Pedro Castro A

8/13/2019 Pedro Castro A

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Hydraulic Cylinders Actuators

Pedro Castro

ECE 5320 Mechatronics

Assignment #1


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Outline

Introduction

Hydraulic Cylinder Actuator

Common Hydraulic Cylinders

Operating Specifications

Choices For Cylinder Type

Guidelines On Selecting A Cylinder

Choices for cylinder configuration

Schematic Applications


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Introduction

The termhydraulicsis defined as the science that

studies the behavior of fluids that stand still or move

(hydrostatics and hydrodynamics). However, in a

mechanical engineering sense, the term hydraulics isassociated with the area of fluid studies that are

concerned with transmitting power and force by fluid

means. Applications of power and force transmission

are primarily based on Pascals Principle which statesthat the pressure applied to a confined fluid increases

the pressure throughout by the same amount.


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Hydraulic Cylinder Actuator

Hydraulic cylinders are actuation devices that

utilize pressurized hydraulic fluid to produce linear

motion and force. Hydraulic cylinders are used in

a variety of power transfer applications. Operating

specifications, configuration or mounting,

materials of construction, and features are all

important parameters to consider when searching

for hydraulic cylinders.


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Common Hydraulic Cylinders

As we know, hydraulic cylinders cause linear action frompressure pushing against piston in a cylinder. There are twocommon hydraulic cylinders:

Single acting: Fluid may only enter the cylinder from oneside, therefore can only push the cylinder in one direction.Springs are commonly used to return the cylinder to theoriginal form when the pressure is leased.

Double acting: Fluid may enter the cylinder from eitherside of the piston, allowing control to move the piston underpressure in either direction.


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Operating Specifications

Important operating specifications for hydraulic

cylinders include:

-The cylinder type

-Stroke

-Maximum operating pressure

-Bore diameter

-Rod diameter


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The cylinder typeChoices for cylinder type include tie-rod, welded, and ram.

A tie-rod c yl inderis a hydraulic cylinder that uses one or moretie-rods to provide additional stability. Tie-rods are typicallyinstalled on the outside diameter of the cylinder housing. In manyapplications, the cylinder tie-rod bears the majority of the appliedload.

A welded cyl inderis a smooth hydraulic cylinder that uses aheavy-duty welded cylinder housing to provide stability.

A ram cylinderis a type of hydraulic cylinder that acts as a ram. Ahydraulic ram is a device in which the cross-sectional area ofthe piston rod is more than one-half the cross-sectional area of themoving component. Hydraulic rams are primarily used to pushrather than pull, and are most commonly used in high pressure

applications.


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Stroke

Stroke is the distance that the piston travels through thecylinder. Hydraulic cylinders can have a variety of stroke

lengths, from fractions of an inch to many feet.

Maximum operating pressureThe maximum operating pressure is the maximumworking pressure the cylinder can sustain.Bore diameter

The bore diameter refers to the diameter at the cylinder bore

Rod diameterThe rod diameter refers to the diameter of the rod or piston used in

the cylinder.


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Guidelines On Selecting A Cylinder

Parameters:

mass to be displaced

real cylinder force

length of displacement (stroke)

displacement time and speed (flow calculation in l/min)

Determining the cylinder bore:

When working pressure is known, refer to table on page B/5and check whether the forces developed by the cylinders

correspond to the force required.


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Selecting shock absorber/cushioning:

a cushioning system is required when the cylinder stroke is not

limited by thrust blocks and when the displacement speed exceeds

0.1 m/s.

Checking cylinder cushioning capacity:

-The energy to be absorbed must not exceed a level which might

dissipate the cylinder

-Referring to the diagrams on page B/9, the absorption capacity of

the cylinder chosen is calculated according to the workingpressure

-Dissipating energy is calculated using the formulas and indications

given in the tables on page B/8 (when the energy to be absorbed

exceeds a level likely to dissipate the cylinder, a larger bore

diameter must be used).


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Choices for cylinder configuration

Choices for cylinder configuration are simple

configuration or telescopic figuration.

A simple configurationhydraulic cylinder consists

of a single cylindrical housing and internalcomponents.

A telescopic configurationhydraulic cylinder uses

"telescoping" cylindrical housings to extend the

length of the cylinder. Telescopic configuration

cylinders are used in a variety of applications that

require the use of a long cylinder in a space-

constrained environment.


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Hydraulic cylinders can be single action or double action.

A single actionhydraulic cylinder is pressurized

for motion in only one direction.

A double actionhydraulic cylinder can move

along the horizontal (x-axis) plane, the vertical(y-axis) plane or along any other plane of motion.

Choices for mounting method include flange, trunnion,

threaded, clevis or eye, and foot. The mount location can

be cap, head, or intermediate.

Materials of construction include steel, stainless steel, and

aluminum. Common features for hydraulic cylinders

include integral sensors, double end rod, electro-hydraulic

cylinders, and adjustable stroke


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c ema c

(htt p://web.umr.edu/~l i ou/M E459/Actuators/AC_table2.htm)


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1 - CYLINDER HEAD

20 - Cushion and bleeder adjustment screw

21 - Nut with seal

2 - ROD GUIDE CARTRIDGE

22 - Scraper ring23 - Guide bush

24 - Rod seal

25 - O-Ring

3 - TUBE

4 - ROD

5 - CYLINDER CAP

20 - Cushion and bleeder adjustment screw21 - Nut with seal

6 - TIE RODS

33 - Locknuts

7 - PISTON

(In the event of static functioning, the piston can be supplied with liquid-tight seals)

26 - O-Ring

27 - Guide bush28 - Piston seal

30 - Safety screw

31 - Permanent magnet (V160C magnetic version)

8 - HEAD CUSHION BUSH

9 - CAP CUSHION BUSH

33- Circlip

10 - MAGNETIC PROXIMITY SWITCHES

Schematic Description


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Applications

Typical applications of this type of actuators are: pulling or

pushing in engineering applications such as in machine

tools,

earth moving equipments, construction equipments andspace applications.

Also, hydraulic cylinders actuators are used for all fields of

engineering that comprise of: earth moving, mining

industry, construction machinery, plant engineering,

defense technology, automotive engineering, mechanical

engineering, textile industries, railways, power plants,

agricultural machinery etc.

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