Pneumatics and Control Valves Part 2

Air compressors are often called a hidden utility because not many people know about air compressors. The closest they get to an air compressor is the buzzing of air wrenches when they get their tires fitted. There are a myriad of pneumatic tools available on the market today. Cabinet and furniture shops use pneumatic nail guns and staplers, because nothing else compares to the speed and reliability of these tools. Blow off guns are the most common use for compressed air. From blowing off chips in a machine shop to a makeshift air brooms, these guns are extremely convenient tools. A blow off gun is simply a push button valve with a discharge valve to focus the escaping air. This type of gun is preferred when operators are restricted to specific machines, such as lathes, mills and punch presses.

Pneumatic energy is regulated and controlled by pneumatic valves. Functionally, valves are divided into four major groups viz, direction control, flow control, pressure control and non-return and special type valves. As per construction, valves are sub-grouped as seat valves and sliding or spool valves. However, spool valves are easier to manufacture. Valves are actuated in various methods, viz, manually, mechanically, electrically, pneumatically and by various combined mode of actuation. Specially designed valves like quick exhaust, time delay and shuttle and twin pressure valves are used to impart various functions to pneumatic circuits.

To control the to and fro motion of a pneumatic cylinder, the air energy needs to be regulated, controlled and reversed with a pre determined sequence in a pneumatic system. Similarly, one may have to control the quantity of pressure and flow rate to generate the desired level of force and speed of actuators. To achieve these functions valves are used. Valves are fluid power elements used for controlling and regulating the working medium, i.e, the compressed air in the case of a pneumatic system.

Board valves are used to start and stop pneumatic energy, control the direction of flow of compressed air, control the flow rate of compressed air and control the pressure rating of the compressed air. Direction control valves are mainly used to direct the flow of pressure fluid in the desired direction. They can be actuated to assume different positions by various actuating mediums. This results in corresponding connection or disruption of flow between various port openings. Direction control valves have two, three, four or five ports or openings.

In a direction control valve, the force is applied directly on the working piston or spool. The control method could be manual, mechanical, pneumatic, magnetic or a combination of any two. Magnets are commonly used for actuation of pneumatic valves. When the magnet is excited, the plunger gets attracted to it and it presses down on the valve spool. The pneumatic method acts on a spool or piston with a large area which in turn transfers the actuating force to the spool. Mechanical method involves the use of rollers, springs and other mechanical elements are used to actuate the valve. In the manual method the angular movement of a pedal or lever is transmitted to the spool.

Pneumatics and Control Valves Part 1

Pneumatics is a branch of mechanical engineering that deals with the use of air pressure in creating motion or some form of mechanical force. Pneumatics is used mainly in factories and industries where compressed air is dealt with. The compressed air or steam is stored in one location and distributed through valves. Compressed gases are a cheaper solution to using electric motors and actuators. Pneumatics is used because of the cheap availability of air. Air costs nothing. Compressed air can be stored and used even when electrical power is lost. The design is simple and straightforward, utilizing existing components like cylinders and pistons.

The first pneumatic tool probably was the bellows used by blacksmiths. Modern air compressors were designed in the 1800s and were used in department stores. The system was used between sections to get change. Air compressors were also used on barges and boats. These were hand operated and needed four hardy men to keep it going. The air pump was used to supply air to divers. Due to the limits of human strength high pressures could not be produced and this limited the depth the divers could go to. As steam engines began to be used, the man power was replaced by this.

Air compressors began to be used more widely in the second half of the 19th century. Compressed air was used to dig the foundations of the Brooklyn Bridge. The silt under the river was very porous and the water kept seeping into the caissons. Compressed air was used to keep out the water. Pneumatic machines gained popularity fast and industrial installations all around the country started using them. There were uncertainties on whether steam or electricity was the energy of the future. In the end electricity won out because small businesses could not afford steam systems.

The invention of the pneumatic tire called for a cheap, mass produced air pump. The hand pump was the first mass produced air pump. It became a standard part of bicycles, cars, and trucks. The hand pump was also found at garages and gas pumps. The introduction of electric motors meant businesses did not need to buy steam plants to power their compressors. The electric motor revolutionized the air pump. Air compressors could be made smaller and more inexpensive, opening out the market further. World War 2 added impetus to the air compressor development. Air compressors started to be sold in units of the pump, the motor and the receiver.

The better technology of air compressors meant that a variety of air and pneumatic tools were developed. Personal sized tools were developed to make them more affordable. Go to any auto mechanic and you will find that he uses air tools and has a compact air compressing unit. Today the air compressor is found nearly everywhere. Buildings use air compressors to operate heating, ventilation and air conditioning. If it wasn’t for air compressors very few rides in the amusement park would work.

How To Help A Pet Hit By A Car

December 31, 2008 was cold and clear when a white dog raised its head as we approached in our truck while lying in the middle of the two lane street. I asked my husband to return, and we did to protect the dog. I called my vet, found a phone number that was for emergencies, called that and found that it was the wrong county. If I had dialed 911, I would have saved valuable time. It was after 9:00 pm when we stopped.

They arrived, placed a muzzle that was too small on the dog, and used the towel I provided to load the dog, asked us some questions, and left. The dog died, but the important point is that it had a chance it would not have without Animal Control. It had no collar, no tags, and we didn’t know the dog. It was trying to bite, but did not bite anyone.

We found out that after hours 911 is the fastest way to contact the correct county Animal Control. If out of the county of residence and not online, information may help. Getting the numbers into the speed dial for local shelters is important.

Although there may not be a tax deduction, it is very helpful to donate towels, sheets and items dogs and cats can use. It is a good idea to have some of these items for emergency use while traveling.

Two other neighbors stopped to help us divert traffic while we waited for Animal Control to come help this dog. A muzzle in our car would have made the difference, although getting a muzzle on a hurt dog is not always easy. The options of taking the dog ourselves to an Emergency Clinic may save the dog, but may be out of pocket instead of paid by the county with Animal Control.

(c) Charlotte Fairchild 2008