Discrete proximity detection system

• US 7,171,879 B2
• Filed: 07/02/2002
• Issued: 02/06/2007
• Est. Priority Date: 07/02/2001
• Status: Expired due to Term

• Current Assignee: Sawstop Holding LLC
• Original Assignee: SD3, LLC
• Inventors: Gass, Stephen F., Fulmer, J. David
• Primary Examiner(s): Ashley; Boyer D.
• Assistant Examiner(s): Alie; Ghassem
• Application Number:
  US10/189,031
• Publication Number:
  US 20030002942A1
• Time in Patent Office: 1,680 Days
• Field of Search: 83/621, 83/58, 834/713, 834/771, 834/90, 835/89, 835/81, 833/97, 833/971, 834/772, 836/30, 832/92, 836/44, 83D/IG.1, 837/88, 834/76, 835/26, 834/91, 83/768, 83/72, 834/85, 834/87, 835/46, 835/90, 836/65, 324/678, 324/658, 324/686, 324/660, 324/725, 324/706, 408/710, 317/146, 317/153, 317/DIG.2, 317/123, 403/2, 403/28, 307/326, 307/142, 307/110, 307/121
• US Class Current: 83/58
• CPC Class Codes: B23Q 5/58 Safety devices protecting the operator B23Q11/0089
• CPC Class Codes: B27G 21/00 Safety guards or devices specially designed for other wood-working machines auxiliary devices facilitating proper operation of said wood-working machines
• CPC Class Codes: F16P 3/12 with means, e.g. feelers, which in case of the presence of a body part of a person in or near the danger zone influence the control or operation of the machine F16P3/08 takes precedence
• CPC Class Codes: F16P 3/148 using capacitive technology
• CPC Class Codes: Y10S 83/01 Safety devices
• CPC Class Codes: Y10T 408/96 Miscellaneous
• CPC Class Codes: Y10T 83/04 Processes
• CPC Class Codes: Y10T 83/081 With randomly actuated stopping means
• CPC Class Codes: Y10T 83/089 Responsive to tool characteristic
• CPC Class Codes: Y10T 83/707 By endless band or chain knife
• CPC Class Codes: Y10T 83/7726 By movement of the tool
• CPC Class Codes: Y10T 83/773 Work-support includes passageway for tool [e.g., slotted table]
• CPC Class Codes: Y10T 83/7788 Tool carrier oscillated or rotated

Abstract

A machine is described having at least one dangerous portion. The machine also includes a safety system to detect dangerous proximity between a person and the dangerous portion and perform a predetermined action to limit or prevent injury to the person from the dangerous portion.

Claims

1. For use on power equipment having at least one dangerous portion, a method of detecting dangerous proximity between a person and the dangerous portion, the method comprising:

generating a high voltage;

applying the high voltage to the dangerous portion, where the high voltage is sufficient to cause an electrical discharge arc between the dangerous portion and the person'"'"'s body when a portion of the person'"'"'s body comes within a predetermined distance from the dangerous portion, and where the high voltage on the dangerous portion has an expected amplitude;

providing an electronic circuit adapted to detect when an electrical discharge arc between the dangerous portion and the person'"'"'s body occurs by monitoring the voltage amplitude on the dangerous portion;

detecting through the electronic circuit when an electrical discharge arc between the dangerous portion and the person'"'"'s body occurs by monitoring the voltage amplitude on the dangerous portion and comparing that voltage amplitude with the expected amplitude; and

triggering an action to mitigate potential injury when the monitored voltage amplitude departs from the expected amplitude greater than a predetermined threshold amount.

2. The method of claim 1, where the power equipment is a woodworking machine and the dangerous portion is a cutting tool.

3. The method of claim 1, where the limitation of generating a high voltage includes generating a DC voltage.

4. The method of claim 3, where the step limitation of generating a high voltage includes generating an intermittent DC voltage.

5. The method of claim 1, where the step limitation of generating a high voltage includes generating an AC voltage.

6. The method of claim 1, where the predetermined distance is at least approximately 0.1 millimeter and less than approximately 20 millimeters.

7. The method of claim 1, where the predetermined distance is at least approximately 1 millimeter and less than approximately 4 millimeters.

8. The method of claim 1, where the high voltage is generated by an electronic ignition type high voltage power supply.

9. The method of claim 1, where the high voltage is generated by a flyback transformer type high voltage power supply.

10. The method of claim 1, where the high voltage is generated by a spark gap circuit type high voltage power supply.

11. The method of claim 1, where the high voltage is generated by a regulated high voltage power supply.

12. The method of claim 1, where the high voltage is pulsed and the frequency of pulsing is at least 100 cycles per second.

13. The method of claim 1, where the high voltage is pulsed and the frequency of pulsing is at least 500 cycles per second.

14. The method of claim 1, where the sign of the high voltage is alternated.

15. The method of claim 1, where the limitation of detecting through the electronic circuit when an electrical discharge arc between the dangerous portion and the person'"'"'s body occurs senses the sign of the electric discharge.

16. The method of claim 1, where the limitation of detecting through the electronic circuit when an electrical discharge arc between the dangerous portion and the persons body occurs senses the rate of the electric discharge.

17. The method of claim 1, where the limitation of detecting through the electronic circuit when an electrical discharge arc between the dangerous portion and the person'"'"'s body occurs senses the rise time of the current of the electric discharge.