2-39
Function of boom priority valve
(9)
During both the swing operation and the boom hoisting operation, the pilot pressure enters
through ports PAs(or PBs), PBb and Pns. The pressure Pns transfers the piston (356) and the
spool (107) to the down direction, and the path from (a) to (b) is closed. Hereby, the pressurized
oil pushes open the poppet (102), passes in the path (c) and (d), enters into the chamber (e),
and the poppet (101) is pushed to the casing seat. Therefore, the most of pressurized oil
entering through port P2 flows to the boom priority spool (393) than the swing spool (305) to
make the boom hoisting operation most preferential.
On the other hand, in the independent swing operation, the pilot pressure does not enter through
ports Pns, and the path from (a) to (b) is not closed, and oil of chamber (e) flows to the path (a)
and (b). The pressurized oil entering through port P2 pushes open the poppet (101) and flows to
the swing spool (305).
(e)
(d)
(a)
(b)
(c)
356
107
Pns
Bs
As
102
PBs
SWING SPOOL
from PZ
PAs
3607A2MC26
