Contactless Power Tool Trigger Using Rotational Magnetic Sensing

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Solution Overview

Problem

Physical connections on input devices, such as triggers for power tools, wear over time, reducing the operational life of the tools and leading to inefficiencies.

Innovation Solution

A contactless trigger assembly using a movable plunger, arm, and magnet system that senses magnetic field changes to control the power tool's output, eliminating the need for physical contact and reducing wear.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If physical connections are used in input devices, then the device structure is simple and reliable, but the connections wear over time reducing operational life

Engineering Contradiction:

Improveoperational lifeVSAvoidwear resistance

Core Design Contradiction:

ReliabilityVSDuration of action of moving object

Solution Approach 1:

The patent replaces the mechanical contact system (physical connections between trigger components and electronic components) with a magnetic sensing system. A magnet is attached to the movable plunger and a magnetic sensor detects its position, eliminating physical contact and wear between the trigger mechanism and electronic components while maintaining the ability to detect trigger position and control tool operation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Duration of action of stationary object

If contactless sensing is used, then wear is reduced and operational life is extended, but the device complexity increases

Engineering Contradiction:

Improvetool durabilityVSAvoidtrigger assembly complexity

Core Design Contradiction:

Duration of action of stationary objectVSDevice complexity

Solution Approach 1:

The patent introduces a magnet as an intermediary element that couples the mechanical trigger movement to the electronic sensing system without direct contact. The magnet translates the physical movement of the plunger into a detectable magnetic field change, serving as a bridge between the mechanical and electronic domains while avoiding wear-prone direct connections.

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 contactless trigger assembly extends the operational life of power tools by minimizing wear and providing precise control over the tool's output, enabling longer tool durability and improved performance.

Implementation Method 1

an arm including a first side that is moveably connected to the second end of the moveably plunger and a second side that is coupled to a magnet. The trigger assembly also includes a sensor configured to sense a magnetic field of the magnet.

Methodology Applied

Scientific EffectMagnetic field sensing: Magnetic Field

Data Source

PatentUS11890741B2Contactless trigger with rotational magnetic sensor for a power tool

Publication Date: 2024.02.06 MILWAUKEE ELECTRIC TOOL CORP

AI summary

A trigger assembly for a power tool includes a housing, a moveable plunger extending from a surface of the housing, the movable plunger includes a first end disposed externally from the housing and a second end disposed internally within the housing. The trigger assembly further includes a trigger shoe coupled to the first end of the moveable plunger, and an arm including a first side that is moveably connected to the second end of the moveably plunger and a second side that is coupled to a magnet. The trigger assembly also includes a sensor configured to sense a magnetic field of the magnet. Movement of the trigger shoe rotates the magnet, and alters the magnetic field sensed by the sensor.