In the classical Float and Solar Glass lehr design the rollers are driven by a centralized shaft, which provides the same rotational speed for each roller. This system is basically safe, but in the event of a disturbance (failure) very critical for the rollers themselves. Technologically the system with its open sprockets and oil pans has been state of the art 25 years ago.
The main disadvantage is to be seen in the same rotational speed of each roller. The glass enters the lehr at a temperature of approx. 600°C and cooled to approx. 70°C. During this process it thermally shrinks and will lead to a relative movement of the glass on the rollers itself. This will result in a scratching of the glass surface (Micro Scratches). Due to the reduction of the rotational speeds (offset) of the rollers, according to the temperature of the glass, such effect may be avoided, whereas the LOR’s are operated as the master drives.