L-Track Fitting Lug Anchor Shear Strength
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Solution Overview
Problem
Existing track fittings in vehicles, such as those used in buses, lack sufficient strength to secure seats and wheelchair restraints due to stress concentration and limited stud size, which is exacerbated by increased loads during sudden deceleration and changing industry regulations.
Innovation Solution
The design features a track fitting with three lugs on each side and a load beam with a larger cross-section, allowing the stud to be positioned above the narrowing portions of the L-track, providing better load distribution and increased shear strength, and a locking mechanism that secures onto the load beam rather than the stud for enhanced stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If single or double stud fittings are used in L-track, then the device complexity is reduced and installation is simplified, but the pull-out force and shear strength are insufficient to withstand higher loads
Solution Approach 1:
The anchor is segmented into multiple lugs (at least three lugs on each side of the track) instead of using a single stud or double stud configuration. This segmentation distributes the load across multiple contact points with the track, significantly increasing the pull-out force and shear strength while maintaining a relatively simple overall structure.
Solution Approach 2:
The lugs are positioned to engage with specific narrowed portions of the L-track at localized points. This local engagement creates high-stress concentration points that effectively transfer loads from the anchor to the track structure, enhancing the overall strength without requiring a complex multi-component system.
2Strength
If the stud diameter is increased to provide greater strength, then the shear load capacity improves, but the stud cannot fit between the narrowing portions of the L-track
Solution Approach 1:
The invention transitions from a single-dimensional stud configuration to a multi-dimensional lug arrangement. Instead of increasing the diameter of a single stud, the solution uses multiple lugs extending laterally from the anchor body, engaging with narrowed portions of the track at different positions. This dimensional change allows the anchor to achieve greater shear load capacity without requiring a larger single component that would not fit in the track.
3Reliability
If more locking mechanisms are added to provide additional index members, then the reliability of securing the anchor improves, but the device complexity and number of parts increase
Solution Approach 1:
The locking mechanism is merged with the anchor body such that the lugs themselves serve as the indexing elements. The narrowed portions of the L-track engage directly with the lugs to provide the locking action, eliminating the need for separate locking members or index members. This integration maintains high reliability while minimizing the number of parts.
4Strength
If the anchor is designed with a low profile to minimize visibility and space, then the aesthetic appearance and space utilization improve, but the structural strength may be compromised
Solution Approach 1:
The anchor employs a thin-walled but structurally optimized geometry that provides high strength-to-weight ratio. The wall thickness and cross-sectional geometry of the anchor body are designed to resist bending and buckling forces while maintaining a low overall profile. This allows the anchor to achieve the necessary structural strength without increasing its height or visual prominence.
Data Source
AI summary
A track fitting assembly for engagement with an L-track is disclosed herein. The track fitting assembly includes an anchor with at least one, but preferably three track engaging lugs extending from each side of the anchor. The anchor includes a load beam whose cross-section is larger than the anchor portion not comprising the load beam. The top surface of the load beam rises above the top surface of the track. A stud extending upwards from the load beam, and because it sits above the track, the diameter of the stud is not limited by the narrowed portions of the L-Track or the load beam. The track fitting assembly also includes a locking mechanism comprising at least one index member on each side, wherein the index members fit between the lugs of the anchor. The locking mechanism comprises an opening for receiving one or both of the load beam and the stud. A nut secures hardware to the track fitting assembly through engagement with the stud.