Port 1 To Port A: Free Flow; Port A To Port 1: Flow Control Released - Kubota KX080-3 Workshop Manual

WSM KX080-3 Mechanism

Port 1 to Port A: Free flow

The pressure oil supplied out of port 1 flows through the hole
(a) and orifice first and then through the hole (b) up to the
port A.
The resistance in passing through the orifice makes the
pressure of chamber (i) lower than that of chamber (ii), which
moves the plunger upward.
When the plunger has reached up, the hole (c) gets open
and the entire pressure oil flows out to port A.
With no pressure oil flow, the plunger is brought back to the
neutral position by the spring force.
A: Boom C/V section pilot chamber
1 : Boom down pilot line to return

Port A to Port 1: Flow control released

Usually the spool (5) is held at the neutral position by the left and right springs (6). The pressure oil from
the port A is therefore cut from the port T with the hole (d) in between. As discussed in Fig. 2, the flow
through the port A is controlled. (Left layout in Fig. 4)
When the pressure at port 2 rises above the force of spring (6), the spool moves and allows the ports A
and T to connect each other. The pressure oil through the port A therefore flows down directly into the
tank, which releases the flow control at port A.
(17)
(d)
A: Boom C/V section rod side pilot chamber
B: Boom C/V section bottom side pilot chamber
: Pilot valve port, boom down
: Pilot valve port, boom up
See Fig. 3.
See Fig. 4.
(18) (19)
Fig. 4.
IV-M-111
(c)
Fig. 3.
(20) (d)
IV Hydraulic System
(i)
(b)
(a)
(ii)
(21) (22)
(17) Port 1 passable
(18) Port T passable
(19) Port 2 passable
(20) Port 1 passable
(21) Port T passable
(22) Port 2 passable