Dust collection box

A dust extractor for a power tool comprising a dust collection box, wherein the dust collection box comprises:

• a housing having a plurality of walls including a rear wall, a front wall, and two side walls extending from the rear wall to the front wall;
• an air inlet chamber formed within the housing;
• an air inlet aperture formed in at least one of the plurality of walls of the housing, wherein air is drawn through the air inlet aperture into the air inlet chamber;
• an air outlet chamber formed within the housing;
• an air outlet aperture formed in at least one of the plurality of walls of the housing, wherein air is drawn through the air outlet aperture out of the air outlet chamber by a vacuum source;
• an air intermediate chamber formed in part by the rear wall of the housing and located within the housing;
• a filter mounted within the housing, the filter including a first part through which air passes from the air inlet chamber to the air outlet chamber, and a second part through which air passes from the air inlet chamber to the air intermediate chamber;
• a valve located between the air intermediate chamber and the air outlet chamber;
• and
• an ambient air aperture formed in the rear wall of the housing adjacent a part of the rear wall of the housing that forms the air intermediate chamber and in communication with the valve, the ambient air aperture arranged to receive ambient air in communication with the valve;
• wherein the valve is switchable between a first position, where air passes from the air intermediate chamber to the air outlet chamber and the valve substantially seals the ambient air aperture, and a second position, where air passes from the ambient air aperture to the air intermediate chamber and the valve substantially seals passage of air from the air intermediate chamber to the air outlet chamber.