Weld Nut With Integrated Retaining Element
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Solution Overview
Problem
The existing methods for attaching airbag cushions to vehicle body parts using weld nuts are costly due to the need for a plastic element to hold the screw captive, and they increase installation space.
Innovation Solution
A weld nut design that integrates a retaining element in the head part, allowing captive screw fixation without a plastic element, using a self-tapping screw that forms its own thread, eliminating the need for internal threads and reducing manufacturing costs, while enhancing clamping and alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a plastic element is applied to the screw to hold it captive in the nut, then the screw is securely retained, but the production cost increases and the installation space increases
Solution Approach 1:
The retaining element is integrated directly into the nut structure, merging the retention function with the nut body. This eliminates the need for separate plastic elements on screws, reducing production costs while maintaining secure screw retention through the integrated retaining element with its retaining opening and engagement geometry
Solution Approach 2:
The retention function is extracted from the screw (by removing the need for plastic elements on screws) and transferred to the nut structure. The retaining element in the nut actively captures the screw, reversing the conventional approach where the screw would need modification to achieve retention
2Reliability
If a plastic element is applied to the screw to hold it captive, then the screw is securely retained, but the screw length increases which increases installation space
Solution Approach 1:
The retention function is merged into the nut structure through the integrated retaining element, eliminating the need for extended screw length with attached plastic elements. The screw remains standard length while the retaining element provides capture functionality through its opening and engagement surfaces
3Ease of operation
If internal threads are provided in the nut, then screws can be easily inserted, but the manufacturing cost increases and the risk of cross-threading increases
Solution Approach 1:
Instead of pre-formed internal threads requiring expensive manufacturing, the self-tapping screw performs the thread-cutting function itself during installation. The screw's own geometry and cutting edges enable it to create its own mating thread in the through-hole, eliminating the need for pre-threaded holes and reducing manufacturing complexity
Solution Approach 2:
Rather than the nut providing the thread (conventional approach), the screw provides the thread through self-tapping. This inversion of the threading function eliminates the need for internal threads in the nut, reducing manufacturing cost while maintaining easy insertion through the self-aligning geometry of the retaining element
4Ease of operation
If internal threads are provided in the nut, then screws can be easily inserted, but the risk of cross-threading increases
Solution Approach 1:
The self-tapping screw creates its own thread with precise geometry controlled by the screw's own cutting edges and tolerance specifications. This self-formed thread ensures proper alignment and reduces cross-threading risk compared to pre-formed threads in the nut, while the retaining element's geometry provides additional alignment guidance during insertion
Data Source
Figure 1
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AI summary
The nut has a head structure (2) and a shaft structure (3) which is formed on the head structure. A through-hole (4) is formed through the head structure and the shaft structure. The through-hole is formed with an enlarged diameter in the area of the head structure. A retainer, into which a hollow cylindrical retaining ring (5) is introduced in order to captively fix the end of a screw (6), is formed. The hollow cylindrical retaining ring is made of plastic or metal sheet.