# Hydraulic Cylinders Actuators

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Hydraulic Cylinders Actuators
Pedro Castro ECE 5320 Mechatronics Assignment #1

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

Introduction The term hydraulics is 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 is associated 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 Pascal’s Principle which states that the pressure applied to a confined fluid increases the pressure throughout by the same amount.

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.

Common Hydraulic Cylinders
As we know, hydraulic cylinders cause linear action from pressure pushing against piston in a cylinder. There are two common hydraulic cylinders: Single acting: Fluid may only enter the cylinder from one side, therefore can only push the cylinder in one direction. Springs are commonly used to return the cylinder to the original form when the pressure is leased. Double acting: Fluid may enter the cylinder from either side of the piston, allowing control to move the piston under pressure in either direction.

Operating Specifications
Important operating specifications for hydraulic cylinders include: -The cylinder type -Stroke -Maximum operating pressure -Bore diameter -Rod diameter

The cylinder type Choices for cylinder type include tie-rod, welded, and ram.  A tie-rod cylinder is a hydraulic cylinder that uses one or more tie-rods to provide additional stability.  Tie-rods are typically installed on the outside diameter of the cylinder housing.  In many applications, the cylinder tie-rod bears the majority of the applied load.  A welded cylinder is a smooth hydraulic cylinder that uses a heavy-duty welded cylinder housing to provide stability.  A ram cylinder is a type of hydraulic cylinder that acts as a ram.  A hydraulic ram is a device in which the cross-sectional area of the piston rod is more than one-half the cross-sectional area of the moving component.  Hydraulic rams are primarily used to push rather than pull, and are most commonly used in high pressure applications.

Maximum operating pressure
Stroke Stroke is the distance that the piston travels through the cylinder. Hydraulic cylinders can have a variety of stroke lengths, from fractions of an inch to many feet.  Maximum operating pressure The maximum operating pressure is the maximum working pressure the cylinder can sustain.  Bore diameter The bore diameter refers to the diameter at the cylinder bore Rod diameter The rod diameter refers to the diameter of the rod or piston used in the cylinder.

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/5 and check whether the forces developed by the cylinders correspond to the force required.

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 working pressure -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).

Choices for cylinder configuration
Choices for cylinder configuration are simple configuration or telescopic figuration.  A simple configuration hydraulic cylinder consists of a single cylindrical housing and internal components.  A telescopic configuration hydraulic 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.

Hydraulic cylinders can be single action or double action.
A single action hydraulic cylinder is pressurized for motion in only one direction.  A double action hydraulic 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

Schematic (http://web.umr.edu/~liou/ME459/Actuators/AC_table2.htm)

Schematic Description
1 - CYLINDER HEAD 20 - Cushion and bleeder adjustment screw Nut with seal 2 - ROD GUIDE CARTRIDGE 22 - Scraper ring 23 - Guide bush 24 - Rod seal 25 - O-Ring 3 - TUBE 4 - ROD 5 - CYLINDER CAP 20 - Cushion and bleeder adjustment screw 21 - 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 bush 28 - 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

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 and space 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.