Pitch-tilt hydraulic circuits for dozer blades

Claim 1

In a vehicle having a pivotally mounted dozer blade, said blade pivotally supported on said vehicle by a pair of double acting fluid pressure cylinders, each cylinder having a piston and a rod, said cylinder being connected to said blade on opposite sides of the vertical pivot axis and vertically spaced from the horizontal pivot axis, the improved fluid control circuit for controlling tilt and pitch of the blade which comprises: a source of fluid pressure; an exhaust conduit; a diverter valve for selecting the tilt and pitch functions; a control valve for selecting the direction of tilt and pitch; said control valve being connected in series between a first port of said diverter valve and both said source of fluid pressure and said exhaust conduit, said control valve also being selectively connected to a first end of one of said fluid cylinders at said first port when said diverter valve is in its tilt position; said control valve being further connected in series between the corresponding end of the other of said fluid cylinders and both said source of fluid pressure and said exhaust conduit; said first ends of both said fluid cylinders being slectively connected to each other and to said control valve at a second port of said diverter valve when said diverter valve is in its pitch position; the opposite ends of both said fluid cylinders being continuously connected to each other by a linking conduit, which is in turn selectively connected to said control valve at said first port of said diverter valve when said diverter valve is in its pitch position; said control valve, when in a first non-neutral position, connecting one of said diverter valve ports to said source of fluid pressure and the other of said diverter valve port to said exhaust conduit and reversing said connection when in a second non-neutral position; whereby both tilt and pitch functions are controlled with two fluid cylinders and two valves, with the exhausting end of one fluid cylinder supplying pressurizing fluid to the corresponding end of the other fluid cylinder via said linking conduit when said diverter valve is in its tilt position, and with a first pair of corresponding ends of said fluid cylinders being simultaneously pressurized and a second pair of corresponding ends of said fluid cylinders being simultaneously exhausted, as controlled by said control valve, when said diverter valve is in its pitch position.