Underground Vault Fastening System with Shearable Composite Nut
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Solution Overview
Problem
Existing fastening systems for underground vaults and pits are prone to failure due to bolt and nut seizure, thread contamination, and damage during re-entry, leading to security and access issues.
Innovation Solution
A fastening system with a nut and bolt arrangement that features a floating nut design or fixed nut attachment, using composite materials like glass-filled nylon to ensure the nut threads shear before other components fail, and includes geometries and chamfers to manage torque and misalignment, reducing the risk of damage during entry and enhancing tamper resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional bolt and nut fastening systems are used to secure covers to underground vaults, then the covers are firmly attached and tamper-resistant, but the fastening system is highly prone to failure due to seizure, thread contamination, and stripping
Solution Approach 1:
The patent extracts the fastening function from the traditional bolt-nut system and relocates it to a track-mounted carriage system. The bolts pass through the cover and engage with carriages that ride on tracks embedded in the vault, separating the fastening mechanism from the traditional seized-prone bolt-nut interface. This allows the cover to be securely attached while eliminating the seizure and contamination problems of threaded fasteners.
Solution Approach 2:
The patent changes the fastening mechanism from threaded engagement to track-based linear engagement. The carriage moves along the track with controlled friction, providing secure attachment without the thread contamination and seizure issues. The friction parameter is optimized to provide sufficient holding force while allowing controlled movement for cover removal.
2Reliability
If tamper-resistant features such as Penta head designs are used on bolts, then security is enhanced, but when fastening fails, the cover cannot be removed without breaking it
Solution Approach 1:
The patent segments the fastening system into separate functional components: the cover with through-holes, the bolts, the carriages with tamper-resistant features, and the track system. The tamper-resistant features are concentrated in the carriage component rather than the bolt head, allowing the cover to be accessed by removing the carriage from the track while preserving the cover integrity. This segmentation enables security features without compromising cover removability.
Solution Approach 2:
The carriage acts as an intermediary between the bolt and the track system. It provides the tamper-resistant features while riding on the track, allowing the cover to be securely fastened and later removed by detaching the carriage from the track rather than breaking the cover. The intermediary carriage absorbs the security function, preserving the cover for future access.
3Strength
If advanced composite materials are used to manufacture covers, then cover strength and resistance to breaking are improved, but when retaining systems fail, extreme measures are required to re-enter the box
Solution Approach 1:
The patent extracts the fastening function from the cover material itself and relocates it to the track-mounted carriage system. This allows the use of strong composite materials for the cover without compromising re-entry capability, as the cover can be accessed by removing the external carriage fasteners rather than breaking the cover material. The fastening function is separated from the cover structure.
Solution Approach 2:
The patent introduces dynamic capability to the fastening system through the movable carriage on the track. The carriage can be positioned, engaged, and disengaged dynamically, allowing the strong composite cover to be securely fastened during operation and easily accessed when needed by simply detaching the carriage, without requiring extreme measures to break into the cover.
4Reliability
If anti-seize compounds are added to prevent bolt and nut galling, then galling is reduced, but particulates are given a grease-like compound to adhere to and carried into the bolt/nut thread interface
Solution Approach 1:
The patent extracts the fastening interface from the traditional bolt-nut threaded system and relocates it to a track-mounted carriage system. This eliminates the threaded interface that is susceptible to contamination by particulates carried by anti-seize compounds. The fastening function is maintained through friction-based track engagement, removing the source of contamination problems.
Solution Approach 2:
The patent replaces the threaded mechanical fastening system with a track-based linear engagement system. The threaded interface that is vulnerable to contamination by grease-like anti-seize compounds is substituted with a friction-based track carriage system, eliminating the harmful effect of particulate contamination while maintaining secure fastening.
Data Source
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AI summary
A fastening system (10) for attaching a cover to an underground vault having a bolt (12) with threads (18) and a composite fiber reinforced polymer nut (14) having a thread engagement portion (22) extending through the nut (14) which will fail in shear after the bolt (12) is inserted before the nut (14) and bolt (12) seize. The fastening system (10) can also include a nut retainer (16) sized to allow the nut (14) to float within the retainer (16).