22-122-1TX / TXH / TXB 180S - 400L (Rev. 4/23/07)TX / TXH / TXB 180S - 400L (Rev. 4/23/07)
causes LC2 to open and LC3 to close enough tocauses LC2 to open and LC3 to close enough to
satisfy the steering flow requirement (Load sensesatisfy the steering flow requirement (Load sense
pressure can pressure can be measured be measured at port at port LSM). LSM). ExcessExcess
flow is available for use by the hoist and tilt.flow is available for use by the hoist and tilt.
When load sense (steering) pressure reaches theWhen load sense (steering) pressure reaches the
setting of relief valve [RV2 (which must be set at asetting of relief valve [RV2 (which must be set at a
pressure equal to or lower than RV1)], RV2 openspressure equal to or lower than RV1)], RV2 opens
causing LC3 to causing LC3 to open as well. open as well. Pump flow Pump flow is thenis then
sent to sent to hoist and tilthoist and tilt. . (Refer to (Refer to thethe HYDRAULICHYDRAULIC
PRESSURE SETTINGSPRESSURE SETTINGSin thein the AppendicesAppendicesforfor
RV1 and RV2 pressure settings.)RV1 and RV2 pressure settings.)
Hydraulic LogicHydraulic Logic (Illustration 22-20)(Illustration 22-20).. HydraulicHydraulic
flow from the secondary gear set of the mainflow from the secondary gear set of the main
pump enters at the inlet of the accessory valve.pump enters at the inlet of the accessory valve.
Flow then passes through the manifold where itFlow then passes through the manifold where it
joins with the flow from the joins with the flow from the primary pump. primary pump. TheThe
combined flows then enter the hoist and tilt valve.combined flows then enter the hoist and tilt valve.
Pump flow from the secondary gear set is alwaysPump flow from the secondary gear set is always
available for accessory functions such as sideavailable for accessory functions such as side
shifter and fork positioners if the truck is soshifter and fork positioners if the truck is so
equipped. equipped. Pump flow Pump flow from the from the primary pumpprimary pump
must satisfy steering requirements first, butmust satisfy steering requirements first, but
excess flow is always available for hoist and tiltexcess flow is always available for hoist and tilt
functions. functions. The total flow The total flow from both pumps from both pumps is avail-is avail-
able to hoist and tilt if there is no requirement fromable to hoist and tilt if there is no requirement from
steering or steering or accessory functaccessory functions. ions. Flow returns Flow returns toto
the tank from the tank from the hoist the hoist and tilt valve and tilt valve outlet. outlet. TheThe
outlet is outlet is equipped with equipped with two returns. two returns. An inlineAn inline
check valve has been installed at the hydrauliccheck valve has been installed at the hydraulic
ORF1 and check valve (CK1) to start the accumu-ORF1 and check valve (CK1) to start the accumu-
lator charging lator charging process. process. As pressure As pressure builds in builds in thethe
charge circuit, the pressure reducing valve (PRV1)charge circuit, the pressure reducing valve (PRV1)
supplies pilot fluid for accessory valve and hoist /supplies pilot fluid for accessory valve and hoist /
tilt valve tilt valve operation. operation. When the When the PRV1 valve PRV1 valve settingsetting
is reached, it closes off and all flow through theis reached, it closes off and all flow through the
circuit is directed to the parking brake and servicecircuit is directed to the parking brake and service
brake acbrake accumulators. cumulators. When When both both accumulatorsaccumulators
reach full pressure, determined by the unloaderreach full pressure, determined by the unloader
valve (UNL1), the pilot to the spring chamber ofvalve (UNL1), the pilot to the spring chamber of
logic element (LC1) is drained and pump flow islogic element (LC1) is drained and pump flow is
directed to the drive axle to cool the left side drivedirected to the drive axle to cool the left side drive
axle brake. axle brake. Flow from Flow from the other gear the other gear set cools set cools thethe
fluid of tfluid of the right side he right side drive axle brakdrive axle brake. e. As pres-As pres-
sure falls in the accumulators, the pressure signalsure falls in the accumulators, the pressure signal
to UNL1 falls to UNL1 falls and closes itand closes it. . The process The process repeatsrepeats
itself. itself. Relief valve Relief valve (RV3) protects (RV3) protects the pump fromthe pump from
over-pressurization and acts as a thermal reliefover-pressurization and acts as a thermal relief
also. also. The parking The parking brake is brake is electrically applied electrically applied andand
released by released by solenoid SOL1. solenoid SOL1. Pressure must Pressure must bebe
held on the spring-applied / hydraulic-releasedheld on the spring-applied / hydraulic-released
parking brake (located on the transmission out-parking brake (located on the transmission out-
put). put). Both brake Both brake pedals are spedals are supplied from presupplied from pres--
sure and flow sure and flow stored in accstored in accumulator (ACC2). umulator (ACC2). TheThe
LH foot pedal inches the transmission and appliesLH foot pedal inches the transmission and applies
the wheel the wheel brakes. brakes. The RH The RH foot pedal foot pedal applies theapplies the
wheel brakes onlywheel brakes only. . (Refer to (Refer to thethe HYDRAULICHYDRAULIC
PRESSURE SETTINGSPRESSURE SETTINGSin thein the AppendicesAppendicesforfor
pressure settings.)pressure settings.)
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