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Method for controlling a screwdriver and screwdriver

  • US 10,464,195 B2
  • Filed: 11/08/2013
  • Issued: 11/05/2019
  • Est. Priority Date: 11/09/2012
  • Status: Active Grant
First Claim
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1. A method for controlling a screwdriver having an electric motor, the electric motor having a distinct ratio of rotational speed to torque at a given effective voltage, the method comprising:

  • predefining a constant effective voltage for the operation of the electric motor, said predefined effective voltage associated with an unloaded rotational speed;

    predefining a cutoff rotational speed which corresponds to a predetermined cutoff torque at the predefined effective voltage, the cutoff rotational speed being a minimum speed threshold below which the cutoff torque is exceeded;

    operating the screwdriver under load, wherein operating the screwdriver under load comprises maintaining the predefined effective voltage without controlling the rotational speed of the motor by dynamically adjusting the current;

    during operation of the screwdriver under load, determining a detected rotational speed of the electric motor when the electric motor is operating at the predefined effective voltage, said detected rotational speed being less than the unloaded rotational speed; and

    when the detected rotational speed at the predefined effective voltage is decreased to the cutoff rotational speed by the load, switching off the electric motor.

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