Roller conveyors are classified into two groups according to the principle of conveying action.
These are:
1. Unpowered or Idle Roller Conveyor.
2. Powered or Live Roller Conveyor.
In an unpowered roller conveyor, the rollers are not driven or powered from an external source. The loads roll over the series of rollers either by manual push or push from an endless moving chain or rope fitted with pusher dogs, rods or clamps. Generally these conveyors operate at horizontal plane, but at times a gentle slope is given to these coveyors to aid motion of the loads. An inclination of 1.5% to 3% ensures that the load will roll by gravity. Such conveyors are termed “gravity roller conveyor’’.