Komatsu 930E-2 Shop Manual page 454

BLEEDDOWN MANIFOLD
The pilot valve/hoist valve hydraulic circuit is routed
through the bleeddown manifold, located on the left
frame rail. The hoist-up solenoid and pilot operated
check valve described below are contained in the
manifold. Refer to Section L4 for additional information
concerning these components.
Hoist-up Limit Solenoid
The hoist-up limit solenoid (5, Figure 7-1), located on
the the bottom of the bleeddown manifold, is used in
the hydraulic circuit to prevent maximum hoist cylinder
extension.
The solenoid valve is a 3-way valve, and is controlled
by a proximity switch (hoist limit switch) located near
the body pivot and the right rear suspension upper
mount.
When the body is nearly fully raised, the body activates
the magnetic proximity switch, signalling the solenoid
to open the "raise" pilot line to tank, and close the
"raise" pilot line to the hoist valve, stopping further oil
flow to the hoist cylinders.
Refer to Section "D", Electrical System (24VDC) for
adjustment procedure of the hoist limit switches
Pilot Operated Check Valve
The Pilot Operated Check Valve (6, Figure 7-1), lo-
cated in the bleeddown manifold, is opened by power
down pilot pressure to allow oil in the raise port to
by-pass the hoist up limit solenoid for initial power
down operation while the solenoid is activated by the
hoist limit switch.
L7-4
OVERCENTER MANIFOLD
The overcenter manifold (4, Figure 7-4), located on the
pump module at the rear of the hoist valve (1) contains
the counterbalance valve (2). This valve controls the
pressure of the cushion of oil in the annulus area of the
hoist cylinder when the body approaches the maxi-
mum dump angle. The valve limits the maximum pres-
sure build-up by relieving pressure in excess of 3000
psi (20, 400 kPa), preventing possible seal damage.
Quick Disconnect fittings (5) mounted on the bottom
of the manifold allow service personnel to dump the
load in a disabled truck by connecting jumper hoses
from an operational truck, utilizing its hydraulic system.
FIGURE 7-4. PUMP MODULE
1. Hoist Valve
2. Counterbalance Valve
3.Needle Valve
4. Overcenter Manifold
Hoist Circuit
5. Quick Disconnects
6. Steering/Brake Pump
7. Hoist Pump
L07023