Toro 04384 Service Manual page 51

Right and Left Turn
The tandem gear pump is directly coupled to the piston
(traction) pump. The rear gear pump section supplies
hydraulic flow for the steering circuit (priority flow), for
raising and lowering the cutting units and for the traction
charge circuit. The gear pump takes its suction from the
hydraulic reservoir. Maximum circuit pressure of 1160
PSI (80 bar) is limited by the relief valve located in the
steering valve.
With the steering wheel in the neutral position and the
engine running, the spool valve in the steering valve is
in the center position. Pump flow enters the steering
valve at Port (P) and goes through the spool valve, by--
passing the steering cylinder. Flow leaves the steering
valve out port (E) to be available for the raise/lower and
traction charge circuits.
Right Turn
When a right turn is made with the engine running, the
turning of the steering wheel positions the spool valve in
the steering valve so that flow goes through the bottom
of the spool. Flow entering the steering valve at Port (P)
goes through the spool and is routed to two places. First,
most of the flow through the valve is by--passed out
steering valve port (E) and is available for raising and
lowering the cutting units and for the traction charge cir-
cuit. Second, the remainder of the flow is drawn through
the steering valve rotary meter and out steering valve
port (R). Pressure moves the steering cylinder piston to
retract the cylinder for a right turn. The rotary meter en-
sures that the oil flow to the cylinder is proportional to the
amount of turning on the steering wheel. Fluid leaving
the cylinder flows back through the spool valve then out
steering valve port (T) and then to the traction charge
circuit.
The steering valve returns to the neutral position when
turning is complete.
Greensmaster 3250--D
Left Turn
When a left turn is made with the engine running, the
turning of the steering wheel positions the spool valve in
the steering valve so that flow goes through the top of
the spool. Flow entering the steering valve at Port (P)
goes through the spool and is routed to two places. First,
most of the flow through the valve is by--passed out
steering valve port (E) and is available for raising and
lowering the cutting units and for the traction charge cir-
cuit. Second, the remainder of the flow is drawn through
the steering valve rotary meter and out steering valve
port (L). Pressure moves the steering cylinder piston to
extend the cylinder for a left turn. The rotary meter en-
sures that the oil flow to the cylinder is proportional to the
amount of turning on the steering wheel. Fluid leaving
the cylinder flows back through the spool valve then out
steering valve port (T) and then to the traction charge
circuit.
The steering valve returns to the neutral position when
turning is complete.
Page 4 - - 19 Hydraulic System