Aromatic Polyester Elevator Rope for Lightweight High-Rise Lifting
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Solution Overview
Problem
Existing load-bearing members for high-rise elevator systems, such as metal ropes and coated steel belts, are heavy and inflexible, making them unsuitable for efficient high-rise applications due to their weight and stiffness, while carbon fiber belts require rigid matrices that reduce flexibility.
Innovation Solution
A lifting member for elevator systems comprising a rope formed from a plurality of aromatic polyester-based fibers, coated with a UV stabilizer material, including aliphatic or polyester-based polyurethane dispersions, which also incorporates additional fibers like carbon, glass, or liquid crystal polymers, offering improved strength-to-weight ratio and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal ropes are used as load bearing members, then tensile strength is achieved, but weight and cross-section size increase
Solution Approach 1:
The patent employs composite materials by combining aromatic polyester fibers (providing tensile strength) with polyurethane coating (providing protection and flexibility). This composite structure achieves the required strength while significantly reducing weight compared to traditional metal ropes, directly resolving the contradiction between strength and weight.
Solution Approach 2:
The patent changes the material parameters from metal-based to polymer-based (aromatic polyester and polyurethane), fundamentally altering the density and strength-to-weight ratio. This parameter change enables the load bearing member to maintain adequate tensile strength while dramatically reducing weight for high-rise elevator applications.
2Strength
If coated steel belts are used, then load bearing capacity is achieved, but weight increases due to steel cords
Solution Approach 1:
The patent replaces steel cord composites with an all-polymer composite structure using aromatic polyester fibers embedded in polyurethane. This eliminates the heavy steel components while maintaining load bearing capacity through the high strength-to-weight ratio of aromatic polyester, directly addressing the weight issue with coated steel belts.
Solution Approach 2:
The patent adopts polymer materials that, while having different lifecycle characteristics than steel, provide sufficient service life for elevator applications while offering superior strength-to-weight ratios. The aromatic polyester-polyurethane composite achieves the required durability without the weight penalty of steel cords.
3Weight of moving object
If carbon fiber belts are used, then strength to weight advantage is improved, but flexibility decreases due to rigid thermoset matrix
Solution Approach 1:
The patent changes the matrix material parameter from rigid thermoset to flexible thermoplastic polyurethane. This parameter change maintains the lightweight advantage of carbon fiber-like materials (aromatic polyester) while restoring flexibility through the elastomeric properties of polyurethane, enabling the belt to bend around sheaves and pulleys effectively.
Solution Approach 2:
The patent uses a flexible polyurethane coating layer that envelops the aromatic polyester fibers, creating a flexible shell structure. This flexible outer layer allows the load bearing member to deform and bend as required in elevator systems while the inner aromatic polyester core provides the necessary strength, resolving the flexibility contradiction.
4Reliability
If rigid matrix material is used to protect carbon fiber, then protection is achieved, but belt flexibility reduces requiring larger sheaves
Solution Approach 1:
The patent employs a flexible polyurethane coating layer that serves as a protective shell around the aromatic polyester fibers. This flexible protection layer provides the necessary durability and environmental resistance while maintaining sufficient flexibility to allow the belt to operate with standard-sized sheaves, eliminating the need for oversized components.
Solution Approach 2:
The patent creates a composite structure where the polyurethane coating provides protective functions (abrasion resistance, environmental protection) while the aromatic polyester core provides structural strength. This functional differentiation within the composite allows both protection and flexibility to coexist, avoiding the rigidity problem of thermoset matrices.
Data Source
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AI summary
A lifting member for an elevator system includes a rope formed from plurality of load carrying fibers extending along a length of the lifting member. The plurality of load carrying fibers including a plurality of aromatic polyester based fibers. A coating layer at least partially encapsulates the rope. An elevator system includes a hoistway, an elevator car disposed in the hoistway and movable therein, and a lifting member operably connected to the elevator car to suspend and/or drive the elevator car along the hoistway. The lifting member includes a rope formed from plurality of load carrying fibers extending along a length of the lifting member. The plurality of load carrying fibers including a plurality of aromatic polyester based fibers. A coating layer at least partially encapsulates the rope.