SPECIFICATIONS

Vehicle Systems Systems Operation
Lift Cylinders and Mast
Standard Lift
Standard Lift Mast
(Typical Example)
(A)Free lift period.
The rods of Standard Lift Cylinders (1) and (2) are
moved up by oil under pressure and go back to their
original position by gravity.
The combination of the single-acting hydraulic lift
cylinders with other mechanical lifting components
will operate as follows:
When the control valve lift lever is pulled back, the
hydraulic oil under pressure, pushes against the rods
at the bottom of the lift cylinders. The inner mast
crossbar, which is connected to the top of the
cylinder rods, begins to move up. At this time, the
carriage also starts to move up because it is
connected to the inner mast through the lift chains
arrangement. From the start of the lift cycle until the
top of the inner mast becomes equal height to the
top of the outer mast, the carriage and mast are in
their free lift period (A).
The inner mast moves at a 1 to 1 ratio and the
carriage moves at a 2 to 1 ratio with the rods of the
lift cylinders.
Standard Lift Mast At Full Extension
(Typical Example)
(1) Lift cylinder. (2) Lift cylinder.
The inner mast and carriage will continue to move up
until they are in the extended position. If the control
valve lift lever is held in the lift position with the mast
fully extended, the pressure relief valve in the control
valve will release the extra pressure until the lift lever
is released. The oil flows through the relief valve and
the control valve into the hydraulic tank. The carriage
and inner mast will be stationary at this full height
until the lift lever is moved to the lowered position.
When the lift lever is moved forward, the oil under
pressure is released in the lift cylinders. Gravity and
the weight of a load will cause the carriage to move
down at a 2 to 1 ratio and the inner mast to move
down at 1 to 1 ratio with the rods of the lift cylinders
until the carriage and mast are completely lowered.
The flow regulator located between the outer mast
near the base of the lift cylinders, permits 54 to 66
liter/min (14 to 17 U.S. gpm) of oil flow back through
the control valve and into the hydraulic tank.
The lift cylinders also have excess flow protectors.
These flow protectors act as a lowering flow control
valve if an oil line is broken between them and the
flow regulator located near the base of the lift cylin-
ders.
The carriage and inner mast move up and down
smoothly on load bearings (rollers). Stability of the
mast and carriage is controlled by bearing size and
shims behind the bearings (rollers).
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IDCS001P IDCS002P
(A)
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2