Power tool with anti-kickback control system

• US 10,589,413 B2
• Filed: 05/25/2017
• Issued: 03/17/2020
• Est. Priority Date: 06/20/2016
• Status: Active Grant

• Current Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Original Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Inventors: Goble, James E.
• Primary Examiner(s): Smith, Scott A
• Application Number:
  US15/604,728
• Publication Number:
  US 20170361449A1
• Time in Patent Office: 1,027 Days
• Field of Search: 173 1, 173 2, 173 5, 173176, 173178, 173183, 173213, 173217, 173179, 173181, 408 1 R, 408 6, 408 9
• CPC Class Codes: B25B 21/00 Portable power-driven screw or nut setting or loosening tools; details or components, e.g. casings, bodies, of portable power-driven tools not particularly related to the operation performed B25F5/00; for mounting or dismounting wheels B60B29/006; Attachments for drilling apparatus serving the same purpose machines B23P19/06
• CPC Class Codes: B25B 21/002 for special purposes
• CPC Class Codes: B25B 23/147 specially adapted for electrically operated wrenches or screwdrivers
• CPC Class Codes: B25D 2250/221 Sensors
• CPC Class Codes: B25F 5/00 Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for
• CPC Class Codes: B25F 5/001 Gearings, speed selectors, clutches or the like specially adapted for rotary tools
• CPC Class Codes: B25F 5/02 Construction of casings, bodies or handles B25F5/006, B25F5/008 take precedence
• CPC Class Codes: F16P 3/008 Devices for directly stopping or interrupting the drive or gear in case of danger to the machine, e.g. devices with clutches
• CPC Class Codes: G01C 19/08 electrically driven G01C19/14 takes precedence
• CPC Class Codes: G01P 15/00 Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration

Abstract

A power tool includes a housing, a motor received in the housing, an output driven by the motor, and a control system. The control system includes a rotational motion sensor configured to generate a rotational motion signal that corresponds to a rotational motion of the housing about an axis, a current sensor configured to generate a motor current signal that corresponds to an amount of current drawn by the motor, and a control circuit that is configured to receive the rotational motion signal and the motor current signal and to control operation of the motor. The control circuit is configured: (a) to determine, based on the current signal, whether a detected kickback condition is likely to be false; (b) to determine, based upon the rotational motion signal, whether an uncontrolled kickback condition has occurred; and (c) to initiate one or more protective operations upon determining that an uncontrolled kickback condition has occurred and is not likely to be false.

Claims

1. A power tool comprising:

a housing;

a motor received in the housing;

an output driven by the motor; and

a control system that includes a rotational motion sensor configured to generate a rotational motion signal that corresponds to a rotational motion of the housing about an axis, a current sensor configured to generate a motor current signal that corresponds to an amount of current drawn by the motor, and a control circuit that is configured to receive the rotational motion signal and the motor current signal and to control operation of the motor,

wherein the control circuit is configured;

(a) to determine, based on the current signal, that a detected kickback condition is likely to be false when the current signal indicates that at least one of the amount of current drawn by the motor and a rate of change of the amount of current drawn by the motor is less than a first threshold value;

(b) to determine, based upon the rotational motion signal, that an uncontrolled kickback condition has occurred when the rotational motion signal indicates that at least one of an angular rotation, an angular velocity, and an angular acceleration of the housing exceeds a second threshold value; and

(c) to initiate one or more protective operations upon determining that an uncontrolled kickback condition has occurred and is not likely to be false.

2. The power tool of claim 1, wherein the one or more protective operations includes one or more of interrupting power to the motor, reducing power to the motor to a non-zero value, pulsing the motor, braking the motor, and actuating a clutch.

3. The power tool of claim 1, wherein the rotational motion sensor comprises one or more of a gyroscope and an accelerometer.

4. The power tool of claim 1, wherein the current sensor comprises a low resistance, high wattage resistor.

5. The power tool of claim 1, wherein the control circuit comprises one or more of a controller, a microcontroller, and a motor control circuit.

6. The power tool of claim 1, further comprising a mode change mechanism configured to select among a hammer only mode, a rotary drive only mode, and a rotary hammering mode, and a mode change sensor configured to generate a mode change signal that corresponds to the selected mode.

7. The power tool of claim 6, wherein the control circuit is configured to prevent initiation of the one or more protective operations when the mode change signal indicates that the hammer only mode has been selected.

8. The power tool of claim 6, wherein the control circuit is configured to determine that the detected uncontrolled kickback condition is likely to be false when the current signal indicates that the amount of current drawn by the motor is less than a current threshold value, and the control circuit is configured to set the current threshold value at a first current threshold value when the mode change signal indicates that the hammer only mode has been selected and at a different second current threshold value when the mode change signal indicates that the hammer only mode has not been selected.

9. A method for initiating a protective response in a power tool having a housing, a motor received in the housing, an output driven by the motor, a current sensor, and a rotational motion sensor, the method comprising:

receiving a current signal from the current sensor that corresponds to an amount of current drawn by the motor;

determining that a detected kickback condition is likely to be false based upon the current signal by determining that at least one of the amount of current drawn by the motor and a rate of change of the amount of current drawn by the motor is less than a first threshold value;

receiving a rotational motion signal from the rotational motion sensor that corresponds to a rotational motion of the housing about an axis;

determining that an uncontrolled kickback condition has occurred based upon the rotational motion signal by determining that at least one of an angular rotation, an angular velocity, and an angular acceleration of the housing exceeds a second threshold value; and

initiating one or more protective operations upon determining that an uncontrolled kickback condition has occurred and is not likely to be false.

10. The method of claim 9, wherein initiating the one or more protective operations comprises one or more of interrupting power to the motor, reducing power to the motor to a non-zero value, pulsing the motor, braking the motor, and actuating a clutch.

11. The method of claim 9, wherein the rotational motion sensor comprises one or more of a gyroscope and an accelerometer.

12. The method of claim 9, wherein the current sensor comprises a low resistance, high wattage resistor.

13. The method of claim 9, wherein the power tool includes a mode change mechanism configured to select among a hammer only mode, a rotary drive only mode, and a rotary hammering mode, and a mode change sensor configured to generate a mode change signal that corresponds to the selected mode, and further comprising preventing the initiating of the one or more protective operations when the mode change signal indicates that the hammer only mode has been selected.

14. The method of claim 9, wherein the power tool includes a mode change mechanism configured to select among a hammer only mode, a rotary drive only mode, and a rotary hammering mode, and a mode change sensor configured to generate a mode change signal that corresponds to the selected mode, and determining that the detected uncontrolled kickback condition is likely to be false comprises determining when the current signal indicates that the amount of current drawn by the motor is less than a current threshold value, and further comprising setting the current threshold value at a first current threshold value when the mode change signal indicates that the hammer only mode has been selected and at a different second current threshold value when the mode change signal indicates that the hammer only mode has not been selected.

15. The method of claim 9, wherein receiving a current signal and determining whether a detected kickback condition is likely to be false are performed before receiving a rotational motion signal, and determining whether an uncontrolled kickback condition has occurred.

16. The method of claim 9, wherein receiving a current signal and determining whether a detected kickback condition is likely to be false are performed after receiving a rotational motion signal, and determining whether an uncontrolled kickback condition has occurred.