Distribution Junction Box Ribs for Draw Spring Guidance
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Solution Overview
Problem
Existing distribution junction boxes often result in draw springs getting stuck and inadequate guidance, making it difficult for electricians to install wiring correctly, and complicate the manufacturing and stocking of precast concrete slabs with these boxes.
Innovation Solution
The design features ribs that smoothly transition into the bottom of the box, with each passage opening having its own pair of ribs, and a conical elevation that smoothly changes into the bottom, creating a duct that narrows towards the center for optimal guidance of the draw spring, and allows for modular construction with separable box members for easier adaptation to various slab thicknesses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If ribs are made perpendicular to the bottom of the box, then the draw spring is guided in circumferential direction, but the draw spring may get stuck at the corner location
Solution Approach 1:
The rib is designed to smoothly curve into the bottom of the box rather than forming a sharp perpendicular corner. This curvature eliminates the buckle or stop shoulder that causes the draw spring to get stuck, while still providing adequate guidance in the circumferential direction.
Solution Approach 2:
The rib geometry is modified by changing the angle and curvature parameters along its length. Instead of a constant perpendicular orientation, the rib transitions from a steeper angle near the passage opening to a smoother curve near the bottom, optimizing both guidance and preventing stagnation points.
2Device complexity
If ribs are shared between adjacent passage openings, then the box structure is simplified, but guidance of the draw spring is insufficient at the wall section separating passage openings
Solution Approach 1:
The box is divided into multiple rib pairs, with each passage opening having its own dedicated pair of ribs. This segmentation ensures that each draw spring insertion point has sufficient guidance without compromising the overall structural simplicity of the box.
3Ease of manufacture
If distribution junction boxes are incorporated in precast concrete slabs with fixed heights, then manufacturing is simplified, but the concrete manufacturer must keep a wide variety of boxes in stock
Solution Approach 1:
The box design incorporates adjustable or modular components that allow the effective height to be varied. This dynamic adaptability enables a single box type to serve multiple slab thickness requirements, reducing the need for concrete manufacturers to maintain extensive inventories of different box heights.
4Ease of manufacture
If the box is provided as a single integrated unit, then manufacturing is straightforward, but adaptation to various slab thicknesses and electrician's wishes is difficult
Solution Approach 1:
The box is divided into multiple separable members or modules that can be assembled in different configurations. This segmentation maintains manufacturing simplicity for each individual module while providing flexibility in the final assembly to accommodate various slab thicknesses and electrical distribution requirements.
Solution Approach 2:
The modular box design creates universal components that can serve multiple functions and configurations. Each module is designed to be adaptable, allowing the same basic component to work in different arrangements to meet varying electrical distribution needs and slab thickness requirements.
Data Source
Figure 1~2
Figure 3
Figure 4A~4B
AI summary
Box for accommodating wires of electric wirings, comprising a bottom and a circumferential wall. The box is provided with a passage opening suitable to allow a draw spring through, and with ribs for counteracting movement of the draw spring in circumferential direction in the box. The ribs extend up to the circumferential wall of the box. The ribs smoothly change into the bottom of the box. When there are several passage openings, the box contains a pair of relating ribs for each passage opening. The box is provided with an elevation projecting inwardly from bottom of the box, from which elevation the ribs extend, wherein the elevation smoothly changes into the bottom of the box.