Elevator Load Bearing Member with Roughened Urethane Jacket
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Solution Overview
Problem
Coated steel load bearing members in elevator systems often have urethane jackets with undesirable smooth surfaces, leading to inconsistent coefficient of friction and adhesion issues with traction sheaves, which affect traction performance.
Innovation Solution
A load bearing member with a roughened urethane jacket surface, achieved through chemical or mechanical methods such as etching, abrading, or embossing, to create a textured surface that matches the sheave roughness, thereby optimizing friction and reducing adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a smooth urethane jacket surface is used, then the coefficient of friction is lower, but adhesion increases causing undesirable friction characteristics
Solution Approach 1:
The patent applies a rough surface treatment to specific contact areas of the urethane jacket where it interfaces with the sheave. This creates localized variation in surface properties - the roughened zones reduce adhesion and friction characteristics, while other portions of the jacket maintain their original smooth properties. This resolves the contradiction by making the surface properties non-uniform, addressing the adhesion issue only where needed for traction contact.
Solution Approach 2:
The rough surface treatment is applied to the urethane jacket during the manufacturing process, before the jacket is installed on the load bearing member. This preliminary action ensures that the friction and adhesion characteristics are optimized in advance, preventing undesirable sticking behavior from occurring during operation. The surface modification is performed proactively rather than reactively.
2Ease of manufacture
If urethane material with beneficial chemical properties for extrusion is selected, then the jacket application process is improved, but the coefficient of friction may be higher or lower than desirable
Solution Approach 1:
The patent modifies the surface parameters of the urethane jacket after extrusion by applying a rough surface treatment. This changes the surface roughness parameter from smooth to rough, which directly affects the coefficient of friction between the jacket and sheave. The bulk material properties remain unchanged, maintaining the beneficial extrusion characteristics, while only the surface parameters are altered to achieve desired friction properties.
Solution Approach 2:
The patent creates a composite surface structure on the urethane jacket, combining the base urethane material with a roughened surface layer. This composite structure allows the interior bulk material to maintain properties suitable for extrusion and flexibility, while the outer surface layer provides the desired friction characteristics for sheave contact. The two layers work together to satisfy both manufacturing and performance requirements.
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 roughened surface significantly improves traction performance by adjusting the coefficient of friction and reducing adhesion, ensuring consistent and desired traction characteristics.
Implementation Method 1
the resulting coefficient of friction between the jacket and an elevator sheave surface may be higher or lower than desirable for meeting the traction requirements within the hoistway
Implementation Method 2
this smoothness can introduce undesirable adhesion between the jacket and a traction sheave
Data Source
AI summary
An elevator load bearing member assembly includes at least one roughened surface (46) on a polyurethane jacket (44). In one example, mechanical roughening is used to roughen the surface (46) after the jacket has been extruded onto tension members (42). In another example, the temperatures used for molding a jacket (44) are controlled to induce melt fracture and roughen the surface (46) during the forming process. Other examples include chemically roughening the jacket surface and using localized heating to roughen the surface. The roughened jacket surface improves friction characteristics of a load bearing member assembly.