Patents Assigned to D.T.A. Pty. Ltd.
  • Transmission sleeve for a down hole hammer
    Patent number: 5154244
    Abstract: The present invention relates to a sacrificial transmission sleeve for a reverse circulation down hole hammer of the percussive type actuated by a fluid under pressure, including an outer sleeve, a drill bit retained in retaining means, the transmission sleeve comprising a body and an annular flange extending from the body towards the drill bit, wherein the transmission sleeve has an outer diameter greater than that of the outer sleeve and substantially the same as the drill bit.
    Type: Grant
    Filed: April 26, 1991
    Date of Patent: October 13, 1992
    Assignee: D.T.A. PTY Ltd
    Inventors: John Elsby, Brian T. Sanfead, Andrew Greathead
  • 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