| 摘要 |
A power shovel including a stiffleg, a dipper handle operatively connected to the stiffleg, a dipper having a forwardly disposed digging end pivotally connected to the dipper handle, the dipper being biased to pitch the forwardly disposed digging end thereof upwardly, means for limiting the upward pitch of the digging end of the dipper relative to the dipper handle, a hoist frame pivotally connected to the stiffleg, and a hoist link pivotally connected at the ends thereof to the hoist frame and to the dipper defining a four bar linkage. Such linkage is provided with a geometry wherein the point of intersection of the longitudinal centerlines of the hoist link and the dipper handle is confined to the third quadrant of a set of coordinates having the center of gravity of the dipper and any material disposed therein defining the origin of the set of coordinates, the coordinates being parallel and perpendicular to a longitudinal centerline of the dipper and the third quadrant thereof including the forwardly disposed digging end of the dipper, and the point of intersection is positioned inwardly of the plane of the bottom surface of the dipper when the dipper is in a retracted position, pitched upwardly and restrained by the pitch limiting means. |
