US20140224544A1 - Pneumatic down-the-hole drill - Google Patents
Pneumatic down-the-hole drill Download PDFInfo
- Publication number
- US20140224544A1 US20140224544A1 US14/350,060 US201214350060A US2014224544A1 US 20140224544 A1 US20140224544 A1 US 20140224544A1 US 201214350060 A US201214350060 A US 201214350060A US 2014224544 A1 US2014224544 A1 US 2014224544A1
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- United States
- Prior art keywords
- piston
- combustion chamber
- frame
- percussion piston
- acceleration
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 238000009527 percussion Methods 0.000 claims abstract description 104
- 230000001133 acceleration Effects 0.000 claims abstract description 78
- 238000002485 combustion reaction Methods 0.000 claims abstract description 76
- 239000000446 fuel Substances 0.000 claims abstract description 25
- 238000013016 damping Methods 0.000 claims description 12
- 230000000903 blocking effect Effects 0.000 claims description 10
- 238000011010 flushing procedure Methods 0.000 claims description 10
- 239000000567 combustion gas Substances 0.000 claims description 6
- 230000000149 penetrating effect Effects 0.000 claims 2
- 230000007423 decrease Effects 0.000 claims 1
- 238000005553 drilling Methods 0.000 description 23
- 239000011435 rock Substances 0.000 description 6
- 239000000243 solution Substances 0.000 description 2
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000002828 fuel tank Substances 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
Images
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 chamber, 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 reflecting from the tool do not affect the acceleration piston and do not stress it.
- FIG. 1 shows schematically a rock drilling rig
- FIG. 2 shows schematically another, different rock drilling rig
- FIGS. 3 a to 3 f 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 provided 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 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 10 by means of the rotation unit 7 .
- FIG. 2 shows a second drilling unit 4 , which differs from the one in FIG. 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 .
- FIGS. 3 a to 3 f 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 21 a 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 .
- FIG. 3 a 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 21 b and the acceleration piston includes a stop shoulder 25 a.
- the acceleration piston 25 has stopped before the moment of impact, upon collision of its stop shoulder 25 a 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 21 c 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 24 b and 25 b they comprise working surfaces 24 c and 25 c 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 24 a in the percussion piston 24 together with the inner surface of the counterpart shoulder 21 b, has tightly closed the connection from the space between the stop shoulder 25 a 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.
- the surface area 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 24 f and 24 g on the front end side of the frame 21 and the side 24 e 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.
- FIG. 3 c further shows that the percussion piston 24 having moved a sufficient distance towards the acceleration piston 25 , the blocking shoulder 24 a at the upper end thereof passes by the counterpart shoulder 21 b in the frame 21 in such a manner that a connection opens from the damping chamber 31 to the annular space 21 a 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 25 and to reach it in such a manner that the stop shoulder 25 a of the acceleration piston 25 and the blocking shoulder 24 a of the percussion piston 24 , as well as the working surfaces 24 c and 25 c, will come into contact with one another and the pistons continue their travel towards the combustion chamber 26 at the same rate.
- a working shoulder 24 d 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 24 e of its working shoulder 24 d, and produces a force that pushes the percussion piston 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 extremely 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 23 a 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 24 e of the working shoulder 24 d of the percussion piston 24 , which tends to push the percussion piston 24 towards the tool 22 .
- FIG. 3 e shows a phase, in which the percussion piston 24 has closed the connection of the reversing chamber 21 f into the flushing channel 23 by means of the flushing pipe 23 a in association with the flushing channel 23 .
- a connection has opened from the compressed air feed channel 27 and the space 21 a, around the working shoulder 24 d, into the reversing chamber 21 f, when the working shoulder 24 d 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 24 f in the reversing chamber 21 f, in front of the working shoulder 24 d of the percussion piston 24 , thus decelerating the percussion piston 24 .
- the blocking shoulder 24 a of the percussion piston 24 together with the counterpart shoulder 21 b of the frame, has closed the connection from the damping chamber 31 to the space around the percussion piston, whereby the damping chamber 31 is formed into a closed space, and as the percussion piston 24 and the acceleration piston 25 proceed, the air pressure in the damping chamber 31 rises.
- the pressure cushion formed as the pressure rises decelerates the motion of the acceleration piston 25 , whereby the percussion piston detaches from the acceleration piston 25 , and thus the acceleration piston 25 no longer pushes the percussion piston 24 towards 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.
- 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.
- the acceleration piston 25 does not strike at full speed the stop shoulder 21 b.
- 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 21 b 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 dispensing 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.
- ignition means such as glow plugs or the like
- FIGS. 3 a to 3 f the invention is only illustrated by way of example and schematically.
- the shapes of the frame and the pistons, the positioning and shaping of various channels and shoulders may be implemented in a variety of ways within the scope of the general designing knowledge of a person skilled in the art.
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Abstract
A pneumatic down-the-hole (DTH) drill having a frame, and a pneumatic percussion piston that moves in a reciprocating manner as pressurized air is fed into the DTH-drill and strikes a tool in the front end of the frame is mounted movably in the longitudinal direction of the frame. A feed channel for feeding compressed air to the DTH-drill shoulders in the frame and in the percussion piston for controlling compressed air to provide an impact movement. In the rear end of the frame the DTH drill has a combustion chamber and an acceleration piston that is arranged to push the percussion piston during the impact movement for a portion of the percussion piston travel, and means for feeding combustion air and fuel into the combustion chamber, whereby the percussion piston is arranged to push the acceleration piston after the impact into the combustion chamber and to compress the air in the combustion chamber prior to feeding the fuel into the combustion chamber.
Description
- 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. In these DTH-drills 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.
- Known solutions have a drawback that, for instance, their efficiency is relatively poor. A pneumatic percussion mechanism alone does not provide a sufficient efficiency, and hydraulic percussion devices are not readily used because of pollution risks.
- 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 chamber, 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. Yet another idea of the DTH-drill is that 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 reflecting from the tool do not affect the acceleration piston and do not stress it.
- The invention is now described in greater detail in the attached drawings, in which
-
FIG. 1 shows schematically a rock drilling rig, -
FIG. 2 shows schematically another, different rock drilling rig, and -
FIGS. 3 a to 3 f show schematically the structure of a down-the-hole drill and its operation in various phases of a working cycle. -
FIG. 1 shows arock drilling rig 1 that may comprise amovable carrier 2 provided with adrilling boom 3. Theboom 3 is provided with arock drilling unit 4 comprising afeed beam 5, afeed device 6 and arotation unit 7. Therotation unit 7 may be supported to acarriage 8, or alternatively the rotation unit may comprise sliding parts or the like support members with which it is movably supported to thefeed beam 5. Therotation unit 7 may be provided withdrilling equipment 9 which may comprise one or moreinterconnected drilling pipes 10, and adrill bit 11 at the outermost end of the drilling equipment. Thedrilling unit 4 ofFIG. 1 is intended for rotary drilling in which therotation unit 7 is used for rotating thedrilling equipment 9 about its longitudinal axis in direction R and, at the same time, therotation unit 7 and thedrilling equipment 9 connected to it are fed with feed force F by means of afeed device 6 in drilling direction B. Thus, the drill bit breaks rock by the effect of rotation R and feed force F, and adrill hole 12 is formed. When thedrill hole 12 has been drilled to a desired depth, thedrilling equipment 9 can be pulled by means of thefeed device 6 out of thedrill hole 12 in return direction C, and the drilling equipment can be disassembled by unscrewing connection threads between thedrilling pipes 10 by means of therotation unit 7. -
FIG. 2 shows asecond drilling unit 4, which differs from the one inFIG. 1 in such a way that thedrilling equipment 9 is provided with apercussion device 13. Thepercussion device 13 is thus at the opposite end of thedrilling equipment 9 in relation to therotation unit 7. During drilling, the down-the-hole drill 13 is in the drill hole and the tool with thedrill bit 11 may be connected directly to the down-the-hole drill 13. -
FIGS. 3 a to 3 f show the down-the-hole drill of the invention and its operation in various phases of a working cycle. It comprises aframe 21 and, in the front end of the frame, atool 22 that is mounted movably in the longitudinal direction thereof. In this application and the claims 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, and the rear end refers to the opposite end of the DHT-drill 13. - In the middle of the
tool 22 there is a flushingchannel 23. Further, the DHT-drill 13 comprises apercussion piston 24 that is mounted movably in the longitudinal direction of theframe 21. Additionally, it includes anacceleration piston 25, which in relation to thepercussion piston 24 is in the opposite end of theframe 21, i.e. rear end of the percussion piston, from thetool 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 thepercussion piston 24 there is acombustion chamber 26. The DHT-drill includes afeed channel 27, through which pressurized air is fed into anannular space 21 a between thepercussion piston 24 and theframe 21. Further, the DHT-drill includes anair channel 28, through which compressed air is fed into thecombustion chamber 26, and aninlet valve 29, by which the feed of compressed air is controlled. Theinlet 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 anozzle 30, included in fuel feeding means, through which fuel is fed into thecombustion chamber 26. The DTH-drill further includes timing and feeding means, not shown and known per se, which control fuel feed into thecombustion chamber 26 on the basis of the position of theacceleration piston 25 or the conditions, such as pressure, in thecombustion chamber 26. -
FIG. 3 a shows the DTH-drill in a situation where thepercussion piston 24 has struck thetool 22. Theframe 21 of the DTH-drill includes acounterpart shoulder 21 b and the acceleration piston includes astop shoulder 25 a. InFIG. 3 a theacceleration piston 25 has stopped before the moment of impact, upon collision of itsstop shoulder 25 a with thecounterpart shoulder 21 b in theframe 21. For a portion of their lengths thepercussion piston 24 and theacceleration piston 25 are nested in such a manner that there is never an open gap or a notable clearance therebetween. - Because high pressure still prevails in the
combustion chamber 26, theinlet valve 29 remains closed despite the fact that the pressure of compressed air acts thereon via thechannel 28. The pressure in thecombustion chamber 26 becomes, however, lower and lower while the combustion gases therein will be discharged into theexhaust channel 32 and further into aspace 21 c around the acceleration piston, between said piston and theframe 21, and further throughchannels 33 in theacceleration piston 25, via a space in the middle of the pistons, into the flushingchannel 23. - In
FIG. 3 b thepercussion piston 24 has started its reverse movement and the pressure in thecombustion chamber 26 has decreased to enable the compressed air to push thecheck valve 29 open. At this stage, the air of high pressure, e.g. about 3 to 5 bar, from theair channel 28 flushes combustion gases from thecombustion chamber 26 into theexhaust channel 32 and fills the combustion chamber with fresh air. - For a portion of their lengths the
percussion piston 24 and theacceleration piston 25 are nested in such a manner that there is never an open gap or clearance therebetween. At the nestedparts surfaces acceleration piston 25 pushes thepercussion piston 24 towards thetool 22, or thepercussion piston 24 pushes theacceleration piston 25 towards thecombustion chamber 26. At the same time, a blockingshoulder 24 a in thepercussion piston 24, together with the inner surface of thecounterpart shoulder 21 b, has tightly closed the connection from the space between thestop shoulder 25 a and thecounterpart shoulder 21 b. In this situation the space between thepercussion piston 24 and theacceleration piston 25 forms a closed dampingchamber 31, which is full of compressed air. - As the
percussion piston 24 moves towards theacceleration piston 25, the pressure in the dampingchamber 31 rises and thepercussion piston 24 starts pushing theacceleration piston 25 towards the combustion chamber by means of the formed, pressurized air cushion. In that case theacceleration piston 25, while moving, closes theexhaust channel 32, whereafter a pressure rise in thecombustion chamber 26 pushes theinlet valve 29 closed, as the pressure rises higher than the pressure of air fed by theair channel 28. A so-called compression step thus takes place. Thesurface area 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 24 f and 24 g on the front end side of theframe 21 and theside 24 e facing the rear end of the frame. Said surface area is larger than the surface area of theacceleration piston 25 on the side of thecombustion chamber 26, whereby a sufficient compressive force is obtained for compressing the air in the combustion chamber. -
FIG. 3 c further shows that thepercussion piston 24 having moved a sufficient distance towards theacceleration piston 25, the blockingshoulder 24 a at the upper end thereof passes by thecounterpart shoulder 21 b in theframe 21 in such a manner that a connection opens from the dampingchamber 31 to theannular space 21 a between thepercussion piston 24 and theframe 21, whereby the pressure in the dampingchamber 31 drops. As a result, thepercussion piston 24 is able to move towards theacceleration piston 25 and to reach it in such a manner that thestop shoulder 25 a of theacceleration piston 25 and the blockingshoulder 24 a of thepercussion piston 24, as well as the workingsurfaces combustion chamber 26 at the same rate. - As the
percussion piston 24 and theacceleration piston 25 move towards thecombustion chamber 26, a workingshoulder 24 d in the lower end of thepercussion piston 24 becomes in alignment with acontrol shoulder 21 d in the frame and closes the connection from a reversing chamber 21 f, which is at the end of thepercussion piston 24 on the side of thetool 22, into thefeed channel 27. At the same time thepercussion piston 24 continues its motion with theacceleration piston 25 towards thecombustion chamber 26. From this moment on, the pressure in the compressed air from thefeed channel 27 starts acting on thepercussion piston 24, on the workingsurface 24 e of its workingshoulder 24 d, and produces a force that pushes the percussion piston towards thetool 22. This decelerates the motion of thepercussion piston 24 and theacceleration piston 25 slightly. - In
FIG. 3 d, thepercussion piston 24 and theacceleration piston 25 have compressed the air in thecombustion chamber 26 to have extremely high pressure and fuel is fed through anozzle 30 into the combustion chamber, which fuel ignites because of the heated, compressed air causing a steep rise in pressure in thecombustion chamber 26 in accordance with the operating principle of a diesel engine. - In the final part of the percussion piston motion, prior to said situation, the
percussion piston 24 has passed by the end of a flushingpipe 23 a in connection with the flushingchannel 23 and thus opened a connection from the reversing chamber 21 f to the flushingchannel 23, whereby the pressurized air in the reversing chamber 21 f discharges there. In that situation thepercussion piston 24 and theacceleration piston 25 start an impact movement upon ignition of the fuel. At the same time, highly pressurized air from thefeed channel 27 acts on the workingsurface 24 e of the workingshoulder 24 d of thepercussion piston 24, which tends to push thepercussion piston 24 towards thetool 22. -
FIG. 3 e shows a phase, in which thepercussion piston 24 has closed the connection of the reversing chamber 21 f into the flushingchannel 23 by means of the flushingpipe 23 a in association with the flushingchannel 23. In the situation shown in the figure, a connection has opened from the compressedair feed channel 27 and thespace 21 a, around the workingshoulder 24 d, into the reversing chamber 21 f, when the workingshoulder 24 d has passed by thecontrol shoulder 21 d. In this situation, thepercussion piston 24 and theacceleration piston 25 further continue the motion at the same rate in the direction of thetool 22, still in contact with one another, but the force produced by the pressure in the compressed air acts against the travel direction of thepercussion piston 24 because of the larger reversingsurface 24 f in the reversing chamber 21 f, in front of the workingshoulder 24 d of thepercussion piston 24, thus decelerating thepercussion piston 24. - In
FIG. 3 f the blockingshoulder 24 a of thepercussion piston 24, together with thecounterpart shoulder 21 b of the frame, has closed the connection from the dampingchamber 31 to the space around the percussion piston, whereby the dampingchamber 31 is formed into a closed space, and as thepercussion piston 24 and theacceleration piston 25 proceed, the air pressure in the dampingchamber 31 rises. As a result, the pressure cushion formed as the pressure rises, decelerates the motion of theacceleration piston 25, whereby the percussion piston detaches from theacceleration piston 25, and thus theacceleration piston 25 no longer pushes thepercussion piston 24 towards thetool 22. - As the
acceleration piston 25 continues its movement towards the front end of theframe 21 a connection opens to theexhaust channel 32. As the pistons move onwards, negative pressure is formed in thespace 21 c around theacceleration piston 25, because the surface area of thestop shoulder 25 a in the front end of theacceleration piston 25 is larger than the surface area of theacceleration piston 25 in thecombustion chamber 26. Consequently, the produced negative pressure aspirates the combustion gases quickly into thespace 21 c, which enhances the flushing of thecombustion chamber 26. - After this, the situation of
FIG. 3 a occurs again, in which thepercussion piston 24 has struck thetool 22 and theacceleration piston 25 has stopped to theshoulders - It is essential in the operation of the
percussion piston 24 and theacceleration piston 25 that as thepercussion piston 24 strikes thetool 22, theacceleration piston 25 is no longer in impact-direction contact with thepercussion piston 24, but it has stopped prior to the impact moment. Thus theacceleration piston 25 does not receive any impact stress, nor the stress caused by a reflection impulse from thetool 22, but all the stress is exerted on the percussion piston alone. Further, it is essential in the operation that theacceleration piston 25 does not strike at full speed thestop shoulder 21 b. Thus its impact rate is decelerated by a compressed air cushion in the dampingchamber 31 in such a manner that the rate of theacceleration piston 25 on impact with thestop shoulder 21 b of theframe 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 dispensing 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.
- In
FIGS. 3 a to 3 f the invention is only illustrated by way of example and schematically. The shapes of the frame and the pistons, the positioning and shaping of various channels and shoulders may be implemented in a variety of ways within the scope of the general designing knowledge of a person skilled in the art.
Claims (16)
1. A pneumatic down-the-hole drill having a frame and inside the frame a pneumatic percussion piston that moves in a reciprocating manner in a 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 drill comprising:
a combustion chamber at a rear end of the frame;
a separate acceleration piston disposed in the combustion chamber between the frame and the 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; and
an exhaust channel for exhausting combustion gases from the combustion chamber, whereby the percussion piston is arranged to push the acceleration piston by means of pressurized air back into the combustion chamber after each impact movement and thus to compress the air in the combustion chamber prior to feeding fuel into the combustion chamber.
2. The down-the-hole drill of claim 1 , wherein the acceleration piston is arranged to close the exhaust channel before penetrating into the combustion chamber and to open the exhaust channel before its forward motion ends.
3. The down-the-hole drill of claim 1 , wherein the air channel includes a blocking valve that opens as the pressure in the combustion chamber drops below a predetermined pressure level and that from the air channel, the blocking valve being open, pressurized air is arranged to flow for flushing the combustion chamber and for filling the combustion chamber with fresh combustion air.
4. The down-the-hole drill of claim 1 , wherein the acceleration piston includes a stop shoulder and at the same point in the frame, in an axial direction, a counterpart shoulder, so that as the shoulders meet the acceleration piston stops before the percussion piston strikes the tool.
5. The down-the-hole drill of claim 4 , wherein the percussion piston and the acceleration piston are for a portion of their length closely nested so that no clearance opens at any stage between them, the percussion piston including in its upper end a blocking shoulder, which as the pistons move in the impact direction, before the stop shoulder of the acceleration piston hits the counterpart shoulder of the frame, together with the counterpart shoulder closes a connection from a space between the stop shoulder and the counterpart shoulder in such a manner that a damping chamber is provided and while the acceleration piston moves onwards its volume decreases and the pressure of the compressed air contained therein increases and decelerates the movement of the acceleration piston, and correspondingly during the reversing movement of the percussion piston pushes the acceleration piston towards the combustion chamber before the blocking shoulder opens a connection from the damping chamber so that the percussion piston may displace air from the damping chamber and reach the acceleration piston for pushing it back into the combustion chamber.
6. The down-the-hole drill of claim 1 , further comprising timing equipment for timing fuel feed in relation to the position of the acceleration piston.
7. The down-the-hole drill of claim 1 , wherein the percussion piston includes a working shoulder having a tool-side surface area that is larger than a surface facing the acceleration piston, the frame including an auxiliary shoulder so that in the rear position of the percussion piston, with the shoulders being aligned, the pressure of the compressed air only acts on the surface facing the acceleration piston producing a force that pushes the percussion piston towards the tool, and in the front position of the percussion piston, with the shoulders being apart, the pressure of the compressed air acts on both surfaces producing a force that pushes the percussion piston away from the tool.
8. The down-the-hole drill of of claim 7 , wherein in the percussion piston the surface area of the surfaces which are facing the front end of the frame and through which the pressurized air pushes the percussion piston and the acceleration piston towards the combustion chamber, is larger than the surface area of the acceleration piston facing the combustion chamber.
9. A pneumatic down-the-hole drill comprising:
a frame;
a pneumatic percussion piston movably mounted in a longitudinal direction within the frame, the pneumatic percussion piston reciprocating along the longitudinal direction of the frame to impact a tool that is disposed at a front end of the frame;
a feed channel to guide pressurized air between the frame and the percussion piston and shoulders in the frame and in the percussion piston;
a combustion chamber disposed at a rear end of the frame;
an acceleration piston disposed in the combustion chamber between the frame and the percussion piston and moving in the longitudinal direction of the frame;
an air channel for feeding combustion air into the combustion chamber;
means for injecting fuel into the combustion chamber; and
an exhaust channel to exhaust combustion gases from the combustion chamber.
10. The down-the-hole drill of claim 9 , wherein the acceleration piston is arranged to close the exhaust channel before penetrating into the combustion chamber and to open the exhaust channel.
11. The down-the-hole drill of claim 9 , wherein the air channel includes a blocking valve that opens as the pressure in the combustion chamber drops below a predetermined pressure allowing pressurized air to flush the combustion chamber and fill the combustion chamber with fresh combustion air.
12. The down-the-hole drill of claim 9 , wherein the acceleration piston includes a stop shoulder and at the same point in the frame, in an axial direction, a counterpart shoulder to stop the acceleration piston before the percussion piston strikes the tool.
13. The down-the-hole drill of claim 12 , wherein the percussion piston and the acceleration piston are for a portion of their length closely nested so that no clearance exists therebetween, the percussion piston including in its upper end a blocking shoulder, which as the pistons move in the impact direction, before the stop shoulder of the acceleration piston hits the counterpart shoulder of the frame, together with the counterpart shoulder closes a connection from a space between the stop shoulder and the counterpart shoulder to provide a damping chamber.
14. The down-the-hole drill of claim 9 , further comprising timing equipment to time fuel feed in relation to the position of the acceleration piston.
15. The down-the-hole drill of claim 9 , wherein the percussion piston includes a working shoulder having a tool-side surface area that is larger than a surface facing the acceleration piston.
16. The down-the-hole drill of claim 15 , wherein in the percussion piston the surface area of the surfaces which are facing the front end of the frame and through which the pressurized air pushes the percussion piston and the acceleration piston towards the combustion chamber, is larger than the surface area of the acceleration piston facing the combustion chamber.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FI20115980A FI123555B (en) | 2011-10-06 | 2011-10-06 | Compressed air driven lowering drill |
FI20115980 | 2011-10-06 | ||
PCT/FI2012/050954 WO2013050657A1 (en) | 2011-10-06 | 2012-10-04 | Pneumatic down-the-hole drill |
Publications (1)
Publication Number | Publication Date |
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US20140224544A1 true US20140224544A1 (en) | 2014-08-14 |
Family
ID=44883648
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US14/350,060 Abandoned US20140224544A1 (en) | 2011-10-06 | 2012-10-04 | Pneumatic down-the-hole drill |
Country Status (11)
Country | Link |
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US (1) | US20140224544A1 (en) |
EP (1) | EP2751368B1 (en) |
JP (1) | JP5854536B2 (en) |
KR (1) | KR101513843B1 (en) |
CN (1) | CN103842606B (en) |
AU (1) | AU2012320368B2 (en) |
CA (1) | CA2850907C (en) |
CL (1) | CL2014000837A1 (en) |
FI (1) | FI123555B (en) |
WO (1) | WO2013050657A1 (en) |
ZA (1) | ZA201402459B (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20140305707A1 (en) * | 2011-10-06 | 2014-10-16 | Sandvik Mining And Construction Oy | Fuel Tank |
CN107313714A (en) * | 2017-08-29 | 2017-11-03 | 吉林大学 | A kind of valve bush type is without air cushion high-performance air hammer |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
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WO2018003668A1 (en) * | 2016-06-28 | 2018-01-04 | 古河ロックドリル株式会社 | Two-piston hydraulic striking device |
EP3409879B1 (en) * | 2017-06-02 | 2019-11-20 | Sandvik Intellectual Property AB | Down the hole drilling machine and method for drilling rock |
CA3119835A1 (en) | 2018-11-13 | 2020-05-22 | Rubicon Oilfield International, Inc. | Three axis vibrating device |
SE1951244A1 (en) | 2019-10-31 | 2021-04-20 | Epiroc Drilling Tools Ab | Pneumatic drill hammer comprising a boost chamber and a drilling rig comprising such a drill hammer |
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SE393940B (en) * | 1973-12-31 | 1977-05-31 | Atlas Copco Ab | PROCEDURE FOR DAMPING OF THE MOVEMENT OF A PATCH PISTON INCLUDING IN A PENCIL AND A PERCENTAGE FOR PERFORMING THE PROCEDURE |
FR2528104A1 (en) * | 1982-06-04 | 1983-12-09 | Stenuick Freres | HAMMER OF DRILLING |
US4747466A (en) * | 1983-09-06 | 1988-05-31 | Jaworski Bill L | Impact tool |
CN1009848B (en) * | 1987-01-22 | 1990-10-03 | 英格索尔-兰德公司 | Down hole drill improvement |
SE500654C2 (en) * | 1987-07-14 | 1994-08-01 | G Drill Ab | Hydraulic submersible drill |
US5662180A (en) * | 1995-10-17 | 1997-09-02 | Dresser-Rand Company | Percussion drill assembly |
SE507651C2 (en) * | 1997-07-02 | 1998-06-29 | Uniroc Ab | Lowering drill with double driver areas for the stroke and return stroke of the piston |
FI117548B (en) * | 2005-03-24 | 2006-11-30 | Sandvik Tamrock Oy | The impactor, |
US7353845B2 (en) * | 2006-06-08 | 2008-04-08 | Smith International, Inc. | Inline bladder-type accumulator for downhole applications |
CN101492997A (en) * | 2008-01-21 | 2009-07-29 | 姚小林 | Hydraulic down-the-hole rock drilling impactor |
CN201301664Y (en) * | 2008-11-26 | 2009-09-02 | 宜昌市五环钻机具有限责任公司 | Down-the-hole hammer |
CN201502318U (en) * | 2009-09-03 | 2010-06-09 | 李保顺 | High air-pressure down-the-hole hammer |
CN201653273U (en) * | 2010-03-22 | 2010-11-24 | 中国兵器工业第二一三研究所 | Hydraulic damping hot-working driving device |
-
2011
- 2011-10-06 FI FI20115980A patent/FI123555B/en active IP Right Grant
-
2012
- 2012-10-04 KR KR1020147011982A patent/KR101513843B1/en not_active IP Right Cessation
- 2012-10-04 EP EP12838275.1A patent/EP2751368B1/en active Active
- 2012-10-04 US US14/350,060 patent/US20140224544A1/en not_active Abandoned
- 2012-10-04 CN CN201280049234.4A patent/CN103842606B/en not_active Expired - Fee Related
- 2012-10-04 WO PCT/FI2012/050954 patent/WO2013050657A1/en active Application Filing
- 2012-10-04 AU AU2012320368A patent/AU2012320368B2/en not_active Ceased
- 2012-10-04 JP JP2014533955A patent/JP5854536B2/en not_active Expired - Fee Related
- 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/en unknown
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20140305707A1 (en) * | 2011-10-06 | 2014-10-16 | Sandvik Mining And Construction Oy | Fuel Tank |
CN107313714A (en) * | 2017-08-29 | 2017-11-03 | 吉林大学 | A kind of valve bush type is without air cushion high-performance air hammer |
Also Published As
Publication number | Publication date |
---|---|
JP2014531543A (en) | 2014-11-27 |
FI20115980A (en) | 2013-04-07 |
AU2012320368A1 (en) | 2014-05-22 |
JP5854536B2 (en) | 2016-02-09 |
EP2751368A1 (en) | 2014-07-09 |
FI123555B (en) | 2013-07-15 |
WO2013050657A1 (en) | 2013-04-11 |
EP2751368B1 (en) | 2017-12-27 |
CA2850907A1 (en) | 2013-04-11 |
CN103842606A (en) | 2014-06-04 |
AU2012320368B2 (en) | 2016-02-04 |
EP2751368A4 (en) | 2016-06-29 |
CA2850907C (en) | 2016-04-12 |
CN103842606B (en) | 2016-02-24 |
KR101513843B1 (en) | 2015-04-20 |
ZA201402459B (en) | 2015-03-25 |
KR20140067167A (en) | 2014-06-03 |
CL2014000837A1 (en) | 2014-09-12 |
FI20115980A0 (en) | 2011-10-06 |
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Legal Events
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Owner name: SANDVIK MINING AND CONSTRUCTION OY, FINLAND Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:HEDLUND, JUHA;KESKINIVA, MARKKU;LEPPANEN, JARMO;SIGNING DATES FROM 20140401 TO 20140402;REEL/FRAME:032635/0460 |
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AS | Assignment |
Owner name: HARRISON SPINKS COMPONENTS LIMITED, UNITED KINGDOM Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:SPINKO LIMITED;REEL/FRAME:038729/0718 Effective date: 20151222 |
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