Apparatus and method for detecting dangerous conditions in power equipment

• US 20100180739A1
• Filed: 01/04/2010
• Published: 07/22/2010
• Est. Priority Date: 08/14/2000
• Status: Active Grant

• Current Assignee: Sawstop Holding LLC
• Original Assignee: SD3, LLC
• Inventors: Gass, Stephen F.
• Granted Patent: US 8,006,595 B2
• Time in Patent Office: Days
• US Class Current: 83/58
• 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: B23Q 11/0082 by determining whether the operator is in a dangerous position B23Q17/2438 takes precedence
• 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 3/145 using magnetic technology
• 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 83/089 Responsive to tool characteristic
• CPC Class Codes: Y10T 83/707 By endless band or chain knife
• CPC Class Codes: Y10T 83/7693 Tool moved relative to work-support during cutting
• CPC Class Codes: Y10T 83/7726 By movement of the tool
• CPC Class Codes: Y10T 83/7788 Tool carrier oscillated or rotated

Abstract

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.

Claims

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.

10. A band saw comprising:

a motor;

at least two spaced-apart wheels, where at least one wheel is driven by the motor;

a band blade extending around the wheels, where the band blade is electrically isolated;

signal generation circuitry adapted to generate an electrical signal;

a capacitive coupling adapted to capacitively couple the signal generation circuitry to the band blade to transfer at least a portion of the electrical signal to the band blade; and

detection circuitry configured to monitor the electrical signal on the band blade for changes indicative of a dangerous condition between a person and the band blade and to trigger some action to mitigate the dangerous condition when the changes indicative of the dangerous condition are detected.

11. The band saw of claim 10 further comprising a second capacitive coupling adapted to capacitively couple the detection circuitry to the band blade so that the detection circuitry can monitor the electrical signal on the band blade through the second capacitive coupling.

12. The band saw of claim 10 where the capacitive coupling includes two spaced-apart conductors, and where the blade is one of the two conductors and a charge plate adjacent the blade is the other of the two conductors.

13. The band saw of claim 12 where the charge plate is adjacent a portion of the band blade extending around one of the wheels.

14. The band saw of claim 12 where the charge plate is adjacent a portion of the band blade extending between the wheels.

15. The band saw of claim 12 further comprising a second capacitive coupling adapted to capacitively couple the detection circuitry to the band blade so that the detection circuitry can monitor the electrical signal on the band blade through the second capacitive coupling, where the second capacitive coupling includes two spaced-apart conductors, and where the blade is one of the two conductors and a charge plate adjacent the blade is the other of the two conductors.

16. A woodworking machine comprising:

a motor;

a cutting tool driven by the motor, where the cutting tool is electrically isolated;

an excitation system adapted to generate an electrical signal;

a capacitive coupling adapted to capacitively couple the excitation system to the cutting tool to transfer at least a portion of the electrical signal to the cutting tool, where the capacitive coupling includes a conductive plate adjacent the cutting tool; and

an insulating spacer intermediate the cutting tool and conductive plate.

17. The woodworking machine of claim 16 where the cutting tool has two sides and the conductive plate and insulating spacer are adjacent one side of the cutting tool, and further comprising at least one additional spacer adjacent the other side of the cutting tool.

18. The woodworking machine of claim 16 where the insulating spacer is a dielectric.

19. A woodworking machine comprising:

a motor;

a cutting tool driven by the motor, where the cutting tool is electrically isolated;

an excitation system adapted to generate an electrical signal;

means for capacitively coupling the excitation system to the cutting tool to transfer at least a portion of the electrical signal to the cutting tool; and

means for positioning the capacitive coupling means in an operable configuration in the woodworking machine.

20. The woodworking machine of claim 19 where the means for capacitively coupling the excitation system to the cutting tool includes at least one charge plate, and where the means for positioning the capacitive coupling means in an operable configuration includes at least one support member.