DE102022110168B3 - Functional monitoring of conveyor belts in the printing press - Google Patents

Abstract

The invention relates to a method for monitoring the wear of conveyor belt devices (6, 19) in the sheet delivery (4) or sheet feeder (16) of a printing press (1) using a computer (15). The invention is characterized in that the computer (15) is supplied with an actual value for the speed or the angle of rotation of the main drive shaft (14) of the printing machine (1), that the computer (15) receives an actual value for a speed (9th , 20) or an angle of rotation of the conveyor belt device (6, 19) and that the computer (15) from deviations between the actual value of the speed or the angle of rotation of the main drive shaft (14) and the actual value of the speed or the angle of rotation of the Conveyor belt device (9, 20) detects differences and calculates the current state of wear of the conveyor belt device (6, 19) from the differences.

Description

The present invention relates to a method for monitoring the wear of conveyor belt devices in the sheet delivery or sheet feeder of a printing press using a computer.

Conveyor belt devices in printing presses are subject to constant wear and tear, which means that there is constantly increasing slippage between the conveyor belt itself and the wheels or shafts carrying the conveyor belt. This slip results from the wear of the conveyor belt and the wear of the wheels or shafts, since the surfaces wear out due to constant rubbing against each other. Over time, this increases the risk that the forces from the conveyor belt to the wheels or vice versa can no longer be properly transmitted due to the increased slip and the wheels increasingly begin to slip. Reliable control of the conveyor belt is then no longer possible, since the conveyor belt device slipping makes precise control impossible. In practice, the operator of a printing press must ensure in good time that the wearing conveyor belts or wheels or shafts in the conveyor belt device are replaced.

Another possibility comes from the disclosure document DE 10 2011 087 627 A1 out, there the wear of a conveyor belt device in a sheet brake is compensated for by an automatic spring adjustment. The disadvantage of this procedure is that at some point the wear is so high that the conveyor belt can tear or the force of the spring for adjustment is no longer sufficient due to the excessive wear and there is still a risk of the conveyor belt slipping.

Based on the state of the art, the task therefore arises of creating a method for monitoring the wear of conveyor belt devices in the sheet delivery or sheet feeder of a printing press with a computer, which can reliably and at any time determine the current state of wear of the conveyor belt device and thus, in particular, preventive measures for Avoidance of the failure of the conveyor belt device allowed in time.

This object is achieved by patent claim 1 according to the invention. Embodiments according to the invention result from the dependent patent claims, the description and the figures.

The solution according to the invention is particularly suitable for use in conveyor belt devices in the sheet delivery or sheet feeder of a printing press. Such a conveyor belt device in the sheet delivery are the sheet brakes used there, which consist of conveyor belts on friction wheels. In the sheet feeder there is such a conveyor belt device in the form of a suction conveyor belt, which is also driven by friction wheels and conveys the sheet-like printing materials from the feeder stack into the first printing unit of the printing press. With both conveyor belt devices, it is important that the conveyor belts can be precisely controlled and not slip on the friction wheels. According to the invention, it is provided that the computer is supplied with an actual variable for the speed or the angle of rotation of the main drive shaft of the printing press, that the computer is supplied with an actual variable for a speed or an angle of rotation of the conveyor belt device and that the computer calculates deviations between the actual Size of the speed or the angle of rotation of the main drive shaft and the actual size of the speed or the angle of rotation of the conveyor belt device detected as differences and calculated from the differences the current state of wear of the conveyor belt device. In this case, the computer carries out a comparison of the speed or the angle of rotation of the main drive shaft with the speed or the angle of rotation of the conveyor belt device, which are in a constructively determined relationship to one another. With increasing wear, this ratio changes, which is recorded as a difference by the computer. The greater this difference, the greater the wear. The computer can then use the difference to recognize how great the wear is and thus calculate the current state of wear of the conveyor belt device. Basically, the present invention works both with detected speeds and detected angles of rotation.

In a first embodiment of the present invention, it is provided that the computer calculates these differences at specific time intervals and calculates the failure time of the conveyor belt device from the trend of the increasing differences. In this embodiment of the invention, it is provided that the differences are calculated at predetermined time intervals and the differences calculated at the time intervals are compared with one another. In this way, a trend can be identified, in particular deviations from a linear deterioration can be identified in good time, which indicates a sharp increase in wear. The progression of this trend allows the calculation of the point in time when the differences are so large that failure of the conveyor belt device is imminent. This point in time can then be used to service the conveyor belt device in good time and to replace the conveyor belt and/or the friction wheels in good time, so that a failure of the conveyor belt device and thus a standstill of the printing press can be avoided. The time intervals are advantageously created in such a way that the changing differences are recognized in good time, but unnecessary computing processes are avoided.

In a further embodiment of the present invention, a speed sensor or angle of rotation sensor for detecting the actual size of the main drive shaft is arranged on the main drive shaft of the printing press or on a cylinder coupled to the main drive shaft on a printing unit of the printing press. A sensor that is already present in the printing press can usually be used for this purpose, since the speed or the angle of rotation of the main drive shaft of the printing press is important for controlling the speed of the drive motor of the printing press during printing in order to be able to ensure reliable printing operation. However, the sensor does not necessarily have to be located on the main drive shaft of the printing press itself; it is sufficient if it is arranged on a cylinder coupled to the main drive shaft in a printing unit of the printing press. In printing operation, there is almost no play between the individual cylinders of the printing press due to the necessary tension, so that it is completely sufficient for accuracy if the sensor is seated on a cylinder coupled to the main drive shaft. In this way, the actual speed or the actual angle of rotation of the main drive shaft can be reliably detected in any case.

Furthermore, it is provided that the calculation of the state of wear is triggered by the computer after a specific number of pulses from the rotation angle sensor of the main drive shaft. The time intervals after which the calculation of the current state of wear of the conveyor belt device must be carried out by the computer of the printing press can be determined via the predetermined number of pulses of the angle of rotation sensor.

Advantageously, it is also provided that the conveyor belt device is a sheet brake, that the printing press has several brake modules of one or more sheet brakes in the sheet delivery and that these brake modules are equipped with sensors that detect the speed or the angle of rotation in the brake module. By equipping each brake module with a speed sensor, the actual speed in each brake module can be reliably recorded by the computer on the printing machine and the current state of wear can be calculated by comparing the actual speed of a brake module with the actual speed of the main drive shaft. In this way, the current state of wear can be precisely calculated individually for each brake module of a sheet brake.

It is advantageously provided that after the calculation of the state of wear has been initiated, pulses of the main drive shaft are corrected with the pulses of the rotation angle sensor of the conveyor belt device and the respective diameter ratio is thus taken into account. Since the speed of the main drive shaft and the speed of the conveyor belt device are different due to the different diameters of the rotating components, a correction must be made to compare the rotation angles of the main drive shaft and the conveyor belt device in order to take the respective diameter ratio into account. Only then can the differences in the angles of rotation be calculated correctly and the current state of wear correctly recorded. The same applies when recording the speeds, here too the different speeds must be set in relation. As long as the ratio remains constant, there is no wear. With wear, the ratio changes, which is therefore an indicator of wear.

In a further embodiment of the invention, it is provided that after the calculation of the state of wear has been initiated, the counter for the main drive shaft in the computer is reset to zero. In this way it is ensured that the next calculation of the state of wear is reliably started again.

Furthermore, it is provided that when the state of wear exceeds a permissible limit, the computer issues a service message and/or initiates a service call for a printing press. This permissible limit of the state of wear is so far below the failure limit of the conveyor belt device that the failure of the conveyor belt device can be avoided by servicing it in good time. A service message can be displayed on a screen of the printing press itself, so that the operator of the printing press can carry out the maintenance of the conveyor belt device himself in good time, or a service call can be initiated automatically at a service company directly via a remote maintenance device and the Internet, which is then carried out in good time visits the print shop and waits for the printing press, thus preventing a failure of the conveyor belt device and thus of the printing press.

In a particularly advantageous embodiment of the present invention, the brake modules of a sheet brake have a number of friction wheels, these friction wheels each having their own speed sensor. In this way, the wear of individual friction wheels, each of which has a speed sensor, can be detected particularly precisely, so that individual friction wheels can also be replaced in good time.

In a further embodiment of the present invention, it is provided that the brake modules of the sheet brake are variable or removable and that the computer queries the current configuration of the sheet brake before each start-up of the printing press via special sensors or by querying the presence of the speed sensors in the brake modules of the sheet brake and taken into account when detecting the state of wear. Depending on how many sheet brakes are currently in use depending on the printed format of the sheets processed in the printing press, the load on the brake modules of the sheet brake varies. However, it is not irrelevant for determining the probability of failure of the conveyor belt device, since brake modules of the sheet brake, which are rarely used, are subject to less wear than brake modules of the sheet brake, which are used frequently. Since the speed sensors in the brake modules are connected to the computer on the printing press, the current configuration of the sheet brake can be easily queried before each start-up of the printing press by querying the presence of the speed sensors, and the current configuration of the sheet brake can thus be taken into account when determining wear.

• 1 den Ausleger einer Bogendruckmaschine mit einer erfindungsgemäßen Überwachungseinrichtung der Bogenbremse,
• 2 mehrere Bremsmodule einer Bogenbremse und
• 3 eine Bogendruckmaschine mit einem Anleger, der eine Überwachungseinrichtung zur Ermittlung des Verschleißzustands des Saugbändertisches aufweist.

The present invention is described and explained in more detail below with reference to several figures. Show it:

• 1 the delivery of a sheet-fed printing press with a sheet brake monitoring device according to the invention,
• 2 several brake modules of a sheet brake and
• 3 a sheet-fed printing press with a feeder that has a monitoring device for determining the state of wear of the suction belt table.

In 1 shows the area of the sheet delivery 4 of a printing press 1, which has one or more printing units 3. The sheet delivery device 4 is arranged at the exit of the last printing unit 3 and takes over the sheets 2 of the last printing unit 3 by means of a chain conveyor 5 and conveys them into the area of the delivery above the sheet stack 7 . In order to enable the sheets 2 to be deposited correctly on the sheet stack 7, sheet brakes 6 are arranged in the boom 4, with these sheet brakes 6 comprising a plurality of brake units 6.1, 6.2, 6.3 over the entire width of the boom 4. These braking units 6.1, 6.2, 6.3 are used depending on the format of the sheet 2 used. Unused braking units 6.1, 6.2, 6.3 can be switched off or removed from the sheet delivery 4. At least one sensor 9 is arranged in the area of each sheet brake 6 and detects the speed of the respective sheet brake 6 . A speed sensor 14 is in turn arranged on a cylinder in the printing units 3 and directly or indirectly detects the speed of the main drive shaft of the printing press 1 . The signals from the sensors 14, 9 are fed to a control computer 15 of the printing machine 1, where the speeds are compared with one another. If the ratio of the speeds to one another changes, the computer 15 registers these differences, which represent a measure of the wear on the rollers and belts of the sheet brake 6. Furthermore, a suction chamber 10 is present in the sheet delivery device 4, which stabilizes the sheet 2 during sheet transport. For example, inexpensive inductive or Hall effect sensors can be used as sensors 9 . The drive shaft and the friction wheels are equipped with one or more so-called measuring lugs. During one revolution of the respective wheel, the corresponding sensor 9 supplies one measuring pulse per flag and revolution. These pulses can be detected by a suitable evaluation unit and then stored in the computer 15 with a time stamp.

The wear of the brake modules 6.1, 6.2, 6.3 can be attributed to a relative movement between the central drive shaft and the friction wheel, ie the slip there. This slip results from the forces that occur in the contact area between shaft and wheel as a result of the highly dynamic changes in speed.

• - im Rechner 15 befinden sich die abgelegten Daten, jeder Sensor 9 entspricht einem Messkanal
• - die Impulse jedes Messkanals werden kontinuierlich addiert/gezählt
• - wenn der Messkanal des Sensors 14 der Antriebswelle eine bestimmte Anzahl von Impulsen aufweist (z.B. 1e4), wird die Berechnung der eigentlichen Verschleißkenngröße angestoßen:
  • ◯ Die Verschleißkenngröße eines einzelnen Bremsmoduls 6.1, 6.2, 6.3 entspricht dem Verhältnis der Anzahl der Impulse der Antriebswelle zur Anzahl der Impulse der zugehörigen getrieben Welle
  • o Solange kein oder nur geringer Schlupf vorhanden ist, bildet die Verschleißgröße in etwa das Durchmesserverhältnis von zentraler Antriebswelle und Reibrad ab, korrigiert um das Verhältnis der jeweiligen Messfahnen. Bei zunehmendem Schlupf wird der Wert der Verschleißgröße zunehmend größer.
  • ◯ die Sensitivität der Verschleißgröße lässt sich durch die Anzahl der Messfahnen und die Anzahl der gezählten Umdrehungen bis Berechnungsstart beeinflussen
  • ◯ nach angestoßener Berechnung wird der Zähler der Antriebswelle wieder zu 0 gesetzt

The preferred and simplest embodiment of this invention provides that the pulses recorded from the central drive shaft and the respective brake modules 6.1, 6.2, 6.3 are used to calculate a simple wear parameter. This is determined as follows:

• - The computer 15 contains the stored data, each sensor 9 corresponds to a measuring channel
• - the pulses of each measuring channel are continuously added/counted
• - if the measuring channel of the sensor 14 of the drive shaft has a certain number of pulses (eg 1e4), the calculation the actual wear parameter triggered:
  • ◯ The wear parameter of an individual brake module 6.1, 6.2, 6.3 corresponds to the ratio of the number of pulses from the drive shaft to the number of pulses from the associated driven shaft
  • o As long as there is no or only little slip, the wear value roughly represents the diameter ratio of the central drive shaft and the friction wheel, corrected by the ratio of the respective measuring lugs. With increasing slip, the value of the wear variable becomes increasingly larger.
  • ◯ the sensitivity of the wear variable can be influenced by the number of measuring lugs and the number of revolutions counted before the start of the calculation
  • ◯ After the calculation has been triggered, the drive shaft counter is set to 0 again

This wear variable represents a measure of the average slip over a number of operating cycles. Decisions can now be made on the basis of this variable. This means that if the size exceeds a certain level, a message is issued and a service call is initiated. The threshold can be selected in such a way that the onset of wear is detected and major damage and unplanned production downtime are avoided.

Since the number of brake modules 6.1, 6.2, 6.3 that are currently used can vary from print job to print job, in some cases they are even expanded and the number of installed modules varies, it makes sense to follow the process described above for each brake module 6.1, 6.2, 6.3 to go through individually. In this way, the number of wear could always be determined when the corresponding brake module 6.1 has the required number of pulses. Especially with double assembly, one friction wheel often stops. Here, the adjacent friction wheels must be queried separately. The computer 15 should automatically recognize which brake modules 6.1, 6.2, 6.3 are currently in use, or it should be possible for the operator to make appropriate entries in order to select and deselect the modules.

Instead of controlling the calculation of the amount of wear over the cycles, it could also be time-controlled. However, the quality of the measured value then decreases considerably, since the accuracy depends on the number of pulses in question and rounding effects then occur. Instead of instrumenting the drive shaft with a sensor 14, the number of printed sheets 2 or the machine revolutions of the boom 4 could be used to count the drive cycles. Instead of instrumenting the drive shaft with a sensor 14, a comparison of the brake modules 6.1, 6.2, 6.3 with one another could also serve as a slip indicator. Encoders or speed sensors could also be used. The pulse generators could also be designed optically.

The brake bands 11 usually have a certain number of holes located along the middle of the band. An optical sensor 9 could be used to detect the holes in the tape. In addition to the speed monitoring, temperature and/or vibration monitoring could take place and provide further data that could be incorporated into a more complex damage model or a so-called big data analysis. The wear indicators could be recorded centrally for the entire machine population. On the basis of this data and, if necessary, with the help of modern methods, such as so-called big data analyses, it is then possible to carry out predictive maintenance, so that the service life of the components, as well as work processes and downtimes of the printing press 1 can be planned and optimized. If other factors are included in such big data analyses, such as just the pure wear parameter of the respective brake unit 6, individual forecasts can be created for each brake unit 6 and printing machine 1. For example, the life expectancy of the braking unit will also depend on the number of sheets 2 braked and their specific properties. It may make sense not to measure constantly during operation. It is possible that slippage occurs here, since the friction wheels go into generator operation due to the sucked sheet.

Here, in a test phase in which the printing press 1 is running but no paper is running and the sheet brake 6 is turning, it can be checked whether all the friction wheels are turning evenly.

In 2 the sheet brake 6 is off 1 shown enlarged so that it is easier to see that the sheet brake 6 consists of several braking units 6.1, 6.2, 6.3, which are distributed over the entire format width of a sheet 2. 2 also shows how the brake bands 11 of the brake units 6.1, 6.2, 6.3 are actuated in order to brake the sheets 2 in the delivery 4. The braking process is initiated via the drive shaft 8, which extends over the entire width of the boom 4 and is in contact with the respective brake band 11. Thus, in each brake unit 6.1, 6.2, 6.3, the respective brake band 11 is guided via the drive shaft 8 with running wheels of the brake units 6.1, 6.2, 6.3. In addition, on each brake Unit 6.1, 6.2, 6.3 has a speed sensor attached, which records the speed of an impeller and thus provides a measure of the wear. It can be seen that several sensors 9 can also be present per brake unit 6.1, 6.2, 6.3 in order to be able to detect each individual running wheel of the brake unit 6.1, 6.2, 6.3. This allows a precise prediction of the wear of each brake unit 6.1, 6.2, 6.3. Furthermore, in 2 a safety device 13 can be seen, by means of which the respective brake unit 6.1, 6.2, 6.3 can be positioned safely and immovably. By opening the safety device 13, it is possible to move a braking unit 6.1, 6.2, 6.3 or to remove it entirely. Brake modules 6.1, 6.2, 6.3 are basically constructed in such a way that a closed brake band 11 is stretched between several rollers and runs around them. One of these rollers is the drive roller of the brake module 6.1, which has an axially offset friction wheel that is connected to it in a rotationally fixed manner. The friction wheel is pressed against the central drive shaft and transmits its rotary motion to the brake module. A layer of rubber is applied to the circumference of the friction wheel to improve power transmission between the friction wheel and the central drive shaft.

The sheet brake 6 serves to decelerate the printed sheets 2 that run into the delivery 4 from machine speed to a speed that enables good stack formation in the delivery 4 . The speed of the sheet brake 6 changes constantly since it constantly alternates between machine speed and (almost) standstill. These are highly dynamic speed changes and thus place a corresponding load on the components in the power flow. This leads to relative movements, i.e. slip, between the central drive shaft and the force-transmitting rubber layer of the friction wheel. This slip increasingly causes wear, essentially on the rubber layer that is applied to the friction wheel. If wear and tear is not recognized and remedied in good time, it can even happen that the main body of the friction wheel and also the central drive shaft are damaged in such a way that they become unusable and have to be replaced. This entails higher costs and longer and unplanned downtimes of the printing machine 1. If wear and tear is detected at an early stage, the repairs are cheaper on the one hand and on the other hand the service calls at the customer's can be planned together with them.

Another embodiment of the present invention is 3 can be seen here, in addition to monitoring the wear of the sheet brakes 6 in the boom 4, a monitoring of the wear of the suction belt 19 in the sheet feeder 16 before the first printing unit 3 of the printing press 1 is provided. In the sheet feeder 16, sheets 2 are removed from the sheet stack 7 by means of suction heads 18 and conveyed to the first printing unit 3 via a suction belt 19. The suction belt 19 is also driven via rollers, which can wear out. The height of the stack of sheets 7 in the feeder 16 is recorded using a feeler foot 17 . A speed sensor 20 is arranged on the suction belt 19, which detects the speed of the suction belt 19 and can thus detect wear on the suction belt 19 or the drive rollers of the suction belt 19, in that the speed sensor 20 forwards the respective actual speed to the control computer 15 and the Control computer 15 in turn compares this speed with the actual speed of the speed sensor of the main drive shaft 14 . The wear of the suction belt 19 or the sheet brakes 6 can be displayed to the operator of the printing machine 1 on the operating screen 21 of the printing machine 1, so that he can change the wearing parts himself in good time or call a service to prevent a failure of the printing machine 1.

In principle, the speed of the drive roller of the suction belt 19 in the feeder 16 is known; the drive roller rotates in a known transmission ratio to the speed of the printing machine, which the sensor 14 measures. If the speed of a freely rotating roller (deflection roller, tensioning roller) on the suction belt 19 is monitored, e.g. via a rotary encoder 20 or e.g. via the continuous hole pattern of the suction belt 19 with an optical sensor, this shows a suction belt running slower over time compared to the speed of the drive roller 19 an increasing slip and thus wear of the suction belt 19. It is also possible to monitor the sheet arrival at the feed marks of the printing press 1 and to intervene to correct deviations from the optimal point in time. In the case of mechanically coupled feeders 16, this takes place via a phase adjustment of the feeder 16 in relation to the printing machine 1. In the case of a motor-driven individual drive of the suction belt 19, this can take place via a change in the speed of the drive. If one observes the required correction of the sheet arrival over a longer period of time and recognizes that the required correction is increasing, this is a sign of wear on the suction belt 19, since the transport path of the suction belt 19 per revolution of the drive decreases, which increases the need for correction.

Reference List

1

printing press

2

arc

3

printing unit

4

bow boom

5

chain conveyor

6

sheet brake

6.1, 6.2, 6.3

braking units

7

stack of sheets

8th

drive shaft

9

Sensor on the sheet brake

10

suction chamber

11

brake band

12

suction port

13

security device

14

Main drive shaft speed sensor

15

control computer

16

sheet feeder

17

touch foot

18

suction head

19

suction belt

20

Speed sensor on the suction belt

21

operating screen

Claims (11)

Method for monitoring the wear of conveyor belt devices (6, 19) in the sheet delivery (4) or sheet feeder (16) of a printing press (1) with a computer (15), characterized in that the computer (15) receives an actual value for the speed or the angle of rotation of the main drive shaft (14) of the printing press (1) is supplied, that the computer (15) is supplied with an actual value of a speed (9, 20) or of a rotation angle of the conveyor belt device (6, 19) and that the computer ( 15) differences are detected from deviations between the actual value of the speed or the angle of rotation of the main drive shaft (14) and the actual value of the speed or the angle of rotation of the conveyor belt device (9, 20) and the current state of wear of the conveyor belt device (6, 19) calculated. procedure after claim 1 , characterized in that the computer (1) calculates these differences at specific time intervals and calculates the failure time of the conveyor belt device (6, 19) from the trend of the increasing differences. Method according to one of the preceding claims, characterized in that a rotational angle sensor (14) for detecting the actual size of the Main drive shaft is arranged. procedure after claim 3 , characterized in that the calculation of the state of wear by the computer (5) is initiated after a specific number of pulses from the rotation angle sensor (14) of the main drive shaft. Method according to one of the preceding claims, characterized in that the conveyor belt device is a sheet brake (6), that the printing press (1) has several brake modules (6.1, 6.2, 6.3) of one or more sheet brakes (6) in the sheet delivery (4) and that these brake modules (6.1, 6.2, 6.3) are equipped with sensors (9) which detect the speed or the angle of rotation in the brake module (6.1, 6.2, 6.3). procedure after claim 4 or 5 , characterized in that after initiating the calculation of the state of wear, pulses of the main drive shaft are corrected with the pulses of the rotation angle sensor (9, 20) of the conveyor belt device (6, 19) and the respective diameter ratio is thus taken into account. Procedure according to one of Claims 4 until 6 , characterized in that after the calculation of the state of wear has been initiated, the counter in the computer (15) for the main drive shaft is reset to zero. Method according to one of the preceding claims, characterized in that when the state of wear exceeds a permissible limit, the computer (15) issues a service message and/or initiates a service call on the printing press (1). Procedure according to one of Claims 5 until 8th , characterized in that the brake modules (6.1, 6.2, 6.3) of the sheet brake (6) have a plurality of friction wheels and that these friction wheels each have a rotation angle sensor (9). Procedure according to one of Claims 5 until 9 , characterized in that the brake modules (6.1, 6.2, 6.3) of the sheet brake (6) are variable or removable and in that the computer (15) reads the current configuration of the sheet brake (6) before each start-up of the printing press (1) via special sensors or querying the presence of the rotation angle sensors (9) in the braking modules (6.1, 6.2, 6.3) of the sheet brake (6) and taken into account when detecting the state of wear. Method according to one of the preceding claims, characterized in that the computer (15) shows the operator of the printing press (1) the current state of wear of the conveyor belt device (6, 19) on a screen (21).

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