Dual Durometer Bonded Direct Fixation Fastener
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Bonded direct fixation fasteners (BDFFs) face challenges in maintaining vertical and lateral stiffness, leading to premature failures under cyclic loading due to uniform rubber durometer designs that compromise noise and vibration mitigation performance.
Innovation Solution
A dual durometer bonded direct fixation fastener design featuring a soft elastomer for vertical movement and a hard elastomer for lateral stability, with upturned edges encased in a continuous elastomeric component to prevent horizontal movement and extend the fastener's lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If soft rubber is used in BDFF to achieve noise and vibration mitigation, then noise and vibration reduction is improved, but lateral stiffness deteriorates leading to premature failures
Solution Approach 1:
The patent applies local quality by using different rubber durometers in different regions of the fastener. The core rubber element has lower durometer (softer) for noise and vibration mitigation, while the rubber at the upturned edges has higher durometer (harder) for lateral stability. This spatial variation in material properties resolves the contradiction between noise reduction and lateral stability.
Solution Approach 2:
The patent uses composite materials by combining rubber elements of different durometers within a single fastener structure. The multi-durometer rubber composition allows the fastener to exhibit both soft characteristics for vibration isolation and hard characteristics for lateral support, effectively resolving the performance trade-off.
2Object-affected harmful factors
If vertical stiffness is reduced for softer cushioning, then noise and vibration reduction is improved, but lateral deflection increases causing premature failures
Solution Approach 1:
The patent implements local quality by positioning softer rubber material in the vertical load path for noise and vibration mitigation, while placing harder rubber material at the upturned edges to resist lateral deflection. This localized differentiation of material properties allows independent optimization of vertical and lateral performance characteristics.
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 dual durometer design effectively reduces noise and vibration while preventing lateral deflection and extending the fastener's useful life by maintaining vertical flexibility and lateral stiffness.
Implementation Method 1
The soft elastomer achieves a desired amount of noise and vibration mitigation
Implementation Method 2
The soft elastomer will move in a vertical direction by action of the weight of a train
Implementation Method 3
the upturned edges are encased in a relatively hard elastomers. The two elastomers are bonded to the two plates, and the two rubbers are physically continuous. The soft elastomer achieves a desired amount of noise and vibration mitigation while the hard elastomer prevents lateral deflection
Data Source
AI summary
A bonded, direct fixation fastener as supportive structure for a rail on a railroad tie or bed comprising: a rail plate, wherein the rail plate has a generally horizontal center portion having a lower face and an upper face and defining a rail plate horizontal plane, and wherein the rail plate center portion extends at a first angle from opposing sides as rail plate tongues above the rail plate horizontal plane, the rail plate having a rail securing device; a bed plate comprising a generally horizontal center portion, an upper bed plate face defining a bed plate horizontal plane, and a pair of opposing bed plate tongues extending from opposing sides of the bed plate horizontal center portion disposed at a second angle above the bed plate horizontal plane; a horizontal elastomeric portion of relatively lower durometer hardness encapsulating at least a portion of the bed plate and at least a portion of the rail plate; and vertical elastomeric portions of relatively higher durometer hardness encapsulating at least a portion of each bed plate tongue and at least a portion of each rail plate tongue, and surrounding the upper face of the rail plate; and wherein each vertical elastomeric portion is physically continuous with the horizontal elastomeric portion.