Three-Wing Locking Lever for Ergonomic Hand Tool Grip

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Solution Overview

Problem

Hand-held work devices with safety levers are often uncomfortable and non-intuitive to operate, requiring operators to release their grip to actuate both levers simultaneously, which can be challenging, especially when using tools that require different grip positions.

Innovation Solution

The design incorporates a locking lever with three wing elements, allowing ergonomic operation even when the tool is held to the side, with a spring unit that biases the lever back to its locking position, enabling operation with a pure pivoting movement of the thumb and facilitating use with either hand, and allowing unlocking in both directions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If both levers are pressed simultaneously, then the safety function is activated, but the operator must abandon their firm grip on the handle

Engineering Contradiction:
Improvesafety functionVSAvoidgrip stability
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The locking lever is segmented into three separate wing elements arranged at different positions around the rotation axis. This segmentation allows the operator to press the locking lever with the thumb while maintaining grip on the handle with other fingers, as each wing element can be actuated independently without requiring release of the entire grip

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The locking lever is designed with wing elements distributed in three-dimensional space around the rotation axis rather than in a single plane. This spatial distribution allows the thumb to access the locking lever from different angles while maintaining a firm grip on the handle, resolving the conflict between safety activation and grip stability

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

2Adaptability or versatility

If the tool is held at an angle for ergonomic cutting positions, then cutting versatility is improved, but operating the locking lever becomes difficult

Engineering Contradiction:
Improvegrip position flexibilityVSAvoidlocking lever operation
Core Design Contradiction:
Adaptability or versatilityVSEase of operation

Solution Approach 1:

The locking lever's wing elements are arranged in three-dimensional space around the rotation axis at different angular positions and heights. This allows the operator to access and press the locking lever from multiple directions and angles, maintaining ease of operation even when the tool is held at various angles for different cutting positions

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

Solution Approach 2:

The locking lever design with multiple wing elements makes it universally operable from various grip positions and angles. The same locking lever structure serves multiple functions by being accessible from different directions, accommodating both horizontal and vertical cutting operations without requiring different mechanisms

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

This design enhances ergonomic operation by allowing the operator to actuate the locking lever without releasing their grip, improving comfort and usability across various grip positions and techniques.

Implementation Method 1

a spring unit (6) which biases the locking lever (5) in the direction of the locked position (10)

Methodology Applied
Scientific EffectElastic force: Elasticity

Data Source

PatentEP3792009B1Hand-guided appliance with a tool
Publication Date: 2024.04.24 ANDREAS STIHL AG & CO KG
  • EP3792009B1 patent drawingFigure 1~2
  • EP3792009B1 patent drawingFigure 3~4
  • EP3792009B1 patent drawingFigure 5~6

AI summary

The invention relates to a hand-held tool with a tool (3). The tool comprises a handle (26), the handle (26) having a longitudinal axis (18). The locking lever (5) is pivotally mounted about a pivot axis (8). The locking lever (5) locks the actuating lever (4) in a locked position (10) and releases the actuating lever for actuation in at least one operating position (11, 11'). The locking lever (5) has three wing elements (24, 24', 34) for actuating the locking lever (5).