Detection system for power tool

Abstract

Power tool includes a movable blade and a detection system for detecting contact between the blade and an object. Detection system includes an excitation plate capacitively coupling the drive signal to the movable blade. A circuit generates an in phase component signal and a quadrature component signal from a blade current signal indicative of the instantaneous current drawn by the movable blade and calculates an energy of the blade current signal considering the in-phase and the quadrature components. The circuit compares the energy of the blade current signal to an adaptive trigger threshold to detect contact between the blade and the object based on whether the energy of the blade current signal is greater than the adaptive trigger threshold.

Description

Background technique [0001] Detection or sensing systems have been developed for various manufacturing equipment and power tools. Such a detection system is operable to trigger some type of condition mitigation mechanism by detecting or sensing an operator approaching or an operator contacting a certain part of the equipment. For example, it is known to use capacitive touch sensing systems in table saws to detect operator contact with the blade. However, such systems have difficulty distinguishing certain materials that may cause false activation of state mitigation mechanisms. Accordingly, there is a need for improved and more robust capacitive touch sensing systems. Contents of the invention [0002] In one general aspect, the present invention relates to a power tool having an improved detection system capable of distinguishing between a movable blade of the power tool and a first object believed to cause activation of a condition mitigation system or "reaction system" ...

AI Technical Summary

Problems solved by technology

However, such systems have difficulty distinguishing certain materials that may cause false activation of state mitigation mechanisms

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