Case CX47 Excavator Repair Manual

Model: Case CX47
Manuals: Shop Manual
Specification
Maintenance
System
Disassembling
Troubleshooting
Engine
Installation Procedures for Optional Attachments
Manual Extract:
Operating boom raise

With the boom raise operation, the pilot secondary pressure enters into the Pb8 port, and moves the spool for the boom operation. And with the movement of the spool, as the by-pass circuit is cut at the boom switching section, the oil received through the P1 port flows from the parallel circuit through the check valve installed on the upper part of the spool by-pass circuit for the travel operation into the parallel circuit on the boom switching section.

With the movement of the spool, as the circuit from the passage leading to the boom lock valve section to the bridge passage is opened, the oil entered in the parallel circuit passes through the load check valve on the boom switching section and flows into the B8 port through the bridge passage and open the boom lock valve (free flow) and is fed into the boom cylinder head side.

On the other hand, the return oil from the boom cylinder rod side flows into the A8 port, and with the movement of the spool the oil flows out into the tank circuit.
Consequently, the boom cylinder extends and raises the boom.
(See page 11 and 12 for lock valve)
The oil from the Pp port passes through the orifice provided on the P1 and P2 supply section and flows into the pilot circuit.

The oil entered into the pilot circuit flows from the travel switching section to the tank circuit, and the pilot circuit pressure becomes equal to the tank pressure, consequently the travel spool is not switched.