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6-13
FUNCTION
2)
1
2
3
4
5
6
8
9
10
11
7
13
12
L1
X
B
S
L
LS pressure
X
4
10
12
13
75796WE33
1
Drive shaft
2
Swash plate
3
Shoe plate
4
Counter piston
5
Piston
6
Counter spring
7
Pressure & flow compensator valve
8
Piston shoe
9
Cylinder
10 Control piston
11 Control plate
12 Pressure compensator spool
13 Flow compensator spool
The steering pump and loader pump are variable displacement piston pump. The steering pump
and loader pump are flow controlled by LS signal. When the steering and loader are not being
used, the pumps are at low pressure standby.
The load sensing pressure that is sensed from steering and loader hydraulic systems flows to flow
compensator spool (13). This spool keeps the pump output at a level that is necessary to fulfill the
requirements for the system flow and for the pressure.
The pressure compensator spool (12) also limits maximum system pressure. The pressure
compensator spool (12) prevents damage to the steering and loader hydraulic components from
excessive pressure.
The swivel angle of the pumps is controlled by counter piston (4) and control piston (10). Counter
spring (6) cause swash plate (2) to move at maximum displacement or causes swash plate (2) to
upstroke.
Control piston (10) has a larger area (diameter) than counter piston (4). Control piston (10) causes
swash plate (2) to destroke the pump.
Flow compensator spool (13) and/or pressure compensator spool (12) changes pump output by
regulating the pump discharge pressure that is acting on control piston (10).
Summary of Contents for HL955
Page 557: ...7 6 MEMORANDUM MEMORANDUM ...