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Lawn mower

  • US 8,833,045 B2
  • Filed: 12/02/2011
  • Issued: 09/16/2014
  • Est. Priority Date: 12/06/2010
  • Status: Expired due to Fees
First Claim
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1. A lawn mower comprising:

  • an electric motor;

    a driving assembly coupled to and driven by said electric motor;

    a blade assembly coupled to and driven rotatably by said driving assembly;

    a battery for providing electricity to said motor;

    a switch unit electrically connected to said electric motor and said battery and operable between an open circuit state, in which electrical connection between said electric motor and said battery is broken, and a closed circuit state, in which electrical connection between said electric motor and said battery is made; and

    a detecting unit including a sampling resistor electrically connected in series with said battery, and a trigger circuit electrically connected in parallel with said sampling resistor and configured to control said switch unit according to detected voltage across said sampling resistor;

    wherein said switch unit includes;

    a stationary magnet;

    a movable magnet movable toward and away from said stationary magnet;

    a biasing member disposed between said stationary magnet and said movable magnet and providing a biasing force to bias said movable magnet away from said stationary magnet;

    a coil electrically connected to said trigger circuit and capable of creating a magnetic field to move said movable magnet relative to said stationary magnet upon receipt of electrical current from said trigger circuit;

    an electrically conductive first contact member electrically connected to one of said sampling resistor and said electric motor; and

    an electrically conductive second contact member electrically connected to the other one of said sampling resistor and said electric motor;

    wherein one of said first and second contact members is configured to be moved by said movable magnet to make or break electrical contact with the other one of said first and second contact members.

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