To prevent the operation discontinuation by the generation of a deadlock by forming an intermittent disc at least partially from especially a light material, favorably aluminium alloy in comparison with the material of a grid disc.

Each grid roller 1 has a central mandrel, in which a carrying disc 7 and intenaediate disc 8 are arranged alternately. The degree/weight of a deadlock is reduced by forming the carrying disc and/or intermediate disc at least partially from especially a light material, favorably aluminium alloy in comparison with the material of the grid disc. As the carrying disc 7 is loaded extremely and mechanically and exposed to the wear thereby, only the central part of the carrying disc 7 is formed by a light metal and favorably a replacable wear member is installed on the outer periphery of the carrying disc 7.