Section E - Hydraulics
Operation Description
Loader Valve Operation
E - 22 E - 22
9803-9450-2
Shovel Tilt
Fig 18.
Fig 18. (
X E-22) shows the shovel tilt service selected. On
servo machines, when the joystick is moved servo oil is
supplied to the appropriate end of the tilt spool 9c which
moves to select the service. On manual machines the
spool is operated mechanically by movement of the control
lever.
The oil entering the valve block flows past the first (lift)
spool and is then diverted by the tilt spool 9c to load hold
check valve 9g which opens only when the supply oil
pressure rises above the service line pressure. This
prevents unwanted ram movement due to a possible
momentary fall in line pressure. The pressurised oil then
flows out of the valve block to operate the tilt ram.
Oil returning from the opposite end of the tilt ram enters the
valve block and flows past spool 9c into the exhaust gallery
and back to tank.
Main Relief Valve 9a 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 Main
Relief Valve opens, dumping excess oil directly into the
exhaust gallery.
9c
9g
9f
9a
9c
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