US Patent 7493697 Lawn mower

A lawn mower comprises an operation arm, a driven shaft rotatably supported inside the operation arm and having two opposite ends, a cutter operatively connected to one end of the driven shaft, a power source operatively connected to the other end of the driven shaft for generating a drive power to be transmitted to the cutter through the driven shaft, wherein said power source is selective from an engine and an electric motor, an arm side joint case provided on the end of the operation arm, a power source side joint case provided on a housing of the power source and detachably and selectively connected to the arm side joint case, and a centrifugal clutch incorporated in the arm side joint case and having a first member connected to the driven shaft, a second member detachably and selectively connected to the power source and a third member provided to engage the first member and the second member according to the centrifugal force applied thereto.