03-303 ORBITROL

No. 3-303October, 1998Char-Lynn®

Steering Controls

Description of Operation

Technical Info.

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Char-Lynn Steering Controls

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Eaton Char-Lynn Steering Controls

Manual Steering

The following information may be used to explain andunderstand the basic steering concepts.

The first concept in steering is Manual Steering, or as sometimes referred to as arm strong type steering.The stronger the arm the stronger the steering. With this type ofsteering there usually is some form of a mechanicaladvantage such as the diameter of the steering wheel oradditional mechanical reduction which is found in the steeringsector. The advanage with this type of steering is a directmachanical linkage between the steering wheel and the steeredwheels.

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Power Assist

The second concept in steering is power assist.Steering with power assist usually uses some form ofhydraulics to assist in the steering function. When a steeringcommand is made, a hydraulic valve is opened, allowing thehydraulics to assist in the steering fuction. Again, the advanageof this type of steering, like the manual type steering, is themechanical linkage between the steering wheel and the steeredwheels.

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Hydrostatic Steering

The third concept in steering is Hydrostatic Steering.This is the type of steering that is manufactured at EatonCorporation Hydraulics Division.Hydrostatic Steering is truely 100% Hydraulic and has nomechanical linkage between the steering wheel and steeredwheels. Because there is no machanical linkage used with thistype of steering, hydrostatic steering is very easy to apply and isused on many applications today. Hydrostatic Steering is usuallyused on off-road applications

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The following information may be used to explain and understandbasic Eaton Char-Lynn steering control operation.

This illustration is used to show the internal porting andcomponents that are found in a typical Eaton steering control unit.When rotated, the spool/sleeve assembly is like a rotary valve andis used to control fluid direction. The gerotor assembly is basicallya metering section, and is used to control fluid flow.

T L R P

Pump InRightLeftPump Return( Tank )

Pin

Spool

Sleeve

CenteringSprings

CheckValve

Drive

GerotorAssembly

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This illustration is used to show a open center type steeringcontrol in the neutral position.In the neutral position, the fluid enters into the steering controlthrough the (P) port and continues through the spool/sleeveassembly and back out the (T) port.

T L R P

Pump Pressure

Metered Flow

Exhaust

Intake

Intake or Exhaust

Inactive or Trapped

Neutral

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This illustration is used to show the steering control in the lefthand turn position.In this position, the fluid enters into the steering controlthrough the (P) port and continues through the spool/sleeveassembly, metering section, spool/sleeve assembly and outthe (L) port. The (R) port is open through the spool/sleeveassembly to the (T) port.

T L R P

Pump Pressure

Metered Flow

Exhaust

Intake

Intake or Exhaust

Inactive or Trapped

Left Turn

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This illustration is used to show the steering control in the righthand turn position.In this position, the fluid enters into the steering control throughthe (P) port and continues through the spool/sleeve assembly,metering section, spool/sleeve assembly and out the (R) port.The (L) port is open through the spool/sleeve assembly to the(T) port.

T L R P

Pump Pressure

Metered Flow

Exhaust

Intake

Intake or Exhaust

Inactive or Trapped

Right Turn

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This illustration is used to show the steering control in themanual right hand turn position.In this position, the fluid is recirculated from the (T) portthrough the check valve, spool/sleeve assembly, meteringsection, spool/sleeve assembly and out the (R) port. The (L)port is open through the spool/sleeve assembly to the (T)port. In this position, the metering assembly actually be-comes a hand pump.

T L R P

Pump Pressure

Metered Flow

Exhaust

Intake

Intake or Exhaust

Inactive or Trapped

Manual

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The second section may be used to explainand understand steering circuits.

This illustration is used to show a open center type steeringcontrol in the neutral position.In the neutral position, the fluid enters into the steering controlinto the (P) port, through the spool/sleeve assembly and rightback out the (T) port.

Open Center( Neutral Position )

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This illustration is used to show the steering control in the lefthand turn position.In this position, the fluid enters the steering control into the(P) port, through the spool/sleeve assembly, metering sec-tion, spool/sleeve assembly and out the (L) port to the steer-ingcylinders. The fluid in the opposite end of the steering cylin-ders is ported back to the (R) port, which is now open backthrough the spool/sleeve assembly, allowing the fluid to exitout the (T) port.

Open Center( Lefthand Turn Position )

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This illustration is used to show a closed center steering controlin the neutral position.In this position, the fluid enters into the steering control throughthe (P) port and is blocked at the spool/sleeve assembly.

Closed Center( Neutral Position )

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This illustration is used to show the steering control in the lefthand turn position.In this position, the fluid enters the steering control into the(P) port, through the spool/sleeve assembly, metering sec-tion, spool/sleeve assembly and out the (L) port to the steer-ingcylinders. The fluid in the opposite end of the steering cylin-ders is ported back to the (R) port, which is now open backthrough the spool/sleeve assembly, allowing the fluid to exitout the (T) port.

Closed Center( Lefthand Turn Position )

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This illustration is used to show a load sensing type steeringcontrol in the neutral position.In this position, the fluid enters into the steering control throughthe (P) port and is blocked at the spool/sleeve assembly. In theneutral position, there will be no load sensing pressure.Load sensing steering controls are used to provide a signal toload sensing pumps and or priority valves.

Load Sensing( Neutral Position )

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This illustration is used to show a load sensing type steeringcontrol in the left hand turn position.In this position, the fluid enters the steering control into the(P) port, through the spool/sleeve assembly, metering sec-tion, spool/sleeve assembly and out the (L) port to the steer-ingcylinders. The fluid in the opposite end of the steering cylin-ders is ported back to the (R) port, which is now open backthrough the spool/sleeve assembly, allowing the fluid to exitout the (T) port. In this position, the load sensing port is opento provide a signal to a load sensing pump and or a priorityvalve.This pressure signal will be just the pressure required tomake the steering function.

Load Sensing( Lefthand Turn Position )

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This illustration is used to show a non-load reaction steeringcontrol. When in a steering position, hydraulic pressure to the steeringcylinders exceeds the mechanical external forces reacting againstthe steered wheels. This hydraulic pressure to the steeringcylinders will cause them to either extend or retract.Non-load reaction steering controls, when returned to the neutralposition, block both cylinder ports (L) and (R) at the spool/sleeveassembly. With these ports in the blocked position, the hydraulicfluid will be entrapped between the steering cylinders and thesteering control causing the steered wheels to remain in the laststeered position.

Non-Load Reaction( Control In Neutral Position )

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This illustration is used to show a load reaction steering con-trol.Like the previous illustration, when in a steering position, theload reaction steering control will function just like non-loadreaction steering control.Load reaction steering controls however, when returned to theneutral, will have both cylinder ports in a open position directlythrough the spool/sleeve assembly to the gerotor assembly ormetering section. The external forces reacting against thesteered wheels now cause the hydraulic pressure entrappedbetween the steering cylinders and the gerotor assembly to actas a motor.The gerotor assembly, now acting as a motor, will cause thesteering control and steered wheels to return the centeredposition.

Load Sensing( Lefthand Turn Position )

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This illustration is used to show the Q-Amp steering control.Q- Amp steering controls, when rotated more then 10 RPM, willbypass approximately 1-1/2 to 2 times the steering controls meteringsections displacement. Q-Amp steering controls, when in the Q-Ampmode, will give you a faster steering rate with a smaller steering pack-age.When ever the steering control is rotated slower then 10 RPM, thesteering control will return to the steering rate dictated by themetering section.

Q-Amp SteeringIncreases Steering

Flow 1-1/2 to 2 TimesMetering Displacement

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This illustration is used to show priority valve options.Priority valves are some times used in steering systems to provide,on demand, a metered priority flow to a single function when acommon pump supply is utilized for muli functions in the system.The VLC Series Priority Valves are 16 GPM flow rated. The controlspools are available with either a static or dynamic signal. Optionalstandby control pressures for static spools are 50, 75 and 100 PSI.Dynamic spools are 75, 110 and 145 PSI. The controlled flow sys-tem pressure options are 1200 to 3475 PSI, usually set in 25 PSIincrements.Eaton also has the VLE Series Priority Valves rated at 40 GPM andthe VLH Series rated at 63 GPM.

VLC Priority Valve

Controlled Flow Relief Valve

Stand -byControl PressureSpring

Static or DynamicSignal Spools

( Options )Inlet

Controlled FlowExcess Flow

Load Sensing

Tank

The Third section may be used to explainand understand Priority valve operation.

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This illustration is used to show a VLC priority valve with a static con-trol spool in the stand-by position.In the stand-by position there will be no load sensing pressure. Theinlet pressure first passes through a small orifice, forcing the controlspool to shift to the left, compressing the stand-by spring.With the control spool shifted to this position, the majority of pumpflow will exit out the excess flow port. The standby spring pressure willkeep the control spool shifted to the right, just enough to maintainstandby pressure, to the controlled flow port. This standby pressureagain is goveroned by the VLC proirity valves optional spring rate.

Spool shown in the stand-by position Inlet


Load Sensing

TankOrifice

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This illustration is used to show a VLC priority valve, again with astatic control spool, only this time in the priority flow mode.In the priority flow mode, the load sensing pressure is added to thestandby spring pressure. With this added pressure, the control spoolwill shift further to the right to provide both pump flow and pressureout the controlled flow port. The balance of the pump flow is portedout the excess flow port.Whenever the controlled flow pressure exceeds the controlled flowpressure relief valve, the valve will open to reduce the load sensingpressure on the left side of the control spool. With this load sensingpressure reduced, the inlet or pump pressure will shift the controlspool back to the left, reducing both pump flow and pressure to thecontrolled port. It will reduce it to the point of maintaining the presetpressure of the controlled flow relief valve.

Spool shown in the Priority Flow ModeInlet


Load Sensing

Tank

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This illustration is used to show a typical open center steering systemusing a fixed displacement pump.This open center steering system incorporates a open center steeringcontrol, check valve, main relief valve, fixed displacement pump, engine,reservoir and return line filter. The check valve, located between the pumpand the steering control, is used to prevent steering control kickback.Kickback may occur when the steering pressure becomes higher thenthe pump pressure.The main relief valve is used as overload protection for the steering control.The return line filter is used to keep the steering system clean.In the neutral position, the fluid provided by the pump passes through thecheck valve and enters into the (P) port located in the steering control.This same fluid then passes through the steering controls spool/sleeveassembly, out the (T) port, through the return line filter, back to reservoir.

The Forth section may be used to explainand understand steering systems.

T

L R

P

Reservoir

EngineFixedPump

Main Relief Valve

Filter

Open Center Steering System( Neutral Position )

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This illustration is used to show the same open center steering systemin the left turn position.In the left turn position, the fluid provided by the pump passes through thecheck valve and enters into the (P) port located in the steering control.This same fluid then passes through the steering controls spool/sleeveassembly, metering section and out the (L) port to the hydraulic cylindersfor a left turn. The fluid located in the opposite end of the hydraulic cylinders is forced out and into the (R) port located in the steering con-trol.This same fluid then passes through the steering controls spool/sleeveassembly, out the (T) port, through the return line filter, back to reservoir.As long as the pressure required to turn, is less then the main relief valvesetting, the main relief valve will remained closed. If this pressure ex-ceedsthe main relief valve setting, the valve will open to bypass the pump flowthrough the relief valve back to the reservoir.

T

L R

P

Reservoir

EngineFixedPump

Filter

Open Center Steering System( Left Turn Position )

Main Relief Valve

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This illustration is used to show a typical closed center steering systemusing a pressure compensated pump.This closed center steering system incorporates a closed center steeringcontrol, pressure compensated pump, engine,reservoir and return line filter.With a pressure compensated pump, a main relief valve is no longer requiredas overload protection for the steering control. The pressure compensatorlocated on the pressure compensated pump is now used for the steeringcontrols overload protection.In the neutral position, the fluid provided by the pump passes through thecheck valve and enters into the (P) port located in the steering control.This same inlet fluid is now blocked at the steering controls spool/sleeveassembly. In the neutral position, the pressure compensated pump willcreate only the pressure equal to the pressure compensated valves setting,and only the pump flow required to maintain that pressure.

T

L R

P

Reservoir

Engine PCPump

Filter

Closed Center Steering System( Neutral Position )

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This illustration is used to show the same closed center steering systemin the left turn position.In the left turn position, the fluid provided by the pump passes through theand enters into the (P) port located in the steering control.This same fluid then passes through the steering controls spool/sleeveassembly, metering section and out the (L) port to the hydraulic cylindersfor a left turn. The fluid located in the opposite end of the hydrauliccylinders is forced out and into the (R) port located in the steering control.This same fluid then passes through the steering controls spool/sleeveassembly, out the (T) port, through the return line filter, back to reservoir.As long as the pressure required to turn, is less then the pressurecompensators valve setting, the pump will remain at full stroke.Whenever the steering pressure exceeds the pressure compensators valvesetting, or the steering control is returned to the neutral position, thepumpwill automatically destroke to maintain only the pressure setting of thepressure compensators valve setting.

T

L R

P

Reservoir

Engine PCPump

Filter

Closed Center Steering System( Left Turn Position )

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This illustration is used to show a typical closed center load sensing steeringsystem using a priority valve and fixed displacement pump.When a fixed displacement pump is used with a priority valve, the EF portfunction of priority valve must be connected in a open circuit. The relief valvelocated in the priority valve is used for the steering controls overloadprotection and the main relief is used for protecting the EF port function.In the neutral position, the fluid provided by the pump passes through thepriority valve, check valve and enters into the (P) port located in the steeringcontrol. This same inlet fluid is now blocked at the steering controls spool/sleeve assembly. With the pump flow blocked at the steering controls spool/sleeve assembly, and no load sensing signal provided by the steering control,pump pressure will shift the priority control spool to the left to port the pumpflow out the EF port.

T

L R

P

Reservoir

EngineFixedPump

Filter

Load Sensing Steering System( Neutral Position )

Main Relief Valve

LS

LS

P

EFT

CF

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This illustration is used to show the same closed center load sensing steer-ing system using a priority valve and fixed displacement pump in the leftturn position.In the left turn position, and with a load sensing signal provided, the fluidprovided by the pump passes through the priority valve, check valve andenters into the (P) port located in the steering control. This same fluidpasses through the steering controls spool/sleeve assembly, metering sec-tion and out the (L) port to the hydraulic cyclinders for a left turn. The loadsensing signal provided by the steering control will shift the priority controlspool to the right to provide both the pump flow and pressure for the steeringfunction. The balance of the pump flow is ported out the EF port. The fluidlocated in the opposite end of the hydraulic cylinders is forced out and intothe (R) port located in the steering control. This same fluid then passesthrough the steering controls spool/sleeve assembly, out the (T) port,through the return line filter, back to reservoir. Again the relief valve locatedin the priority valve is used for the steering controls overload protection andthe main relief is used for protecting the EF portfunction.

T

L R

P

Reservoir

EngineFixedPump

Filter

Load Sensing Steering System( Left Turn Position )

Main Relief Valve

LS

LS

P

EFT

CF

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This illustration is used to show a typical closed center load sensing steeringsystem using a priority valve and pressure/pressure flow compensated pump.Like the previous system, the relief valve located in the priority valve is used forthe steering controls overload protection. When a pressure, pressure /flowcompensated pump is used in a steering system, the pressure compensatormay be used as the main relief for protecting the EF port function. For this tohappen, the load sensing signal provided by the steering control, must beprovided to both the priority valve and the pressure compensated pumpcontrol.In the neutral position, the fluid provided by the pump passes through thepriority valve, check valve and enters into the (P) port located in the steeringcontrol. This same inlet fluid is now blocked at the steering controls spool/sleeve assembly. With the pump flow is blocked at the steering controls spool/sleeve assembly, and no load sensing signal provided by the steering control,pump pressure will shift the priority control spool to the left to port the pumpflow out the EF port.

T

L R

P

Reservoir

EnginePFCPump

Filter

Load Sensing Steering System( Neutral Position )

LS

LS

P

EFT

CF

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This illustration is used to show the same closed center load sensing steeringsystem using a priority valve and pressure, pressure /flow compensated pumpin the left turn position.In the left turn position, and with a load sensing signal provided to both thepriority valve and pump control, the fluid provided by the pump passes throughthe priority valve, check valve and enters into the (P) port located in thesteering control. This same fluid passes through the steering controls spool/sleeve assembly, metering section and out the (L) port to the hydraulic cylin-ders for a left turn. The load sensing signal provided by the steering controlwill shift the priority control spool to the right to provide both the pump flowand pressure for the steering function. The balance of the pump flow is portedout the EF port. The fluid located in the opposite end of the hydraulic cylindersis forced out and into the (R) port located in the steering control.This same fluid then passes through the steering controls spool/sleeve assem-bly, out the (T) port, through the return line filter, back to reservoir. Again therelief valve located in the priority valve is used for the steering controls over-loadprotection and the pressure compensated control is used for protecting the EFport function.

T

L R

P

Reservoir

EnginePFCPump

Filter

Load Sensing Steering System( Left Turn Position )

LS

LS

P

EFT

CF

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Notes:


Copyright Eaton Corporation 1998All Rights ReservedPrinted in USAForm No. 3-303

Eaton CorporationHydraulics Division15151 Hwy. 5Eden Prairie, MN 55344

Eaton Ltd.Hydraulics DivisionGlenrothes, FifeScotland, KY7 4NWTelephone: +44 (0)1592-771-771Fax: +44 (0)1592-773-184

Eaton GmbHHydraulics ProductsAm Schimmersfeld 740880 Ratingen, GermanyTelephone: +49 (0)2102-406-830Fax: +49 (0)2102-406-800

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ACCREDITED BYTHE DUTCH COUNCILFOR CERTIFICATION

Reg. No. 24

Quality System CertifiedProducts in this catalog are manufacturedin an ISO-9001-certified site.

http://www.eaton.com

03-303 ORBITROL

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