Sheet feeding or delivering – Feeding – With means to interrupt feeding
Reexamination Certificate
2001-07-11
2003-05-13
Mackey, Patrick H. (Department: 3651)
Sheet feeding or delivering
Feeding
With means to interrupt feeding
C271S262000, C271S258010, C271S258050, C271S265040
Reexamination Certificate
active
06561509
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a monitoring apparatus for the sheet feed to a sheet-processing machine (e.g., a sheet-fed printing machine), in particular overlapping sheet feed. The monitoring apparatus has at least one sensing element which is disposed above or beneath the sheet stream and, by means of an actuating device having an actuating drive, can be displaced in the direction of the sheet stream and in the opposite direction. The invention further relates to a method of monitoring the sheet stream structure or the sheet stream during its transport into a sheet-processing machine, wherein at least one sensing element can be displaced in the direction of a back-pressure element, over which the overlapping sheet stream or the sheet stream having individual sheets is guided.
U.S. Pat. No. 4,753,433 (European patent EP 0 242 622 B1) describes a monitoring apparatus of the type mentioned here which has a sensing roller which is arranged above a feeder table and can be displaced in the direction of the feeder table with the aid of an electric stepping motor. Coupled to the sensing roller is a sensor which always transmits a signal to a control device when at least two sheets overlap each other. It has been shown that the monitoring apparatus can be used only to a limited extent and, in the cases wherein dynamic and very precise displacement of the sensing roller is required, cannot be used, among other things because of the relatively sluggish stepping motor.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a monitoring apparatus which overcomes the above-noted deficiencies and disadvantages of the prior art devices and methods of this general kind, and to provide a method of monitoring the sheet stream wherein high functional reliability can be ensured.
With the above and other objects in view there is provided, in accordance with the invention, a monitoring apparatus for the sheet feed to a sheet-processing machine wherein a stream of sheets travel in a given sheet stream direction, comprising:
at least one sensing element disposed adjacent (i.e., above and/or underneath) the sheet stream;
an actuating device connected to the sensing element and configured to selectively displace the sensing element towards and away from the sheet stream, the actuating device having an actuating drive for displacing the sensing element, the actuating drive including at least one piezoelectric actuator (i.e., it is has or is formed by the piezoelectric actuator).
In other words, the apparatus has one or more sensing elements which is/are arranged above or beneath a sheet stream and can be moved in the direction of the sheet stream and away from the sheet stream by means of an actuating drive. The monitoring apparatus is distinguished by the fact that the actuating drive has at least one piezoelectric actuator or is formed by the latter. With the aid of the piezoelectric actuator, dynamic, that is to say very fast and precise, displacement of the sensing element is possible, which may be necessary in specific monitoring operations.
In a particularly advantageous exemplary embodiment of the monitoring apparatus, the piezoelectric actuator is constructed as described in German patent DE 196 46 511 C1 of the company marco Systemanalyse und Entwicklung GmbH. The disclosure content with regard to the construction and the function of the piezoelectric actuator of the German patent is herewith incorporated by reference. The piezoelectric actuator has a basic element which has a stack structure built up from ceramic lamellae layers.
By means of appropriate electrical driving of the piezoelectric actuator the latter can be pivoted or tilted about an axis lying at the area center of gravity of the basic element, so that the sensing element, directly or with the interposition of a transmission mechanism, can be displaced in the direction of the sheet stream or, respectively, of a support over which the sheet stream is transported, and in the opposite direction.
Further advantageous exemplary embodiments of the monitoring apparatus emerge from the dependent claims.
With the above and other objects in view there is also provided, in accordance with the invention, a method of monitoring a sheet stream structure or a sheet stream being transferred into a sheet-processing machine, which comprises:
transporting a stream of sheets across a back-pressure element and towards a sheet-processing machine;
displacing at least one sensing element in a direction towards the back-pressure element over which the stream of sheets is guided in the form of an overlapping sheet stream or a sheet stream having individual sheets;
detecting, with the sensing element set against the sheet stream, the sheet stream as it is transferred into the sheet-processing machine; and
thereby displacing the sensing element with respect to the sheet stream in dependence on an instantaneous sheet stream thickness such that a pressing force with which the sensing element is pressed against the sheet stream is maintained within a predefined range.
In other words, in order to monitor the sheet stream structure or the sheet stream during its transport into a sheet-processing machine, at least one sensing element can be displaced in the direction of a back-pressure element, over which the overlapping sheet stream or the sheet stream having individual sheets is guided, that is to say transported. The method is distinguished by the fact that the sensing element is set against the sheet stream, that is to say pressed on with a defined force, and detects the sheet as it is transferred into the machine, for example a sheet-fed printing machine. During the monitoring of the sheet stream, the sensing element is always displaced with respect to the sheet stream as a function of the respective instantaneous sheet stream thickness in such a way that the pressing force with which the sensing element is pressed against the sheet stream is kept at a predefinable value or within a predefinable value range. By means of a suitable sensor system, the travel is determined by which the sensing element is displaced with respect to the preferably stationary back-pressure element, for example formed by a feeder table. In this way, the thickness of the sheet stream can be determined or measured very exactly, so that double and missing sheets can readily be detected, which, for example, leads to the output of a fault signal. In addition, by means of the change in the distance of the sensing element with respect to the back-pressure element, including the respective instantaneous machine speed, premature, delayed and skewed sheets can also be detected. The method is distinguished by high accuracy and, in addition, exhibits high functional reliability. Moreover, it is particularly advantageous that, because of the pressing force of the sensing element on the back-pressure element being kept constant, the measuring conditions are constant, irrespective of the respective sheet stream thickness. Automation of the sheet thickness measurement or the sheet stream thickness measurement and/or the sheet stream monitoring is therefore readily possible.
In an advantageous exemplary embodiment of the method, provision is made for the pressing force of the sensing element against the sheet stream to be monitored and, in the event of the pressing force falling above or below a limiting value, for a fault signal to be triggered which, for example, leads to a visual display of a fault or directly to the machine being stopped.
According to another design variant, the distance between the sensing element and the back-pressure element is monitored by the relative movement of the sensing element with respect to the back-pressure element being measured/monitored in order to set a constant pressing force, it being possible here, too, for a fault signal to be output as soon as the distance between the sensing element and the back-pressure element falls above a specific upper limiting value or below a specific lower limiting
Butterfass Hans
Huschle Carsten
Kettenmann Peter
Müller Robert
Reuter Martin
Heidelberger Druckmaschinen AG
Mackey Patrick H.
Mayback Gregory L.
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