Escalator Handrail Joint Stiffness Control
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Solution Overview
Problem
The bonding of a rectangular patch cloth to the joint section of an endless escalator handrail leads to localized stiffness changes, causing stress concentration and eventual separation and breakage due to positive and negative bending during operation.
Innovation Solution
A thermoplastic resin member with curved portions and a flat woven fabric is used, with patch cloths having divergent and base portions bonded to the inner surface of the curved portions to distribute stress evenly and prevent separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rectangular patch cloth is bonded to cover the entire canvas surface of the joint section, then the strength and protection of the joint section is improved, but the stiffness of the joint section becomes extremely higher compared to the base body portion
Solution Approach 1:
The patent applies local quality by making the patch cloth non-uniform in thickness, with a thicker base portion at the center and thinner divergent portions at the edges. This creates varying local stiffness: the base portion provides strength where needed, while the thinner divergent portions reduce stiffness concentration at the bonding interface, preventing stress concentration and separation.
2Reliability
If a rectangular patch cloth is bonded to cover the entire canvas surface of the joint section, then the protection of joined edges is improved, but stress concentrates locally at the bonding interface when the handrail is bent
Solution Approach 1:
The patch cloth is designed with local quality variations where the base portion is thicker for protection, while the divergent portions are thinner to reduce stress concentration. This gradient in thickness distributes stress more evenly across the bonding interface during bending, preventing separation while maintaining edge protection.
Solution Approach 2:
The divergent portions of the patch cloth are designed with curved, rounded edges rather than sharp rectangular corners. This curvature prevents stress concentration at the edges by distributing the stress more evenly, eliminating the sharp corners that would act as stress concentrators during bending operations.
3Strength
If a rectangular patch cloth is bonded to the joint section, then the connection of canvas is reinforced, but separation of the patch cloth occurs in the joint section due to repeated bending
Solution Approach 1:
The patch cloth uses local quality with a thicker base portion for strong canvas connection and thinner divergent portions that flex better during repeated bending. This gradient structure maintains strong attachment where needed while allowing flexibility at the edges, preventing separation and extending the service life of the joint section.
Solution Approach 2:
The rounded, curved edges of the divergent portions eliminate sharp corners that would concentrate stress during repeated bending cycles. This curvature allows the patch cloth to flex smoothly with the handrail's bending motions, preventing fatigue-induced separation and extending the duration of reliable operation.
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
This configuration suppresses the increase in stiffness at the joint section, reducing stress concentration and preventing separation, thereby extending the life of the handrail joint section.
Implementation Method 1
joined at a joint section by melting cut ends of the member
Data Source
AI summary
The endless escalator handrail is made up of a thermoplastic resin member having a first and a second curved portions and a joint section; a flat woven fabric bonded to an inner surface of the thermoplastic resin member; a first patch cloth having a base portion and a divergent portion, for being placed on the first curved portion side in the joint section; and a second patch cloth having a base portion and a divergent portion, for being placed on the second curved portion side in the joint section. The divergent potion of the first patch cloth is bonded onto the flat woven fabric at an inward side of the first curved portion, and the divergent potion of the second patch cloth is bonded onto the flat woven fabric at an inward side of the second curved portion.