jcb JS200 Service Manual page 448

Section F
3 - 6
Operation (continued)
Shuttle Function
The counterbalance valve has a shuttle function. When the plunger moves from the position in Fig. 5-1 to that of Fig. 5-2, the
parking brake release port P3 is opened to guide the pressurised oil to the brake releasing cylinder cavity. This releases the
parking brake. When the motor stops, the counterbalance valve becomes as shown in Fig. 5-1 and P3 port is blocked and the
drain port in the motor case is opened. The pressurised oil in the brake is exhausted into the motor case to activate the brake.
Fig 5-1. Shuttle Function
Relief Valve
The relief valve determines the drive force and brake force which controls the machine travel and is located on the cross line.
This valve also provides the shockless function which reduces shock during acceleration.
The relief valve is constructed as shown in Fig. 6.
a. Area differential type directly driven relief valve
b. Shockless piston
With the shockless type relief valve, reduction of shock and stress on the structure is achieved.
Relation of relief valve set pressure and adjuster amount
Per one rotation approx. 8.6 Mpa {88 kgf/cm
Do not make adjustments unless there are problems.
9803/6400
Transmission
Motor/Gearbox
}
2
Fig 6. Relief Valve Section.
Fig 5-2. Shuttle Function
Section F
3 - 6
Issue 1