Lawnmower Handle Bar Steering and Speed Control

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Solution Overview

Problem

Existing drive wheel steering systems for lawnmowers are cumbersome and tiring to operate, particularly for walk-behind mowers, due to the need for complex lever controls and lack of stabilization, leading to fatigue and reduced maneuverability.

Innovation Solution

A handle bar assembly pivotally mounted to a control panel that connects to a linkage mechanism controlling the drive wheels' speed and direction, allowing rotation about horizontal and vertical axes to manage speed and steering, with a cam system for setting forward speed and a damper for stabilization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If conventional lever controls are used for drive wheel steering, then steering function is achieved, but operator fatigue increases and maneuverability decreases

Engineering Contradiction:

Improveease of steering controlVSAvoidcomplexity of control system

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical lever controls with a simplified handle bar assembly that rotates about vertical and horizontal axes. The linkage mechanism translates simple rotational movements into differential drive wheel control, eliminating the need for complex lever systems while reducing operator fatigue and improving maneuverability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The handle bar assembly serves multiple functions: it controls both steering direction (via vertical axis rotation) and speed (via horizontal axis rotation), whereas conventional systems required separate controls for each function. This multi-functionality simplifies the overall control system while maintaining full steering capability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Ease of operation

If pistol grip controls are used for speed control, then speed regulation is achieved, but operator fatigue increases and maneuverability decreases

Engineering Contradiction:

Improveease of speed controlVSAvoidtime to become adept with controls

Core Design Contradiction:

Ease of operationVSLoss of time

Solution Approach 1:

The patent replaces pistol grip controls with a handle bar that rotates about a horizontal axis to control speed. This substitution eliminates the repeated compression and release actions required by pistol grips, reducing hand fatigue and allowing operators to become proficient much faster while maintaining precise speed regulation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Stability of the object's composition

If stabilizing bars are added to walk-behind mowers, then operator stability improves, but freedom of hand movement is restricted

Engineering Contradiction:

Improveoperator stabilityVSAvoidfreedom of hand movement

Core Design Contradiction:

Stability of the object's compositionVSEase of operation

Solution Approach 1:

The patent introduces a damper assembly as an intermediary element that provides stabilization without restricting operator movement. The damper absorbs vibrations and shocks between the mower deck and handle bar, enhancing operator comfort and stability while leaving the handle bar fully mobile for unrestricted control operations.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Ease of operation

If linkage mechanism is extended downward to control pumps, then pump control is achieved, but operator movement space is restricted

Engineering Contradiction:

Improvepump control capabilityVSAvoidoperator movement space

Core Design Contradiction:

Ease of operationVSArea of stationary object

Solution Approach 1:

The patent resolves the spatial conflict by routing the linkage mechanism through a vertical dimension - the linkage passes upward through the control panel frame rather than extending downward. This allows the operator to move freely behind the mower while the linkage still effectively connects the handle bar to the pump control points.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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

The system simplifies operation by reducing operator fatigue and improving maneuverability, providing easier control over speed and direction with reduced physical strain and increased comfort, while maintaining stability and allowing for zero-radius turns.

Implementation Method 1

a damper assembly (44) mounted to the handle bar shaft (40) to dampen vibrations and shocks

Methodology Applied

Scientific EffectDamping: Damping

Implementation Method 2

A control assembly (100) may be operatively associated with the linkage mechanism (60) to set a desired forward speed of the lawnmower

Methodology Applied

Scientific EffectCam mechanism: Cam

Implementation Method 3

Hydraulically powered drive wheel systems typically include a separate variable displacement hydraulic pump for each of the two drive wheels

Methodology Applied

Scientific EffectHydraulic power transmission: Hydraulic Press

Data Source

PatentUS7740091B2Drive wheel steering system for lawnmower

Publication Date: 2010.06.22 EXCEL IND INC

AI summary

A drive wheel steering system for a lawnmower has a handle bar assembly that is pivotal about a vertical axis to provide directional control of the mower and rotatable about a horizontal axis to provide speed control of the mower. A control bar is operable to set a desired forward speed of the mower via engagement of a cam and the linkage assembly providing directional and speed control for the mower.