A distributed computing system conforms to a multi-level, hierarchical organizational model. On the other hand, in a cleaning device, a dust collection member is installed so as to make contact with the shield plate and holding plate. The push rod is manually movable with respect to the housing to induce a horizontal movement, which is converted into a rotary motion of the cover by a linkage mechanism that has a lever forming a groove movably receiving and guiding the cover. The drive coupling is arranged to inter-fit with a portion of the or each drive shaft.