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Operation
Functional Description
The HC control consists of a ported housing, mounted directly on the end cap. It contains a check valve, a
shuttle valve, a piston, a connecting pin, and a bias spring. The HC control does not have pressure
compensating override (PCOR) function.
Check Valve
The check valve resolves which port (system A or B) is at higher pressure. It routes that higher pressure to
the 4-way valve to power the servo piston.
Shuttle Valve
The shuttle valve ports higher signal pressure to the top of the servo piston. It ports lower signal pressure
to the bottom of the servo piston.
Connecting Pin
The connecting pin links the piston to the 4-way valve. The bias spring holds the piston and pin against
the 4-way valve. A threshold spring and ramp spring(s) act on the opposite end of the 4-way valve.
HC Schematic Diagram
M4
M3
M1
L1
L2
M5
M2
B
Max.
displ.
X2 X1
A
P101 875
Repair
Diassembly
1. Using a 10 mm wrench, loosen locknut (M40).
2. Using a 4 mm internal hex, remove bleed valve (M38).
3. Using a 1/4-inch internal hex, remove plug (M48)
Service Manual
Series 51 Hydraulic Proportional Controls Service Manual
HC Controls
28
11009446 • Rev BA • July 2014