Allied Telesis 595 - Manual (Page 21)

The hydraulic self-leveling system (HSL) utilizes two metering cylinders
which displace oil into or out of the bucket cylinders as the loader is raised
or lowered. The cylinder volumes and geometry’s are carefully matched
for each loader model to provide the correct amount of oil to keep the
bucket level after it is initially leveled.
The HSL system incorporates two relief valves which are only utilized if
the bucket cylinders are at either end of the stroke. If the loader is
raised with the bucket fully dumped, oil will be bypassed at high
pressure into the lower side of the lift cylinder circuit. If the loader is
lowered with the bucket fully rolled back, oil will be bypassed at high
pressure into the raised side of the lift cylinder circuit. Note that these two
conditions are likely to occur only intermittently, and although the pump
will be forced to supply oil at a higher pressure no damage to the loader
components will occur. It is, however, recommended to avoid the above
situations and keep the bucket somewhat level while raising or lowering
the loader for smoother operation.
Note that the large volume (piston side) of the leveling cylinders is
connected to the large volume of the bucket cylinders, and the small
volume (rod side) is connected between the two sets of cylinders. The
effect of this configuration is to create a breakout force “boost” if the
bucket cylinders are pressurized toward the rollback position during
breakout.
The opposite effect of the above situation is that the loader will have poor
lift capacity if lifting with the bucket cylinders pressurized in the dumped
position. This is, however, a very unlikely occurrence (lifting a load with
bucket fully dumped).
The cartridge style relief valves are factory set at 2,000 psi cracking
pressure and are capable of bypassing 15-20 GPM. If loader lock-up
should occur due to a low tractor relief setting, higher inlet flows or return
line restrictions, the relief valve setting may be bucket off slightly until the
lock-up condition is overcome (as described in note 2 above).
CAUTION: Never utilize the leveling cylinders to raise the loader. This
could occur if the lift cylinders are placed in float while the bucket cylinders
are held pressurized in the retracted position. If the loader should rise,
pressurize the lift cylinders to lower it; otherwise a rapid drop may occur
when the bucket cylinders are extended. Note that this situation is unlikely
to occur during normal loader operation and is possible only with a lightly
loaded bucket.
General Notes and Instructions to the Operator -
Regarding ALLIED HSL Loader Operations
19