Staggered Joint Configuration for Load Bearing Assemblies
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Solution Overview
Problem
Existing load bearing assemblies for elevator systems and passenger conveyors face challenges in joining ends to form a loop, as current joint configurations either increase stiffness, reducing flexibility, or compromise strength, making it difficult to accurately test bending fatigue and meet performance requirements.
Innovation Solution
The proposed solution involves a staggered discontinuity pattern in tension members with stress relieving features such as supplemental tension members or gaps, which distribute load more evenly and maintain flexibility, allowing for improved joint strength and reduced bending fatigue testing challenges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an overlapping joint is used to join ends of tension members, then the joint provides structural connection, but the stiffness of the assembly increases significantly in the joint area, reducing flexibility and introducing additional bending fatigue
Solution Approach 1:
The joint is divided into multiple discrete connection points rather than a continuous overlapping section. Individual tension members are joined at separate locations along the assembly, creating segmented joints that maintain flexibility while providing structural connection.
Solution Approach 2:
The joint configuration creates different local properties along the assembly - areas with joints have connection strength, while areas between joints maintain the original flexible characteristics of the tension members.
2Ease of operation
If an overlapping joint is used to join ends of tension members, then the joint provides structural connection, but the strength is insufficient to meet the needs of some situations
Solution Approach 1:
Multiple joining methods are combined within the joint configuration - mechanical interlocking, adhesive bonding, and friction-based connections work together to achieve both flexibility and sufficient strength.
Solution Approach 2:
The joint uses composite construction with different materials (e.g., polymer jacket, metal fasteners, adhesive layers) working together to provide both flexibility and strength properties that single materials cannot achieve alone.
3Productivity
If a reciprocating bending fatigue tester is used to test load bearing assemblies, then bend cycles can be accumulated quickly, but the machine requires significant reciprocating mass and is limited in speed and ability to provide consistent fatigue conditions
Solution Approach 1:
Instead of using a complex reciprocating machine to accelerate testing, the invention inverts the approach by designing the joint and assembly to naturally withstand and distribute fatigue loads, allowing simpler testing methods to achieve reliable results.
Solution Approach 2:
The staggered joint configuration allows continuous load distribution along the assembly, enabling steady-state testing conditions that maintain consistent fatigue loading without the need for complex reciprocating mechanisms.
4Ease of operation
If tension members are cut in an interlocking fingers arrangement, then the joint does not have additional stiffness, but the strength decreases to about fifty percent of the strength of the tension members
Solution Approach 1:
One tension member is nested within or alongside another at the joint location, with the staggered configuration allowing inner and outer members to work together, maintaining both flexibility and strength through layered construction.
Data Source
AI summary
A load bearing assembly (20) includes a plurality of tension members (22). A joint in the load bearing assembly (20) has a staggered pattern of discontinuities (30) in the tension members (22). A stress relieving feature is associated with at least outermost tension members (22A, 22L) in the vicinity of the discontinuities. One example includes supplemental tension members (32, 50) as the stress relieving feature. Another example includes selected spacings (32′, 40, 42) between ends of at least some of the tension members. One example includes different sized tension members as the stress relieving feature. Another example includes different lateral spacings between selected tension members.