DE102006037248B4 - False sheet sensor of a printing sheet processing machine - Google Patents

Abstract

False sheet sensor of a printing sheet processing machine, in particular a sheet-fed printing machine, with a measuring capacitor defining a capacitor chamber, the measuring capacitor having at least two opposing measuring electrodes defining the capacitor chamber, through which printed sheets can be moved for false sheet detection, characterized by at least one device (13; 20), which influences a field line course in the capacitor space defined by the measuring electrodes (11, 12; 18, 19) in such a way that the capacitor space comprises a measurement space (14; 21) with a homogeneous field line distribution and by at least one dielectric lens (13) located in the between measuring electrodes (11, 12) extending capacitor chamber, with a measuring electrode (11) with a point geometry opposite a first side of the dielectric lens (13) and a measuring electrode opposite a second side of the dielectric lens (13) ode (12) is arranged with a plate-shaped geometry, and wherein the area of the capacitor chamber extending between the dielectric lens (13) and the measuring electrode (12) with the plate-shaped geometry forms the measuring chamber (14) with the homogeneous field line distribution.

Description

The invention relates to a false sheet sensor of a printing sheet processing machine according to the preamble of claim 1.

In machines that process printed sheets, in particular in sheet-fed printing machines, printed sheets are kept ready as an attachment stack, with printed sheets being lifted individually from the attachment stack with the aid of suction devices and deposited on an attachment device designed as a feed table. Via the feed table, the printed sheets are fed to a sheet feeding device of the printing sheet processing machine. The printed sheets lifted from the system stack are usually fed in an imbricated sheet position as an imbricated stream to the sheet feeder via the feed table. In order to ensure the correct operation of a printing sheet processing machine, it is important that no so-called false sheets occur. A false sheet can, for example, be a double sheet made up of two printed sheets positioned one above the other. If such a double sheet is fed to the printing sheet processing machine, this can lead to damage of the same. The detection of false sheets is therefore important.

The term false sheet is to be understood as meaning all printed sheets which differ from a proper printed sheet with regard to at least one property. In addition to double sheets, these can also be missing sheets, multiple sheets, oblique sheets, early sheets, late sheets, thick sheets or thin sheets. Missing sheets and multiple sheets, like double sheets, differ in terms of the number of sheets from a correct printing sheet. With early and late sheets, as with diagonal sheets, the position of the printed sheet deviates from a proper printed sheet. Thick sheets and thin sheets differ from a proper print sheet in terms of the substrate thickness.

In practice, mechanical devices are generally used to identify double sheets, which mechanically scan the imbricated flow of printed sheets to be checked. The mechanical double-sheet control device rolls onto the printed sheet, which can cause running marks on the printed sheet. Running marks on the printed sheet impair the quality of the same and are therefore a disadvantage.

Furthermore, double-sheet control devices are used in practice, which are based either on the principle of optical transmission or the absorption or reflection of ultrasonic waves. Optical double sheet control devices or ultrasonic double sheet control devices, however, require the presence of a single sheet for double sheet control. In a sheet-fed printing machine, this condition is only met for a short time and only immediately before the sheet is mechanically accessed by the sheet feed device of the sheet-fed printing machine. It follows directly from this that if a double sheet is identified with the aid of an optical double sheet control device or an ultrasonic double sheet control device, only a short time is available for measurement.

wobei C die Kapazität, ε₀ die Dielektrizitätskonstante, ε_r die relative Dielektrizität des Bedruckstoffs, A die Fläche der den Kondensatorraum des Messkondensators definierenden Messelektroden und d der Abstand zwischen den Messelektroden ist.In order to avoid the above disadvantages of the double sheet control devices used so far in practice, according to the prior art according to FIG DE 40 03 532 C2 as well as the EP 1 403 202 A1 capacitive double sheet controllers proposed. With these capacitive double-sheet control devices, the imbricated flow to be checked is moved through a capacitor space formed by a measuring capacitor. The capacitive measurement is based on the following relationship: $$\mathrm{C.}={\epsilon }_0\ast {\epsilon }_r\ast \frac{\mathrm{A.}}{d}$$

where C is the capacitance, ε _{0 is} the dielectric constant, ε _{r is} the relative dielectricity of the printing material, A is the area of the measuring electrodes defining the capacitor space of the measuring capacitor and d is the distance between the measuring electrodes.

Since all printing materials have a dielectricity that differs from that of air, the capacitance of the same changes when the imbricated flow moves through the capacitor chamber of the measuring capacitor, whereby false sheets can in principle be identified from the change in capacitance.

In the case of capacitive false arc sensors known from practice, there is the problem that they have an inhomogeneous field line distribution in the capacitor space formed by the measuring electrodes. Due to this inhomogeneous field line distribution in the capacitor chamber, the change in capacitance of the measuring capacitor, which is caused by the penetration of a printed sheet into the capacitor chamber of the false sheet sensor, depends on the position or location of the printed sheet in the capacitor chamber of the measuring capacitor of the false sheet sensor. However, since the position or the place of entry of a printed sheet into the condenser space of the false sheet sensor cannot be precisely maintained during operation of a printed sheet processing machine, this is the case with the false sheet sensor The measurement signal provided is subject to fluctuations, which have hitherto opposed the use of capacitive false sheet sensors on machines that process printed sheets. There is therefore a need for a false arc sensor which, at least in sections, has a homogeneous field line distribution in the capacitor space.

Out DE 197 34 102 A1 a method and a device for machine protection when using printed materials in printing machines is known. When processing materials that have already been printed, a machine protection mode can be activated on the printing machine. A sheet control is carried out in the machine protection mode with a capacitive double sheet control device. In this way, an interruption of the sheet travel which is only effective when the multiple sheets are above the threshold of the same, is activated after the processing of already printed materials.

Out JP H08-29111 A a measuring device and a measuring method using a capacitive measuring system are known. To measure the thickness and displacement of an insulating sheet with one operation, an electrostatic capacitance meter is used simply by adding a simple device. The thickness or displacement measuring device consists of a flat main electrode that is insulated and accommodated in a first flat, plate-shaped protective electrode. A second flat tabular guard electrode receives the first flat guard electrode. The guard electrode is insulated and a tabular ground electrode is placed on top of the guard electrode. The second protective electrode is shielded by an insulating element. The measurement of a thickness by means of the second flat tabular guard electrode and the ground electrode are measured under the condition of electrical insulation. To measure displacement, the second guard electrode and the ground electrode are measured under the condition of a short circuit.

From the DE 195 37 954 C1 a device for checking sheets is known, the sheets being drawn into a sheet processing machine singly from a stack. At least one optical transducer directed at the sheets is arranged on the sheet processing machine, the output signal of which is evaluated in an evaluation unit with regard to its amplitude for the presence of a single or multiple sheet. In addition, at least one capacitive measuring transducer is provided, the output signal of which is also evaluated in the evaluation unit with regard to the amplitude for the presence of a single or multiple sheet. In the evaluation unit, depending on the amplitude of the output signal of the optical and / or capacitive transducer, only one output signal is used to decide whether a simple. or multiple sheets are used.

Out DE 100 03 352 A1 a transport system for a printing machine is known which contains at least one printing substrate guide surface, means for generating an air cushion between the guide surface and the printing substrate and at least one sensor arrangement for detecting the distance between printing substrate and guide surface. Furthermore, control means are provided which are able to control the strength of the air cushion on the basis of the detected distance in such a way that the distance detected by the sensor arrangement comes to lie in a desired range.

Proceeding from this, the present invention is based on the problem of creating a new type of capacitive false sheet sensor of a printing sheet processing machine. This problem is solved by a false sheet sensor according to claim 1.

According to the invention, the false arc sensor comprises at least one device which influences a field line course in the capacitor space defined by the measuring electrodes in such a way that the capacitor space comprises a measurement space with a homogeneous field line distribution.

The false arc sensor according to the invention has, in addition to the measuring electrodes, which define a capacitor compartment of the measuring capacitor, devices which influence the course of the field lines in the capacitor compartment in such a way that the same has a homogeneous field line distribution in a measuring compartment, which in particular corresponds to a partial area of the capacitor compartment. As a result, the measurement quality that can be achieved with capacitive false-arc sensors can be improved.

According to a first preferred development of the invention, the false arc sensor comprises at least one dielectric lens which is arranged in the capacitor space extending between measuring electrodes, with a measuring electrode with a point geometry opposite a first side of the dielectric lens and opposite a second side of the dielectric lens a measuring electrode is arranged with a plate-shaped geometry, and wherein the region of the capacitor chamber extending between the dielectric lens and the measuring electrode with the plate-shaped geometry forms the measuring chamber with the homogeneous field line distribution.

According to a second preferred development of the invention, which can be used either alone or in combination with the first preferred development of the invention, at least one shaped electrode is assigned to at least one plate-shaped measuring electrode, the or each shaped electrode deflecting the course of the field lines in the area of the plate-shaped measuring electrode to which the or each shaped electrode is assigned in such a way that, adjacent to the plate-shaped measuring electrode, a measuring chamber of the capacitor chamber has a homogeneous field line distribution.

• 1: eine schematisierte Darstellung eines erfindungsgemäßen Falschbogensensors einer Druckbogen verarbeitenden Maschine nach einem ersten Ausführungsbeispiel der Erfindung; und
• 2: eine schematisierte Darstellung eines erfindungsgemäßen Falschbogensensors einer Druckbogen verarbeitenden Maschine nach einem zweiten Ausführungsbeispiel der Erfindung.

Preferred developments of the invention emerge from the subclaims and the following description. Embodiments of the invention are explained in more detail with reference to the drawing, without being restricted thereto. It shows:

• 1 : a schematic representation of a false sheet sensor according to the invention of a printing sheet processing machine according to a first embodiment of the invention; and
• 2 : a schematic representation of a false sheet sensor according to the invention of a printing sheet processing machine according to a second embodiment of the invention.

1 shows a schematic representation of a false sheet sensor according to the invention 10 according to a first embodiment of the invention, wherein the false sheet sensor 10 one of two measuring electrodes 11 and 12 Has formed measuring capacitor. The measuring electrodes 11 , 12 delimit a capacitor space between the two measuring electrodes 11 , 12 extends.

In the embodiment of 1 points the measuring electrode 11 a punctiform geometry and the measuring electrode 12 a plate-shaped geometry. An electrode with a point-like geometry is to be understood as an electrode whose geometry leads to field lines on this electrode running approximately through a common point.

According to 1 is in that of the two measuring electrodes 11 and 12 limited capacitor space a dielectric lens 13 arranged, which is shown by a dashed box.

At the dielectric lens 13 it is a device that creates a field line course in that of the measuring electrodes 11 , 12 The defined capacitor space is influenced in such a way that the capacitor space is a measuring space 14th includes with a homogeneous field line distribution. Opposite a first side of the dielectric lens 13 is the measuring electrode 11 with the point-like geometry and opposite to a second side of the dielectric lens 13 the measuring electrode 12 arranged with the plate-shaped geometry.

The measuring room 14th with the homogeneous field line distribution extends between the dielectric lens 13 and the measuring electrode 12 with the plate-shaped geometry. In this measuring room 14th there is a homogeneous field line distribution so that a reliable, capacitive measurement signal can be provided for the detection of false sheets.

The one from the measuring electrodes 11 , 12 The capacitor space defined is accordingly of the dielectric lens arranged in the capacitor space 13 divided into two areas, namely an area between the dielectric lens 13 and the measuring electrode 11 with the point-like geometry and in an area between the dielectric lens 13 and the measuring electrode 12 with the plate-shaped geometry, the area between the dielectric lens 13 and the measuring electrode 12 the measuring room with the plate-shaped geometry 14th of the condenser space forms or provides.

The dielectric lens 13 is concave on at least one side. Then when the dielectric lens 13 is concave on one side only, the concave curvature is the side of the dielectric lens 13 assigned to the measuring electrode 11 with the point-like geometry opposite. However, it is also possible that the dielectric lens 13 is concave on both sides.

The dielectric lens 13 is formed from a material that preferably has a greater relative dielectricity than the printing material of the printed sheet that passes through the measuring space 14th of the false sheet sensor 10 should be moved. However, it is also possible that the dielectric lens 13 consists of a material that has a smaller relative dielectricity than the printing material of the printed sheet, but a larger relative dielectricity than air.

As already stated, the measuring electrode has 11 via a point-like geometry. The measuring electrode can 11 be designed as a tip electrode or a spherical electrode.

According to 1 is the dielectric lens 13 in a receiving facility 15th stored, the receiving device 15th takes on a shielding function and provides a shield for scattering field lines. This allows the measuring room 14th be shielded against scattering field lines, so that the homogeneous field line distribution in the measuring room 14th is not adversely affected by scattering field lines.

Another exemplary embodiment of a false sheet sensor according to the invention 17th shows 2 highly schematic. So also includes the false sheet sensor 17th of the embodiment of 2 two measuring electrodes 18th and 19th that define a capacitor space, wherein in the embodiment of 2 both measuring electrodes 18th and 19th have a plate-shaped geometry.

In the embodiment of 2 is one of the two measuring electrodes 19th a shaped electrode with plate-shaped geometry 20th assigned, the formula electrode 20th the course of the field lines in the area of the measuring electrode 19th holding the formula electrode 20th is assigned, deflects such that adjacent to the plate-shaped measuring electrode 19th the condenser room a measuring room 21st includes with a homogeneous field line distribution.

With the formula electrode 20th it is accordingly in turn a device which influences the course of the field lines in the capacitor space defined by the measuring electrodes in such a way that the capacitor space comprises a measurement space with a homogeneous field line distribution.

In the exemplary embodiment shown, there is only one plate-shaped measuring electrode 19th a formula electrode 20th assigned. However, it is also possible that both measuring electrodes 18th , 19th of the false sheet sensor 17th the 2 at least one form electrode is assigned to each.

The formula electrode 20th of the false sheet sensor 17th the 2 has a different electrical potential than the plate-shaped measuring electrode 19th holding the formula electrode 20th assigned.

The electrical potential of the shaped electrode is preferably different 20th both from the electrical potential of the measuring electrode 19th as well as the electrical potential of the measuring electrode 20th , i.e. from the electrical potential of all measuring electrodes that define the capacitor space. However, a field line-shaping function of the or each form electrode is also conceivable if it has the same electrical potential as the measuring electrode.

The plate-shaped measuring electrode 12 of the embodiment of 1 or one of the plate-shaped measuring electrodes 18th or. 19th of the embodiment of 2 is preferably formed by a feed table of a sheet-fed printing machine. The point-shaped measuring electrode 11 of the embodiment of 1 or one of the plate-shaped measuring electrodes 19th or. 18th of the embodiment of 2 is preferably formed by a functional element of the sheet-fed printing machine, for example by a transport element of the same.

For the purposes of the present invention, it is possible to use the principles of the two false sheet sensors in accordance with 1 and 2 to combine with each other. So z. B. the plate-shaped measuring capacitor 12 of the false sheet sensor 10 the 1 be assigned a formula electrode, as in the embodiment of 2 for the measuring electrode 19th is shown.

List of reference symbols

10

False sheet sensor

11

Measuring electrode

12

Measuring electrode.

13

dielectric lens

14th

Measuring room

15th

Receiving facility

17th

False sheet sensor

18th

Measuring electrode

19th

Measuring electrode

20th

Formula electrode

21st

Measuring room

Claims (11)

False sheet sensor of a printing sheet processing machine, in particular a sheet-fed printing machine, with a measuring capacitor defining a capacitor chamber, the measuring capacitor having at least two opposing measuring electrodes defining the capacitor chamber, through which printed sheets can be moved for false sheet detection, characterized by at least one device (13; 20) which influences a field line profile in the capacitor space defined by the measuring electrodes (11, 12; 18, 19) in such a way that the capacitor space comprises a measurement space (14; 21) with a homogeneous field line distribution and is provided with at least one dielectric lens (13), which is in the capacitor space extending between measuring electrodes (11, 12) is arranged, with a measuring electrode (11) with a point geometry opposite a first side of the dielectric lens (13) and a measuring electrode opposite a second side of the dielectric lens (13) Trode (12) is arranged with a plate-shaped geometry, and wherein the area of the capacitor chamber extending between the dielectric lens (13) and the measuring electrode (12) with the plate-shaped geometry forms the measuring chamber (14) with the homogeneous field line distribution. False sheet sensor after Claim 1 , characterized in that the dielectric lens (13) on at least one side, in particular at least on the first side, which is the measuring electrode (11) with the point-like geometry and opposite, is concave. False sheet sensor after Claim 1 or 2 , characterized in that the dielectric lens (13) consists of a material which has a greater relative dielectricity than the printing material of the printed sheet. False sheet sensor after Claim 1 or 2 , characterized in that the dielectric lens (13) consists of a material which has a greater relative dielectricity than air and a smaller relative dielectricity than the printing material of the printed sheet. False sheet sensor according to one or more of the Claims 1 to 4th , characterized in that the measuring electrode (11) with the point-like geometry is designed as a tip electrode or as a spherical electrode. False sheet sensor according to one or more of the Claims 1 to 5 , characterized in that the or each dielectric lens (13) is mounted in a receiving device (15), the receiving device (15) forming a screen for scattering field lines. False sheet sensor according to one or more of the Claims 1 to 6th , characterized in that at least one shaped electrode (20) is assigned to at least one plate-shaped measuring electrode (19), the or each shaped electrode (20) having the field line course in the area of the plate-shaped measuring electrode (19) to which the or each shaped electrode (20) is assigned , deflects such that adjacent to the plate-shaped measuring electrode (19) a measuring space (21) of the capacitor space has a homogeneous field line distribution. False sheet sensor after Claim 7 , characterized in that the or each formula electrode (20) has at least one different electrical potential than the plate-shaped measuring electrode (19) to which the or each formula electrode (20) is assigned. False sheet sensor after Claim 8 , characterized in that the or each shaped electrode (20) has a different electrical potential than all measuring electrodes (18, 19). False sheet sensor according to one or more of the Claims 1 to 9 , characterized in that the plate-shaped measuring electrode (12) or one of the plate-shaped measuring electrodes (18, 19) of the measuring capacitor is formed by a feed table of a sheet-fed printing machine. False sheet sensor after Claim 10 , characterized in that the point-shaped measuring electrode (11) or one of the plate-shaped measuring electrodes (18, 19) of the measuring capacitor is formed by a functional element of the sheet-fed printing machine.

Images