Thread Rolling Screw Profile Geometry for Anchor Thread Formation
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Solution Overview
Problem
Existing high performance thread rolling screws face challenges in efficiently forming mating nut threads in unthreaded ductile material anchors with existing thread profile geometries, which often result in high initial thread forming torque and potential cross-threading issues during screw removal and re-insertion.
Innovation Solution
A novel screw thread profile geometry comprising three defined zones: a central trapezoidal section (ZONE 'A'), a parabolic tip section (ZONE 'B'), and a hyperbolic root section (ZONE 'C'), which work together to reduce initial thread forming torque and prevent cross-threading by controlling material flow and thread formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional thread profile geometries are used in high performance thread rolling screws, then the screw can form mating nut threads in unthreaded ductile material anchors, but the initial thread forming torque is high and cross-threading issues occur during screw removal and re-insertion
Solution Approach 1:
The thread profile is divided into three distinct zones (A, B, and C) along the thread length, with each zone having a specific geometric shape and function. Zone A (trapezoidal) handles the primary thread forming, Zone B (parabolic) reduces initial torque and guides material flow, and Zone C (hyperbolic) prevents cross-threading. This segmentation allows each zone to optimize its function while working together to solve the torque and reliability contradiction.
Solution Approach 2:
Different sections of the thread profile are given different geometric qualities tailored to their specific functions. The parabolic curve in Zone B provides gradual material displacement for low initial torque, while the hyperbolic curve in Zone C creates a self-centering effect to prevent cross-threading. This local differentiation of geometric properties allows the thread profile to address multiple problems simultaneously at different locations along the thread.
2Ease of operation
If conventional thread profile geometries are used, then thread formation can occur, but cross-threading issues arise during screw removal and re-insertion
Solution Approach 1:
Zone B (parabolic section) performs a preliminary action by gradually guiding the ductile material flow during initial insertion, creating a smooth path before the main thread forming action in Zone A. This preliminary material guidance prevents misalignment and cross-threading before they can occur, ensuring reliable thread formation during subsequent insertions after removal.
Solution Approach 2:
The use of curved geometric profiles (parabolic in Zone B, hyperbolic in Zone C) instead of straight or angular transitions creates smooth material flow paths. The parabolic curve in Zone B acts as a gradual transition that centers the screw and guides material, while the hyperbolic curve in Zone C provides a self-centering effect that prevents cross-threading during removal and re-insertion operations.
3Ease of manufacture
If standard thread profiles are used, then the design is simple, but material flow control during thread formation is poor
Solution Approach 1:
The thread profile parameters (geometric shape, curvature radius, transition angles) are specifically optimized to control material flow. The parabolic Zone B uses a specific curvature that gradually increases from the tip, and the hyperbolic Zone C uses a curvature that prevents material snagging. These parameter optimizations enable precise control of ductile material flow during thread rolling while maintaining manufacturability through standard machining processes.
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 novel thread profile design reduces initial thread forming torque, prevents cross-threading, and enhances the durability of the screw by ensuring controlled nut thread formation and improved material flow, thereby improving the assembly process and screw performance.
Implementation Method 1
the thread helix angle will cause the relative axial forward movement, of the screw/bolt, into the anchor. This rotation and relative axial movement will be the prime mover in developing the nut thread that has mating contact with the screw/bolt thread
Data Source
Figure 1
Figure 2~3
AI summary
The present invention provides a screw/bolt thread profile geometry that is particularly suited to forming a mating nut thread when the screw is inserted in to a plain diameter hole, in the anchor and rotated in a manner by which the thread helix angle will cause the relative axial forward movement, of the screw/bolt, into the anchor. This rotation and relative axial movement will be the prime mover in developing the nut thread that has mating contact with the screw/bolt thread.