9-M16
BX24, RCK54(P)-23BX, RCK60B-23BX, LA240, BT601, WSM
BACKHOE
(3) Overload Relief Valve
Overload relief valve in this control valve is a
combination valve combining a relief operation and anti-
cavitation operation.
Relief Operation
When the control valve is in the neutral position, both
cylinder ports of control valve are blocked by the spool.
If an external load is imposed on the cylinder, pressure
builds in the circuit.
When the pressure exceeds the set level of the
overload relief vale, the relief valve opens and the oil
returns to tank. In this way, the hydraulic circuit and
actuator are protected from excessive pressures.
Anti-cavitation Operation
Overload relief valve also has anti-void function. If a
negative pressure takes place in the circuit, the oil is fed
from the tank to eliminate the negative pressure.
W1023498
Relief Operation
[When the actuator port pressure is lower than the
setting]
The cylinder port HP is applied to the seat B in the
following route : first through the throttle a of the piston
poppet (1) built in the relief valve poppet (5), second
through the spring chamber A, and then through the
circular clearance between the adjusting screw (9) and
the piston poppet (1). This cylinder port HP works to
open the pilot poppet (2). Because the piston spring (3)
has not reached the set pressure, however, the valve
stays shut. In this way the seat remains intact and the
relief valve poppet (5) stays shut.
W1024073
(1) Overload Relief Valve
(2) Control Valve
(3) Housing
(4) Check Valve Poppet
(5) Relief Valve Poppet
(6) Piston Spring
(7) Piston Poppet
(8) Lock Nut
(9) Adjusting Screw
(10) Pilot Spring
(11) Pilot Poppet
(12) Pilot Section
(1) Piston Poppet
(2) Pilot Poppet
(3) Piston Spring
(4) Adjusting Screw
(5) Relief Valve Poppet
HP :High Pressure
LP :Low Pressure
A : Chamber
B : Seat
a : Throttle
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