Power Tool with Ultrasonic Sensor for Sensing Contact between an Implement and an Object

• US 20160319989A1
• Filed: 12/12/2014
• Published: 11/03/2016
• Est. Priority Date: 12/24/2013
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH, Robert Bosch Tool Corporation (Robert Bosch GmbH)
• Original Assignee: Robert Bosch GmbH
• Inventors: Ramaswamy, Bharadwaja Maharshi, Manevarthe Srikantiah, Vishwanatha, Krishnarao, Niranjan Sathyanarayanarao
• Granted Patent: US 10,330,258 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B23D 59/002 for the position of the saw blade B27B5/36 and B27B9/02 take precedence
• CPC Class Codes: B27G 19/02 for circular saws
• CPC Class Codes: F16P 3/141 using sound propagation, e.g. sonar

Abstract

A power tool (200) includes a moving implement (222) and an ultrasonic transducer (226) that emits ultrasonic signals and receives echo return signals from an object (224, 229) that reflects the ultrasonic signals. A controller (240) identifies a distance between the implement and the object and identifies a type of the object based on the echo return signals from the object. The controller activates an implement arrest mechanism (236) in response to the distance between the object and the ultrasonic transducer being less than a predetermined threshold and the type of the object corresponding to a portion of a human body.

Claims

1. A power tool comprising:

an implement located in a predetermined location in the power tool;

an actuator configured to move the implement in a predetermined motion during operation of the power tool;

an implement arrest mechanism operatively connected to the implement;

an ultrasonic emitter and an ultrasonic receiver, the ultrasonic emitter being configured to emit an ultrasonic signal and the ultrasonic receiver being configured to receive an echo return signal from an object that reflects the ultrasonic signal; and

a controller operatively connected to the actuator, the ultrasonic emitter, the ultrasonic receiver, and the implement arrest mechanism, the controller being configured to;

operate the actuator to move the implement;

identify a distance between the implement and an object that is proximate to the implement with reference to data corresponding to an ultrasonic signal emitted from the ultrasonic emitter and an echo return signal received by the ultrasonic receiver;

identify a type of the object with reference to an amplitude of the echo return signal; and

activate the implement arrest mechanism to stop movement of the implement or move the implement from the predetermined location to prevent contact between the object and the implement while the implement is in motion in response to the identified distance being less than a predetermined threshold and the identified type of the object corresponding to a portion of a human body.

2. The power tool of claim 1 wherein the implement is a saw blade.

3. The power tool of claim 2, the implement arrest mechanism being configured to retract the saw blade below a level of a table in the power tool.

4. The power tool of claim 2, the implement arrest mechanism being configured to stop motion of the saw blade.

5. The power tool of claim 1, the controller being further configured to:

identify the distance between the implement and the object with reference to a time delay between emission of the ultrasonic signal and reception of the echo return signal.

6. The power tool of claim 1, the controller being further configured to:

identify an absorption coefficient as a ratio of an amplitude of the ultrasonic signal that reaches a surface of the object to the amplitude of the echo return signal that reflects from the surface of the object with reference to a first predetermined amplitude of the emitted ultrasonic signal, a second amplitude of the echo return signal, and the identified distance between the ultrasonic emitter and the object.

7. The power tool of claim 6, the controller being further configured to:

identify the type of the object as the portion of the body of the human in response to the absorption coefficient being above a first predetermined threshold.

8. The power tool of claim 7, the controller being further configured to:

identify the type of the object as a work piece in response to the absorption coefficient being below the first predetermined threshold.

9. The power tool of claim 1, the controller being further configured to:

continue operation of the actuator to enable the implement to remain in motion in response to the identified type of the object corresponding to a work piece.

10. The power tool of claim 1, the ultrasonic emitter and ultrasonic receiver being incorporated into an ultrasonic transducer.

11. The power tool of claim 1, the controller being further configured to:

identify a velocity of the object with reference to a plurality of echo return signals that are reflected from a surface of the object in response to a plurality of ultrasonic signals emitted from the ultrasonic emitter; and

activate the implement arrest mechanism to stop movement of the implement or move the implement from the predetermined location to prevent contact between the object and the implement while the implement is in motion in response to the identified velocity exceeding a predetermined threshold and the identified type of the object corresponding to a portion of a human body.

12. A method of operating a power tool comprising:

operating an actuator to move an implement;

operating with a controller an ultrasonic emitter to emit an ultrasonic signal;

receiving with an ultrasonic receiver an echo return signal from an object corresponding to the ultrasonic signal emitted from the ultrasonic emitter;

identifying with the controller a distance between the implement and an object that is proximate to the implement with reference to the emitted ultrasonic signals and the received echo return signals;

identifying with the controller a type of the object with reference to an amplitude of the echo return signal; and

activating with the controller an implement arrest mechanism to stop movement of the implement or move the implement from the predetermined location to prevent contact between the object and the implement while the implement is in motion in response to the identified distance between the object and the transducer being less than a predetermined threshold and the identified type of the object corresponding to a portion of a human body.

13. The method of claim 12, the identification of the distance further comprising:

identifying with the controller the distance between the implement and the object with reference to a time delay between emission of the ultrasonic signal and reception of the echo return signal.

14. The method of claim 12 further comprising:

identifying with the controller an absorption coefficient as a ratio of an amplitude of the ultrasonic signal that reaches a surface of the object to the amplitude of the echo return signal that reflects from the surface of the object with reference to a first predetermined amplitude of the emitted ultrasonic signal, a second amplitude of the echo return signal, and the identified distance between the ultrasonic emitter and the object.

15. The method of claim 14, the identification of the type of the object further comprising:

identifying with the controller the type of the object as the portion of the body of the human in response to the absorption coefficient being above a first predetermined threshold.

16. The method of claim 15, the identification of the type of the object further comprising:

identifying with the controller the type of the object as a work piece in response to the absorption coefficient being below the first predetermined threshold.

17. The method of claim 12 further comprising:

continuing operation of the actuator to enable the implement to remain in motion in response to the identified type of the object corresponding to a work piece.

18. The method of claim 12 further comprising:

Identifying with the controller a velocity of the object with reference to a plurality of echo return signals that are reflected from a surface of the object in response to a plurality of ultrasonic signals emitted from the ultrasonic emitter; and

activating with the controller the implement arrest mechanism to stop movement of the implement or move the implement from the predetermined location to prevent contact between the object and the implement while the implement is in motion in response to the identified velocity exceeding a predetermined threshold and the identified type of the object corresponding to a portion of a human body.