Blind Fastener Frangible Break-Off for Flush Panel Installation
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Solution Overview
Problem
Existing blind fasteners face challenges in controlling the rotation of both the bolt and nut, achieving a flush finish, adapting to variations in grip length, and preventing defective installations due to excessive torque, which affects the strength and aesthetics of the joint.
Innovation Solution
A blind fastener design featuring a bolt with a shaft, bolt head, and lug, and a nut with a sleeve and handling member, incorporating frangible portions and tool engagement features that allow for controlled torque transmission and adaptation to varying grip lengths, ensuring a flush installation without the need for post-installation grinding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the break-off point of the core bolt is not controlled, then the fastener can be installed, but the finished product cannot be flush with panels requiring post-installation grinding
Solution Approach 1:
The patent incorporates a frangible portion in the bolt head that is designed to break off at a predetermined location during installation. This preliminary design ensures that the break-off point is controlled in advance, allowing the bolt head end surface to be flush with or recessed from the panel surface, thereby eliminating the need for post-installation grinding and achieving a clean finished appearance.
2Manufacturing precision
If rotation of both bolt and nut is controlled, then installation precision is improved, but installation complexity and time increase
Solution Approach 1:
The patent extracts the rotation control function from the bolt and assigns it to the nut alone. The nut includes a frangible portion that breaks off to control rotation, while the bolt simply needs to be inserted and threaded. This separation simplifies the overall installation process by reducing the number of components requiring coordinated rotation control.
3Productivity
If torque is not controlled, then installation is faster, but excessive torque causes sleeve to flare forming defective tulip configuration
Solution Approach 1:
The patent incorporates a frangible portion in the nut that is designed to break off at a predetermined torque level during installation. This preliminary design feature automatically limits the maximum torque applied to the fastener, preventing the sleeve from flaring out to form a defective tulip configuration while still allowing for relatively fast installation without complex torque control mechanisms.
4Manufacturing precision
If frangible portions are incorporated, then controlled break-off is achieved, but additional manufacturing steps are required
Solution Approach 1:
The patent incorporates frangible portions in both the bolt head and nut by modifying the cross-sectional area or material properties at specific locations during manufacturing. These frangible portions are designed with reduced cross-sectional area or different material characteristics that cause them to break at predetermined torque levels. While this adds manufacturing steps, it provides precise control over the break-off point and torque limitation, ensuring reliable and high-quality fastener installation.
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 enables controlled rotation and secure clamping of panels, adapts to grip length variations, and prevents defective installations by using frangible portions to ensure a flush finish and maintain joint strength, reducing installation costs and time.
Implementation Method 1
The first frangible portion frangibly couples the lug to the bolt head. The second frangible portion frangibly couples the second tool engagement portion to the nut head.
Implementation Method 2
The sleeve includes a central bore configured to receive the shaft and defining internal threads configured to mate with the external threads.
Data Source
Figure 1~2
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AI summary
A blind fastener (10) for connecting panels (26,30) includes a bolt (14) and nut (18). The bolt includes a shaft (110), bolt head (114), and lug (118). The bolt head is between the shaft and lug. The lug includes a first tool engagement portion (150) and first frangible portion (154) that connects the lug and bolt head. The nut includes a sleeve (210), nut head (214), and handling member (218). A central bore (230) of the sleeve receives the shaft and defines internal threads (234) mated with the external threads. The nut head extends radially from the sleeve and defines a recess (242) that receives the bolt head. The handling member surrounds a portion of the lug. The handling member includes a second frangible portion (270) and a second tool engagement portion (266). The second frangible portion couples the second tool engagement portion to the nut head.