Facade Panel Screw Geometry for Controlled Overwinding
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Solution Overview
Problem
Existing facade panel screws require multiple manufacturing steps, are costly, and can be difficult to handle due to the need for separate drilling and screwing operations, which can lead to incomplete fastening and material damage during installation.
Innovation Solution
A facade panel screw design featuring a cylindrical shaft with a threadless underhead section, an attenuated threaded section, and a stop collar, allowing controlled overwinding and reduced torque stress, which can be manufactured in a single operation and is economical to produce.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If self-tapping screws are used for fastening facade panels to aluminum substructures, then pre-drilling is avoided and installation is simplified, but the screw tip cannot generate sufficient compressive stress to form reliable threads in soft aluminum material
Solution Approach 1:
The screw tip is segmented into two functional zones: a first region with a conical compression element for generating compressive stress, and a second region with thread-forming elements. This segmentation allows the screw to first compress the aluminum material to increase its flow stress, then form reliable threads in the compressed zone, solving the problem of thread formation in soft aluminum without pre-drilling
Solution Approach 2:
The screw tip performs preliminary compression of the aluminum substructure material before thread formation. The conical compression element in the first region pre-compresses the material, increasing its flow stress and creating favorable conditions for subsequent thread formation in the second region, ensuring reliable fastening without pre-drilling
2Ease of manufacture
If conventional screw designs are used, then manufacturing is simple, but correction of incorrectly set screws is difficult and material damage can occur during installation
Solution Approach 1:
The screw features a controlled overwind capability where the thread pitch increases in the third region compared to the second region. This dynamic pitch change allows the screw to be over-turned during installation to release excessive tightening forces, prevent material damage, and enable correction of incorrectly set screws without compromising fastening reliability
Solution Approach 2:
The screw design allows for partial reversal of the fastening action through controlled overwinding. The increased pitch in the third region enables the screw to be back-driven a limited amount to release excessive compression forces, providing installation flexibility and correction capability while maintaining secure fastening
3Adaptability or versatility
If facade panels are pre-drilled with large holes for thermal expansion, then panel expansion is accommodated, but the screw receives virtually no guidance during the setting process
Solution Approach 1:
The screw shaft features a locally optimized guide section with specific dimensional tolerances and surface properties that provides precise guidance during insertion through the pre-drilled hole. This local quality enhancement in the guide section ensures accurate screw positioning and centered insertion, maintaining manufacturing precision despite the large hole size required for thermal expansion
Data Source
AI summary
A facade panel screw for the optimized fastening of facade panel elements to a substructure has a head having a very large diameter, a subsequent, essentially cylindrical shaft section (22) extending along a central longitudinal axis (A) and a subsequent tip region (23). The shaft section (22) includes, as viewed from the head, a threadless underhead section (24), a stop collar (25) and a threaded section (28). The thread in a first part (26) of the threaded section (28) subsequent to the stop collar (25) has an outer diameter Dr, which is attenuated compared to the thread in a second part (27) with outer diameter Dn, over several convolutions, so that Dr<Dn. This threaded section 26 allows a controlled overwinding of the facade panel screw in use. A corresponding fastening arrangement includes a facade panel, a substructure for transferring the load to a building surface and the facade panel screw.