Blind Fastening Assembly With Segmented Sleeve for Lower Wall Stress
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing fastening assemblies apply high local forces on the wall surface surrounding the opening, leading to potential deformation and inadvertent loosening, which compromises the stability of the attachment.
Innovation Solution
A fastening assembly with a collapsible wedge member and an expansion sleeve that bends its segments to increase the contact surface with the wall, distributing forces more evenly and preventing deformation, featuring a collapsible wedge member and an expansion sleeve with slanting inner surfaces to facilitate initial engagement and sliding, and a design that blocks mutual rotation to enhance stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the expansion sleeve is tightened over the wedge member in conventional fastening assemblies, then the head surface of the expansion sleeve expands to a larger diameter and abuts the wall surrounding the opening, but high local stresses are incurred in the material of the wall surrounding the opening
Solution Approach 1:
The expansion sleeve is divided into multiple deformable wall segments that can bend independently. This segmentation allows the force to be distributed across multiple bending points rather than concentrated at a single abution point, reducing local stress on the wall while maintaining fastening strength
Solution Approach 2:
The expansion mechanism transitions from radial expansion (increasing diameter) to axial bending (increasing contact length along the wall). The wall segments bend to engage the inner surface of the wall, creating a larger contact surface area that distributes forces along the axial dimension rather than concentrating them at a single point
2Reliability
If the expansion sleeve is tightened to expand the head surface diameter, then the fastening assembly achieves secure attachment, but the opening can deform which may allow inadvertent loosening
Solution Approach 1:
The segmented wall segments distribute the attachment force across multiple contact points along the wall, preventing concentration of forces that would cause opening deformation. Each segment independently engages the wall, creating a stable attachment that preserves opening geometry
Solution Approach 2:
The design changes the engagement parameter from diameter expansion to contact length increase. By bending the wall segments to create extensive contact along the wall surface, the fastening achieves secure attachment without the radial force concentration that deforms the opening
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 provides a stable and secure attachment by reducing high local stresses on the wall, preventing deformation and inadvertent loosening, ensuring a larger contact surface area for better force distribution and enhanced stability.
Implementation Method 1
the expansion sleeve is adapted to bend its segments to such a degree that the end of the expansion sleeve that has advanced towards the wall, engages with its inner surface the surface of the wall surrounding the opening
Implementation Method 2
the wedge member is a collapsible part, which is adapted to collapse when the wall segments of the expansion sleeve are tightened towards the wall of the constructional member
Data Source
Figure 1~5
Figure 6~7
Figure 8A~8E
AI summary
A blind fastening assembly (1) comprises a bolt having a bolt shank and a bolt head (21), a metal expansion sleeve (5) fitted in use over at least a part of the bolt shank and having deformable wall segments, a washer (3) arranged over the bolt shank, a wedge member (6) arranged between the washer and the expansion sleeve and having a wedge portion adapted to be inserted in one end of the expansion sleeve, and a nut (4) arranged on the shank. The nut is adapted to tighten the washer and the expansion sleeve towards each other so as to pull the wedge portion of the wedge member into the expansion sleeve resulting in the wall segments being pushed outwardly. The wall segments have an inner side with an inner side surface adapted and arranged to engage a wall surface surrounding the opening in the wall of the constructional member opposite the washer.