Patent ID: 7793742

Claim:
A ground engaged vehicle comprising: a wheeled front portion; a wheeled rear portion; a hydrostatic drive system driving at least one of said wheeled front and rear portions; an articulation between said wheeled front portion and said wheeled rear portion, said articulation allowing said wheeled front portion and said wheeled rear portion to roll relative to one another around a longitudinal axis of the vehicle, wherein said articulation is comprised of a first collar attached to said front wheeled portion and a second collar attached to said wheeled rear portion and a center tube operatively engaged with each of said collars; and wherein said center tube has a sufficiently large diameter for at least one hydrostatic drive hose to travel between said wheeled front portion and said wheeled rear portion; two wheels on said front portion are connected to each other by a front tie rod, said front tie rod having a first end and a second end, each of said first and said second ends of said front tie rod being pivotably attached to a front lever arm, each of said lever arms being operatively engaged to turn each of said two wheels of said front portion, said front tie rod being driven by a front two way piston and cylinder assembly; two wheels on said rear portion are connected to each other by a rear tie rod, said rear tie rod having a first end and a second end, each of said first and said second ends of said rear tie rod being pivotably attached to a rear lever arm, each of said lever arms being operatively engaged to turn each of said two wheels of said rear portion, said rear tie rod being driven by a rear two way piston and cylinder assembly; each of said front and rear two way cylinder and piston assemblies having an active chamber, one of said active chambers receiving pressurized fluid from said power steering system while the other of said front or rear active portions exhausts fluid to return to said power steering system; each of said front and rear piston and cylinder assemblies having a passive portion each of said front and rear passive portions being connected by a hydrostatic hose, and said first and second passive portions and said hose being in operative communication to trap a volume of fluid such that pressurization of a first active portion of a first piston cylinder assembly drives said trapped fluid volume into said second passive portion of said second piston cylinder assembly such that when a first piston cylinder assembly is driven to turn a first pair of wheels in a first direction, said second piston cylinder assembly is driven to drive a second pair of wheels in an opposite direction.