These sensors are used to prevent the blocks on the individual cranes from moving. They are used all over the world in all environmental conditions. It is a safety device and must therefore be fail-safe and extremely robust. The switch used to be fixed onto the end of the crane boom. Depending on the angle of the sensor cable and the steel weight relative to the switching body, a misalignment would take place, which could potentially have a negative effect on the function of the switch. A switch with a metal or Teflon-coated bearing would be too expensive and require too much maintenance. The new design uses shoulder bolts as shafts and allows the assembly two degrees of rotational freedom. Irrespective of the angle of the crane boom, the sensor cable for the switch is always pulled straight through the switching body without there being any chance of misalignment. "igus® bearings enable maintenance-free operation - no lubrication is necessary, and they work in all environmental conditions where our switches are found. That makes a perfect pair."