Hydraulic tilt and pitch control for dozer blade

Claim 1

In a fluid control system for an earth moving blade pivotally supported on a vehicle for selectively varying the pitch and tilt position of said blade relative to a ground surface, said blade being pivoted around intersecting axes and said vehicle having a control console, the improvement comprising: first and second fluid cylinders, each having a piston and piston rod and each having one end connected to opposite upper ends of said blade and the other end to said vehicle; a main control valve means connected to a source of fluid under pressure and having first and second sections separate from each other; a selector valve movable by selector valve control means between a pitch control and a tilt control position; first and second conduits interconnecting the rear and front ends, respectively, of said first cylinder with said selector valve, and third and fourth conduits interconnecting the rear and front ends, respectively, of said second cylinder with said selector valve; first and second pairs of conduits interconnecting said first and second sections, respectively, of said main control valve means with said selector valve, each of said pairs including a supply and an exhaust conduit, and said main control valve having reversing means for simultaneously reversing the supplyexhaust functions of said conduits within each conduit pair; said selector valve, in its tilt position, providing communication between said second and fourth conduits, between said first conduit and the exhaust conduit of said second pair of conduits, and between the supply conduit of said second pair of conduits and said third conduit, all when said main control valve is in a first position, to tilt the blade in a first direction, and the reversing of the supply-exhaust functions of said second pair of conduits by said main control valve reversing means causing the blade to tilt in the opposite direction; said selector valve, in its pitch position, providing communication between said first and third conduits and the respective supply conduits of said first and second Pair of conduits, and further providing communication between said second and fourth conduits and the respective exhaust conduits of said first and second pair of conduits, all when said main control valve is in a first position, to pitch the blade in a first direction, and the reversing of the supply-exhaust functions of said first and second pairs of conduits by said main control valve reversing means causing the blade to pitch in the opposite direction.