Patent ID: 7506693

Claim:
A hammer comprising: a housing; a motor mounted within the housing; a tool holder mounted on the housing for holding a cutting tool; a ram mounted for axial movement within the housing; a spring mounted coaxially with the ram; a barrel cam for converting rotary input from the motor into an axial drive output; a drive member driven by the barrel cam to reciprocate in the axial direction; a drive arm pivotably mounted on a pivot point at a first location and contacting the spring at a second location and acted on by the drive member at a third location; a wheel mounted on an axis for rotation, and the pivot point of the drive arm is located on the wheel at a point radially outward from the axis, so that rotation of the wheel moves the pivot point in order to adjust the third location on the drive arm; and wherein the drive arm acts between the drive member and the spring to transfer the axial reciprocation of the drive member to the ram via the spring and the third location on the drive arm is adjustable, so as to vary the amount of axial movement transferred from the drive member to the spring.