Grinding Spindle Eccentric Shaft Oscillation Mechanism

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Solution Overview

Problem

Existing grinding units lack a simple and robust design with minimal installation space, limiting their versatility and effectiveness in processing large-area surfaces such as wood or wood substitutes.

Innovation Solution

A grinding unit with a torsionally rigid and longitudinally displaceable eccentric shaft mounted on the grinding spindle, featuring a spring-loaded sanding disc that moves on a circular path with minimal rotation relative to the spindle, allowing for efficient processing of large surfaces using interchangeable sanding discs or brushes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a traditional grinding unit design is used, then the structure may be complex or require large installation space, but the invention achieves a simple and robust design with small installation space

Engineering Contradiction:
Improvedesign simplicityVSAvoidrobustness
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The grinding unit is divided into separate functional modules: the eccentric shaft assembly, the sanding plate assembly, and the mounting interface. This segmentation allows each component to be optimized independently while maintaining overall simplicity and robustness.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The eccentric shaft design serves multiple functions: it provides the oscillating motion, supports the sanding plate, and interfaces with the grinding spindle. This multi-functionality reduces the number of separate components needed, achieving simplicity without sacrificing reliability.

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Ease of operation

If the sanding disc is freely movable in at least one direction of rotation relative to the grinding spindle, then the abrasive moves on a circular path with little or no rotation of its own, but this requires precise control of the eccentric shaft

Engineering Contradiction:
Improvecontact pressure controlVSAvoideccentric shaft control
Core Design Contradiction:
Ease of operationVSDevice complexity

Solution Approach 1:

The sanding plate is made freely movable relative to the grinding spindle through the eccentric shaft mechanism, allowing dynamic adjustment of the abrasive's circular path. This dynamic design enables precise contact pressure control while the eccentric shaft handles the rotational control automatically.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The eccentric shaft self-generates the oscillating motion and controls the sanding plate's movement without requiring external control systems. The mechanism uses the spindle's rotation to automatically create the desired circular path, reducing control complexity.

Inventive Principle:
Principle #25Self-service

3Manufacturing precision

If spring elements are used to press the grinding unit against the workpiece surface, then precise contact pressure is achieved, but the device complexity increases

Engineering Contradiction:
Improvecontact pressure precisionVSAvoidspring element assembly
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The spring elements are integrated into the existing structure, using the weight of the eccentric shaft and sanding plate assembly to provide the contact pressure. This self-service approach achieves precise contact pressure without requiring separate complex pressure control mechanisms.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The contact pressure is controlled by adjusting the spring element stiffness and pre-load, which are straightforward parameter changes rather than complex control systems. This allows precise pressure control while keeping the device simple.

Inventive Principle:
Principle #35Parameter changes

4Productivity

If the eccentric shaft is made torsionally rigid and longitudinally displaceable, then the grinding unit can process large-area surfaces efficiently, but the shaft design becomes more complex

Engineering Contradiction:
Improveprocessing efficiencyVSAvoideccentric shaft design
Core Design Contradiction:
ProductivityVSDevice complexity

Solution Approach 1:

The eccentric shaft is designed with segmented structural features that provide torsional rigidity in the critical regions while allowing longitudinal displacement. This segmentation enables efficient processing of large surfaces without requiring an entirely complex shaft design.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The eccentric shaft may use composite construction or material combinations that provide the required torsional rigidity and longitudinal displacability. This approach achieves high productivity while keeping the shaft design manageable through material selection rather than complex geometry.

Inventive Principle:
Principle #40Composite materials

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 enables efficient processing of large-area surfaces with precise contact pressure and reduced rotation, enhancing the grinding unit's versatility and effectiveness for applications like woodworking, while maintaining a compact design.

Implementation Method 1

The tool is pressed against the workpiece surface to be processed by spring elements arranged in the grinding unit. For example, there are spring elements, e.g. disc springs, which are combined into stacks or packages.

Methodology Applied
Scientific EffectSpring: Spring

Implementation Method 2

an electric motor in a housing causes an oscillating movement of a grinding disk covered with an abrasive by means of an eccentric shaft

Methodology Applied
Scientific EffectEccentric motion: Eccentric

Implementation Method 3

the sanding plate is suspended from the housing in such a way that it can oscillate transversely to the eccentric shaft. The center of the sanding disc is supported on the eccentric pin by means of a roller bearing.

Methodology Applied
Scientific EffectRoller bearing: Roller

Implementation Method 4

a grinding unit with an eccentric shaft arranged in a grinding spindle for supporting a grinding disk carrying an abrasive

Methodology Applied
Scientific EffectFriction: Friction

Implementation Method 5

the abrasive moves on a circular path with little or no rotation of its own in relation to the grinding spindle

Methodology Applied
Scientific EffectAbrasion: Abrasion

Data Source

PatentEP2529887B1Grinding tool with an eccentric shaft in a grinding spindle
Publication Date: 2015.12.16 BENZ GMBH
  • EP2529887B1 patent drawingFigure 1
  • EP2529887B1 patent drawingFigure 2
  • EP2529887B1 patent drawingFigure 3

AI summary

The grinding unit has a grinding spindle (10) that is arranged on the eccentric shaft (50), and a grinding structure (170) for holding the grinding wheel (140). A rolling bearing is supported on free end of eccentric shaft through grinding disc housing, in opposite to rotation direction of spindle. The eccentric shaft is equipped with balancing portions. A freewheel is arranged between eccentric shaft and grinding spindle.