Patents by Inventor John U. Dewar

John U. Dewar 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).

  • Compensating ring for a down hole hammer
    Patent number: 5085285
    Abstract: The present invention relates to a sacrificial compensating ring for a down hole hammer having an outer sleeve, a drive sub and a drill bit, wherein the sacrificial compensating ring has an outer diameter greater than that of the outer sleeve and substantially the same as that of the drill bit and the sacrificial compensating ring being located between the outer sleeve and the drive sub.
    Type: Grant
    Filed: July 17, 1990
    Date of Patent: February 4, 1992
    Assignee: D.T.A. Pty. Ltd.
    Inventors: John Elsby, John U. Dewar, Andrew Greathead, Brian T. Sanfead