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A detection system for detecting a dangerous condition for an operator using a power tool of the type which has an exposed blade relative to a work surface and a protection system for minimizing, if not eliminating the possibility of a user being injured by contacting the blade. In one preferred emb

A detection system for detecting a dangerous condition for an operator using a power tool of the type which has an exposed blade relative to a work surface and a protection system for minimizing, if not eliminating the possibility of a user being injured by contacting the blade. In one preferred embodiment of the present invention, a proximity detection system is capable of detecting the presence of a user near the blade of a table saw and a protection system that can either retract the blade below the work surface of the table saw or terminate the drive torque to the blade which can result in rapid stopping of the saw blade by a work piece that is being cut.

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1. A sensor arrangement for a table saw comprising: at least one dielectric sensor embedded in a table top of the table saw having a slot opening in which a circular blade is arranged;a deflection plate embedded in the table top, arranged on a side of the at least one dielectric sensor opposite an u

1. A sensor arrangement for a table saw comprising: at least one dielectric sensor embedded in a table top of the table saw having a slot opening in which a circular blade is arranged;a deflection plate embedded in the table top, arranged on a side of the at least one dielectric sensor opposite an upper surface of the table top and electrically insulated from the at least one dielectric sensor; anda ground plane positioned on a side of the deflection plate opposite the at least one dielectric sensor and electrically insulated from the at least one dielectric sensor and the deflection plate,wherein the sensor arrangement is configured to generate a first actuation signal based upon predetermined sensed characteristics relating to a portion of a person in a sensed volume, wherein the at least one dielectric sensor and the deflection plate are both embedded in a composite insulation layer, which defines at least in part the upper surface of the table top. 2. The sensor arrangement of claim 1, wherein the ground plane is embedded in the composite insulation layer. 3. The sensor arrangement of claim 1, wherein the composite insulation layer has a thickness of approximately 0.5 inches and the composite insulation layer substantially encloses the sensing mechanism. 4. The sensor arrangement of claim 1, wherein the ground plane includes a metallic housing that defines a portion of the upper surface and the composite insulation layer is arranged within the metallic housing. 5. The sensor arrangement of claim 1, further comprising a first insulating layer interposed between the at least one dielectric sensor and the deflection plate. 6. The sensor arrangement of claim 5, further comprising a second insulating layer interposed between the deflection plate and the ground plane. 7. The sensor arrangement of claim 1, further comprising circuitry configured to apply an excitation field to the circular blade such that the circular blade functions as an additional sensor. 8. The sensor arrangement of claim 1, wherein: the circular blade defines a cutting plane, and a feed direction is defined generally parallel to said cutting plane; andthe at least one dielectric sensor includes a first sensor spaced apart in the feed direction from a first end of the slot opening. 9. The sensor arrangement of claim 8, wherein the at least one dielectric sensor includes a second sensor spaced apart in the feed direction from a second end of the slot opening. 10. The sensor arrangement of claim 9, wherein the at least one dielectric sensor includes a third sensor and a fourth sensor, the third sensor being spaced apart from a first side of the slot opening and the fourth sensor being spaced apart from a second side of the slot opening. 11. The sensor arrangement of claim 1, wherein the at least one dielectric sensor includes a plurality of sensors arranged in a rectangular array around the slot opening. 12. The sensor arrangement of claim 11, wherein: the plurality of sensors includes first sensors and second sensors; andthe first sensors are smaller than and arranged closer to the slot opening than the second sensors. 13. The sensor arrangement of claim 1, wherein the at least one dielectric sensor includes a first hollow rectangular sensor surrounding the slot opening. 14. The sensor arrangement of claim 13, wherein the at least one dielectric sensor includes a second hollow rectangular sensor surrounding the first sensor. 15. The sensor arrangement of claim 14, wherein the at least one dielectric sensor includes a third hollow rectangular sensor surrounding the second sensor. 16. The sensor arrangement of claim 15, wherein the first hollow rectangular sensor has a first thickness, the second hollow rectangular sensor has a second thickness, and the third hollow rectangular sensor has a third thickness, and the first thickness is greater than the second thickness, which is greater than the third thickness. 17. The sensor arrangement of claim 15, wherein a first spacing between the first hollow rectangular sensor and the second hollow rectangular sensor is less than a second spacing between the second hollow rectangular sensor and the third hollow rectangular sensor. 18. The sensor arrangement of claim 15, wherein a first spacing between the first hollow rectangular sensor and the second hollow rectangular sensor is equal to a second spacing between the second hollow rectangular sensor and the third hollow rectangular sensor. 19. The sensor arrangement of claim 1 further comprising a processor configured to receive sensor signals from the at least one dielectric sensor and generate the first actuation signal based upon the sensor signals. 20. The sensor arrangement of claim 19, wherein the processor is further configured to generate the first actuation signal based upon the sensor signals indicating that the portion of the person is in a highly dangerous position relative to said circular blade. 21. The sensor arrangement of claim 20, wherein the sensor signals indicate a position and a velocity of the portion of the person in the sensed volume. 22. A table saw comprising: a frame structure including a table top defining a slot opening and having an upper surface;a rotatable circular blade configured such that at least a portion of said circular blade is positionable above the upper surface;a drive motor including an output shaft, supported by the frame structure, and configured to rotatably drive the circular blade;a sensing mechanism configured to generate a first actuation signal based upon predetermined sensed characteristics relating to a portion of a person in a sensed volume; anda retracting mechanism configured to rapidly move the blade downwardly below the upper surface based upon said first actuation signal,wherein the sensing mechanism includes: at least one dielectric sensor embedded in the table top;a deflection plate embedded in the table top, arranged on a side of the at least one dielectric sensor opposite the upper surface of the table top, and electrically insulated from the at least one dielectric sensor; anda ground plane positioned on a side of the deflection plate opposite the at least one dielectric sensor and electrically insulated from the at least one dielectric sensor and the deflection plate, wherein the at least one dielectric sensor and the deflection plate are both embedded in a composite insulation layer of the top table, which defines at least in part the upper surface. 23. The table saw of claim 22, wherein the ground plane is embedded in the composite insulation layer of the table top that defines the upper surface. 24. The table saw of claim 22, wherein the composite insulation layer of the table top has a thickness of approximately 0.5 inches and the composite insulation layer substantially encloses the sensing mechanism. 25. The table saw of claim 22, wherein the ground plane includes a metallic housing that forms a portion of the upper surface and the composite insulation layer is arranged within the metallic housing. 26. The table saw of claim 22, further comprising a first insulating layer interposed between the at least one dielectric sensor and the deflection plate. 27. The table saw of claim 26, further comprising a second insulating layer interposed between the deflection plate and the ground plane. 28. The table saw of claim 22, further comprising circuitry configured to apply an excitation field to the circular blade such that the circular blade functions as an additional sensor. 29. The table saw of claim 22, wherein: the circular blade defines a cutting plane, and a feed direction is defined generally parallel to said cutting plane; andthe at least one dielectric sensor includes a first sensor spaced apart in the feed direction from a first end of the slot opening. 30. The table saw of claim 29, wherein the at least one dielectric sensor includes a second sensor spaced apart in the feed direction from a second end of the slot opening. 31. The table saw of claim 30, wherein the at least one dielectric sensor includes a third sensor and a fourth sensor, the third sensor being spaced apart from a first side of the slot opening and the fourth sensor being spaced apart from a second side of the slot opening. 32. The table saw of claim 22, wherein the at least one dielectric sensor includes a plurality of sensors arranged in a rectangular array around the slot opening. 33. The table saw of claim 32, wherein: the plurality of sensors includes first sensors and second sensors; andthe first sensors are smaller than and arranged closer to the slot opening than the second sensors. 34. The table saw of claim 22, wherein the at least one dielectric sensor includes a first hollow rectangular sensor surrounding the slot opening. 35. The table saw of claim 34, wherein the at least one dielectric sensor includes a second hollow rectangular sensor surrounding the first sensor. 36. The table saw of claim 35, wherein the at least one dielectric sensor includes a third hollow rectangular sensor surrounding the second sensor. 37. The table saw of claim 36, wherein the first, second, and third hollow rectangular sensors all have thicknesses that are substantially equal. 38. The table saw of claim 36, wherein the first hollow rectangular sensor has a first thickness, the second hollow rectangular sensor has a second thickness, and the third hollow rectangular sensor has a third thickness, and the first thickness is greater than the second thickness, which is greater than the third thickness. 39. The table saw of claim 36, wherein a first spacing between the first hollow rectangular sensor and the second hollow rectangular sensor is less than a second spacing between the second hollow rectangular sensor and the third hollow rectangular sensor. 40. The table saw of claim 36, wherein a first spacing between the first hollow rectangular sensor and the second hollow rectangular sensor is equal to a second spacing between the second hollow rectangular sensor and the third hollow rectangular sensor. 41. The table saw of claim 22 further comprising a processor configured to receive sensor signals from the at least one dielectric sensor and generate the first actuation signal based upon the sensor signals. 42. The table saw of claim 41, wherein the processor is further configured to generate the first actuation signal based upon the sensor signals indicating that the portion of the person is in a highly dangerous position relative to said circular blade. 43. The table saw of claim 42, wherein the sensor signals indicate a position and a velocity of the portion of the person in the sensed volume.