| 摘要 |
The present invention relates to a device to prevent damage to printing groups of web-fed rotary presses that print webs fed by a cylinder which is placed on a reel changer. A fault detector is provided that has a deflection device next to both web edges. It can create a deflective force transverse to the web plane transport, which can be overcome by the tension of the web during normal operation. A monitor is also provided that detects changes. With the aid of this device, damage to printing groups can be prevented (especially arising from defects occurring during reel exchange) by locating the fault detection device in front of the first printing group of the web-fed rotary press, and each of the two monitors of the fault detector is designed as an optical sensor that emits a signal which depends on shading by the web, and its optical axis is tilted in the lengthwise direction of the web in relation to the direction of the deflection force that is essentially perpendicular to the transport plane of the web.
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