Sweeper with precleaner and/or demister

Claim 1

In a sweeper, a mobile frame, wheels for the frame providing for its movement, a generally horizontal rotary brush on the frame adapted to propel debris from a surface to be cleaned, a debris receiving hopper with an inlet opening therein on the frame adapted to receive debris thrown by the brush, two chambers in the hopper, one chamber being a debris chamber for receiving debris from the brush and the other being a filter chamber with a filter unit therein, a vacuum fan on the frame for exhausting air from the hopper and connected to the filter chamber to reduce dusting and to draw air through the filter unit, an opening between the chambers remote from the brush providing for an air flow from the debris chamber to the filter chamber to reduce dusting around the sweeper, and a precleaner for separating some of the dust particles passing through the opening between the debris chamber and the filter chamber constructed and arranged to separate dust particles entrained in the airstream created by the vacuum fan before the airstream enters the filter chamber from the debris chamber, the precleaner including two spaced plates with a series of openings in each plate, the openings in one plate being offset relative to the openings in the other plate, the openings having a smaller dimension than the distance between the openings so that an opening in one plate is overlapped by a plate area in the next plate, thereby requiring the airflow to change direction in flowing from the openings in one plate to and through the openings in the next plate.