Textured Stem Washer for Compact Bolt Shear Locking

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Solution Overview

Problem

Existing bolt systems face challenges in compact assemblies where access is limited, and are prone to slippage under shear forces, necessitating larger bolts that conflict with the trend towards smaller and more compact designs.

Innovation Solution

A combined washer comprising an annular disc with a central hole and a cylindrical stem with a textured exterior surface, which creates a mechanical lock and reduces shear forces acting on the bolt, allowing for the use of smaller bolts while maintaining necessary clamping forces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If larger bolts are used to generate more friction and prevent slippage under shear forces, then the bolt's ability to withstand shear forces is improved, but the assembly size increases and conflicts with the trend to make things smaller and more compact

Engineering Contradiction:
Improvebolt shear resistanceVSAvoidassembly size
Core Design Contradiction:
StrengthVSVolume of moving object

Solution Approach 1:

The invention divides the bolted joint system into two functional components: the bolt itself and a separate locking washer. The locking washer with its textured exterior surface creates a mechanical lock between the washer and the receiving part, while the bolt provides the clamping force. This segmentation allows the bolt to be smaller while still preventing slippage through the washer's locking mechanism.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The locking washer acts as an intermediary component between the bolt and the receiving part. It transfers and distributes the clamping force from the bolt while creating a mechanical lock through its textured surface that prevents slippage. This intermediary allows the use of smaller bolts while maintaining the necessary friction and locking capability.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Volume of moving object

If serration bolts are used to downsize bolts while maintaining clamping force, then bolt size is reduced, but access to both sides of the receiving part is required during assembly

Engineering Contradiction:
Improvebolt sizeVSAvoidassembly accessibility
Core Design Contradiction:
Volume of moving objectVSEase of operation

Solution Approach 1:

The invention separates the locking function from the fastening function by using a distinct locking washer component. This allows the bolt to be inserted and tightened from one side only, while the locking washer creates the mechanical lock on the other side, eliminating the need for access to both sides during assembly.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The locking washer serves as an intermediary that enables one-sided assembly. It is positioned on the far side of the receiving part, creating a mechanical lock that prevents slippage without requiring access to that side during the assembly process. The bolt can be fully assembled and locked from a single accessible side.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Volume of moving object

If the bolted joint is made more compact to reduce access space, then assembly compactness is improved, but it becomes difficult to access the bolt to loosen or tighten it

Engineering Contradiction:
Improveassembly compactnessVSAvoidbolt accessibility
Core Design Contradiction:
Volume of moving objectVSEase of operation

Solution Approach 1:

The invention segments the fastening system so that the locking function is handled by a separate washer component that does not interfere with bolt accessibility. The compact design is achieved through the washer's positioning and structure, while the bolt remains accessible for tightening and loosening operations.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The locking washer acts as an intermediary element that enables compact assembly design without compromising bolt accessibility. It creates the mechanical lock in a space-efficient manner while leaving the bolt head accessible for tool application during assembly and maintenance operations.

Inventive Principle:
Principle #24Intermediary (Mediator)

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 combined washer effectively minimizes or prevents slippage and reduces the size and weight of bolts, enhancing assembly accessibility and reducing material costs, while maintaining the required clamping force.

Implementation Method 1

the textured exterior surface creates friction or clamping forces between the combined washer and a surface of the receiving part

Methodology Applied
Scientific EffectFriction: Friction

Data Source

PatentEP4549761A1Combined washer with extra features for alignment
Publication Date: 2025.05.07 VOLVO CAR CORP
  • EP4549761A1 patent drawingFigure 1A~1C
  • EP4549761A1 patent drawingFigure 2A~2B
  • EP4549761A1 patent drawingFigure 2C~2D

AI summary

A combined washer comprising an annular disc with a central hole; and a cylindrical stem comprising a textured exterior surface and extending perpendicularly from the first side of the annular disc, wherein the textured exterior surface is configured to create a mechanical lock and avoid slipping.