Conductive Housing Skin Fastening for Reliable Ground Contact
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Solution Overview
Problem
Existing methods for grounding metal parts in electrical devices, especially those with painted or insulating coatings, face challenges in establishing a reliable and resilient conductive connection due to the need for soft or thin materials to avoid excessive torque, leading to connections that can't withstand loads.
Innovation Solution
A housing design featuring an electrically insulating structure with a conductive skin and screws that engage in a bore, displacing material to create a secure electrical contact and a secure hold, using a recess with serrated edges to facilitate easy deformation and maintain contact under forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a screw with a sharp-edged profile is used to establish reliable conductive contact with painted or insulating coated metal sheet, then the electrical contact reliability is improved, but the sheet metal must be soft or thin which limits the load capacity of the connection
Solution Approach 1:
The recess in the skin is designed with serrated edges that create localized deformation zones. When the screw is inserted, it displaces the serrated edges locally to establish electrical contact, while the overall connection structure maintains high load capacity through the bore engagement in the fixed structure.
Solution Approach 2:
The connection system is divided into three functional parts: the fixed structure with bore for mechanical anchoring, the skin with recess for electrical contact, and the screw as the connecting element. This segmentation allows each component to be optimized independently - the fixed structure provides strength, the recess provides conductivity, and the screw provides both functions simultaneously.
2Ease of manufacture
If the sheet metal is made soft or thin to allow screw thread tapping without excessive torque, then the electrical contact is improved, but the connection can only withstand low loads
Solution Approach 1:
The solution moves from a single-dimension approach (relying solely on sheet metal thickness) to a multi-dimensional approach by adding the fixed structure with bore as a second dimension of mechanical support. This allows thin sheet metal to be used while maintaining high load capacity through the combined effect of bore engagement and skin attachment.
3Ease of manufacture
If the skin is made thin and inexpensive, then the manufacturing cost is reduced, but the mechanical strength and durability of the housing is compromised
Solution Approach 1:
The skin is merged with the fixed structure through the screw connection that engages both the bore in the fixed structure and the recess in the skin. This merging creates a composite structure where the thin skin provides electrical contact and aesthetic function, while the fixed structure provides mechanical strength, achieving both cost-effectiveness and durability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design achieves a reliable and durable conductive connection between the skin and carrier, ensuring the electrical contact remains secure despite external forces, even with thin and inexpensive sheet metal, and can be applied to various electrical devices like refrigerator housings.
Implementation Method 1
material of the skin surrounding the recess being displaced by the screw
Implementation Method 2
engaging the bore of the fixed structure, it finds a secure hold there so that the electrical contact between the screw and the conductive skin is not compromised by forces acting on the screw or the wall
Implementation Method 3
The recess preferably has a serrated edge, since the serrations can be deformed much more easily by the screw than, for example, an essentially straight edge
Data Source
Figure 1
Figure 2~3
AI summary
Disclosed is a housing for an electric appliance, comprising a wall (1) with an electrically insulating solid structure (3) and an electrically conductive skin (8) that is fastened to the structure (3), an electrically conductive support (2), and at least one screw (17) which engages into a bore (7) of the structure (3) and keeps the support (2) pressed against the wall (1). The screw (17) extends through a recess (13) of the skin (8). Material of the skin (8) that surrounds said recess (13) is displaced by the screw (17).