Stub Shaft Conveyor Pulley Reducing Deflection
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Solution Overview
Problem
Conveyor pulleys with small diameters face frequent failures due to limited load capacity and shaft deflection, which is costly and detrimental in unit handling operations, and existing solutions with self-aligning bearings are either costly or have limited load capacity.
Innovation Solution
The design incorporates stub shaft assemblies with inner and outer bearings, where the outboard bearing is external to the center tube, allowing for a larger diameter and reduced shaft deflection, enabling the use of higher-rated bearings even at small pulley diameters, and the ratio of distances between bearing effective load centers is optimized to reduce load and deflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If smaller diameter pulleys are used to reduce the gap between conveyor belts, then the gap is reduced and articles maintain orientation, but the load capacity of bearings is limited and shaft deflection increases leading to frequent pulley failures
Solution Approach 1:
The patent positions the outboard bearing external to the center tube, effectively moving the bearing support from an internal radial configuration to an external axial configuration. This dimensional change allows the bearing to support larger loads and reduce shaft deflection while maintaining the small pulley diameter, thus reducing gap between conveyor belts without compromising reliability
Solution Approach 2:
The outboard bearing acts as an intermediary support element between the shaft and the external environment. By introducing this intermediate bearing structure outside the center tube, the system can accommodate higher loads and reduce shaft deflection without increasing the pulley diameter, resolving the contradiction between small gap requirement and high reliability
2Reliability
If self-aligning bearings are used to accommodate shaft deflection, then shaft deflection is accommodated, but the cost is prohibitive and load capacity is limited
Solution Approach 1:
The patent divides the bearing support function into two separate bearings: an inboard bearing inside the center tube and an outboard bearing outside the center tube. This segmentation allows each bearing to be a standard, cost-effective component rather than requiring expensive self-aligning bearings, while collectively they accommodate shaft deflection and support high loads
Solution Approach 2:
The outboard bearing external to the center tube serves as an intermediary that absorbs shaft deflection and accommodates misalignment. This intermediary bearing allows the use of standard, cost-effective bearings instead of expensive self-aligning bearings, while still providing the necessary deflection accommodation and high load capacity
3Force
If higher rated bearings are used to increase load capacity, then load capacity increases, but shaft deflection increases leading to frequent pulley failures
Solution Approach 1:
By positioning the outboard bearing external to the center tube, the patent creates a longer bearing support span in the axial direction. This dimensional change allows higher rated bearings to be used with reduced shaft deflection, as the external bearing position provides better structural support and reduces the bending moment on the shaft, thereby increasing load capacity without compromising reliability
Data Source
AI summary
Stub shaft conveyor pulleys that may be used as a tail pulley and/or head pulley in a belt conveyor system are disclosed. The conveyor pulley includes first and second stub shaft assemblies connected to a center tube. Each stub shaft assembly includes an inner bearing and an outer bearing. In some embodiments, the outer bearing has a diameter larger than the inner bearing. Alternatively or in addition, the inner bearing may be within the center tube and the outer bearing may be exterior to the center tube.