Elevator Rope Friction Stabilization via Polyurethane Resin
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Solution Overview
Problem
Conventional elevator ropes experience unstable friction coefficients due to variations with temperature and sliding velocity, leading to issues in maintaining static conditions and performing emergency stops, as well as potential strength decreases and melting from frictional heat.
Innovation Solution
A resin material is developed by adding a friction stabilizer with a melting point of 100°C to 150°C and an isocyanate compound with two or more isocyanate groups to a thermoplastic polyurethane elastomer, creating a covering layer that maintains a stable friction coefficient across various sliding velocities and temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the diameter of the rope is made smaller to reduce the sheave diameter, then the sheave size is reduced, but the maximum weight capacity of the elevator decreases due to decreased rope strength
Solution Approach 1:
The patent applies composite materials by combining steel wires twisted into strands with a polyurethane resin covering material. This composite structure allows the rope to maintain high strength through the steel core while the resin coating provides enhanced friction characteristics and protection, enabling smaller sheave diameters without compromising weight capacity.
2Volume of moving object
If the diameter of the driving sheave is made smaller, then the sheave size is reduced, but the bending fatigue life of the rope decreases
Solution Approach 1:
The polyurethane resin covering material forms a composite structure with the steel wire rope that protects against bending fatigue. The resin layer distributes stresses more evenly during bending cycles, reducing stress concentration on individual steel wires and thereby extending the bending fatigue life even when the sheave diameter is reduced.
3Device complexity
If conventional resin covering materials are used, then the rope structure is simple, but the friction coefficient varies significantly with sliding velocity and temperature
Solution Approach 1:
The patent selects specific parameters for the polyurethane resin covering material, including viscosity between 100 to 1000 Pa·s and specific compositional ratios, to optimize friction characteristics. These parameter changes ensure the friction coefficient remains stable across varying sliding velocities and temperatures while maintaining a relatively simple rope structure.
4Ease of manufacture
If conventional covering materials are used, then manufacturing is simple, but the friction coefficient cannot be secured at certain levels during emergency stops
Solution Approach 1:
The patent specifies critical parameter ranges for the polyurethane resin, including viscosity (100-1000 Pa·s) and compositional ratios, to ensure sufficient friction force during emergency stops. These parameter optimizations allow the material to maintain high friction coefficients under high-speed sliding conditions while keeping the manufacturing process relatively simple through extrusion or coating methods.
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 provides an elevator rope with a stable friction coefficient that does not depend on temperature or sliding velocity, ensuring consistent performance from static conditions to emergency stops without strength loss or melting.
Implementation Method 1
adding an isocyanate compound having two or more isocyanate groups per molecule to a thermoplastic polyurethane elastomer
Implementation Method 2
a friction stabilizer having a melting point of 100°C or more to 150°C or less
Implementation Method 3
An elevator using such rope is driven by a frictional force between a sheave and the resin material forming the outermost periphery
Implementation Method 4
viscoelastic characteristics such as dynamic viscoelasticity of the resin material are known to have velocity and temperature dependencies
Data Source
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AI summary
An elevator rope of the present invention includes: a rope main body; and a covering resin layer that covers the periphery of the rope main body and comprises a molded product of a composition for forming the covering resin layer, wherein the composition is produced by mixing a thermoplastic polyurethane elastomer, a friction stabilizer having a melting point of 100°C or more to 150 °C or less and an isocyanate compound having two or more isocyanate groups per molecule. In order to further stabilize the friction coefficient, inorganic fillers may be further mixed in the composition for forming the covering resin layer. The elevator rope of the present invention has a stable friction coefficient that does not depend on temperature or sliding velocity.