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Title:
METHOD IN DOWN-THE-HOLE DRILLING AND A DOWN-THE-HOLE DRILLING DEVICE
Document Type and Number:
WIPO Patent Application WO/2017/089647
Kind Code:
A1
Abstract:
The invention relates to a method in down-the-hole drilling and a down-the-hole drilling device, being meant for drilling a hole with and a casing pipe (2). The drilling device comprises in its drilling head (I) : a drilling arrangement having first drilling means (4) for drilling a center hole and second drilling means (5) for reaming the center hole for the casing pipe (2); and a flushing flow arrangement (6) for feeding of a pressurized flushing medium onto a drilling surface (P) of the drilling arrangement by a feed flow arrangement (6a). In the method the flushing medium for drilling is being led by the feed flow arrangement (6a) onto the drilling surface (PI) of the first drilling means (4). The feed flow arrangement (6a) is prevented from getting clogged with soil substance, due to releasing the pressure of the flushing medium, by one or more feed channels (6a') of the feed flow arrangement (6a), having a cross section that expands toward the drilling surface (PI) of the first drilling means (4).

Inventors:
GYLLING KAI (FI)
Application Number:
PCT/FI2016/050767
Publication Date:
June 01, 2017
Filing Date:
November 02, 2016
Export Citation:
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Assignee:
OY ATLAS COPCO ROTEX AB (FI)
International Classes:
E21B10/61; E21B10/60; E21B7/20; E21B10/18; E21B10/26; E21B10/38; E21B10/62; E21B10/64
Domestic Patent References:
WO2010070190A12010-06-24
WO1998020229A11998-05-14
WO1992011436A11992-07-09
WO2002081856A12002-10-17
WO2016128607A12016-08-18
Attorney, Agent or Firm:
KANGASMÄKI, Reijo (Tampere, FI)
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Claims:
Claims :

1. Method in down-the-hole drilling to be performed by a down-the-hole drilling device (1) with a casing pipe (2) , wherein the drilling device comprises in its drilling head (I) : a drilling arrangement having first drilling means (4) for drilling a center hole and second drilling means (5) for reaming the center hole for the casing pipe (2) ; and a flushing flow arrangement (6) for feeding of a pressurized flushing medium onto a drilling surface (P) of the drilling arrangement by a feed flow arrangement (6a) and for discharging the same from the drilling surface (P) together with drilling waste backwards with respect to the drilling direction by an exhaust flow arrangement (6b), wherein the casing pipe (2) is arranged to be pulled into the hole to be drilled by power influence directed thereto from the drilling arrangement, such as the first and/or the second drilling means (4, 5), and whereby in the method the flushing medium for drilling is being led by the feed flow arrangement (6a) onto the drilling surface (PI) of the first drilling means (4), characterized in that, the feed flow arrangement (6a) is prevented from getting clogged with soil substance, due to releasing the pressure of the flushing medium, by one or more feed channels (6a') of the feed flow arrangement (6a), having a cross section that expands toward the drilling surface (PI) of the first drilling means ( 4 ) .

2. Method according to claim 1, wherein the drilling head (I) of the drilling device (1) consists of a first frame part (4a) and a second frame part (5a) , wherein the drilling surfaces (PI, P2) formed of end surfaces of the frame parts are provided with drilling organs of the first and the second drilling means (4, 5) , such as an integrated drilling part, separate drilling pieces, bits or like, wherein the essentially rotationally symmetrical first and second drilling means (4, 5) are coupled with each other on the first hand at least during a drilling situation in a power transmitting manner by means of a coupling arrangement in order to carry out co-operation thereof for a rotational motion, a feeding motion and/or a hammering motion and on the other hand removably in order to enable removal of the first drilling means (4) from a drilled hole, wherein the drilling device is provided with a casing shoe (8) for pulling the casing pipe (2) into the hole by means of a shoulder arrangement (L) enabling an independent rotational movement of the casing pipe (2) and the drilling device (1) with respect to each other and restricting mutual longitudinal (s) movement thereof, wherein the exhaust flow arrangement (6b) comprises one or more longitudinal (s) return flow channels (6b') on the side surface of the first drilling means (4) for removing drilling waste between the first and second drilling means (4, 5) inside the casing pipe (2), and whereby in the method the flushing medium is being led inside the first frame part (4a) in a centric duct (6a") and delivered therefrom radially through one or more feed channels (6a') onto the drilling surface (PI) of the first drilling means (4), characterized in that, getting clogged of the feed flow arrangement (6a) is prevented by the one or more feed channels (6a')/ the cross section of which expand conically from a delivery opening (X) thereof in the centric duct (6a") toward a feed opening (Y) thereof on the drilling surface (PI) of the first drilling means (4) .

3. A down-the-hole drilling device for drilling a hole with a casing pipe (2), wherein the drilling device (1) comprises in its drilling head (I) : a drilling arrangement having first drilling means (4) for drilling a center hole and second drilling means (5) for reaming the center hole for the casing pipe (2) ; and a flushing flow arrangement (6) for feeding of a pressurized flushing medium onto a drilling surface (P) of the drilling arrangement by a feed flow arrangement (6a) and for discharging the same from the drilling surface (P) together with drilling waste backwards with respect to the drilling direction by an exhaust flow arrangement (6b), wherein the casing pipe (2) is arranged to be pulled into the hole to be drilled by power influence directed thereto from the drilling arrangement, such as the first and/or the second drilling means (4, 5), and whereby the feed flow arrangement (6a) is arranged to lead the flushing medium for drilling onto the drilling surface (PI) of the first drilling means (4), characterized in that, one or more feed channels (6a') of the feed flow arrangement (6a) have a cross section that expands toward the drilling surface (PI) of the first drilling means (4) .

4. A down-the-hole drilling device according to claim 3, wherein the drilling head (I) of the drilling device (1) consists of a first frame part (4a) and a second frame part (5a) , wherein the drilling surfaces (PI, P2) formed of end surfaces of the frame parts are provided with drilling organs of the first and the second drilling means (4, 5), such as an integrated drilling part, separate drilling pieces, bits or like, wherein the essentially rotationally symmetrical first and second drilling means (4, 5) are coupled with each other on the first hand at least during a drilling situation in a power transmitting manner by means of a coupling arrangement in order to carry out co-operation thereof for a rotational motion, a feeding motion and/or a hammering motion and on the other hand removably in order to enable removal of the first drilling means (4) from a drilled hole, wherein the drilling device is provided with a casing shoe (8) for pulling the casing pipe (2) into the hole by means of a shoulder arrangement (L) enabling an independent rotational movement of the casing pipe (2) and the drilling device (1) with respect to each other and restricting mutual longitudinal (s) movement thereof, wherein the exhaust flow arrangement (6b) comprises one or more longitudinal (s) return flow channels (6b') on the side surface of the first drilling means (4) for removing drilling waste between the first and second drilling means (4, 5) inside the casing pipe (2), and whereby the first frame part (4a) comprises a centric duct (6a") for delivering of the flushing medium therefrom radially through one or more feed channels (6a') onto the drilling surface (PI) of the first drilling means (4), characterized in that, the cross section of the one or more feed channels (6a') of the feed flow arrangement (6a) expands from a delivery opening (X) thereof in the centric duct (6a") toward a feed opening (Y) thereof on the drilling surface (PI) of the first drilling means (4) .

5. A down-the-hole drilling device according to claim 3 or 4, characterized in that, the cross section of the one or more feed channels (6a') of the feed flow arrangement (6a) expands conically in one plane aligned with longitudinal axis (t) thereof. 6. A down-the-hole drilling device according to claim 3 or 4, characterized in that, the cross section of the one or more feed channels (6a') of the feed flow arrangement (6a) expands conically in two crosswise planes aligned with longitudinal axis (t) thereof.

7. A down-the-hole drilling device according to any of the preceding claim 3-5, characterized in that, the feed flow arrangement (6a) comprises one or more flushing channels (6al) on the drilling surface (PI) of the first drilling means (4) passing from a feed opening (Y) of the feed channel (6a') of the feed flow arrangement (6a) toward the outer periphery of the first drilling means (4) . 8. Down-the-hole drilling device according to any of the preceding claims 1-7, characterized in that, the feed flow arrangement (6a) comprises on a bottom of one or more flushing channels (6al) a supplementary flushing groove (6a2) passing from one or more feed openings (Y) of the feed flow arrangement (6a) toward the outer periphery of the first drilling means (4) .

9. A down-the-hole drilling device according to claims 7 or 8, characterized in that, the one or more flushing channels (6al) and/or supplementary flushing grooves (6a2) get wider in longitudinal direction (r) thereof toward the outer periphery of the first drilling means ( 4 ) . 10. A down-the-hole drilling device according to any of the preceding claim 3-9, characterized in that, the one or more flushing channels (6al) and/or supplementary flushing grooves (6a2) are connected to a return flow channel (6b') of the exhaust flow arrangement (6b) on the side surface of the first drilling means (4) with a backward sloping bottom (6al', 6a2' ) .

Description:
Method in down-the-hole drilling and a down-the-hole drilling device

The invention relates to a method in down-the-hole drilling and a down-the-hole drilling device according to the preambles of the independent claims directed thereto .

A way to carry out earth drilling in a developed manner with respect to traditional technique is known e.g. from Finnish Patent No. 95618. A drilling head in a drilling unit of the drilling apparatus that exists inside a casing pipe or in other words a so called earth pipe or casing pipe presented in this patent is formed of a first frame part and an annular second frame part, the drilling surfaces of which being provided with drilling organs, such as drill bits or like, of the first and second drilling means or in other words of a center drill or a pilot and a reaming drill or a reamer. In this solution the first frame part forming the pilot, is being released from the second frame part forming the reamer, in order to pull the same alone off from a drilled hole after the drilling situation.

The solution in question is provided with an arrangement, which locks the said drilling means together for a drilling situation unrotatively in respect with each other and in both directions longitudinally, in which context as an advantageous embodiment a bayonet coupling has been used.

After many years of experience, the drilling device according to the above mentioned patent has proved very efficient in practise and also very easy to be adjusted for different kinds of drilling purposes . E.g. regarding a drilling device of this type, there has, however, been found possibilities for making its functioning more efficient particularly in drilling of different kinds of soils. In this context modifications of the first drilling means i.e. the pilot have been developed and tested, wherein e.g. a drill bit with a flushing flow arrangement has been used, in which the feed channels of a feed flow arrangement for flushing medium at least partly end up on the drilling surface of the pilot at flushing channels that exist in the longitudinal direction of the drilling device essentially lower than the lowest part of the actual drilling surface of the pilot. Furthermore the flushing channel on the drilling surface of the pilot may also get wider in longitudinal direction thereof towards the outer periphery of the pilot in order to make flushing on the drilling surface more efficient.

On the one hand, despite the above modifications, an adequate result has not been achieved under all circumstances particularly due to clogging of the drilling surface e.g. particularly in drilling clayey soil or soil comprising soft sand. On the other hand, under very soft conditions, like drilling wet clay and sand with high water content (e.g. under ground water level) , the soil with drilling waste may easily enter excessively inside the drill bit when adding casing and drill pipes. This happens because the pressure inside the pipes and the drill bit drops, when the drill pipe thread is opened. Due to the pressure being higher down in the ground than inside the drill bit and pipes, and due to the soil being in fluidious state (liquid form) , the higher pressure in the soil pushes the soil substance inside the drill bit through the drilling surface of the drilling device. Sometimes the soil substance will rise all the way into the hammer regardless of whether the check valve of the hammer works correctly or not. In case the above will take place, all the drilling equipment will need to be taken out of the hole, broken into pieces and cleaned up. It is a matter of fact that in practice a blockage of this kind will not open despite a high pressure of the flushing medium will be applied. The cleaning operations related to this kind of situations are time consuming thus causing unnecessary delays and extra costs in drilling. It is an aim of the method in down-the-hole drilling and the down-the-hole drilling device according to the present invention to bring about a decisive improvement particularly in the problems described above in drilling different types of soil and thus to raise essentially the level of prior art. In order to carry out this aim, the method in down-the-hole drilling and the down-the-hole drilling device according to the invention are mainly characterized by what has been presented in the characterizing parts of the independent claims directed thereto.

As the most important advantages of the method in down-the-hole drilling and the down-the-hole drilling device according to the invention may be mentioned simplicity of constructions and operating principle enabled by the same. The above are first of all thanks to the fact that the applicability of the drilling device, being found profitable in practice as such, can be further improved by making possible drilling with the same drilling device construction that doesn't get clogged when adding casings and drill pipes and that has an efficiently operating drilling face for a wide variety of soil types. Thanks to the invention, by virtue of the one or more expanding feed channels of the feed flow arrangement on the other hand entering of soil substance particularly inside the deeper parts of the feed flow arrangement of the flushing medium is efficiently prevented. By utilizing channels with an expanding cross section in longitudinal direction thereof in delivering flushing medium onto the drilling surface of the first drilling means, a blockage of soil substance will be formed in a controlled manner only in the feed channels. Such blockages can be opened without dismantling the whole drilling device simply by switching on again the pressure of the flushing medium thanks to the blockages being formed only in the feed channels very close to the drilling surface. On the other hand by utilizing furthermore advantageously flushing channels on the drilling surface of the pilot and furthermore possibly supplementary flushing grooves on the bottom of the flushing channels, more space is left for the soil substance facing the drilling surface of the drilling device. In this context as a further advantageous embodiment, a supplementary flushing groove e.g. having a constant width from an opening of the feed channel to the outer periphery of the pilot can be exploited. The drilling efficiency can be further enhanced by exploiting a supplementary flushing groove having a cross section that at least partly gets larger in its longitudinal direction. The removing of the drilling waste through the return flow channels on the side surface of the pilot can be made furthermore even more efficient with backward sloping bottoms of the flushing channels and/or the supplementary flushing grooves.

By virtue of the invention, the functioning of the drilling device may be enhanced also by eliminating/retarding wear thus increasing the life time of the drilling device. Thanks to the invention also the speed of drilling can be increased with respect to traditional constructions thanks to avoiding clogging of the drilling device, whereby also both air and water can be used as the flushing medium.

Other advantageous embodiments of the method in down-the-hole drilling and the down-the-hole drilling device according to the invention have been presented in the dependent claims directed thereto.

In the following description the invention is being illustrated in detail with reference to the appended drawings, in which in figures la-lc

are shown a perspective view, a frontal view and a longitudinal cross section of an advantageous down-the-hole drilling device according to the invention with a casing shoe, in figures 2a-2c

are shown a perspective view, a frontal view and a longitudinal cross section of a second alternative down-the-hole drilling device with a casing shoe, in figures 3a-3c

are shown a perspective view, a frontal view and a longitudinal cross section of a third alternative down-the-hole drilling device with a casing shoe and having a simpler drilling surface of the pilot, and in figures 4a-4c

are shown a perspective view, a frontal view and a longitudinal cross section of a fourth alternative down-the-hole drilling device with a casing shoe and having a simpler drilling surface of the pilot.

The invention relates to method in down-the-hole drilling to be performed by a down-the-hole drilling device 1 with a casing pipe 2, wherein the drilling device comprises in its drilling head I: a drilling arrangement having first drilling means 4 for drilling a center hole and second drilling means 5 for reaming the center hole for the casing pipe 2; and a flushing flow arrangement 6 for feeding of a pressurized flushing medium onto a drilling surface P of the drilling arrangement by a feed flow arrangement 6a and for discharging the same from the drilling surface P together with drilling waste backwards with respect to the drilling direction by an exhaust flow arrangement 6b. The casing pipe 2 is arranged to be pulled into the hole to be drilled by power influence directed thereto from the drilling device 1, such as the first and/or the second drilling means 4, 5. In the method the flushing medium for drilling is being led by the feed flow arrangement 6a onto the drilling surface PI of the first drilling means 4. The feed flow arrangement 6a is prevented from getting clogged with soil substance, due to releasing the pressure of the flushing medium, by one or more feed channels 6a' of the feed flow arrangement 6a, having a cross section that expands toward the drilling surface PI of the first drilling means 4. It is preferred for the method according to the present invention to work in a good way that the cross section of the one or more feed channels 6a' grows constantly from start to finish. As an advantageous embodiment of the method according to the invention, the drilling head I of the drilling device 1 consists of a first frame part 4a and a second frame part 5a, wherein the drilling surfaces PI, P2 formed of end surfaces of the frame parts are provided with drilling organs of the first and the second drilling means 4, 5, such as an integrated drilling part , separate drilling pieces, bits or like. The essentially rotationally symmetrical first and second drilling means 4, 5 are coupled with each other on the first hand at least during a drilling situation in a power transmitting manner by means of a coupling arrangement in order to carry out co-operation thereof for a rotational motion, a feeding motion and/or a hammering motion and on the other hand removably in order to enable removal of the first drilling means 4 from a drilled hole . The drilling devices according to the drawings are provided furthermore (but not necessarily) with a casing shoe 8 for pulling the casing pipe 2 into the hole by means of a shoulder arrangement L enabling an independent rotational movement of the casing pipe 2 and the drilling device 1 with respect to each other and restricting mutual longitudinal s movement thereof. The exhaust flow arrangement 6b comprises one or more longitudinal s return flow channels 6b' on the side surface of the first drilling means 4 for removing drilling waste between the first and second drilling means 4, 5 inside the casing pipe 2. In the method the flushing medium is being led inside the first frame part 4a in a centric duct 6a" and delivered therefrom radially through one or more feed channels 6a' onto the drilling surface PI of the first drilling means 4. Getting clogged of the feed flow arrangement 6a is prevented by the one or more feed channels 6a' , the cross section of which expand according to figures lc and 2c conically from a delivery opening X thereof in the centric duct 6a" toward a feed opening Y thereof on the drilling surface PI of the first drilling means 4.

The invention also relates to a down-the-hole drilling device for drilling a hole with a casing pipe 2, wherein the drilling device 1 comprises in its drilling head I: a drilling arrangement having first drilling means

4 for drilling a center hole and second drilling means

5 for reaming the center hole for the casing pipe 2 ; and a flushing flow arrangement 6 for feeding of a pressurized flushing medium onto a drilling surface P of the drilling arrangement by a feed flow arrangement 6a and for discharging the same from the drilling surface P together with drilling waste backwards with respect to the drilling direction by an exhaust flow arrangement 6b. The casing pipe 2 is arranged to be pulled into the hole to be drilled by power influence directed thereto from the drilling device 1, such as the first and/or the second drilling means 4, 5. The feed flow arrangement 6a is arranged to lead the flushing medium for drilling onto the drilling surface PI of the first drilling means 4. With reference particularly to figures lc and 2c one or more feed channels 6a' of the feed flow arrangement 6a have a cross section that expands toward the drilling surface PI of the first drilling means 4.

As an advantageous embodiment of the down-the-hole drilling device according to the invention, as shown in the drawings the drilling head I of the drilling device 1 consists of a first frame part 4a and a second frame part 5a, wherein the drilling surfaces PI, P2 formed of end surfaces of the frame parts are provided with drilling organs of the first and the second drilling means 4, 5, such as an integrated drilling part , separate drilling pieces, bits or like. The essentially rotationally symmetrical first and second drilling means 4, 5 are coupled with each other on the first hand at least during a drilling situation in a power transmitting manner and advantageously in a restricted manner regarding mutual movement thereof in the longitudinal direction s by means of a coupling arrangement, such as a bayonet coupling or the like, in order to carry out co-operation thereof for a rotational motion, a feeding motion and/or a hammering motion and on the other hand removably in order to enable removal of the first drilling means 4 from a drilled hole.

The drilling devices shown in the drawings are provided with a casing shoe 8 for pulling the casing pipe 2 into the hole by means of a shoulder arrangement L enabling an independent rotational movement of the casing pipe 2 and the drilling device 1 with respect to each other and restricting mutual longitudinal s movement thereof. The exhaust flow arrangement 6b comprises one or more longitudinal s return flow channels 6b' on the side surface of the first drilling means 4 for removing drilling waste between the first and second drilling means 4, 5 inside the casing pipe 2. According to the advantageous embodiments shown in the drawings, the first frame part 4a comprises a centric duct 6a" for delivering of the flushing medium therefrom radially through one or more feed channels 6a' onto the drilling surface PI of the first drilling means 4. With reference particularly to figures lc and 2c, the cross section of the one or more feed channels 6a' of the feed flow arrangement 6a expands from a delivery opening X thereof in the centric duct 6a" toward a feed opening Y thereof on the drilling surface PI of the first drilling means 4.

As an advantageous embodiment of the down-the-hole drilling device according to the invention, the cross section of the one or more feed channels 6a' of the feed flow arrangement 6a expands as shown in figures 2a - 2c and 4a - 4c conically in one plane aligned with longitudinal axis t thereof.

As a furthermore advantageous embodiment of the down-the-hole drilling device according to the invention, the cross section of the one or more feed channels 6a' of the feed flow arrangement 6a expands as shown in figures la - lc and 3a - 3c conically in two crosswise planes aligned with longitudinal axis t thereof .

In the above by the wording "conical" is meant that the shape and size of the one or more feed channels gets larger preferably constantly from start to finish e.g. as shown in figures lc, 2c, 3c and 4c. So, the shape of the one or more feed channels 6a' on the drilling surface PI is, when viewed in a crosswise plane with respect to the longitudinal direction s of the drilling device, e.g. elongated (figs. 2b and 4b) or circular (figs, lb and 3b) . Naturally the shape of the channels may be elliptical, rectangular, triangular or of whatever shape.

As a furthermore advantageous embodiment of the down-the-hole drilling device according to the invention, particularly with reference to figures la, lb and 2a, 2b, the feed flow arrangement 6a comprises one or more flushing channels 6al on the drilling surface PI of the first drilling means 4 passing from a feed opening Y of the feed channel 6a' of the feed flow arrangement 6a toward the outer periphery of the first drilling means 4. In this context, as a furthermore advantageous embodiment of the down-the-hole drilling device according to the invention, the feed flow arrangement 6a comprises on a bottom of one or more flushing channels 6al a supplementary flushing groove 6a2 passing from one or more feed openings Y of the feed flow arrangement 6a toward the outer periphery of the first drilling means 4.

In figures la - lc and 2a - 2c are shown two exemplary alternative embodiments of the present invention in connection with drilling devices 1 having flushing channels 6al with supplementary flushing grooves 6a2 on the drilling surface PI of the first drilling means 4 or the pilot. In figures 3a -3c and 4a - 4c are shown furthermore two exemplary alternative embodiments of the present invention in connection with drilling devices with only flushing channels 6al on the drilling surface PI of the pilot 4. As an advantageous embodiment of the down-the-hole drilling device, according to figures la, lb and 2a, 2b, the one or more flushing channels 6al and/or the supplementary flushing grooves 6a2 get wider in longitudinal direction r thereof toward the outer periphery of the first drilling means 4 (these kinds of embodiments particularly regarding the supplementary flushing grooves have not been shown in the drawings) .

As an advantageous embodiment of the down-the-hole drilling device according to the invention, the one or more flushing channels 6al and/or supplementary flushing grooves 6a2 are connected to a return flow channel 6b' of the exhaust flow arrangement 6b on the side surface of the first drilling means 4 with a part 6al', 6a2' having a backward sloping bottom.

As a furthermore advantageous embodiment of the down-the-hole drilling device according to the invention, with reference to figures 3a - 3c and 4a - 4c, the flushing channels 6al and/or, with reference to figures la - lc and 2a - 2c, the supplementary flushing grooves 6a2 have a cross section perpendicular to longitudinal direction r thereof that remains constant for the whole length thereof. The drilling devices in the appended drawings have a pilot 4; 4a with a planar drilling surface PI, instead of which the drilling devices according to the invention may naturally also have a pilot with a drop center i.e. concave front or the like.

Furthermore, as an advantageous embodiment of the down-the-hole drilling device according to the invention, the flushing channels 6al and/or the supplementary flushing grooves 6a2 comprise a bottom 6al", 6a2" in an essentially transverse plane with respect to the longitudinal direction s of the drilling device as shown e.g. in figures la - lc and 3a - 3c.

Thanks to the above explained constructions of the flushing flow arrangement, the advantages mentioned above of the present invention can be made possible.

It is clear that the invention is not limited to the embodiments shown or described above, but instead it can be modified within limits of the basic idea of the present invention according to the needs at any given time. It is thus clear, that the constructions of the drilling devices being illustrated in the drawings may vary in practice very much merely when being carried out with differing diameters and particularly even with different kinds of feed channels and/or flow ducts and grooves in general of the flushing flow arrangement. So, the one or more feed channels may have one or more cylindrical sections with a constant cross section in connection with one or more expanding sections thereof. Furthermore e.g. the flushing grooves with constant width in the longitudinal direction thereof as well as supplementary flushing grooves with increasing width can be exploited, or the bottoms thereof may be sloped backward in an arched manner. Also the one or more feed channels, the flushing channels and/or the supplementary flushing grooves may be arranged in more or less sloped positions than shown in the drawings. Furthermore bevellings in different corners of the drilling device constructions shown in the drawings can be replaced by more or less rounded shapes etc.

On the other hand, instead of the type of embodiments shown in the drawings, it is naturally possible to use as the drilling device also other drilling devices that are applicable for the same purpose, in which a casing pipe may be exploited in connection with the drilling that is drawn into the ground unrotatively without or with a casing shoe. The casing pipe can naturally also be pulled into the hole by the first frame part i.e. the pilot, in which case the second frame part i.e. the reamer, such as a "reaming ring", may be situated further back in the longitudinal direction than the reamers presented in the drawings. It is not that significant for the down-the-hole drilling device according to the invention, either, how the first and second drilling means are coupled with each other, so that a wide variety of different solutions can be exploited as the power transmission assemblies between the same.