EP0892754A1

EP0892754A1 - Sheet-guiding suction box

Info

Publication number: EP0892754A1
Application number: EP97920566A
Authority: EP
Inventors: Gerald Josef Reinhard; Johannes Georg Schaede
Original assignee: Koenig and Bauer AG
Current assignee: Koenig and Bauer AG
Priority date: 1996-04-02
Filing date: 1997-04-01
Publication date: 1999-01-27
Anticipated expiration: 2017-04-01
Also published as: JPH11509506A; DE59701042D1; US6176482B1; EP0892754B1; WO1997036813A1; DE19613084A1; ES2142678T3

Abstract

The object of the invention is to adapt a sheet-guiding suction box to the sheet format. According to the invention, this object is achieved by a central suction chamber whose extension is smaller than the smallest format of a sheet to be guided.

Description

description

Suction box for guiding sheets

The invention relates to a suction box for guiding sheets according to the preamble of claim 1.

The invention has for its object to provide a suction box for guiding sheets.

This object is achieved by the features of the characterizing part of claim 1.

The suction box according to the invention can advantageously be adapted to the format of sheets. As a result, downflow of air is avoided and a constant suction power is achieved even with formats of different sizes. With large formats, corners and edges tend to flutter more. In order to avoid fluttering of the corners, independently controllable suction chambers are provided.

It is particularly advantageous to use this suction box with inspection systems, because it is necessary for inspection systems to guide sheets that are to be inspected quietly and flutter-free, at least during image recording. In the remaining areas of a sheet transport rec ke this is not absolutely necessary, so that the increased technical to flutter-free guidance Effort can be avoided.

Using an integrated sensor that can be moved in the direction of transport, it is possible to trigger the image acquisition in such a way that the sheet is in the middle of a CCD area camera of the Inspe ct 1 ons system during the exposure.

The device according to the invention is shown in the drawing and is described in more detail below.

Show it

Fig. 1 is a schematic side view of a

Device for the qualitative assessment of printed sheets;

Figure 2 is a schematic view of a device for qualitative assessment in transport direction of the printed sheets.

Fig. A schematic plan view of a suction box of the device for qualitative assessment of printed sheets;

4 is a perspective view of the device,

A device for the qualitative assessment of processed material 1 consists essentially of a guide 2, a lighting device 3, at least one sensor 4 and a downstream evaluation unit.

This quality control system can be used to monitor both webs and sheets 1 in a rotary printing press or

Processing machine can be used. In the present exemplary embodiment, the quality control system is used in a sheet-fed rotary printing press for securities, in particular for banknotes.

Sheets 1 to be inspected are transported, for example, by means of gripper systems 6 in a sheet transport plane 7. These gripper systems 6 are attached to rotating chains 8 of a chain conveyor known per se. Above the sheet transport level 7, the guide 2 is arranged. This guide 2 has the arch, for example

1 facing guide surface 9 has a curved shape in the transport direction T. This guide surface 9 is thus concave in transport direction T and has a radius of curvature R9, z. B. R9 = 800 mm. The leadership

2 is designed, for example, as a suction box 2. For this purpose, the guide surface 9 is provided with a plurality of perforations 11, ie the guide surface 9 is formed by a perforated plate. The perforations 11 have a diameter of 2 mm, for example, and are in spaced 3mm apart. This guide surface 9 is interchangeable (with different perforations) and can be opened for maintenance work.

Partition walls are arranged within the suction box 2, so that a number of independently acting, separately controllable suction chambers 12 to 23 is formed. In the middle of the suction box 2, an area corresponding to the smallest format of the sheets 1 to be processed is divided in transport direction T into a front 12 and rear suction chamber 13. On the four sides of this rectangular area there is another suction chamber 14, 16, 17, 18. In addition to these suction chambers 14, 16, 17, 18, four suction chambers 19, 21, 22, 23 are again arranged in the direction of the outer edges of the sheet 1, the in

Transport direction T extending outer suction chambers 21, 23 can be divided again.

A negative pressure in the individual suction chambers 12 to 23 is individual, for. B. by means of bypass control, adjustable. Thus, a holding force acting on the sheet 1 on z. B. format, material or processing of the sheet 1 can be adjusted.

The lighting device 3 and the sensor 4 are arranged opposite the suction box 2. The lighting device 3 has a V-shaped cross section in the transport direction T, ie it is designed as a V-shaped box 24. This box 24 points two legs 26, 27 with flat faces 28, 29 which face the sheet 1 to be inspected facing towards the left. These legs 26, 27 enclose an opening angle alpha of, for example, 122 °. This opening angle alpha preferably has a range from 90 ° to 150 °. Each of the two light exit surfaces 28, 29 is trapezoidal. The shorter of the two base sides 31, 32 abut each other and run parallel to the transport direction T. The two short base sides 31 have a length 131 of z. B 350 mm. The two larger base sides 32 with a length 132, z. B. 132 = 560 mm also run parallel to the transport direction T and are transverse to the transport direction T at a distance a32, z. B. a32 = 1220mm, spaced, which corresponds to a width b3 of the lighting device 3. This distance a32 is greater than a greatest width b1, z. B. 840 mm, the sheet to be inspected 1.

The size and shape of the lighting device is therefore adapted to the format of the sheets to be inspected. The light exit surfaces 28, 29 consist for example of milk glass panes. A plurality of diffusely radiating light sources are arranged under each of these milk glass panes. These light sources are designed, for example, as single flash tubes. This arrangement of light sources and milk glass panes achieves particularly uniform illumination of the sheets 1 to be inspected. The lighting device 3 can instead of V-shaped cross-section also have a curved, for example circular-arc-shaped cross-section,

A plurality of guide webs 33 (“shutter”) running parallel in the transport direction T can also be placed on the milk glass pane. These guide webs 33 can, for example, be made from sheet metal or also from frosted glass. An angle of inclination of these guide webs 33 with respect to the light exit surfaces 28, 29 or arc transport plane 7 is adapted to run approximately parallel to a light beam, such a light beam directed between two guide webs 33 striking a reflecting area of the sheet 1 after reflection there on the sensor 4.

These guide webs 33 are at a distance a33, z. B. a33 = 20 mm.

The lighting device can also consist of several individually arranged light sources.

The sensor 4 is arranged in a center of this lighting device 3. In the present example, a CCD area camera 4 with an upstream lens is provided as the sensor 4. The lens is designed in the present example such that the entire sheet 1 to be inspected is detected, ie a distance between the CCD area camera 4 and the sheet transport plane 7 is adapted to the lens of the CCD area camera 4. But it is also possible capture several parts one after the other and combine them into a total picture. The sheet 1 to be inspected is located in the optical axis of the lens of the CCD area camera 4.

In the suction box is in the present

Embodiment built a nig tardar l lter sensor acting as a trigger. This sensor detects the front edge of the sheet 1 to be inspected and triggers the inspection process. This sensor is arranged so as to be adjustable in transport direction T in order to align the position of the sheet in the case of sheet sizes of different sizes such that the inspection takes place approximately in the center of the lens of the CCD area scan camera 4.

An evaluation device is connected downstream of the CCD area camera 4.

A picture of the sheet 1 to be inspected is in a

Matrix consisting of a multitude of small ones

Picture elements, i.e. Pixels, divided. Each of these

Pixel is an exact location by specifying it

Coordinates in X and Y direction of a Cartesian

Coordinate system assigned. In addition, his

Reflectance value, e.g. B. its gray value, a value Z determining this. Each pixel P (X, Y, i i i Z) is thus given the values X, Y, Z in

1 1 1 1

Location and size precisely determined.

The light reflected from the sheet 1 on the individual pixels P is correspondingly obtained by the CCD area camera 4 its amount converted into an electrical analog signal. This analog signal is fed to an A / D converter, which forms the digital values Z therefrom. Usually the range of values is broken down into 0 to 255 discrete values. In this case, the value 0 means no remission hitting the corresponding pixel P of the i CCD area camera 4, while 255 corresponds to maximum remission.

In the present application, the sheet 1 to be inspected has reflecting surfaces. Under

In this context, “reflective” is to be understood to mean that directed, reflecting on the surfaces

Light rays with weak scatter and noticeably directed portion are reflected. Such areas can in particular be silver threads of a banknote or, for example, holograms or kinegrams. These reflective surfaces must be recognized as such.

A value range is now assigned to the values of the pixels P of such a sheet 1 in such a way that the occurring one

Range of values outside the reflective surfaces is clearly within the limits 0 and 255. In the

Practice then becomes, for example, the color "white"

Value Z from 180 to 200 and the color "black" assigned a value i Z from 10 to 30. i This assignment is made using, for example

Setting the brightness of the lighting device

3, the amplification of the camera signal in the Evaluation electronics or an aperture of the lens of the CCD area camera 4.

The sheet 1 is illuminated uniformly by means of the lighting device 3 in such a way that any surface located at any point on the sheet 1 and which has almost ideally reflecting properties, an incident light beam directly into the

CCD area camera 4 reflected. At least partially directed light beams are used for this.

The associated value Z of a pixel P takes i i

A value that differs significantly from one of the

Color "white" assigned value differs.

For example, the value Z of a pixel P 230 to i 255 assigned to an i reflecting surface then reaches.

Areas with reflective surfaces are thus above the

Assignment of extreme values Z clearly defined, i.e. i Areas that are weakly scattered with noticeably directed

Shares are differentiated from diffuse reflecting areas.

The pixels assigned to the reflecting surfaces are then recognized as such by the evaluation electronics and are processed accordingly. Reference list

1 sheet, material

2 suction box, guide

3 lighting device

4 CCD area scan camera, sensor

5

6 gripper system

7 sheet transport level

8 chain

9 guide surface (2)

10

11 holes

12 suction chamber

13 suction comb r

14 suction comb r

15

16 suction chamber

17 suction chamber

18 suction chamber

19 suction chamber

20th

21 suction chamber

22 suction comb r

23 suction chamber

24 boxes

25

26 legs (24)

27 legs (24) 28 light exit surface (3)

29 light exit surface (3)

30 31 base 32 base

33 control board

a32 distance between base sides (32) a33 distance between guide rails (33)

b1 width of the arches (1) b3 width of the lighting device (3)

R9 radius of curvature of the guide surface (9)

131 length of the base side (31)

132 length of the base side (32)

alpha opening angle

Claims

Expectations

1. suction box (2) for guiding sheets (1) with a plurality of independently acting suction chambers (12 to 23), characterized in that at least one central suction chamber (12, 13) is arranged and that its extension is smaller than the smallest Format of a sheet to be guided (1).

2. Suction box according to claim 1, characterized in that two independently acting suction chambers (12; 13), the central suction chamber (12, 13) are provided bi ldend.

3. suction box (2) according to claim 1, characterized in that a planar projection of a guide surface (9) in the area of the central suction chamber (12, 13) is rectangularly formed.

4. Suction box (2) according to claim 1, characterized in that on both sides in transport direction T extending sides of the central suction chamber (12, 13) at least one further suction chamber (16; 18; 21; 23) is then arranged.

5. suction box (2) according to claim 1, characterized in that extending transversely to the transport direction T sides of the central suction chamber (12, 13) at least jewei ls a further suction chamber (14; 17; 19; 22) subsequently arranged is.

6. Suction box (2) according to claim 1, characterized in that the suction box (2) has a curved guide surface in transport direction T (9).

7. suction box (2) according to claim 1, characterized in that the guide surface (9) of the suction box (2) of a device (3, 4) for the qualitative assessment of sheets (1) is arranged opposite.

8. suction box (2) according to claim 1, 2 or 3, characterized in that a negative pressure in the suction chambers (12, 13) is individually adjustable.

9. suction box (2) according to claim 1, characterized in that a guide surface (9) of the suction box (2) is interchangeable.