Web-Guiding or Sheet-Guiding Machine, and Method of Operating the Same

Abstract

The invention relates to a web-guiding or sheet-guiding machine, in which webs or sheets are transported along a transport path (z), and which has at least one roller nip, it being possible for at least one of the rollers, which delimits the roller nip or is located downstream of the roller nip on the transport path, to be driven by an electric drive. A power controller is assigned to the electric drive, and the web-guiding or sheet-guiding machine is equipped with a safety device, which makes it possible to 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 here comprises a first measuring device, which can monitor at least one first electric variable of the power made available to the drive by the power controller. The safety device comprises a second measuring device, which can measure a second physical variable having a functional relationship with the first electric variable. The safety device comprises a computer module by means of which the time sequences of the two variables can be compared with one another and warning signals can be generated in the event of deviations in the time sequence.

1 . 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.   
   
   
       2 . Machine, as claimed in the preceding claim, characterized in that the mechanical variable is the web tension and/or the web speed. 
   
   
       3 . Machine, as claimed in  claim 1 , characterized in that the second measuring device comprises at least one rotary encoder and/or a contactiess, web-detecting sensor and/or at least one compensator roller and/or at least one measuring roller with a force measuring device. 
   
   
       4 . Machine, as claimed in  claim 1 , characterized in that the second measuring device also exhibits measuring means and/or control modules, which can consider the influence of the web elongation. 
   
   
       5 . Machine, as claimed in  claim 1 , characterized in that the second measuring device can also measure electrical variables. 
   
   
       6 . Method for operating a web guiding or sheet guiding machine, 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 driven by an electric drive,   and a power divider provides power for the electric drive,   during normal operation of the machine, a safety device is added, and this safety device monitors whether foreign bodies are penetrating into the roller nip and/or whether a specified torque for the drive is being maintained,   to this end the safety device monitors with a first measuring device at least a first electrical variable of the power, made available to the drive by the power divider,   the safety device measures with a second measuring device a second physical variable, this second physical variable having a functional relationship with the first electrical variable,   the safety device compares with a computer module the time profiles of the two variables, and, in the event of deviations in the time profiles, generates alarm signals, characterized in that   the first measuring device monitors the torque-forming current,   the second measuring device monitors 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 is monitored.