Hardenable Washer Bolt Assembly to Prevent Nut Loosening

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Solution Overview

Problem

Existing bolt assemblies experience untimely loosening due to nut rotation, leading to a loss of preload and mechanical performance issues, particularly because washers made of deformable materials can adhere to threaded rods, making disassembly difficult.

Innovation Solution

A bolt design featuring a nut with recessed or projecting shapes and a washer made from a pasty material that hardens, with lugs or indentations to prevent rotation, and a second washer with internal ribs to contain the hardened material, ensuring high adhesion and preventing contact with the rod, thus maintaining preload.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a washer made of deformable material is used to prevent nut rotation, then the nut is locked in position, but the washer material adheres to the threaded rod making disassembly difficult

Engineering Contradiction:
Improvenut position stabilityVSAvoiddisassembly difficulty
Core Design Contradiction:
ReliabilityVSEase of repair

Solution Approach 1:

The system is divided into two separate washers: a first washer made of hardenable material that prevents nut rotation, and a second washer made of deformable material that prevents rod adhesion. This segmentation allows each component to perform its specific function without the negative effects of the other materials combining.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The second washer acts as an intermediary barrier between the deformable material and the threaded rod. By positioning the second washer between the first washer and the rod, it prevents the hardenable material from coming into contact with and adhering to the rod surface.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Strength

If a hardenable material is used to conform to nut shapes, then high adhesion is achieved, but the material may contact and adhere to the rod

Engineering Contradiction:
Improvewasher adhesionVSAvoidmaterial adhesion to rod
Core Design Contradiction:
StrengthVSObject-affected harmful factors

Solution Approach 1:

The second washer serves as a protective intermediary layer that prevents the hardenable material of the first washer from contacting the threaded rod. This intermediary barrier eliminates the harmful adhesion effect while preserving the beneficial adhesion properties of the hardenable material against the nut.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The function of preventing rod adhesion is extracted from the first washer and assigned to a dedicated second washer. This separation allows the first washer to focus on providing high adhesion and mechanical locking, while the second washer专门 handles the rod protection function.

Inventive Principle:
Principle #2Taking out (Extraction)

3Reliability

If the washer material is compressed between nut and contact face, then the material flows into hollow shapes to lock the nut, but the material may propagate into the through hole and contact the rod

Engineering Contradiction:
Improvenut locking capabilityVSAvoidmaterial propagation into through hole
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The second washer with its peripheral ribs acts as a physical barrier that intercepts and contains the compressed material within the through hole. The ribs prevent the material from flowing outward and contacting the rod, while still allowing the material to effectively fill and lock into the hollow shapes of the nut.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The second washer introduces local structural features (peripheral ribs) that create localized containment zones. These ribs are strategically positioned to control material flow paths, allowing material compression to effectively lock the nut while preventing unwanted propagation toward the rod.

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 solution effectively limits untimely unscrewing of the nut, maintains mechanical performance by preventing rotation, and allows for easy disassembly by preventing material contact with the rod.

Implementation Method 1

the first washer is made from a material configured to occupy a first pasty state allowing it to conform to each hollow or protruding shape of the nut during installation of the nut and a second solid state, after hardening of the material

Methodology Applied
Scientific EffectHardening:

Implementation Method 2

the material of the first washer is chosen so that the first washer has, after hardening, high adhesion with at least one of the surfaces in contact with its first and second transverse faces

Methodology Applied
Scientific EffectAdhesion: Adhesive

Data Source

PatentEP3859170B1Bolt comprising a nut and at least one washer obtained by hardening of a pasty material, method for installing said bolt and assembly comprising at least one such bolt
Publication Date: 2023.12.06 AIRBUS OPERATIONS (SAS)
  • EP3859170B1 patent drawingFigure 1~4
  • EP3859170B1 patent drawingFigure 5~7

AI summary

The invention relates to a bolt comprising a shank, a nut (22) screwing onto the shank and at least one first washer (36), characterized in that the nut (22) comprises, at the level of a terminal face (26.1) oriented towards the first washer (36), at least one hollow or protruding shape (32) and in that the first washer (36) is made from a material configured to occupy a first paste-like state enabling it to conform to each hollow or protruding shape (32) of the nut (22) when the nut (22) is put in place and a second solid state, after hardening of the material, in which the first washer (36) comprises, at the level of its surface oriented towards the nut (22), for each hollow or protruding shape (32) of the nut (22), a lug or a recess (42). This solution avoids unscrewing the nut (22).The invention also relates to a method for mounting such a bolt and to an assembly comprising at least one such bolt.