Web-guiding or sheet-guiding mahcine, and method of operating the same

Web guiding or sheet guiding machine, in which the webs or sheets are conveyed along a transport path (z), comprising at least one roller nip,

• at least one of the rollers, which bounds the roller nip or is situated downstream of the roller nip on the transport path, being drivable by an electric drive,
• the electric drive being assigned a power divider,
• the web guiding or sheet guiding machine being equipped with a safety device, which can monitor whether foreign bodies are penetrating into the roller nip and/or whether a specified torque for the drive is being maintained,
• the safety device comprising a first measuring device, which can monitor at least a first electrical variable of the power, made available to the drive by the power divider,
• the safety device comprising a second measuring device, which can measure a second physical variable, this second physical variable having a functional relationship with the first electrical variable,
• the safety device comprising a computer module, by means of which the time profiles of the two variables can be compared with each other, and in the event. of deviations in the time profiles, alarm signals can be generated,
• characterized in that
• the first measuring device can monitor the torque-forming current,
• the second measuring device can monitor a mechanical variable, which is connected to the web mechanism,
• and on the basis of the measured values of the second measuring device the correct function of the first measuring device can be monitored.