Apparatus and method for detecting dangerous conditions in power equipment
Woodworking machines are disclosed having electrically conductive cutting tools adapted to cut workpieces. The machines include a contact detection system capacitively coupled to the cutting tool, and adapted to detect contact between a person and the cutting tool. The machines also include a reaction system configured to cause one or more predetermined actions to take place upon detection of contact between a person and the cutting tool by the contact detection system.
1. A woodworking machine comprising:
a motor;
an electrically isolated arbor configured to be driven by the motor;
a cutting tool coupled to the arbor;
an excitation system adapted to generate an electrical signal;
a capacitive coupling adapted to capacitively couple the excitation system to the arbor to transfer at least a portion of the electrical signal to the cutting tool, where the capacitive coupling includes a conductive plate substantially encircling the arbor; and
an insulator substantially encircling the conductive plate.
2. The woodworking machine of claim 1 further comprising an opening in the insulator so that the excitation system can electrically couple to the conductive plate.
3. The woodworking machine of claim 1 further comprising a detection system configured to detect a dangerous condition between a person and the cutting tool and a second conductive plate adjacent the arbor.
4. The woodworking machine of claim 3 where the second conductive plate substantially encircles the arbor, and where the insulator substantially encircles the second conductive plate.
5. The woodworking machine of claim 4 further comprising an opening in the insulator so that the detection system can electrically couple to the second conductive plate.
6. The woodworking machine of claim 4 further comprising a first opening in the insulator so that the excitation system can electrically couple to the conductive plate and a second opening in the insulator so that the detection system can electrically couple to the second conductive plate.
7. The woodworking machine of claim 1 further comprising an arbor block adapted to support the arbor, and where the arbor block also supports the insulator.
8. The woodworking machine of claim 7 where the arbor block includes two spaced-apart support members and the insulator is held by the two spaced-apart support members.
9. The woodworking machine of claim 7 where the insulator supports the conductive plate.