Elevator Belt With Distinct Inner Outer Cords
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Solution Overview
Problem
Elevator systems face challenges in balancing breaking strength, cord life, and torque requirements, particularly due to the limitations of wire cross-sectional areas and fatigue life, as well as uneven stress distribution across the belt when using conventional wire arrangements and sheave designs.
Innovation Solution
The elevator system employs a belt construction with inner and outer cords having distinct configurations, including varying wire diameters, strand formations, and core materials, with the outer cords optimized for reduced stress and increased flexibility to accommodate different load conditions, and sheaves with convex crowns to maintain belt alignment and balance forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If large cross-section wires are used to increase breaking strength, then breaking strength is improved, but fatigue life is reduced
Solution Approach 1:
The belt is divided into multiple cords with different wire cross-sectional areas, where inner cords use larger wires for strength and outer cords use smaller wires for fatigue resistance. This segmentation allows each region to be optimized for its specific functional requirements.
Solution Approach 2:
Different regions of the belt have different wire configurations: inner cords use larger cross-section wires for high strength where needed, while outer cords use smaller cross-section wires for better fatigue life. The jacket material properties are also differentiated locally to match the specific mechanical requirements of each cord region.
2Duration of action of moving object
If nearly equal wire cross-sectional areas are used to maximize cord life, then fatigue life is improved, but breaking strength is reduced
Solution Approach 1:
The uniform wire configuration is segmented into different wire size categories across inner and outer cords, allowing the breaking strength requirement to be met through strategic placement of larger wires in inner cords while maintaining smaller wires in outer cords for fatigue resistance.
Solution Approach 2:
The belt employs a composite construction with different wire cross-sectional areas combined with differentiated jacket material properties in different regions, creating a multi-layered structure that simultaneously achieves high breaking strength and long fatigue life.
3Ease of manufacture
If conventional wire arrangements are used without guidance features, then manufacturing simplicity is maintained, but belt alignment on sheaves is poor
Solution Approach 1:
The jacket material is given different local properties: inner cords have different jacket characteristics than outer cords, creating inherent guidance features that steer the belt into proper alignment on the sheave without complex manufacturing processes.
Solution Approach 2:
Instead of adding complex guidance features to the sheave or belt structure, the invention inverts the approach by using the jacket material's differentiated properties to provide the guidance function, simplifying the overall system while improving alignment.
4Ease of operation
If sheaves with convex crowns are used to center the belt, then belt alignment is improved, but mechanical and fatigue behavior of cords is altered
Solution Approach 1:
The cord construction is differentiated locally to compensate for the crown effect: inner cords use specific wire configurations optimized for their position, while outer cords use different configurations. This local differentiation allows the system to accommodate the sheave crown while maintaining reliable mechanical and fatigue behavior across all cords.
Data Source
AI summary
A belt for suspending and/or driving an elevator car includes a plurality of wires arranged into a plurality of cords. The plurality of cords includes one or more inner cords located at an innermost portion of the belt relative to a lateral end of the belt and one or more outer cords located laterally outboard of the one or more inner cords. The one or more outer cords have a construction distinct from the one or more inner cords. A jacket substantially retains the plurality of cords.