Auxiliary Spool - jcb 214e Service Manual

Backhoe loader

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Loader Valve - Variable Flow

Auxiliary Spool

The auxiliary valve section comprises the spool assembly A,

load hold check valve assembly B, primary and secondary

shuttles, items L and K respectively.

While the spools are in neutral position, the primary shuttles

and secondary shuttles are vented to tank. When a spool is

operated, the load pressure sensed at the work port is

directed via the primary and secondary shuttles to the

hydraulic pump, where the pump subsequently 'swashes'

and increases its output to meet this load sense demand.

When a service is selected (the spool moved up or down),

the waisted sections of the spool connect passage C to one

of the service ports D. Oil from the pump must overcome the

force of spring E to lift poppet F and make the connection

from the pump passage J to the service ports D via passage

In some instances there is a back pressure in the service line

(e.g. generated by the weight of a loaded shovel). This

pressure is felt in chamber G via drilling H in poppet F. The

back pressure combined with the force of spring E keeps

the load hold check valve firmly closed, preventing the load

from dropping.

The pressure in pump passage J will increase until it is

greater than that in the service line. At this point, the load

hold check valve will open, as previously described.

Circuit Descriptions

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