Power tool anti-kickback system with rotational rate sensor
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Abstract
A control system is provided for use in a power tool. The control system includes: a rotational rate sensor having a resonating mass and a controller electrically connected to the rotational rate sensor. The rotational rate sensor detects lateral displacement of the resonating mass and generates a signal indicative of the detected lateral displacement, such that the lateral displacement is directly proportional to a rotational speed at which the power tool rotates about an axis of the rotary shaft. Based on the generated signal, the controller initiates a protective operation to avoid further undesirable rotation of the power tool. The controller may opt to reduce the torque applied to shaft to a non-zero value that enables the operator to regain control of the tool.
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Citations
47 Claims
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1-31. -31. (canceled)
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32. A method for initiating a protective response in a power tool having a rotary shaft, comprising:
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monitoring rotational motion of the power tool about a longitudinal axis of the rotary shaft using a rotational motion sensor disposed in the power tool;
computing angular displacement of the power tool about the axis of the rotary shaft based on input from the rotational motion sensor;
initiating a protective operation when a trigger condition is met and angular displacement of the power tool falls within a range of angular displacements; and
initiating a protective operation when the trigger condition is not met but angular displacement of the power tool exceeds the range of angular displacements. - View Dependent Claims (33, 34, 35, 36, 37, 38, 39)
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40. A method for initiating a protective response in a power tool having a motor drivably coupled to a rotary shaft to impart rotary motion thereto, comprising:
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monitoring rotational motion of the power tool about a longitudinal axis of the rotary shaft using a rotational motion sensor disposed in the power tool;
determining angular displacement of the power tool about the axis of the rotary shaft from a baseline based on input from the rotational motion sensor;
initiating a protective operation in the power tool when a first trigger condition is met and angular displacement of the power tool falls within a first range of angular displacements; and
initiating a protective operation in the power tool when a second trigger condition is met and angular displacement of the power tool falls within a second range of angular displacements, where the second trigger condition is different than the first trigger condition and the second range of angular displacements is different than the first range of angular displacements. - View Dependent Claims (41, 42, 43, 44, 45, 46)
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47. A method for initiating a protective response in a power tool having a motor drivably coupled to a rotary shaft to impart rotary motion thereto, comprising:
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arranging a rotational motion sensor at a location in the power tool spatially separated from the rotary shaft, where the rotational motion sensor measures rotational velocity based on Coriolis acceleration;
determining angular displacement of the power tool about the axis of the rotary shaft from a baseline based on input from the rotational motion sensor;
initiating a protective operation in the power tool when the rotational velocity of the power tool determined by the rotational motion sensor exceeds a velocity threshold and angular displacement of the power tool falls within at range of angular displacements; and
initiating the protective operation in the power tool when the angular displacement of the power tool exceeds the range of angular displacements.
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Specification