Method for detecting a bit jam condition using a freely rotatable inertial mass
AssigneeBlack & Decker Inc.
InventorsDavid A Carrier, Daniel Puzio, Robert Bradus
Life of this patent
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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.
Claims20
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.
A method for detecting a bit jam condition in a power tool having rotary shaft configured to hold a tool bit, 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 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.
A method for detecting a bit jam condition in a power tool having a rotary shaft configured to hold a tool bit, comprising:
- 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.
Dependencies are inferred from the claim text.