Blind Fastener Bulb Separation for Large Footprint
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing blind fasteners face challenges in securely engaging the blind side of work pieces with a large footprint, particularly when access is limited, and they often result in indentations and high buckling loads during installation.
Innovation Solution
A blind fastener design featuring a core bolt and sleeve combination, where the sleeve forms a bulb that separates and engages the blind side with a tapered notch, providing a larger diameter footprint and frictional enhancement to prevent rotation, while the core bolt absorbs buckling loads and minimizes indentations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a large footprint bulb is formed on the sleeve to engage the blind side of work pieces, then the engagement area is increased, but the installation process generates high buckling loads and indentations on the work pieces
Solution Approach 1:
The sleeve is divided into two functional segments: a bulb-forming portion that creates the large footprint engagement area, and a tapered portion that provides structural support. This segmentation allows the bulb to engage the blind side with large area while the tapered portion absorbs and distributes buckling loads, preventing indentations on the work pieces.
Solution Approach 2:
The sleeve features localized structural variations: the bulb portion has a larger diameter for engagement, while the tapered portion has a gradually reducing diameter optimized for load distribution. This local quality differentiation enables the engagement area to be large without concentrating excessive forces that would cause indentations.
2Area of stationary object
If a large footprint bulb is formed on the sleeve to engage the blind side of work pieces, then the engagement area is increased, but indentations are created on the work piece surface
Solution Approach 1:
The sleeve is segmented into a bulb portion for engagement and a tapered portion for load management. The tapered portion acts as a transition zone that distributes installation forces over a larger area, preventing stress concentration that would cause indentations on the work piece surface.
Solution Approach 2:
The tapered portion of the sleeve serves as a cushioning element during installation. Its gradual geometry absorbs and distributes the impact forces before they reach the work piece surface, preventing indentations while still allowing the bulb to form with sufficient engagement area.
3Area of stationary object
If the bulb diameter is increased to improve engagement on the blind side, then the footprint is enlarged, but the sleeve becomes more prone to rotation during installation
Solution Approach 1:
The tapered portion introduces asymmetry in the sleeve's geometry, creating a wedging effect during installation. This asymmetric shape generates frictional forces and mechanical interference that prevent rotation, while the bulb portion maintains its symmetric circular footprint for optimal engagement area on the blind side.
Solution Approach 2:
The tapered portion's curved geometry creates a wedging action during installation that naturally resists rotation. The gradual curvature transition from the bulb portion provides a stable insertion path that maintains alignment and prevents the sleeve from rotating while being installed into the work pieces.
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 effectively secures work pieces with a large footprint on the blind side, reducing indentations and peak buckling loads, and ensures stable engagement without rotation issues.
Implementation Method 1
the tapered portion includes a frictional enhanced surface that is adapted to inhibit rotation of the bulbed portion relative to the elongated body after the bulbed portion separates from the elongated body
Data Source
AI summary
A blind fastener including a pull-type core bolt having a shank with a head, and a sleeve having an elongated body with a head, and a tapered notch formed within an exterior surface thereof and defined by a tapered portion having a slope and a frictional enhanced surface. The core bolt is installed within the sleeve. During installation of the fastener within the plurality of work pieces, an axial force is applied to the core bolt the head of the core bolt engages the sleeve, and a bulb is formed on the elongated body of the sleeve, the bulb defining a portion of a bulbed portion. When a selected axial force is reached, the bulbed portion separates from the elongated body and engages axially the tapered portion of the sleeve, increasing the diameter of the bulb which engages a blind side of one of the work pieces.