Komatsu PC500LC-10R Shop Manual page 336

COMPONENT PARTS OF SWING SYSTEM
OPERATION OF SWING MOTOR REVERSE PREVENTION VALVE
When brake pressure occurs in port (MB)
1.
Pressure (MB) flows to chamber (d) through notch (g).
2.
Spring (6) is compresses by the circle area difference of
spool (5) (diameter D1 > diameter D2). Spool (5) is moved
to the left.
3.
Port (MB) and chamber (e) are connected.
4.
Spool (2) does not move since pressure (MA) is the set
pressure of spring (3) or lower. The pressurized oil is
closed and the braking force is secured.
When motor reverse pressure occurs in port (MA)
1.
The motor rotates in reverse by the closed pressure gener-
ated in port (MB). (First reverse rotation)
2.
The reverse pressure is generated in port (MA) side. Pres-
sure (MA) flows to chamber (a).
3.
Spring (3) is compressed by the circle area difference of
spool (2) (diameter D3 > diameter D4). Spool (2) is moved
to the right.
4.
Port (MA) and chamber (b) are connected.
5.
The oil flows through drilled hole (h) of spool (5) and port
(b) and port (f) are connected. The reverse pressure of
port (MA) is bypassed to port (T) to prevent the second re-
verse rotation.
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10 STRUCTURE AND FUNCTION
PC500LC-10R