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
  • E21B4/00—Drives for drilling, used in the borehole
  • E21B4/06—Down-hole impacting means, e.g. hammers
  • E21B4/14—Fluid operated hammers

Definitions

• This invention relates to an in-hole rock drilling machine comprising a tubular housing with a guide bushing in its front end arranged to guide the front end of a piston hammer and a valve housing in the rear end of the machine housing arranged to guide the rear end of the piston hammer.
• Figures 1 and 2 are together a side view of an in-hole rock drilling machine in accordance with the invention; Figure 1 shows the rear part of the machine and Figure 2 shows the front part. An intermediate part of the machine is not shown.
• the in-hole rock drilling machine shown in the Figures has a housing, the main part of which is a cylindrical tube 12 that has an interior shoulder 13 and interior threads in each end,
• a drill bit 14 is maintained in the housing by means of a sleeve 15 screwed into the tube 12.
• the sleeve 15 is in splined connection with the drill bit.
• the drill bit is guided in the housing by the sleeve 15 and a guiding bushing 16 and a stop ring 17 prevents the drill bit from falling out.
• the drill bit 14 is thus axially movable a limited distance in the housing 12 and it cannot turn relative to the housing.
• the drill bit 14 has an axial flushing fluid passage that ends in flushing fluid ejecting holes in its front surface.
• a guide bushing 18 takes support against the shoulder 13 and a distance sleeve 19 takes support against the guide bushing 18.
• a valve housing 20 with a back head 38 takes support against the distance sleeve 19. and and a tube formed filter support 21 with a filter 21a takes support against the back head 38 of the valve housing 20.
• a backhead 22 of the machine housing is screwed into the rear end of the tube 12 and it is arranged to axially clamp the parts 18,19,20,38,21 against the shoulder 13. These parts 18,19,20,38,21 act together as a spring and their cumulative lenght is such that they are compressed when the backhead 22 is screwed into place.
• the overall axial compression is 0.4 - 2 mm.
• the distance sleeve 19 contributes most to this compression because of its dominating length and its comparatively small steel area in its cross section. It is adapted to be compressed at least 0.3 and preferably 0.8 - 3 pro mille of its length.
• the filter support 21 may have about the same cross section area of steel as the distance sleeve 19, but it is shorter and its contributon to the spring action is therfore smaller.
• the back head 38 of the valve housing 20 is thus clamped against the main part of the valve housing 20.
• the back head 22 of the machine housing is arranged to be screwed to a conventional drill tubing that transmits rotation to the drilling machine and also transmits hydraulic drive fluid in the form of pressure water to the drilling machine.
• the annular space 58 at the back of the valve housing 20 is thus continuously filled with filtered water under pressure.
• a tube 23 forms part of the valve housing 20.
• a piston hammer 24 with a through channel 25 has its front end guided
• the rear end 27 of the piston hammer 24 extends into an annular cylinder chamber 26 (drive chamber) that is formed in the valve housing 20 between the sleeve-like front portion 35 of the valve housing and the tube 23 of the valve housing.
• the rear end of the piston hammer 24 is thus guided by the walls of the cylinder chamber 26, that is, by the valve housing 20,
• the rear end 27 of the piston hammer 24 has a groove 28 with a rear end wall 29 so that the piston hammer 20 has a defined outer guiding surface 30 behind the end wall 29.
• the piston hammer 24 has also an interior guiding surface 31 of defined length.
• the outer and inner guiding surfaces 30,31 could have about the same length.
• the actual length of the guiding surfaces is defined by the guiding surfaces 18 (at the front end of the piston hammer) and 30,31 (at the rear end of the piston hammer) and it takes up only a minor part of the length of the piston hammer 24.
• the actual length of guiding is less than 20% of the length of the piston hammer.
• the major part 32 of the piston hammer 24 is between these guiding surfaces and it has a wide clearance to the distance sleeve 19 of the machine housing 12.
• the major part 32 of the piston hammer 24 can be radially enlarged as compared with its guided end portions.
• the guiding surface 33 of the piston hammer sliding against the guide bushing 18 has a smaller diameter than the guiding surface 30 against the valve housing 20 so that the piston hammer will have a differential piston area in the front drive chamber 34 that is formed axially between the guide bushing 18 and the valve housing 20. If the groove 28 and the front guiding surface 33 have the same diameter, then this differential area is represented by the area 36, that is, by the area of the rear wall 29 of the groove 28. This differential area is smaller than the annular piston area 37 in the rear cylinder chamber 26.
• the valve housing 20 contains a spool valve 40 with three control surfaces A1,A2,A3 that are in three annular control chambers 45,46,47.
• the effective area of surface A3 is a differential area since the diameter of the sliding surface of the valve 40 close to the surface Al is greater than the diameter of the sliding surface close to the surface A2.
• the relation between these areas are A3 ⁇ Al ⁇ A2+A3 .
• the area A2 is greater than the area A3 and suitably, Al and A2 can be equal or about equal and about twice as large as A3.
• the valve 40 has a row of large holes 50 and two small holes 51.
• a control conduit 52 leads between the annular chamber 46 and the rear cylinder chamber 26 and it has a control port
• a number of parallel channels 57 lead axially through the valve housing 20 and connect the front drive chamber 34 with the continuously pressurized space 58 at the rear of the valve housing 20.
• a number of channels 59 connect a row of ports 60 into the rear drive chamber 26 with a row of ports 61 into the annular chamber 48.
• a number of channels connect a row of ports 62 into the annular chamber 47 with the continuously pressurized space 58 at the back of the valve housing 20.
• valve 40 Presume that the valve 40 is in its illustrated position and that the piston hammer 24 has just begun its work stroke forwardly in order to strike the drill bit 14. ( The piston hammer 24 is shown in its impacting position. )
• the valve 40 connects the rear cylinder chamber 26 with the chamber 58 that is continuously under pressure.
• the control surface Al of the valve is under pressure during the entire work stroke of the piston hammer 24 since the control port 56 of the control passage 54 is at first open to the continuously pressurized front drive chamber 34 and then, shortly after the closing of the port 56, the control port 55 of the control passage 54 is instead opened to the rear drive chamber 26 which is under pressure.
• the length of the guide surface 30 of the piston hammer can be such that both ports 56 and 55 are closed during a short period, which, however, will be so short that it will not influence the pressure in the control passage 54.
• the valve 40 will therefore remain stable in its illustrated forward position because the area Al overcomes the area A3.
• the leakage from the annular chamber 46 prevents a pressure build up in the annular chamber 46.
• the valve 40 is dampened by its nose 65 cutting off a damping chamber so that the valve is retarded before it lands in its rear non-illustrated position and it will therefore not tend to rebounce.
• the annular chamber 48 is cut off from the annular chamber 47 and is instead coupled to the interior of the valve through the holes 50 in the valve. Through the tube 23, the interior of the valve is
• SUBSTITUTE SHEET continuously open to the channel 25 in the piston hammer and the channel 25 is always open to the flushing fluid passage in the drill bit 14.
• the rear drive chamber 26 will therefore be depressurized simultaneously with the piston hammer reaching its impacting position, and the continuously pressurized front drive chamber 34 starts to drive the piston hammer rearwardly in its return stroke.
• control ports 53 and 55 can be varied and the control port 53 need not be axially forwardly of the port 55.
• the water that flows out of the rear drive chamber 26 during the return stroke of the piston hammer 24 is thus utilized as a flushing fluid for flushing the debris out of the borehole.

Landscapes

• Engineering & Computer Science (AREA)
• Geology (AREA)
• Life Sciences & Earth Sciences (AREA)
• Mining & Mineral Resources (AREA)
• Physics & Mathematics (AREA)
• Environmental & Geological Engineering (AREA)
• Fluid Mechanics (AREA)
• Mechanical Engineering (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Earth Drilling (AREA)
• Drilling And Exploitation, And Mining Machines And Methods (AREA)
• Percussive Tools And Related Accessories (AREA)
• Details Of Valves (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=20392073

Family Applications (1)

Country Status (8)

Cited By (1)

Families Citing this family (8)

Family Cites Families (1)

• 1993
  • 1993-12-13 SE SE9304125A patent/SE505170C2/sv not_active IP Right Cessation
• 1994
  • 1994-12-13 EP EP95919251A patent/EP0733152B1/de not_active Expired - Lifetime
  • 1994-12-13 KR KR1019960703110A patent/KR100352883B1/ko not_active Expired - Fee Related
  • 1994-12-13 ES ES95919251T patent/ES2194910T3/es not_active Expired - Lifetime
  • 1994-12-13 WO PCT/SE1994/001201 patent/WO1995016848A1/en not_active Ceased
  • 1994-12-13 JP JP51670395A patent/JP3588467B2/ja not_active Expired - Fee Related
  • 1994-12-13 AU AU12866/95A patent/AU685561B2/en not_active Ceased
  • 1994-12-13 DE DE69432312T patent/DE69432312T2/de not_active Expired - Lifetime

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events