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U20-3, U25-3 WSM
h. Relief valve/Anti-cavitation
valve
Function of relief valve
(1) The pressure oil passes first through the piston
that is built in the main poppet. It then goes
through the orifice B and fills the chamber A.
Now the main poppet and socket are well
fitted, whereas the socket and body seat are
also ensured together.(Fig.1)
(2) When the pressure oil at the port P has
reached the spring's set pressure, the piston is
pushed, which in turn pushes the pilot poppet
open.
Now the pressure, oil flows in this way: piston,
orifice B, chamber A, ring orifice A, and port D.
It finally passes around the socket into the tank
port. (Fig.2)
(3) With the pilot valve open, the pressure in the
chamber A drops. The main poppet then
opens, and the pressure oil at the port P goes
through the port E and directly reaches the
tank port. (Fig.3)
(4) When the pressure at the port P has dropped
below the spring's set pressure, the pilot
popper is pressed against the seat by the
spring force and the pressure of chamber A
becomes equal to that of port A. The main
poppet is also pressed against the socket seat
resulting in the original state(Fig.1)
Function of anti-cavitation valve
(1) This valve works to feed the oil from the tank
port if a negative pressure occurs at the port P.
When the pressure at tank port has risen
above that at the port P, the socket is activated
upward.
This upward force makes a space between the
body seat and the socket. The oil now comes
through the tank port into the port P and fills
the space. (Fig. 4)
(2) This valve works to feed the oil from the tank
port if anegative pressure occurs at the port P.
When the pressure at the tank port has risen
above that at the port P, the valve is activated
upward.
This upward force makes a space between the
body seat and the valve. The oil now comes
through the tank port into the port P and fills
the space. (Fig.5)
Hydraulic system (Mechanism section)
IV-M-25
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