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US 5,493,747 AGranted
Electric toothbrush
AssigneeMatsushita Electric Works, Ltd.
InventorsSatoru Inakagata, Yoji Kawamoto
Life of this patent
Estimating the term…
Abstract
An electric toothbrush with a control circuit capable of stopping the brushing operation when the brush is pressed against an user's teeth with an excessive force. The electric toothbrush comprises a housing which carries a shaft mounting a brush. The housing incorporates a rotary electric motor and a motion conversion mechanism which converts a rotational movement of the motor to a reciprocatory movement of the shaft for reciprocating said brush. A pressure sensor is provided to sense a brush pressure being applied back to the brush as a counter-action when pressing the brush against the user's teeth and to produce a stop signal when the sensed brush pressure exceeds a predetermined limit level.
Claims23
An electric toothbrush comprising:
- a housing having a shaft mounting a brush, said housing incorporating a rotary electric motor and a motion converting mechanism which converts a rotational movement of said motor to a reciprocatory movement of said shaft for reciprocating said brush;
- a pressure sensor which senses a brush pressure being applied back to said brush as a counter-pressure when pressing said brush against teeth of a user, and which provides a stop signal when said brush pressure exceeds a predetermined limit level;
- a selector to select a limit level from a plurality of set values;
- and
- a control circuit which is responsive to said stop signal for lowering the motor speed or stopping said motor.
2 more elements
An electric toothbrush comprising:
- a housing having a shaft mounting a brush, said housing incorporating a rotary electric motor and a motion converting mechanism which converts a rotational movement of said motor to a reciprocatory movement of said shaft for reciprocating said brush;
- a pressure sensor which senses a brush pressure being applied back to said brush as a counter-pressure when pressing said brush against teeth of a user, and which provides a stop signal when said brush pressure exceeds a predetermined limit level;
- and
- a control circuit which is responsive to said stop signal for lowering the motor speed or stopping said motor, said control circuit including a constant speed means for rotating said motor at a constant level irrespective of variations in said brush pressure so long as said brush pressure is below said limit level and a speed selector for selecting the constant speed rotation speed of said motor.
1 more element
An electric toothbrush comprising:
- a housing having a shaft mounting a brush, said housing incorporating a rotary electric motor and a motion converting mechanism which converts a rotational movement of said motor to a reciprocatory movement of said shaft for reciprocating said brush;
- a pressure sensor which senses a brush pressure being applied back to said brush as a counter-pressure when pressing said brush against teeth of a user, and which provides a stop signal when said brush pressure exceeds a predetermined limit level;
- and
- a control circuit which is responsive to said stop signal for lowering the motor speed or stopping said motor, said control circuit including constant speed means for rotating said motor at a constant level irrespective of variations in said brush pressure so long as said brush pressure is below said limit level, said control circuit providing a first limit mode and a second limit mode selectively, said first limit mode enabling said motor to rotate at a first constant rotation speed irrespective of said brush pressure so long as said brush pressure is below a first limit level, said second limit mode enabling said motor to rotate at a second constant rotation speed irrespective of said brush pressure so long as said brush pressure is below a second limit level, said first rotation speed and said first limit level being respectively lower than said second rotation speed and said second limit level.
1 more element
An electric toothbrush comprising:
- a housing having a shaft mounting a brush, said housing incorporating a rotary electric motor and a motion converting mechanism which converts a rotational movement of said motor to a reciprocatory movement of said shaft for reciprocating said brush;
- a pressure sensor which senses a brush pressure being applied back to said brush as a counter-pressure when pressing said brush against teeth of a user, and which provides a stop signal when said brush pressure exceeds a predetermined limit level;
- and
- a control circuit which is responsive to said stop signal for lowering the motor speed or stopping said motor, said control circuit including proportional means for increasing the rotational speed of said motor in proportion to an increase in said brush pressure so long as said brush pressure is below said limit level.
1 more element
An electric toothbrush comprising:
- a housing having a shaft mounting a brush, said housing incorporating a rotary electric motor and a motion converting mechanism which converts a rotational movement of said motor to a reciprocatory movement of said shaft for reciprocating said brush;
- a pressure sensor which senses a brush pressure being applied back to said brush as a counter-pressure when pressing said brush against teeth of a user, and which provides a stop signal when said brush pressure exceeds a predetermined limit level;
- said pressure sensor comprising means which monitors a waveform of a motor current flowing through said motor and analyzes said waveform for deriving said brush pressure, said monitor means producing said stop signal when said brush pressure exceeds said limit level;
- and
- a control circuit which is responsive to said stop signal for lowering the motor speed or stopping said motor.
2 more elements
An electric toothbrush comprising:
- a housing having a shaft mounting a brush, said housing incorporating a rotary electric motor and a motion converting mechanism which converts a rotational movement of said motor to a reciprocatory movement of said shaft for reciprocating said brush;
- a pressure sensor connected to said shaft and which senses a brush pressure being applied back to said brush as a counter-pressure when pressing said brush against teeth of a user, and which provides an electric resistance which varies in proportion to said brush pressure applied back to said shaft and produces a stop signal when the electric resistance increases to a level corresponding to a predetermined limit level;
- and
- a control circuit which is responsive to said stop signal for lowering the motor speed or stopping said motor, said control circuit including calibration means which obtains an initial current level measured when said motor rotates under substantially no load condition, and said calibration means defining said limit level as said initial current level plus a predetermined set level.
1 more element
Dependencies are inferred from the claim text.