Asymmetric Thread Screw Anchor for Concrete
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Solution Overview
Problem
Conventional screw anchors with buttress threads are less effective in substrates with low tensile strength, such as concrete, as they fail to provide sufficient engagement and pull-out resistance due to their design.
Innovation Solution
A screw anchor design featuring threads with a head side surface angle of 30° to 40° and a tip side surface angle of 15° to 25°, creating a wedge configuration that leverages the compressive strength of concrete and reduces torque and displacement, along with centering threads for improved engagement and penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If buttress threads are used in screw anchors, then axial thrust resistance is improved, but effectiveness in low tensile strength substrates such as concrete deteriorates
Solution Approach 1:
The patent applies asymmetry by designing threads with different angles on opposite sides: the head side surface has an angle of 30°-40° while the tip side surface has an angle of 15°-25°. This asymmetric configuration allows the thread to effectively engage with concrete substrates by creating a wedge action that leverages concrete's compressive strength while maintaining reliability in low tensile strength materials.
Solution Approach 2:
The patent changes the geometric parameters of the thread profile by specifying precise angle ranges (head side surface: 30°-40°, tip side surface: 15°-25°). These parameter modifications optimize the thread's interaction with concrete, transforming the engagement mechanism to better suit low tensile strength substrates while maintaining axial thrust resistance.
2Ease of manufacture
If conventional thread profiles are used, then manufacturing simplicity is maintained, but pull-out resistance in concrete deteriorates
Solution Approach 1:
The patent modifies the thread geometry parameters within practical manufacturing ranges (30°-40° for head side, 15°-25° for tip side), maintaining ease of manufacture through standard machining capabilities while significantly improving pull-out resistance in concrete substrates through the optimized asymmetric wedge configuration.
3Strength
If higher engagement strength is achieved, then torque requirements and material displacement increase
Solution Approach 1:
The optimized thread angles (30°-40° head side, 15°-25° tip side) create an efficient wedge action that converts applied torque into axial engagement force more effectively. This parameter optimization achieves high engagement strength while minimizing the torque required and reducing concrete displacement during installation.
Data Source
AI summary
A screw anchor includes a body having a head end that extends to a tip end through an intermediate portion defining an axis of the screw anchor, and a plurality of threads extending along the intermediate portion. Each of the plurality of threads includes a head side surface having a first angle relative to an axis perpendicular to the axis of the screw, and a tip side surface having a second angle relative to the axis perpendicular to the axis of the screw. The first angle is between about 30° and about 40°, and the second angle is between about 15° and about 25°.