Patent ID: 6640764
Filing Date: 2003-11-04
Classification: F02B

Abstract:
A portable power tool comprising:an internal combustion engine including a crankshaft that rotates about a first axis, at least one piston that reciprocates along a second axis, the piston being operatively connected to the crankshaft, wherein a load applied to the crankshaft is unevenly distributed along the first axis of the crankshaft with respect to the second axis of reciprocating movement of the piston; an operational member fixed to one end of the crankshaft and driven by the internal combustion engine; a rotational body fixed to another end of the crankshaft to which a smaller component of the load is distributed; and a balancing weight provided on the rotational body, for absorbing vibration generated by the reciprocating movement of the piston at the one end of the crankshaft to which a larger component of the load is distributed, wherein a centroid of the balancing weight is disposed at an angular position that is from 140 degrees to 180 degrees with respect to the second axis of the reciprocating movement of the piston in a rotational direction of the rotational body, when the piston is positioned at a top dead center.