Idlers are installed on belt conveyor structures and are the main support structure for the belt conveyor between pulleys. Idlers keep the belt from sagging when loaded and, depending on their configuration, provide different types of support.
Troughing idlers: Rollers underneath the loaded belt that support the belt conveyor and its load. The troughing idler is angled toward the outside edges of the belt, causing the belt to turn upward at the edges. When loaded, the weight of the loaded belt sits down into the center of the angled rollers, creating a trough shape. The trough shape keeps the material on the belt and minimizes spillage. Troughing idlers are also called carrying idlers since they carry the belt load.
Flat idlers: Rollers that allow the belt to lie flat. Flat idlers are commonly used on belt feeders or as impact idlers. Flat idlers are sometimes called carrying idlers where they are used to carry the belt load, as in a belt feeder.
Impact idlers: Rollers placed closely together directly underneath the material feed point that provide additional structural support. The additional support protects the belt against damage as material falls from above. Impact idlers may be flat or troughing idlers.
Return idlers: Rollers underneath the return side of the belt that support the weight of the returning empty conveyor belt. Return idlers are spaced farther apart than carrying or impact idlers because the weight of the returning belt is much less than the combined belt and loaded weight on the top of the conveyor.
Training idlers guide idlers, or guidlers: Idlers pivoted at their center so that they swivel. Training idlers have vertical guide rolls that contact the edge of the belt if it is off-center. This causes the idler to pivot, steering the belt back in the opposite direction.
