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Groundsmaster 4000--D Hydraulic SystemPage 4 -- 23
Steering Circuit
A four section gear pump is coupled to the piston (trac-
tion) pump. The third gear pump section supplies hy-
draulicflowtothe steering controlvalveand the lift/lower
controlvalve.Pump hydraulicflowis delivered to thetwo
circuits through a proportional flow divider located in the
fan drive manifold. The gearpumptakes its suction from
the hydraulic reservoir. Steering circuit pressure is limit-
ed to 1350 PSI (93 bar) by a relief valve located in the
steering control.
With the steering wheel in the neutral position and the
engine running, flow enters the steering control valve at
the P port and goes through the steering control spool
valve, by--passing the rotary meter (V1) and steering
cylinder. Flow leaves the c ontrol valve through the PB
port to the oil filter and traction charge circuit.
Left Turn
When a left turn is made with the engine running, the
turningofthe steeringwheelpositionsthe spool valveso
thatflowgoesthrough the topofthe spool. Flowentering
the steering control valve at the P port goes through the
spool and is routed to two places. First, most of the flow
through the valve is by--passed out the PB port back to
the oil filter and traction charge circuit. Second, the r e-
mainder of the flow is drawn through the rotary meter
(V1) and out the L port. Pressure contracts the steering
cylinder piston for a left turn. The rotary meter ensures
that the o il flow to the cylinder is proportional to the
amount of the turning on the steering wheel. Fluid leav-
ing the cylinder flows back through the s pool valve then
through the T port and to the hydraulic reservoir.
The steering control valve returns to the neutral position
when turning is completed.
Right Turn
When a right turn is made with the engine running, the
turningofthe steeringwheelpositionsthe spool valveso
that flow goes through the bottom of the spool. Flow en-
tering the steering control valve at the P port goes
through the spool and is routed to two places. As in a left
turn, most of the flow through the valveis by--passed out
the PB port back to the oil filter and traction charge cir-
cuit. Also like a left turn, the remainder of the flow is
drawn through rotary meter (V1) but goes out port R.
Pressure extends the steering cylinder piston for a right
turn. The rotary meterensures that the oil flow to the cyl-
inder is proportional to the amount of the turning on the
steering wheel. Fluid leaving the cylinder flows back
through the spool valve then through the T port and to
the hydraulic reservoir.
The steering control valve returns to the neutral position
when turning is completed.
Figure 13
1350
PSI
PB
STEERING
T
R
P
L
PISTONMOVEMENT
CONTROL
1350
PSI
PB
STEERINGCYLINDER
STEERING
T
R
P
L
PISTONMOVEMENT
CONTROL
1350
PSI
PB
STEERINGCYLINDER
STEERING
T
R
P
L
CONTROL
LEFT TURN
NEUTRAL POSITION
RIGHT TURN
NOPISTONMOVEMENT
STEERINGCYLINDER
Hydraulic
System