A control for a working apparatus having a boom arm. Each filter stick includes a plurality of filter disks stacked about a fluid-pervious tube with a hollow core and retained about the tube by a retainer at each end. The paper feed roller according to the present invention includes a rotary shaft, a cylindrical roller portion formed by press molding a mixture of a hydraulic composition, followed by curing and hardening, and integrated with an outer periphery of the rotary shaft. In some devices, at least 5% of all light reflected by the third reflector region traveled directly from the first reflector region to the third reflector region. The contact regions are laterally offset with respect to one another.