Junction Box Cover Retention With Rotating Axial Rod
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Solution Overview
Problem
Conventional jump start housings in electric junction box assemblies are prone to having their covers inadvertently dislodged, leaving the jump start bolt unprotected.
Innovation Solution
The electric junction box assembly features a housing with arcuate support members and an axial rod with intermediate portions that prevent the cover from being dislodged, combined with a resilient stop and rib to secure the cover in place, preventing accidental removal and rattling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional jump start cover is used, then the jump start bolt is protected, but the cover can be inadvertently dislodged
Solution Approach 1:
The axial rod includes intermediate portions with arcuate inner surfaces that engage corresponding arcuate outer surfaces on the support members. This curved geometry enables rotational movement while maintaining engagement, allowing the cover to rotate into a secured position where the intermediate portions prevent dislodgement without requiring complex fastening mechanisms
Solution Approach 2:
The cover transitions from a static attached state to a dynamic rotating state. The axial rod is designed to rotate within the housing, moving from an insertion position to a secured position where the intermediate portions engage with the support members. This dynamic mechanism provides both ease of operation (simple rotation) and reliability (secured position prevents inadvertent dislodgement)
2Reliability
If the cover is securely mounted to prevent dislodgement, then reliability improves, but device complexity increases
Solution Approach 1:
The axial rod is segmented into distinct portions: a first portion for insertion, intermediate portions with arcuate surfaces for engagement, and a second portion extending outward. The support members are also segmented with corresponding arcuate surfaces. This segmentation allows each component to perform its specific function simply, avoiding the need for complex integrated mounting mechanisms
Solution Approach 2:
The arcuate inner surfaces of the intermediate portions engage with arcuate outer surfaces on the support members, creating a simple curved engagement mechanism. This geometric solution provides reliable retention through rotational engagement without requiring threads, clips, screws, or other complex fastening elements
3Reliability
If the cover can rotate to prevent dislodgement, then reliability improves, but manufacturing precision requirements increase
Solution Approach 1:
The intermediate portions extend slightly beyond what would be minimally required for engagement, providing excessive action in the form of extended arcuate surfaces. This ensures that even with variations in manufacturing precision, sufficient engagement surface area is available to maintain reliable rotational engagement and prevent dislodgement
Solution Approach 2:
The arcuate surfaces provide a generous engagement geometry that is tolerant of manufacturing variations. The curved surfaces allow for self-alignment during rotation, reducing the precision required for initial positioning while ensuring reliable engagement once rotated into place
Data Source
AI summary
An electric junction box assembly includes a case, a housing and a cover. A housing is disposed on an outer surface of the case. The housing includes a back wall and a pair of supports disposed on the back wall. The supports are spaced apart from each other and each support includes an upper support member and a lower support member spaced apart from each other so as to define an opening. The upper support member has an arcuate inner surface and the lower support member has an arcuate inner surface each having a radius greater than the opening. The cover includes an axial rod having a thickness smaller than a height of the opening and a width greater than the height of the opening, wherein a rotation of the axial rod prevents the cover from being dislodged from the opening.