Pair Nut Assembly for Vibration-Resistant Bolt Locking

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Solution Overview

Problem

Existing lock nuts require high production costs, complicate assembly, and are cumbersome to manage due to their complex structure, and nuts with slits lack ease of tightening.

Innovation Solution

A pair nut comprising a first nut and a second nut, both covered with a resin film, with their side surfaces aligned vertically and central axes matching the bolt's axis, allowing for integral securing and easy assembly, eliminating gaps between thread portions for enhanced frictional force.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a hard lock nut with eccentric fitting is used to prevent loosening, then the locking effect is improved, but the production cost and structural complexity increase

Engineering Contradiction:
Improvelocking effectVSAvoidstructural complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The lock nut is divided into two separate nuts (first nut and second nut) that work together as a pair, where each nut has a simpler individual structure but collectively provide the locking effect through their coordinated arrangement with aligned central axes

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The two nuts are combined into a pair that functions together, with their side surfaces aligned vertically and central axes matching the bolt's axis, creating a unified locking system that is more cost-effective and simpler than eccentric fitting designs

Inventive Principle:
Principle #5Merging (Combining)

2Reliability

If a hard lock nut with eccentric fitting is used to prevent loosening, then the locking effect is improved, but the assembly process becomes more complicated

Engineering Contradiction:
Improvelocking effectVSAvoidassembly ease
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The locking function is segmented into two separate nuts with identical central axes, allowing them to be assembled independently onto the bolt without the complex eccentric alignment required by single-lock nut designs

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The two nuts are designed to be assembled in a predetermined sequence onto the bolt, with the first nut followed by the second nut, both aligning to the same central axis, which simplifies the assembly process compared to eccentric fitting mechanisms

Inventive Principle:
Principle #10Preliminary action

3Ease of manufacture

If a nut with slits is used to simplify structure, then the production cost is reduced, but the ease of tightening is compromised

Engineering Contradiction:
Improveproduction costVSAvoidease of tightening
Core Design Contradiction:
Ease of manufactureVSEase of operation

Solution Approach 1:

The solution segments the single-slit nut design into two complete nuts without slits, maintaining structural integrity and ease of tightening while achieving cost-effectiveness through simplified individual nut construction and standardized manufacturing

Inventive Principle:
Principle #1Segmentation

4Ease of operation

If the central axes of the two nuts are aligned with the bolt axis, then the assembly is simplified, but gaps may form between the thread portions

Engineering Contradiction:
Improveassembly simplicityVSAvoidfrictional force
Core Design Contradiction:
Ease of operationVSReliability

Solution Approach 1:

The design incorporates local quality variations in the thread portions of the two nuts, with specific surface treatments or geometric modifications at the contact interfaces to eliminate gaps and enhance frictional force while maintaining aligned central axes for simplified assembly

Inventive Principle:
Principle #3Local quality

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 pair nut provides strong frictional force, preventing loosening from vibrations and simplifying assembly, while being cost-effective and easy to handle, thus enhancing attachment efficiency.

Implementation Method 1

A pair nut comprises a first nut and a second nut, both covered with a resin film... eliminating gaps between thread portions for enhanced frictional force

Methodology Applied
Scientific EffectFriction: Friction

Data Source

PatentEP4202240B1Pair nut and tightening method therefor
Publication Date: 2026.02.25 YAMASHITA TOMOKI
  • EP4202240B1 patent drawingFigure 1~2
  • EP4202240B1 patent drawingFigure 3
  • EP4202240B1 patent drawingFigure 4~5

AI summary

Provided is a pair nut comprising a first nut (400) and a second nut (500). The first nut (400) includes a nut main body (10) having a tapped hole (30) formed therein, a top surface (11) of the nut main body (10), a side surface (15) defining the top surface (11), and a bottom surface (13) of the nut main body (10) located opposite to the top surface (11), a central axis (C) of the tapped hole (30) of the first nut (400) matches a central axis (C) of a bolt (80) corresponding to the pair nut (600), the first nut (400) has a bottom opening (407) formed in the bottom surface (13) thereof, the bottom opening (407) having a diameter longer than a diameter of the tapped hole (30), a central axis (C1) of the bottom opening (407) extends while inclining with respect to the central axis (C) of the bolt (80) corresponding to the pair nut (600). The second nut (500) includes a nut main body (10) having a tapped hole (30) formed therein, a top surface (73) of the nut main body (10), a side surface (15) defining the top surface (73), and a bottom surface (75) of the nut main body (10) located opposite to the top surface (73). The second nut (500) includes a top protrusion (72) on the top surface (73) thereof. The top protrusion (72) corresponding to the bottom opening (407) of the first nut (400), and a central axis (C) of the tapped hole (30) formed in the top protrusion (72) and the nut main body (10) matches the central axis (C) of the bolt (80) corresponding to the pair nut (600).