Leaf Spring Width Profile for Constant Stress Distribution

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Solution Overview

Problem

Existing leaf springs for commercial vehicles face challenges in achieving a constant stress distribution in the main stress area while minimizing weight and maintaining structural integrity, as reducing the width of the main stress area affects stress distribution and increases weight, which is undesirable for fuel efficiency and material savings.

Innovation Solution

A spring leaf design with a transition area between the main stress area and the clamping area, where the thickness decreases from the clamping area to the main stress area with a constant width, and the width of the main stress area decreases quadratically from the clamping area to the end section, ensuring a substantially constant stress distribution under uniaxial, vertical loading.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If the width of the main stress area is reduced from the clamping area to the end section to save material and weight, then weight and material usage are reduced, but the stress distribution in the main stress area is adversely affected

Engineering Contradiction:
Improveleaf spring weightVSAvoidstress distribution in main stress area
Core Design Contradiction:
Weight of moving objectVSStress or pressure

Solution Approach 1:

The patent applies local quality by differentiating the width profile in different regions of the main stress area. Specifically, a first region has a reduced width to save material, while a second region maintains a larger width to ensure proper stress distribution. This localized differentiation allows weight reduction in non-critical areas while maintaining structural integrity in stress-critical areas, resolving the contradiction between weight reduction and stress distribution.

Inventive Principle:
Principle #3Local quality

2Area of stationary object

If the width of the main stress area is reduced to create installation space in the wheel suspension area, then additional installation space is available, but the stress distribution and structural integrity are compromised

Engineering Contradiction:
Improveinstallation space in wheel suspension areaVSAvoidstructural integrity of leaf spring
Core Design Contradiction:
Area of stationary objectVSStrength

Solution Approach 1:

The patent applies local quality by differentiating the width profile in different regions of the main stress area. Specifically, a first region has a reduced width to save material

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent segments the main stress area into distinct regions with different width characteristics. The first region has a reduced width profile to create installation space, while the second region maintains adequate width to preserve structural integrity. This segmentation allows the leaf spring to fulfill both space-saving and strength requirements simultaneously.

Inventive Principle:
Principle #1Segmentation

3Stress or pressure

If the thickness decreases parabolically from the clamping zone to the end section to achieve constant stress distribution, then constant stress distribution is achieved, but the leaf spring becomes relatively heavy

Engineering Contradiction:
Improveconstant stress distribution in main stress zoneVSAvoidleaf spring weight
Core Design Contradiction:
Stress or pressureVSWeight of moving object

Solution Approach 1:

The patent combines parabolic thickness reduction with localized width reduction in specific regions. This allows the leaf spring to achieve constant stress distribution through parabolic thickness variation while reducing weight by narrowing the width in non-critical regions, thus resolving the contradiction between stress distribution and weight.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent segments the leaf spring into regions with different geometric characteristics. The parabolic thickness reduction is applied throughout the main stress area to ensure constant stress distribution, while width reduction is applied selectively in specific regions to reduce weight, achieving both objectives simultaneously.

Inventive Principle:
Principle #1Segmentation

Data Source

PatentEP3612748B1Spring blade for a leaf spring
Publication Date: 2023.08.02 HENDRICKSON COMML VEHICLE SYST EURO GMBH
  • EP3612748B1 patent drawingFigure 1~4
  • EP3612748B1 patent drawingFigure 5~6

AI summary

The invention relates to a spring leaf for a leaf spring having a top side (13), a bottom side, two side sections extending between the top side (13) and the bottom side, a longitudinal axis (15), a sectional plane (III) extending perpendicularly to the top side (13) and the bottom side and through the longitudinal axis (15), two end sections (3a) and a center section extending between the end sections (3a). The center section has a clamping region (5). Between at least one of the end sections (3a) and the clamping region (5), a main stress region (6a) is provided, the thickness of which decreases, in particular parabolically, in the direction from the clamping region (5) to the end section (3a). The width (B) of the main stress region (6a), extending between the sectional plane (III) and a side section of the spring leaf, increases according to a quadratic function over part of the length of the main stress region or over the entire length of the main stress region in the direction from the end section (3a) to the clamping region (5).