Polymeric Protuberance Fastener Assembly Alignment
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Solution Overview
Problem
Existing fastener assemblies with retention elements often fail to maintain the inserted component in concentric alignment with the outer component, particularly during automated assembly processes, and may offset the shaft, making precise positioning challenging.
Innovation Solution
A fastener assembly utilizing a retention and alignment element with elongated polymeric protuberances or a polymeric coating on the inner surface of a cylindrical component, providing an interference fit and maintaining the shaft collinear with the bore's axis, which includes a method of applying a thermoplastic resin with a blowing agent to form the protuberances or coating, ensuring precise alignment and retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a retention element is used to maintain components in assembled relation, then retention is improved, but alignment precision deteriorates
Solution Approach 1:
The retention element is segmented into multiple discrete protuberances distributed around the circumference of the bore. This segmentation allows each protuberance to independently engage with the shaft, providing both retention force and alignment capability. The distributed arrangement creates multiple contact points that collectively maintain concentric alignment while securing the component.
Solution Approach 2:
The protuberances are strategically positioned at specific locations around the bore circumference rather than being uniformly distributed. This local quality approach places retention and alignment features exactly where needed to engage with the shaft geometry, optimizing both retention strength and alignment precision at critical contact zones.
2Reliability
If a retention element is used to secure the shaft, then retention is improved, but shaft offset increases
Solution Approach 1:
The protuberances are designed with asymmetric geometry, featuring different dimensions and orientations on opposite sides. This asymmetry creates a preferred engagement orientation that naturally guides the shaft into correct alignment during insertion. The asymmetric configuration prevents shaft offset by providing unequal retention forces that correct misalignment tendencies.
Solution Approach 2:
The protuberances act as intermediary elements between the bore and the shaft, mediating the interaction between these two components. Rather than direct contact between the bore surface and shaft, the protuberances serve as intermediate contact points that simultaneously provide retention and alignment functions, eliminating the need for separate retention and alignment features.
3Manufacturing precision
If protuberances are added to maintain alignment, then alignment precision is improved, but device complexity increases
Solution Approach 1:
The invention merges the retention function and alignment function into a single integrated retention element. The protuberances simultaneously provide both retention force to secure the shaft and geometric constraints to maintain alignment. This consolidation eliminates the need for separate retention rings, alignment sleeves, or positioning features that would otherwise be required.
Solution Approach 2:
The retention element with protuberances serves multiple functions: it retains the shaft in the bore, aligns the shaft concentrically, and provides mechanical engagement. This multi-functionality reduces the overall component count and structural complexity compared to using separate specialized components for each function.
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 effectively maintains the inserted component in concentric alignment, facilitating precise positioning and secure retention during storage, shipping, and assembly operations, enhancing the efficiency of automated assembly processes.
Implementation Method 1
The retention and alignment element comprises a coating of polymeric material on more than fifty percent of the circumference of the inside of the cylinder wall, the coating having a thickness sufficient to establish an interference fit with the shaft of the second component
Implementation Method 2
a method of applying a thermoplastic resin with a blowing agent to form the protuberances or coating
Data Source
Figure 1~2A
AI summary
A fastener assembly includes a retention and alignment element used in combination with a first component (10) having a cylindrical wall (11) defining a bore (13) and a second component (12) having an elongated shaft for insertion into the bore (13) of the first component (10). The retention and alignment element comprises a plurality of elongated polymeric protuberances (14), each having (i) a base (18) fixed to the cylindrical wall of the first component, (ii) a height sufficient so that together the free ends of the protuberances define a passageway that creates an interference fit with the shaft of the second component, and (iii) a length sufficient to maintain the shaft of the second component (12) generally collinear with the axis of the bore of the first component (10).