Patent ID: 8020630

Claim:
An impact mechanism comprising: a hammer defining a hammer axis and including a hammer lug, a cam lug spaced from the hammer lug, and a recess between the hammer lug and the cam lug; an anvil defining an anvil axis that is generally parallel to but non-collinear with the hammer axis, the anvil including a jaw extending substantially parallel to the anvil axis, an engaging cam surface, and a flange generally perpendicular to the anvil axis and interconnected with the jaw; and a connector adapted to mount to a motor output shaft and rotate in response to rotation of the motor output shaft, the connector including a disengaging cam surface bearing against the cam lug to cause the hammer to orbit the anvil in response to rotation of the connector; wherein a portion of the flange is received within the recess of the hammer between the hammer lug and the cam lug for at least a portion of the orbital movement of the hammer about the anvil; wherein the hammer is pivoted about the hammer axis into an engaged position in response to a portion of the hammer moving along the engaging cam surface of the anvil, the hammer lug striking the jaw of the anvil when the hammer lug is in the engaged position and the hammer is moving at a rate in excess of a critical speed, the hammer lug striking the jaw causing rotation of the anvil about the anvil axis; and wherein the hammer is pivoted about the hammer axis into a disengaged position prior to the hammer striking the jaw of the anvil in response to the disengaging surface of the connector bearing against the cam lug while the hammer is moving at a rate below a critical speed, such that the hammer lug moves past the jaw of the anvil.