The present invention relates generally to a method for controlling operation of a printing press, and particularly, to a sheet-fed offset printing press.
From DE 101 15 546 A1 a method is known for operating a printing press, in particular a sheet-fed offset printing press, in which two drives, whose positions can be controlled independently from each other, feed into a continuous gear train of the printing press. In this regard, the devices of the printing press to be driven and coupled to the gear train are driven specifically in a manner such that rotation of the gear train is effected between the feed sites of the drives acting on the continuous gear train.
According to DE 101 15 546 A1, a rotational angle position of the continuous gear train is measured at two different positions thereof, and the position of the drive acting on the continuous gear train is adjusted as a function of a rotational angle difference obtained from the measured rotational angle positions. According to this prior art, a rotational angle difference control is established which is based on a rotational angle difference determined by measurement in the gear train.
It is an object of the present invention to provide a method for more efficiently controlling the operation of a printing press, and particularly a sheet fed printing press, for improved print quality.
According to the invention, a desired torque distribution for the drives feeding into the continuous gear train is determined such that each drive provides a driving torque for a sub-unit associated with the same and furthermore for a sub-unit associated with a drive connected downstream of the respective drive, wherein based on said torque distribution for each drive an individual angle target value is determined, which is used to control the position of each drive individually in order to provide an angular difference that is dependent on the torque distribution between the feed sites of the drives.
With respect to the inventive method, sensors to measure a rotational angle difference are now no longer needed. Therefore, costs can be reduced. Furthermore, a position control of drives feeding to the continuous gear train is possible on the basis of a preferred torque distribution of the continuous gear train so that the print quality can be improved.
Preferably, in order to determine the desired torque distribution between the drives driven in the continuous gear train, a torque requirement for each drive is calculated or is determined experimentally such that the drive on the one hand covers the torque requirement of the sub-unit allocated thereto, and on the other hand covers a portion of the torque requirement of the same downstream sub-unit to which a separate drive is allocated.
To determine the individual angle target value for each drive, an angle difference between the feed sites of the drives is changed experimentally until the previously determined, desired torque distribution is obtained, wherein the determined angle values of the drives are saved as angle target values.
According to a further favorable embodiment of the invention, given an individual position control of the drives, the torque distribution actually occurring during the position control is determined, and wherein in this regard a check is made to ascertain whether the actually occurring torque distribution is within a tolerance band defined by an upper limit value and a lower limit value around the desired torque distribution, wherein then, if it is thereby determined that the actual torque distribution is within the tolerance band, the angle target values for position control of the drives remain unchanged, and then if it is thereby determined that the actual torque distribution is outside of the tolerance band, at least one angle target value is adjusted automatically for position control of one drive such that the actual torque distribution is again located within the tolerance band.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which:
While the invention is susceptible of various modifications and alternative constructions, a certain illustrative embodiment thereof has been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific form disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention.
The present invention relates to a method for operating a printing press, particularly a sheet-fed offset printing press, wherein at least two drives, whose positions can be controlled independently from each other, feed into a continuous gear train of the printing press. The method according to the invention is explained in detail below with reference to the sheet-fed offset printing press 10 illustrated in
The feeder 11 together with the first three printing presses 12, 13 and 14 form a first sub-unit 23 of the sheet-fed offset printing press. The printing presses 15, 16 and 17 form a second sub-unit 24 of the sheet-fed offset printing press 10. The printing presses 18, 19, 20 and 21 together with the delivery unit 22 form a third sub-unit 25 of the sheet-fed offset printing press 10. The feeder 11, the printing presses 12-21 and the delivery unit 22 each are driven devices of the sheet-fed offset printing press 10.
The sheet-fed offset printing press 10 in
Accordingly, in the embodiment in
The sub-units 23, 24 and 25 of the sheet-fed offset printing press 10 in
In carrying out the invention, for the drives feeding into the continuous gear train of the printing press, a desired torque distribution is defined in that each drive 26, 27 and 28 produces a drive torque, first for the sub-unit 23, 24 and 25, allocated thereto, and additionally for the drive downstream of the particular drive 26, 27 and 28. In the illustrated embodiment, this means that the drive 26 produces a drive torque for the sub-unit 23 and a drive torque for the sub-unit 24. The drive 27 produces a drive torque for sub-unit 24 and sub-unit 25. The drive 28 produces a drive torque for sub-unit 25. Based on the particular desired torque distribution for the drives 26, 27 and 28, an angle target value is determined individually for each drive; and based on this value, each drive 26, 27 and 28 can be individually position-controlled in order to provide an angular difference between the feed sites of the drive depending on the desired torque distribution.
To determine the desired torque distribution between the drives 26, 27 and 28 feeding into the continuous gear train, a torque requirement is determined experimentally or by calculation for each drive, namely such that the drive first covers the torque requirement of the sub-unit allocated thereto, and secondly covers a portion of the torque requirement of the sub-unit downstream thereof, which is allocated to the particular drive.
Arrows 29, 30 and 31 in
Based on the torque distribution determined experimentally or by calculation as indicated above, an angular difference between the feed sites of drives 26, 27 and 28, i.e., the drive shafts, is varied experimentally to determine the individual angle target value for the particular drives 26, 27 and 28, until the previously defined, desired torque distribution is adjusted. Thus angular values of the drives 26, 27 and 28 determined in this manner are saved as angle target values or as difference angles relative to a lead angle applicable to all sub-units. In the above determination of the individual angle target values for drives 26, 27 and 28 it is possible to vary the desired torque distribution and thus to save a characteristic line dependent on the angular difference and torque distribution for determining the individual angle target values.
The angle target values for the individual drives 26, 27 and 28 determined in the above manner are valid preferably for an operating mode of the sheet-fed offset printing press 10, for example, for continuous printing. In order to produce angle target values dependent on operating mode for other types of operation of sheet-fed offset printing presses, the angle target value of each drive can be corrected by an offset value depending on the operating mode, wherein separate offset values are kept ready for an acceleration and/or a deceleration and/or a change in direction of rotation and/or a set-up mode and/or for an adjustment of format length in first and second print mode of the sheet-fed offset printing press.
Accordingly, by means of the present invention it is possible to establish a position control for the drives feeding into a continuous gear train of a printing press in such a manner that a desired torque distribution of the drives is defined such that, based on the desired torque distribution, individual angle target values are determined for the drives and that based on these individual angle target values, each drive will be individually position-controlled, namely in a manner such that an angular difference depending on the torque distribution will form between the feed sites of the drives.
According to another desirable embodiment of the present invention, the torque distribution of the drives actually occurring is determined for the individual position control of the drives 26, 27 and 28, and specifically on the basis of the driving current of the drives 26, 27 and 28. In this case a check is made to determine whether the actually occurring torque distribution is within a tolerance band around the desired torque distribution, wherein the tolerance band around the desired torque distribution is defined by an upper limit value and by a lower limit value.
If it is thus determined that the actual torque distribution is within the tolerance band, then the angle target values for individual position control of the drives remain unchanged.
However, if it is then found that the actual torque distribution is outside of the tolerance band around the desired torque distribution, then at least one angle target value is changed automatically for position control of one drive, in such a manner that the actual torque distribution is again within the tolerance band around the desired torque distribution. This adjustment of the angle target value occurs in relatively small steps over a relatively long period of time.
The above continuous adaptation of angle target values takes place especially when a format length adjustment of the gear train of the sheet-fed offset printing press 10 takes place for the first- and second-print. In a format length adjustment in first- and second print operation, the gear train has to be opened in order to rotate the devices of the sheet-fed offset printing press used for driving in first-print mode, and in second print mode for the purpose of format adjustment, wherein after a subsequent closing of the gear train, the original torque distribution is not automatically present, but rather has to be established again, in steps, by means of a corresponding adaptation of the angle target values for the position control.
To produce a pre-control component for implementing of a change in direction of rotation, for each drive, individual angle target values can be adjusted, depending on the play between teeth of the gears which is present between the feed sites of the drives. In this manner, operation is possible with a suitable torque distribution during a reversal of the direction of rotation.
The advantage of the inventive method, which is based on a position control of the drives feeding into the continuous gear train, with respect to the method based on a torque control, is that potential fluctuations in torque do not cause changes in required angle allocations between the individual feed sites and thus the print quality is not adversely impacted. Due to the required angle allocation to the feed sites of the drives, any torque fluctuations within the sub-units of the printing machine will also cause angle errors, but in total they are much smaller than for a mechanical, longitudinal shaft, since each sub-unit regulates its own angle errors independently and/or individually.
Number | Date | Country | Kind |
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10 2007 049 455.8 | Oct 2007 | DE | national |
This patent application is the national phase of PCT/EP2008/008181, filed Sep. 26, 2008, which claims the benefit of German Patent Application No. 102007049455.8, filed Oct. 16, 2007.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2008/008181 | 9/26/2008 | WO | 00 | 5/11/2010 |