Patent ID: 7971654
Filing Date: 2011-07-05
Classification: B25B

Abstract:
1. A rotary impact tool comprising: a drive shaft rotationally driven by a rotational drive power source, the drive shaft having an outer circumferential surface and a cam groove formed on the outer circumferential surface; a hammer arranged around the drive shaft, the hammer having an inner circumferential surface and a cam groove formed on the inner circumferential surface; a ball engaging with the cam groove of the drive shaft and the cam groove of the hammer; an anvil engageable with the hammer along a rotational direction; and a spring for biasing the hammer toward the anvil, wherein the cam groove of the drive shaft and the cam groove of the hammer cause the hammer to rotate about an axis extending along a longitudinal direction of the drive shaft such that a fixed point on the hammer generates a locus of points that form a curve when plotted in a development view, and a lead angle of the rotational locus varies continuously as the hammer rotates.