QUIK-LIFT® UNIT COMPONENTS CONT.
CHECK VALVES
Check valves are very simple devices that have two
basic functions: They prevent fluid from passing
through them in one direction, but they allow fluid to
pass through them in the opposite direction.
In both models a pump check valve is used to prevent
hydraulic fluid from leaking back through the pump
to the reservoir.
The E-60 and E-60H models incorporate two additional
check valves, necessary because the “B” and “C”
Solenoid Valves, being spool valves, have some
leakage.
One check valve is located between the “B” Solenoid
Valve and the lift cylinder. It prevents the hydraulic fluid
in the lift cylinder from leaking back through the “B”
Solenoid Valve which could cause the weight of the
plow to angle the plow to the left by forcing hydraulic
fluid through the “C” Solenoid Valve into the right
power angling cylinder.
The other check valve is located between the “B” and
“C” Solenoid Valves. It prevents the hydraulic fluid
in either power angling cylinder from being forced
through the “B” Solenoid Valve to the left cylinder.
PILOT CHECK VALVE
The pilot check valve used only on the E-60 and
E-60H is more sophisticated in that it incorporates
a piston in addition to the ball, seat and spring. It is
located between the “C” Solenoid Valve and reservoir.
It has two functions: The first is to prevent the hydraulic
fluid in either power angling cylinder from leaking back
to the reservoir. The second is to allow the hydraulic
fluid from the retracting power angling cylinder during
the angling cycle to return to the reservoir. This is
accomplished by the pressurized hydraulic fluid
moving the piston which forces the check ball off its
seat.
CROSSOVER RELIEF VALVE
When plowing snow, a snow plow can be exposed
to damaging forces caused by impact with hidden
obstructions, ends of curbs, etc. With power angling,
these damaging forces can damage not only the snow
plow but also the vehicle. The crossover relief valve
has the function of protecting the snow plow system
against these damaging forces under normal snow
plowing conditions. The crossover relief valve, cannot
protect the system from damaging forces that are too
great due to abusive snow plowing conditions.
Basically, the crossover relief valve functions exactly
like the previously described pump relief valve.
It’s designed to open at a specific pressure. In this
instance, the pressure is not produced by the pump
but rather by the damaging force. As an example,
assume that the right corner of the plow runs into the
end of a curb. The impact will attempt to collapse the
right power angling cylinder. As a result, very high
hydraulic pressure is produced within the cylinder.
When the produced pressure is high enough, it
opens the crossover relief valve, allowing the highly
pressurized hydraulic fluid to flow directly to the left
power angling cylinder.
When the crossover relief valve functions in this
manner, the excessive pressure is released, the
excessive energy produced by the impact is absorbed,
and the result is only a change in angled position of
the plow.
The crossover relief valve may be adjusted to the
specified pressure of 3800 P.S.I. ± 400 by turning the
3/8” hex cap screw after installing a suitable pressure
gauge of 5000 P.S.I. in the circuit. TIGHTEN (TURN IN)
ADJUSTMENT SCREW TO INCREASE PRESSURE.
See Disassembly Figure 3-49 thru 3-56. Reassembly
figures 3-57 thru 3-69.
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