Spacing Fastener Support Geometry for Stable Outer Shell Sealing
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Solution Overview
Problem
Existing spacing fasteners face issues with sealing damage due to flexible insulating materials under high wind pressure or settling processes, particularly with single-start under-head screw threads having increasing pitch, and their complex production processes.
Innovation Solution
A spacing fastener design featuring a support element spaced circumferentially from the under-head screw thread, providing an additional contact point for the outer shell, which reduces tilting and maintains even contact pressure, and can be easily produced through a pressing and rolling process with minimal material displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-start under-head screw thread with increasing pitch is used, then the fastener can be easily produced, but the sealing is damaged due to tilting of the outer shell
Solution Approach 1:
The under-head screw thread is divided into multiple independent thread starts (e.g., two-start thread) instead of a single continuous thread. This segmentation creates multiple contact points that distribute the load and reduce tilting moments on the outer shell, thereby improving sealing reliability while maintaining ease of production through standard threading processes
Solution Approach 2:
The pitch of the under-head screw thread is varied locally along the thread length, with different pitch values in different sections. This allows optimization of local contact characteristics to minimize tilting while maintaining overall manufacturability and sealing performance
2Reliability
If a double thread with large pitch is used to reduce tilting, then sealing is improved, but production becomes complex requiring material upset
Solution Approach 1:
The thread geometry parameters (pitch, number of starts, thread profile) are optimized to achieve the desired reduction in tilting without requiring complex production processes. By carefully selecting thread parameters, the fastener achieves improved sealing while maintaining compatibility with standard pressing and rolling production methods without excessive material upset
3Reliability
If the under-head screw thread pitch is increased to create contact points, then tilting is reduced, but the outer shell and substructure separate during screwing
Solution Approach 1:
The use of multiple thread starts creates distributed contact points along the thread engagement length. This segmentation allows the load to be distributed across multiple engagement points, reducing localized tilting moments while maintaining continuous structural integrity and preventing separation between the outer shell and substructure during the screwing process
Data Source
AI summary
A spacing fastener comprises a head and a shaft adjoining the head and ending with a tip. The shaft comprises an anchoring screw thread, an under-head screw thread closest to and ending near the head, and a non-threaded shaft portion therebetween. A support element at a distance circumferentially from the screw-thread end of under-head screw thread forms contact point (Au) therewith. In the region overlapping with under-head screw thread in top view, the support element is spaced apart therefrom and forms a contact point (As) for an outer shell lying between the head and under-head screw thread. The distance of contact point (As) from the head is greater than or equal to difference between the distance of contact point (Au) from the head and a tolerance distance of at most 15% of the major diameter of the under-head screw thread. The support element extends lengthwise over less than 150°.