Variable Thread Knurl Fastener for Low-Torque Penetration

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Solution Overview

Problem

Existing fasteners struggle to securely and efficiently bind materials, particularly in applications requiring reduced torque and improved penetration, such as in wood and composite materials.

Innovation Solution

A fastener design featuring a shank with varying thread angles and knurls, including serrated edges, which reduces torque requirements and enhances penetration by incorporating knurls and varying thread angles to improve engagement with the material.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a conventional uniform thread design is used, then the fastener structure is simple, but the penetration ability and torque reduction are insufficient

Engineering Contradiction:
Improvepenetration abilityVSAvoidthread structure complexity
Core Design Contradiction:
StrengthVSDevice complexity

Solution Approach 1:

The patent applies local quality by varying the thread angle along the length of the fastener. The lead portion has a first thread angle optimized for penetration, while the trailing portion has a second thread angle optimized for binding. This local differentiation allows each section to perform its specific function optimally without requiring complex additional components.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The thread structure is segmented into distinct portions with different thread angles. The lead portion and trailing portion are clearly divided, with each segment having optimized geometry for its specific function. This segmentation allows the fastener to achieve complex performance characteristics through simple geometric division rather than multiple components.

Inventive Principle:
Principle #1Segmentation

2Strength

If a conventional fastener design is used, then the installation torque is high, but the binding security is insufficient

Engineering Contradiction:
Improvebinding securityVSAvoidinstallation torque
Core Design Contradiction:
StrengthVSForce

Solution Approach 1:

The patent uses local quality by assigning different thread angles to different portions of the fastener. The lead portion with the first thread angle is optimized for penetration with reduced torque requirements, while the trailing portion with the second thread angle provides enhanced binding security. This local optimization resolves the contradiction between installation ease and binding strength.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent changes the thread angle parameter along the length of the fastener. By varying this geometric parameter from the lead portion to the trailing portion, the fastener achieves both reduced installation torque and improved binding security. The parameter change allows optimization of both installation and performance characteristics.

Inventive Principle:
Principle #35Parameter changes

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 fastener design significantly reduces installation torque and improves penetration, demonstrating enhanced performance in securing elements in wood and composite materials.

Implementation Method 1

at least a portion of the contiguous helical thread including a serrated edge. At least one knurl is positioned in the shaft within an area of the first thread angle

Methodology Applied
Scientific EffectFriction: Friction

Implementation Method 2

Multiple knurls may be provided. For example, a second knurl may be provided at a distance apart on the shank from the first knurl

Methodology Applied
Scientific EffectMechanical interlocking: Mechanical Fastener

Implementation Method 3

A first thread angle extending from and beginning at the tip and extending toward the second end, and a second thread angle. The first thread angle is greater than the second thread angle

Methodology Applied
Scientific EffectMechanical advantage: Mechanical Advantage

Data Source

PatentEP2978981B1Variable thread knurl fastener
Publication Date: 2026.01.07 SIMPSON STRONG TIE
  • EP2978981B1 patent drawingFigure 1
  • EP2978981B1 patent drawingFigure 2~3
  • EP2978981B1 patent drawingFigure 4~6

AI summary

A fastener 100 includes a shank 102 having a point 104 at a first end and a second, head end. A first portion 220 of a thread 112 is formed with a first thread angle and a second portion 225 of the thread is formed with a second thread angle. One or more knurls 114, 118 are provided in the shaft in the threaded or unthreaded regions of the fastener. The thread may be serrated or jagged over one or more portions of the fastener, including the area of the first thread angle.