Kickback detection system

Patent metadata

Field	Value
Publication number	US-9586336-B2
Application number	US-201314140735-A
Country	US
Kind code	B2
Filing date	Dec 26, 2013
Priority date	Dec 31, 2012
Publication date	Mar 7, 2017
Grant date	Mar 7, 2017

Abstract

A method of detecting a kickback event for a table saw includes operatively connecting a stress sensor to the table saw that is configured to detect a characteristic of a work component of the table saw, the work component being coupled to a workpiece being cut by the table saw during a cutting operation. The stress sensor outputs stress signals indicative of the characteristic of the work component. A speed of the saw blade is then controlled based on the stress signals.

First claim

What is claimed is:

1. A method of detecting a kickback event for a table saw, the table saw including a motor having an arbor shaft for driving a saw blade and a guide fence for guiding a workpiece, the method comprising:
operatively connecting a stress sensor to the table saw, the stress sensor being configured to detect deflection of a work component during a cutting operation, the work component comprising at least one of the arbor shaft and the guide fence;
outputting sensor signals from the stress sensor indicative of the deflection of the work component; and
controlling the saw blade based on the sensor signals.

2. The method of claim 1 , further comprising:
comparing the deflection indicated by the sensor signals to a threshold value for the characteristic; and
adjusting the speed of the saw blade based on the comparison.

3. The method of claim 2 , wherein the threshold value corresponds to a value of the characteristic during a kickback event.

4. The method of claim 3 , wherein adjusting the speed comprises reducing the speed of the motor in response to the deflection indicated by the sensor signals exceeding the threshold value.

5. The method of claim 3 , wherein adjusting the speed comprises actuating a braking mechanism for stopping the saw blade in response to the deflection indicated by the sensor signals exceeding the threshold value.

6. The method of claim 1 , wherein the stress sensor comprises a deflection sensor for indicating a deflection of the work component from a normal position.

7. The method of claim 6 , wherein the deflection sensor comprises at least one of a transducer, a strain gauge, an accelerometer, and an optical sensor.

8. The method of claim 7 , wherein the work component comprises the arbor shaft.

9. The method of claim 8 , wherein the deflection sensor is connected to a bearing that rotatably supports the arbor shaft.

10. The method of claim 7 , wherein the work component comprises the guide fence.

11. The method of claim 3 , wherein the stress sensor comprises a current sensor, and
wherein the sensor signals indicate a current being supplied to the motor, and
wherein the threshold value corresponds to a current level supplied to the motor during a kickback event.

12. A kickback detection system for a table saw having a guide fence and a motor rotatably driving an arbor shaft supported by a bearing, the system comprising:
a stress sensor operatively connected to the table saw, the stress sensor being configured to detect deflection of a work component of the table saw during a cutting operation, the work component comprising at least one of the arbor shaft and the guide fence, the stress sensor outputting sensor signals indicative of the deflection of the work component;
a controller operatively coupled to receive the sensor signals from the stress sensor and to output a speed control signal based on the characteristic indicated by the sensor signals; and
a speed control mechanism operatively coupled to receive the speed control signal and configured to control a speed of the saw blade based on the speed control signal.

13. The system of claim 12 , wherein the controller is configured to compare the deflection indicated by the sensor signals to a threshold value for the characteristic and to output the speed control signal based on the comparison.

14. The system of claim 13 , wherein the threshold value is selected to indicate a kickback event experienced by the work component.

15. The system of claim 14 , wherein the speed control mechanism comprises the motor, the motor being configured to reduce speed in response to the speed control signal.

16. The system of claim 15 , wherein the speed control mechanism comprises a braking mechanism configured to stop rotation of the saw blade in response to the speed control signal.

17. The system of claim 14 , wherein the stress sensor comprises a deflection sensor for indicating a deflection of the work component from a normal position.

18. The system of claim 17 , wherein the deflection sensor comprises at least one of a transducer, a strain gauge, an accelerometer, and an optical sensor.

19. The system of claim 18 , wherein the work component comprises the arbor shaft.

20. The system of claim 18 , wherein the work component comprises the guide fence.

Assignees

• Bosch Tool Corp
• Bosch Gmbh Robert

Inventors

• Mehta Amit
• Wiker Juergen

Classifications

• F16P3/14

  the means being photocells or other devices sensitive without mechanical contact · CPC title

• Y10T83/04

  Processes · CPC title

• Y10T83/541

  Actuation of tool controlled in response to work-sensing means · CPC title

• B27B5/222

  the saw blade being arranged underneath the work-table; Guiding arrangements for the work-table · CPC title

• B27G19/02 Primary

  for circular saws · CPC title