Elastomeric Bushing Geometry for Spring Rate Without Curling
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Solution Overview
Problem
Existing elastomeric bushings require additional manufacturing steps such as curling and grinding to achieve desired dimensional control and radial/axial deflection rates, increasing production costs and complexity.
Innovation Solution
An elastomeric bushing design featuring an inner sleeve with radially outwardly extending flanges and sloped surfaces, combined with an elastomeric bumper, which is compressed during assembly to provide geometric constraints and enhance radial and axial deflection rates without the need for curling or grinding processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the outer sleeve ends are curled inward to compress the elastomeric material, then the radial and axial spring rates are increased, but additional manufacturing steps (curling and grinding) are required beyond standard molding
Solution Approach 1:
The elastomeric bumper is pre-compressed during the molding process itself, before final assembly. The molding cavity is designed to compress the elastomeric material to the desired degree, eliminating the need for subsequent curling and grinding operations. This preliminary compression action achieves the required spring rates while simplifying the manufacturing process.
Solution Approach 2:
The compression of the elastomeric material and the formation of the outer sleeve are merged into a single molding operation. The elastomeric bumper is molded in a compressed state within the outer sleeve, combining what were previously separate operations (molding, curling, grinding) into one integrated process, thereby reducing manufacturing complexity.
2Strength
If the outer sleeve is deformed to curl over the ends, then the elastomeric material is compressed to increase spring rates, but additional grinding is required to qualify the outer surface dimensions
Solution Approach 1:
The outer surface of the outer sleeve is pre-formed to the correct dimensions during the initial molding process, before any compression or assembly operations. This preliminary formation of the outer surface eliminates the need for subsequent grinding operations to achieve dimensional specifications, maintaining manufacturing precision while avoiding additional processing steps.
Solution Approach 2:
Instead of deforming the outer sleeve after molding and then correcting the outer surface dimensions through grinding, the invention inverts the sequence by first forming the outer sleeve with the correct outer surface dimensions during molding, then applying compression internally without affecting the outer surface geometry. This approach maintains dimensional control while achieving the required spring rates.
3Manufacturing precision
If additional curling and grinding processes are implemented, then dimensional control and deflection rates are achieved, but production costs increase
Solution Approach 1:
Multiple manufacturing operations (molding, compression, and outer surface formation) are merged into a single injection molding process. The elastomeric bumper is molded in a compressed state within the outer sleeve, and the outer surface is formed to final dimensions all in one operation, eliminating the need for separate curling and grinding processes, thereby reducing production costs.
Solution Approach 2:
The compression of the elastomeric material and the formation of the outer surface to final dimensions are performed as preliminary actions during the molding process itself. This preliminary completion of what would otherwise require additional post-processing steps achieves dimensional control and required deflection rates while minimizing production costs by eliminating subsequent operations.
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 design achieves improved dimensional control and reduced manufacturing costs by eliminating unnecessary production steps while maintaining target deflection rates, enhancing the bushing's durability and performance.
Implementation Method 1
an elastomeric bumper disposed around and directly engaging an inner sleeve. An outer sleeve is disposed around the inner sleeve and the elastomeric bumper
Implementation Method 2
first through fourth sloped surfaces extending between the neck portions and the flanges as well as between the neck portions and the bulbous portion
Data Source
AI summary
An elastomeric bushing comprises an elastomeric bumper disposed around and directly engaging an inner sleeve. An outer sleeve is disposed around the inner sleeve and the elastomeric bumper. The inner sleeve includes radially outwardly extending first and second flanges at opposite ends. The inner sleeve includes a centralized bulbous portion with first and second neck portions positioned on opposite sides of the bulbous portion. The inner sleeve further includes first through fourth surfaces extending between the neck portions and the flanges as well as between the neck portions and the bulbous portion. A first cushion portion of the elastomeric bumper is trapped between the first and third surfaces. A second cushion portion of the elastomeric bumper is trapped between the second and fourth surfaces.