Apparatus and method for detecting dangerous conditions in power equipment

Abstract

A machine such as a saw, jointer, planer, etc. is disclosed. The machine has cutting tool, a direct drive mechanism configured to move the cutting tool, a detection system adapted to detect the occurrence of an unsafe condition between a person and the cutting tool, and a reaction system adapted to mitigate the unsafe condition upon the detection of the unsafe condition by the detection system. An electrical signal is imparted on the cuffing tool, and the signal is used to determine the occurrence of the unsafe condition. The direct drive mechanism is electrically isolated so that the electric signal may be imparted on the cutting tool. The electric isolation may be achieved through configurations such as insulated bearings, a substantially non-conductive housing, and a substantially non-conductive coupling joining two shaft portions.

We claim:  
     
         1 . A saw comprising: 
 a circular blade adapted to spin;    a motor configured to spin the blade;    a detection system adapted to detect contact between the blade and a person, where the detection system is adapted to impart an electrical signal on the blade;    a reaction system adapted to stop the blade from spinning upon the detection of the contact by the detection system; and    a direct drive system interconnecting the a motor and the blade, where the direct drive system includes at least two shaft portions coupled by a substantially nonconductive coupling.    
     
     
         2 . The saw of  claim 1 , where the non-conductive coupling is a gear, and where at least a portion of the gear is made of a substantially non-conductive material.  
     
     
         3 . The saw of  claim 2 , where the portion of the gear made of a substantially non-conductive material is sandwiched between metal portions.  
     
     
         4 . The saw of  claim 2 , where the gear includes metal teeth and a substantially non-conductive portion isolating the metal teeth.  
     
     
         5 . The saw of  claim 2 , where the gear is made at least substantially from a substantially non-conductive material.  
     
     
         6 . The saw of  claim 1 , where the non-conductive coupling includes a gear, a substantially non-conductive spacer that mates with the gear, and a drive hub mounted to the spacer.  
     
     
         7 . The saw of  claim 6 , where the gear and drive hubs are mounted on shaft portions, where the shaft portions are supported by bearings, and where the bearings are supported in insulating bushings.  
     
     
         8 . The saw of  claim 6 , where the gear and drive hubs are mounted on shaft portions, where the shaft portions are supported by bearings, and where insulating bushings are positioned between the shaft portions and the bearings.  
     
     
         9 . The saw of  claim 1 , where the non-conductive coupling includes a eccentric portion, a substantially non-conductive sleeve configured to fit over and insulate the eccentric portion, and a gear configured with an opening to receive the eccentric portion and sleeve.  
     
     
         10 . The saw of  claim 1 , where the substantially non-conductive coupling is a planetary gear assembly.  
     
     
         11 . The saw of  claim 10 , where the planetary gear assembly includes a substantially non-conductive housing.  
     
     
         12 . The saw of  claim 10 , where the planetary gear assembly includes planetary gears made from substantially non-conductive material.  
     
     
         13 . The saw of  claim 1 , where the motor is a switched reluctance motor.  
     
     
         14 . The saw of  claim 1 , further comprising a housing supporting the motor.  
     
     
         15 . A saw comprising: 
 a circular cutting tool, where the cutting tool is adapted to spin;    a direct drive mechanism configured to spin the cutting tool;    a detection system adapted to detect the occurrence of an unsafe condition between a person and the cutting tool, where the detection system is adapted to impart an electrical signal on the cutting tool; and    a reaction system adapted to mitigate the unsafe condition upon the detection of the unsafe condition by the detection system;    where the direct drive mechanism is electrically isolated so that the electric signal may be imparted on the cutting tool.    
     
     
         16 . The saw of  claim 15 , where the direct drive mechanism is in a substantially non-conductive container, and the container is mounted in the operative structure.  
     
     
         17 . The saw of  claim 15 , where the direct drive mechanism includes a switched reluctance motor and an electrically isolated drive shaft.  
     
     
         18 . The saw of  claim 15 , where the direct drive mechanism includes a electrically isolated drive shaft.  
     
     
         19 . The saw of  claim 15 , further comprising a housing supporting the direct drive mechanism.  
     
     
         20 . A saw comprising: 
 a circular cutting tool adapted to spin;    at least one motor configured to move the cutting tool;    a detection system adapted to detect the occurrence of an unsafe condition between a person and the cutting tool, where the detection system is adapted to impart an electrical signal on the cutting tool;    a reaction system adapted to mitigate the unsafe condition upon the detection of the unsafe condition by the detection system; and    means for electrically isolating the cutting tool so that the electric signal may be imparted on the cutting tool.