Table Saw Motor Shutdown by Workpiece Unloading Detection

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Solution Overview

Problem

Table tools face inefficiencies and safety hazards due to the inability to automatically shut down after completing large workpiece cuts, leading to power waste and user inconvenience.

Innovation Solution

A table tool with a controller, sensing device, and switch configuration that allows for automatic motor shutdown based on sensing the unloading of a workpiece, enabling two working modes: intelligent mode for automatic shutdown and normal mode for manual control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If manual switch operation is used for small workpieces, then ease of operation is maintained, but power waste and safety hazards occur when handling large workpieces

Engineering Contradiction:

Improvepower wasteVSAvoidmanual switch operation convenience

Core Design Contradiction:

Loss of energyVSEase of operation

Solution Approach 1:

The system automatically detects workpiece removal via the sensing device and shuts down the motor without requiring manual intervention. The table tool serves itself by monitoring its own operational state and autonomously transitioning from active to idle mode, eliminating the need for user action while preventing power waste.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The sensing device provides continuous feedback about the workpiece state to the controller. When the workpiece is detected as removed or unloaded, this feedback signal triggers the controller to shut down the motor. This closed-loop feedback mechanism ensures automatic power conservation while maintaining operational simplicity.

Inventive Principle:

Principle #23Feedback

2Loss of energy

If automatic shutdown based on sensing device is implemented, then power waste is reduced, but device complexity increases

Engineering Contradiction:

Improvepower wasteVSAvoidcontroller and sensing device configuration

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The manual mechanical switch operation is replaced with an automated sensing and control system. The sensing device detects workpiece presence or removal state, and the controller automatically processes this information to control motor shutdown, substituting mechanical user action with automated electromechanical systems.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The controller integrates multiple functions: it receives signals from the sensing device, processes workpiece state information, controls motor operation, and manages shutdown sequences. This multi-functional integration reduces the need for separate dedicated components for each function, thereby limiting the increase in overall device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Measurement precision

If sensing device is positioned close to saw blade for accurate detection, then measurement precision is improved, but safety hazards increase due to proximity to moving blade

Engineering Contradiction:

Improveworkpiece state detection accuracyVSAvoidsafety hazards from blade proximity

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The sensing device acts as an intermediary that indirectly detects workpiece state without requiring direct contact or extreme proximity to the saw blade. It senses changes in the work environment (such as presence, position, or removal state of the workpiece) and translates these into electrical signals for the controller, enabling accurate detection while maintaining safety distance.

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 ensures efficient power management, improved user safety, and convenience by automatically shutting down the tool after completing a cut, reducing power waste and enhancing user experience, especially when handling large workpieces.

Implementation Method 1

The sensor includes a capacitive proximity switch

Methodology Applied

Scientific EffectCapacitive sensing: Capacitance

Implementation Method 2

The sensor includes an inductive proximity switch

Methodology Applied

Scientific EffectInductive sensing: Electromagnetic Induction

Implementation Method 3

The sensor includes a photoelectric switch

Methodology Applied

Scientific EffectPhotoelectric sensing: Photoelectric Effect

Data Source

PatentUS20230166343A1Table tool and control method therefor

Publication Date: 2023.06.01 NANJING CHERVON IND

AI summary

A table tool includes a table, a saw blade, a motor, a controller, a sensing device and a first switch. The table has a work plane on which a workpiece is placed. The saw blade acts on the workpiece. The motor drives the saw blade to rotate. The controller is used for controlling rotation of the motor. The sensing device is electrically connected to the controller and used for sensing a state of the workpiece and outputting a first signal to the controller. The first switch is used for a user to select a working mode from at least two working modes of the table tool. When the table tool is in a first working mode, the controller is configured to adjust a rotational speed of the motor to be a first rotational speed based on an acquired first signal or a working parameter of the motor.