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Capacitively coupled machine tool safety having a self-test network

  • US 4,518,958 A
  • Filed: 02/02/1982
  • Issued: 05/21/1985
  • Est. Priority Date: 02/02/1982
  • Status: Expired due to Fees
First Claim
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1. A machine tool safety system comprising:

  • an electric field generator adapted to be carried on a portion of the person of a machine tool operator for generating an electric field;

    a capacitive receptor antenna mountable in a predetermined location with respect to a machine tool and cooperable with the electric field generator to form a capacitively coupled transmission arrangement operative to induce, by the action of the electric field through the capacitive coupling, a monotonically increasing electrical signal the magnitude of which is functionally related to the distance between the electric field generator and the capacitive receptor antenna;

    a signal processor connected to the capacitive receptor antenna and responsive to the signal induced in the capacitive receptor antenna by the electric field to generate an indication when the magnitude of the induced electrical signal exceeds a predetermined threshold, the indication being able to be used to permit safe operation of a machine tool;

    a self-test radiating antenna disposed in proximity to the capacitive receptor antenna; and

    a self-test network electrically connected to the self-test radiating antenna for generating an excitation signal operative to induce in the capacitive receptor antenna a test signal having a magnitude greater than the threshold.

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