Elevator Sheave Plastic Outer Member Noise Reduction
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Solution Overview
Problem
Elevator systems experience noise due to strain energy buildup and release at the high surface energy interface between metal sheaves and coated steel belts, leading to undesirable noise levels.
Innovation Solution
A sheave configuration using a molded plastic outer member with metallic support, such as a tubular insert or metallic rings, and featuring dimples, bumps, or roughness elements to reduce noise, providing a lower surface energy interface and improved friction characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal sheaves with high surface energy coating are used, then structural strength and durability are improved, but noise is generated due to strain energy buildup and release at the interface
Solution Approach 1:
The sheave is constructed as a composite structure with a metal core providing structural strength and a molded plastic outer member providing low surface energy. This composite approach allows simultaneous achievement of strength requirements and noise reduction through the plastic material's lower surface energy characteristics.
Solution Approach 2:
The invention changes the surface energy parameter of the sheave interface by replacing metal coating with molded plastic material. This parameter change reduces the strain energy buildup and release that causes noise, while the metal core maintains the required structural integrity.
2Object-generated harmful factors
If molded plastic material is used for sheave outer member, then noise is reduced due to lower surface energy, but structural strength may be compromised
Solution Approach 1:
The sheave combines metal core for strength with plastic outer member for noise reduction. The composite structure allows each material to perform its optimal function - metal provides structural integrity while plastic provides low surface energy interface.
Solution Approach 2:
The sheave is divided into functional segments: a metal core segment for structural support and a plastic outer member segment for noise reduction. This segmentation allows independent optimization of each component for its specific function.
3Strength
If metallic support members are embedded in plastic material, then structural integrity is maintained, but manufacturing complexity increases
Solution Approach 1:
The manufacturing process merges the metal support member insertion and plastic molding operations into a single integrated step. The metal members are positioned in the mold cavity and the plastic is molded around them in one process, reducing overall manufacturing complexity despite the multi-material nature.
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 solution effectively reduces noise by lowering the surface energy and enhancing friction between the sheave and belt, resulting in quieter operation and potentially reduced material and weight while maintaining structural integrity.
Implementation Method 1
Due to the high surface energy of the metal surface, the tension member to sheave interface can generate noise as a result of strain energy buildup and release in the jacket
Implementation Method 2
The sheave outer member includes a sheave outer surface interactive with the tension member, the sheave outer surface including one or more dimples, bumps, ridges, slits, depressions, or roughness elements configured to inhibit noise
Data Source
AI summary
A belted elevator system (10) includes a hoistway (14) and an elevator car (12) suspended in the hoistway (14) via a suspension member (16) and drivable along the hoistway (14). The suspension member (16) is routed over a plurality of sheaves (18). A sheave (18) of the plurality of sheaves includes a shaft (36) defining a central axis of the sheave (18), the sheave (18) rotatable about the central axis. A sheave outer member (38) is operably connected to the shaft (36) and rotatable about the central axis. The sheave outer member (38) includes a sheave outer surface (44) interactive with the suspension member (16). The sheave outer member (38) is formed from a molded plastic material.