channels and the bottoms of the cylinders are connected with the cylinder supporter of
the outer mast by bolts and pins, while their tops (i.e. piston rod heads) are held by the
inner mast piston head guide. Two piston rods should be synchronous during the
lifting or lowering. Readjusting the strokes of two pistons or article 28& 29 shown in
Fig.9-8 should be done, if they are not so.
The lift cylinder consists primarily of cylinder body, piston, piston rod, cylinder
cap, cylinder base and oil seals. At the lower part of the cylinder body is an inlet for
high-pressure oil and at the upper part is arranged the return pipe which allows leak
oil from the clearance between the piston and cylinder body to return to the oil tank.
The piston, fastened to the piston rod with castled nut and cotter pin is fitted with a
Yx-type seal, snap ring and packing on its outer periphery. It moves up along the inner
surface of the cylinder by high-pressure oil from the cylinder bottom. With press-fitted
bushing and dust seal, the cylinder cap is screwed into the cylinder body. The bushing
supports the piston rod and the dust seal keeps dust off. The stroke of the piston can be
adjusted with cylinder cap.
When the lift spool is pulled backward, high pressure oil flows into the lift
cylinder through the cylinder bottom and pushed up the piston, causing the forks and
inner mast to rise with the aid of lift chains. When the lift spool is pushed forward, the
piston descends because of the weight of load and all of lifting parts, causing the oil
under the piston to flow out of the cylinder. The oil flow discharged from the cylinders
is regulated by the flow regulator valve and returns through the control valve to the oil
tank.
-77-
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