Hyundai r35z-7 Workshop Manual page 52

4) Operation of boom lock valve
( ( 1) Holding
In the boom spool neutral condition,
The pilot piston chamber (a) is connected to the drain passage through the pilot port (Pb8') for
releasing the boom lock valve.
The piston chamber (b) is also connected to the drain passage through the drain port (Dr2).
Therefore, the piston (B) maintains the condition shown in the figure.
The boom cylinder holding pressure (shown in half-tone dot meshing) is applied to the lock valve
chamber as shown in the figure to :
Press the needle valve against the needle valve seat.
Press the lock valve against the body seat.
Then, oil leakage from the boom cylinder head side is prevented to stop the movement of the
boom cylinder due to leakage.
Piston chamber(b)
Neddle valve seat
Pilot piston
chamber(a)
Pb8'
Piston B
Force applied to neddle valve
Holding pressure
Body seat
Lock valve
chamber
Dr2
Piston A
Needle
valve
Operation of boom lock valve (holding)
2-20
B8 port
A9
Lock valve
Force applied to lock valve
R35Z72MCV15