7.1 Lift cylinder
The two lift cylinders of single acting type are used and located behind each outer
mast frame. The bottoms of the cylinders are sustained by the mast support of the outer
mast while the tops of cylinders, or the piston rod tops are inserted into the upper beam
of the inner mast.
The lift cylinder assembly consists primarily of a cylinder body, piston, piston rod
and cylinder cap. At the lower part of the cylinder body is arranged an inlet for
high-pressure oil, and at the upper part there is an outlet for low-pressure oil above the
piston packing, to which a return pipe is connected.
The piston is fastened to the piston rod with a steel clamp. A wear ring, packing
and back-up ring are attached to the outside periphery of the piston which is moved
along the inner surface of the cylinder by high-pressure oil. An oil seal and bushing are
installed on the cylinder cap which is screwed into the cylinder body. The bushing
supports the piston rod, and the oil seal prevents dust from entering the cylinder. The
upper end of the piston rod and inner mast upper beam is locked with bolts.
When the lift lever is tilted backward, high oil pressure is sent into the lift cylinders
through their inlets to push up the piston rods and the piston head, causing the forks to
rise through chains. The height from the ground to the fork upper position when the
inner mast channel beam upper ends exceed the outer mast upper ends is called “Free
lift” . Within this range, the mast height does not vary.
With the lift lever tilted forward, the piston rods of the lift cylinders descend by the
weights of the piston rods, inner mast, lift bracket, finger bar and forks, causing oil under
the piston to flow out of the cylinders. The oil discharged from the cylinders is regulated
by the flow regulator and returns through the control valve to the oil tank.
The structure of the lift cylinder is shown in Fig. 7.1.
Note: Please pay more regard to safety when adjusting the lift cylinder.
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