Amphibious Vehicle Caterpillar Track Suspension Leaf Springs
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Solution Overview
Problem
Amphibious vehicles with caterpillar tracks face user comfort issues due to unsuspended rigid track layer assemblies, which detract from comfort and mechanical performance, with previous solutions using steel and fiber-glass-reinforced epoxy resin leaf springs proving unsuccessful.
Innovation Solution
The use of a suspension system with pairs of curved flexible leaf springs made of heat-hardening resin reinforced with glass fibers, where the upper leaf spring is stiffer and the lower leaf spring is longer and more flexible, connected via an elastomer layer and secured to the roller shafts and chassis, providing a non-linear stiffness and retarding effect to prevent premature breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If rigid track layer assemblies are used, then structural strength and simplicity are improved, but user comfort deteriorates
Solution Approach 1:
The patent replaces rigid track layer assemblies with flexible leaf springs that can bend and absorb shocks. The leaf springs are made of elastomeric material that provides both flexibility and structural integrity, allowing the vehicle to maintain strength while improving comfort by reducing vibrations and impacts transmitted to the vehicle body.
Solution Approach 2:
The patent changes the mechanical parameters of the suspension system by using leaf springs with specific elastomeric properties. The elastomeric material has controlled stiffness, damping characteristics, and elasticity that allow it to filter out high-frequency vibrations while maintaining load-bearing capacity, thus improving user comfort without sacrificing structural strength.
2Ease of manufacture
If steel leaf springs are used for suspension, then ease of manufacture is improved, but reliability deteriorates due to breakage
Solution Approach 1:
The patent uses composite elastomeric materials that combine the advantages of flexibility and high breakage resistance. These elastomeric composites are engineered to have superior tensile strength and elasticity compared to traditional steel, allowing them to withstand repeated bending cycles without breaking while being easier to manufacture through molding processes rather than metal forming and assembly.
3Reliability
If fiber-glass-reinforced epoxy resin leaf springs are used, then reliability is improved, but ease of manufacture deteriorates and breakage resistance under compression is insufficient
Solution Approach 1:
The patent changes the material parameters by selecting elastomeric materials with optimized compression resistance and tensile strength ratios. These elastomeric materials are specifically chosen to perform better under compressive loads compared to fiber-glass-reinforced epoxies, while also offering superior elongation at break and energy absorption capabilities.
Solution Approach 2:
The patent employs flexible elastomeric leaf springs that can be manufactured as monolithic pieces through molding, eliminating the complexity of layering and bonding fiber-glass reinforcements. The elastomeric material inherently provides both compression and tension resistance, simplifying the manufacturing process while maintaining or improving reliability.
4Strength
If upper leaf spring is made stiffer, then assembly stiffness is improved, but reliability deteriorates due to premature breakage under compression
Solution Approach 1:
The patent applies local quality by making the upper leaf spring stiffer in terms of bending stiffness to maintain assembly stiffness, but selects elastomeric material with high compression resistance to prevent breakage. The local geometry and material properties are optimized so that the spring can be stiff where needed for structural integrity while remaining resistant to compression-induced failure through the inherent elasticity and damping of the elastomeric material.
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 configuration enhances user comfort and mechanical performance by allowing significant flexing before breakage, accommodating high mechanical loads, and preventing premature failure of the upper leaf spring, while maintaining assembly stiffness and preventing longitudinal displacement.
Implementation Method 1
The adherence of the elastomer to the leaf springs is obtained through an over-molding operation
Implementation Method 2
pairs of curved flexible leaf springs made of a heat-hardening resin—notably made of an epoxy resin reinforced with superimposed fibers, notably glass fibers
Implementation Method 3
characterized by surprising amplitudes of flexing before breakage under a load, due to a non-linear stiffness
Implementation Method 4
the stiffer upper leaf spring has compressing force exerted on it while the more-flexible lower leaf spring has an extending force exerted on it
Implementation Method 5
the stiffer upper leaf spring has compressing force exerted on it while the more-flexible lower leaf spring has an extending force exerted on it
Implementation Method 6
the elastomer located between the two leaf springs progressively compresses, and stiffness is contributed by only the lower leaf spring and the elastomer (due to its compression)
Implementation Method 7
maintaining the join between the leaf springs in the presence of longitudinal stresses and imposing the overall stiffness of the assembly, plus—in parallel—enabling a longitudinal slippage of the two leaf springs in relation to each other
Data Source
AI summary
Vehicle comprising a hull and motorised aquatic propulsion members and motorised land propulsion members, this vehicle being able to move between a navigation position and a land transport position in which it rests on sets of caterpillar tracks. Each set of caterpillar tracks (1) is equipped with an even number of rollers (7) so as to define a set of adjacent roller pairs (71, 72). The rollers (71, 72) of each pair are connected to the chassis (2) by suspension means comprising a set (12) of at least two superposed curved elastic leaves made of a fibre-reinforced thermosetting resin, namely an upper leaf (131) and a lower leaf (132), the set being fixed on the one hand to the axles (9) of the rollers (71, 72) at its respective ends and, on the other hand, to the chassis (2) in its central part, and the upper leaf (13i) and the lower leaf (132) of each of the sets of leaves (12) are joined together and covered with a layer of elastomer (14).