1.21.2. Hopper Wing Lift System. The hopper wing
lift system consists of switches on the operator switch
panel, right auxiliary hydraulic pump, 50/50 flow divider,
solenoid valves, and hydraulic cylinders.
Power for the hopper wing lift system originates at CB5.
The operator switch panel has switches for both left and
right hopper wing lift cylinder control. Power through the
spring loaded center OFF switch is directed to the extend
or retract solenoid valve and to the power beyond
Hydraulic oil for the hopper wing lift system is supplied
from the right auxiliary hydraulic pump. The right
auxiliary hydraulic pump contains two pumps, 0.7 and
0.58 cu in. (11,5 and 9,5 cc) outputs, mounted on a
common shaft. The 0.58 cu in. (9,5 cc) output pump
supplies oil to a 50/50 flow divider. The flow divider splits
the hydraulic flow, sending half to the stack valve.
Stack valve pressure is regulated at 2500 psi (17 238
kPa) by a pressure relief valve internal to the stack valve.
This pressure can be read at the test manifold. The
relief valve ports excess hydraulic oil to the return
manifold and back to the hydraulic reservoir. The oil that
is not routed through the relief valve is routed to the
power beyond valve and the screed lift valve. In the
normal, deenergized, position the power beyond valve
routes all hydraulic oil out of the stack valve and to the
energizes whenever any hydraulic function on the stack
valve is operated. When the power beyond valve
solenoid is energized the valve shifts and does not allow
any oil to leave the stack valve by way of the track
tensioning system. All hydraulic oil entering the stack
valve is therefore directed to the screed lift valve. This
The screed lift valve is normally deenergized, allowing all
hydraulic fluid to flow to the stack valve supply header.
When the screed lift system is in use, the screed lift
valve is energized, redirecting all hydraulic flow from the
stack valve to the screed lift system. Since this prevents
any hydraulic oil from entering the stack valve supply
header, no stack valve functions will operate until the
screed lift valve is deenergized. Once hydraulic oil is
past the screed lift valve, the fluid enters the stack valve
When the hopper wing control switch on the operator
control console is activated, the extend solenoid or the
retract solenoid will energize, repositioning the valve.
The valve will allow the hydraulic oil from the stack valve
supply header to move the cylinder in the selected
direction. The hydraulic oil forced out of the cylinder is
directed to the stack valve return header. The stack
valve return header directs the hydraulic oil to the return
manifold and then to the hydraulic reservoir.