Saw Blade Speed Feedback for Automatic Kickback Detection

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Solution Overview

Problem

Existing power tools, such as circular saws, cannot detect kickback events automatically and thus cannot initiate mitigation measures without operator intervention, leading to potential accidents.

Innovation Solution

A non-destructive method for detecting kickback in circular saws and other power tools, which involves using a digital controller to monitor the saw blade's rotational speed, detect changes, and autonomously deactivate the motor or engage a blade arrest mechanism to mitigate kickback without requiring manual intervention.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If existing power tools use manual kickback mitigation devices (riving knives, guide rails), then kickback occurrences are reduced, but the system cannot automatically detect or respond to kickback events

Engineering Contradiction:

Improvekickback mitigation effectivenessVSAvoidautomatic kickback detection

Core Design Contradiction:

ReliabilityVSExtent of automation

Solution Approach 1:

The system continuously monitors blade speed and compares it against expected operational ranges, creating a feedback loop that automatically detects kickback events and triggers mitigation responses without operator intervention

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The power tool autonomously monitors its own operational state through blade speed sensing and automatically initiates kickback mitigation measures, enabling the system to protect itself without external intervention

Inventive Principle:

Principle #25Self-service

2Object-affected harmful factors

If the system autonomously deactivates the motor upon kickback detection, then safety is improved, but the tool requires additional sensors and control systems

Engineering Contradiction:

Improvekickback accident riskVSAvoiddetection and control system

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The system replaces complex mechanical kickback mitigation mechanisms with an electronic sensing and control system that uses blade speed monitoring to detect and respond to kickback events, reducing mechanical complexity while improving response capability

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 rapid detection and mitigation of kickback events, reducing the risk of accidents by automatically disengaging the saw motor within a short time frame, even if the operator continues to activate the saw.

Implementation Method 1

a blade speed sensor of the group consisting of an encoder, a Hall effect sensor, a strobe sensor, and a shaker sensor

Methodology Applied

Scientific EffectRotational speed sensing:

Data Source

PatentUS11571831B2System and method for kickback detection based on blade speed in a power tool

Publication Date: 2023.02.07 ROBERT BOSCH TOOL

AI summary

A method of detecting and mitigating kickback in a saw includes identification of a running average speed (RPM) of a saw blade, the speed at a given time sample relative to the running average speed, the percentage change in speed from one speed sample to the previous speed sample, and the percentage change in average speed based on the current speed of the saw blade. If the identified speed profile from the samples indicates a kickback is imminent, then the saw identifies an imminent kickback event and removes power from the saw motor to mitigate kickback.