Power Tool with Force Sensing Electronic Clutch

• US 20130105189A1
• Filed: 10/18/2012
• Published: 05/02/2013
• Est. Priority Date: 10/26/2011
• Status: Active Grant

• Current Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Original Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Inventors: Gottesman, Tal, Puzio, Daniel, Murthy, Sankarshan, Howson, John, Eshleman, Scott J., Hester, Russell David, Schell, Craig Alan, Schwartz, Daniel L.
• Granted Patent: US 9,352,456 B2
• Time in Patent Office: Days
• US Class Current: 173/178
• 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 23/14 Arrangement of torque limiters or torque indicators in wrenches or screwdrivers couplings for transmitting rotation or clutches F16D; devices for measuring torque per se G01L
• CPC Class Codes: B25B 23/147 specially adapted for electrically operated wrenches or screwdrivers
• CPC Class Codes: G01L 5/0042 applying a torque
• CPC Class Codes: G01L 5/0061 Force sensors associated with industrial machines or actuators for the specific machine or actuator involved see relevant class, e.g. F01, F04, F16, B66, E21

Abstract

A power tool includes a housing, a motor disposed in the housing, a transmission disposed in the housing and coupled to the motor, an output end effector coupled to the transmission, a control circuit for controlling power delivery from a power source to the motor, and a force sensing electronic clutch including a force sensor coupled to a substantially stationary element of the transmission. The force sensor senses a reaction torque transmitted from the end effector to at least a portion of the transmission. The sensor is configured to generate a first electronic signal corresponding to an amount of the reaction torque. The control circuit compares the first electronic signal with a second electronic signal corresponding to a desired threshold torque value, and initiates a protective operation when a value of the first electronic signal indicates that the reaction torque has exceeded the desired threshold torque value.

Claims

1. A power tool comprising:

a housing;

a motor disposed in the housing;

a transmission disposed in the housing and coupled to the motor;

an output end effector coupled to the transmission;

a control circuit for controlling power delivery from a power source to the motor; and

a force sensing electronic clutch including a force sensor coupled to a substantially stationary element of the transmission to sense a reaction torque transmitted from the end effector to at least a portion of the transmission,

wherein the sensor is configured to generate a first electronic signal corresponding to an amount of the reaction torque, and

wherein the control circuit compares the first electronic signal with a second electronic signal corresponding to a desired threshold torque value, and initiates a protective operation when a value of the first electronic signal indicates that the reaction torque has exceeded the desired threshold torque value.

2. The power tool of claim 1, wherein the sensor comprises a thin film force sensing resistor.

3. The power tool of claim 1, wherein the transmission comprises a planetary gear set having a sun gear, at least one planet gear, a ring gear, and a planet gear carrier, and wherein the force sensor is coupled to a substantially stationary gear of the planetary gear set.

4. The power tool of claim 3, wherein the force sensor is coupled to the ring gear.

5. The power tool of claim 4, wherein the force sensor is supported in a base of a cavity in the housing, and the ring gear includes a radial lug that transmits torque to the force sensor.

6. The power tool of claim 1, further comprising a clutch setting switch that enables a user to adjust the desired threshold torque value.

7. The power tool of claim 6, further comprising a position sensor that senses the position of the clutch setting switch.

8. The power tool of claim 1, wherein the protective operation comprises one or more of interrupting or reducing power to the motor, actively braking the motor, and actuating a mechanical clutch.

9. The power tool of claim 1, wherein the sensor comprises a first layer having a conductive pattern on a non-conductive substrate, a second layer having a conductive pattern on a non-conductive substrate, and a third layer between the first layer and the second layer, the third layer having a resistive or semi-conductive pattern on a non-nonconductive substrate.

10. The power tool of claim 9, wherein the resistive or conductive pattern is printed with an material containing graphene.

11. The power tool of claim 1, further comprising a current sensing electronic clutch that includes a current sensor that generates a current signal that corresponds to an amount current delivered to the motor, and that causes the controller to initiate a protective operation when a value from the current sensor exceeds a current threshold value that corresponds to the desired threshold torque value.

12. The power tool of claim 11, wherein the force sensing electronic clutch is activated and the current sensing electronic clutch is deactivated when the motor is driving the end effector in a clockwise direction, and the force sensing electronic clutch is deactivated and the current sensing electronic clutch is activated when the motor is driving the end effector in a counter-clockwise direction.

13. The power tool of claim 11, wherein the control circuit uses the current signal to automatically re-calibrate the first electronic signal from the force sensor, during a period when the control circuit determines that the current signal by itself is a good indicator of output torque.

14. The power tool of claim 13, wherein the control circuit re-calibrates the first electronic signal by determining a compensation factor to add to or subtract from the first electronic signal based on the current signal.

15. A power tool comprising:

a housing;

a motor disposed in the housing;

a transmission disposed in the housing and coupled to the motor;

an output end effector coupled to the transmission;

a control circuit for controlling power delivery from a power source to the motor; and

a force sensing electronic clutch including a force sensor that senses a reaction torque transmitted from the end effector to at least a portion of the transmission and causes the control circuit to initiate a first protective operation when the sensed reaction torque exceeds a first threshold torque value;

a current sensing electronic clutch including a current sensor that senses an amount current delivered to the motor, and a controller that causes the controller to initiate a second protective operation when a value from the current sensor exceeds a current threshold value that corresponds to a second threshold torque value.

16. The power tool of claim 15, wherein the force sensing electronic clutch is activated and the current sensing electronic clutch is deactivated when the motor is driving the end effector in a clockwise direction, and the force sensing electronic clutch is deactivated and the current sensing electronic clutch is activated when the motor is driving the end effector in a counter-clockwise direction.

17. The power tool of one claim 15, wherein each of the first protective operation and the second protective operation comprises one or more of interrupting or reducing power to the motor, actively braking the motor, and actuating a mechanical clutch.

18. A force sensing electronic clutch for use with a power tool having a motor, a transmission coupled to the motor, and an end effector coupled to the transmission, the force sensing electronic clutch comprising:

a control circuit for controlling power delivery from a power source to the motor; and

a force sensor coupled to a substantially stationary element of the transmission to sense a reaction torque transmitted from the end effector to at least a portion of the transmission, wherein the sensor is configured to generate a first electronic signal corresponding to an amount of the reaction torque, and

wherein the control circuit compares the first electronic signal with a second electronic signal corresponding to a desired threshold torque value, and initiates a protective operation when a value of the first electronic signal indicates that the reaction torque has exceeded the desired threshold torque value.

19. The force sensing electronic clutch of claim 18, wherein the protective operation comprises one or more of interrupting or reducing power to the motor, actively braking the motor, and actuating a mechanical clutch.

20. The force sensing electronic clutch of claim 18, wherein the transmission comprises a planetary gear set having a sun gear, at least one planet gear, a ring gear, and a planet gear carrier, and wherein the force sensor is coupled to a substantially stationary gear of the planetary gear set.