Page 12 - ConveyorBeltMaintenanceManual2010

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INSTALLATION, MAINTENANCE & TROUBLESHOOTING GUIDE
i n s t a l l a t i o n
Return Idlers
Return idlers, being flat, provide no self-aligning influence as in the tilted troughing idlers. However, by shifting their axis with
respect to the path of the belt, the return roll can be used to provide a constant corrective effect in one direction. As in the
troughing rolls, the end of the roll toward which the belt is shifting should be moved longitudinally in the direction of return
belt travel to provide correction.
Self-aligning return rolls also should be used. These rolls are pivoted about a central pin. Pivoting of the roll about this pin
results from an off-center belt and the idler roll axis thus becomes shifted, with respect to the path of the belt, in a corrective
direction (Fig. 10).
Some return idlers are made with two rolls forming a 10-degree to 20-degree V-trough, which is effective in helping to train
the return run. The V-return idlers are only recommended for fabric belts wider than 54”. The most important criteria for belt
training is idler contact in the center. If the belt has taken a set on the trough side and V-return idlers are being used, the
center of the belt is not able to make contact with the center of the V-return idlers. A hold-down roller on the return side will
help in training the belt, as it forces the belt to lay flat on the following idlers.
Rubber-segmented disk return idlers (Fig. 11) are used for cleaning the belt and help in belt training. When one of the discs
on the edges falls off, the belt edges tend to get caught, forcing the belt to run one way and become a belt de-trainer.
Minimum of 8” of belt contact is recommended for disc return idlers.
Fig. 10
Typical Self-Aligning Return Idler
Fig. 11
Rubber Disk Return Idler