Multi-stepped Tool Bushing for Breaking Hammer Maintenance

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Solution Overview

Problem

The existing solutions for mounting and dismounting tool bushings in breaking hammers are time-consuming and laborious, often requiring extensive dismantling and are not feasible in field conditions, leading to wear and deformation of the lower tool bushing due to friction locking and interference fitting.

Innovation Solution

A multi-stepped tool bushing with increasing diameters and corresponding multi-shouldered configuration that utilizes friction locking between the bushing and housing, allowing for easier mounting and dismounting with shorter axial lengths, and includes features like alignment grooves and lubricating grooves to facilitate maintenance and prevent impurities.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If friction locking and interference fitting are used to secure the tool bushing, then the bushing is firmly retained in the housing, but the mounting and dismounting process becomes time-consuming and laborious

Engineering Contradiction:

Improveretention of tool bushingVSAvoidmounting and dismounting time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The tool bushing is divided into multiple cylindrical sections with different diameters along its axial length, creating a multi-stepped configuration. This segmentation allows the bushing to engage with corresponding stepped surfaces in the housing, distributing the retention force across multiple friction locking zones while enabling controlled disengagement through axial movement.

Inventive Principle:

Principle #1Segmentation

2Reliability

If interference fitting is used to lock the bushing, then the bushing is securely fastened, but extensive dismantling measures and tooling are required for replacement

Engineering Contradiction:

Improvefastening securityVSAvoiddismantling requirements

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The bushing is segmented into stepped cylindrical sections that correspond to stepped surfaces in the housing. This creates multiple interference fitting zones along the axial direction, providing secure fastening while allowing the bushing to be removed by applying axial force to overcome the stepped retention features without requiring complex dismantling procedures.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of using a single complex interference fit requiring special tooling, the design inverts the approach by using multiple simpler friction locking zones created by stepped surfaces. The bushing is retained through distributed friction across multiple contact areas, allowing removal by standard axial pulling forces without specialized equipment.

Inventive Principle:

Principle #13The other way round (Inversion)

3Reliability

If a single large friction locking zone is used, then the bushing is securely retained, but the axial mounting length becomes long requiring great movement distances

Engineering Contradiction:

Improveretention forceVSAvoidaxial mounting length

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

The single large friction locking zone is segmented into multiple smaller friction locking zones along the axial direction. Each zone corresponds to a stepped surface engagement, distributing the total retention force across multiple contact areas. This reduces the axial mounting length required while maintaining the overall retention force through the cumulative effect of multiple zones.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The retention mechanism is extended from a single axial contact zone to multiple axial zones by introducing radial variations in diameter (stepped configuration). This dimensional change allows the same retention force to be achieved over a shorter axial distance by utilizing the radial dimension for force distribution.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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

Facilitates quick and efficient maintenance of breaking hammers by enabling easy removal and installation of the tool bushing in field conditions without extensive tooling, reduces wear, and extends the operating life by preventing impurities and moisture entry.

Implementation Method 1

fastening of the tool bushing is based at least partly to mutual sizes of an outer diameter of the bushing and an inner diameter of the bushing housing, whereby friction locking is utilized

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 2

The tool bushing is typically locked inside the bushing housing by using friction locking principles and interference fitting between the bushing and the bushing housing

Methodology Applied

Scientific EffectInterference fitting:

Data Source

PatentUS11478914B2Tool bushing, breaking hammer and mounting method

Publication Date: 2022.10.25 SANDVIK MINING & CONSTR OY

AI summary

A tool bushing of a breaking hammer, a tool bushing arrangement, a breaking hammer and a method of mounting a tool bushing of a breaking hammer are disclosed. The tool bushing is a sleeve-like piece having a multi-shouldered outer surface with three or more successive cylindrical portions. The cylindrical portions have different diameters that match with corresponding surfaces of a bushing housing when the tool bushing is mounted. Diameters of the bushing and the bushing housing are dimensioned so that friction forces are generated when the bushing is assembled.