TYPES OF HYDRAULIC CYLINDERS BY FUNCTIONING
Most of you are aware that pumps deliver energy to a hydraulic system by converting mechanical energy into
hydraulic energy. But once the pump delivers that energy, do you know how it is
utilized in the hydraulic system? Well, the answer to that is the motion of the
components. The energy from the hydraulic fluid is used to move the components.
This movement is achieved by using actuators in a hydraulic system.
A hydraulic system can use various
types of actuators that convert hydraulic energy into mechanical motion. Linear
actuators convert the energy into linear mechanical motion, while rotary
actuators convert the energy into rotational motion. A hydraulic cylinder is a type of
linear actuator that converts fluid power into linear motion. This linear
motion is achieved by extending and retracting a piston rod by applying
pressure through the hydraulic fluid or oil.
Generally, there are two types of
hydraulic cylinders based on their functions. The simplest type is called a
single acting cylinder. Just as the name suggests, in a single acting cylinder,
the pressure from hydraulic fluid can only actuate the cylinder in one
direction, either in extension or retraction. To return to the normal position,
such cylinders use a spring. A single acting cylinder has a port at one end of
the cylinder for the entry and exit of the hydraulic fluid. The cylinder
housing, also called a barrel, has a piston inside that is connected with a rod.
As the fluid enters the blank end, the rod is extended outside the cylinder from
the other end, called the rod end. In a hydraulic circuit, the components are
represented such that it clearly shows the functioning of the component without
actually showing its detailed construction. This allows for easy analysis of
the hydraulic circuit. A single acting cylinder is represented similarly to
show the functioning. One drawback of the single acting cylinder is a spring that can cause mechanical problems due to spring failure. For this reason, they are
not used in applications with large stroke length.
To overcome this drawback, there is
one more type of hydraulic cylinder called a double acting cylinder. Double
acting cylinders can be actuated in both directions hydraulically. As opposed to
single acting cylinders, the double acting cylinder has two ports, one for
extension and the other for retraction. You might have noticed the single rod
in the double acting cylinder. This rod covers some area on the piston where it
is connected. Due to the reduction in area, the pressure exerted on the piston
while retracting is reduced. Such cylinders are called single rod ended type. The
imbalance of pressure during the extension and retraction can be overcome by
adding another rod on the opposite side of the piston. The two rods can now
provide two equal forces in both directions. Such cylinders are called double
rod ended cylinders.
This is only one type of classification for hydraulic
cylinders. In the next article, we will talk about classification according to
the construction of hydraulic cylinders.
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