Patents by Inventor John Henry Calvert

John Henry Calvert has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Eddy current metal surface flaw detector
    Patent number: 3931571
    Abstract: A flaw detecting device responding to variations in eddy currents induced in a surface under test includes an oscillatory circuit comprising a tuned detector circuit including a detector coil. The detector circuit is in series with an inductor and preferably capacitors are in parallel with the detector coil and with the detector coil and inductor respectively. The oscillatory circuit includes also a two stage amplifier with zero phase shift and a capacitor between the output of the amplifier and earth. The oscillatory circuit operates to successively decrease its output amplitude when the detector is moved from free air to adjacent a flawless surface and then adjacent a flaw in the surface.
    Type: Grant
    Filed: June 14, 1974
    Date of Patent: January 6, 1976
    Assignee: Hocking Associates (Electronics) Limited
    Inventors: Donald Henry Hocking, John Henry Calvert, Richard Dennis