Printing – Rolling contact machines – Rotary
Reexamination Certificate
1998-10-05
2001-04-24
Eickholt, Eugene (Department: 2854)
Printing
Rolling contact machines
Rotary
C101S484000, C250S202000, C250S559290, C250S559380, C250S559440
Reexamination Certificate
active
06220158
ABSTRACT:
FIELD OF THE INVENTION
The present invention concerns rotation-angle measurement for printing presses with at least one marking arranged on a rotating element and at least one sensor which detects the marking.
RELATED TECHNOLOGY
In printing presses it is often necessary to determine a rotation angle unambiguously and precisely. This is particularly important for various automation functions; by way of example, the plate cylinder must be precisely positioned above the main drive for automatic change of printing plates. For this purpose, position feedback to the printing-press control system concerning the actual rotation angle of the machine is necessary. Up until the present, incremental sensors or similar sensor systems which were mounted on the shafts of certain cylinders were used for this purpose. These sensors have an internal scale which, as a rule, is an optical disk with grid lines. The instantaneous angular position can be determined using light barriers or the like. For reasons of space, it is possible to attach this sensor only where a free shaft end is present. Installation and adjustment are involved processes, and installation errors result in measurement errors. In incremental sensors of this kind, the rotation angle of the element the position of which is to be determined is not determined directly but rather the angular position of the measuring disk assigned to this element is determined. As a result, additional errors occur since the position of the measuring disk is not always in agreement with the position of the element the position of which is to be determined. Such errors are caused by alignment errors, bearing eccentricity, or shaft torsion. In addition, additional errors occur through play, bent gearwheels, etc., resulting in angular displacement between the individual cylinders so that several of these rotation sensors would have to be used for precise determination of position. However, this is not practicable due to the high cost and additional space requirement.
In order to provide simple determination of a rotation angle without a large space requirement, European Patent Application No. 0 562 608 A1 suggests rotation-angle measurement where a marking in the form of a reflecting plate is fixed to a gearwheel and the marking is detected by a sensor. While this type of rotation angle determination is of simple design, continuous measurement is not possible; thus interim values must be determined by a supplemental incremental sensor. This in turn requires precise adjustment of a measuring disk and results in the errors described above.
SUMMARY OF THE INVENTION
An objective of the present invention is to further develop the rotation-angle measurement so as to make a simple device available for continuous and precise rotation-angle measurement.
The present invention provides that at least one marking extends along an entire circumferential path and that such marking is arranged on the element, the position of which is to be determined.
The method according to the present invention has the advantage that the position of the element in question is determined directly. Thus an appropriate marking can be applied to the plate cylinder to determine its position in a direct manner without misalignment of a measuring disk, shaft torsion, or other influences resulting in a measuring disk of this type not indicating the exact angular position of the element which is to be determined. In the example of the plate cylinder, precise determination of the angular position is required, for example, to insert a printing plate which is to be changed automatically precisely into the clamping device.
A further advantage of the method according to the present invention is that the suggested device is constructed in a significantly more simple manner, can be manufactured more cost-effectively, and is very simple to install. Most importantly, it requires almost no additional space, and it is therefore possible to provide rotation-angle measurement of this kind at several points of the printing press. Thus, appropriate rotation-angle measurement can be assigned to each element the rotation angle of which must be precisely determined. It is even possible to install several rotation-angle measurement units to compensate mathematically in this manner for errors.
The marking can be configured in various ways; thus it is possible, for example, for it to be a depression machined into the element or a raised area or another marking which can be detected by a sensor. A marking of this type can in turn be detected by various types of sensors based on various principles of operation. The detection can be optical, or it is possible, for example, to detect depressions or elevations electromagnetically. Such a marking may be configured as a milled sine-wave line which is detected by at least one sensor.
A particularly advantageous further development is for the toothed rim of a gearwheel to serve as a marking. The drive gearwheels of a printing press in particular are parts of particularly high precision, and they must be precisely coordinated with the associated cylinders because they represent the link with the drive and thus to the control system of the printing press. The quality of printing depends on this precision, and it is among the highest levels of precision which is achieved in machine building. For this reason, it is possible to utilize this toothed rim directly for determination of rotation angle in printing presses. This not only makes arranging an additional marking unnecessary, but also reduces the required space since it is only one or several sensors which must be attached. It thus becomes unnecessary to align a marking since the gearwheels are the elements of the printing press that determine the rotation angle. In this way, the indirect approach using a measuring disk is avoided and the associated source of error is eliminated. In addition, by determining the rotation angle directly at the gearwheel, inaccuracies of the gearwheel can be detected at the same time and eliminated by the control system.
It is particularly useful for the at least one sensor to detect a marking on the basis of the change in a magnetic field. For example, the at least one sensor can be a Hall-effect device. In this way, rotation-angle measurement becomes particularly insensitive to contamination which is particularly prevalent in the gear train of a printing press. Special enclosures as needed in the case of disks which must be detected optically are no longer necessary. This simplifies the construction of the device and makes it particularly robust, reliable, and economical. The teeth of a tooth rim in particular are very easily detected in this manner.
In order to detect the direction of rotation in addition to the angular position, it can be provided that at least two sensors are arranged offset viewed in the angle of rotation.
In order to be able to determine the exact angle at every point in time, it is proposed that the circumferential path have at least one marking of a certain width and that the at least one sensor extend as a result of oblong configuration at least partially across this width, the sensor and the marking being configured so that the measured value changes continuously. This is the case, for example, in a milled line which changes in its dimensions or location along the circumferential path. If the toothed rim of a gearwheel serves as marking, it is possible for at least one sensor to extend transversally to the direction of rotation of a helically toothed gearwheel and to be matched to the width of a tooth. With a spur-toothed gearwheel, at least one sensor can extend obliquely to the tooth orientation of the spur-toothed gearwheel and can be matched to the width of a tooth. With embodiments of this type, measurement profiles are generated which can be attributed to the angular position at a given moment through an appropriate metrological evaluation. The measurement profiles can be of any shape, for example sawtooth profiles or sinusoidal profiles. With these kinds
Hartmann Klaus
Krueger Michael
Eickholt Eugene
Heidelberger Druckmaschinen AG
Kenyon & Kenyon
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