Ergonomic Handle Drive Control and Undercut Coupling for Garden Tools

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Solution Overview

Problem

Existing gardening devices face issues with stress concentration and breakage at coupling zones, limited assembly speed, user fatigue, and corrosion due to threaded couplings, as well as difficulty in managing drive controls during operation.

Innovation Solution

A device with an undercut coupling system between the knob and central body, eliminating the need for threaded fixing elements, and a ergonomic design that includes a handle with a drive control system allowing easy activation of the motor, reducing user fatigue and improving handling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If threaded couplings (screws and bolts) are used to constrain the knob to the body, then the assembly is secure, but the assembly speed during manufacturing is limited and stress concentration increases breakage risk

Engineering Contradiction:

Improveknob coupling reliabilityVSAvoidassembly speed

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The central body is divided into two separate caps (first cap and second cap) that are constrained to each other to form the complete central body. This segmentation allows the knob to be assembled with the central body in a single operation without threaded fasteners, improving assembly speed while maintaining structural integrity through the distributed cap structure

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent replaces the threaded mechanical coupling system (screws and bolts) with an undercut coupling system formed by the counter-shaped constraining portions of the caps and knob. This substitution eliminates the need for threaded fasteners, enabling faster assembly while distributing stresses more evenly across the coupling interface

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If threaded couplings (screws and bolts) are used to constrain the knob to the body, then the assembly is secure, but stress concentration intensifies leading to increased breakage risk

Engineering Contradiction:

Improveknob coupling durabilityVSAvoidcoupling zone strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The central body is segmented into two caps that together form the constraining portion. This segmentation distributes the coupling interface across multiple contact surfaces between the caps and the knob, preventing stress concentration at single points and reducing breakage risk while maintaining secure attachment

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent replaces the stress-concentrating threaded coupling system with an undercut coupling system where the counter-shaped constraining portions create a distributed stress field. This mechanical substitution eliminates thread roots and stress concentration points, improving the strength and durability of the coupling zone

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If threaded couplings (screws and bolts) are used to constrain the knob to the body, then the assembly is secure, but manufacturing costs increase due to additional components

Engineering Contradiction:

Improveknob coupling securityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent extracts and eliminates the threaded fasteners (screws and bolts) from the coupling system. The knobs are secured to the central body through the undercut coupling formed by the counter-shaped constraining portions of the caps, removing the need for separate fastening components and reducing manufacturing costs while maintaining secure attachment

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent merges the function of mechanical fastening into the structural design of the caps and knob themselves. The counter-shaped constraining portions are integrated into the cap geometry, combining the structural support function with the fastening function, thereby eliminating the need for separate fasteners and reducing overall manufacturing cost

Inventive Principle:

Principle #5Merging (Combining)

4Ease of operation

If the device mass is reduced, then operator fatigue decreases, but structural integrity may be compromised

Engineering Contradiction:

Improveoperator fatigue reductionVSAvoiddevice structural integrity

Core Design Contradiction:

Ease of operationVSStrength

Solution Approach 1:

The patent employs composite material construction for the caps and knob components, utilizing materials with high strength-to-weight ratios. This allows the device mass to be reduced for easier operator handling while maintaining the structural integrity required for reliable operation and durability

Inventive Principle:

Principle #40Composite materials

Data Source

PatentEP4477060A1Device for executing maintenance operations in a land or garden

Publication Date: 2024.12.18 STIGA S P A IN BREVE ANCHE ST SPA

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AI summary

A device adapted to execute land maintenance operations comprising a work tool, a motor configured for moving said work tool, a handle comprising a gripping portion configured to be grasped by an operator, at least one drive control configured for activating the motor, wherein said drive control comprises a fulcrum defining a drive axis and a drive tab 52 movable about said drive axis and configured to be driven by an operator. The drive tab extends in length away from the drive axis, and in width between a first side edge and a second side edge, and wherein said drive tab comprises a contact surface, configured to contact a hand of the operator, extending in width to define a respective curved profile having concavity facing said gripping portion of the handle.