Kohler K91 Owner's Manual page 291

HYDRAULIC COMPONENTS (cont'd)
Hydraulic Cylinder A hydraulic cylinder
converts hydraulic pressure and flow into linear
mechanical energy. I t consists of a sealed
chamber, piston, and piston rod. Cylinders can
be either single action or dual action.
Single Action Cylinder Single action
cylinders can only be powered in one direction.
Gravity or spring pressure is used to retract the
cylinder after extension.
These cylinders come in two different styles.
The typical version has a hydraulic line
connected on one side of the piston and is
vented to the atmosphere on the opposite side.
A displacement cylinder uses a large shaft
called a ram which replaces the piston and
piston rod. It can be serviced externally and
eliminates the need for an atmospheric vent.
Dual Action Cylinder A dual action cylinder
can be filled with oil on either side of the piston.
To extend the piston rod, oil is forced into the
bottom end of the cylinder and oil ahead of the
piston is pushed out of the cylinder. During
retraction, this process is reversed, allowing the
piston rod to be powered in both directions.
A typical double action cylinder can exert more
force during extension than it can during
retraction. This is because the piston rod takes
away from the piston surface area used to
retract the cylinder.
Force Pressure X Area
15
CHAMBER PISTON PISTON
ROD
3.4297.417
3.4297.418
r
I
3.4297.419
Productivity Series