Method for detecting a bit jam condition using a freely rotatable inertial mass
First Claim
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1. A method for detecting a bit jam condition in a power tool having a tool drivably connected to a motor to impart rotary motion about a rotational axis to the tool, comprising:
- disposing an inertial mass comprised of a solid cylindrical body in a housing of the power tool, the inertial mass being freely rotatable about its longitudinal axis and axially aligned with the rotational axis of the tool;
monitoring rotational motion of the housing of the power tool in relation to the inertial mass; and
determining when angular velocity of the rotational motion exceeds a predefined velocity threshold indicative of a bit jam condition.
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Abstract
An improved method is provided for controlling a power tool having a rotary shaft. The method includes: disposing an inertial mass in a housing of the power tool, such that the inertial mass is freely rotatable about an axis of rotation which is axially aligned with the rotary shaft; monitoring rotational motion of the power tool in relation to the inertial mass during operation of the power tool; and activating a protective operation based on the rotational motion of the power tool in relation to the inertial mass.
74 Citations
20 Claims
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1. A method for detecting a bit jam condition in a power tool having a tool drivably connected to a motor to impart rotary motion about a rotational axis to the tool, comprising:
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disposing an inertial mass comprised of a solid cylindrical body in a housing of the power tool, the inertial mass being freely rotatable about its longitudinal axis and axially aligned with the rotational axis of the tool; monitoring rotational motion of the housing of the power tool in relation to the inertial mass; and determining when angular velocity of the rotational motion exceeds a predefined velocity threshold indicative of a bit jam condition. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method for detecting a bit jam condition in a power tool having rotary shaft configured to hold a tool bit, comprising:
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disposing an inertial mass comprised of a solid cylindrical body in a housing of the power tool, the inertial mass being freely rotatable about an axis of rotation during operation of the tool and the axis of rotation being axially aligned with a rotational axis of the tool bit; monitoring rotational motion of the housing of the power tool in relation to the inertial mass; computing angular velocity of the housing in relation to the inertial mass; determining a direction of the angular velocity of the housing in relation to the inertial mass; and activating a protective operation when the angular velocity exceeds a predefined velocity threshold and the direction of the angular velocity does not change within a predefined period of time. - View Dependent Claims (14, 15, 16, 17, 18, 19)
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20. A method for detecting a bit jam condition in a power tool having a rotary shaft configured to hold a tool bit, comprising:
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disposing an inertial mass in a housing of the power tool, the inertial mass being freely rotatable about an axis of rotation and the axis of rotation being axially aligned with the rotary shaft; setting the predefined displacement threshold at a first value for low motor speeds and at a second value for high motor speeds, where the first value is higher than the second value; arranging a sensing element in fixed relation to the housing to detect rotational motion of the housing in relation to the inertial mass; determining rotational displacement of the housing in relation to the inertial mass based on input from the sensing element; and activating a protective operation when the rotational displacement of the housing exceeds a predefined displacement threshold.
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Specification