Case 580SR Service Manual page 618

www.maskinisten.net
28
One hydraulic circuit operating
When a single hydraulic circuit is operated the spool
in the control valve section is moved allowing oil to
flow past the lands of the spool and apply pressure
to the metering element of the pressure compensat-
ing valve.
The metering element moves upwards to allow oil to
flow to the load check valve and at the same time
uncovers the drilling in the spool portion of the pres-
sure compensator valve enabling operating pres-
sure to be sensed in the load sense gallery.
As pressure increases to open the load check valve,
load sense pressure is applied to the spring side of
the flow balancer valve in the backhoe control valve
end cover. A higher pressure is now required to op-
Pump pressure
Load sense pressure
Return to oil tank
1. Load sense bleed orifice 1 l/min
2. Load sense limiter (system relief valve)
3. Return to oil tank
SECTION 35 - HYDRAULIC SYSTEM
1
7
Flow balancer valve operation - Hydraulic circuits operating
erate the flow balancer valve and pump pressure in-
crease accordingly.
When pump pressure overcomes the pressure be-
hind the load check valve, the valve opens allowing
oil to flow into the cylinder port.
Exhaust oil from the cylinder returns to tank through
the other port in the control valve section.
If pressure in a load sensing system reaches 195
bar, the safety valve in the side cover of the backhoe
attachment control valve will operate. Pump pres-
sure is now limited to 210 bar. This is the pressure
required to overcome the pressure of the flow bal-
ancing valve spring (15 bar) plus the load sensing
pressure controlled at 195 bar.
2
6
4. Load sense line
5. Pump flow balancer (unload) valve
6. Pump flow IN
7. To backhoe control valves
Copyright ©
3
4
5
F29289