Multi-Disc Grinder Housing With Recessed Dust Extraction Ducts

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Solution Overview

Problem

Existing hand-held power tools struggle with efficient dust extraction from multiple grinding wheels, leading to reduced airflow and increased pressure loss, which affects the tool's performance and user experience.

Innovation Solution

The design incorporates a housing part with recessed air ducts between grinding wheel receiving areas, allowing for low-loss air guidance and dust extraction. These air ducts are strategically positioned on the outer side of the housing, forming a guide structure that enhances airflow and reduces friction, enabling homogeneous dust extraction across all grinding wheels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If multiple grinding wheels are driven simultaneously, then productivity is improved, but dust extraction efficiency deteriorates due to reduced airflow and increased pressure loss

Engineering Contradiction:
Improvesimultaneous grinding capabilityVSAvoidairflow pressure loss
Core Design Contradiction:
ProductivityVSLoss of energy

Solution Approach 1:

The housing is divided into multiple independent air ducts, each serving a specific grinding wheel position. This segmentation allows each duct to maintain optimized airflow characteristics independent of other grinding operations, preventing the cumulative pressure loss that would occur in a shared exhaust system.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

Air ducts are positioned on the outer lateral surface of the housing rather than routing exhaust through the interior. This spatial reconfiguration creates dedicated external pathways for each grinding wheel's dust extraction, eliminating internal airflow interference and maintaining consistent suction efficiency across all wheels.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Productivity

If air ducts are positioned on the outer side of the housing, then dust extraction efficiency is improved, but device complexity increases

Engineering Contradiction:
Improvedust extraction efficiencyVSAvoidhousing structure complexity
Core Design Contradiction:
ProductivityVSDevice complexity

Solution Approach 1:

The air ducts are integrated directly into the housing's outer shell as recessed features rather than being separate attached components. This merging of the duct structure with the housing itself eliminates the need for additional fasteners, seals, or mounting mechanisms, reducing overall device complexity while maintaining extraction efficiency.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The housing structure serves dual functions: it provides mechanical protection for internal components and simultaneously acts as the air duct system for dust extraction. This multi-functionality eliminates the need for a separate duct system, simplifying the overall device architecture while achieving effective dust removal.

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

3Ease of operation

If recess depth increases from central region to edge, then homogeneous dust extraction is achieved, but manufacturing precision requirements increase

Engineering Contradiction:
Improvedust extraction uniformityVSAvoidrecess dimensional tolerance
Core Design Contradiction:
Ease of operationVSManufacturing precision

Solution Approach 1:

The recess depth is varied locally across different regions of the housing - deeper at the edges and shallower at the center. This local quality variation compensates for the natural decrease in airflow velocity at the periphery, ensuring uniform dust extraction across the entire grinding surface without requiring excessively tight manufacturing tolerances throughout.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The recess depth parameter is systematically changed across the housing surface to optimize airflow distribution. By increasing depth from center to edge, the design compensates for geometric airflow losses and maintains consistent suction efficiency, achieving homogeneous dust extraction through controlled parameter variation rather than uniform dimensions.

Inventive Principle:
Principle #35Parameter changes

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 achieves improved air guidance and dust extraction efficiency, reducing pressure loss and allowing for more effective aspiration of sanding dust. This results in a more compact and user-friendly tool design, capable of reaching narrow or hard-to-reach areas.

Implementation Method 1

The air duct serves to guide the air, in particular the low-loss air guidance of an exhaust air stream

Methodology Applied
Scientific EffectAir guidance:

Implementation Method 2

The cross-section between the housing part and the sanding plate is enlarged. The concave structure of the recess additionally reduces the friction of the air stream on the housing part

Methodology Applied
Scientific EffectPressure loss reduction: Pressure Drop

Data Source

PatentEP3677379B1Hand machine tool
Publication Date: 2025.06.18 ROBERT BOSCH GMBH
  • EP3677379B1 patent drawingFigure 1
  • EP3677379B1 patent drawingFigure 2
  • EP3677379B1 patent drawingFigure 3

AI summary

The invention relates to a hand-held power tool, in particular a grinder (10), for the simultaneous drive of several, preferably three, grinding discs (12, 14, 16), in particular tiltable, rotating and/or oscillating and/or randomly circularly driven, comprising at least one housing part (60) which has grinding disc receiving areas (102) and/or openings (100) in or through which grinding disc receptacles (56) and/or output shafts (40) for driving the grinding discs (12, 14, 16) are arranged. It is proposed that the at least one housing part (60) has a recess (108), in particular a concave recess (108), between at least two adjacent grinding disc receiving areas (102) and/or openings, wherein the recess (108) forms at least part of an air duct (120), in particular part of an air duct (120) for dust extraction.