Gear-Driven Cutting Device for Thick Branch Access

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Solution Overview

Problem

Conventional garden cutting devices, such as scissors and pruning shears, face limitations in cutting thick branches due to a fixed and limited opening angle of the lever elements, which restricts access and cutting efficiency, especially in cramped spaces.

Innovation Solution

A cutting device with a gear or connector that translates the movement of lever elements into a larger movement of cutting elements, allowing a second angle that is one and a half to three times larger than the first angle, enabling a quick translation ratio (i <1), and incorporating a motor drive unit and sensor systems for enhanced operation and safety.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the opening angle of lever elements is increased to cut thick branches, then the cutting capability is improved, but the device becomes difficult to operate in confined spaces where lever opening is limited by adjacent branches

Engineering Contradiction:
Improvecutting capabilityVSAvoidaccessibility in confined spaces
Core Design Contradiction:
StrengthVSEase of operation

Solution Approach 1:

The device segments the motion transmission into two independent stages: lever element motion and cutting element motion, connected through a gear mechanism. This allows the lever opening angle and cutting element opening angle to be independently optimized, resolving the conflict between cutting capability and accessibility.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

A gear mechanism acts as an intermediary between the lever elements and cutting elements, translating the limited lever motion into amplified cutting element motion. The gear transfers and transforms the mechanical motion, enabling the cutting elements to achieve a larger opening angle than the lever elements.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Ease of operation

If the lever elements are designed with a limited opening angle for ergonomic operation, then the ease of operation is improved, but the cutting elements cannot open wide enough to cut thick branches

Engineering Contradiction:
Improveergonomic operationVSAvoidcutting capability
Core Design Contradiction:
Ease of operationVSStrength

Solution Approach 1:

The gear mechanism serves as a motion amplifier intermediary, taking the ergonomic lever opening angle and transforming it into a larger cutting element opening angle. This allows the lever elements to remain compact for easy handling while the cutting elements achieve the necessary width for thick branches.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The device changes the motion parameter relationship between input (lever) and output (cutting elements) through the gear ratio. By selecting appropriate gear tooth counts, the system transforms the lever opening angle parameter into a larger cutting element opening angle parameter, enabling thick branch cutting with ergonomic lever dimensions.

Inventive Principle:
Principle #35Parameter changes

3Strength

If a gear mechanism with ratio i < 1 is used to amplify the opening angle of cutting elements, then the cutting capability is improved, but the device complexity increases

Engineering Contradiction:
Improvecutting capabilityVSAvoidmechanism complexity
Core Design Contradiction:
StrengthVSDevice complexity

Solution Approach 1:

The gear mechanism performs multiple functions simultaneously: it amplifies the opening angle, transmits force from the lever elements to the cutting elements, and enables the angular transformation. This multi-functionality reduces the need for additional separate mechanisms, thereby limiting the increase in overall device complexity.

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

4Strength

If the opening angle of cutting elements is increased to cut thick branches, then the cutting capability is improved, but the closing speed of cutting elements decreases

Engineering Contradiction:
Improvecutting capabilityVSAvoidclosing speed
Core Design Contradiction:
StrengthVSSpeed

Solution Approach 1:

The gear mechanism enables dynamic motion characteristics where the cutting elements can achieve both large opening angles and rapid closing speeds. The mechanical advantage provided by the gear allows the cutting elements to accelerate quickly during closing while maintaining the ability to open to a wider angle than the lever elements.

Inventive Principle:
Principle #15Dynamics

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 allows for larger opening angles of the cutting elements, increased cutting speed, and improved accessibility for thick branches, reducing operator effort and preventing overloading, while maintaining ergonomic operation and reducing the complexity of parts.

Implementation Method 1

A gear and/or a connector is proposed that translates a movement of the lever elements relative to a movement of the cutting elements with a ratio i

Methodology Applied
Scientific EffectMechanical Advantage: Mechanical Advantage

Implementation Method 2

It is proposed that the connector be a gearwheel, wherein the gearwheel is rotatably mounted on the second lever element and is supported, in particular, in a force-transmitting manner, on the one hand, against a toothed section of the first lever element and, on the other hand, against a toothed section of the second cutting element

Methodology Applied
Scientific EffectGear: Gear

Data Source

PatentEP3673725B1Cutting device
Publication Date: 2025.02.12 ROBERT BOSCH GMBH
  • EP3673725B1 patent drawingFigure 1
  • EP3673725B1 patent drawingFigure 2
  • EP3673725B1 patent drawingFigure 3~4

AI summary

The invention relates to a cutting device (10), in particular a garden cutting device, with at least one first and one second cutting element (12, 14) movable relative to each other, with a first and one second lever element (502, 504), in particular a handle element (16, 18), movable relative to each other, for opening and closing the cutting elements (12, 14). It is proposed that a displacement of the lever elements (502, 504) by a first angle (506) causes a displacement of the cutting elements (12, 14) by a second angle (508), wherein the second angle (508) is larger than the first angle (506), in particular one and a half to three times as large, preferably twice as large.