Handheld Tool Gear Closure with Pressure Valve

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Solution Overview

Problem

The internal pressure of hand tool gear housings increases to undesirable levels due to a closed design without an air duct, leading to reduced service life and performance issues, particularly affecting impact energy in hand-held power tools.

Innovation Solution

A hand tool gear lock with an air duct and a pressure valve designed as an elastic hose element, which reduces overpressure and compensates for negative pressure, allowing air to escape while preventing lubricant leakage through an air-permeable and gear oil-tight sealing element.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the gear housing is designed with a closed structure without an air duct, then the sealing performance and lubricant retention are improved, but the internal pressure increases to undesirable levels during operation

Engineering Contradiction:
Improvesealing performanceVSAvoidinternal pressure
Core Design Contradiction:
ReliabilityVSStress or pressure

Solution Approach 1:

The patent employs a diaphragm (flexible membrane) as the sealing element in the gear closure. This diaphragm is permeable to gas molecules but impermeable to lubricant, allowing pressure equalization while maintaining lubricant retention. The flexible nature of the diaphragm enables it to deform with pressure changes, facilitating air passage while blocking liquid lubricant.

Inventive Principle:
Principle #30Flexible shells and thin films

Solution Approach 2:

The diaphragm is designed as a porous or microporous membrane that selectively permits gas molecules to pass through while blocking larger lubricant molecules. This porous structure enables the dual function of pressure regulation and lubricant sealing simultaneously, resolving the contradiction between closed sealing and pressure release.

Inventive Principle:
Principle #31Porous materials

2Loss of substance

If the gear housing is designed with a closed structure without an air duct, then the lubricant retention is improved, but the service life and work performance data deteriorate

Engineering Contradiction:
Improvelubricant retentionVSAvoidservice life
Core Design Contradiction:
Loss of substanceVSDuration of action of stationary object

Solution Approach 1:

The diaphragm acts as a selective barrier that retains lubricant while allowing air to pass through. This maintains the closed lubricant system necessary for long service life, while simultaneously enabling pressure equalization that prevents performance degradation and extends component life.

Inventive Principle:
Principle #30Flexible shells and thin films

Solution Approach 2:

The porous diaphragm structure provides selective permeability based on molecular size, allowing small gas molecules to diffuse through while blocking larger lubricant molecules. This ensures long-term lubricant retention while preventing pressure-related performance loss.

Inventive Principle:
Principle #31Porous materials

3Stress or pressure

If a pressure valve is added to the gear closure to release overpressure, then the internal pressure is reduced, but the device complexity increases

Engineering Contradiction:
Improveoverpressure reductionVSAvoidclosure structure complexity
Core Design Contradiction:
Stress or pressureVSDevice complexity

Solution Approach 1:

The diaphragm performs multiple functions simultaneously: it seals the gear housing, retains lubricant, allows pressure equalization, and prevents contaminant ingress. By combining these functions into a single component, the patent avoids the complexity of separate pressure valves, seals, and filters while achieving overpressure protection.

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

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

Regulates internal pressure, preventing damage and maintaining performance by allowing air to escape while keeping lubricant inside, thus extending the service life and maintaining the tool's impact energy.

Implementation Method 1

a reduction in an overpressure occurring in the transmission housing is accompanied by an elastic deformation of the elastic hose element

Methodology Applied
Scientific EffectElastic deformation: Elasticity

Implementation Method 2

an air-permeable and in particular essentially gear oil-tight sealing element

Methodology Applied
Scientific EffectSelective permeability: Permeation

Data Source

PatentEP3221091B1Handheld tool gear closure and handheld machine tool
Publication Date: 2022.07.13 HILTI AG
  • EP3221091B1 patent drawingFigure 1a~1c
  • EP3221091B1 patent drawingFigure 2
  • EP3221091B1 patent drawingFigure 3

AI summary

The invention relates to a hand-held tool transmission closure having a base body for closing a transmission housing opening of a transmission housing of a hand-held machine tool, in particular a drill hammer or a combi-hammer, wherein the hand-held machine tool transmission closure comprises an air channel, through which air can flow into and out of the transmission housing, and wherein the hand-held machine tool transmission closure comprises a pressure valve arranged in the air channel, via which an excess pressure occurring in the transmission housing can be reduced.