Variable Prestress Blade Arrangement for Garden Shears

Solution Overview

Problem

Motor-driven garden cutting devices with oscillating blade arrangements face issues with wear and damage when cutting thin branches, as the upper blade is pinched between the cutters, leading to impaired cutting performance and surface damage, and increased wear due to higher prestressing for thicker materials.

Innovation Solution

The blade arrangement features a variable resistance force mechanism, allowing for low wear during grass cutting and improved cutting performance for bushes by adjusting the elastic pretension and support geometry, preventing the upper blade from lifting off the lower blade, especially during problematic cutting processes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the upper blade is prestressed with higher force to prevent lifting during cutting, then cutting performance for thick branches is improved, but wear of the blade arrangement increases rapidly

Engineering Contradiction:

Improvecutting performanceVSAvoidblade service life

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The blade arrangement transitions from a static prestress system to a dynamic variable prestress system. The upper blade can change its prestress force automatically during operation based on the cutting resistance encountered, allowing high prestress for thick branches only when needed while maintaining low prestress for soft materials like grass during normal operation.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The prestress force parameter of the upper blade is made variable rather than fixed. The system automatically adjusts the prestress force level according to the material being cut, transitioning between low prestress (for grass) and high prestress (for thick branches) states, thereby optimizing both cutting performance and blade durability.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If the upper blade is prestressed with higher force to prevent lifting, then cutting of thick branches is improved, but wear increases and service life decreases

Engineering Contradiction:

Improvecutting capabilityVSAvoidblade service life

Core Design Contradiction:

Adaptability or versatilityVSDuration of action of moving object

Solution Approach 1:

The blade arrangement transitions from a static prestress system to a dynamic variable prestress system. The upper blade can change its prestress force automatically during operation based on the cutting resistance encountered, allowing high prestress for thick branches only when needed while maintaining low prestress for soft materials like grass during normal operation.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The prestress force parameter of the upper blade is made variable rather than fixed. The system automatically adjusts the prestress force level according to the material being cut, transitioning between low prestress (for grass) and high prestress (for thick branches) states, thereby optimizing both cutting performance and blade durability.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the upper blade is allowed to lift slightly from the lower blade, then wear is reduced for grass cutting, but thin branches may be pinched and damage the plant surface

Engineering Contradiction:

Improveblade service lifeVSAvoidbranch damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The blade arrangement transitions from a static prestress system to a dynamic variable prestress system. The upper blade can change its prestress force automatically during operation based on the cutting resistance encountered, allowing high prestress for thick branches only when needed while maintaining low prestress for soft materials like grass during normal operation.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The prestress force parameter of the upper blade is made variable rather than fixed. The system automatically adjusts the prestress force level according to the material being cut, transitioning between low prestress (for grass) and high prestress (for thick branches) states, thereby optimizing both cutting performance and blade durability.

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

This solution enables efficient cutting of both thin and thick materials with reduced wear and extended blade life, minimizing damage to branches and maintaining effective cutting performance across different materials.

Implementation Method 1

the second blade (42) can be elastically deformed in relation to the first blade (41)

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Implementation Method 2

the support device (44) is designed to increase a resistance force against further deformation of the second blade (42)

Methodology Applied

Scientific EffectMechanical advantage: Mechanical Advantage

Data Source

PatentEP2627164B1Blade arrangement for a garden cutting device and garden cutting device having such a blade arrangement

Publication Date: 2015.03.18 HUSQVARNA AB

Figure 1~3
Figure 4(A)~6(B)
Figure 7~8(B)

AI summary

The invention relates to a blade arrangement (OM, UM) for a motor-operated cutting arrangement, in particular in the style of motor-operated grass shears, wherein said blade arrangement can be used for the low-wear cutting of grass or other weak material to be cut and at the same time has an improved cutting performance with respect to known grass shears for stronger material to be cut, such as bushes.