Capacitive Control Handles and Clutch Deceleration for Stump Cutters

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Solution Overview

Problem

Material reduction machines, such as stump cutters, face challenges in reliably detecting operator presence at control levers due to intermittent lever use and operator positioning, leading to frequent unwanted cutter wheel stoppages and operator fatigue, while existing braking systems are inefficient and unreliable for decelerating heavy tools.

Innovation Solution

A control system utilizing capacitive sensing technology in the control handles to detect operator absence and engage a clutch with the engine during speed reduction, maintaining engagement to decelerate the material reduction tool, and disengaging before engine rpm drops below a predetermined level, combined with an electrical PTO clutch/brake for efficient braking.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If mechanical or electromechanical interlocks are used on control levers to detect operator presence, then operator presence detection is improved, but operator freedom of hand position is restricted causing fatigue and control errors

Engineering Contradiction:

Improveoperator presence detectionVSAvoidoperator freedom of hand position

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent replaces mechanical interlocks and electromechanical switches with capacitive sensing technology. The capacitive sensors detect changes in electrical capacitance caused by the operator's proximity or contact with control levers, eliminating the need for mechanical buttons or switches that restrict hand positioning. This substitution maintains reliable operator presence detection while preserving natural operator movement and comfort.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Object-affected harmful factors

If the operator station is positioned to minimize risk from thrown objects, then operator safety is improved, but operator positioning becomes more difficult and fatigue increases

Engineering Contradiction:

Improveoperator safety from thrown objectsVSAvoidoperator positioning flexibility

Core Design Contradiction:

Object-affected harmful factorsVSEase of operation

Solution Approach 1:

The patent introduces capacitive sensing technology as an intermediary between the operator and the control system. This allows the operator to remain in safe positions away from the cutter wheel while still enabling reliable detection of operator presence through the control handles. The capacitive sensors act as a mediator that can detect operator proximity without requiring the operator to be in a vulnerable position.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Speed

If existing braking systems are used to decelerate the material reduction tool, then braking function is provided, but braking efficiency and reliability are insufficient for heavy tools

Engineering Contradiction:

Improvetool deceleration capabilityVSAvoidbraking system reliability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent converts the engine's rotational inertia and kinetic energy, which normally would be wasted during deceleration, into a useful braking force. By engaging the clutch to connect the engine to the drive system during engine shutdown, the engine's resistance to rotation provides effective braking torque. This transforms what would be harmful wasted energy into a beneficial braking mechanism that is both efficient and reliable for heavy tools.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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

Enables reliable operator presence detection without inhibiting control, reduces operator fatigue, and provides effective and efficient braking, ensuring smooth operation and reducing unwanted stoppages.

Implementation Method 1

A capacitive sensor system is utilized in the control handles to sense when an operator is not present at the control station

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

The control unit is configured to decelerate the material reduction tool by maintaining the clutch engaged with the engine during an engine speed reduction period

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 3

the material reduction tools on such machines are often heavy and difficult to decelerate due to inertia of the moving tool

Methodology Applied

Scientific EffectInertia: Inertia

Data Source

PatentUS8257227B2Method and apparatus for decelerating a material reduction tool

Publication Date: 2012.09.04 VERMEER MFG CO

AI summary

One embodiment of the present disclosure provides a material reduction machine including a clutch configured and arranged to engage and disengage a material reduction tool with an engine based in response to a control unit. The control unit is configured to decelerate the material reduction tool by maintaining the clutch engaged with the engine during an engine speed reduction period. Another embodiment of the present disclosure also provides a method of decelerating a material reduction tool of a material reduction machine. The method includes the steps of maintaining engagement between the material reduction tool and an engine after the engine enters an engine speed reduction mode, and disengaging the material reduction device from the engine before the engine rpm drops below a predetermined level.