Electric Equipment Box Assembly for Air Conditioner Flame Containment
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Solution Overview
Problem
In wall-hung type air conditioners, there is a risk of flame spread from an electric equipment box to the main body and design panel due to the burning and melting of resin components during an electrical fire, as the existing designs lack effective flame inhibition mechanisms.
Innovation Solution
The air conditioner incorporates a design with a container portion made of resin containing a control board and terminal block, a sheet metal case, a resin cover, and a sheet metal lid body, where locking claws and holes create a flame spread inhibiting path by overlapping edges, ensuring that even if the resin components burn, the flame is contained within the electric equipment box and cannot spread to the main body or design panel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If resin components (container portion and cover) are used in the electric equipment box, then ease of manufacture and cost are improved, but flame spread risk increases when electrical fire occurs
Solution Approach 1:
The electric equipment box is divided into multiple segments: container portion (resin), case (sheet metal), cover (resin), and lid body (sheet metal). This segmentation isolates flame spread by creating separate compartments with metal barriers between them, preventing fire from propagating through the entire structure while maintaining resin components for ease of manufacture.
Solution Approach 2:
Sheet metal components (case and lid body) serve as intermediary barriers between resin components (container portion and cover). These metal intermediaries prevent direct flame transmission from one resin part to another, blocking the fire spread path while allowing the resin parts to remain for manufacturing advantages.
2Ease of operation
If locking claws and holes are used to assemble components, then ease of assembly is improved, but flame spread paths may be created at connection points
Solution Approach 1:
The locking claws and holes create a nested structure where the case penetrates into the container portion, and the lid body penetrates into the cover. This nesting ensures tight fitting at connection points, reducing gaps that could serve as flame spread paths while maintaining easy assembly through the locking mechanism.
Solution Approach 2:
The connection points with locking claws and holes are designed with specific local qualities - tight fitting and overlapping edges - to prevent flame spread at these critical locations. The local structure at connection points differs from other areas by having interlocking metal-resin interfaces that block fire propagation.
3Ease of operation
If opening edges of case and cover are exposed, then ease of assembly is improved, but flame can spread through gaps between components
Solution Approach 1:
The solution addresses the gap problem by adding vertical overlap between the case and lid body, creating a three-dimensional barrier. Instead of relying solely on horizontal sealing, the overlapping edges in the vertical dimension block flame spread paths that might exist at component interfaces.
Solution Approach 2:
The case and lid body are positioned to overlap, merging their protective functions. This overlap creates a continuous metal barrier that combines the fire resistance of both components, eliminating gaps that would otherwise allow flame propagation between the container portion and cover.
Data Source
AI summary
A locking claw on an outer face of a container portion made of resin is engaged with a locking hole in an outer periphery of a case made of sheet metal, the container portion being covered by the case, a locking claw on an outer face of a cover is engaged with a locking hole in an outer periphery of a lid body, the cover being covered by the lid body, they are assembled so that a part of an opening edge of an opening portion of the case is covered by an opening edge of an opening portion of the cover, the container portion and the case as well as the cover and the lid body are fixed to form an electric equipment box and a flame spread inhibiting path is formed between the lid body and the case.