Screw Anchor with Dual Threads for Wood-Concrete Fastening
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Solution Overview
Problem
Conventional screw anchors for fastening wooden components to concrete or masonry face limitations in tensile, bending, and transverse load capacity, often requiring additional components like metal washers and dowels to manage shear loads effectively, and are costly and aesthetically unappealing.
Innovation Solution
A single-part screw anchor with a wood thread section and a concrete thread section connected by an unthreaded shank, featuring a conical head and a push-through design, where the wood thread pitch is slightly smaller than the concrete thread pitch, allowing for increased tensile and transverse load capacity without the need for metal washers or dowels, and enabling full embedding in the wooden component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal washers are inserted between the anchor head and wooden component to increase tensile load capacity, then the tensile load that can be absorbed is improved, but the device complexity and assembly cost increase
Solution Approach 1:
The patent combines the anchor head and the tensile load transfer function into a single integrated component. The conical head with bearing surface directly transfers tensile loads to the wooden component through bearing stress, eliminating the need for separate metal washers. This merging of functions reduces device complexity while maintaining or improving tensile load capacity.
2Strength
If dowels of special design are introduced into the wooden component to relieve bending load on the anchor, then the transverse load capacity is improved, but the device complexity and assembly cost increase
Solution Approach 1:
The patent integrates the shear load transfer function directly into the anchor shaft. The threaded section of the anchor engages with the wooden component to transfer shear loads through thread friction and bearing stress, eliminating the need for separate dowels. This integration reduces device complexity while improving transverse load capacity.
Solution Approach 2:
The patent divides the anchor into functionally distinct sections: a threaded section for shear load transfer and an unthreaded shank for tensile load transfer. This segmentation allows each section to optimize its performance for specific load types without requiring additional components.
3Adaptability or versatility
If conventional anchors are used with large wooden component thicknesses, then the anchor can accommodate thick components, but the bending stress on the anchor increases and transverse load capacity decreases
Solution Approach 1:
The patent segments the anchor into a threaded section for shear load transfer and an unthreaded shank for tensile load transfer. This segmentation allows the threaded section to engage deeply in thick wooden components, providing sufficient shear load capacity without subjecting the entire anchor to excessive bending stress.
Solution Approach 2:
The patent applies different structural characteristics to different parts of the anchor: the threaded section has high engagement area for shear loads, while the unthreaded shank provides a smooth bearing surface for tensile loads. This local optimization allows the anchor to handle both thick components and high transverse loads effectively.
4Strength
If steel connectors are attached to the outside of concrete with anchors and fastened to wood with nails or screws, then the connection strength is improved, but the assembly cost and visual appearance worsen
Solution Approach 1:
The patent combines multiple fastening functions into a single anchor component that simultaneously anchors to concrete and fastens to wood. The anchor features a concrete-threaded section for concrete anchoring and a wood-threaded section for timber fastening, eliminating the need for separate steel connectors, anchors, and fasteners. This reduces assembly cost and simplifies installation while maintaining connection strength.
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 solution significantly enhances tensile and transverse load-bearing capabilities, reduces bending stress, and simplifies manufacturing, while being more versatile and aesthetically preferable by eliminating the need for additional components and allowing for a shorter overall length, thus improving the connection's performance and appearance.
Implementation Method 1
The tensile load is transferred from the wooden component to the anchor via its head support, and the transverse loads are transferred via bearing stress or pressure along the smooth shaft of the anchor in the wooden component.
Implementation Method 2
A screw anchor has a threaded section with a concrete thread for screwing directly into concrete. This threaded section is followed by an unthreaded shank, which penetrates the wooden component
Data Source
Figure 1~7
AI summary
The invention relates to a screw anchor for fixing wood components to concrete or masonry. Said anchor has a shaft (1) comprising a first threaded section (2) with a wood screw thread (6) for screwing into wood, and a second threaded section (3) with a concrete thread (7) for screwing into concrete, the pitch (P2) of the wood screw thread being equal to, or slightly smaller than, the pitch (P1) of the concrete thread (7).