Patent ID: 8360168

Claim:
A power tool comprising: a driving mechanism to drive a tool bit, an enclosed housing space which houses the driving mechanism and in which lubricant to lubricate the driving mechanism is sealed in, a path which communicates the housing space with the outside to regulate pressure of the housing space, a filter chamber having a predetermined capacity provided on the path, an inner passage provided on the path to communicate the filter chamber with the housing space, an outer passage provided on the path to communicate the filter chamber with the outside are formed on the path, a filter disposed in the filter chamber to absorb lubricant, the filter spaced apart from a peripheral edge of an opening of the outer passage which is open to the filter chamber, so that a space is formed on the opening edge side of the filter chamber, and a throttle disposed in the space to throttle flow of air which flows out to the outer passage through the filter, wherein the throttle member includes a sheet member which is overlaid on top of the filter and throttles a passage between the filter and the space, the sheet member being formed of circular elastic material.