Tadano TT-800XXL1, Руководство по обслуживанию

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9
W 11 9-0500E
F-4. F-4.
Counterbalance Valve (Winch)
3. Principle of operation
B
A
B 1
Overload relief valve
A 1
a
d b c
IW 11 9-0500E03
3. 1 When control valve is in neutral
The holding pressure of the hydraulic motor is
locked by the seat area a of the check valve, the
land area d of the spool and the overload relief
valve.
3.2 Hoisting up
1 . When the control valve sends oil to port A, the oil
pushes open the check valve and flows to port A 1
connected to the motor.
2. On the other hand, the return oil from the motor
port enters through port B 1 , and then, is
discharged through port B to the control valve.
3.3 Hoisting down
1 . As oil is sent to port B by the control valve, it flows
to the motor via port B 1 .
2. The return oil from the motor is blocked at port A 1 ,
to raise the pressure at port B.
3. This pressure flows through choke b in the spool,
enters into chamber c, where it pushes the
plunger to the right by overcoming the spring force,
and opens land d.
4. As a result, the return oil from the motor is
discharged to the control valve via land d to drive
the motor.
5. When the load tends to pull the motor faster than
the speed corresponding to the flow rate to port B,
the pressure in chamber c drops.
6. Maintaining balance with the spring force to
automatically adjust the oil passage area in land d
to prevent the load from falling at speeds faster
than the motor drive speed.
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