Hydraulic Actuators or Drive (Pneumatics Actuators)

The fluid discharged by the pump is directed to the ‘hydraulic actuator’.Theactuatorconvertthepressureenergyofthefluid into mechanical energy. There are 3 basic type of hydraulic actuator.
• Theactuatorsconvertthefluidpressuretoasuitablelinearor rotary motion.
• Linearmotion–Hydrauliccylinder
• Rotary motion – Hydro motor
• Rotarymotion–Semi-rotaryactuator

1. Mohammad Azam Khan
HYDRAULIC
ACTUATORS
Actuators 1

2. Mohammad Azam Khan
HYDRAULIC ACTUATORS
Actuators 2
•The fluid discharged by the pump is directed to the ‘hydraulic
actuator’. The actuator convert the pressure energy of the fluid into
mechanical energy. There are 3 basic type of hydraulic actuator.
•The actuators convert the fluid pressure to a suitable linear or rotary
motion.
•Linear motion –Hydraulic cylinder
•Rotary motion –Hydro motor
•Rotary motion –Semi-rotary actuator

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HYDRAULIC CYLINDERS
•Ahydrauliccylinderisadevice,whichconvertsfluidpowerinto
linearmechanicalforceandmotion.Itusuallyconsistsofamovable
element,apistonandapistonrodoperatingwithinacylindrical
bore.
Actuators 3

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PARTS OF A HYDRAULIC
CYLINDER
•A hydraulic cylinder consists of the following parts
•Cylinder barrel
•Piston
•Piston rod
•Bush
•Cylinder head and cap
Actuators 4

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TYPE OF HYDRAULIC
CYLINDER
Hydraulic
cylinder
Single acting
cylinders
Double acting
cylinders
Actuators 5

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SINGLE ACTINGCYLINDER
•In the case of a single acting cylinder, only the piston side is pressurized
with hydraulic fluid. The cylinder can thus carry out work only in one
direction.
•The fluid which flows into the piston chamber causes a pressure to build
up the surface of the piston.
•The piston travels into its forward end position. The return stroke is
effected by a spring, the dead weight of the piston rod or an external
load
Actuators 6

7. SINGLE ACTINGCYLINDER.
Actuators Mohammad Azam Khan
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PLUNGER TYPE SINGLE
ACTING CYLINDER
•In the case of plunger cylinders, the piston and
rod form a single component.
•Due to the design of the cylinder, the return
stroke can only be effected by external forces.
The cylinders can therefore generally be
installed only vertically.
Actuators 8

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PLUNGER TYPE SINGLE
ACTING CYLINDER
Actuators 9

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PLUNGER TYPE SINGLE
ACTING CYLINDER
Actuators 10

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APPLICATION OF SINGLE
ACTING CYLINDER
Actuators 11

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DOUBLE ACTING CYLINDERS
•Inthecaseofdoubleactingcylinders,bothpistonsurfacescanbe
pressurized.Aworkingmovementcanthusbeperformedinboth
directions.
•With double acting cylinders with a single-sided piston rod, different
forces and speeds are obtained on the advance and return strokes due
to the difference in area between the piston surface and annular
piston surface.
Actuators 12

13. DOUBLE ACTING CYLINDERS
Actuators Mohammad Azam Khan
101

14. APPLICATION OF DOUBLE ACTING
CYLINDERS
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DOUBLE ACTING CYLINDER WITH
END POSITION CUSHIONING
•Cylinder with end position cushioning are used to brake high stroke speeds
smoothly and prevent hard impacts at the end of the stroke. Shortly before
the end position is reached, the cross-section for the outflow of fluid is
reduced by the built-in cushioning pistons and then finally closed. The
hydraulic fluid is then forced to escape through a flow control valve.
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CUSHIONING CYLINDER
Actuators 16

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END POSITION CUSHIONING
•The piston is a short distance
before its end position; the
hydraulic fluid on the piston-rod
side must escape via the
adjustable flow control valve
above the piston rod
•This type of end position
cushioning is used for stroke
speed between 6 m/min and 20
m/min. At higher speed,
additional cushioning or braking
devices must be used
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END POSITION CUSHIONING
•The piston rod is on its return stroke;
in this flow direction, the non-return
valve below the piston rod is
opened, thus by-passing the flow
control valve. The piston rod retracts
at maximum speed.
Actuators 18

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DOUBLE-ACTING CYLINDER
WITH CUSHIONING
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TELESCOPICCYLINDER
Actuators 20
•Oftencylinder&rodlengthdoesnotfitinthemachine.Inthatcase
thepistonrodisalsousedasapistonbarrelandasecondpistonrodis
used.
•Thesekindsofcylindersarecalledtelescopiccylinders.Ifwecalla
normalrodcylindersinglestage,telescopiccylindersaremulti-stage
unitsoftwo,three,four,fiveormorestages.
•Ingeneraltelescopiccylindersaremuchmoreexpensivethannormal
cylinders.Mosttelescopiccylindersaresingleacting(push).Double
actingtelescopiccylindersmustbespeciallydesignedand
manufactured.

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TELESCOPICCYLINDER
Actuators 21