,

SECONDARYRELIEF VALVE

CLOSED"J"

INLETFROM PUMP

CHECK VALVECLOSED

"28"~

TO BUCKETCYLINDER

HIGH PRESSURE OIL

LOW PRESSURE OIL- STA TIC OILBN25463

Figure 36 - Oil Flow Through Open Center (Loader Models)

' /

CHECK VALVE CLOSED

TO BUCKETCYLIN D'ER

HIGH PRESSURE OIL

LOW PRESSURE OIL

_STATIC OIL

BN25363

Figure 37 - Oil Flow Through Open Center (Loader - Backhoe Models)" /

IX- 1 8

",/

,.

' J

...

SUMP

' J F.

...

"---/

.-... .PUME.

.....

BUCKET CYLINDERS

HYDRA - LEVELINGCYLINDER

FILTER

LIFT CYLINDERS

.

..

.

SPOOL POSITIONS,-,FLOAT' I,_.I,-, ,-,

LOWER I J f I DUMP'_.I ,_/

.IIIc:Jl1li.

.HIGH PRESSURE OIL

LOW PRESSURE OIL

STATIC OIL

SUMP OIL

\NEUTRAL C). NEUTRALRAISE . '-,I J,_.I ROLLBACK

LEVER POSITIONS

Figure 38 - Oil Flow Through Valve - Raising Bucket

IX-I 9

..

..

BN25163

..

SUMP

..

I'

.

;II

,,

IjHof

11'.

FILTER

.",.';'

..-.PUMP .

-ill

BUCKET CYLI NDERS

.

..LIFT CYLINDERS

..

HYDRA-LEVELINGCYLINDER

.. HIGH PRESSURE OILD LOW PRESSURE OIL- STATIC OILIII SUMPOIL

SPOOL POSITIONS

FLOAT (-','_.ILOWER (-', (-'I DUMP'-.I -.I

NEUTRAL.c:' NEUTRALRAISE (-\ . ROLLBACK,_.I

LEVERPOSITIONS

Figure 39 - Oil Flow Through Valve - Rolling Bucket Back

IX-20

~

"

.. ~

~

..

~BN25063

~

\..J

SUMP

' /

~

..

.

..

..

.

FILTER..

.

PUMP -..

..

. .HYDRA-LEVELING

CYLINDER

1

~

BUCKET CYLINDERS

.

LIFT CYLINDERS

.

.

FLOAT ,,-,I I'-"

LOWER. 8 BUCKET DUMP,,-, ,,-,

NEUTRAL I I ( I NEUTRAL'-" '-", ,,-

RAISE~, ) ROLLBACK. '-" ~-"

LEVERYOSITIONS

..

...

. .. HIGH PRESSURE OILD LOWPRESSUREOILlEI STATIC/OILIII[] SUMP OIL

Figure 40 - Oil Flow Through Valve - Lowering and Dumping Bucket

IX-21

..

..

BN25563

-

.-J

I~--I: III

II

SUMP~.. J

11

.1

.

'

1

'

-M,

-.

.PUMP

~

BUCKET CYLINDERS

LIFT CYLINDERS

.

NEUTRAL (). NEUTRAL

RAISE,-, ,-,I I I J'-" '-"

ROLLBACK

LEVER POSITIONS

~

~

I~i

~

.

"

" /

HYDRA - LEVELINGCYLINDER

" /

III HIGH PRESSURE OIL

D LOW PRESSURE OIL

~ STATIC OILIbJ SUMP OIL

Figure 41 - Oil Flow Through Valve - Float Position

IX-22

BN25263" /

SPOOL POSITIONS

FLOAT 8LOWER

,-, ,-,DUMPr I r I

'-' '-"

" /INLET FROM PUMP

VALVE POPPET OPEN SECONDARY RELIEF VALVE CLOSE

\TO BUCKET CYLINDER

- HIGH PRESSURE OILLOW PRESSURE OIL.. STATIC OIL

BN25663

Figure 42 - Oil Flow Through Valve - Main Relief Valve By-Passing

' /

INLET CHECK VALVEOPEN

MECHANICAL ACTUATEDHIGH PRESSURE

_HIGH PRESSURE OILLOW PRESSURE OIL

~TATIC OIL

BN25763

~Figure 43 - Lift Spool and Bucket Secondary Relief Valve Actuated

IX-23

8. HYDRA-LEVELINGCIRCUIT

\...J

[gJw[Q)~~Q[lrnwrn[larro@~a~~[!JJalJ~

-OIL DISPLACED BY HYDRA-LEVELING CYLINDERNOTE'COLORS AREREVERSED WHENLOWERINGLOADER

OIL DISPLACED BYDUMP CYLINDERS

RAISE

BN24863

Figure 71 - Hydra-LevelingCircuit - Raising Bucket

As the loader arms are raised, the position ofthe bucket changes in relation to the ground. Itis the purpose of the hydra-leveling circuit to keepthe bucket level in relation to the ground at all timesduring the lift cycle,. This is accomplished verysimply by oil displacement.

the bucket back.

This hydra-leveling action may be overridden atany time by actuating the bucket cylinder spool ofthe loader control valve.

As the loader arms are raised, the piston rod ispulled out of hydra-leveling cylinder. This forcesoil out the top of hydra-leveling cylinder into thefront of the bucket cylinder causing the bucket toroll forward, see Figure 71.

As the loader arms are lowered, the piston is

pushed back into the hydra-leveling cylinder. Thisforces oil out the bottom of the hydra-leveling cyl-inder and into the rear of the bucket cylinder rolling

\~ IX-31

I