Elevator Drive Sheave Tension Control via Segmented Rim Members
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Solution Overview
Problem
Elevators with high friction ropes, such as those with polymer coatings, experience significant rope force variations due to minimal slip on the drive sheave, leading to excessive fatigue on load-bearing components, reduced ride comfort, and shortened rope lifespan, particularly in systems with long travel distances, low headroom, and 2:1 suspension configurations, where prior tension equalization solutions are inadequate.
Innovation Solution
A drive machinery with a rotatable drive sheave featuring a central cylinder and multiple circular rim members, each with independent rotation control via an electrically controllable control means, allowing for precise tension adjustment between ropes passing around different rim members to mitigate tension differences generated by car position changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If high friction ropes with polymer coating are used, then grip on drive sheave is improved, but rope force variations increase due to minimal slip
Solution Approach 1:
The drive sheave is divided into multiple independent circular rim members (first, second, third, fourth rim members) that can rotate independently relative to each other and the central cylinder. This segmentation allows each rim member to be controlled separately to compensate for individual rope tension variations, resolving the contradiction between high friction grip and uniform rope force.
Solution Approach 2:
The rim members are made dynamically adjustable through independent rotation control around the central axis. The control means enable real-time adjustment of each rim member's position to compensate for changing rope tensions, transforming a static friction system into a dynamic one that can adapt to tension variations.
2Reliability
If rope tension equalization is attempted with limited range movement, then some tension balancing is achieved, but further equalization is blocked when range limit is reached
Solution Approach 1:
The rim members are designed with unlimited rotation capability relative to the central cylinder, eliminating the range limit constraint of prior solutions. The control means enable continuous adjustment of each rim member's angular position, allowing tension equalization to proceed without being blocked by mechanical range limits.
Solution Approach 2:
By segmenting the drive sheave into independently controllable rim members, the system achieves finer-grained control over tension distribution. Each rim member can be adjusted independently to compensate for local tension variations, providing more versatile and extensive tension equalization capability.
3Length of stationary object
If small diameter drive sheave is used, then space requirements are reduced, but number of rotations increases worsening travel difference accumulation
Solution Approach 1:
The drive sheave is segmented into multiple rim members that can independently rotate. This segmentation allows the system to compensate for the increased number of rotations caused by small diameter by actively adjusting each rim member's position to maintain uniform rope tension, thereby offsetting the negative effect of frequent rotations.
Solution Approach 2:
The control means monitor rope tension variations and adjust rim member positions accordingly. This feedback mechanism detects travel differences caused by the small diameter and corrects them in real-time, preventing accumulation of tension variations despite the higher rotation frequency.
4Length of moving object
If long travel distance is implemented, then service coverage is improved, but rope tension variations worsen due to accumulated travel differences
Solution Approach 1:
The independent rotation control of rim members provides continuous dynamic adjustment capability throughout the entire travel distance. As the elevator moves, the control system actively compensates for tension variations at any position, enabling long travel distances without sacrificing rope tension uniformity.
Solution Approach 2:
The segmented rim member design allows distributed control of tension throughout the rope length. Each rim member can be independently adjusted to compensate for tension variations caused by long travel, effectively managing the contradiction between extended service coverage and tension uniformity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively reduces rope tension variations, alleviates fatigue on components, enhances ride comfort, and extends rope lifespan, even in challenging configurations like long travel distances and low headroom scenarios, by enabling precise control of tension differences across the elevator system.
Implementation Method 1
high friction ropes, such as ropes having a polymer coating, are easily subjected to large force variations due to their small slip on the drive sheave
Data Source
AI summary
The invention relates to an a drive machinery for an elevator, the drive machinery comprising a rotatable drive sheave for driving plurality of ropes of the elevator, the drive sheave comprising a central cylinder, which comprises a central axis around which the central cylinder is rotatable; plurality of circular rim members surrounding the central cylinder, each said rim member comprising an outer rim surface for engaging a rope. Said plurality of circular rim members includes one or more rotatably mounted circular rim members, each said rotatably mounted circular rim member being mounted on the central cylinder rotatably around said central axis relative to the central cylinder and relative to one or more of the other circular rim members, and in that said drive sheave moreover comprises a control means for controlling rotation of each said rotatably mounted circular rim member relative to the central cylinder and relative to one or more of the other circular rim members. The invention also relates to an elevator implementing the drive machinery.