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
• • 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
• • 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
  • E21B4/20—Drives for drilling, used in the borehole combined with surface drive

Definitions

• the invention relates to a pneumatic down-the-hole drill having a frame and inside the frame a pneumatic percussion piston that moves in a reciprocating manner in the longitudinal direction of the frame when pressurized air is fed into the down-the-hole drill and at the end of its impact movement strikes a tool that is in the front end of the frame and mounted movably in the longitudinal direction of the frame, a feed channel for feeding pressurized air between the frame and the percussion piston, and shoulders in the frame and in the percussion piston to guide the pressurized air to provide the impact movement.
• the down-the-hole drills are used for drilling holes in a rock.
• a tool is connected immediately in front of the DTH-drill and it is subjected to impacts with a percussion device of the DTH-drill.
• the object of the present invention is to provide a pneumatic DTH-drill that is simple and works reliably.
• the DTH-drill of the invention is characterized by comprising a combustion chamber at the rear end of the frame, and in the combustion chamber a separate acceleration piston between the frame and a percussion piston, moving in the longitudinal direction of the frame and operating by fuel combustion in the combustion chamber, which acceleration piston is arranged to push the percussion piston during the impact movement only for a portion of the percussion piston travel, an air channel for feeding combustion air into the combustion chamber, means for injecting fuel into the combustion chamber, an exhaust channel for exhausting combustion gases from the combustion cham- ber, whereby the percussion piston is arranged to push the acceleration piston by means of pressurized air back into the combustion chamber after each impact and thus to compress the air in the combustion chamber prior to feeding fuel into the combustion chamber.
• the idea of the DTH-drill is that it includes a separate, pneumatic percussion piston that strikes the tool and a separate acceleration piston operating by fuel combustion, which accelerates the percussion piston motion but will be off the percussion piston for the duration of the impact so that a working stroke will be performed by the percussion piston alone.
• the acceleration piston is returned to the initial position by pushing it with the percussion piston by means of the pressure in compressed air.
• An advantage with the invention is that the striking being performed with a percussion piston accelerated with a fuel-operated acceleration piston a required impact power will be provided. However, as the acceleration piston is off the percussion piston at the time of the impact, recoil forces re- fleeting from the tool do not affect the acceleration piston and do not stress it.
• Figure 1 shows schematically a rock drilling rig
• Figure 2 shows schematically another, different rock drilling rig
• Figures 3a to 3f show schematically the structure of a down-the-hole drill and its operation in various phases of a working cycle.
• FIG. 1 shows a rock drilling rig 1 that may comprise a movable carrier 2 provided with a drilling boom 3.
• the boom 3 is provided with a rock drilling unit 4 comprising a feed beam 5, a feed device 6 and a rotation unit 7.
• the rotation unit 7 may be supported to a carriage 8, or alternatively the rotation unit may comprise sliding parts or the like support members with which it is movably supported to the feed beam 5.
• the rotation unit 7 may be provid- ed with drilling equipment 9 which may comprise one or more interconnected drilling pipes 10, and a drill bit 11 at the outermost end of the drilling equipment.
• the drilling unit 4 of Figure 1 is intended for rotary drilling in which the rotation unit 7 is used for rotating the drilling equipment 9 about its longitudinal axis in direction R and, at the same time, the rotation unit 7 and the drilling equipment 9 connected to it are fed with feed force F by means of a feed device 6 in drilling direction B.
• the drill bit breaks rock by the effect of rotation R and feed force F, and a drill hole 12 is formed.
• the drilling equipment 9 can be pulled by means of the feed device 6 out of the drill hole 12 in return direction C, and the drilling equipment can be disassembled by unscrewing connection threads between the drilling pipes 0 by means of the rotation unit 7.
• Figure 2 shows a second drilling unit 4, which differs from the one in Figure 1 in such a way that the drilling equipment 9 is provided with a percussion device 13.
• the percussion device 13 is thus at the opposite end of the drilling equipment 9 in relation to the rotation unit 7.
• the down-the-hole drill 13 is in the drill hole and the tool with the drill bit 11 may be connected directly to the down-the-hole drill 13.
• Figures 3a to 3f show the down-the-hole drill of the invention and its operation in various phases of a working cycle. It comprises a frame 21 and, in the front end of the frame, a tool 22 that is mounted movably in the longitudinal direction thereof.
• the front end refers to the end of the DTH-drill 13 where the tool is and in which direction the DTH- drill 13 advances in drilling
• the rear end refers to the opposite end of the DHT-drill 13.
• the DHT-drill 13 comprises a percussion piston 24 that is mounted movably in the longitudinal direction of the frame 21. Additionally, it includes an acceleration piston 25, which in relation to the percussion piston 24 is in the opposite end of the frame 21 , i.e. rear end of the percussion piston, from the tool 22, and it is mounted movably in the longitudinal direction of the DHT-drill frame 21. Behind the acceleration piston, on the side away from the percussion piston 24 there is a combustion chamber 26.
• the DHT-drill includes a feed channel 27, through which pressurized air is fed into an annular space 21a between the percussion piston 24 and the frame 21.
• the DHT-drill includes an air channel 28, through which compressed air is fed into the combustion chamber 26, and an inlet valve 29, by which the feed of compressed air is controlled.
• the inlet valve 29 may be any appropriate valve structure, or one known per se, and herein it is illustrated, by way of example, by a check valve. It further comprises a nozzle 30, included in fuel feeding means, through which fuel is fed into the combustion chamber 26.
• the DTH-drill further includes timing and feeding means, not shown and known per se, which control fuel feed into the combustion chamber 26 on the basis of the position of the acceleration piston 25 or the conditions, such as pressure, in the combustion chamber 26.
• Figure 3a shows the DTH-drill in a situation where the percussion piston 24 has struck the tool 22.
• the frame 21 of the DTH-drill includes a counterpart shoulder 21b and the acceleration piston includes a stop shoulder 25a.
• the acceleration piston 25 has stopped before the mo- ment of impact, upon collision of its stop shoulder 25a with the counterpart shoulder 21 b in the frame 21.
• the percussion piston 24 and the acceleration piston 25 are nested in such a manner that there is never an open gap or a notable clearance therebetween.
• the inlet valve 29 remains closed despite the fact that the pressure of compressed air acts thereon via the channel 28.
• the pressure in the combustion chamber 26 becomes, however, lower and lower while the combustion gases therein will be discharged into the exhaust channel 32 and further into a space 21c around the acceleration piston, between said piston and the frame 21 , and further through channels 33 in the acceleration piston 25, via a space in the middle of the pistons, into the flushing channel 23.
• the percussion piston 24 and the acceleration piston 25 are nested in such a manner that there is never an open gap or clearance therebetween.
• the nested parts 24b and 25b they comprise working surfaces 24c and 25c which are in contact with one another, when the acceleration piston 25 pushes the percussion piston 24 towards the tool 22, or the percussion piston 24 pushes the acceleration piston 25 towards the combustion chamber 26.
• a blocking shoulder 24a in the percussion piston 24, together with the inner surface of the counterpart shoulder 21b has tightly closed the connection from the space between the stop shoulder 25a and the counterpart shoulder 21 b. In this situation the space between the percussion piston 24 and the acceleration piston 25 forms a closed damping chamber 31 , which is full of compressed air.
• 24 of the percussion piston on which the pressure of the compressed air acts and thus generates a force reversing the pistons, is formed by the difference between the percussion piston surfaces 24f and 24g on the front end side of the frame 21 and the side 24e facing the rear end of the frame. Said surface area is larger than the surface area of the acceleration piston 25 on the side of the combustion chamber 26, whereby a sufficient compressive force is obtained for compressing the air in the combustion chamber.
• Figure 3c further shows that the percussion piston 24 having moved a sufficient distance towards the acceleration piston 25, the blocking shoulder 24a at the upper end thereof passes by the counterpart shoulder 21b in the frame 21 in such a manner that a connection opens from the damping chamber 31 to the annular space 21a between the percussion piston 24 and the frame 21 , whereby the pressure in the damping chamber 31 drops.
• the percussion piston 24 is able to move towards the acceleration piston
• a working shoulder 24d in the lower end of the percussion piston 24 becomes in alignment with a control shoulder 21 d in the frame and closes the connection from a reversing chamber 21 f, which is at the end of the percussion piston 24 on the side of the tool 22, into the feed channel 27.
• the percussion piston 24 continues its motion with the acceleration piston 25 towards the combustion chamber 26. From this moment on, the pressure in the compressed air from the feed channel 27 starts acting on the percussion piston 24, on the working surface 24e of its working shoulder 24d, and produces a force that pushes the percussion pis- ton towards the tool 22. This decelerates the motion of the percussion piston 24 and the acceleration piston 25 slightly.
• the percussion piston 24 and the acceleration piston 25 have compressed the air in the combustion chamber 26 to have ex- tremely high pressure and fuel is fed through a nozzle 30 into the combustion chamber, which fuel ignites because of the heated, compressed air causing a steep rise in pressure in the combustion chamber 26 in accordance with the operating principle of a diesel engine.
• the percussion piston 24 has passed by the end of a flushing pipe 23a in connection with the flushing channel 23 and thus opened a connection from the reversing chamber 21 f to the flushing channel 23, whereby the pressurized air in the reversing chamber 21 f discharges there.
• the percussion piston 24 and the acceleration piston 25 start an impact movement upon ignition of the fuel.
• highly pressurized air from the feed channel 27 acts on the working surface 24e of the working shoulder 24d of the percussion piston 24, which tends to push the percussion piston 24 towards the tool 22.
• Figure 3e shows a phase, in which the percussion piston 24 has closed the connection of the reversing chamber 21f into the flushing channel 23 by means of the flushing pipe 23a in association with the flushing channel 23.
• a connection has opened from the compressed air feed channel 27 and the space 21a, around the working shoulder 24d, into the reversing chamber 21 f, when the working shoulder 24d has passed by the control shoulder 21 d.
• the percussion piston 24 and the acceleration piston 25 further continue the motion at the same rate in the direction of the tool 22, still in contact with one another, but the force produced by the pressure in the compressed air acts against the travel direction of the percussion piston 24 because of the larger reversing surface 24f in the reversing chamber 21 f, in front of the working shoulder 24d of the percussion piston 24, thus decelerating the percussion piston 24.
• the acceleration piston 25 It is essential in the operation of the percussion piston 24 and the acceleration piston 25 that as the percussion piston 24 strikes the tool 22, the acceleration piston 25 is no longer in impact-direction contact with the percussion piston 24, but it has stopped prior to the impact moment. Thus the acceleration piston 25 does not receive any impact stress, nor the stress caused by a reflection impulse from the tool 22, but all the stress is exerted on the percussion piston alone. Further, it is essential in the operation that the acceleration piston 25 does not strike at full speed the stop shoulder 21b. Thus its impact rate is decelerated by a compressed air cushion in the damping chamber 31 in such a manner that the rate of the acceleration piston 25 on impact with the stop shoulder 21b of the frame 21 is sufficiently low so that the materials withstand the stresses caused by the impact.
• Fuel feed for a DTH-drill may be implemented in various ways known per se by using fuel feed hoses, fuel tanks etc. Fuel injection may be implemented by several, different technical methods by using mechanical, electrical, pneumatic or other known solutions for timing fuel feed and for dis- pensing a quantity of fuel.
• the DTH-drill may also be operated by compressed air alone, without feeding fuel into the combustion chamber, and naturally in that case its power is considerably lower. It may be used, for instance, when for one reason or another drilling is to be done very cautiously. Likewise, it allows the operation of the acceleration piston to be started without separate ignition means, such as glow plugs or the like, just by striking the acceleration piston with the percussion piston until the air in the combustion chamber is sufficiently hot for igniting the fuel.

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• 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)
• Portable Nailing Machines And Staplers (AREA)
• Earth Drilling (AREA)
• Percussive Tools And Related Accessories (AREA)

Priority Applications (8)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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Cited By (1)

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Citations (3)

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• 2011
  • 2011-10-06 FI FI20115980A patent/FI123555B/fi active IP Right Grant
• 2012
  • 2012-10-04 CN CN201280049234.4A patent/CN103842606B/zh not_active Expired - Fee Related
  • 2012-10-04 JP JP2014533955A patent/JP5854536B2/ja not_active Expired - Fee Related
  • 2012-10-04 US US14/350,060 patent/US20140224544A1/en not_active Abandoned
  • 2012-10-04 AU AU2012320368A patent/AU2012320368B2/en not_active Ceased
  • 2012-10-04 WO PCT/FI2012/050954 patent/WO2013050657A1/en active Application Filing
  • 2012-10-04 KR KR1020147011982A patent/KR101513843B1/ko not_active Expired - Fee Related
  • 2012-10-04 EP EP12838275.1A patent/EP2751368B1/en not_active Not-in-force
  • 2012-10-04 CA CA2850907A patent/CA2850907C/en not_active Expired - Fee Related
• 2014
  • 2014-04-02 ZA ZA2014/02459A patent/ZA201402459B/en unknown
  • 2014-04-04 CL CL2014000837A patent/CL2014000837A1/es unknown

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