Abstract: A closed rigid tank stores oil or other liquid for use in operating hydraulic jacks or other fluid-driven devices. A flexible bladder within the tank is coupled to a source of compressed air and to an air pressure regulator in order to maintain a constant positive pressure in the tank as the bladder expands and contracts in response to the withdrawal and return of oil. The sealed regulated pressure tank may be smaller, lighter and less costly than the tank structures heretofore used in hydraulic systems and the construction is more adaptable to variations in tank shape and location relative to other system components. Fluid lines which connect the tank and fluid pump may be smaller and the total volume of oil required for the hydraulic system may be reduced.

Abstract: A vehicle such as a motor grader includes a hydrostatic auxiliary front wheel drive system which utilizes implement system pressurized fluid flow to drive a pair of fixed displacement hydraulic motors, such motors being drivingly connected to cause rotation of the front wheels. A pilot operated series-parallel valve in combination with a flow divider allows the motors to be driven in series or in parallel. A directional control valve is selectively responsive to operator control, and clutch actuation is accomplished automatically by directing a controlled portion of system fluid to such clutches to overcome the normal spring bias thereof.