Printing – Processes – Condition responsive
Reexamination Certificate
1999-08-18
2001-04-24
Colilla, Daniel J. (Department: 2854)
Printing
Processes
Condition responsive
C101S483000, C101S485000, C101S351100, C101S352010
Reexamination Certificate
active
06220162
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method and an apparatus for detecting collisions in printing machines.
Printing machines typically have a number of rotationally driveable rotary bodies, each of which can be adjusted in a direction normal to the axis of rotation by means of an associated actuator. For example, in a typical flexographic printing machine, a plurality of inking units are arranged at a common reaction cylinder, and each inking unit has two such rotary bodies, i.e. a printing cylinder and an inking roller. During the printing operation the inking roller is in rolling engagement with the printing cylinder, and the printing cylinder itself is in rolling engagement with the printing medium which is guided around the reaction cylinder, so that the ink is transferred from the inking roller to the printing parts of the printing blocks of the printing cylinder and, then, a corresponding printed image is formed. In case of maintenance and retooling, for example, when the cylinders are exchanged, the inking roller is separated from the printing cylinder, and the printing cylinder is separated from the reaction cylinder. To this end, the inking roller and the printing cylinder are moved (adjusted) in a substantially radial direction relative to the reaction cylinder by means of their respective actuators. In this case there is a risk that the inking roller and the printing cylinder collide with one another or with other machine components, so that damages are caused.
It is therefore common practice to provide a monitoring system for detecting such collisions and for stopping the corresponding actuators immediately, in order to avoid damages or injuries of the operating personnel.
In conventional printing machines the detection of collisions is achieved by monitoring the driving torques of the actuator motors. When the rotary body hits an obstacle during the adjustment process, the driving torque transmitted from the actuator motor is increased, and when this driving torque exceeds a certain threshold value, this indicates that a collision has occurred, and the actuator motor is stopped.
The actuator, e.g. a spindle drive, generally has a large transmission ratio, so that even a comparatively small torque of the drive motor generates a high actuating force. Conversely, this means that the increase of the resistance opposing the adjusting movement in case of a collision leads to only a comparatively small increase in the transmitted torque. The collision detection system is therefore relatively slow and inaccurate. Although, in principle, the sensitivity can be increased by lowering the threshold value at which the actuator motor is stopped, this threshold value must always be selected so high that the sometimes considerably high frictional forces which occur during the adjusting movement can be overcome.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to increase the sensitivity in the detection of collisions.
In a method according to the present invention, this object is achieved by the feature that the rotary body is caused to rotate during the adjusting movement, and the rotary speed and/or the driving torque for the rotary movement is monitored.
When the rotary body collides with an obstacle during an adjustment operation, this blocks not only the further adjusting movement, but it also brakes the rotary movement. By monitoring the rotary speed and/or the torque of the rotary drive for the rotary body, this braking of the rotation can be detected with high sensitivity, so that, in case of a collision, a quicker and more sensitive response of the collision detection system is achieved. Another advantage of this solution is that the response sensitivity does not depend on the location at the circumference of the roller where the collision with the obstacle takes place. When, for example, the rotating body hits the obstacle in a glancing manner during the displacement, the displacement itself is scarcely blocked, but nevertheless the rotation is braked significantly, so that, even in this case, a more sensitive response of the collision detection system is assured. In particular, it is possible in this way to detect situations in which the rotary body is directly touched by an operator. Thus, injuries can be avoided reliably by immediately stopping the actuator and possibly also the rotary drive.
The solution according to the invention is particularly advantageous in printing machines of the single-drive type in which a separate drive motor is provided for the rotary drive of each rotary body. In this case, each rotary drive is provided with an angle increment sensor or torque sensor, anyway, for synchronising the rotary bodies, and this sensor and then be utilised as well for the collision detection, so that the construction of the collision detection system can be simplified.
REFERENCES:
patent: 5125339 (1992-06-01), Rogge
patent: 5142981 (1992-09-01), Dettinger et al.
patent: 5181468 (1993-01-01), Borel
patent: 5588362 (1996-12-01), Sugiyama et al.
patent: 5953991 (1999-09-01), Geissenberger et al.
patent: 0226554 (1987-06-01), None
Kolbe Wilfried
Schirrich Klaus
Steinmeier Bodo
Terstegen Manfred
Colilla Daniel J.
Fischer & Krecke GmbH & Co.
Goldberg Richard M.
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