Hydraulic system for controlling bulldozer blade

Claim 1

A hydraulic means for operating a bulldozer blade comprising, a vehicle, a bulldozer blade universally mounted on said vehicle for pivotal movement about a transverse axis to pitch said blade and for the pivotal movement generally about a longitudinal axis to tilt said blade, a pair of ram assemblies pivotally supported on said vehicle, each ram assembly including a strut and a pusharm universally connected to the lower and upper portion of said blade respectively, a hydraulic system including a source of pressurized fluid, a hydraulic actuator in each of said pusharms for extending or contracting said pusharms, a control valve connected between said source and each one of said actuators controlling the flow of pressurized fluid from said source to said hydraulic actuators, resilient means connected to each of said control valves normally biasing said valves to a centrally neutral position, a single control lever, means connecting said lever to both control valves to simultaneously control the flow of hydraulic fluid to each of said hydraulic actuators, pivotal support means supporting said lever for pivotal movement about two axes transverse to the length of the lever, said pivotal support means defining a first pivotal axis essentially parallel with said transverse axis whereby pivotal movement of said lever about said first axis provides simultaneous extension of said actuators to pitch said blade, said pivotal support means defining a second pivotal axis essentially parallel with said longitudinal axis whereby pivotal movement of said lever about said second axis differentially extend and contract said hydraulic actuators to tilt said blade and to thereby provide pivotal movement of said lever to simulate movement of said blade.