This document discusses different types of hydraulic linear actuators. It describes single-acting actuators which can extend in one direction via hydraulic pressure and retract via gravity or a spring. Double-acting actuators can extend and retract via hydraulic pressure supplied to either end of the cylinder. Common types include cylinders with piston rods on one or both sides. The document also outlines the basic components of a hydraulic system including a pump to pressurize hydraulic fluid, valves to control fluid flow, piping to transport fluid, and a cylinder where fluid pressure is converted to linear motion.

3.  Hydraulic linear actuators, as their name
implies, provide motion in a straight line.
The total movement is a finite amount
determined by the construction of the unit.
They are usually referred to as cylinders,
rams and jacks.
 Actual Basic working -

4.  1) Single Acting Actuators
 2) Double Acting Actuators
 3) Telescopic Actuators
 4)Tandem Actuators

5.  It consists of a piston inside a cylindrical housing
called barrel. On one end of the piston there is a rod,
which can reciprocate. At the opposite end, there is a
port for the entrance and exit of oil.
 Single-acting cylinders produce force in one direction
by hydraulic pressure acting on the piston.(Single-
acting cylinders can exert a force in the
extending direction only.)
 The return of the piston is not done hydraulically. In
single-acting cylinders, retraction is done either by
gravity or by a spring.
 According to the type of return, single-acting
cylinders are classified as follows:
 1) Gravity-return single-acting cylinder.
 2) Spring-return single-acting cylinder.

6.  There are two types of double-acting cylinders:
 1)Double-acting cylinder with a piston rod on one side.
2) Double-acting cylinder with a piston rod on both
sides.
 To extend the cylinder, the pump flow is sent to the blank-
end port as in The fluid from the rod-end port returns to
the reservoir. To retract the cylinder, the pump flow is
sent to the rod-end port and the fluid from the blank-end
port returns to the tank.
 A double-acting cylinder with a piston rod on both sides
is a cylinder with a rod extending from both ends. This
cylinder can be used in an application where work can be
done by both ends of the cylinder, thereby making the
cylinder more productive. Double-rod cylinders can
withstand higher side loads because they have an extra
bearing, one on each rod, to withstand the loading.

7. 1) Gravity-return single-acting cylinder. 2) Spring-return single-acting cylinder.
1)Double-acting cylinder with a piston
rod on one side
2) Double-acting cylinder with a piston
rod on both sides

8.  Hydraulic Fluid :
Hydraulic fluid must be essentially non-
compressible to be able to transmit power
instantaneously from one part of the system to
another. At the same time, it should lubricate the
moving parts to reduce friction loss and cool the
components so that the heat generated does not lead
to fire hazards. It also helps in removing the
contaminants to filter. The most common liquid used
in hydraulic systems is petroleum oil because it is only
very slightly compressible. The other desirable
property of oil is its lubricating ability.

9.  It holds the hydraulic fluid to be circulated and
allows air entrapped in the fluid to escape. This is
an important feature as the bulk modulus of the oil,
which determines the stiffness of hydraulic system,
deteriorates considerably in the presence of
entrapped air bubbles. It also helps in dissipating
heat
 3) Filter :
 The hydraulic fluid is kept clean in the system with the
help of filters and strainers. It removes minute particles
from the fluid, which can cause blocking of the orifices
of servo-valves or cause jamming of spools.

10. 3) Hydraulic Pumps :
The pump converts the mechanical energy of
its prime-mover to hydraulic energy by delivering a given quantity
of hydraulic fluid at high pressure into the system. Generically, all
pumps are divided into two categories, namely, hydrodynamic or
non-positive displacement and hydrostatic or positive
displacement. Hydraulic systems generally employ positive
displacement pumps only.
The graphical symbol for Pumps :

11.  4)An Electric Motor
 5)Valves
 6)Piping Line
 7)Maximum Pressure Relief valve
 8)Flow Control Valve
 9)Pressure Guages
 10)Piston and Cylinder
Actual working of Hydraulic Actuator:

12. - Economic
- Reliable
- Resistant to overloads
- Able to support heavy loads
Hydraulic actuators :
- Low working speed
- Hydraulic group noisy in operation
Advantages :
Dis-Advantages :
- Possible oil leakage
How Hydraulic Actuators Are made ?

13. From :- Akshay Hase