Jacobsen AR3, Technical/Repair Manual

Page: 207 / 342

6-16 4181384 First Edition
HYDRAULICS
6
Theory of Operation and
Diagnostic Information
Steering Circuit and Theory of
Operation
See Figure 6-11.
Hydraulic oil is drawn from the hydraulic oil tank by the
steering pump. Operating pressure oil flows from the
steering pump to the steering valve where there is a relief
valve set to reach a maximum pressure of 1595 psi (110
bar).
When the steering wheel is turned, oil is directed from
steering valve to one side of the steering cylinder, moving
the piston and rear wheel support and turning the rear
wheel.
Low-pressure (return) oil from the other side of the
steering cylinder flows through the steering direction
valve body and returns to the hydraulic oil tank.
When the steering cylinder reaches the end of its travel,
or if the steering mechanism movement is stopped with
the steering wheel turned, pressure in the steering circuit
will build. When pressure reaches maximum pressure the
steering relief valve opens and releases excess oil flow to
the hydraulic oil tank.
A portion of the operating pressure oil flowing through the
steering direction valve body is directed to the lift valve to
supply oil for the raise/lower circuit. (See “Raise Circuit
Schematic and Theory of Operation” on page 6-18.) The
amount of oil routed to the raise/lower circuit will depend
on the position of the steering wheel/steering direction
valve, as the steering system has priority. The most oil
will flow to the raise/lower circuit when the steering wheel
is in the center (neutral) position.