C-Shaped Elevator Safety Spring With Variable Cross-Section

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Solution Overview

Problem

Existing elevator safety springs face challenges in achieving a larger braking force without increasing material thickness, which leads to higher costs and manufacturing complexities, and require multiple tooling and configurations for different performance parameters.

Innovation Solution

A spring design featuring a cavity that extends along its length with varying cross-sectional dimensions and a C-shaped body formed from high-strength steel, using casting or three-dimensional printing, which maintains a constant moment of inertia to spring force ratio and allows for uniform material thickness, reducing weight and manufacturing complexity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If the thickness of the spring material is increased to achieve a larger braking force, then the braking force is improved, but the material cost and manufacturing difficulty increase

Engineering Contradiction:
Improvebraking forceVSAvoidmanufacturing difficulty
Core Design Contradiction:
ForceVSEase of manufacture

Solution Approach 1:

The spring cross-section is varied along its length, with thicker sections at critical locations (ends and center) and thinner sections in between. This local quality variation allows the spring to achieve the required braking force at critical points while reducing overall material usage and manufacturing complexity compared to a uniformly thick spring.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The spring design changes the geometric parameters along its length, specifically varying the cross-sectional dimensions. The cross-section transitions from a first dimension at the ends to a second dimension at the center, optimizing the distribution of material to achieve the required force characteristics without uniformly increasing thickness throughout.

Inventive Principle:
Principle #35Parameter changes

2Force

If the thickness of the spring material is increased to achieve a larger braking force, then the braking force is improved, but the material cost increases

Engineering Contradiction:
Improvebraking forceVSAvoidmaterial cost
Core Design Contradiction:
ForceVSQuantity of substance

Solution Approach 1:

The spring cross-section is varied along its length, with thicker sections at critical locations (ends and center) and thinner sections in between. This local quality variation allows the spring to achieve the required braking force at critical points while reducing overall material usage and manufacturing complexity compared to a uniformly thick spring.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The spring design changes the geometric parameters along its length, specifically varying the cross-sectional dimensions. The cross-section transitions from a first dimension at the ends to a second dimension at the center, optimizing the distribution of material to achieve the required force characteristics without uniformly increasing thickness throughout.

Inventive Principle:
Principle #35Parameter changes

3Adaptability or versatility

If a variety of spring sizes are required for different elevator safety configurations, then the performance parameters are improved, but the number of tools and manufacturing steps increase

Engineering Contradiction:
Improveperformance parametersVSAvoidnumber of tools
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The spring design incorporates a cavity that can accommodate different fill materials (such as lead, steel shot, or other density-adjusting materials). This allows a single spring geometry to be adapted for different weight and performance requirements by simply changing the fill material, reducing the need for multiple different spring sizes and the associated tooling and manufacturing steps.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The spring is designed as a composite structure with an outer shell and an internal fill material. This composite approach allows adjustment of the spring's effective weight and performance characteristics by selecting different fill materials, enabling a single spring design to serve multiple performance configurations without requiring multiple different spring geometries.

Inventive Principle:
Principle #40Composite materials

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 new spring design achieves a desired spring performance with reduced material cost and manufacturing complexity, providing a lighter weight and efficient braking force while maintaining uniform deflection and force characteristics.

Implementation Method 1

a curved shaped body that has a C-shape and the spring exerts a spring force toward an inside of the C-shape

Methodology Applied
Scientific EffectElasticity: Elasticity

Data Source

PatentEP3508749B1Elevator safety device with a light weight c-shaped spring
Publication Date: 2021.03.10 OTIS ELEVATOR CO
  • EP3508749B1 patent drawingFigure 1
  • EP3508749B1 patent drawingFigure 2
  • EP3508749B1 patent drawingFigure 3~5

AI summary

An illustrative example spring includes a curved shape body having a length. The body includes a cavity that extends along at least a majority of the length. The body has a cross-section across the length that is different at a plurality of locations on the body along the length.