Screw with Displacement Tip for Sandwich Panel Fastening
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Solution Overview
Problem
Existing fastening methods for sandwich panels require pre-drilling or complex and expensive double-start threads to secure screws against reverse rotation, lacking a simple and cost-effective solution for achieving high tightening and shearing forces without delamination.
Innovation Solution
A screw design with a thread that runs into a displacement tip and an unthreaded shank section between the thread and screw head, where the unthreaded shank section's length is optimized to ensure secure engagement and prevent delamination, allowing the screw to be seated with minimal play and providing stability through the restoring force of the layer stack thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thread ends axially in a point (conventional design), then the screw can be inserted into a pilot hole, but the security against turning back is insufficient without a non-threaded shank section
Solution Approach 1:
The thread ends in an asymmetrically angled portion that slopes away from the head, creating a geometric lock that prevents reverse rotation. This asymmetric geometry engages with the material in a way that allows insertion but resists extraction, providing security against turning back without requiring a separate non-threaded shank section.
Solution Approach 2:
Instead of preventing reverse rotation by eliminating the thread (creating a non-threaded section), the invention inverts the approach by designing the thread end itself to have anti-loosening functionality through its angled geometry. The thread end is designed to actively engage and lock rather than passively terminate.
2Reliability
If double-start threads are used to ensure security against turning back, then reliability improves, but manufacturing complexity and cost increase
Solution Approach 1:
The invention uses a simple single-start thread with an angled end portion that can be manufactured using conventional single-start threading processes. This avoids the need for complex double-start threading while achieving the same anti-loosening effect, significantly reducing manufacturing complexity and cost.
3Strength
If the unthreaded shank section is too short, then the screw has insufficient engagement length, but if too long, then the screw has excessive play
Solution Approach 1:
The angled thread end automatically adjusts to the material thickness during insertion. As the screw is driven in, the angled portion engages the material and self-regulates the effective engagement length based on the actual stack thickness, eliminating the need for precise pre-determination of unthreaded section length and reducing screw play.
4Force
If a screw with thread running all the way to the top is used, then tightening force is maximized, but reverse rotation cannot be prevented without additional features
Solution Approach 1:
The invention merges the functions of maximum thread engagement for tightening force and reverse rotation prevention into a single integrated feature: the angled thread end. This design allows the thread to run substantially the full length of the shank for maximum engagement while the angled termination provides inherent anti-loosening capability, combining both functions in one structural element.
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 enables secure fastening without pre-drilling, maintaining stability and preventing reverse rotation, while allowing for high tightening and shearing forces, and is suitable for various applications including outdoor use with austenitic materials.
Implementation Method 1
at least the layer of the stack of layers furthest away from the screw head being deformed in the screwing-in direction, so that a thickness Dp of the stack of layers is increased in an area immediately around the screw
Implementation Method 2
providing stability through the restoring force of the layer stack thickness
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to the production of a securing arrangement (10) with a layer packet (12, 14, 16) and a screw (18). The screw (18) has a screw head (20), a shaft (24), a thread (26) which runs into an displacement tip (22), and a thread-free shaft portion (28). The method has the following steps: - rotating the screw (18) into the layer packet (12, 14, 16), the packet (12, 14, 16) layer (14) furthest away from the screw head (20) being deformed in the screw-in direction such that a thickness Dp of the layer packet (12, 14, 16) is increased in a region about the screw (18), and - continuing the rotation of the screw (18) until the screw head (20) strikes the layer packet, at which point a maximum layer packet thickness Dp, max is reached and the length LF of the thread-free shaft portion (28) is maximally 10% smaller and maximally 30% larger than the maximum layer packet thickness Dp, max.