Band saw with improved safety system

Abstract

A band saw including a frame, at least two, spaced apart, rotatable wheels supported by the frame, a blade looped around the wheels, where rotation of at least one wheel causes the blade to move around the wheels, a detection system adapted to detect a dangerous condition between a person and the blade, and a reaction system configured to engage and stop the blade within 10 milliseconds after detection of the dangerous condition is disclosed. The reaction system may be configured to cut and grip the blade.

1 . A band saw comprising:
 a motor;   at least two spaced-apart wheels, where at least one wheel is driven by the motor;   a band blade extending around the wheels, where the band blade is electrically isolated;   signal generation circuitry adapted to generate an electrical signal;   a capacitive coupling adapted to capacitively couple the signal generation circuitry to the band blade to transfer at least a portion of the electrical signal to the band blade; and   detection circuitry that monitors the electrical signal on the band blade for changes indicative of a dangerous condition between a person and the band blade, where the detection circuitry triggers some action to mitigate the dangerous condition when the changes indicative of the dangerous condition are detected.   
     
     
         2 . The band saw of  claim 1  further comprising a second capacitive coupling adapted to capacitively couple the detection circuitry to the band blade, and where the detection circuitry monitors the electrical signal on the band blade through the second capacitive coupling. 
     
     
         3 . The band saw of  claim 1  where at least one wheel is mounted for rotation on a shaft, where the capacitive coupling includes two spaced-apart conductors, and where at least a portion of the shaft is one of the two conductors and a charge plate adjacent the shaft is the other of the two conductors. 
     
     
         4 . The band saw of  claim 3  further comprising a second capacitive coupling adapted to capacitively couple the detection circuitry to the band blade, where the detection circuitry monitors the electrical signal on the band blade through the second capacitive coupling, where the second capacitive coupling includes two spaced-apart conductors, and where the shaft is one of the two conductors and a charge plate adjacent the shaft is the other of the two conductors. 
     
     
         5 . A band saw comprising:
 a motor;   a band blade driven by the motor, where the band blade is electrically isolated;   signal generation circuitry adapted to generate an electrical signal;   coupling means for capacitively coupling the signal generation circuitry to the cutting tool to transfer at least a portion of the electrical signal to the cutting tool; and   detection means for monitoring the electrical signal on the cutting tool for changes indicative of a dangerous condition between a person and the cutting tool, and for triggering some action to mitigate the dangerous condition when the changes indicative of the dangerous condition are detected.