Cutting Tool Lever Mechanism for Symmetrical Force Distribution

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Solution Overview

Problem

Prior cutting tools experience suboptimal force transmission due to lever and engagement point design, leading to uneven cutting force distribution and asymmetrical cutting movements, making the process cumbersome and requiring more force at the beginning of each cut.

Innovation Solution

The cutting tool features elongated elements connected via tooth gear parts to an anvil and a moving blade, with a lever mechanism that optimizes the lever arm for symmetrical force distribution and stepwise cutting, using engagement points arranged transversely to the pivot point for efficient force transmission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If engagement points are placed successively away from the pivot point on a radial line, then the lever mechanism can accommodate stepwise cutting of objects with different diameters, but the cutting force is not transmitted optimally and force is lost

Engineering Contradiction:
Improveability to cut objects with different diametersVSAvoidcutting force transmission efficiency
Core Design Contradiction:
Adaptability or versatilityVSForce

Solution Approach 1:

The engagement points are arranged in a transverse direction perpendicular to the radial line from the pivot point, rather than sequentially along the radial line. This dimensional change allows the lever to maintain a consistent lever arm length (perpendicular distance from pivot to engagement point) while still accommodating different cutting depths, thereby optimizing force transmission efficiency across all engagement points.

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

2Device complexity

If one blade is provided fixedly in one of the handles, then the structure is simplified, but the cutting movement becomes asymmetrical for both hands

Engineering Contradiction:
Improveblade mounting structureVSAvoidcutting movement symmetry
Core Design Contradiction:
Device complexityVSEase of operation

Solution Approach 1:

The anvil is designed as a separate component with asymmetrical features including a hand rest on one side and engagement points arranged to work with the lever mechanism. This intentional asymmetry allows the tool to be optimized for one-handed operation while maintaining balanced force distribution and symmetrical cutting action, resolving the contradiction between structural simplicity and operational symmetry.

Inventive Principle:
Principle #4Asymmetry

3Productivity

If more force is required at the beginning of each cutting movement, then the cutting can be initiated, but the cutting becomes cumbersome and more force must be exerted on the handles

Engineering Contradiction:
Improvecutting initiation capabilityVSAvoidforce requirement during cutting
Core Design Contradiction:
ProductivityVSEase of operation

Solution Approach 1:

The spring mechanism is pre-loaded to automatically apply initial force to the lever, which in turn applies force to the blade at the engagement point. This preliminary action eliminates the need for the user to exert excessive force to initiate cutting, and the spring maintains consistent force throughout the cutting stroke, making the operation easier and less cumbersome.

Inventive Principle:
Principle #10Preliminary action

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 ensures consistent and reduced force requirement throughout cutting movements, maintaining symmetry and efficiency in cutting, especially in the final cutting step where the most force is needed.

Implementation Method 1

The first and the second elongated elements and hence the handles are connected in an articulated manner to the anvil part or the first blade as well as to one another with tooth gear parts

Methodology Applied
Scientific EffectGear mechanism: Gear

Implementation Method 2

The first or the second of the handles is further connected operationally to a movable blade with a lever mechanism for force transmission. The first end of the lever in the lever mechanism is thus connected to the first or the second elongated element in an articulated manner at a pivot point.

Methodology Applied
Scientific EffectLever principle: Lever

Data Source

PatentEP2156731B1Cutting tool
Publication Date: 2014.03.19 FISKARS GARDEN OY AB
  • EP2156731B1 patent drawingFigure 1
  • EP2156731B1 patent drawingFigure 2
  • EP2156731B1 patent drawingFigure 3

AI summary

The invention relates to a cutting tool comprising a metal plate (20) including a blade (22) that forms a cutting jaw with an anvil (4), the metal plate (20) being connected in an articulated manner to an anvil part (2) at a first pivot point (6) and connected operationally to a first elongated element (12) for opening and closing the cutting jaw in response to the relative turning movement of the first elongated element (12) and the second elongated element (14) about the second and the third pivot points (8, 10) respectively.