Safety system and method for cutting machine

Abstract

A safety system prevents cutting machine operators from being accidentally carried through the infeed chute into the machine's cutting mechanism. An operator wears a safety device on his wrist and/or ankle and a sensor array mounts on opposing sides of the cutting machine's infeed chute. The sensor array elements are wound in opposite directions and connect in series opposing. The magnetic field of the safety device induces a current in the sensor array as it moves in the proximity of the sensor array. The safety system generates a signal which is proportional to the sum of the induced currents. When the signal exceeds a threshold, the safety system shuts off power to the feed mechanism and/or the cutting blades of the cutting machine, preventing injury to the operator.

What is claimed is: 
     
         1 . A safety system for a machine comprising:
 a sensor array comprising at least two sensor elements having conductive windings, each sensor element comprising a protective plate and a conductive winding, each conductive winding comprising at least one loop of wire, the sensor elements mounted on opposing sides of an infeed chute;   a sensor circuit configured to sense a current induced in the conductive windings by a magnetic field of a magnetic safety device, the current induced by moving the magnetic safety device proximate to the sensor array, the sensor circuit further comprising an amplifier that generates an amplified signal proportional to the current; and   a comparator to compare the amplified signal to a threshold value, wherein the operation of the machine is interrupted when the amplified signal is greater than the threshold value.   
     
     
         2 . The safety system of  claim 1 , wherein the amplifier is configured to amplify the amplified signal proportional to a voltage potential induced in the conductive windings. 
     
     
         3 . The safety system of  claim 1 , wherein the conductive winding of the first sensor element is wound in a different direction than the conductive winding of the second sensor element. 
     
     
         4 . The safety system of  claim 1 , wherein at least one conductive winding is wound clockwise and at least another conductive winding is wound counterclockwise. 
     
     
         5 . The safety system of  claim 1 , wherein the threshold value comprises a positive set point and a negative set point, and shutting off power to the machine when the amplified signal is greater than the positive set point or less than the negative set point. 
     
     
         6 . The safety system of  claim 1  further comprising a threshold circuit configured to generate a predetermined threshold value. 
     
     
         7 . The safety system of  claim 1  further comprising a shut-off circuit to terminate operation of the machine when the amplified signal is greater than the threshold value. 
     
     
         8 . The safety system of  claim 1 , wherein the current is induced by moving the magnetic field between the at least first sensor array element and the at least second sensor array element. 
     
     
         9 . The safety system of  claim 1  further comprising a reset switch mounted externally to the infeed chute of the machine, the reset switch configured to restart the operation of the machine in response to pressing. 
     
     
         10 . A method of controlling a machine comprising:
 sensing a current induced in a sensor array, the sensor array comprising at least two sensor elements having conductive windings, each sensor element comprising a protective plate and a conductive winding, each conductive winding comprising at least one loop of wire, the sensor elements mounted on opposing sides of an infeed chute, wherein the current is induced by moving the magnetic safety device proximate to the sensor array;   generating an amplified signal proportional to the current;   a comparator to compare the amplified signal to a threshold value; and   interrupting operation of the machine when the amplified signal is greater than the threshold value.   
     
     
         11 . The method of  claim 10 , comprising amplifying the amplified signal proportional to a voltage potential induced in the conductive windings. 
     
     
         12 . The method of  claim 10 , comprising winding the conductive winding of the first sensor element in a different direction than the conductive winding of the second sensor element. 
     
     
         13 . The method of  claim 10 , comprising winding at least one conductive winding clockwise and at least another conductive winding counterclockwise. 
     
     
         14 . The method of  claim 10 , wherein the threshold value comprises a positive set point and a negative set point, and shutting off the machine when the amplified signal is greater than the positive set point or less than the negative set point. 
     
     
         15 . The method of  claim 10  further comprising generating a predetermined threshold value. 
     
     
         16 . The method of  claim 10  further comprising shutting off the machine when the amplified signal is greater than the threshold value. 
     
     
         17 . The method of  claim 10 , wherein the current is induced by moving the magnetic field between the at least first sensor array element and the at least second sensor array element. 
     
     
         18 . The method of  claim 10  further comprising restarting the operation of the machine in response to pressing a reset switch mounted externally to the infeed chute of the machine.