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Section D
40 - 4
Pilot Control Valves
Dismantling, Inspection and Assembly
Note that the procedure shows the right hand control valve.
The procedure for the left hand valve differs only in the
location of one way restrictors 4 and orientation of joint
mechanism assemblies 2.
Dismantling
1
Undo the three cap screws 1. Lift off the joint
mechanism assembly 2.
2
Pull out the four valve capsule assemblies 3.
3
Remove the six adaptors 16 from the ports. Note that
the adaptors incorporate seals. Note that one way
restrictors 4 are fitted to some ports as follows:
Right hand valve - ports 1 and 3.
Left hand valve - ports 2 and 4.
Inspection
1
Inspect the underside of the wobble plate 5 for signs of
excessive wear. If wear is evident the complete
assembly 2 must be renewed.
2
Inspect the universal joint for signs of excessive play. If
wear is evident the complete assembly 2 must be
renewed.
3
Inspect the mating faces of plungers 6 and bushes 7 for
signs of excessive wear. If wear is evident the valve
capsule must be renewed as a complete assembly.
4
If the valve has been contaminated with debris be sure
to remove it from all internal drillings. Carefully inspect
the mating faces of spools 8 and body 9. If scoring is
evident the complete valve must be renewed.
5
Make sure that one way restrictors 4 are free from
debris.
9803/3280
Precision Control (Servo)
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Controls
Assembly
Assembly is the reverse dismantling but note the following:
1
The valve assembly is susceptible to malfunction and
damage if it is contaminated with debris or dirt. Make
sure that all components are clean and free from
debris.
2
Renew all 'O' rings 14 and seals 15.
3
Be sure to fit the one way restrictors 4 the correct way
up and in the correct ports. See Dismantling, Step 3.
4
Apply JCB HP Grease to the mating faces of wobble
plate 5 and plungers 6.
5
Be sure to orientate the joint mechanism assembly 2
correctly. On left hand valves note that the slot Z aligns
with port 2 as shown at A. On right hand valves the slot
Z aligns with port 1 as shown at B.
6
If the joint mechanism assembly 2 is to be renewed it
must be adjusted correctly. With the assembly fixed in
position, check the dimension X. The wobble plate 5
must be positioned so that it just makes contact with
the top of the valve plungers. If there is a gap at X, or if
the plate is depressing the plungers adjust as follows:
Hold the collar 11 using a suitable rod located in hole Y.
Slacken the lock nut 10 and then screw the collar 13 up
or down as required. Tighten the lock nut 10.
Torque Settings:
Item
Nm
1
9
10
9
16
30
Section D
40 - 4
Kgf m
lbf ft
1
7
1
7
3
22
Issue 1
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