Classifications

• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B17/00—Drilling rods or pipes; Flexible drill strings; Kellies; Drill collars; Sucker rods; Cables; Casings; Tubings
  • E21B17/02—Couplings; joints
  • E21B17/04—Couplings; joints between rod or the like and bit or between rod and rod or the like
  • E21B17/042—Threaded
  • E21B17/0426—Threaded with a threaded cylindrical portion, e.g. for percussion rods

Definitions

• the present invention relates to a thread coupling for percussive drilling including at least one male thread and one female thread, said male thread being arranged upon a spigot and said female thread being arranged within a sleeve, said male and female threads being cylindrical, an external shoulder stop at a free end of the sleeve, said shoulder stop including contact surfaces being perpendicular to a longitudinal centre axis of the thread coupling, the spigot at a free end having an end surface that is perpendicular to said longitudinal centre axis, the sleeve being provided with an internal stop surface that is perpendicular to said longitudinal centre axis, in an unused thread coupling there is an initial play between the end surface of the spigot and the internal stop surface, said initial play being eliminated after wearing-in of the thread coupling.
• a thread coupling of the type defined above is previously known from SE-B-469 603 (US-A-4.968,068) , said document being incorporated by reference into the present application.
• a problem with such a thread coupling, especially when trapezoidal threads are used, is that the coupling during use becomes so tightened that it is difficult to unscrew the coupling when one member of the coupling needs to be exchanged.
• the present invention has the aim to present a thread coupling of the type mentioned above, said thread coupling being less tightened than prior art thread couplings of the type defined above.
• Fig.l shows a schematic, partly sectioned view of a thread coupling according to the invention
• Fig.2 shows a view similar to Fig.l of an alternative embodiment of the invention
• Fig.3 shows a view similar to Fig.l of a further alternative embodiment of the invention.
• the thread coupling of Fig.l includes a male thread 10 that is provided on a spigot 11 which constitutes an integral part of a male extension member 12 for percussive drilling.
• a male extension member 12 is provided with a shoulder 13 that has a first plane contact surface 14 directed towards the free end of the spigot 11.
• the first contact surface 14 has an extension perpendicular to a longitudinal centre axis 15 of the male extension member 12.
• the free end of the spigot 11 has the shape of a plane end surface 16 that has an extension perpendicular to the centre axis 15.
• the thread coupling also includes a female thread 17 that is provided in a sleeve 18 which constitutes an integral part of a female extension member 19.
• a second plane contact surface 20 is provided, said second contact surface 20 having an extension perpepdicular to the longitudinal centre axis 15 of the female extension member 19, said longitudinal centre axis coinciding with the centre axis of the male extension member 12.
• the female extension member 19 has a plane bottom surface 21 that has an extension perpendicular to the longitudinal centre axis 15. From Fig.l it is evident that in the thread coupling according to the present invention the first contact surface 14 of the male extension member 12 always contacts the second contact surface 20 of the sleeve 18, i.e. so called shoulder stop is established.
• the thread coupling according to the present invention is between a drill rod and a drill bit it is favourable that the drill bit constitutes the male extension member 12 while the drill rod constitutes the female extension member 19.
• the region of the clearance 22 of the male thread 10 is the weakest portion of the thread coupling according to the present invention, i.e. if the coupling collapses it is likely that the fracture will occur in the region of the clearance 22. Since a drill bit is worn out up to ten times faster than a drill rod it is favourable that the fracture is located in the drill bit.
• the male thread 11 has a pitch angle .
• the female thread 17 has the same pitch angle .
• the pitch angle o. is greater that 8.5° and less than 15° (8.5° ⁇ ⁇ ⁇ 15°) .
• the pitch angle a should be greater than 9.5° and less than 11.5° (9.5° ⁇ ⁇ ⁇ 11.5°) .
• the shock wave is transmitted simultaneously through both the spigot 11 and the sleeve 18. This means that there is very small relative motions in the axial direction between the male thread 10 of the spigot 11 and the female thread 17 of the sleeve 18.
• the thread coupling according to the present invention will operate properly at a lower tightening level than thread couplings without shoulder-bottom stop. Said lower tightening level is achieved by an increase of the pitch angle a .
• both the male threads 10', 10" and the female threads 17', 17" have the same pitch angle ⁇ .
• the embodiment according to Fig.3 includes a male thread 10' ''that is provided on a separate spigot 11'''.
• the male thread 10''' is interrupted in the intermediate region of the longitudinal direction of the spigot 11' ' ' .
• the male thread has a continous extension along the entire length of the spigot 11'''. Since the spigot 11''' is a separate element there are two end surfaces 16''' and 16''' respectively.
• the spigot 11''' is received in two sleeves 18''' and 18''' respectively, said sleeves 18'''', 18'''' being integral with drill tubes 19''' and 19''' respectively.
• the female threads 17' ' ' and 17' ' ' ' are located inside the sleeves 18' '' and 18' '' ' respectively.
• Both the male thread 10'' ' and the female threads 17' ' ' and 17' ' ' ' ' have a pitch angle a .
• Fig.3 functions according to the principles of the present invention. First there is shoulder stop established between the contact surfaces 20' ' ' and 20' ' ' ' . Then there are two bottom stops established when after wearing in of the thread coupling the plays ⁇ at both ends of the spigot 11' ' ' are eliminated.
• the invention is in no way restricted to the embodiments described above.
• the principles of the invention can be used both for drill rods and drill tubes for percussive drilling and also in a thread coupling between a shank adapter and the first drill rod.
• the threads of a thread coupling according to the present invention preferably have one entry but it is also possible with two entries.
• the embodiments and examples should not be considered given in a restricting manner but only for examplifying purposes.
• the present invention primarily relates to trapezoidal threads, the present invention is not limited to such type of threads. Also in other respects the invention can be varied freely within the scope of the appending claims.

Landscapes

• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Geology (AREA)
• Mining & Mineral Resources (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Environmental & Geological Engineering (AREA)
• Fluid Mechanics (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Earth Drilling (AREA)
• Prostheses (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 1994
  • 1994-07-19 SE SE9402517A patent/SE505073C2/sv not_active IP Right Cessation
• 1995
  • 1995-07-13 WO PCT/SE1995/000852 patent/WO1996002729A1/en not_active Application Discontinuation
  • 1995-07-13 CA CA 2192204 patent/CA2192204A1/en not_active Abandoned
  • 1995-07-13 AU AU30893/95A patent/AU684380B2/en not_active Ceased
  • 1995-07-13 BR BR9508260A patent/BR9508260A/pt not_active Application Discontinuation
  • 1995-07-13 EP EP95926562A patent/EP0771388A1/en not_active Withdrawn
  • 1995-07-13 JP JP8504950A patent/JPH10504077A/ja active Pending
• 1997
  • 1997-01-16 FI FI970181A patent/FI970181A0/fi not_active Application Discontinuation

Non-Patent Citations (1)

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