FR2746705A1 - Contactless measurement device for shifts of continuous sheet - Google Patents

Abstract

The device directs crossed beams (13,14) from two lasers or infrared or other light sources (11,12) towards the moving sheet (5). The light scattered from the points of impact (A,B or A',B') is detected by a charge-coupled device (CCD) camera (10). The camera pixels receiving the scatter produce electrical signals from which the deviation (D1) from the reference distance (D0), due to the sheet being shifted (16) from its reference position (15), can be calculated. The signal-processing circuit may generate a control pulse to restore the sheet to the reference position.

Description

 The invention relates to a device for non-contact measurement and control of the position of a continuous traveling web in a machine for processing such a web, such as a rotary printing machine.

 Various devices of this type are already known.

 Thus, for example, document EP 0 184 907 describes a system for locating a strip of material to be treated which includes markers. Individual locations on the strip are illuminated using light sources, the reflected light is measured and an output signal is generated based on the intensity of the reflected light. A calculator searches the output signals for the minima of the reflected light fractions and determines the time intervals between them. It is possible to deduce from these time intervals the tracking differences in the longitudinal and transverse directions.

 The document FR 2 565 216 describes an opto-electronic device for signaling the lateral movement of an edge of a sheet of paper. A row of optical means, for example transversely oriented fibers, are mounted in a housing and arranged at the edge of a surface of a strip of material from a roll. The surface of the strip is subdivided into three strips by longitudinal cutting blades. A light source is arranged opposite the transversely oriented row of fibers, the strip of material being interposed between the source and the aforementioned row, so that it is possible to control the process of unwinding of the strip surface by the through the luminosities of the individual fibers. The luminosities are converted into electrical signals transmitted to analyzer means making it possible to intervene in the unfolding process.

 Document US 4,966,074 describes a display system for a "web reel" of a rotary offset printing machine. An optical detector arranged on one side of the blanket cylinder of a printing machine explores the reflection of the surface of this cylinder. If there is a sudden increase in the reflection of the surface of this cylinder, it is interpreted as a signal indicating that the strip of material, whose reflectance is greater than that of the surface of the cylinder, is about to s' wrap around the circumference of the blanket cylinder. The differences in reflectance determined by the optical detector generate electrical signals which cause the whole machine to stop.

 Document EP 0 429 970 describes a switch which operates in the event of a tear in the strip. A strip processing machine, in particular a rotary printing machine, is equipped with at least one exploration device associated with the strip and having the form of a light barrier which can be interrupted by the strip. A signal is generated in the event of an inadmissible change in the position of the strip.

Each exploration device placed near a longitudinal edge of the strip is associated with a deflection device exerting a corresponding force which acts permanently on the area of the associated longitudinal edge of the strip, which the traction of the latter can overcome. during the walk without disturbance and with the help of which the longitudinal edge of the strip can be put in place with respect to the plane of the latter while running without disturbance. In the absence of traction, said deflection device can be moved relative to the exploration device.

 The document EP 0 533 043 A1 describes a photoelectric control device for the running of a strip or of a sheet, in particular of strips of paper in rotary printing machines.

 According to this document, an exploration device is provided which comprises a light source as well as a photosensitive receiver comprising an analysis and control system from which it is possible to deduce sequential operations of the printing machines. The exploration device includes a glass fiber optic. The individual light waveguides of this optic are on the one hand arranged in a line perpendicular to the strip of paper in movement, covering a width greater than the width of said strip.

 In addition, the light waveguides are grouped in a section transformer so that each picture element of a CCD (charge coupled by diode) sensor chip, which is integrated into the scanning device, can be enlightened. The CCD sensor chip is connected to the image analysis and control system. The light source is arranged opposite the glass fiber optic and perpendicular to the strip of paper in movement so that it also covers a width greater than the width of said strip. The strip of paper can pass between the light source and the glass fiber optics and can therefore be projected entirely onto the line of light waveguides.

 Finally, document EP 0 502 408 B1 describes a method and a device for controlling the position of a continuous web. The web continues to be treated receives a control radius, the reflection of which is received, the distance separating the emission and reception from the control radius is measured and a control pulse is generated when said a measured distance exceeds a prescribed width of strip. The prescribed bandwidth is a function of the speed of the continuous web.

The object of the present invention is to measure, without contact, the possible modifications of the position of a sheet of moving material in its transport plane in a processing machine in service. In case of unwanted positioning of the continuous web,
The invention allows the transmission of a control pulse to a control device. Thus the invention can detect the angle at which the web continues to treat adheres to the circumference of a cylinder before or after it tears.

 More particularly, the measurement and control device according to the invention comprises means for emitting at least one incident ray towards said continuous sheet and means for receiving at least one ray diffused on said continuous sheet. It is characterized in that the emission means comprise two radiation sources positioned so as to emit crossed incident rays which produce at different times couples of points of incidence on said continuous sheet, and in that the reception means comprise a CCD camera comprising pixels intended to receive at least a scattered fraction of said incident rays emitted, said pixels being capable of supplying electrical signals allowing the determination of a change in position of the continuous sheet.

 An advantage of the device according to the invention lies in the fact that simple components make it possible to create such a measurement and control device downstream of which an analysis electronics can be fitted, such a cheap analysis electronics making it possible to process the signals sent from the camera to CCD (charge coupling by diodc) in real time. This makes it possible to control the transport of the continuous ply and to react immediately to modifications of the transport parameters of the continuous ply such as for example the deviation of the ply with respect to a prescribed reference plane of transport. The measurement and control device according to the invention also makes it possible to detect and analyze cylinder vibrations, oscillations in the grooves of the cylinders, vibrations of the wall of the frame, vibrations of the sheet during and after the passage in grooves in the cylinders of the printing units.

 The CCD camera is particularly suitable for generating electrical signals; the light scattered at the points of incidence charges each of the pixels of the CCD camera, so that it is possible to directly generate electrical signals inside these pixels. These signals can either be sent to an analog / digital converter in order to convert an electrical charge into a digital value, or be sent to a threshold processing device in which a logic 0 or a logic 1 can be generated from the quantities determined by the CCD device.

The invention will be described in more detail by way of example, with reference to the accompanying drawings in which
FIG. 1 is a diagram of a measurement device according to the invention, downstream of which is mounted an analysis electronics either with analog / digital conversion, or comprising a Schmitt rocker,
FIG. 2 schematically represents in parallel different planes of transport of the continuous web, a reference plane and a deviated plane, as well as the angles and distances which result therefrom,
FIG. 3 is a diagram of a measurement and control device according to the invention, downstream of which is mounted an analysis electronics which processes the data in real time and which acts directly on the drives controls.

 Referring to Figure 1, a measuring device downstream of which is mounted an analysis electronics, is arranged above a continuous sheet of material 5. A CCD camera 10 and two inclined sources of radiation 1 1 and 12 are housed in a housing 9. The two radiation sources 11, 12 respectively emit rays 13, 14.

Note that only one radius, either 13 or 14, can be used. In this case, the device, which is less expensive, will also be less precise. The radiation sources 1 1 and 12 which can be used are both laser radiation sources as infrared radiation sources or any other sources of optical radiation. The CCD camera 10 here comprises a set of CCDs 10.1 in front of which a lens 10.2 is placed. The set of CCDs (charge coupling by diode) 10.1 can be an online set, or a matrix set. A set of CCDs comprises for example 1024 pixels in the longitudinal direction and 1 to 512 pixels in the transverse direction relative to the continuous web of moving material 5.

 The rays 13 and 14 emitted by the two radiation sources 1 1 and 12 intersect and are incident on the continuous sheet of material 5 at the points of incidence A and B. The incident rays arrive on the surface of said continuous sheet 5 according to angles of incidence a and ss. When the incident rays 13 and 14 arrive at the surface of the continuous sheet 5, a fraction of these incident rays is dispersed and another fraction is diffused towards a lens 10.2 and charges corresponding pixels from the set of CCD 10.1 of the camera. to CCD 10. The fact that the set of CCD 10.1 is in the form of a line or a matrix does not play any particular role.

 To correctly calibrate the measuring device, the CCD 10.1 assembly must first be adjusted so that it takes into account the diffuse radiation of daylight when the radiation sources 11 and 12 are inactive so as not to distort the charge of the pixels activated by the scattered fraction of the incident rays 13, 14.

 A reference distance Do between the lens 10.2 and the surface of the continuous ply 5 is preselected for the presetting of the measuring device. This distance Do as well as the maximum measurable range of deflection of the continuous sheet 5 conditions the resolving power of the measuring device according to the invention.

 The energy potentials of the individual pixels in the CCD 10.1 set are compared with each other and the positions of the points of incidence A and B and the distance between them are determined from the differences in energy potentials. The distance Do separating the lens 10.2 and the upper face of the continuous ply 5 therefore defines a reference position 15, that is to say a reference plane for transporting the continuous ply 5.

There are two possibilities for processing and analyzing the electrical signals from the pixels of the CCD 10.1 set. In FIG. 1, the electrical signals are sent in the signal conductor 17 and are converted in an analog-digital converter 18 into digital signals which can then be directed to a processor 19. It is also possible to provide a flip-flop 18.1, by example a toggle of
Schmitt, instead of an analog-digital converter 18. The flip-flop 18.1 can be adjusted so that if a threshold is exceeded, a logic 1 is generated, while for all the other values, therefore for the signals of output of the pixels of the set of CCD 10.1 which are below this preset threshold, the logic value 0 is generated.

 In the two aforementioned embodiments, the signals from the analog-digital converter 18 or the flip-flop 18.1 are directed to a processor 19. The processor 19 comprises a geometric computer, a digital filter. The geometric calculator determines the variations in the position of the continuous ply of material 5. The digital filter manipulates and filters the data making it possible to obtain the correct position of the continuous ply of material 5. The variations in position of said ply 5 can be converted in the frequency domain to detect critical frequencies. The results found by this processor 19 can be presented in the form of a graph or in digital form on the screen 21. The results can be recorded in a data storage device 24, for later use. In the processor 19, new distances Di calculated using the signals of the pixels of the set of CCD 10.1 are then emitted on a screen 21 of cathode-ray tube.

 In the representation of FIG. 2, the transport planes of a continuous ply in the reference position 15 and in the deflected position 16 are placed in parallel.

 As already described with reference to FIG. 1, the continuous ply 5 is in a reference position 15 as indicated by the dotted lines. At this reference position 15, the distance from the continuous ply 5 to the lens 10.2 is Do The points of incidence A, B as well as the corresponding angles of incidence determined at the reference position 15 are transmitted to the processor 19 which n is not shown in this figure.

An event such as a disturbance moves the continuous ply 5 from its reference position 15 to a deviated position 16. The deflection distance at an instant t1 is D1 and then the points of incidence A ', B' on the continuous ply at the deflected position 16, a distance different from that which exists between the points of incidence A, B on the continuous ply 5 at the reference position 15 is spread.
B 'corresponds, within the set of CCDs 10.1, to two new loadings of different pixels, compared to the previous position.

More precisely, in FIG. 2, as D1 moves away, the two exited pixels move away from the old position. The positions of the pixels in the set of CCDs 10.1 vary with respect to the variation in distance A'B 'on the sheet 5. The projection A1 from the point of incidence A to the reference position 15 on the continuous sheet 5 occupying the deflected position 16 makes it possible to determine the distance D1 by the angle a. This distance
D1 thus gives the magnitude of the deflection of the continuous ply 5 with respect to its reference position 15. Depending on whether this quantity is preceded by a positive or negative sign, the continuous ply 5 has been deflected up or down during transport. The angles a and B do not vary during the deviation of the continuous ply 5 from the reference position 15 to the deviated position 16, since it is an angle measured with respect to parallels. The lines connecting the points of incidence A, B located at the reference position 15 and the points of incidence A ', B' located at the deflected position 16 are only imaginary lines, the deflected position 1G of the sheet continues 5 corresponding to the projection plane in which the point of incidence A is projected in the form of an imaginary point of incidence
A1 to calculate D1.

 FIG. 3 represents a measurement and control device according to the invention which allows processing of the determined data in real time.

 The components and processes described in detail with reference to FIGS. 1 and 2 are incorporated into a control of a printing unit. The housing 9 housing the CCD 10.1 assembly and the lens 10.2 is shown in side elevation. The incident ray 13 crosses the reference plane 15 of the transport of the continuous ply and arrives on the surface of the continuous ply 5 in its deflected position 16.

 Both the analog-digital converter 18 and the flip-flop 18.1 are connected to a signal conductor 17 shown in Figure 3, however either one or the other of these components is used. The processor 19 performs the calculations of the modifications of distance Di and, in the particular case, for example at time t = tl, D1 = A'A1 tga corresponding to the distance from the point of incidence A to the point of incidence projected A1 at the real deviated position 16 of the continuous ply 5. The processor 19 determines during the continuation of the calculation operations whether the calculated distance separating the points A ', B' is greater or less than the distance separating the points incidence A, B at the reference position 15 of the continuous ply 5. If the distance separating the points A ', B' is greater than the distance separating the points A, B, the continuous ply 5 has moved away from the housing 9; if, on the other hand, the distance between the points A ', B' is less than the distance between the points A, B, the continuous sheet 5 has moved closer to the measuring device.

 The processor 19 includes a real time processor 19.1, as shown schematically in Figure 3, which allows the processing of process data in real time. The real-time processor 19.1 works by its very nature very fast. The real-time processor 19.1, for example the commercially available Tl 320 sc processor, transmits the data to an output 21 on a cathode ray tube screen to a data storage device 24 as well as a control device 27 for the drives 28 and 29 of printing groups 1 and 2.

 The processing of the process data in real time by the processor 19.1 allows control of the drives 28 ct 29 dc so as to optimize the continuous sheet of material 5. Thus, for example, in the event of too strong beating of the sheet, the voltage of said ply can be readjusted. If the continuous web 5 adheres to the circumference of a transfer cylinder 8 of a printing unit 1 or 2 in an unacceptable manner - if the deviation from the reference plane 15 exceeds a prescribed tolerable dimension -, a device d interception of the continuous web of material which is behind the first printing unit 1 is put into service. The device for intercepting said sheet can advantageously be arranged downstream of the first printing unit, can consist of two rollers or the like which face each other and is not part of the present invention.

Claims (11)

 1. Device for non-contact measurement and control of the position of a continuous traveling web in a machine for processing such a web, such as a rotary printing machine, device comprising means for emitting at least one ray incident 13, 14 towards said continuous sheet 5 and means for receiving at least one ray diffused on said continuous sheet 5, characterized in that the emission means comprise two sources of radiation (11, 12) positioned so as to emit crossed incident rays (13, 14) which produce at different times pairs of points of incidence (A, B, A ', B ') on said continuous sheet (5), and in that the reception means comprise a CCD camera (10) comprising pixels intended to receive at least a scattered fraction of said emitted incident rays (13, 14), said pixels being able to supply electrical signals allowing the determination of a change in position (Dj) of the continuous ply (5).  2. Device according to claim 1, characterized in that the determination of a change in position (Dj) of the continuous ply (5), generates the emission of a control pulse from the control device (27), case of unwanted positioning of the continuous web (5).  3. Device according to one of claims 1 and 2, characterized in CC that the CCD camera (10) comprises a CCD assembly (10.1) in front of which a lens (10.2) is mounted.  4. Device according to one of claims 1 to 3, characterized in CC that the CCD camera (10) and the radiation sources (11, 12) are arranged in a common housing (10).  5. Device according to claim 4, characterized in that the housing (10) is arranged in a fixed position relative to the continuous ply (5).  6. Device according to any one of claims 1 to 5, characterized in that the radiation sources (11, 12) are sources of laser radiation.  7. Device according to any one of claims 1 to 5, characterized in that the radiation sources (11, 12) are sources s. r infrared.  8. Device according to any one of claims 3 to 7, characterized in that the CCD assembly (10.1) is a matrix assembly.  9. Device according to any one of claims 3 to 7, characterized in that the CCD assembly (10.1) is an in-line assembly.  10. Device according to claim 8, characterized in that the CCD assembly (10.1) in the form of a matrix comprises 1024 pixels in longitudinal direction and 1 to 512 pixels in transverse direction.  11. Device according to any one of claims 1 to 10, characterized in that there is provided a processor (19) mounted downstream of an analog-digital conversion (18) capable of converting the electrical signals supplied by the pixels receiving the broadcast fraction of the incident signals emitted.