1) Power and free conveyor
A variation of overhead chain conveyor is "power and free". In a conventional overhead conveyor the carrier is permanently fastened to the drive chain, in the power and free case the carrier can mechanically disengage from the drive chain and essentially idle while the chain continues to move. Power and free conveyors can also be inverted so that they can be mounted to the floor, in which case the carrier or tray rides on top of the guiding rail as opposed to being suspended beneath it.
2) Chain conveyor
A form of powered conveyor used to transport heavy unit loads such as pallets and industrial containers. These conveyors can be single or double chain strand in configuration. This chain is not only the driving force but it is also the part which comes in direct contact with the load and provides friction which pulls the load forward. In some cases, free rollers on either side of or between the chain provide additional support to the load. Short sections of double strand chain conveyors are a common means of transferring loads at right angle to/from another straight section of roller conveyor.