Torque balancing linkage for excavator dipper sticks

Claim 1

In an earth moving machine having a boom with spaced side members at its outer end, said side members having spaced upstanding outer end projections, a saddle pivotally connected between said spaced upstanding projections of the side members of the boom to normally project thereabove, a dipper stick slideably adjustably carried in said saddle, a fluid pressure operated cylinder pivotally connected at its inner end to the boom to extend generally longitudinally thereof and having an extensible piston rod projecting outwardly toward the outer end of the boom, the improvement comprising power-transmitting linkage pivotally connected at one end to the piston rod and at its other end to the saddle at a location above the piston rod and spaced longitudinally outwardly from the pivotal connection between the saddle and the upstanding projections of the boom, radius linkage pivotally connected at its upper end to the upstanding projections of the boom inwardly of the pivotal connection between the saddle and said projections and having its lower end connected to the piston rod adjacent the pivotal connection between the piston rod and said power-transmitting linkage, both the power-transmitting linkage and the piston rod extending in the same general direction as the longitudinal axis of the boom when the dipper stick is in an inwardly crowded position, and the power-transmitting linkage being movable upwardly at a progressively increasing angle with respect to the axis of the boom as the dipper stick is raised whereby the effective lifting force from the piston rod is augmented as the demand for power increases during elevation of the dipper stick and saddle to a position of parallelism with the boom, wherein, when the piston rod is fully extended, the length and position of the radius linkage is such as to maintain the cylinder and its piston rod substantially within the confines of the side members of the boom while the dipper stick is substantially parallel with the boom, and wherein the length and position of the radius linkage is such as to maintain the arc of swinging movement of the pivotal connection between the end of the piston rod and the linkage such that said pivotal connection stays substantially within the confines of the side members of the boom in all positions of movement.