EP2496786B1 - Method for the drilling, in particular percussion or rotary percussion drilling, of holes in soil or rock material and device therefor - Google Patents

Description

The present invention relates to methods for drilling, in particular impact or rotational impact drilling holes in soil or rock material, wherein a borehole is formed by a drill bit mounted on a drill string by a striking and / or rotating movement, a cladding tube adjoining the drill bit Pulling and / or hitting is introduced into the borehole and mined material is introduced via at least one passage opening formed between the drill bit and the cladding tube into the annular space formed between the outer circumference of the drill string and the inner circumference of the cladding tube and discharged from the borehole. Furthermore, the invention relates to a device for drilling, in particular impact or rotary impact drilling holes in soil or rock material, wherein formed by a drill bit mounted on a drill bit by a beating and / or rotating movement a borehole, a subsequent to the drill bit sheath Pulling and / or beating can be introduced into the borehole and mined material can be introduced via at least one through-bore formed between the drill bit and the cladding tube into the annular space formed between the outer circumference of the drill string and the inner circumference of the cladding tube and can be brought out of the drilled hole.

For producing holes in soil or rock material by a percussion or rotary impact drilling is by means of a drill string mounted on a drill bit, wherein moreover a jacket or sheath into the well for an optionally required further lining, or to a breaking material With certainty, the impact energy is either applied directly to the drill bit via the drill string or through complicated devices such as slippers.

Depending on the degraded soil or rock material and depending on whether the hole formed in the soil or rock material to be used below to receive a rock anchor, to form a pipe shield or drainage of the soil or rock material, as well as in Depending on the soil or rock material, in particular its hardness, stratification, but also on whether this soil or rock material inclusions, such as mountain water or the like., Depending on the choice of drill bit to be used, the drill string and either co-contracted or embarked cladding tube , where very often on the same site the most diverse Elements, such as drill bit, linkage and in particular different ducts must be used.

The EP 1 818 499 A1 relates to a device for the simultaneous drilling and lining of boreholes, in which a drill bit is connected to an adapter, which adapter is further connected to a drill string. In addition, a tubular surrounding the drill pipe is provided, which is introduced by being hammered by the adapter simultaneously with the formation of the borehole in the borehole. For this simultaneous introduction of a cladding tube into the borehole and the formation of the same an adapter is used in this case, which partially transfers the impact energy to the drill bit and partially on the cladding tube.

The GB 1,068,638 describes a drilling device consisting of a central drill bit and a ring bit, wherein on the ring bit detachably a cladding tube is hinged, which has such a coupling that the impact energy introduced via the drill string is partially applied to the central bit and partially to the ring bit.

Of the US 2006/0060388 A1 is a drill bit and a threaded connection for the same can be seen.

The present invention now aims to develop a method and a device of the type mentioned in that adaptation to a variety of subsoil conditions is possible quickly and reliably and that any combinations of the elements used when drilling holes in soil or rock directly can be assembled and used on site in accordance with the requirements. Furthermore, it is an object of the invention to minimize the number of different prefabricated holes drilling apparatuses.

To solve these objects, a method of the type mentioned is essentially characterized in that the impact energy of the drill string is applied via a cooperating with the drill bit and the drill string adapter to the drill bit and that the impact energy at least partially on a hitting the adapter and at least partially is applied to the drill bit via a threaded connection between adapter and drill bit. By the Impact energy of the drill string is applied via a cooperating with the drill bit and the drill pipe adapter to the drill bit, it is easily possible to perform the inventive method so that depending on the existing mining or soil conditions, the most suitable elements are used can. Furthermore, by carrying out the method according to the invention in such a way that the impact energy is applied at least partially to the drill bit via a shoulder of the adapter and at least partially via a threaded connection between the adapter and the drill bit, a secure and reliable transmission of the impact energy to the drill bit succeeds on the one hand On the other hand, it is ensured that the threaded connection intended for the connection of the drill bit to the adapter is not knocked out during the drilling operation and thus, if necessary, a connection between the drill bit and the adapter is made impossible after the end of the drilling operation.

In order to ensure that, in particular after completion of the drilling operation, the adapter can be separated from the drill bit without damaging the components, the method according to the invention is preferably guided such that the adapter is coupled to the drill bit by screwing via a coarse thread connection. In particular, by coupling the adapter to the drill bit by screwing via a coarse screw connection, it is possible to ensure that screwing after completion of the drilling operation, and in particular after the threaded connection of the adapter to the drill bit of the large load has been applied by introducing the impact energy, safely and reliably to solve and deploy the drill pipe together with the adapter from the borehole. Furthermore, this ensures that the adapter can be used multiple times, which brings not inconsiderable economic benefits.

In addition, it is possible with such training during drilling holes in soil or rock material, if necessary, to replace the drill pipe entirely, for example due to excessive stresses or wear or defects on the linkage or if the subsoil conditions, for example, require the use of more stable linkage.

In order to ensure that, during the drilling of holes in soil or rock material, there is no accidental release of the drill string from the adapter, the method according to the invention is preferably developed in such a way that that the adapter with the drill string by screwing over a thread, in particular a relation to the threaded connection between the drill bit and adapter lower pitch exhibiting thread is coupled. With such a design of the method according to the invention, it can be ensured that, in particular during drilling, the drill pipe together with the adapter can be removed from the drilled hole without unintentionally releasing the connection between the drill pipe and the adapter, in order to be able to carry out any necessary adaptation work.

In order to ensure that drill cuttings formed during the drilling of holes are transported away and that no openings of the drill bit are laid, the method according to the invention is preferably developed in such a way that flushing liquid is discharged through the tubular adapter and cooperating openings in the drill bit during drilling. By carrying out the method according to the invention in such a way that flushing liquid is discharged through the tubular adapter and cooperating openings in the drill bit during drilling, it is possible on the one hand to apply sufficient amounts of flushing liquid during drilling with a structurally simple device, both to the Digestion as well as possibly directly to a remote from the well interior end portion of a drill bit or in an annulus between the drill bit and a cladding tube to keep installing the openings and passages with cuttings, and also to ensure that an excessive loss of rinsing fluid during drilling are avoided can.

In order to prevent in particular the discharge of an excessive amount of rinsing liquid during the drilling process, the invention is further developed such that rinsing liquid is applied intermittently via an adapter arranged in the intervention rinsing valve during engagement of the drill bit in the soil or rock material. By intermittently engaging an intervention-controlled flushing valve during the engagement of the drill bit in the soil and rock material on the one hand, excessive liquid discharge or an excessive amount of liquid, which is introduced through the flushing opening of the drill bit in the well, avoided with certainty and on the other hand ensured at the same time sufficient quantities of liquid are provided for the removal of the cuttings inside the well.

In order to safely and reliably carry along with the formation of a hole in soil and rock a cladding tube in the interior of the borehole, in particular entrainment, the inventive method is preferably developed to the effect that the impact energy in addition at least partially trained on the drill bit on the shoulder Cladding tube is applied. In addition, during the method for drilling holes in soil and rock material, part of the impact energy is additionally applied to the cladding tube via a striking shoulder formed on the drill bit, ensuring reliable and reliable pulling of the cladding tube into the interior of the borehole.

To solve the problems mentioned above, a device for drilling, in particular impact or rotary impact drilling of soil or rock material of the type mentioned above essentially characterized in that a cooperating with the drill pipe and the drill bit adapter is provided and that the adapter via a striking shoulder of the Adapters and a threaded connection between the adapter and drill bit with the drill bit cooperates. By providing a universally applicable adapter cooperating with the drill string and drill bit, the drill bit and drill string can be arbitrarily selected to suit the requirements of forming a hole in the soil and rock material and combining the respective suitable elements. By forming the adapter so that the adapter interacts with the drill bit via a shoulder of the adapter and via a threaded connection between the adapter and the drill bit, it is ensured that, on the one hand, the drilling energy is reliably and reliably transmitted to the drill bit, and on the other hand, that the vulnerable for a knocking or damaging threaded connection between the adapter and drill bit is claimed as little as possible.

By coupling the adapter to the drill bit via a coarse screw connection, as is the case with a preferred development of the device according to the present invention, a distribution of the forces is achieved such that damage to the threaded connection is certainly withheld and, on the other hand, it is ensured upon release of the adapter and the drill pipe from the drill bit, the connection between the drill bit and the adapter is opened easily and reliably and in particular before loosening of other threads, if appropriate.

Such a threaded connection can be formed, for example, as a helical thread connection with two gears, with which both a secure and reliable hold of the adapter in the drill bit can be ensured and on the other hand, an intentional release of the adapter can be achieved from the drill bit.

By, as corresponds to a preferred embodiment of the present invention, the device is designed so that the adapter with the drill string via another thread, which has a deviating from the threaded connection between the adapter and drill bit pitch of the thread, in particular a smaller pitch, coupled, it is possible to withhold accidental release of the adapter from the drill pipe both during the drilling process and when unscrewing the adapter from the drill bit with certainty. Furthermore, it is ensured with such a design that at least the drill pipe and the adapter can be recovered undamaged at the end of the drilling process, whereby a not insignificant cost savings can be achieved.

By, as this corresponds to a preferred development of the present invention, the device is designed so that the end face of the adapter facing the well bore is at least partially beveled, it succeeds, the adapter coupled to the drill string, especially if maintenance during the formation of the well are required to safely insert together with the drill string in the drill bit and to screw with this, so that even for example in semi-finished holes adaptation work on the linkage can be made.

For a reliable introduction of rinsing liquid into the interior of the borehole, the invention is preferably further developed such that the tubular adapter is formed with a bore hole interior facing passage for rinsing liquid and that the passage opening cooperates with openings for dispensing rinsing fluid in the drill bit. With such a device it can be ensured that rinsing liquid is introduced into the rinsing holes formed in the drill bit through the hollow adapter and is available in the interior of the borehole for the drilling operation and optionally in the annular space between drill bit and cladding tube, so that on the one hand the removal of the cuttings by trained in the drill bit in a conventional manner Openings or recesses is made and on the other hand, a laying of the openings for both the rinsing liquid and for the removal of cuttings in the drill bit or, where appropriate, the annulus or annular gap is prevented.

According to one embodiment of the invention, the device is designed so that an intervention-controlled flush valve is provided in the adapter. By providing an intervention-controlled flushing valve in the adapter, a controlled discharge of flushing liquid through the adapter and through the flushing holes formed in the drill bit succeeds, whereby on the one hand only those quantities of flushing liquid are discharged which are required for a proper removal of the cuttings and, on the other hand, an installation the openings, in particular the flushing opening with cuttings is held back. In this case, the intervention-controlled flushing valve can be formed via a pressure switch or a pressure valve formed in the above-described annular space.

In order to use the introduced by the adapter drilling energy in particular for the entrainment of a cladding tube or to apply the impact energy on a cladding tube safely and reliably, the device according to the invention is further developed such that the drill bit at least one impact shoulder for cooperation with the Cladding tube, in particular for impact stress of the cladding tube has. By such a design ensures that the cladding tube is also subjected to impact stress during the impact stress of the drill bit in its front end region and thus can be introduced without knocking from the outside into the wellbore. The cladding tube is thereby pulled by the impact stress at its front end into the interior of the borehole.

By, as this corresponds to a preferred development of the present invention, the cladding tube is formed so that it is thickened at its end facing the inside of the bore hole and that the thickening is formed at its end remote from the bore hole complementary to a shoulder of the drill bit, is through a co-operation of the complementarily shaped impact shoulder of the drill bit with the thickened region of the cladding tube ensures reliable impact or introduction of the cladding tube into the drilled hole.

With such a design, for example, before starting a drilling process, any cladding tube, which appears suitable for the expected drilling process, for example, an expandable cladding tube at an end region of a drill bit facing away from the bore hole inside are arranged and are determined by pressing on the drill bit, in particular in such a way that the cladding tube along the drill bit is longitudinally displaceable permanently connected to the drill bit. Since the thickening of the cladding tube at its end region facing away from the bore hole inside the borehole, in particular during the impact stress, comes into contact with the impact shoulder of the drill bit, a reliable pulling of the cladding tube into the drilled hole is ensured. In the event that during the drilling process, in particular in the area in which the cladding tube along the drill bit is longitudinally displaceable, broken cuttings displacement of the cladding tube is no longer possible, can restore the free movement of the cladding tube in the borehole interior, for example by a Impact stress can be achieved from the outside.

By, as this corresponds to a preferred development of the present invention, the device is developed so that the end of the cladding tube facing the well inside is formed with a recess, in particular an asymmetrically formed recess, the drill bit can be dropped from the cladding tube, creating a separation can be achieved by the drill bit and cladding tube and, for example, in the case of a shared drill bit at least a portion of the drill bit after completion of the drilling process is recoverable together with the drill pipe and the adapter from the well.

• Fig. 1 einen Schnitt durch die erfindungsgemäße Vorrichtung zur Durchführung des erfindungsgemäßen Verfahrens zum Bohren von Löchern,
• Fig. 2 eine Außenansicht, teilweise in der Perspektive der Vorrichtung von Fig. 1,
• Fig. 3 einen Längsschnitt durch eine Variante des Adapters von Fig. 1,
• Fig. 4 einen Längsschnitt durch eine abgewandelte Variante des Adapters gemäß der Erfindung, und
• Fig. 5 einen Schnitt durch den dem Bohrlochinneren zugewandten Endbereich einer Variante eines Hüllrohrs der erfindungemäßen Vorrichtung zum Bohren von Löchern.

The invention will be explained in more detail with reference to embodiments shown in the drawing. In these show:

• Fig. 1 a section through the device according to the invention for carrying out the method according to the invention for drilling holes,
• Fig. 2 an external view, partly in the perspective of the device of Fig. 1 .
• Fig. 3 a longitudinal section through a variant of the adapter of Fig. 1 .
• Fig. 4 a longitudinal section through a modified variant of the adapter according to the invention, and
• Fig. 5 a section through the end of the hole facing the inside of a variant of a cladding tube of erfindungemäßen device for drilling holes.

In Fig. 1 It can be seen that a generally designated 1 device for drilling or rotary drilling holes in soil or rock material has a drill bit indicated schematically with 2, which via an adapter 3 with a in Fig. 1 schematically indicated drill pipe 4 is connected.

Furthermore, the drill bit 2 is adjoined by a cladding tube 5, whose end region 6 facing the bore hole interior has an enlarged thickness relative to the area of the cladding tube 5 facing the borehole exterior. This end region 6 is beveled at its end region 7 facing away from the bore hole inside and formed complementarily in the shape of a striking shoulder 8 of the drill bit 2. During the drilling of holes, at least part of the impact energy is applied by the training over the hitting shoulder 8 to the chamfer 7, so that the sheath 5 is pulled into the borehole 1 during the drilling progress.

The drill bit 2 is connected to the adapter 3 with a thread schematically indicated by 9, wherein over the borehole facing the end of the adapter 3 and the drill bit 2, an annular space 10 is formed, through which annular space 10 rinsing liquid, which by a hollow inside trained adapter 3 provided rinsing liquid channel 11 and provided in the drill bit 2 holes 12 for the passage of rinsing liquid to the interior of the wellbore is ausbringbar.

The over the drill pipe 4 applied to the adapter 3 drilling energy is in accordance with the training Fig. 1 Such a design ensures that the thread 9 is not excessively stressed during the drilling process and in particular is not knocked out, so that after the end of the drilling process a safe and reliable separation of the adapter 3 is made possible by the drill bit 2.

In the Fig. 1 illustrated drill bit 2 is in this case a conventional one-piece drill bit, which has a plurality of drill pins 14 and in addition to the openings, the dispensing of rinsing fluid 12 recesses 15, over which cuttings formed by between the cladding tube 5 and the drill bit 2 recesses 16 in between the adapter 3 and the drill pipe 4 and the cladding tube 5 formed annular space 17 are introduced can and can be discharged in the sequence on the outside of the borehole. In order to hold back laying of the annular space 17 with cuttings, the drill bit 2 also has a backward flushing channel 27, through which the annular space 17 can be sufficiently rinsed.

In the presentation according to Fig. 2 are the reference numerals of Fig. 1 retained, where in the representation of Fig. 2 it can be seen that the cladding tube 5 at its the bore hole facing inner end portion 6 has a relation to the borehole outer facing area reduced diameter, which diameter reduction can be achieved in a simple manner by pressing the cladding tube 5 on a drill bit 2, so that before the start of a drilling operation Any combination of drill bit 2, adapter 3, drill pipe 4 and sheath 5 can be put together depending on the expected requirements, whereby an extremely simple and inexpensive variant of a device for drilling holes in soil and rock material can be achieved. It is needless to say that the cladding tube 5 in this variant can be any cladding tube, as used during drilling holes in soil and rock material used, such as a frictionally introduced cladding tube, expandable cladding tube, drainage tube or even a example certain mobility of the individual forming the cladding tube segments exhibiting cladding tube, which can follow to a certain extent deviations from the direction of the bore.

The drill bit 2 used in this context may deviate from the illustrations according to Fig. 1 and Fig. 2 be selected arbitrarily, in addition to a one-piece drill bit a multi-part drill bit, from which after completion of the drilling process, for example, only a part remains inside the well, an asymmetrically shaped drill bit and a drill bit, which instead of drilling pins cutting can be used.

In Fig. 2 is further schematically at the top of the bore hole facing the edge 18 of the cladding tube 5 an asymmetrically formed recess 19 recognizable, which recess 19 has a vertical or steep side wall 26 and a second cheek 20 low pitch, with such a depression, for example, the discarding the drill bit 2 is possible after completion of the drilling process.

In Fig. 3 is a variant of the adapter 3 of Fig. 1 shown, wherein the adapter in turn on the one hand a thread 9 at its end, which is to be coupled with a drill bit 2 has. The thread 9 of the adapter 3 is in this case designed as a coarse thread with two courses, on the one hand to ensure a secure and reliable connection of the adapter 3 with the drill bit 2 during the drilling process and on the other hand to be able to solve the adapter 3 of the drill bit 2 so after completion of the drilling process in that the connection between the drill bit 2 and the adapter is that connection of the entire apparatus 1 for drilling holes in soil or rock material which first comes loose under appropriate stress.

In addition to the again schematically indicated passageway 11 for rinsing liquid, a further thread 21 is provided in the interior of the hollow adapter 3 at its borehole outer facing region for connection to a drill pipe 4, wherein the thread 21 in comparison with the thread 9 on the one hand significantly more courses and on the other hand has a significantly low pitch to withstand accidental release of the connection of the adapter 3 with the drill string, in particular after completion of the drilling operation with certainty.

In the variant of Fig. 3 the hitting shoulder 13 of the adapter 3 is different from the illustration according to Fig. 1 bevelled trained in order to apply the impact energy even better on the drill bit 2, in particular, in a beveled design of the striking shoulder 13, the wear of the striking shoulder 13 is significantly reduced.

In addition, in the variant according to Fig. 3 the borehole interior facing end portion 22 of the adapter 3 is provided with bevels 23 to facilitate insertion or threading of the adapter 3 in a drill bit 2, which is particularly advantageous when replacing the drill string during the drilling process.

Also in the presentation of Fig. 4 , which essentially coincides with that of Fig. 3 the adapter 3, the adapter 3 has a coarse thread 9 for the insertion of the adapter 3 in a drill bit 2, as well as another thread 21, which has a relation to the thread 9 significantly reduced pitch and a significantly increased number of courses. Furthermore, as well as in the illustration of Fig. 3 the hitting shoulder 13 is beveled and formed a chamfer 23 on the end face 22 of the adapter 3, which faces the bore hole inside.

Deviating from the illustration according to Fig. 3 is in the variant according to Fig. 4 a pressure switch 24 is provided on the end surface 22, via which pressure switch 24 an intermittently openable valve 25, which is indicated schematically in the passage 11 for dispensing rinsing liquid, is provided. During the drilling process, the pressure switch 24 is actuated by the pressurization in that beating process, whereupon the valve 25 is opened and rinsing liquid is discharged either directly through holes provided in the drill bit for rinsing liquid 12, or via the annular space provided between the drill bit 2 and the adapter 3 10 and the opening for flushing fluid 12 is discharged to the well interior. Such training ensures that excessive flushing fluid usage is avoided during the drilling operation, while ensuring that the normally small orifices for drilling fluid in the drill bit are not misplaced during drilling with cuttings.

In connection with the adapter 3 it is stated that its external dimensions, such as e.g. its threads 9 and 21 are designed such that are suitable for all common drill bits 2 and drill pipe 4, so that the adapter 3 is a universal element, by its use also any commonly used ancillary equipment, such as flip-flops, special connecting sleeves for connecting Drill bit and drill pipe and the like. Not required, resulting in a simplified, economical and universally applicable device for drilling holes in soil or rock material by using the adapter 3 according to the present invention.

In the illustration according to Fig. 5 is a section, in particular a longitudinal section through the end of the bore hole facing an end of a cladding tube 5, in turn, the end of the bore hole facing the inner end portion 6 of the cladding tube 5 is formed thickened. At the transition of the thickened end region 6 to the outside of the borehole facing region of the cladding tube 5, in turn, a shoulder 7, for cooperation with a shoulder 8 of a drill bit 2 is formed in order to move the cladding tube 5 into the borehole interior.

In the illustration according to Fig. 5 the recess 19 is shown on the side facing the bore hole interior edge region 18 of the cladding tube 5, wherein the side cheek 20 of the recess 19 is formed such that it extends to the edge 18 with a slight slope. The second side cheek 26 of the recess 19 is in this case formed normally on the edge 18, with which variant manages to throw off a drill bit 2 after completion of the drilling operation by a slight rotation of the cladding tube 5, either at least partially recover the drill bit 2 or the drilling process without to continue a carried-over cladding tube 5.

By, as shown in the illustration Fig. 1 can be removed, the cladding tube 5 is pressed onto the drill bit 2 that it is slidably mounted in the longitudinal direction of the drill bit 2, in addition, if necessary, from the Bohrlochäußeren on the cladding tube 5 a striking energy are applied to the addition of the Hüllrohrs 5 on the coupling between the hitting shoulder 8, the drill bit 2 and the shoulder 7 of the cladding tube 5 also allow a wrapping of the cladding tube 5. Such wrapping of the cladding tube 5 may be required in certain cases, such as when the passage gap 16 between drill bit 2 and cladding tube is laid by cuttings or further entrainment of the cladding tube 5 with the drill bit 2 due to broken material, which the space between the edge 18 of the cladding tube 5 and a corresponding to the cladding tube 5 superior or with this flush final area of the drill bit 2 to eliminate.

Claims (15)

1. A method for drilling, in particular percussion or rotary percussion drilling, holes in soil or rock material, wherein a borehole is formed by a drill bit (2) mounted on a drill rod assembly (4) by a percussive and/or rotational movement, a casing (5) adjoining the drill bit (2) is introduced into the borehole by being pulled and/or struck, and material that is removed is introduced into the annular space formed between the outer circumference of the drill rod assembly (4) and the inner circumference of the casing (5) via at least one passage opening formed between the drill bit (2) and the casing (5), and is discharged from the borehole, characterized in that the impact energy of the drill rod assembly (4) is applied to the drill bit (2) via an adapter (3) cooperating with the drill bit (2) and the drill rod assembly (4), and that the impact energy is applied to the drill bit (2) at least partially via an impact shoulder (13) of the adapter and at least partially via a threaded connection between the adapter (3) and the drill bit (2).
2. A method according to claim 1, characterized in that the adapter is coupled to the drill bit (2) by screwing via a quick-acting screw thread connection (9).
3. A method according to claim 1 or 2, characterized in that the adapter (3) is coupled to the drill rod assembly (4) by screwing via a thread (21), in particular a thread having a smaller pitch than the threaded connection (9) between the drill bit (2) and the adapter (3).
4. A method according to any one of claims 1, 2 or 3, characterized in that flushing fluid is discharged during drilling through the tubular adapter (3) and through operating openings (12, 27) provided in the drill bit (2).
5. A method according to claim 4, characterized in that flushing fluid is intermittently discharged during an engagement of the drill bit (2) with the soil or rock material via a flush valve (25) disposed in the adapter (3) and controlled as a function of said engagement.
6. A method according to any one of claims 1 to 4, characterized in that the impact energy, in addition, is at least partially applied to the casing (5) via an impact shoulder (8) formed on the drill bit (2).
7. A device for drilling, in particular percussion or rotary percussion drilling, holes in soil or rock material, wherein a borehole is formed by a drill bit (2) mounted on a drill rod assembly (4) by a percussive and/or rotational movement, a casing (5) adjoining the drill bit (2) is introducible into the borehole by pulling and/or striking, and removed material is introducible into an annular space formed between the outer circumference of he drill rod assembly (4) and the inner circumference of the casing (5) via at least one passage opening formed between the drill bit (2) and the casing (5), and is dischargeable from the borehole, characterized in that an adapter (3) cooperating with the drill rod assembly (4) and the drill bit (2) is provided, and that the adapter (3) cooperates with the drill bit via an impact shoulder (13) of the adapter (3) and via a threaded connection (9) provided between the adapter (3) and the drill bit (2).
8. A device according to claim 7, characterized in that the adapter (3) is coupled to the drill bit (2) via a quick-acting screw thread connection (9).
9. A device according to claim 7 or 8, characterized in that the adapter (3) is coupled to the drill rod assembly (4) via a further thread (21) having a pitch differing from that of the thread connection (9) between the adapter (3) and the drill bit (2), in particular a smaller pitch.
10. A device according to claim 7, 8 or 9, characterized in that the end face (21) of the adapter (3) facing the interior of the borehole is designed to be at least partially chamfered (23).
11. A device according to any one of claims 7 to 10, characterized in that the tubular adapter (3) is formed with a passage opening (11) for flushing fluid facing the interior of the borehole, and that the passage opening (11) cooperates with openings 12, 27) for discharging flushing fluid, that are provided in the drill bit (2).
12. A device according to any one of claims 7 to 11, characterized in that an engagement-controlled flush valve (24, 25) is provided in the adapter (3).
13. A device according to any one of claims 7 to 12, characterized in that the drill bit (2) comprises at least one impact shoulder (8) for cooperating with the casing (5) and, in particular, applying an impact stress on the casing (5).
14. A device according to any one of claims 7 to 13, characterized in that the casing (5) is thickened in its end region (6) facing the interior of the borehole and the thickened portion, in its end region facing away from the interior of the borehole, is designed complementary to an impact shoulder (8) of the drill bit (2).
15. A device according to any one of claims 7 to 14, characterized in that the end region (18) of the casing (5) facing the interior of the borehole is designed with a depression (19), in particular an asymmetrically shaped depression (20, 24).

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