Dual-Thread Curtain Wall Screw for Thermal Expansion Retention
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Solution Overview
Problem
Existing methods for fixing curtain wall profiles to building structures, such as concrete or breeze block walls, face challenges in ensuring secure retention while allowing for thermal expansion due to differing expansion coefficients between materials like aluminum and concrete, often resulting in poor holding force and difficulty in controlling the distance between screw components.
Innovation Solution
A screw with a dual-thread design, featuring a first thread of larger diameter and a second thread of smaller diameter that extends towards the head, allowing for a clear distance that accommodates the profile and connecting part thicknesses, ensuring secure engagement and allowing for expansion, with a self-drilling capability and hexagonal socket for ease of use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a screw with a smooth part and sharp stop is used to hold the connecting piece and profile, then the profile is retained, but the distance between the head and sharp stop is difficult to control, resulting in poor holding force
Solution Approach 1:
The invention changes the geometric parameters of the screw thread by introducing a dual-thread system with different pitch and diameter characteristics. The first thread has a larger pitch for rapid engagement, while the second thread has a smaller pitch for precise positioning and controlled engagement, thereby achieving both strong holding force and precise distance control without requiring complex manufacturing tolerances.
Solution Approach 2:
The screw thread is segmented into two distinct zones with different thread characteristics. The first threaded zone has a larger pitch for initial engagement and rapid advancement, while the second threaded zone has a smaller pitch for fine adjustment and precise positioning. This segmentation allows the screw to perform multiple functions in sequence, resolving the contradiction between strong engagement and precise control.
2Adaptability or versatility
If a reduced diameter thread near the screw head is used to allow expansion, then the profile can expand relative to the structure, but the holding force is compromised
Solution Approach 1:
The dual-thread design creates a dynamic engagement system where the first thread provides initial strong engagement for secure mounting, while the second thread with smaller diameter and pitch allows for controlled movement and expansion. The transition between the two thread zones enables the connection to adapt to thermal expansion while maintaining holding force through the combined action of both threads.
Solution Approach 2:
Different portions of the screw thread are given different properties: the first threaded zone has larger diameter and pitch for strong engagement and structural support, while the second threaded zone has smaller diameter and pitch for allowing expansion and movement. This local differentiation of thread properties resolves the contradiction between maintaining holding force and allowing expansion.
3Adaptability or versatility
If a functional clearance is provided on the smooth part to allow expansion, then the profile can move, but the connecting piece and profile are poorly held together
Solution Approach 1:
The invention extracts the expansion function from the smooth part clearance approach and implements it through the dual-thread mechanism. The second thread with smaller diameter creates the necessary clearance and movement capability inherently, while the first thread maintains strong engagement. This separates the expansion function from the retention function, allowing both to coexist without compromise.
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 dual-thread screw design provides a secure and adjustable fixing system that allows for vertical movement and expansion of the metal frame relative to the building structure, ensuring effective retention and accommodating manufacturing tolerances, thus addressing the issue of differing expansion coefficients.
Implementation Method 1
a screw (1) for fixing a profile (2) of a metal framework to a part (3) intended to connect this profile to a structure of a building
Implementation Method 2
Such a screw is advantageously a self-drilling screw
Data Source
Figure 1~2
AI summary
The invention relates to a screw (1) for attaching a profile (2) of a curtain wall with a piece (3) for connecting to a structure of a building, comprising a first thread (11) and a second thread (12) having a diameter D12 smaller than the diameter D11 of the first thread, the screw comprising a first area (13) where both threads (11, 12) coexist, and a second area (14), located between the first area (13) and the head (5) of the screw, where only the second thread remains, so that the second thread extends beyond the first thread towards the head. The invention also relates to an associated attachment method.