Adapter for drilling strings with controllable air passage

Adaptor for drilling strings with controllable air passage

Apparatus for actuating downhole flow control valves

Ball actuable circulating dump valve

Ball operated by-pass tool for use in drillstring

Blowout preventer

Check valve for rock drill

Combination fluid nozzle and backflow valve

Dart-operated big bore by-pass valve

Device and procedure for the insertion of a new drilling...

Device for reversing the direction of flow of a fluid at the lev

Downhole valve for oil/gas well

Downhole valve for use when drilling an oil or gas well

Drill bit having springless check valve and method of blocking b

Drill pipe

Erosion resistant downhole mud diverter tool

Flow control valve for rock bits

Method and apparatus for cementing drill strings in place for on

Method and apparatus for cementing drill strings in place...

Methods and apparatus for cementing drill strings in place...