Inductive Trigger Assembly for Precise Power Tool Motor Control

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Solution Overview

Problem

Power tools lack efficient and reliable trigger assemblies that can accurately control electric motors for precise direction and speed control without the need for multiple triggers or complex direction switches, leading to increased component costs and potential wear from contact-based switches.

Innovation Solution

A trigger assembly featuring a printed circuit board with inductive sensors that detect the movement of conductors relative to the trigger, allowing the motor control unit to activate or deactivate the electric motor based on the direction and speed of trigger movement, eliminating the need for secondary direction switches and reducing component count.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If contact-based switches are used for trigger control, then the power tool can be activated and deactivated, but the switches experience wear and require multiple triggers or direction switches for precise control

Engineering Contradiction:

Improveswitch longevityVSAvoidnumber of triggers and direction switches

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces contact-based mechanical switches with inductive sensors that detect the position and movement of a conductor coupled to the trigger. This non-contact sensing mechanism eliminates wear from physical contact while providing precise detection of trigger position, direction, and speed without requiring multiple separate switches or triggers.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The inductive sensor system performs multiple functions simultaneously: it detects trigger activation, determines direction of movement, measures speed of movement, and provides position information. This multi-functionality eliminates the need for separate direction switches and multiple triggers, reducing overall device complexity while maintaining reliability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Ease of operation

If multiple triggers or direction switches are added for precise motor control, then direction and speed control improve, but component count and cost increase

Engineering Contradiction:

Improvemotor direction and speed control precisionVSAvoidcomponent count

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent replaces multiple mechanical switches and direction controls with a single inductive sensor system that electronically determines direction and speed based on the movement characteristics of the conductor. This substitution reduces component count while maintaining or improving control precision through electronic processing of sensor signals.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The conductor coupled to the trigger serves as an intermediary element that translates mechanical trigger movement into electrical signals detectable by the inductive sensor. This intermediary enables precise detection of movement direction and speed without requiring direct mechanical contact or multiple separate switches.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If inductive sensors are used for non-contact switching, then component longevity increases and wear is reduced, but the system requires precise detection of conductor movement

Engineering Contradiction:

Improvenon-contact switching durabilityVSAvoidconductor movement detection accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent implements non-contact inductive sensing to detect conductor movement, eliminating wear from mechanical contact. The inductive sensor measures changes in magnetic field caused by conductor position and movement, providing durable operation while achieving sufficient measurement precision for trigger control applications through electronic signal processing.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 precise control of electric motors in power tools with reduced component complexity, increased longevity due to non-contact switching, and cost savings by integrating direction control within the trigger assembly.

Implementation Method 1

The printed circuit board has an inductive sensor thereon responsive to relative movement between the conductor and the inductive sensor caused by movement of the trigger

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS20240396549A1Trigger assembly

Publication Date: 2024.11.28 MILWAUKEE ELECTRIC TOOL CORP

AI summary

A trigger assembly, for use with a power tool having an electric motor, includes a trigger, a spring configured to bias the trigger towards a first position, a conductor coupled for movement with the trigger, and a printed circuit board. The printed circuit board has an inductive sensor thereon responsive to relative movement between the conductor and the inductive sensor caused by movement of the trigger. An output of the inductive sensor is used to activate the electric motor.