Vibration reduction apparatus for power tool and power tool incorporating such apparatus

摘要

A vibration reduction apparatus (501) for use with a hammer tool having a hammer piston (520) is shown. The hammer piston (520) is caused to reciprocate in cylinder (530) by rotation of a gear wheel (523) about axis (524), the hammer piston (520) being mounted to the gear wheel (523) via piston arm (531) and pivot pin (522). Reciprocating motion of the hammer piston causes a flying mass (569) to be driven along cylinder (530) to impart a hammer action to a bit of the tool. The gear wheel (523) is caused to rotate about axis (524) by meshing of gear (514) on drive shaft (511) with gear teeth (532) on the periphery of gear wheel (524), the drive shaft (511) being caused to rotate by a motor (not shown) of the tool. A cam (533) is rigidly mounted around gear wheel (523), a counterweight (521) surrounds piston cylinder (530), and a cam follower (534) is provided on counterweight (521). The cam follower (534) on counterweight (521) is urged into contact with cam (533) by means of a compression spring (535). The external profile of the cam (533) is such that rotation of gear wheel (534) to cause reciprocating motion of hammer piston (520) causes oscillation of counterweight (521) relative to piston cylinder (530) in antiphase to motion of the hammer piston (520) to counteract vibrations produced by operation of the hammer action of the tool.