US Patent 9108284 Dust collection device for power tool and power tool

In a dust collection device attached to a hammer drill, a filter is provided in a dust box at a position at which the filter covers an outlet provided on a rear face of a lid body, in a state such that a filter surface projects into the dust box from the rear face of the lid body. A space is formed between an inner face of a box main body and a side face of the filter that is adjacent to the filter surface. Air outlets are provided to guide air, which flows in through an inlet, toward the space.