Specifications
84
7. Lift cylinder & tilt cylinder
Lift
cylinder
Type
Single-action piston type, with cut-off valve
Bore diameter
Φ80mm
Stroke
1495mm (Only for 3m lift height)
Tilt
cylinder
Type
Double-action piston type
Bore diameter
Φ115mm
Stroke
227mm
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.