Eccentric Locknut Taper Geometry for Uniform Anti-Loosening Force

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional Hardlock Nuts and Hardlock Set Screws (HLS) exhibit a powerful anti-loosening effect due to an eccentric fit between their protrusion and recess, but this design leads to a large gap between the nuts upon tightening, causing stress concentration and making it difficult to disperse forces uniformly.

Innovation Solution

The anti-loosening device features a first threaded member with a protrusion having a tapered outer peripheral surface and a second threaded member with a recess having a tapered inner peripheral surface. The protrusion and recess are designed to establish an eccentric fit, where the tapered surfaces interfere to produce pressing forces, while a gap between the distal-end outer peripheral surface of the protrusion and the closer-to-bottom inner peripheral surface of the recess allows for minimized inclination of the threaded members.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the protrusion and recess are designed with tapered surfaces to produce pressing forces through eccentric fit, then the anti-loosening effect is enhanced, but the gap between the nuts increases and forces are not dispersed uniformly

Engineering Contradiction:

Improveanti-loosening effectVSAvoiduniform force distribution

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The protrusion is divided into two functional zones: a tapered outer peripheral surface portion for generating pressing forces through eccentric fit, and a distal-end outer peripheral surface portion with a gap from the recess bottom that prevents stress concentration. This segmentation allows the pressing forces to be dispersed more uniformly along the axial direction while maintaining the anti-loosening effect.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different portions of the protrusion are given different geometric properties: the tapered portion (with predetermined taper angle) provides the wedge effect for anti-loosening, while the distal-end portion (with larger gap) reduces stress concentration. This local differentiation of geometric quality enables simultaneous achievement of pressing force generation and uniform force distribution.

Inventive Principle:

Principle #3Local quality

2Reliability

If the protrusion and recess are designed with tapered surfaces to produce pressing forces through eccentric fit, then the anti-loosening effect is enhanced, but the gap between the nuts increases

Engineering Contradiction:

Improveanti-loosening effectVSAvoidgap between nuts

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

3Reliability

If the outer peripheral surface of the protrusion is made eccentric from the threaded hole, then the eccentric fit is achieved, but the manufacturing complexity increases

Engineering Contradiction:

Improveeccentric fitVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The protrusion is designed with asymmetric geometry where the outer peripheral surface is eccentric relative to the threaded hole axis. This intentional asymmetry creates the necessary eccentric fit condition while the specific configuration (tapered portion plus distal-end portion) facilitates manufacturing by providing clear geometric definitions for machining operations.

Inventive Principle:

Principle #4Asymmetry

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

This design minimizes the inclination of the first threaded member relative to the second, efficiently dispersing pressing forces radially and enhancing the anti-loosening effect while reducing the gap between the nuts, thus improving construction management.

Implementation Method 1

the threaded shaft S and nuts 110, 120 are in such a stress state as if a wedge had been hammered between the shaft and the nuts, and this wedge effect enables the Hardlock Nut to exhibit a powerful anti-loosening effect

Methodology Applied

Scientific EffectWedge effect: Wedge

Implementation Method 2

the outer peripheral surface of the protrusion 112 and the inner peripheral surface of the recess 122 interfere with each other along part of their circumference so as to produce pressing forces

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS12221994B2Loosening prevention device

Publication Date: 2025.02.11 HARD LOCK IND CO LTD

AI summary

An object of the present invention is to provide an anti-loosening device that exhibits its anti-loosening effect by means of an eccentric fit between a protrusion 12 of a nut 10 and a recess 22 in a nut 20, wherein the inclination of the nut 20 relative to the nut 10 when they have been tightened is minimized. The outer peripheral surface of the protrusion 12 and the inner peripheral surface of the recess 22 are constructed in such a manner that, with the nuts screwed to a threaded shaft S and an eccentric fit established between the protrusion 12 of the nut 10 and the recess 22 in the nut 20, the tapered outer peripheral surface portion 12a of the protrusion 12 interferes with the tapered inner peripheral surface portion 22a of the recess 22 along part of the circumference while a gap is formed between the distal-end outer peripheral surface portion 12b of the protrusion 12 and the closer-to-bottom inner peripheral surface portion 22b of the recess 22 along the entire circumference.