Air conveyors are a class of material handling devices that use either positive or negative air pressure to move objects from one place to another. The most common type of air conveyor consists of pneumatic pipes containing either high positive air pressure or a vacuum. When solid objects are placed inside these pipes, they are either pushed forward by positive pressure, or sucked along by vacuum. Another type of air conveyor uses positive air pressure to reduce the friction of a surface, making it much easier to move objects over it. This is somewhat similar to an unpowered roller conveyor in that some other force, such as gravity or manual labor, must provide the necessary energy to move an object along this type of conveyor.
One type of air conveyor is typically referred to as a pneumatic tube system. These conveyor systems consist of tubes that can be used to move large objects, small parts such as nuts and bolts, and even loose powders. Some of these systems use positive pressure, which involves pushing objects through the tubes with air pressure generated by some type of compressor or blower. The pressure inside these tubes is often six or more times normal atmospheric pressure, depending on the materials the system is designed to move.
The other type of pneumatic tube conveyor systems uses vacuum instead of air pressure. In some cases the vacuum is generated at the end of the tube system, though another design involves injecting air into special collars that join lengths of tubes together. These collars contain ring-shaped plenum chambers that force compressed air into the system. The introduction of compressed air through this type of chamber creates a vacuum behind the collar, which can suck objects along, and propel them through the system.
Another category of air conveyor does not use any type of enclosed tube. These devices are sometimes referred to as air tables, and they can perform many of the same jobs that belt and roller conveyors are often used for. There are two different ways that these conveyors work, both of which involve creating a thin layer of pressurized air between the surface of the table and an object that needs to be moved. One method uses ball valves that release pressurized air when they come into contact with heavy objects, while the other makes use of a porous surface that covers a plenum chamber. Both of these methods result in an air conveyor that can allow a worker to move heavy objects with relatively little effort.