Sheet feeding or delivering – Feeding – Separators
Reexamination Certificate
2000-03-20
2002-02-26
Bollinger, David H. (Department: 3651)
Sheet feeding or delivering
Feeding
Separators
C271S106000, C271S107000, C271S108000
Reexamination Certificate
active
06349930
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a lifting sucker and a method of operating a lifting sucker which takes sheets off a pile, the sheets being gripped by suction and lifted, and the lifting sucker having a suction air source, a device for executing the lifting movement and a control device.
Lifting suckers of this general type are used in paper-processing machines, in particular in printing machines, for lifting sheets off piles, in order to feed the sheets to the machine. The published German Patent Document DE 40 12 778 C
1
discloses a lifting sucker of the type described at the introduction hereto. With regard to this sucker, the holding force and the lifting movement are produced together by suction air. The sheet is lifted when the suction surface is covered by the sheet. In the case of such lifting suckers, adjustment to the respective paper grades which are used is necessary, the adjustment making a great deal of fingertip feel and test runs necessary. If the adjustment is not correct, the sheet may not be picked up, or double or multiple sheets may also be gripped by the lifting sucker. It is also possible for such malfunctions to occur following an adjustment carried out once, in particular when specific influencing variables change. Such influencing variables are a waviness of the paper, temperature, humidity, electrostatics or air pressure. To some extent, sheets also stick to one another, in particular at the edges.
As a countermeasure, it has previously been known to use double-sheet controls which, in the event of a fault, stop the paper run and thus bring the machine to a standstill. However, detecting a double sheet within an imbricated sheet stream presents difficulties. The previously known double-sheet controls were disposed immediately before or upline of the inlet into the machine, the result of which is that the security elements switching-on in the event of a fault have very little reaction time available to stop the process. Furthermore, in some cases, for example in the case of specific paper grades, correct operation of the double-sheet controls is not ensured. In this case, it is possible for so-called packets to be formed, i.e., for two or more sheets to stick to one another, which can ruin the machine. Even if double-sheet controls of this type are able to prevent damage to the machine, the production process is nonetheless interrupted. A further disadvantage of the heretofore known lifting suckers and the mode of operation thereof is that the functional sequence thereof is permanently predefined, and flexible adjustments and adaptation to the production sequence are not possible.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method and a device of the type mentioned at the introduction hereto so that a sheet run is automatically stabilized for different materials, in particular for different paper grades, and during other changes to the boundary conditions, and is adjusted optimally, and double sheets are prevented.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a method of operating a lifting sucker which takes sheets off a pile, the sheets being picked up and lifted by suction, which comprises determining at least one of the physical variables characterizing the method and comparing it with an associated desired value, and initiating countermeasures if there are any deviations from the desired value.
In accordance with another mode, the method of the invention includes determining a physical variable characterizing the lifting operation.
In accordance with a further mode, the method of the invention includes determining the vacuum.
In accordance with an added mode, the method of the invention includes determining the lifting force.
In accordance with an additional mode, the method of the invention includes determining the lifting time.
In accordance with yet another mode, the method of the invention includes determining the lifting acceleration.
In accordance with yet a further mode, the method of the invention includes determining the travel as a function of time.
In accordance with yet an added mode, the method of the invention includes determining the retardation energy at the upper stop of the lifting sucker.
In accordance with yet an additional mode, the method of the invention includes comparing the physical variable with an entered desired value.
In accordance with still another mode, the method of the invention includes comparing the physical variable with physical variables from preceding operations.
In accordance with still a further mode, the method of the invention includes performing a readjustment if there are deviations.
In accordance with still an added mode, the method of the invention includes breaking off and repeating the operation.
In accordance with still an additional mode, the method of the invention includes correcting the suction force.
In accordance with yet another mode, the method of the invention includes removing multiple sheets.
In accordance with yet a further mode, the method of the invention includes subjecting multiple sheets to a transverse movement.
In accordance with yet an added mode, the method of the invention includes, after a correction, controlling the sheet run so that any possible time delay is recovered.
In accordance with another aspect of the invention, there is provided a lifting sucker having a suction air source, a device for performing a lifting movement, and a control device, comprising at least one device for measuring a physical variable, the control device being constructed so as to perform a desired value comparison, and to initiate countermeasures if there are deviations.
In accordance with a further feature of the invention, the lifting sucker comprises separate devices for picking up a sheet by suction and lifting it.
In accordance with an added feature of the invention, each of the separate devices has at least one measuring device.
In accordance with an additional feature of the invention, the lifting sucker includes an electromagnetic linear drive for lifting action.
In accordance with an alternative feature of the invention, the lifting sucker includes a piezoelectric drive for lifting action.
In accordance with yet another feature of the invention, the sheet is liftable obliquely, with a forward drive component.
In accordance with yet a further feature of the invention, the lifting sucker includes a measuring system integrated into the drive.
In accordance with yet an added feature of the invention, the lifting force is determined.
In accordance with yet an additional feature of the invention, the lifting force is determinable by measuring the current.
In accordance with still another feature of the invention, the travel is determinable as a function of time.
In accordance with still a further feature of the invention, for this measurement, the drive current has a signal superimposed thereon, and the lifting sucker includes a device for separating and separately evaluating the travel-dependent changes in this signal.
In accordance with still an added feature of the invention, the lifting sucker includes devices for determining and regulating the suction force.
In accordance with still an additional feature of the invention, the lifting movement is controllable.
In accordance with another feature of the invention, the lifting sucker includes a device for removing multiple sheets.
In accordance with a concomitant feature of the invention, the sheet run is acceleratable by the control device so that a time delay is recoverable within given limits.
With regard to the method of the invention, the object thereof is achieved in that at least one of the physical variables which characterize the method is determined or registered and compared with an associated desired value and, if there are deviations from the desired value, countermeasures are initiated.
With regard to the lifting sucker of the invention, the object thereof is achieved in tha
Krüger Michael
Wagensommer Bernhard
Bollinger David H.
Heidelberger Druckmaschinen AG
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