Spring-Loaded Cam-Lock Fastener for Tolerance Stackup
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Solution Overview
Problem
Conventional cam-lock fastening systems struggle to maintain consistent preload and accommodate tolerance stackups in rigid metal or composite structures, particularly in applications requiring precise alignment and high-fidelity electrical connections, such as in INDYCAR racing and missile systems, where manual adjustments are time-consuming and impractical.
Innovation Solution
A longitudinal tolerance-mitigating cam-lock fastening system utilizing a spring-loaded pin plate assembly and cam plate assembly, which includes a spring element to maintain preload and accommodate tolerance variations, enabling blind electrical connections without manual adjustment, and allowing for interchangeable 'plug and play' of components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional metal cam-lock and pin system is used to fasten rigid metal or composite structures, then the fastening mechanism can provide structural connection, but it cannot accommodate tolerance stackup variations in rigid structures without manual adjustment
Solution Approach 1:
The patent changes the physical state of the pin from rigid to flexible by introducing a flexible portion that can bend elastically. This allows the pin to accommodate tolerance stackup variations in rigid structures without requiring manual adjustment, while still providing sufficient preload when fastened
Solution Approach 2:
The patent introduces a dynamic element (flexible pin portion) that can adapt its position based on tolerance variations. The flexible pin can bend to accommodate misalignment while the cam-lock mechanism maintains the fastened state, eliminating the need for manual adjustment
2Manufacturing precision
If the pin is made longer to accommodate tolerance variations, then the tolerance stackup capacity increases, but the preload and clamping force are reduced
Solution Approach 1:
The patent changes the pin from a rigid linear element to a flexible element with controlled bending characteristics. The flexible pin can deflect to accommodate tolerance variations while maintaining adequate preload through elastic recovery, solving the trade-off between tolerance capacity and clamping force
Solution Approach 2:
The flexible pin portion acts as a built-in cushion that absorbs tolerance variations before they affect the preload. The elastic flexibility provides a buffer that maintains consistent clamping force despite variations in hole alignment
3Force
If a rigid pin is used to maintain precise preload, then the clamping force is consistent, but it cannot accommodate tolerance stackup in rigid structures
Solution Approach 1:
The patent transitions the pin from rigid to flexible, allowing it to bend and accommodate tolerance variations while the cam-lock mechanism ensures consistent preload is applied once fastened. The flexibility is controlled to maintain adequate clamping force
4Measurement precision
If manual adjustment is implemented to achieve precise alignment, then the preload accuracy is improved, but the assembly time and complexity increase
Solution Approach 1:
The flexible pin performs the alignment adjustment function automatically through its elastic bending capability. No manual intervention is required as the pin self-adjusts to accommodate tolerance variations during insertion, then maintains precise preload when fastened by the cam-lock mechanism
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 system provides a consistent preloaded structural joint with specified minimum and maximum loads over a range of tolerances, facilitating rapid and reliable attachment and detachment of components, including missile payloads, without the need for manual adjustment, and ensures high-fidelity electrical connections.
Implementation Method 1
The spring element can compress to maintain the designed preload throughout its deflection resulting in a clamping force on the surface between the first and second structures as the cam-lock rotates to a locked position
Data Source
AI summary
A cam-lock fastening system is designed to accommodate a tolerance stackup to fasten a pair of rigid structures. A spring allows some longitudinal motion of the pin that would not be accommodated by the rigid structures or metal cam-lock and pin. The spring-loaded pin is also suitably designed to produce a preloaded structural joint that is between specified minimum and maximum loads for any tolerance stackup that is within specification. The fastening of the structures requires no manual adjustment of the pin, and facilitates blind connection of a high-fidelity electrical connector. Further, the described cam-lock fastening system is designed for high performance applications requiring preload forces in the thousands of pounds per square inch.