Polylobular Press-Fit Fastener for Sheet Metal
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Solution Overview
Problem
Existing fastening elements for sheet metal parts often require excessive deformation, making them unsuitable for thicker sheets, and are limited in their application to thinner metals.
Innovation Solution
A press-fit component with a polylobular shaft and a flat bearing surface, featuring a punching edge and various knurling patterns, allowing for axial and rotational fixing through non-positive connections, and capable of punching holes in sheet metal, enabling secure attachment without significant deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing fastening elements are used to attach to sheet metal parts, then fixation is achieved, but excessive deformation of the sheet metal part is required which is unsuitable for thicker sheets
Solution Approach 1:
The shaft is divided into multiple lobes (at least three) creating a polylobular cross-section that segments the interaction with the hole wall, allowing mechanical interlocking without excessive deformation of thick sheet metal parts
Solution Approach 2:
The polylobular cross-section creates an asymmetric shape that does not perfectly match the circular hole, enabling positive connection through geometric interlocking rather than relying on deformation of the sheet metal
2Ease of manufacture
If a polylobular shaft with non-positive connection is used, then fixation without excessive deformation is achieved, but the connection strength may be reduced
Solution Approach 1:
The shaft features a punching edge with curved or rounded transitions between lobes that concentrate stress during insertion and create a wedging effect, enhancing connection strength without requiring deformation of the sheet metal part
Solution Approach 2:
The lobes are designed with specific geometric parameters (radius, angle, distribution) that optimize the balance between easy insertion and strong mechanical interlocking, allowing adaptation to different sheet metal thicknesses and material properties
3Productivity
If a punching edge is added to the shaft, then hole punching and press-fitting can be done in one operation, but the device complexity increases
Solution Approach 1:
The punching edge is integrated directly into the shaft geometry, merging the punching function and press-fitting function into a single component that performs both operations in one insertion motion, eliminating the need for separate punching and fastening steps
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
Enables secure attachment of the press-fit component to sheet metal parts without excessive deformation, suitable for both thinner and thicker metals, and allows for simultaneous hole punching and press-fitting in a single operation, enhancing the component's versatility and stability.
Implementation Method 1
Due to the polylobular cross-section of the shaft, fixing in the direction of rotation can take place through interaction with an opening exhibiting an identical shape
Implementation Method 2
the press-fit component exhibits a punching edge on the free end of its shaft. This is a sharp, edge. It is thereby possible to use the press-fit component as a punching component too
Implementation Method 3
the shaft exhibits knurling over at least part of its extension. This knurling may serve to improve the fixing of the press-fit component in the hole in the sheet metal
Data Source
AI summary
A press-fit component is proposed, which can be both press-fitted into an existing hole in a sheet metal component and also punched into sheet metal where there is no hole. The press-fit component exhibits a head with a bearing surface and a shaft which emanates from the bearing surface. The shaft has a trilobular cross-section and may be provided with knurling over at least part of its length. The shaft may be provided with a threaded through-hole. As a result of the trilobular form, the shaft and with it the press-fit element is secured against turning, without deformation of the sheet metal from a plane taking place during press-fitting.