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JCB 3CX, 4CX, 214e, 214, 215, 217 Backhoe Loader Workshop Service Manual

JCB 3CX, 4CX, 214e, 214, 215, 217 Backhoe Loader Workshop Service Manual
JCB 3CX, 4CX, 214e, 214, 215, 217 & Variants Backhoe Loader Factory Service & Shop Manual

JCB 3CX, 4CX, 214e, 214, 215, 217 Backhoe Loader Workshop Service Manual
Excavator Valve
Precision Control (Servo) (continued) JCB 3CX, 4CX, 214e, 214, 215, 217
(Machines from January 2003)
In the interest of machine efficiency and consistent backhoe operation the excavator valve is of a closed centre design and incorporates pressure compensating valves F, for each service.

These features enable the valve to operate as follows:
No service selected (all spools in neutral) Oil from the loader valve high pressure carry over enters the excavator valve at the inlet port A. Oil flows across the flushing valve spool assembly B and returns to tank from the outlet port C.

Servo Spool Actuation
When a service is operated servo pressure from the joystick control valve acts on the end of the relevant service spool D- and displaces the spool proportionally against the force of
the centering spring E, allowing the oil to flow to move the required service. When the servo pressure on the end of the service spool is reduced the force of the centering spring overcomes the servo pressure and the service spool will move back proportionaly to the central neutral position.

JCB 3CX, 4CX, 214e, 214, 215, 217 Backhoe Loader Workshop Service Manual
JCB 3CX, 4CX, 214e, 214, 215, 217 Backhoe Loader Workshop Service Manual
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When a Service is Selected
When one or more services are selected the pressure compensator valves F detect the service generating the highest pressure. This causes the flushing valve spool B to close and allow pump flow to the spools and service ports at sufficient pressure to move the load.

JCB 3CX, 4CX, 214e, 214, 215, 217 Backhoe Loader Workshop Service Manual

Load hold check valves
G prevent the load falling back if the load pressure is greater than the pump pressure. The closed centre design ensuresconsistent service operation regardless of load. For a full description of spool and pressure compensator valve operation see Load Sense – Pressure Compensator Valve Operation.

JCB 3CX, 4CX, 214e, 214, 215, 217 Backhoe Loader Workshop Service Manual