characterized in that the preparation method is characterized in that,

the measuring sensor (1) is an ultrasonic sensor, and the guide roller (2) has a reflection surface (4) for reflecting a measuring signal of the ultrasonic sensor (1).

5. The method according to one of claims 1 to 3,

it is characterized in that the preparation method is characterized in that,

the controller (6) detects the machine angle, which is supplied to the controller (6) by at least one rotary encoder (8) in the sheet-fed printing press, when calculating the correct point in time for issuing the activation signal.

6. The method of claim 5, wherein the first and second light sources are selected from the group consisting of,

it is characterized in that the preparation method is characterized in that,

the sheet printing machine has a plurality of rotary encoders (8), an

The machine angle detected by the rotary encoder (8) closest to the threading cylinder (2) is used in the calculation of the correct point in time for the emission of the activation signal.

7. The method according to one of claims 1 to 3,

it is characterized in that the preparation method is characterized in that,

the controller (6) of the sheet-fed printing press takes into account the following when calculating the correct time for the emission of the activation signal: the printing speed, the load state or the drive torque of the sheet-fed printing press.

8. The method according to one of claims 1 to 3,

it is characterized in that the preparation method is characterized in that,

in a learning process of the sheet-fed printing press, a deviation from the measured angle (alpha) is determined, which corresponds to a difference between the measured angle (alpha) at the time of the activation signal of the measuring sensor (1) and the actually deviated measured angle (alpha) in the learning process, and a correction value counteracting the difference is calculated and stored in a controller (6).

9. The method of claim 8, wherein the first and second light sources are selected from the group consisting of,

it is characterized in that the preparation method is characterized in that,

the correction value is calculated by the controller (6) according to the printing speed.