Machine Design

Pulley keeps flat belts on track

Keeping conveyor belts in the proper position while they are moving can be difficult.

Differential heating, intermittent heating, and even belt wear causes belts to get off course. To ease matters, Belt Technologies, Agawam, Mass., makes an Independently Steerable Pulley (ISP) which can be used with conveyor systems (with the ISP being the idler or driven pulley), multiple-idlers on a common shaft, and systems with serpentine or other complex belt paths. It consists of a steering collar, sealed bearings, servomotor, and a pulley. The steering collar features either a skewed, or offset, bore. Sensors detect when the belt edge is improperly positioned and signal the servomotor, which holds a dead shaft in place for the idler pulley. The shaft runs through the steering collar, which has an angle bored into it so the collar is not at 90° to the shaft. When the servo moves, it changes the angle in the collar, which transfers the movement through the bearing to the pulley face. This change in the pulley face modifies the tension on each side of the belt, causing it to move laterally across the pulley face. This is all done while the conveyor is moving, so equipment need not be shut down to adjust belt tracking.

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