Contact detection system for power equipment

• US 7,377,199 B2
• Filed: 01/16/2002
• Issued: 05/27/2008
• Est. Priority Date: 09/29/2000
• Status: Expired due to Term

• Current Assignee: Sawstop Holding LLC
• Original Assignee: SD3, LLC
• Inventors: Gass, Stephen F., Fulmer, J. David
• Primary Examiner(s): Alie; Ghassem
• Application Number:
  US10/053,390
• Publication Number:
  US 20020069734A1
• Time in Patent Office: 2,323 Days
• Field of Search: 324/678, 324/658, 324/686, 324/660, 324/775, 324/706, 324/725, 83/621, 83D/IG.31, 833/97, 834/771, 834/713, 836/30, 83/58, 832/97, 836/44, 83/13, 83D/IG.1, 833/971, 834/712, 834/772, 834/90, 835/81, 317/146, 317/DIG.2, 317/153, 317/123
• US Class Current: 83/13
• CPC Class Codes: B23D 45/06 with a circular saw blade arranged underneath a stationary work-table
• CPC Class Codes: B23D 47/08 of devices for bringing the circular saw blade to the workpiece or removing same therefrom
• CPC Class Codes: B23D 55/08 of devices for guiding or feeding strap saw blades
• CPC Class Codes: B23D 59/001 Measuring or control devices, e.g. for automatic control of work feed pressure on band saw blade measuring in general G01; controlling in general G05
• CPC Class Codes: B27B 13/14 Braking devices specially designed for band sawing machines, e.g. acting after damage of the band saw blade
• CPC Class Codes: B27B 5/38 Devices for braking the circular saw blade or the saw spindle; Devices for damping vibrations of the circular saw blade, e.g. silencing B23D47/005 takes precedence
• CPC Class Codes: B27G 19/00 Safety guards or devices specially adapted for wood saws; Auxiliary devices facilitating proper operation of wood saws
• CPC Class Codes: B27G 19/02 for circular saws
• 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 83/04 Processes
• CPC Class Codes: Y10T 83/081 With randomly actuated stopping means
• CPC Class Codes: Y10T 83/088 Responsive to tool detector or work-feed-means detector
• CPC Class Codes: Y10T 83/089 Responsive to tool characteristic
• CPC Class Codes: Y10T 83/613 Work guard
• CPC Class Codes: Y10T 83/7693 Tool moved relative to work-support during cutting
• CPC Class Codes: Y10T 83/773 Work-support includes passageway for tool [e.g., slotted table]
• CPC Class Codes: Y10T 83/7763 Tool carrier reciprocable rectilinearly
• CPC Class Codes: Y10T 83/7788 Tool carrier oscillated or rotated
• CPC Class Codes: Y10T 83/8773 : Bevel or miter cut

Abstract

A woodworking machine having one or more dangerous portions of the machine is disclosed. The machine also includes a safety system configured to detect accidental contact between a person and at least one of the dangerous portions by electrically coupling a signal to the person'"'"'s body, and detecting if the signal becomes coupled to the dangerous portion.

Claims

1. A method for detecting accidental contact between a person and a dangerous portion of a woodworking machine, the method comprising:

providing a first electrode electrically coupled to the person;

providing a second electrode electrically coupled to the dangerous portion;

transmitting a signal by one of the first or second electrodes;

receiving the transmitted signal by the other of the first or second electrodes; and

performing a step of sampling the signal a plurality of times to determine if the signal has at least one predetermined characteristic indicative of contact between a person and the dangerous portion.

2. A method for detecting accidental contact between a person and a dangerous portion of a woodworking machine, the method comprising:

providing a first electrode electrically coupled to the person;

providing a second electrode electrically coupled to the dangerous portion;

transmitting a signal by one of the first or second electrodes;

detecting whether the transmitted signal is received by the other of the first or second electrodes; and

if so,

sampling the signal a plurality of times within 200 microseconds to determine if the signal has at least one predetermined characteristic indicative of contact between a person and the dangerous portion.

3. The method of claim 2, where the step of transmitting includes transmitting the signal by the first electrode through the person.

4. The method of claim 2, where the step of transmitting includes transmitting the signal by the second electrode through the dangerous portion.

5. The method of claim 2, where the woodworking machine includes at least one cutting tool, and where the step of providing a second electrode includes providing a second electrode electrically coupled to the at least one cutting tool.

6. The method of claim 2, where the woodworking machine includes at least one guard, and where the step of providing a second electrode includes providing a second electrode electrically coupled to the at least one guard.

7. The method of claim 2, where the step of transmitting includes transmitting an alternating electrical signal.

8. The method of claim 7, where the alternating electrical signal has a particular frequency, and further comprising identifying contact if an electrical signal having the particular frequency is received.

9. The method or claim 2, where the step of transmitting includes transmitting a ground electrical signal.

10. The method of claim 2, where the dangerous portion is a blade with cutting teeth, and where the sampling occurs while a single tooth is in contact with the person.

11. The method of claim 2, where the sampling occurs within 100 microseconds.

12. The method of claim 2, where the sampling occurs in less than 100 microseconds.

13. The method of claim 2, where the predetermined characteristic indicative of contact between a person and the dangerous portion distinguishes such contact from proximity between a person and the dangerous portion.

14. The method of claim 13, where the predetermined characteristic indicative of contact between a person and the dangerous portion involves peak-to-peak amplitude.

15. The method of claim 13, where the predetermined characteristic indicative of contact between a person and the dangerous portion involves phase.

16. The method of claim 13, where the predetermined characteristic indicative of contact between a person and the dangerous portion involves a positive value.

17. The method of claim 13, where the predetermined characteristic indicative of contact between a person and the dangerous portion involves a negative value.