A tube conveyor is a type of enclosed material transport system. The basic design is comprised of a long tube and one of two inner conveyance systems, platforms and screws. A platform-based system has the inner workings operating on a long circuit; the platforms go through the tube and then back down to the beginning in order to come up again. A screw-style tube conveyor has a single screw that fills the inner area of the tube and doesn’t move from a fixed position. The two styles perform the same basic task, but their application is very different.
The idea behind a tube conveyor is moving material in a controlled and enclosed area. In general, the material needs to be separated from the environment for some reason. Sometimes the material is hazardous and needs a layer of separation that a typical belt doesn’t provide. In other cases, the material needs to be protected from environmental hazards, such as wind or rain. This type is especially common when the conveyance system operates outside.
There are two basic ways of constructing a tube conveyor: platform and screw. Platform conveyors have round disks connected to each other with a chain. These disks fit securely inside the tube, making the area between the platforms secure from one another. Since each compartment is separate, it is actually possible to convey different materials on the same system. The most common variant of this conveyor style features scoops rather than disks; this style does not wholly separate compartments but does have limited separation.
The biggest drawback to this conveyor style is the platforms themselves. These machines run like a standard conveyor belt; the chain and disks make a loop that runs continuously through the tube. After a platform exits one end of the system, there has to be a way of getting it back to the other end securely. As a result, many of these systems actually have two tubes, one that takes material and the other that returns the empty disks.
The other major variety of tube conveyor is the endless screw. These tubes have a single large screw that runs from one end to the other. As the screw turns, it feeds material along its teeth, slowly moving it upwards. The tube is essentially one huge compartment running in a spiral from one end to the other.
This style of tube conveyor can move material without the need to return anything to the other end, making them less bulky than a platform conveyor. On the other hand, there is no way to separate material. The conveyed material is jostled around much more than with the more stable platform system and the screw general uses quite a bit more power.