Swaged Collar Fastener for High Clamp Load and Easy Removal
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Solution Overview
Problem
Conventional fasteners require specialized tools for collar removal, leading to plastic deformation and damage, and there is a need for improved control over their assembly and reusability.
Innovation Solution
A fastener design with a stud and collar where the bore diameter is significantly larger than the shaft diameter, allowing for high residual clamp load, improved thermal management, and easy removal without cutting or specialized tools, featuring a drive portion for unscrewing and a conical shape for easy installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the collar is hardened during installation to provide high tensile strength, then the strength of the fastener is improved, but the force required for collar removal increases causing plastic deformation and damage
Solution Approach 1:
The collar is divided into two distinct portions: a main portion that is hardened and swaged onto the shaft for high strength, and a drive portion that remains softer and can be easily removed. This segmentation allows each portion to have optimized properties for its specific function.
Solution Approach 2:
Different portions of the collar have different material properties - the main portion is hardened for strength while the drive portion remains softer for ease of removal. This local differentiation of material properties resolves the contradiction between strength and removability.
2Ease of repair
If a specialized removal tool is used to cut the hardened collar, then the collar can be removed, but the device complexity and tooling requirements increase
Solution Approach 1:
By segmenting the collar into a removable drive portion and a permanent main portion, the design eliminates the need for complex cutting tools. The drive portion can be unscrewed using simple rotational force, avoiding the need for specialized removal equipment.
Solution Approach 2:
The drive portion is designed as a disposable component that can be easily removed and replaced without requiring expensive specialized tools. This approach trades the cost of complex tooling for the cost of a simple replaceable collar portion.
3Reliability
If the bore diameter is made significantly larger than the shaft diameter, then the residual clamp load and resistance to thermal expansion are improved, but the installation force required increases
Solution Approach 1:
The installation process uses a controlled swaging operation that dynamically applies force to deform the collar onto the shaft. The conical interface allows progressive deformation that achieves high clamp load while controlling the peak installation force through the deformation process.
Solution Approach 2:
The conical interface geometry changes the stress distribution during installation, allowing the collar to be deformed onto the shaft with controlled force. The cone angle and taper ratio are optimized to achieve high residual clamp load while managing installation force requirements.
4Reliability
If the collar is swaged onto the locking portion to provide high clamp load, then the fastening reliability is improved, but the collar becomes difficult or impossible to remove without cutting
Solution Approach 1:
The collar is segmented into a swaged main portion that provides reliable fastening and a separate drive portion that can be unscrewed for removal. This allows the fastened joint to be secure while the collar itself remains removable through the drive portion.
Solution Approach 2:
The conical interface creates a dynamic deformation zone during swaging that allows controlled engagement. The cone geometry enables the collar to be deformed onto the shaft for secure fastening while the drive portion maintains thread engagement for subsequent removal 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
Enables quick installation, high clamp load resistance to thermal expansion and vibration, and easy reassembly or replacement of the collar, reducing material deformation and tooling complexity.
Implementation Method 1
a main portion adapted to be swaged onto the locking portion
Implementation Method 2
high clamp load resistance to thermal expansion and vibration
Data Source
Figure 1~2A
Figure 2B~2C
Figure 3A~3B
AI summary
Method of installing a fastener (10) to a structure (34) with a first and a second workpiece (54, 58), fastening assembly and fastener (10) comprising: - a stud (12) having a head (16), and a shaft (18) extending along a longitudinal axis (X) and defining a shaft length (Ls), wherein the shaft (18) comprises a locking portion (24), said locking portion (24) defining a shaft diameter (Ds); - a collar (14) adapted to be fitted over the locking portion (24) of the shaft (18), the collar (14) comprising a first collar end (36), a second collar end (38), a central through bore (40) extending from the first collar end (36) to the second collar end (38), the central through bore (40) defining a bore diameter (Db), and a main portion (42) adapted to be swaged onto the locking portion (24), wherein a ratio of the bore diameter (Db) to the shaft diameter (Ds) is above 1.10:1.