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Power-driven screwdriver with a torque control

  • US 4,418,765 A
  • Filed: 01/12/1982
  • Issued: 12/06/1983
  • Est. Priority Date: 01/16/1981
  • Status: Expired due to Term
First Claim
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1. A power-driven screwdriver comprising:

  • a base;

    a motor mounted on said base;

    a screwdriver bit mounted on said base and rotatably drivable by said motor to tighten a screw with a tightening torque;

    a torque detector mounted on said base for producing a signal representative of said tightening torque;

    a torque setting device for generating a signal indicative of a desired tightening torque with which the screw is to be tightened;

    a comparator for generating a comparator output signal when said torque representative signal is within a range defined by the signal from said torque setting device;

    a switch responsive to said comparator output signal for de-energizing said motor; and

    a time-delay circuit interposed between said comparator and said switch for introducing a delay time to said comparator output signal applied to said switch.

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