Printing – Processes – Position or alignment
Reexamination Certificate
2000-05-12
2004-12-07
Eickholt, Eugene H. (Department: 2854)
Printing
Processes
Position or alignment
C101S486000, C101S248000, C101S137000, C101S177000, C101S183000
Reexamination Certificate
active
06827018
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a device and a method for driving printing machines using multiple motors.
RELATED TECHNOLOGY
German Patent Application No. 15 63 591 discloses a device in which multiple motors induce a predetermined torque into a gear train or a drive shaft connecting the various printing units. The gear train enables the synchronization of the various printing units. Due to a surplus of torque, the flanks of the gear teeth are in continuous engagement with one another in one direction so as to ensure good print quality. However, it is disadvantageous in this device that an elastic deformation of the gear wheels causes a noticeable impairment of the print quality, as application of the exact required torques cannot be ensured due to the continuously varying load torque.
It is generally known to divide the printing units into separate sections which, by means of single drives, can be driven in such a manner that only slight elastic deformation of the gear wheels takes place within the printing unit sections. The individual printing unit sections are synchronized to one another in a manner that the exact transfer of a paper sheet is ensured. This device has the disadvantage that the individual printing unit sections have very large masses which receive different additional load torque during one rotation. Consequently, a very complicated regulation is required in order to achieve the print quality known from machines with separate drives. An alternative design is disclosed in the German Patent Application No. 41 37 979 A1, wherein the actual control is limited to an angularly synchronous transfer of the printed sheet. This is to say, that regulation takes place only within a certain angular range about the point of transfer, and that outside of this angular range only the rotational speed is kept constant. This makes the timing conditions for the regulation easier, but the masses remain at an unchanged high level.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a device and a method, whereby the disadvantages of the prior art are minimized.
The present invention provides a device for the synchronization of at least two printing-unit groups (
2
,
3
) forming a sheet-fed printing machine (
1
), each of the printing-unit groups (
2
,
3
) being driven by at least one separate drive motor (
7
,
9
) and gear train, characterized in that between the printing-unit groups (
2
,
3
) there is provided at least one transfer unit (
10
) with a separate variable-speed drive motor (
12
).
The present invention also provides a method for the synchronous transfer of printed sheets through a transfer unit (
10
) arranged between two printing-unit groups (
2
,
3
) driven using a respective separate drive, characterized in that through the if transfer unit (
10
) arranged between two printing-unit groups phase synchronism is first established with respect to the printing-unit group (
2
) arranged in front of said transfer unit and then with respect to the printing-unit group (
3
) arranged behind it.
The present invention has the advantage that owing to a separately driven transfer unit the printing machine is uncoupled and at the same time remains easy to be regulated.
The printing-unit groups in front of and behind the separation are respectively connected with one another using a conventional gear-wheel train and are each provided with one drive. Through this separation the interconnected printing units show a favorably low vibration tendency, i.e. the natural frequency of the printing-unit groups still is high enough so that there is no inducement of significant vibration, even at maximal production speed. The regulation of these drives does not need to be synchronized with high precision in order to achieve an in-phase paper transfer, as a phase displacement can be compensated through the transfer unit. Thus, no quick regulation of the drive of the printing units in front of and behind the transfer unit is necessary, so that vibrations caused by regulation are avoided and the printing machine produces good printing results. The phase displacement occurring in the divided printing units is compensated by regulating the transfer unit. This means that the paper sheet is received in phase at the transfer unit from the preceding printing-unit group, the phase position is then corrected during the rotary movement for the transfer to the succeeding printing-unit group, where the paper sheet is received in phase again. The quick regulation in the transfer unit is made possible because the transfer unit has little mass and no mechanical load is exerted on the printing-unit a groups in front of and behind the transfer unit. Moreover, motors possessing favorable regulating characteristics due to a low load torque can be used for this purpose. Drives which can be arranged directly on the shaft of the transfer unit are especially suitable therefor.
The transfer unit is realized, for example, in that a transfer cylinder serves as a transfer unit. From the state of the art it is known to design the transfer unit as a single-revolution cylinder, i.e. the rolling off motion (sheet plus gap) of the impression cylinder and of the transfer cylinder is identical. Furthermore is it known to design the transfer cylinder as a so called storage drum which operates at one half or one third of a revolution, thus, having a circumference which is double and three times the circumference of the impression cylinder. At any rate, the circumference of the transfer cylinder and the circumference of the impression cylinder are in an integral relationship.
However, such integral relationship is not absolutely necessary as mechanical coupling can be eliminated. For example, a transfer cylinder with a circumference of two-and-one-half times the circumference of the impression cylinder has the advantage that the range of the angle of rotation in which a phase correction can be performed is a larger one. It also is contemplated to use the gap between two sheets caused by the cylinder channel for phase correction.
For example, the transfer cylinder, after receiving a sheet, rotates with the same circumferential speed as all cylinders arranged in front thereof. Thereby it is ensured that the sheet does not experience any relative movement with respect to its transport medium, so that there is no danger of smudging. If the sheet is located outside of the printing nip, that is, outside of the feed surface of the transferring printing unit, the sheet can be accelerated or slowed down, until an exact alignment of the phase of the transfer unit with the phase of the succeeding printing-unit groups has taken place. The rotary movement of the transfer unit is therefore not continuous but depends on diameter and modulated phase correction.
It is advantageous that the moment of take-over and the moment of transfer are not identical, but are such that in the interim a respective phase correction is possible, having effect first on the printing-unit group located behind the transfer unit and then on the printing-unit group located in front of said transfer unit.
The present invention has the additional advantage that register corrections can be carried out by setting the phase relationship. A controlled phase displacement at the take-over and/or transfer of the sheet can be used so that the paper-sheet rim gripped by the grippers becomes wider or narrower, thereby enabling the setting of the register. The same is true when the device according to the present invention is used for sheet-tuning. This means that the transfer unit takes the place of the present perfecting drum. It is known that in the sheet-turning process the trailing edge of the sheet is grasped and that for switching from front-side printing to perfecting and for different formats various settings or adjustments have to be carried out; these can take place through a simple program conversion per push-button. Thereby, the stand-still times for preparing the machine for a change in orders are considerably r
Hartmann Klaus
Krueger Michael
Wagensommer Bernhard
Eickholt Eugene H.
Heidelberger Druckmaschinen AG
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