Helically Grooved Drum Sheaves for Zero Fleet Angle Reeling
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Solution Overview
Problem
Non-zero fleet angles in grooved single layer drum sheaves cause axial twisting and frictional wear of cables, leading to reduced service lifespan and potential catastrophic failure due to kinking, which existing solutions address by increasing the distance between the drum and pulley, conflicting with the desire for compact mechanical reeving compartments.
Innovation Solution
The groove helical angle of single layer wrap drum sheaves is modified to achieve alignment of the cable departure angle with the groove helical angle at all locations, enabling zero fleet angle over the full range of cable entrainment and distention, using numerical calculations to determine compensating groove configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the distance between the drum and pulley is increased to maintain fleet angle below 1.5 degrees, then cable wear and twisting are reduced, but the mechanical reeving compartment size increases
Solution Approach 1:
The groove helical angle is varied locally along the drum length to compensate for changing cable departure angles. Instead of using a uniform groove angle, the groove angle is adjusted at different positions along the drum to maintain zero fleet angle throughout the cable wrap range, eliminating the need for increased drum-to-pulley distance
Solution Approach 2:
The groove helical angle parameter is changed as a function of position along the drum. By modifying this geometric parameter locally, the patent achieves zero fleet angle across the full range of cable entrainment and distention, resolving the contradiction between compact design and cable protection
2Ease of operation
If a non-zero fleet angle is present during cable spooling and unspooling, then the cable can be entrained and released from the drum, but axial twisting and frictional wear occur
Solution Approach 1:
The groove angle is tailored locally at each position along the drum to match the cable departure angle at that location. This local adaptation ensures that the cable always exits the groove at zero fleet angle, preventing twisting and wear while maintaining smooth entrainment and release operations
Solution Approach 2:
The groove geometry is made dynamic in the sense that the groove angle varies continuously along the drum length to adapt to the changing cable departure angle as the drum rotates and cable is spooled or unspooled. This dynamic geometric adaptation eliminates harmful effects throughout the operational range
Data Source
AI summary
Single layer wrapped helically grooved drum sheaves with non-invariant groove helical angle are disclosed which have zero fleet angle over their entire extent, calculable for any application. These drums can be paired with pulleys rotating parallel to the drum axis, to give complete drum and pulley systems having zero fleet angle over their full range of motion. These drums can alternately be paired with non-rotating cable terminating attachments, to give complete drum and attachment systems having zero fleet angle over their full range of motion. For single layer wrapped drum and pulley cable systems as well as for single layer wrapped drum and attachment cable systems; the present invention enables complete elimination of the service lifespan reduction arising from non-zero fleet angles. Another implementation benefit is reduction in elevator mechanical compartment size using the zero fleet angle tradeoff between drum length and drum to pulley separation.