Spring-Driven Bail Stop for Lawn Mower Safety

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Solution Overview

Problem

Existing lawn mowers lack sufficient safety features to prevent accidental startup, particularly for inexperienced users and in situations where the operator may lose control or children are nearby.

Innovation Solution

A lawn mower design featuring a pivotably connected operator bail with a spring-driven bail stop that locks into position when not in use, preventing unintentional startup, and an activation mechanism that requires deliberate action to engage the power source.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the operator bail is made easily movable for intuitive operation, then ease of operation is improved, but safety deteriorates due to risk of accidental startup

Engineering Contradiction:
Improveease of operationVSAvoidaccidental startup risk
Core Design Contradiction:
Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The bail stop mechanism applies preliminary anti-action by automatically engaging a locked position that prevents the operator bail from moving toward the handle assembly, thereby counteracting any accidental forces that might cause unintended startup before the operator deliberately intends to activate the mower

Inventive Principle:
Principle #9Preliminary anti-action

2Object-affected harmful factors

If a bail stop mechanism is added to prevent accidental startup, then safety is improved, but device complexity increases

Engineering Contradiction:
Improveaccidental startup preventionVSAvoidmechanism complexity
Core Design Contradiction:
Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The bail stop mechanism is designed to be self-actuating through spring-loaded engagement and automatic disengagement when the operator bail is deliberately moved, eliminating the need for additional controls, switches, or complex interlocking systems that would further increase device complexity

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The bail stop acts as an intermediary mechanical element between the operator bail and the engine activation system, providing a simple physical barrier that requires deliberate operator action to overcome, thereby preventing accidental startup without complicating the core engine control system

Inventive Principle:
Principle #24Intermediary (Mediator)

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

Enhances safety by ensuring the lawn mower cannot be accidentally started, providing protection against unintended operation and reducing the risk of injury or damage.

Implementation Method 1

the bail stop is moved back to its locked position automatically by a spring-driven mechanism

Methodology Applied
Scientific EffectSpring mechanism: Spring

Data Source

PatentEP3799712B1Lawn mower
Publication Date: 2023.07.12 HUSQVARNA AB
  • EP3799712B1 patent drawingFigure 1
  • EP3799712B1 patent drawingFigure 2~3
  • EP3799712B1 patent drawingFigure 4

AI summary

A lawn mower comprising: a handle assembly (60) for guiding operation of the lawn mower (10); an operator bail (70) which is pivotably connected to the handle assembly (60); and a bail stop (72) which when arranged in a locked position prevents the operator bail (70) to be moved towards the handle assembly (60), wherein when the bail stop (72) is arranged in an un-locked position, the operator bail (70) is allowed to be moved towards the handle assembly (60), wherein rotation of at least a blade of the lawn mower (10) is started once the operator bail (70) is moved in proximity to the handle assembly (60), wherein the bail stop (72) is moved back to its locked position automatically by a spring-driven mechanism.