Leaf Spring Assembly with Guide Surface for Variable Stiffness

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Solution Overview

Problem

Leaf springs face a challenge in balancing the need for easy deformation during large displacement and maintaining a high biasing force at smaller displacements, particularly in applications like mounting devices to prevent rattling due to vibrations.

Innovation Solution

A leaf spring assembly comprising a leaf spring member and a spring support member with a guide surface that modifies the spring characteristics by allowing end region movement along the support surface, reducing the force required for displacement through a combination of bending and surface movement, enabling the use of a less flexible but more stable leaf spring member.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If the biasing force of the leaf spring is increased to maintain high force at small displacement, then the spring provides useful biasing force for preventing rattling, but the spring becomes difficult to deform and requires excessive force for large displacement during installation

Engineering Contradiction:
Improvebiasing forceVSAvoidease of deformation
Core Design Contradiction:
ForceVSEase of operation

Solution Approach 1:

The support member is divided into multiple support portions (first support portion, second support portion, third support portion) that independently define different segments of the path of movement. Each segment corresponds to a different phase of spring compression, allowing the spring characteristic to be optimized for different operational requirements.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The spring characteristic is made dynamic by using a guide surface with varying geometry. As the end region moves along the curved path defined by the guide surface, the effective spring stiffness changes continuously - providing higher force at small displacements and lower force at large displacements, automatically adapting to the operational needs.

Inventive Principle:
Principle #15Dynamics

2Ease of operation

If a more flexible leaf spring member is used to facilitate easy deformation during large displacement, then the spring can be easily installed, but the stability of the leaf spring assembly deteriorates and cannot effectively prevent rattling

Engineering Contradiction:
Improveease of installationVSAvoidstability
Core Design Contradiction:
Ease of operationVSStability of the object's composition

Solution Approach 1:

The spring characteristic parameters are changed along the path of movement through the guide surface design. The guide surface geometry is specifically configured to provide different effective spring rates at different positions, allowing a single leaf spring member with fixed properties to exhibit variable characteristics that satisfy both installation and stability requirements.

Inventive Principle:
Principle #35Parameter changes

3Length of moving object

If the leaf spring undergoes large displacement during installation, then the spring can accommodate mounting requirements, but the force required for compression becomes excessively high making installation difficult

Engineering Contradiction:
ImprovedisplacementVSAvoidcompression force
Core Design Contradiction:
Length of moving objectVSForce

Solution Approach 1:

The support member introduces a new dimensional aspect by using a curved guide surface that redirects the movement path. Instead of purely vertical compression, the end region follows a curved trajectory, allowing part of the displacement to occur along the guide surface, which reduces the direct compressive force required.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

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 allows for a balanced spring characteristic that facilitates easy installation and secure holding of devices, reducing the force needed for large displacement while maintaining stability and preventing rattling at smaller displacements.

Implementation Method 1

the guide surface is configured to vary a spring characteristic of the assembly along the path of movement

Methodology Applied
Scientific EffectFriction: Friction

Implementation Method 2

the leaf spring member has a curved elongate form which extends in a longitudinal direction x between a first end a and a second end b supported on a surface S. Upon application of a load force F, the curved leaf spring L is compressed towards the supporting surface S with the central portion c undergoing a displacement d

Methodology Applied
Scientific EffectElasticity: Elasticity

Data Source

PatentEP3260725B1Leaf spring assembly
Publication Date: 2019.05.08 CONTINENTAL AUTOMOTIVE GMBH
  • EP3260725B1 patent drawingFigure 1
  • EP3260725B1 patent drawingFigure 2~4
  • EP3260725B1 patent drawingFigure 5~7

AI summary

The present invention provides a leaf spring assembly (10), comprising: a leaf spring member (1) and a spring support member (2) which supports the leaf spring member (1). The leaf spring member (1) includes a first end region (1a), a second end region (1b), and a loading region (1c) located between the first end region (1a) and the second end region (1b) which is configured for displacement in a direction (y) under loading. The spring support member (2) includes a first support portion (3) for contact with the first end region (1a) of the leaf spring member (1) and a second support portion (4) for contact with the second end region (1b) of the leaf spring member (1). At least one of the first support portion (3) and the second support portion (4) of the support member (2) provides a guide surface (5) which defines a path of movement (P) of the respective end region (la, 1b) during loading of the leaf spring member (1), and the guide surface (5) is configured to vary a spring characteristic of the assembly (10) along the path of movement (P).