Section E - Hydraulics
Operation Description
Typical Valve Spool Operation
E-39 E-39
9803-9340-8
Spool Open Selected - 2
The illustration K Fig 31. ( T E-39) shows the service still
selected.
The oil entering the valve block flows past the spool A and
is then diverted by the spool to load hold check valve B
which, as the supply oil pressure is now above the service
line pressure, opens to allow oil to flow out of the valve
block to operate the ram.
Oil returning from the opposite end of the tilt ram enters the
valve block and flows past spool A into the exhaust gallery
and back to tank. In this instance the exhaust oil flows past
grooves machined in the spool which restricts the flow and
controls the ram movement.
Auxiliary Relief Valve C is preset to open at a specific
pressure. As the inlet oil pressure rises to the preset level,
e.g. when the ram reaches the end of its travel, the Relief
Valve opens, dumping excess oil directly into the exhaust
gallery.
707930A-1
Fig 31.
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