A Bend Pulley is a non-powered (idler) pulley strategically placed within a conveyor frame to change the direction of the conveyor belt's travel and to ensure proper belt wrap around the drive pulley. Its primary role is to guide and support the belt along the required path, contributing significantly to system tension and tracking stability.
Key Functions
Direction Change:
Vertical Direction: Used on the return (bottom) side of the conveyor to create a U-shape, allowing the return belt to bypass obstacles, accommodate take-up systems, or facilitate proper discharge spacing from the head pulley.
Horizontal Direction: Less common, but can be used to shift the entire conveyor path laterally.
Increase Drive Pulley Wrap Angle: When placed close to the drive pulley on the return side, it is specifically called a Snub Pulley. This configuration increases the amount of belt contact (wrap) around the drive pulley, enhancing traction and power transmission efficiency.
Facilitate Take-up Systems: Integral to gravity or screw-type take-up units. The bend pulley is mounted on the moving take-up carriage, allowing it to travel and maintain proper belt tension by adjusting its position.
Support & Alignment: Provides controlled support during a belt's change in direction, reducing stress and preventing belt sag or fold-over.
Design & Construction
Similar in construction to a return idler but built to handle higher belt tensions, a bend pulley typically consists of:
Shell/Drum: Steel tube or fabricated drum.
Shaft: Solid steel shaft, sized for the applied belt tension and bending forces.
Bearings: Heavy-duty pillow block or flange bearings.
Lagging: Often bare (smooth) steel or rubber lagged. Rubber lagging can protect the belt's underside and provide some cleaning action. It is never driven.
Mounting Brackets: Designed to attach to the conveyor frame or take-up carriage.
Key Types & Configurations
Take-up Bend Pulley: The most common type, mounted on a moving take-up frame to maintain belt tension.
Snub Pulley: Positioned specifically to increase the drive pulley's wrap angle.
Fixed Bend Pulley: Used at a designated point in the return run solely to change the belt's path, with a fixed position.
Selection & Installation Considerations
Belt Tension: Must be rated for the maximum operating and stall tensions in the system.
Belt Speed & Width: Determines pulley diameter and face width.
Angle of Bend: The degree of direction change (e.g., 5°, 15°, 45°, 90°) impacts bearing loads and shaft design.
Pulley Diameter: Critical to prevent excessive belt bending stress and fatigue. Minimum diameters are specified by belt manufacturers based on belt construction (e.g., number of ply, fabric type).
Shaft & Bearing Life: Calculations must account for combined tension loads from both incoming and outgoing belt strands.
