Toro 07390 Workman HDX-Auto, Руководство по обслуживанию, Страница: 196 / 280

Workman HDX Auto Page 7 − 12 Hydraulic System
Raise and Lower Bed
The hydraulic gear pump supplies flow for the steering
circuit and for raising and lowering the bed. Pump output
flows through the steering control valve and then to the
lift valve for raising and lowering the bed (flow priority to
the steering circuit). Circuit pressure is limited by a relief
valve located in the steering control valve.
NOTE: On vehicles with High Flow Hydraulics, a two (2)
section gear pump is used. The front gear pump section
on these vehicles supplies oil for steering and raising/
lowering the bed. The rear pump section on these vehi-
cles provides system flow for accessories.
When the lift valve is in the center position, flow from the
gear pump by−passes the lift valve and returns through
the hydraulic oil filter and to the reservoir.
Raise Bed (Fig. 10)
When the bed is to be raised (lift lever pulled rearward),
the lift valve spool directs flow out the A port of the lift
valve to the barrel end of the lift cylinders. Hydraulic
pressure against the cylinder pistons extends the cylin-
der shafts. At the same time, the lift valve spool cam pin
opens the return direction check ball which allows the
cylinder pistons to push the hydraulic fluid out the rod
end of the lift cylinders. Fluid leaving the cylinders is rout-
ed through the lift valve to the reservoir.
When the control valve lever is released, spring action
returns the lift valve spool to the center position and lift
cylinder movement is stopped. The cylinder position is
locked in place since there is no complete circuit of flow
to and from the lift cylinders.
Lower Bed (Fig. 10)
Circuit operation for lowering the bed (lift lever pushed
forward) is similar to raising the bed. However, the lift
valve spool directs flow from the B port of the lift valve to
the rod end of the lift cylinders. Hydraulic pressure
against the cylinder pistons retracts the cylinder shafts
to lower the bed.
Figure 10
LIFT CYLINDERS (2)
PISTON MOVEMENT
LOWER BED
LIFT CYLINDERS (2)
PISTON MOVEMENT
RAISE BED
LIFT VALVE
(IN LOWER POSITION)
LIFT VALVE
(IN RAISE POSITION)
B A
B
A