Bracket Attachment Strength in Electrical Junction Box
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Solution Overview
Problem
Conventional electrical junction boxes face issues with insufficient strength in the connecting part between the bracket and the box body, leading to deformation and instability under external forces, as the bracket is fixed only to the peripheral wall portion of the outer casing, concentrating the load and potentially causing the peripheral wall to bulge or break.
Innovation Solution
The electrical junction box design includes a fitting projection portion on the inner casing that engages with a fitting recess on the bracket, dispersing external forces across both casings and enhancing attachment strength, with the fitting projection portion utilizing a strong edge portion between the bottom and side walls to secure the bracket to both casings, allowing for stable attachment without concentrating force on a single peripheral wall.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the bracket is fixed only to the peripheral wall portion of the outer casing, then the structure is simple and easy to manufacture, but the attaching strength is insufficient and the peripheral wall portion is likely to deform under external force
Solution Approach 1:
The bracket is divided into multiple attachment points: engagement lock portions that attach to the outer casing and a fitting projection portion that attaches to the inner casing. This segmentation distributes the attachment function across multiple locations, improving overall attaching strength while maintaining manufacturing simplicity through modular design
Solution Approach 2:
The inner casing is nested within the outer casing, and the bracket utilizes both casings for attachment. The fitting projection portion on the inner casing engages with the bracket while the engagement lock portions on the outer casing provide additional support, creating a nested attachment structure that enhances strength without complicating manufacturing
2Device complexity
If the bracket is fixed only to the peripheral wall portion of the outer casing, then the structure is simple, but the load is concentrated on the peripheral wall portion causing deformation and instability
Solution Approach 1:
The attachment structure is segmented into two independent systems: engagement lock portions on the outer casing and a fitting projection portion on the inner casing. This segmentation distributes the load across multiple attachment points rather than concentrating it on a single peripheral wall portion, improving stability while keeping the overall device complexity manageable
Solution Approach 2:
The bracket merges attachment to both the outer casing (via engagement lock portions) and the inner casing (via fitting projection portion). This combining of attachment points creates a more stable configuration that resists deformation under external force without significantly increasing device complexity
3Reliability
If an engagement projection portion is locked on the thin peripheral wall portion to prevent lifting, then the peripheral wall is secured, but the structure cannot obtain sufficient strength and space is wasted
Solution Approach 1:
The fitting projection portion on the inner casing (nested component) engages with the bracket to provide reliable attachment. By utilizing the nested inner casing structure, the design achieves both reliability and sufficient attaching strength without wasting space, as the inner casing is already present and underutilized for attachment purposes
Data Source
AI summary
To provide an electrical junction box in which an electrical junction box body includes one casing and the other casing, the other casing is prevented from being lifted from the one casing, and a bracket can be attached to a peripheral wall portion of the other casing stably and strongly. One casing is fitted in the other casing. A peripheral wall portion of the other casing is provided on an outer peripheral surface with engagement lock portions. A bottom wall section of the one casing is exposed from an opening defined by the peripheral wall portion. A fitting projection portion is provided on the bottom wall section near the engagement lock portions. The bracket is mated with the engagement lock portions. The fitting projection portion is mated with a fitting recess provided in the bracket to attach the bracket to the other casing.