Self-Tapping Screw for Electrical Connection of Thick Metal Bodies
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Solution Overview
Problem
Existing screw connections are inadequate for reliable mechanical and electrical connections between thick-walled metal bodies, as they fail to secure the connection and are prone to corrosion, especially when used with coated surfaces.
Innovation Solution
A metal screw design with a screw head and shank featuring a contour section, thread-forming section, and constriction, where the screw shank produces internal threads in pilot holes by material deformation, creating fresh metal surfaces free of corrosion, and the constriction ensures mechanical engagement, eliminating the need for a nut and reducing corrosion risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional screw connection with nut is used for electrical connection of metal plates, then electrical connection is established, but the interface between nut thread and screw thread is subject to corrosion deteriorating electrical conduction
Solution Approach 1:
The invention extracts and eliminates the nut component from the screw connection system. By using a self-tapping screw that directly engages with the metal plate through thread formation, the corrosive thread-nut interface is completely removed, preventing corrosion-related deterioration of electrical conduction while maintaining reliable electrical connection.
Solution Approach 2:
The invention merges the functions of the screw and nut into a single self-tapping screw component. The screw head provides the electrical contact surface, while the screw shank with thread-forming capability directly engages the metal plate, eliminating the separate nut component and its associated corrosion issues.
2Reliability
If a flow-drilling screw is used for electrical connection of conductors to sheet metal, then electrical and mechanical connection is achieved, but the connection is not suitable for thick-walled metal bodies as the thread design does not pull the metal bodies together
Solution Approach 1:
The invention changes the thread design parameters to enable effective engagement with thick-walled metal bodies. The thread pitch, depth, and forming mechanism are optimized to create sufficient clamping force that pulls metal bodies together, unlike conventional flow-drilling screws that are designed for thin sheets. This allows the same screw type to reliably connect thick-walled bodies while maintaining electrical connection capability.
3Reliability
If a screw with nut and cutting rings is used for electrical connection of metal plates, then electrical connection is established on coated surfaces, but the device complexity increases and material costs increase
Solution Approach 1:
The invention removes the nut and separate cutting rings from the assembly, integrating all necessary functions into the self-tapping screw itself. The screw head with contact surface and the thread-forming shank replace the multi-component system, reducing device complexity while maintaining the ability to establish electrical connections on coated surfaces.
Solution Approach 2:
The invention combines the electrical contact function (screw head), the thread formation function (screw shank), and the clamping function (constriction) into a single integrated component. This merging eliminates the need for separate nuts and cutting rings, simplifying the overall device structure while achieving reliable electrical connection on coated metal surfaces.
4Ease of operation
If a conventional screw connection is used for thick-walled metal bodies, then the screw can be inserted, but the mechanical connection is not secure as the metal bodies are not pulled together
Solution Approach 1:
The invention modifies the screw geometry parameters, specifically adding a constriction between the head and shank. This constriction creates a mechanical leverage effect during tightening that generates sufficient clamping force to pull thick-walled metal bodies together, thereby securing the mechanical connection while maintaining ease of insertion and tightening operation.
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
The solution provides a secure mechanical connection and reliable electrical contact between thick-walled metal bodies while preventing corrosion, with the added benefit of reduced material and assembly costs, and the ability to connect thick-walled bodies without passing the screw through both.
Implementation Method 1
the thread of the self-tapping section of the screw producing an internal thread in the pilot hole of the first metal body by material deformation
Implementation Method 2
the constriction arranged between the contour section and the thread-forming section has an outer diameter that is smaller than the core diameter of the thread of the thread-forming section
Data Source
Figure 1~2a
Figure 2b~3
Figure 4~5
AI summary
The invention relates to an electrical connection between two thick-walled metal bodies, each provided with a pilot hole, by means of a metallic screw. The screw has a screw head and a shank adjoining it. In its operating state, the screw is positioned in the axially aligned pilot holes, with the first metal body and the second metal body arranged relative to the screw head. The object of the invention is therefore to provide a screw connection for the electrical connection of thick-walled metallic bodies, while also achieving a secure mechanical connection between these metallic bodies. Furthermore, the electrical connection achieved by the screw connection should be protected against corrosion.This task is solved by the screw shaft (6) having, starting from the screw head (5), a contour section (A), a thread-forming section (C) downstream of the contour section and a constriction (B) arranged between contour section (A) and thread-forming section (C).