THEORY OF OPERATION - CONTINUED
HYDRAULIC STEERING SYSTEM
General. The hydraulic steering system has two functions. The primary purpose is for steering the roller. The steering
pump receives oil from the hydraulic oil tank after it has been cleaned by a hydraulic filter. Oil from the steering pump
flows through a priority valve and continues on in two directions. The primary path for the oil is to the steering control
unit. The steering control unit sends hydraulic oil to the steering cylinders. When the steering wheel is turned, the steer-
ing control unit sends hydraulic oil through the steering hydraulic lines to force the steering cylinders to turn the roller.
The secondary flow of oil and return oil from the steering control unit is combined with the parking brake and two-speed
shift manifold by way of an oil line. This oil is used for the charge system. The charge system supplies the control circuit
and replenishes the main closed loop and cooling circuit of the vibratory system.
Steering Control Unit. The steering control unit is a spring-centered, non-load, reaction-type pump which sends pres-
surized hydraulic oil to the steering cylinders. The steering control unit has two sections: the control section and the
metering section. Oil from the steering pump goes into the control section. As the steering wheel is turned, the control
sends oil out from the metering section. Metered oil from the metering section is directed by the control section to either
the left turn port or right turn port.
Steering Pump. The steering pump is a gear-type pump mounted to the accessory drive on the engine and turns clock-
wise as the engine is running. The steering pump supplies pressurized hydraulic oil to the steering system and charge oil
to the propel and vibratory systems. A priority valve gives the steering system priority over the propel charge circuits. A
pressure compensator valve regulates a constant 6 gallons per minute flow to the steering system.
Priority Valve. Inside the steering pump is the priority valve which is a pressure compensated flow divider. The priority
valve divides flow between the steering circuit and the propel charge circuits. The steering circuit has priority.
Brake/Shift Manifold Valve. The brake/shift manifold valve is part of the propel system, yet receives its charge from
the steering pump.
Steering Cylinders. The steering cylinders are piston-type hydraulic cylinders mounted at the pivot joint of the frame
and yoke assemblies. When the steering control unit sends pressurized oil to them, the steering cylinders force the yoke
assembly to shift its relative placement on the frame assembly, causing the roller to steer either left or right.
Fuel/Hydraulic Oil Tank. The fuel/hydraulic oil tank consists of the hydraulic tank (located on the left side) and the
fuel tank (located on the right side). Although the tanks are welded together, they are separate in their function. The
CB534B Roller hydraulic oil tank holds 15.5 gal. (59 l) of hydraulic oil. The CB534C Roller hydraulic oil tank holds 24
gal. (91 l) of hydraulic oil.
Hydraulic Oil Filter. The hydraulic oil filter cleans all hydraulic oil used in the propel, vibratory and steering systems.
When the filter element is clogged, or oil is cold, the bypass valve opens and oil flows past the element and a signal is
sent to the warning light. On the CB534B Roller, an indicator is mounted on the filter assembly to display the condition
of the filter element.