DE20103070U1 - Camera surveillance - Google Patents

Description

Voith Paper Patent GmbH file: PC11215 DE Sankt Pöltener Strasse 43 "Rail Break Detection" D-89522 Heidenheim Camera surveillance

The invention relates to a device for optically detecting the surface structure of a paper, cardboard, tissue or other fibrous web in a press section of a machine for producing the same using a camera.

So far, no solutions are known that enable the surface structure of the fibrous web to be recorded during normal operation. The biggest problem is the susceptibility of the measuring system to failure, particularly in the press section due to contamination and moisture.

On the other hand, knowledge about the surface structure or even a tear in the fibrous web offers opportunities to influence the production process very quickly, which has a positive effect on the quality of the fibrous web and the failure rate.

The object of the invention is therefore to make the optical detection of the surface structure of a fibrous web in a press section as reliable as possible.

According to the invention, the object is achieved in that the camera has a contamination protection for the camera lens, which in normal operation at least partially, preferably as comprehensively as possible, limits the area between the camera lens and the fibrous web at the sides without coming into contact with the fibrous web. This contamination protection shields the endangered area as far as possible and thus enables the camera to be used for longer periods.

In order to ensure sufficient brightness despite the pollution protection, it is advantageous if the pollution protection and/or the camera have a

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have an illumination device directed directly or indirectly at the surface of the fibrous web to be detected.

Particular problems often arise when starting up the production machine, i.e. when inserting the fibrous web or a strip of it. This is due in particular to the unstable running of the fibrous web and the increased risk of web breaks during the start-up phase. In this context, it is advantageous if the contamination protection has a controllable cover for the camera lens. This cover protects the camera lens very reliably during the insertion of the fibrous web and can be swung away during normal operation.

There are also advantages if the camera is mounted so that it can pivot at least in the direction of web travel, preferably together with the contamination protection. In conjunction with the cover, but also on its own, the protection of the camera can be improved by pivoting the camera away during start-up of the production machine.

To counteract the risk of contamination of the camera lens or even damage, the camera should be tilted in the direction of web travel at an angle between 0 and 45°, preferably between 10 and 30" during normal operation. Particularly safe operation of the device is achieved if the contamination protection has compressed air nozzles to remove contamination from the area between the camera lens and the fibrous web.
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The invention will be explained in more detail below using an exemplary embodiment. In the attached drawing, the figure shows a schematic representation of the device according to the invention when used at the beginning of a press section of a paper machine for dewatering a fibrous web 1.
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The fibrous web 1 is here formed by a forming screen 11 of an upstream former

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for sheet formation. This removal takes place through the upper press felt 12 of the subsequent press nip of the press section, which is supported by a suction-fed guide roller 13.

A press felt 12 is guided on both sides of the fibrous web 1 through the press nip formed by two press rollers 14, which greatly limits the observation area for the fibrous web 1.

The surface structure of the fibrous web 1 is recorded here by several cameras 2 arranged next to one another transversely to the web direction 9. Digital high-speed cameras with a resolution of at least 100 pixels/mm ² are particularly suitable for this. With a surface of the fibrous web 1 to be recorded of approximately 100 x 100 mm ² , this requires a recording frequency of more than 300 Hz, in particular even more than 400 Hz, at high web speeds.

For evaluation, the camera system is connected to a control and regulation unit 15. In the event of structural defects, weak points or even a tear, the control and regulation unit 15 can influence the production process accordingly. As a result, the quality of the fibrous web 1 improves and the damage caused by web tears is reduced.

A longer use of the camera 2 in this extremely stressed environment of the press section with regard to dirt and moisture is made possible by the dirt protection 3, which mainly laterally limits the area 5 between the fibrous web 1 and the camera lens 4. This is done by means of a conical ^casing of this area 5, with the dirt protection 3 being spaced apart from the fibrous web 1.

An illumination device 7 of the camera 2 ensures sufficient brightness of the surface 6 of the fibrous web 1 to be detected.

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In order to adequately protect the camera 2 or the camera lens 4 when starting up the paper machine, i.e. when inserting the fibrous web 1, the contamination protection 3 has a pivoting cover 8 which closes the contamination protection 3 when starting up and when at a standstill.
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The camera 2 is pivotably mounted together with the contamination protection 3. This enables pivoting during the start-up of the paper machine, but also improves accessibility.

The risk of contamination is further reduced by the fact that the camera 2 together with the contamination protection 3 is inclined at an angle of approximately 25° in the web travel direction 9.

The contamination protection 3 also has compressed air nozzles 10 for removing contamination from the area 5 between the camera lens 4 and the fiber web 1.

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Claims (6)

1. Device for optically detecting the surface structure of a paper, cardboard, tissue or other fibrous web ( 1 ) in a press section of a machine for producing the same using a camera ( 2 ), characterized in that the camera ( 2 ) has a contamination protection ( 3 ) for the camera lens ( 4 ) which, during normal operation, at least partially, preferably as comprehensively as possible, laterally delimits the area ( 5 ) between the camera lens ( 4 ) and the fibrous web ( 1 ) without coming into contact with the fibrous web ( 1 ). 2. Device according to claim 1, characterized in that the contamination protection ( 3 ) and/or the camera ( 2 ) have an illumination device ( 7 ) directed at the surface ( 6 ) of the fibrous web ( 1 ) to be detected. 3. Device according to claim 1 or 2, characterized in that the contamination protection ( 3 ) comprises a controllable cover ( 8 ) of the camera lens ( 4 ). 4. Device according to one of the preceding claims, characterized in that the camera ( 2 ) is preferably pivotally mounted together with the contamination protection ( 3 ) at least in the web travel direction ( 9 ). 5. Device according to one of the preceding claims, characterized in that the camera ( 2 ) is inclined in normal operation at an angle between 0 and 45°, preferably between 10 and 30° in the web travel direction ( 9 ). 6. Device according to one of the preceding claims, characterized in that the contamination protection ( 3 ) has compressed air nozzles ( 10 ) for removing contamination from the area ( 5 ) between the camera lens ( 4 ) and the fibrous web ( 1 ).