Hall Effect Trigger for Power Tools

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Solution Overview

Problem

Existing trigger mechanisms in powered devices, such as power tools, suffer from limited variability of control and reliability due to bulky potentiometers and wear-prone switches, which occupy significant space and reduce the lifespan of the device.

Innovation Solution

A trigger apparatus utilizing a linear Hall effect sensor and an activation switch to measure changes in magnetic fields associated with trigger movement, allowing for precise control and improved reliability by reducing power consumption and wear, while enabling compact design.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a potentiometer is used in the trigger mechanism, then the control variability is limited, but the device occupies a large amount of space

Engineering Contradiction:
Improvecontrol variabilityVSAvoidspace occupied
Core Design Contradiction:
Adaptability or versatilityVSVolume of moving object

Solution Approach 1:

The patent replaces the mechanical potentiometer with a magnetic field-based sensing system. A magnet is attached to the trigger, and a Hall effect sensor detects the magnetic field changes as the trigger moves, eliminating the need for physical contact and reducing space requirements while maintaining control variability.

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

Solution Approach 2:

The patent changes the measurement parameter from physical position (potentiometer) to magnetic field strength (Hall effect sensor). This allows for more precise detection of trigger position with a smaller component footprint, improving both control variability and spatial efficiency.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If a switch is used to control power flow, then the power switching function is achieved, but the switch experiences significant wear reducing reliability

Engineering Contradiction:
Improvetrigger mechanism lifeVSAvoidswitch wear
Core Design Contradiction:
ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent eliminates the mechanical switch by using a Hall effect sensor to detect trigger position and control power electronically. This non-contact sensing method removes wear entirely, as there are no moving parts or electrical contacts in the trigger mechanism itself.

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

Solution Approach 2:

The patent introduces a magnet as an intermediary between the trigger and the sensor. The magnet carries the positional information without physical contact, allowing the Hall effect sensor to detect trigger position through magnetic field changes rather than direct mechanical or electrical contact.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Adaptability or versatility

If a potentiometer with limited stroke is used, then the control range is restricted, but the component size is reduced

Engineering Contradiction:
Improvecontrol rangeVSAvoidcomponent size
Core Design Contradiction:
Adaptability or versatilityVSVolume of moving object

Solution Approach 1:

The patent changes from measuring physical displacement (potentiometer stroke) to measuring magnetic field variations (Hall effect sensor output). This allows for extended effective stroke since the magnet can move through a larger range while the sensor detects subtle magnetic field changes, increasing control range without proportionally increasing component size.

Inventive Principle:
Principle #35Parameter changes

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 combination of a linear Hall effect sensor and activation switch provides a reliable and compact trigger mechanism that enhances control variability and reduces wear, improving the overall performance and safety of powered devices.

Implementation Method 1

a linear Hall effect sensor for measuring a change in a magnetic field associated with the trigger being moved from the first position to the at least one second position

Methodology Applied
Scientific EffectHall effect: Hall Effect

Data Source

PatentEP3935725B1Trigger apparatus for powered device, powered device, and method of controlling an operation of a powered device
Publication Date: 2025.07.23 MIRKA OY
  • EP3935725B1 patent drawingFigure 1
  • EP3935725B1 patent drawingFigure 2A~2C
  • EP3935725B1 patent drawingFigure 3A~3C

AI summary

A trigger apparatus for a powered device, such as a power tool is disclosed. The powered device comprises a trigger operable by a user to move from a first position to at least one second position so as to control an operation of the powered device. The trigger apparatus comprises: a linear Hall effect sensor for measuring a change in a magnetic field associated with the trigger being moved from the first position to the at least one second position,and configured to generate a sensor signal based on the measured magnetic field, for controlling the operation of the powered device; a power module configured to power,the linear Hall effect sensor, upon reception of an activation signal for indicating that the trigger apparatus is to be activated; and an activation switch configured to generate the activation signal, when the trigger is moved from the first position. A powered device comprising the trigger apparatus and a method of controlling an operation of a powered device are also disclosed.