E
lectric
C
ounterbalance
H
igh
O
utput
Elevating
3/10/00
7.2
CENTER CYLINDER
The center cylinder is cushioned at the top of its
stroke. There is hydraulic oil on the rod side of
the piston. There are two orifices in the rod, one
larger than the other (Items 3 and 4). As the rod
extends, the hydraulic oil on the rod side is
forced underneath the rod through the large
orifice (3). When the rod extends near the end
of its stroke, the gland nut at the top of the
cylinder closes the large orifice (3). The
remainder of the hydraulic oil must flow through
the small orifice (4) providing a cushioning
effect.
1. Cylinder Rod Assembly
2. Cylinder Shell
3. Large Orifice
4. Small Orifice
5. Wear Ring
1
2
3
4
5
s s
FIGURE 7.2 - CENTER CYLINDER CUSHIONING
OUTER CYLINDERS
The outer cylinders are cushioned at the bottom
of their stroke. As the rod retracts, the hydraulic
oil flows out of the cylinder through the port (3).
When the rod is retracted near the end of its
stroke, the piston ring (6) is below the port
opening. The hydraulic oil below the rod must
flow through the small orifice (4). This cushion
effect prevents a sudden stop at the end of the
lowering sequence, making a smoother lowering
operation.
1. Cylinder Rod Assembly
2. Cylinder Shell
3. Port
4. Small Orifice
5. Wear Ring
6. Piston Ring
1
2
3
4
5
6
FIGURE 7.3 - OUTER CYLINDER CUSHIONING
