jcb JS300 Service Manual page 890

Tracked excavators - tier 4i isuzu engine

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Section E - Hydraulics

Cushion Valve

Cushion Control Off

Fig 6. Cushion Control Off

When the cushion switch is illuminated, the cushion

solenoid is energised and pilot pressure is fed to port S on

the cushion valve. The two inner left and right cushion

spools are both pushed into the centre of the outer spool,

so that the unrestricted galleries X and the cushion valve

spools are open to allow the pilot outputs from the hand

controller to pass through the valve unrestricted, to the

main control valve. When the dipper hand controller is

operated, pilot pressure from the lever to port A, moves the

outer spool to the right and pilot pressure is fed to the

dipper spool in the control valve, via port C. At the

conclusion of the hand controller operation, the returning

pilot oil, goes straight back to the lever, with no restriction.

There is no cushioning effect. Hot oil from port R returns to

tank via the dipper hand controller, as it does in the

K Fig 6. ( T E-229)

warming circuit in the neutral position.

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