Ribbed Elevator Rope Geometry for Stable Traction and Twist Control
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Solution Overview
Problem
Existing belt-shaped elevator ropes exhibit unstable behavior due to variations in friction coefficient over time, leading to unpredictable performance and issues with twist or sway, especially in challenging configurations.
Innovation Solution
A new belt-shaped rope design featuring elongated ribs with arcuate cross-sectional profiles and acute angles, combined with a polymer surface material of Shore A hardness between 85 and 100, to maintain a stable friction bandwidth and prevent twist, along with a rope wheel structure that complements these features for improved guidance and traction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rope uses soft material with planar ribs at large angles, then the rope can provide good initial friction contact, but the friction coefficient varies over time causing unstable behavior
Solution Approach 1:
The patent changes the material parameter from soft to hard (Shore A hardness more than 85 and less than 100) and changes the geometric parameter from planar to arcuate cross-sectional profile with acute angles. These parameter changes ensure that the friction coefficient remains stable throughout the rope's service life, eliminating the instability caused by wear in soft materials.
Solution Approach 2:
The patent uses a composite structure combining hard surface material (polymer with Shore A hardness 85-100) with the rope's load-bearing core. This composite approach allows the surface to maintain stable friction characteristics while the core provides structural integrity, resolving the contradiction between initial friction performance and long-term stability.
2Reliability
If the rope has planar ribs with large angles, then the rope can engage with rope wheels, but the rope exhibits twist and sway in challenging configurations
Solution Approach 1:
The patent replaces planar rib surfaces with arcuate cross-sectional profiles. The curved surfaces provide more stable engagement with rope wheels and reduce the tendency for the rope to twist or sway, particularly in challenging configurations. The curvature distributes contact stresses more evenly and maintains consistent geometric interaction with the wheel ribs.
Solution Approach 2:
The patent introduces asymmetry through the acute angles formed by the arcuate profiles, where the angle between tangents at points of tangency is acute. This asymmetric geometry provides directional stability and prevents the rope from rotating or swaying during operation, improving guidance stability.
3Reliability
If the rope uses hard material with arcuate profiles and acute angles, then the friction bandwidth remains stable, but the manufacturing complexity increases
Solution Approach 1:
The patent specifies precise parameter ranges (Shore A hardness 85-100, acute angles between tangents) that balance performance requirements with manufacturability. These defined parameters provide clear manufacturing targets while ensuring the friction bandwidth remains stable throughout the rope's service life.
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
The solution stabilizes the rope's behavior throughout its lifespan, reducing the likelihood of twist and sway while maintaining effective traction, thus enhancing the reliability and efficiency of elevator operations.
Implementation Method 1
the friction coefficient of a new rope differs from the friction coefficient of an old rope, which makes the behaviour of the rope unsteady and at worst unpredictable due to sensitivity to changes of friction coefficient caused by wear in general
Implementation Method 2
Each said flank face is shaped to have an arcuate cross-sectional profile (as viewed in longitudinal direction of the rope). Said flank faces are shaped to arc from the direction of the tip of the rib towards the center of the rope steeper to such steepness that the angle defined between their tangents is acute
Data Source
AI summary
The invention relates to a belt-shaped rope of an elevator having opposite lateral sides facing in thickness direction of the rope, at least one of the lateral sides being shaped to have elongated ribs that are disposed adjacent each other in width direction of the rope and extend parallel with the longitudinal direction of the rope. Each said rib has a first flank face for contacting a flank face of a rib of a rope wheel, and a second flank face for contacting a flank face of a rib of a rope wheel. Each said first and second flank face is shaped to have an arcuate cross-sectional profile, and said first and second flank face are shaped to arc to such steepness that the angle defined between their tangents is acute, and the surface material of said flank faces has shore A hardness more than 85 and less than 100. The invention also relates to an elevator arrangement as well as to an elevator, implementing the aforementioned belt-shaped rope.