Captive Fastener Assembly With Radial Float for Tolerance Misalignment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Captive fastener systems face challenges in accommodating varying tolerances between structures, leading to difficulties in secure joining and attachment, especially in environments where precise alignment is critical, such as low gravity settings.
Innovation Solution
The proposed captive fastener system includes a sleeve with internal threads to secure a fastener, a biasing element for additional stability, and a mounting assembly that provides two degrees of movement, allowing for increased tolerances and flexibility in alignment through radial float and additional structural freedom.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a captive fastener system uses fixed alignment between structures, then manufacturing precision is improved, but adaptability deteriorates
Solution Approach 1:
The fastener system incorporates a movable mounting assembly that can shift position within a mounting aperture, transforming the static fastening system into a dynamic one. This allows the fastener to adapt to varying tolerances and misalignments between structures while maintaining secure attachment, effectively resolving the contradiction between precision and adaptability.
Solution Approach 2:
The system changes the positional parameter of the mounting assembly relative to the mounting aperture. By allowing the mounting assembly to move within the aperture boundaries, the system accommodates variations in alignment without compromising the fastening security, thus balancing manufacturing precision requirements with tolerance accommodation.
2Adaptability or versatility
If a captive fastener system provides movement freedom, then adaptability is improved, but stability deteriorates
Solution Approach 1:
The mounting assembly is designed to be movable during the fastening process to accommodate misalignments, but once positioned, it becomes stabilized by the captive fastener mechanism. This dynamic-to-stable transition allows the system to provide both movement freedom for adaptability and stability for secure attachment.
Solution Approach 2:
The system incorporates a biasing element that provides pre-compression or pre-positioning force to the mounting assembly. This beforehand cushioning ensures that once the fastener is engaged, the mounting assembly is firmly held in position, maintaining stability while having previously allowed for movement to accommodate tolerances.
3Adaptability or versatility
If a captive fastener system uses reduced shank diameter, then radial float is improved, but strength deteriorates
Solution Approach 1:
The fastener shank is designed with varying diameters along its length - a reduced diameter portion for radial float capability and a full-diameter threaded portion for strength. This local quality differentiation allows the fastener to provide both radial float for adaptability and full strength for secure attachment, resolving the contradiction between the two requirements.
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
Captive fastener systems and structural assemblies having captive fastener systems are described. The captive fastener systems (300) include a captive fastener assembly (302) having a sleeve (308) and a captive fastener (320) arranged within the sleeve, a mounting assembly (304) having a bushing (322) and a mounting fastener (320) arranged to pass through the bushing, and a joining body (306) having a mounting aperture (304), wherein the sleeve is attached to the joining body and the bushing and the mounting fastener are configured to pass through the mounting aperture. The mounting assembly is configured to provide a first degree of movement of the captive fastener system and the captive fastener assembly is configured to provide a second degree of movement of the captive fastener system.