US Patent 7497886 Dust extraction for power tools

There is also provided a dust extraction module for use with a power tool, the dust extraction module having: a dust collection chamber (50) having an inlet (52) connectable in fluid communication with an outlet (44) of a dust-extracting duct (40) of the power tool, and having an outlet (54) in fluid communication with atmospheric air; and a filter (60) locatable in fluid flow between the outlet of the dust collection chamber and the atmospheric air; wherein the dust collection chamber (50) has a substantially circular cross section, the inlet (52) to the dust collection chamber is at the perimeter of the circle and the outlet (54) of the dust collection chamber is from the middle of the circle.