FI20215527A1 - Drilling rig for drilling a borehole into the ground - Google Patents

Abstract

The invention relates to a drilling device (100) for drilling a borehole (22) in soil (102), which drilling device (100) comprises a multi-part blade (5,9), a percussion device (14), a rotating device (50), a first flow channel, a protective tube (3) and an arrangement (24) for pulling the protective tube (3) into the borehole, wherein the blade (5,9) includes a pilot blade (9) and expansion means (5), the pilot blade (9) comprising - a blade surface (12), - a flushing channel (4), - at least one return channel (1), - at least one blade flushing channel (10), wherein the total cross-sectional area of the return channel (1) or return channels (1) is greater than the total cross-sectional area of the blade flushing channel (10) or blade flushing channels (10), and - at least one outlet channel (7), which is wider in cross-sectional area in the flow direction than the blade surface (12) towards the interior (20) of the protective tube (3), and the depth of the outlet channel (7) is increasing in the width direction of the outlet channel (7) in the direction opposite to the direction of rotation of the blade (5,9), and the expansion means (5) extend in the longitudinal direction of the blade (5,9) to the front side of the pilot blade (9) in the drilling direction, whereby the end of the blade flushing channel (10) on the face of the pilot blade (9) is in the radial direction of the blade (5,9) between the pilot blade (9) and the expansion means (5).

Description

DRILLING EQUIPMENT FOR DRILLING A HOLE IN THE GROUND

The invention relates to a drilling device for drilling a borehole in the ground, which drilling device comprises a multi-part bit, an impact device connected to the bit for imparting an impact movement to the bit, a rotating device for rotating the bit, a first flow channel connected to the impact device for conducting a pressurized working air flow to the impact device for operating the impact device, a protective tube comprising a front part and an interior space adapted to be pulled into the borehole to be drilled during drilling, and an arrangement between the front part of the protective tube and the blade for pulling the protective tube into the borehole following the blade by means of an arrangement, wherein the blade comprises - a pilot blade and expansion means, the pilot blade comprising a blade surface, - a flushing channel formed in the pilot blade for conducting a flushing air flow from the impact device to said blade, - at least one return channel arranged in the pilot blade between the flushing channel and the interior space of the protective tube for conducting a part of the flushing air flow directly into the interior space of the protective tube, wherein the return channel branches off from the flushing channel, - at least one blade flushing channel arranged between the pilot blade flushing channel and the blade surface of the pilot blade,

O 25 for directing a flushing air flow to the blade surface for flushing the blade surface ro, where the combined cross-sectional area of the return channel or return channels is greater than the combined cross-sectional area of the blade flushing channel = or blade flushing channels, and

N - exhaust channel fitted to the pilot blade between the blade surface and the interior of the io 30 protective tube to conduct the compressed air flow

N inside the protective tube, which is the outlet channel for the blade rotation

N parallel to the axis of the blade and adapted to expand in the flow direction in cross-sectional area as it goes from the blade surface towards the interior of the protective tube, where the discharge channel has a longitudinal blade

parallel edges, the radial depth of the blade and the width between the edges, and the depth of the outlet channel is increasing in the width direction of the outlet channel when going in the direction opposite to the direction of rotation of the blade to facilitate the movement of drilling waste.

The problem with air-operated, impacting and simultaneously drilling downhole drilling rigs has been to organize the flushing in such a way that the air pressure shocks do not cause harm to old piles in the ground or other structures there. The disadvantages caused by compressed air are, for example, that the compressed air flushes too much material from the drilled borehole, thus causing dangerous subsidence or even complete collapse.

The applicant's own prior art publication FI 126918 is known.

B, where the solution to the above-mentioned problem is to use exhaust channels extending backwards from the pilot bit into the pipe, into which the main part of the air flow intended for flushing is directed, the blade flushing channels leading to the blade surface being smaller in total cross-sectional area than the air flow return channels led backwards directly into the casing. However, the problem with such a structure is that — drilling waste coming out of the soil clogs the casing inwards

O 25 existing drilling waste discharge channels, allowing the pressure against the soil to increase. The problem worsens as the diameter of the pilot bit increases.

Tr a ~~ As the drilling diameter increases, a large diameter io 30 drill rod is used to increase the air flow rate to a level that

N that it can lift the cuttings up from the borehole. If

N drilled rock fragments are too large, they make it difficult for the drill rod to rotate, causing additional friction between the drill rod and the casing being installed. Especially if the air speed is not enough to lift the pieces from the borehole at all, the rotation will jam completely and interrupt the entire drilling operation. For this reason, the soy groove, or outlet channel, must be prepared in such a way that only a certain size of rock can be raised inside the casing.

The material that enters the protective pipe is always as large as it is possible to pass through the discharge channel.

The purpose of the invention is to provide a drilling device that operates more efficiently than prior art drilling devices, in which the clogging of the discharge channels is reduced. The characteristic features of this invention are apparent from the accompanying patent claim 1.

The purpose of the drilling device according to the invention can be achieved by a drilling device comprising a multi-part blade, an impact device connected to the blade for imparting an impact movement to the blade, a rotation device for rotating the blade, a first flow channel connected to the impact device for conducting a flow of pressurized working air to the impact device for operating the impact device, a protective tube comprising a front part and an interior space adapted to be pulled into a borehole to be drilled during drilling, and an arrangement between the front part of the protective tube and the blade for pulling the protective tube into the borehole following the blade via the arrangement.

The blade includes a pilot blade and expansion means, the pilot blade — comprising a blade surface, a flushing channel formed in the pilot

O 25 for directing the flushing air flow from the impact device ro to said blade, the flushing channel branching into return channels, and at least one return channel adapted to the pilot blade = part for directing the flushing air flow directly to the protective tube

N to the interior. The return channel branches off from the flushing channel. In addition, the io 30 blade includes a blade flushing channel fitted to the pilot blade

N between the flushing channel and the blade surface of the pilot blade

N for directing a flushing air flow to the blade surface for flushing the blade surface, wherein the combined cross-sectional area of the return channel or channels is greater than the combined cross-sectional area of the blade flushing channel or channels, and at least one exhaust channel arranged between the blade surface of the pilot blade and the interior of the protective tube for directing the compressed air flow to the interior of the protective tube. The exhaust channel is parallel to the axis of rotation of the blade and is arranged to expand in cross-sectional area in the flow direction from the blade surface towards the interior of the protective tube, wherein the exhaust channel has edges in the longitudinal direction of the blade, a radial depth of the blade and a width between the edges, and the depth of the exhaust channel is increasing in the width direction of the exhaust channel in the direction opposite to the direction of rotation of the blade to facilitate the movement of drilling waste. The expansion means extend in the longitudinal direction of the blade to the front of the pilot blade in the drilling direction, whereby the end of the blade flushing channel on the face of the pilot blade is in the radial direction of the blade between the pilot blade and the expansion means, substantially preventing the pressure effect of the flushing flow on the borehole in the transverse direction of the pilot blade.

According to the invention, the discharge channel is made inclined, whereby the rotational torque cannot brake the passage of the piece through the flushing channel, but rather facilitates its flushing with air. If the discharge channel were to contract in the direction of rotation, the rotational torque would start to brake the passage of the piece, whereby air cannot flush the piece from the discharge channel and new pieces arriving in the wake would get stuck behind those passing in front,

O 25 even though they have already been ground into smaller pieces. The arrangement according to the invention ro ensures that only suitable pieces of rock 0 are flushed through the blade so that they do not brake, = and cannot get stuck, preventing the movement of other smaller drilling waste

N flushing particles and other debris up the borehole. io 30 The outlet channel widens from the pilot bit face to the rear of the bit,

N so that the flushing flow can be shifted to a smaller one all the time

N to the pressure plane from the pilot blade back. When the expansion means extend beyond the pilot blade face, the pressure effect of the flushing flow is directed laterally along the blade at the expansion plane.

lines and cannot expand the drill hole laterally.

In this case, the drilling device is adapted to remove mainly soil material that penetrates the closed area of the discharge channel between the pilot bit and the expansion means. 5

In the drilling device according to the invention, at least one outlet channel growing in the direction opposite to the direction of rotation of the blade and in the direction of flow towards the interior of the protective tube enables efficient removal of drilling waste from the blade area. At the same time, the pressure applied to the soil remains low when the total cross-sectional area of the return channel or channels directed behind the blade into the protective tube is larger than the total cross-sectional area of the blade flushing channel or channels directed towards the blade surface of the blade. In this case, the narrow blade flushing channel causes sufficient back pressure so that the flushing air of the drilling device is diverted to the blade return channel and the drilling device is flushed inside the protective tube without any back pressure from the soil. In a drilling rig, the outlet channel that grows in the opposite direction to the direction of rotation of the bit enables solids in the drilling waste to move as the bit rotates in the outlet channel towards the widest edge of the outlet channel, where they can freely move in the expanding outlet channel towards the interior of the casing.

O 25 Preferably there are 2 - 8 return channels. In this case the blade is ro easier to balance and a sufficiently large return flow 0 into the protective tube is obtained. x a ~~ Preferably there are 2 - 8 blade flushing channels. In this case io 30 the flushing of the blade surface of the blade is obtained symmetrically.

S

Preferably, there are 2 to 8 discharge channels. In this case, each blade flushing channel can be continued by a discharge channel and a blade flushing channel, whereby the flushing is symmetrical.

Preferably, the return channel is arranged between the pilot bit flushing channel and the inner space of the casing. In this context, when speaking of the casing, it should be understood that the welding shoe welded to the casing or the ring cutter connected to the casing also forms part of the casing in the sense that the casing and the welding shoe or the casing and the ring cutter together define the inner space into which the drilling waste and the pressurized flushing flow are directed.

Preferably, the exhaust channel is arranged as an extension of the blade flushing channel. This means that the compressed air flow coming from the blade flushing channel to the blade surface and flushing the blade surface is directed along the exhaust channel into the interior of the protective tube.

Preferably, the depth of each outlet channel increases by 100-150% in the direction opposite to the drilling direction in the width direction of the outlet channel. In this case, the outlet channel is large enough to allow even the largest solids in the drilling waste to be guided into the casing.

Preferably, the depth of each outlet channel increases along the entire length of the outlet channel in the direction of the blade's axis of rotation. In this case, — no back pressure is created in the outlet channel, which would make it difficult

O 25 removal of drilling waste and would cause 3 stress on the soil.

S

= Preferably the return channel and the blade flushing channel are arranged

N to branch from the flushing channel at essentially the same point. io 30 In this case, the smaller cross-sectional area of the blade flushing channel is

The back pressure generated by the nozzle controls the compressed air used for flushing.

N into the return duct and into the protective pipe.

Preferably, the flushing channel has an end wall into which the flushing

The channel ends in a pilot blade, at the end wall of which the return channel and blade flushing channel are connected to the flushing channel.

The end wall directs the flow even more efficiently into the return channel.

According to one embodiment, the discharge channel includes a straight part and an expanding part, and one return channel is connected to the discharge channel by the expanding part of the discharge channel. The discharge channel connecting to the expanding part captures the flow of drilling waste in the discharge channel, enhancing the removal of drilling waste.

According to one embodiment, the expanding part is uniformly expanding. In this case, it is simple to manufacture.

Preferably, the diameter of the pilot bit at the outlet channel decreases uniformly in the direction opposite to the drilling direction of the bit at the point where the return channel joins the outlet channel.

In other words, the outlet channel increases towards the center of the pilot bit as it goes in the opposite direction to the drilling direction at the point where the return channel joins the outlet channel. This results in a small flow resistance in the return direction of the flushing flow.

According to another embodiment, the exhaust channel is uniformly expanding along the entire length of the exhaust channel.

O 25 According to one embodiment, the expanding part is adapted to expand by 30-100% along its length in the direction of the axis of rotation of the blade of the expanding part.

Tr a ~~ Preferably, the total cross-sectional area of the return channel or channels is 20 - 80% larger than that of the blade flushing channel.

N or the total cross-sectional area of the blade flushing channels.

N In this case, the compressed air flow used for flushing is efficiently directed to the return channel and the compressed air flow to the blade flushing channel is smaller, reducing the effect of expanding the drill hole.

According to one embodiment, the expansion means is a ring blade.

The ring bit can be used to enlarge the drill hole made by the pilot bit in front of the retractable protective pipe, while the ring bit remains in the drill hole after drilling is complete.

According to another embodiment, the expansion means is a reamer. The reamer can be removed from the drill hole after drilling along with the pilot bit.

Preferably, the outlet channel is a groove made in the surface of the pilot blade.

This makes the exhaust channel easy to manufacture and the compressed air flowing through the exhaust channel simultaneously flushes the space between the blade and the protective tube.

Preferably, the arrangement includes a welding shoe for connecting the pipe to the blade for pulling the protective pipe into the borehole following the blade using the welding shoe.

Alternatively, the protective tube can also be fed into the drill hole using a method other than using a welding shoe.

Preferably, the blade flushing channel opens directly towards the soil. — This allows the compressed air used for flushing to flush

O 25 blade surface effectively. In other words, this means that when the compressed air flow leaves the blade flushing channel 0, it preferably impinges directly on the soil in the borehole and not on a separate surface belonging to the blade, as in the prior art.

N in solutions where the pressure on the soil is reduced by first impinging the compressed air flow on the blade and

N through it into the soil.

OF

Preferably, the outlet channel may be expanding in the radial direction of the blade as it goes from the blade surface towards the interior of the protective tube.

In other words, the outlet channel is deeper in the radial direction of the blade closer to the protective tube than in the vicinity of the blade surface.

In connection with the blade surface of the pilot blade, the depth of the outlet channel may be 3-15%, preferably 5-10% of the length of the outlet channel at the edge of the outlet channel that is first in the direction of rotation of the blade. In connection with the blade surface of the pilot blade, the depth of the outlet channel may be 15-30%, preferably 18-25% of the length of the outlet channel at the edge of the outlet channel that is last in the direction of rotation of the blade.

The depth of each outlet channel can increase by 100-150% in the radial direction of the blade's axis of rotation in the width direction of the outlet channel as it goes from the blade surface of the pilot blade to the interior of the protective tube.

Inside the protective tube, the depth of the outlet channel may be 6-25%, preferably 10-15%, of the length of the outlet channel at the edge of the outlet channel that is first in the direction of rotation of the blade.

Inside the protective tube, the depth of the outlet channel may be 30-50%, preferably 35-40%, of the length of the outlet channel at the edge of the outlet channel that is the last in the direction of rotation of the blade.

The purpose of the preferably multidirectional expansion of the exhaust channels is to ensure that the passage of the pressurized air flow supplied to the blade surface of the blade and through it — into the drill hole

There are no obstacles in the outlet channel O 25 , so that the compressed air flow flushing the blade surface ro can pass through the drilling bit 0 without expanding the borehole. x a ~~ Preferably, the width of the outlet channel is steadily increasing. In this case, stones loosened from the soil io 30 can be moved as the blade rotates

N towards the wider edge of the outlet channel and finally through it

N inside the protective tube.

Alternatively, the width of the exhaust duct can also be stepped. In this case, the step must be at the front of the protective pipe.

The invention is described in detail below with reference to the accompanying drawings illustrating some applications of the invention, in which

Figure 1 shows the entire drilling device according to the invention from the side,

Figure 2 shows a side view of the drill bit and impact device according to the invention,

Figure 3 shows a sectional view of the blade of the drilling device according to the invention from the side,

Figure 4 shows the pilot blade of the drill bit, separated from the direction of the blade surface,

Figure 5 shows the pilot bit of the drill bit separated from the side,

Figure 6a shows a blade according to the first embodiment of the drilling device, separated from the direction of the blade surface,

Figure 6b shows a blade according to another embodiment of the drilling device, separated from the direction of the blade surface,

Figure 7 shows the pilot bit of the drill bit separated — viewed from the side with the welding shoe,

O 25 Figure 8 shows the drill bit of the drilling device axonometrically ro depicted separately from the pilot bit. 2 = Figure 1 shows the drill bit 100 according to the invention in its entirety

N as a woman. The drilling rig 100 can be moved, for example, supported by a frame with a track and a tower, to which the

N drilling device 100 is supported. The bit 5.9 of drilling device 100 is rotated

N by means of a rotating device 50 via a drill rod 52. Pressurized flushing air is supplied to the blade 5,9 from compressed air means 54. The drilling device according to the invention is intended for pipe-

for putty drilling, in which a protective tube 3 is fed behind the blade 5.9, which is shown in Figure 1 in shortened form for simplicity. The impact device, rotation device, compressed air means and other peripheral equipment of the drilling device may be completely in accordance with the state of the art. When drilling with the drilling device according to the invention, the blade 5.9 rotates while the protective tube follows the blade 5.9 without rotation.

According to Figure 2, the drilling device 100 according to the invention includes, according to the prior art, an impact device 14, preferably comprising a piston 56, which strikes and rotates a blade 5,9, which drills 102 boreholes 22 in the soil, pulling a protective tube 3 behind it.

According to Figure 3, the drilling device 100 comprises a multi-part blade 5,9, to which a flushing air flow is introduced via the impact device 14 along a first flow channel (not shown). The blade 5,9 preferably includes a pilot blade 9 and expansion means 5. The protective tube 3 introduced after the blade 5,9 includes a front part 18 and an interior space 20 is formed inside the protective tube 3 between the protective tube 3 and the shaft of the blade 5,9. The protective tube 3 is connected to the blade 5,9 from its front part 18 by means of an arrangement 24. The arrangement 24 is preferably a welding shoe 11, by means of which the protective tube 3 is connected to the outer edge of the pilot blade 9. The welding shoe is a shoulder that pulls the protective tube into the ground and its use is not necessary if the feeding device is capable of

O 25, for example, to push the protective tube into the resulting drill hole 3 behind the blade.

S

= The pilot bit 9 in the drilling device according to the invention includes 100

N blade surface 12 and flushing channel 4 for conducting flushing air flow io 30 from the impact device 14 through the first flow channel

N for said blade 5.9. The impact device 14 is preferably immediately

N in connection with the shaft of the pilot blade 9. The flushing channel 4 preferably has an end wall 30, in connection with which the flushing channel 4 preferably branches forward into blade flushing channels 10 leading to the blade surface 12 and away from the blade surface 12 towards the interior space 20 of the protective tube 3 into return channels 1 leading. The return channels 1 are arranged between the flushing channel 4 and the interior space 20 of the protective tube 3 in order to conduct the flushing air flow of the pilot blade 9 part directly into the interior space 20 of the protective tube 3 in order to flush it. The blade flushing channels 10 are in turn arranged to conduct the compressed air used for flushing from the flushing channel 4 to the blade surface 12 of the pilot blade 9 in order to flush the blade surface 12 from drilling debris generated when the pilot blade 9 and the expansion means 5 rotate in the borehole 22 while striking. The combined cross-sectional area of the return channels 1 is larger than the combined cross-sectional area of the blade flushing channels 10, whereby the blade flushing channels 10 form a sufficiently large flow resistance to direct the compressed air flow directly along the return channels 1 to the inner space 20 of the protective tube 3 for flushing it without back pressure caused by the soil. With this solution, the compressed air flow coming from the flushing channel 4 is divided so that at least the majority of the flow is turned back along the return channels 1 to the inner space 20 of the protective tube 3 and a smaller part is directed to the blade surface 12 of the pilot blade 9 to flush the blade surface 12.

Although the use of multiple return channels, blade flushing channels, and exhaust channels has been discussed in connection with the detailed description of the invention, this is only a preferred embodiment of the invention. It will be

It is understood that the drilling device according to the invention can also be implemented using only one return channel, one blade flushing channel and one exhaust channel. The compressed air flow directed to the blade surface 12 of the pilot blade 9 through the blade flushing channels 10 is directed to the blade flushing channels 10

N continuous discharge channels 7 along the protective tube 3

N into, preferably first using the radially inclined channel 7.1 of the blade 5,9 to conduct the compressed air towards the outer edge of the pilot blade 9 and from there along the straight part 26 belonging to the discharge channel 7 to the expanding part 8 belonging to the discharge channel 7. In other words, the discharge channels 7 are arranged in the pilot blade 9 as an extension of the blade flushing channels 10 for conducting the compressed air into the interior 20 of the protective tube 3. The discharge channels 7 are arranged to expand in cross-sectional area in the flow direction when going from the blade surface 12 towards the interior 20 of the protective tube 3. Preferably, the expansion takes place in the radial direction of the axis of rotation of the blade 5,9 in accordance with Figure 3. In other words, the closer one is to the protective tube 3, the deeper the discharge channels 7 are.

Each discharge channel 7 has, as shown in Figure 4, a depth d in the radial direction of the blade 5.9 and a width 1 between the edges 44 belonging to the discharge channel 7. According to the invention, the depth of each discharge channel 7 increases in the direction opposite to the direction of rotation of the blade 5.9 in the width direction of the discharge channel 7 in order to facilitate the movement of drilling waste. The depth of each discharge channel 7 can increase by 100-150% in the direction opposite to the drilling direction in the width direction of the discharge channel 7. In connection with the blade surface 12 of the pilot blade 9, the depth d of the discharge channel 7 can be 3-15%, preferably 5-10% of the length 1 of the discharge channel 7 at the edge of the discharge channel 7 that is first in the direction of rotation of the blade 5.9.

In connection with the cutting surface 12 of the pilot blade 9, the depth d of the outlet channel 7 can be 15-30%, preferably 18-25% of the length 1 of the outlet channel 7 at the edge of the outlet channel 7 that is 5.9 of the blade.

O 25 in the direction of rotation as the latter. In the drilling device according to the invention, the blade 5,9 is rotated so that the shallower edge of the outlet channel 7 0 meets the soil first and the deeper edge as the latter, i.e. the blade rotates clockwise when viewed

N blades from top to bottom. In Figure 4, the correct direction of rotation is shown by reference number 42.

S

The depth of each outlet channel 7 may increase by 100-150% in the radial direction of the blade rotation axis in the width direction of the outlet channel 7 as the pilot blade 9 passes from the blade surface 12 into the interior of the protective tube 3. Inside the protective tube 3, the depth d of the outlet channel 7 may be 6-25%, preferably 10-15% of the length of the outlet channel 7 at the edge 44 of the outlet channel 7 that is first in the direction of rotation of the blade 5,9. Inside the protective tube 3, the depth d of the outlet channel 7 may be 30-50%, preferably 35-40% of the length of the outlet channel 7 at the edge 1 of the outlet channel 7 that is last in the direction of rotation of the blade 5,9. The purpose of the preferably multidirectional expansion of the exhaust channels 7 is to ensure that there are no obstacles to the passage of the pressurized air flow fed to the blade surface 12 of the blade 5,9 and through it to the drill hole 22 in the exhaust channel 7, whereby the pressurized air flow flushing the blade surface 12 can pass, displacing drilling waste without expanding the drill hole 22.

Figure 5 shows how the return channels 1 connect to the outlet channel 7, preferably at its expanding part 8 and preferably close to the end of the outlet channel 7 that is in the interior 20 of the protective tube 3 according to Figure 3. In Figure 5, reference number 36 shows a groove for bayonet locking of the ring blade.

The drilling device according to the invention can be used to drill soil and rock, and the flushing of the drilling device inside the pipe element works without any back pressure from the soil, because the combined cross-sectional area of the return channels connected to the flushing channel is larger.

O 25 than the common cross-sectional area of the flow channels ro directed from the flushing channel to the bit. The exhaust channels 7 are formed as shown in Figure 0 3 to expand backwards (direction 2), so they do not = try to force the flow of flushing air in the drilling direction (direction

N 6), which the back pressure created by the soil 102 must overcome to enable flushing, as in conventional drilling systems

With the Elemex and Stable-X systems. Since the exhaust channels 7 are

N is formed to expand backwards, no harmful air discharges into the soil are possible. Furthermore, due to the structure of the pilot bit of the drilling device, the drilling device practically removes only the material that penetrates the closed area of the discharge channel and thus eliminates the overflushing phenomenon, which is also called mammothing. Thus, with the drilling device according to the invention, it is possible to drill large piles very close to potentially damaged targets, because pressure shocks are not possible, and the system does not overflush the borehole.

Preferably, the pilot bit of the drilling device according to the invention has at least two exhaust channels, but there may also be three or even four if the pilot bit has a large diameter.

There is preferably a corresponding number of return channels and blade rinsing channels each as there are discharge channels, i.e. if there are two discharge channels, then there are two return channels and two blade rinsing channels.

According to Figures 6a and 6b, in connection with the pilot bit 9, a ring bit 28 according to Figure 6a or a reamer bit 32 according to Figure 6b can be used as expansion means 5. These are alternative solutions for expansion means 5 to be used with the pilot bit 9. When the casing has been drilled into the rock or to the target level, the pilot bit is rotated in the opposite direction to the direction used during drilling. In this case, the pilot bit 6 is released from the arrangement, which — can also be called a ground shoe, by means of a bayonet attachment, and can be lifted up

O 25 from the borehole. The arrangement 24 and the expansion means 5, if the expansion means 5 are the ring bit 28 according to Figure 6a, remain in the borehole 22. If the expansion means are the reamer bit 32 according to Figure 6b, the reamer bit 32 can also be lifted out.

N from the borehole at the end of drilling. io 30

N Figure 7 shows a drilling device 100 according to the invention.

N pilot blade 9 with welding shoe 11 acting as adapter 24 for securing protective tube 3. Reference number 34 shows the blade pieces in Figures 3 and 6a - 8 and reference number 33 shows the recesses of the blade pieces 34, which are visible in Figures 4 and 5. Figures 5 and 8 show an additional return channel 38, which can be made between the inner space 20 of protective tube 3 and the flushing channel 4 to enhance the return flow.

The diameter of the flushing channel 4 may be, for example, 30 mm, whereby the diameter of the blade flushing channels may be 9 mm. The drilling device according to the invention may be used in drilling underground pipes for forming bored piles to a depth of 2-100 m, preferably up to a depth of 5-m.

OF

O

OF

LÖ

<Q wn

O

I a a

R

OF

O

0

OF

O

OF

Claims (15)

PATENT CLAIMS 1. A drilling device (100) for drilling a borehole (22) in soil (102), the drilling device (100) comprising a multi-part blade (5,9), a percussion device (14) connected to the blade (5,9) for imparting a percussion motion to the blade (5,9), a rotating device (50) for rotating the blade (5,9), a first flow channel connected to the percussion device (14) for conducting a flow of pressurized working air to said percussion device (14) for operating the percussion device (14), a protective tube (3) comprising a front part (18) and an interior space (20) adapted to be pulled into the borehole (22) to be drilled during drilling, and an arrangement (24) between the front part (18) of the protective tube (3) and the blade (5,9) for pulling the protective tube (3) into the borehole (22) following the blade (5,9) by means of a transmission, wherein the blade (5,9) includes a pilot blade (9) and expansion means (5), the pilot blade (9) comprising - a blade surface (12), - a flushing channel (4) formed in said pilot blade (9) for conducting a flushing air flow from the impact device (14) to said blade (5,9), - at least one return channel (1) arranged in the pilot blade (9) for conducting a part of the flushing air flow directly to the interior (20) of the protective tube — (3), and said return channels (1) branches O 25 from the flushing channel (4), ro - at least one blade flushing channel (10) arranged in 0 the pilot blade (9) between the flushing channel (4) and the pilot blade (9) = blade surface (12) for conducting a part of the flushing air flow to the blade surface (12) for flushing the blade surface (12), where io 30 of the return channel (1) or the total cross-sectional area of the return channels (1) is greater than the total cross-sectional area of the blade flushing channel (10) or the N blade flushing channels (10), and - at least one outlet channel (7) arranged in the pilot blade (9) between the blade surface (12) and the interior space (20) of the protective tube (3) for conducting compressed air to the interior space (20) of the protective tube (3), which outlet channel (7) is parallel to the axis of rotation of the blade (5,9) and is arranged in the flow direction to expand in cross-sectional area as it goes from the blade surface (12) towards the interior space (20) of the protective tube (3), wherein the outlet channel (7) has longitudinal edges (44) of the blade (5,9), a radial depth of the blade (5,9) and a width between said edges (44), and the depth of the outlet channel (7) is increasing in the width direction of the outlet channel (7) (5,9) to facilitate the movement of the drilling extension when going in the direction opposite to the direction of rotation, characterized in that the expansion means (5) extend in the longitudinal direction of the blade (5,9) to the front side of the pilot blade (9) in the drilling direction, whereby the end of the blade flushing channel (10) on the face of the pilot blade (9) is in the radial direction of the blade (5,9) between the pilot blade (9) and the expansion means (5), substantially preventing the pressure effect of the flushing flow on the borehole (22) in the transverse direction of the pilot blade (9). 2. A drilling device according to claim 1, characterized in that the depth of the outlet channel (7) increases by 100-150% in the direction opposite to the drilling direction in the width direction of the outlet channel (7). 3. A drilling device according to claim 1 or 2, - characterized in that the depth of the outlet channel (7) increases along the entire length of the outlet channel (7) in the direction of the axis of rotation of the blade (5,9). 8 0 4. A drilling device according to any one of claims 1 to 3, characterized in that said return channel (1) and said blade flushing channel (10) are arranged to branch off from the flushing channel (4) at substantially the same point. S 5. A drilling device according to claim 4, characterized in that the flushing channel (4) has an end wall (30), where the flushing channel (4) ends in a pilot bit (9), the end wall of which The return channel (1) and the blade flushing channel (10) mentioned in connection with (30) are connected to the flushing channel (4). 6. A drilling device according to any one of claims 1 to 5, characterized in that the outlet channel (7) includes a straight part (26) and an expanding part (8), and one said return channel (1) is connected to the outlet channel (7) by an expanding part (8) of the outlet channel (7). 7. A drilling device according to claim 6, characterized in that said expanding part (8) is uniformly expanding. 8. A drilling device according to claim 6 or 7, characterized in that said expanding part (8) is adapted to expand by 30 - 100% along its length parallel to the axis of rotation of the blade (5,9) of the expanding part (8). 9. A drilling device according to any one of claims 1 to 8, characterized in that the total cross-sectional area of the return channel (1) or return channels (1) is 20 to 80% larger than the total cross-sectional area of the blade flushing channel (10) or blade flushing channels (10). 10. A drilling device according to any one of claims 1 to 9, - characterized in that said expansion means (5) are O 25 ring bit (28). 3 O 11. A drilling device according to any one of claims 1 to 9, = characterized in that said expansion means (5) are a drill bit (32). © 30 O N 12. A drilling device according to any one of claims 1 to 11, characterized in that the diameter of the pilot bit (9) at the outlet channel (7) decreases uniformly in a direction opposite to the drilling direction of the bit (5,9) at the point where the return channel (1) joins the outlet channel (7). 13. A drilling device according to any one of claims 1 to 12, characterized in that the arrangement (24) includes a welding shoe (11) for connecting the protective tube (3) to the blade (5,9). 14. A drilling device according to any one of claims 1 to 13, characterized in that said blade flushing channel (10) opens directly towards the soil (102). 15. A drilling device according to any one of claims 1 to 14, characterized in that said outlet channel (7) is widening in the radial direction of the blade (5,9) as it goes from the blade surface (12) towards the interior (20) of the protective tube (3). N O N 0 <Q wn O I jami a N N O 0 N O N