Leaf Spring Assembly Weight Reduction via Segmented Parabolic Design
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Solution Overview
Problem
Commercial vehicle leaf spring suspensions face challenges with high manufacturing costs, weight, and safety concerns due to the use of steel, while alternative materials like plastics and composites are impractical for widespread adoption due to cost and performance issues.
Innovation Solution
A leaf spring assembly comprising two identical upper parabolic leaf springs arranged side-by-side and at least one lower parabolic leaf spring, which maintains the mechanical properties of a single leaf spring while reducing weight and eliminating the need for safety systems, by optimizing the second moment of inertia and cross-sectional area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a single tapered steel leaf spring is used to reduce weight and save material, then manufacturing cost increases due to special tapered rolling machines
Solution Approach 1:
The patent divides the single tapered spring into multiple constant-thickness leaves (typically 3-5 leaves) with varying lengths. Each leaf has uniform thickness, which can be manufactured using conventional rolling machines. The leaves are stacked and clamped together to form an assembly that achieves the desired tapered profile without requiring expensive specialized manufacturing equipment.
Solution Approach 2:
The patent combines multiple constant-thickness leaves into a single assembled spring unit. The leaves are clamped together at their centers where the axle is mounted, creating a unified structural element that functions as a single spring while maintaining the benefits of constant-thickness manufacturing.
2Ease of manufacture
If built-up steel spring assemblies with multiple leaves are used to reduce cost, then weight increases
Solution Approach 1:
The patent optimizes the local properties of each leaf by using constant thickness throughout each individual leaf's length, while varying the length of each leaf in the assembly. This allows each leaf to be manufactured efficiently with uniform cross-section, and the overall assembly achieves the desired weight and performance characteristics through the strategic arrangement of leaves with different lengths.
3Strength
If single leaf springs are designed to be strong enough to withstand loads, then spring rate becomes too high for acceptable ride quality
Solution Approach 1:
The patent segments the spring into multiple leaves that can deflect independently to varying degrees. The shorter leaves near the center deflect less, while the longer leaves at the ends deflect more, creating a progressive spring rate that provides both strength for load-bearing and sufficient compliance for ride quality.
Solution Approach 2:
The patent creates a dynamic spring rate characteristic through the multi-leaf construction. As the spring deflects under load, the interaction between leaves changes, allowing the spring to be stiffer under heavy loads (providing strength) and more compliant under light loads (providing good ride quality).
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 achieves a significant weight reduction of approximately 30% without increasing spring thickness, eliminates the need for costly safety systems, and maintains the mechanical properties of a standard single leaf spring, allowing for cost-effective and efficient suspension systems.
Implementation Method 1
single-stage multi-leaf springs which are designed to mechanically dampen the movement between the frame and the axles during operation of the vehicle
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3C
AI summary
The invention relates to a vehicle suspension leaf spring assembly arranged to be mounted in the longitudinal direction of the vehicle, on both sides thereof, said leaf spring assembly having a first end (223, 224), which is arranged for pivotal connection to a first bracket (207) on the vehicle; and a second end (225, 226), which is arranged for connection to a spring shackle (210) on the vehicle, wherein said leaf spring assembly is arranged to be connected to an axle (212) extending transversely of said leaf spring assembly at a position intermediate the first and second ends of said leaf spring assembly. The leaf spring assembly comprises an upper spring arrangement comprising two individual upper leaf springs (221, 222; 404, 405; 504, 505) arranged side-by-side with a predetermined spacing and extending between said first and second ends (223, 224; 225, 226), and at least one lower spring arrangement (220; 421; 521,523) arranged below the upper leaf springs (221, 222; 404, 405; 504, 505).