Hyster F004 - Three-Stage Mast with Full Free-Lift

4000 SRM 736 Description and Operation
1. MAIN LIFT CYLINDER (2)
2. OUTER WELDMENT
3. FREE-LIFT CYLINDER
4. INNER WELDMENT
5. CHAIN SHEAVE
6. LIFT CHAIN
7. CARRIAGE
8. FROM MAIN CONTROL VALVE
9. EXTERNAL LOWERING CONTROL VALVE
10. INTERNAL LOWERING CONTROL VALVE
Figure 3. Two-Stage Mast With Full Free-Lift
During lowering, main lift cylinders lower first be-
cause they have a greater load. After main lift cylin-
ders have retracted, free-lift cylinder lowers. All oil
from the lift cylinders flows through the lowering
control valves to the hydraulic tank.
THREE-STAGE MAST WITH FULL
FREE-LIFT
The three-stage mast with full free-lift (FFL) has an
outer, an intermediate, and an inner weldment. See
Figure 4. Three single-stage lift cylinders are used
to raise the carriage and extend weldments. Weld-
ments are telescopic and have load roller and strip
bearing arrangements similar to the two-stage mast.
Two main lift cylinders are installed at the back of
the outer weldment. The base of each lift cylinder
is held on a mount at the bottom of the outer weld-
ment by brackets. The top of each main lift cylinder
(cylinderrod)fitsintoaguideatthetopofthein-
termediate weldment. A clamp holds the top of the
lift cylinder in position on the outer weldment. The
free-lift cylinder is installed in the inner weldment
andheldinpositionbytwoclamps.
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