PNEUMATICS:

Pneumatics is a branch of technology, which deals with the study and application of

use of pressurized gas to affect mechanical motion.

Pneumatic systems are extensively used in industry, where factories are commonly plumbed

with compressed air or other compressed inert gases. This is because a centrally-located and

electrically-powered compressor that powers cylinders and other pneumatic devices

through solenoid valves is often able to provide motive power in a cheaper, safer, more flexible,

and more reliable way than a large number of electric motors and actuators. Pneumatics also

has applications in dentistry, construction, mining, and other areas.

GASES USED IN PNEUMATIC SYSTEMS:

Pneumatic systems in fixed installations such as factories use compressed air

because a sustainable supply can be made by compressing atmospheric air. The air usually has

moisture removed and a small quantity of oil added at the compressor, to avoid corrosion of

mechanical components and to lubricate them.

Factory-plumbed, pneumatic-power users need not worry about poisonous leakages as the gas

is commonly just air. Smaller or stand-alone systems can use other compressed gases which

are an asphyxiation hazard, such as nitrogen - often referred to as OFN (oxygen-free nitrogen),

when supplied in cylinders.

Any compressed gas other than air is an asphyxiation hazard - including nitrogen, which makes

up 77% of air. Compressed oxygen (approx. 23% of air) would not asphyxiate, but it would be

an extreme fire hazard, so is never used in pneumatically powered devices.

Portable pneumatic tools and small vehicles such as Robot Wars machines and other hobbyist

applications are often powered by compressed carbon dioxide because containers designed to

hold it such as soda stream canisters and fire extinguishers are readily available, and the phase

change between liquid and gas makes it possible to obtain a larger volume of compressed gas

from a lighter container than compressed air would allow. Carbon dioxide is an asphyxiant and

can also be a freezing hazard when vented inappropriately.

COMPARISION TO HYDRAULICS:

Both pneumatics and hydraulics are applications of  fluid power. Pneumatics uses

an easily compressible gas such as air or a suitable pure gas, while hydraulics uses relatively

incompressible liquid media such as oil. Most industrial pneumatic applications use pressures of

about 80 to 100 psi (550 to 690 KPa). Hydraulics applications commonly use from 1,000 to

5,000 psi (6.9 to 34 MPa), but specialized applications may exceed 10,000 psi (69 MPa).

ADVANTAGES OF PNEUMATIC SYSTEM:

Simplicity of Design And Control

Machines are easily designed using standard cylinders & other components. Control is

as easy as it is simple ON - OFF type control.

Reliability

Pneumatic systems tend to have long operating lives and require very little maintenance.

Because gas is compressible, the equipment is less likely to be damaged by shock. The

gas in pneumatics absorbs excessive force, whereas the fluid of hydraulics directly

transfers force.

Storage

Compressed Gas can be stored, allowing the use of machines when electrical power is

lost.

Safety

Very low chance of fire (compared to hydraulic oil).

Machines can be designed to be overload safe.

ADVANTAGES OF HYDRAULIC SYSTEM:

Liquid (as a gas is also a 'fluid') does not absorb any of the supplied energy.

Capable of moving much higher loads and providing much higher forces due to the

incompressibility.

The hydraulic working fluid is basically incompressible, leading to a minimum

of spring action.

When hydraulic fluid flow is stopped, the slightest motion of the load releases the pressure

on the load; there is no need to "bleed off" pressurized air to release the pressure on the

load.

PNEUMATIC DOUBLE ACTING CYLINDER:

Operation diagram of a double acting cylinder

Pneumatic cylinders (sometimes known as air cylinders) are mechanical

devices which utilize the power of compressed gas to produce a force in a reciprocating linear

motion.

Like hydraulic cylinders, pneumatic cylinders use the stored potential energy of a fluid, in this

case compressed air, and convert it into kinetic energy as the air expands in an attempt to reach

atmospheric pressure. This air expansion forces a piston to move in the desired direction. The

piston is a disc or cylinder, and the piston rod transfers the force it develops to the object to be

moved.

USES OF PNEUMATIC CYLINDERS:

Pneumatic cylinders turn air pressure into linear motion. They are like automobile pistons except the piston (and connecting rod) is pushed by an influx of pressurized gas instead of a gasoline explosion. The piston must be returned to the starting position after each stroke. If a spring is used to return the piston, it is a single acting cylinder. If air pressure is used to return the piston, it is a double acting cylinder.

INDUSTRIAL USES:

Double acting pneumatic cylinders are more expensive than single acting pneumatic cylinders, but double acting cylinders are superior to single acting cylinders by any other important measure. Double acting cylinders are faster, stronger and use less energy to do the same job. In industrial applications, single acting cylinders are used if possible, but when speed or force is important, double acting cylinders are employed. Applications include opening and closing valves and doors, taking things off conveyor belts and putting things on conveyor belts. They are also used for lifting merchandise and moving merchandise around as well as for presses and punches.

ROBOTIC USES:

Pneumatic cylinders including double acting cylinders have been an important component of robots since the introduction of McKibben artificial muscles. Robotic arms move in a much more natural way if the arms are fitted with muscles resembling those of the human arm. McKibben artificial muscles consist of rubber tubes enclosed in a metal mesh. When the rubber tubes are inflated, the metal mesh expands in diameter and decrease in length--pulling the arm. Arms (both artificial and natural) really have two sets of muscles--one on the front (biceps) to decrease the joint angle and another on the back of the arm (triceps) that increases the joint angle. Because these muscles must work together, the pressures must be coordinated very quickly, so double acting cylinders are essential for supplying air to the McKibbens.

OTHER USES: Double acting cylinders are used in automobile, motorcycle, Automated Transfer Vehicle (ATV) and airplane landing gear suspensions because the bumps come so fast that a single acting cylinder would be impractical. Double acting cylinders are used in drilling, log splitters and earth moving equipment because the forces required make single acting cylinders impractical. Double acting cylinders are found in back hoes, elevators, trash compactors, garbage trucks, fork lifts, jacks and those machines in junk yards that compress old cars. They are also used in medical applications that power ventilators--those machines that help people breath. Double acting cylinders are finding increasing applications in the space program--they open and close the shuttle bay doors--because the high radiation levels in space make it important to replace electric motors with pneumatics and hydraulics. Radiation interferes with electronics but not with hydraulics or pneumatics.

DIRECTION CONTROL VALVES (DCV):

Directional control valves are one of the most fundamental parts in pneumatic

and hydraulic machinery. They allow air or fluid flow into different paths from one or more

sources. They usually consist of a piston inside a cylinder which is mechanically, electrically or

manually controlled. The movement of the cylinder restricts or permits the flow, thus it controls

the fluid flow.

Directional control valves are mainly two types:

Hydraulic

Pneumatic

Hydraulic directional control valves are for a liquid working fluid (e.g. water, hydraulic oil) and

pneumatic directional control valves are for a gaseous (usually air) working fluid.

SPECIFICATION:

They are generally specified using the number of ports and the number of switching positions. It can be represented in general form as np/ns, where np is the number of ports connected to the direction control valve and ns the number of switching positions.

PNEUMATIC DIRECTION CONTROL VALVES (DCV):

Pneumatic direction control valves can be divided into three main categories:- Two Way DCV Three Way DCV Four Way DCV

THREE WAY DCV:

A three way DCV has a pressure port P, an outlet port A and an exhaust port E. The pressure port P is connected to compressed air source and the outlet port A is connected to the actuator. The exhaust port E is directly open to the atmosphere

When the button is pressed to move the valve against the spring, the pressure port and the outlet ports are connected. So the flow will be from P to A.

When the button is not pressed, the spring causes the valve to be in the position where the outlet and exhaust ports are connected. So the flow will be from A to E.

OVERVIEW OF PNEUMATIC CAN CRUSHER:

A can crusher is basically used to smash empty aluminum cans so as to decrease the volume of waste disposal. You can save considerable amount of storage space by purchasing a can crusher. Although, there are different styles and sizes available in can crushers, the most preferred one is the pneumatic can crusher. This tool is capable of crushing a can into the smallest possible unit. These devices are commonly seen in bars, restaurants and catering halls. Even heavy drinkers keep this device in their home in order to crush cans. A pneumatic can crusher is simple to operate and ideal to crush cans. Its durability and efficiency makes it suitable for both homes and commercial environments. Even recycling centers have found these devices extremely useful. They can be easily mounted on your workbench so as to achieve a comfortable working height.

Recycling is wonderful way to help the environment, even if you think otherwise when you're hauling big, bulky bags crammed with empty cans to the curb. One device that will make your life easier, and your recycling haul much more compact, is the can crusher. Can crushers are available in a number of styles, sizes and speed, with models to suit everyone from the heavy soda drinker to the recycling center manager.

PURPOSE: The main aim of a can crusher is to smash an empty aluminum can into the smallest unit possible. Anyone who drinks a couple of sodas a week may never see the need to compact the cans, but others who are heavy drinkers may find these devices very helpful. Restaurants, bars, catering halls and recycling plants are places where a can crusher is pretty much a must.

FEATURES:

Can crushers are powered by different methods, but all share similar features. Cans are deposited or placed into a chamber outfitted with a device that crushes the cans. The device can be a disk that smashes the cans from above. A metal unit that gives the cans a two-sided force to crush them, or a massive, mechanical chamber that crushes cans on an assembly line.

PNEUMATIC:

Pneumatic can crushers work on air power, just like the first subway introduced in New York City. A hefty blast of air, usually pumped from some type of pressurized tank, will move the crushing device in a quick and exact motion and crush the can. The pneumatic tube is about the size of large, rolled-up poster. Many of these machines are homemade.

MANUAL:

Manual can crushers rely on a person's force to crush the can. Some of the manual types resemble desk-top paper-hole punchers. Instead of inserting paper into the device to punch holes in it, people insert a can and press down to crush. These table-top units are relatively inexpensive and suitable for residential use.

MOTORIZED:

Medium-sized motorized units may be functional enough for restaurants and other commercial establishments. Many of the basic motorized can crushers are a comparatively inexpensive choice. A common type allows cans to be lined up and fed into the machine, which crushes them in an internal, motorized compartment and spits out the crushed can below. Some of these crushers are about the size of a large end table and can be fairly quiet.

INDUSTRIAL:

Heavy duty can-crushing duties will work best with one of the many industrial can crushers in the market. These units can run into the thousands of dollars but are a must for any major recycling and buy-back facilities. Design particulars vary widely, but most run with a conveyor belt that feeds cans into a large, central unit and spits them out on the other end. Some include an automated washing chamber where cans are rinsed before crushing. These units have quick crushing times. Some may also be able to crush metal 5-gallon pails and smaller, aluminum car parts.

WORKING:

Pneumatic can crushers are powered by air pressure. This device is fitted with a pneumatic cylinder (pressurized tank) that pumps air with a tremendous force to set the crushing device into motion, which then falls onto the can. It can effortlessly reduce the volume of the tin to approximately 1/5th of its original size.