Garden Trimmer Switch Circuit Prevents Short Circuit Activation

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Solution Overview

Problem

Garden processing machines, such as lawn mowers, face a high risk of operator injury due to short circuits in the connecting cables that can lead to overvoltage and unintended motor activation, as existing technologies lack effective means to distinguish between a closed switch state, open state, and short circuit conditions.

Innovation Solution

A garden processing machine switching device is designed with a switch and electrical resistors forming a voltage divider, connected to a comparison circuit unit with comparators, which distinguishes between switch states and prevents motor activation in case of a short circuit, ensuring operator safety by preventing undesired starting of the electric motor unit.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a simple switch is used to control the motor unit, then the device complexity is reduced and ease of operation is improved, but the reliability deteriorates due to inability to distinguish between closed state, open state, and short circuit conditions

Engineering Contradiction:
Improveswitch operationVSAvoidshort circuit detection
Core Design Contradiction:
Ease of operationVSReliability

Solution Approach 1:

A comparison circuit unit is introduced as an intermediary between the simple switch and the motor control system. This circuit includes comparators that receive voltage signals from the switch through a connecting cable and compare them against reference voltages to determine whether the switch is in closed state, open state, or short circuit condition, thereby enabling reliable detection without complicating the user interface

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The mechanical switch system is supplemented with an electronic detection system. Instead of relying solely on mechanical switch positions, the invention uses electrical voltage comparison through comparators to detect the switch state and short circuit conditions, replacing mechanical detection with electronic measurement

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If a comparison circuit unit is added to distinguish switch states and detect short circuits, then the reliability is improved, but the device complexity increases

Engineering Contradiction:
Improveshort circuit detectionVSAvoidswitching device structure
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The comparison circuit unit integrates multiple functions into a single modular component: it combines voltage signal reception from the connecting cable, voltage comparison using comparators, short circuit detection, and motor control signal generation. This merging of functions reduces the need for separate discrete components and simplifies the overall system architecture

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The comparison circuit unit serves multiple purposes simultaneously: it monitors switch state (closed/open), detects short circuits in the connecting cable, controls motor unit activation, and provides system diagnostics. This multi-functionality reduces the need for separate dedicated components for each function

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Ease of operation

If the switch is arranged separately from the motor housing unit, then the ease of operation is improved and operator safety is enhanced, but the device complexity increases due to additional connecting cable

Engineering Contradiction:
Improveswitch accessibilityVSAvoidconnecting cable
Core Design Contradiction:
Ease of operationVSDevice complexity

Solution Approach 1:

The connecting cable serves as an intermediary element that enables both spatial separation for safety and functional connectivity. The cable is designed with integrated monitoring capability through the comparison circuit unit, which detects short circuits in the cable itself, thereby transforming the cable from a simple connector into an active safety component

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

The solution effectively prevents the electric motor unit from starting due to short circuits, enhancing operating safety and providing a structurally simple, cost-effective, and compact configuration for the switching device.

Implementation Method 1

at least one first electrical resistor, which is arranged together with the switch in a switch housing and which is connected in series with the switch in such a way that it forms a voltage divider with at least one other electrical resistor arranged in the comparison circuit unit

Methodology Applied
Scientific EffectVoltage divider: Electrical Resistance

Data Source

PatentEP2899554B1Garden cultivation machine with switching device preventing unintended activation
Publication Date: 2016.12.14 ROBERT BOSCH GMBH
  • EP2899554B1 patent drawingFigure 1
  • EP2899554B1 patent drawingFigure 2
  • EP2899554B1 patent drawingFigure 3

AI summary

The present invention relates to a garden trimming machine switching device, which is configured for at least partly switching an electric motor unit (12) in the electrical aspect, and is provided with at least one switch (14). The garden trimming machine switching device is proposed to comprise a comparison circuit unit (16) which is configured for at least distinguishing the closed state and short circuit of the switch (14).