EP3587729A1 - Connection of two drill string elements of a drill string for earth drilling - Google Patents

Abstract

The invention relates to a system for connecting two drill string members of a drill string for drilling into the ground, wherein one drill string member has a plug element arranged at the end in the form of a plug and the other drill string member has a plug element arranged at the end in the form of a socket, the plug and socket being designed to form a plug connection that the two drill string members have aligned through holes through which a pull-off protection device can be inserted, and the pull-off safety device has a head and an end spaced from the head, a thread being formed at the end and the head and end being spaced apart such that the end at introduced pull-off protection is exposed at the end.

Description

The invention relates to a system and a method for connecting two drill string members of a drill string for earth drilling and to the use of a pull-off protection when connecting two drill string members of a drill string for earth drilling.

In rod-based drilling in the ground, in particular for the production of so-called horizontal bores, which can run essentially parallel or at a relatively small angle to the surface of the earth, a drill head is driven by means of a drill rod, the so-called drill string, from a drive device arranged on the surface of the earth or in an excavation pit propelled. The drill rods used in this process usually consist of individual, interconnected rod sections that are gradually attached to the rear end of the drill pipe that has already been drilled and connected to it, in accordance with the drilling process.

Different configurations are known for connecting the rod sections or members of the drill string to one another. The rod sections can be connected by means of a threaded connection and / or a plug connection.

Out DE 10 2011 010 958 A1 it is known to specify a possibility for connecting two drill pipe sections of a drill pipe which combines the advantages of the threaded connections known from the prior art and the axial plug connections with one another. A plug connection is described which - similar to a threaded connection - is spiral-shaped on a circular cross-section Threaded plug or in a corresponding threaded bushing projections / grooves is based, wherein the projections / grooves are designed so that the self-locking characteristic of a threaded connection does not occur.

Based on this prior art, the object of the invention was to provide an improved possibility for connecting two drill string members of a drill string for earth drilling, which in particular enables a simpler design and / or a safe and / or simple connection.

This object is achieved by the subject matter of the independent claims. Advantageous embodiments are the subject of the respective dependent claims and / or result from the following description of the invention.

The invention is based on the idea of specifying a possibility for connecting two drill string members, which combines both a plug connection and a screw connection. The two drill string links can be inserted into each other and a pull-off protection is used, which is exposed at the end and can be screwed on.

It was recognized according to the invention that, in a departure from the previously prevailing opinion, which considered screwing drill string members or a thread generally disadvantageous, to use a screw-off pull-off protection with two plug-in drill string members, the thread of the pull-off protection also being able to be guided outwards to access it from the outside. Despite the harsh conditions in the ground and the mechanical loads and / or corrosion, which can lead to a high stress on a threaded connection, it was recognized according to the invention that a pull-off protection, with an externally exposed thread, which can be screwed to a counterpart from the outside , can be advantageous. The exposed end of the pull-off protection also makes it possible to access the end for releasing the pull-off protection.

The invention provides a system for connecting two drill string members of a drill string for earth drilling, wherein one drill string member has a plug element arranged at the end in the form of a plug and the other drill string member has a plug element arranged at the end in the form of a socket. The plug and socket are designed to form a plug connection in such a way that the two drill string members have through holes which are aligned with one another and through which a pull-off protection can be inserted. The pull-off protection has a head and an end spaced from the head, a thread being formed at the end of the pull-off protection. The head and end of the pull-off protection are spaced apart from one another that the end of the pull-off protection is exposed at the end when the pull-off protection is inserted into the through holes.

For the purposes of the description, the term “drill string” encompasses a string having an earth drilling tool and a rod that can be moved through the earth by means of an earth drilling device or a drive device in order to drill an earth hole.

For the purposes of the description, the term “linkage” does not only include rigid linkage comprising individual linkage sections that are directly or indirectly connected to one another, but linkage in particular, but in particular all power transmission elements that can be used in an earth drilling device.

The term "rod section" in the sense of the description comprises an element which extends along a longitudinal axis and which is part of the rod or a drill string for drilling into the ground. The rod section can be designed as an element arranged in the front of the drill string with an assigned function (transmitter housing or the like) or as an element (only mechanical) that extends the drill string as a rod section. The rod section can comprise mechanical channels, for example for drilling fluid, electrical lines, electrical elements and / or electronic elements.

The term “earth drilling tool” encompasses a drill head arranged at the front end of the drill string, in which movable parts can be provided. However, it can also be provided that the earth drilling tool has an immovable or rigid or largely immovable or rigid outer contour.

The term "earth drilling device" as used in the description encompasses any device which can move a drill string having rod sections in an existing or to be created channel in the ground, in order to create or expand a hole, in particular a horizontal hole, or to conduct lines or other long pipes Body into the ground. An earth drilling device can comprise a drive device that pulls and / or pushes a drill string. It can additionally or alternatively be provided that the drive device drives the drill string in a rotary manner.

The term "horizontal drilling" in the sense of the description includes in particular any type of existing or to be created, preferably horizontal, channels in a body, in particular earth channels including earth bores, rock holes or earth pipes as well as underground or above-ground pipelines and water channels that can be created or pulled in using an appropriate earth drilling device.

The term "drill string member" denotes a section of the drill string that can be releasably connected to other sections of the drill string. In particular, a drill string member can be a rod section. It is also possible for a drill string member to be a connecting element for two rod sections which are connected to one another indirectly via the connecting element.

For the purposes of the description, the terms “plug” and “socket” encompass an embodiment as an element of a pair of mechanical coupling elements, of which one (“plug”) can be at least partially inserted into the other (“socket”) in order to Form connection. To transmit rotational forces, the plug and / or socket can have circumferential stop or abutment surfaces which abut against the other element with abutment or abutment surfaces and can act on them alternately in the event of thrust or pressure.

A drill string member advantageously has a plug element in the form of a plug at one end and a plug element in the form of a socket at the other end. However, it can also be provided that the drill string member has plug elements of the same shape at the end, so that the drill string member has a plug element in the form of a plug at both ends or a plug element in the form of a socket at both ends.

In the sense of the description, a "through hole" is a through hole that differs from a blind hole. The through hole does not necessarily have to have the same diameter or the same contour over the entire length. The contour surrounding the through hole can have an annular, elliptical, non-circular, polygonal or a mixed form of the aforementioned shapes. If the term “in alignment” is selected for the through holes in the description, this means that the through hole formed in the plug at least partially overlaps the through hole in the socket. In a particularly preferred embodiment, the through-holes are essentially coaxial to one another with attached drill string members; slight deviations, in particular tolerances due to manufacturing, are possible. It makes sense for the through holes or the through hole in the socket to have a larger cross-sectional area in relation to the longitudinal axis of the through hole than the cross-sectional area at least in a section of the through hole in the plug. As a result, an edge region of the head of the pull-off protection can rest on an edge in the through hole, in particular in the section of the plug, when the pull-off protection is inserted through the aligned through holes. The through hole in the socket and the The plug is preferably oriented essentially transversely to the longitudinal axis of the drill string member, an angle in the angular range between 70 ° and 110 ° being preferred, an angle close to 90 ° being particularly preferred, the angle being 90 ° being particularly preferred.

Numerical data in the sense of the description are data that may have a tolerance of +/- 10%, so that the numerical data describes not only the one value but a range of values, in particular to take into account tolerance ranges that may be caused by the manufacturing process.

In the sense of the description, the term “pull-off protection” encompasses an elongated or rod-shaped element which can be inserted through the aligned through holes in the plug and socket. The pull-off protection has a head, which has an enlarged cross-sectional area transverse to the longitudinal axis of the pull-off protection, in particular in relation to a shaft section. The area of the head facing the end with its enlarged cross-sectional area compared to the end and a shank section can have an edge-side contact surface, which in particular can rest on an outwardly (essentially radially) outer surface of the plug, this outer surface of the plug being located within a receptacle of the Connector can be present. The end spaced from the head is threaded. The end is exposed at the end when the pull-off protection is inserted. The end and / or thread can be accessed from the outside.

The plug can form a support for the head of the pull-off protection with an edge area when the pull-off protection is inserted. The plug can have a receptacle for the head, so that the head of the pull-off protection can be at least partially sunk into the plug.

An improved transmission of the forces via the drill string members of the system is made possible, whereby compressive forces can be transmitted via a stop of the plug connection between the plug and socket. Rotational forces can be transmitted via a profile formed within the plug connection between the plug and socket. Tractive forces are transmitted via the pull-off protection. The stop for transmitting the compressive forces can be formed by means of an edge of the socket and / or the plug, which are at least partially in contact with one another in the assembled state.

The thread used to secure the pull-off protection does not have to come into engagement with the drill string member itself, but a further element which is accessible from the outside can be used and which can be replaced independently of the drill string members. Should the thread or the pull-off protection be renewed yourself it is not necessary to revise or maintain the drill string link itself.

However, it can also be provided in a particularly preferred embodiment that a thread is provided in the plug element in the form of a plug at the end of the through hole, which thread is designed to interact with a thread of the pull-off protection. In the context of the description, the term “interaction” encompasses such a configuration that the pull-off protection has, at least in sections, an external thread which can interact with the internal thread formed at the end of the through hole of the plug. A screw connection between the pull-off protection and the thread present at the end in the through-hole of the plug, which is arranged in particular at the rear end of the through-hole of the plug in the direction of insertion, can be used to form a screw connection, which, in particular a first, safeguards against unintentional removal of the pull-off protection can form. In particular, this fuse can comprise an additional securing element, which can be in the form of a (wedge) locking washer, a spring washer, a serrated lock washer or the like. The securing element can rest on the head of the pull-off protection. For this purpose, a securing element can first be pushed onto the pull-off protection. The pull-off protection can then be inserted into the aligned through-holes of the socket and plug and screwed in with the thread formed at least on the end side of the through-hole of the plug and in particular tightened. The securing element at the head of the pull-off protection can largely prevent the pull-off protection from being released. If the securing element is designed as a wedge locking washer, a securing effect can be achieved in that there are different angles (ratios) between the wedge locking washer and the thread pitch. In particular, there can be an angle α on the wedge lock washer which is greater than the thread pitch β of the thread. If it is described in the description that a thread "at the end" is provided on the through hole of the plug, this does not rule out that the thread extends through the entire through hole of the plug. However, an arrangement or formation of a thread on the through hole only at the end with an otherwise thread-free through hole of the plug has the advantage that the thread in the form of an internal thread on the through hole extends only over a short area, which simplifies production.

The end of the anti-peel device, which is spaced from the head of the anti-peel device, is exposed by means of the through hole formed in the bushing and can also be provided with a thread. This thread can be configured in the same way as the thread which is connected to the internal thread of the through hole of the Connector interacts. This allows a simple configuration to be achieved. However, it is also possible for there to be another thread in addition to the external thread, which interacts with the internal thread formed at the end of the through hole of the plug. In this respect, the pull-off protection can have two different threads at its end. In the following it is described that the exposed thread can interact with an internal thread of a counterpart, in particular to prevent a first (plug has no internal thread interacting with the pull-off protection) or a second fuse (plug has an internal thread cooperating with the pull-off protection) To form a pull-off protection.

In a preferred embodiment, the head of the pull-off protection is designed to interact with a tool, in particular a tool acting on the pull-off protection from above. On the one hand, this makes it possible to act on the pull-off protection by means of a device in order to improve handling and / or to avoid direct contact with the hands of a user. On the other hand, tools can in particular be preferred which act in a direction which essentially corresponds to the longitudinal direction of the pull-off protection on the side of the pull-off protection spaced from the end of the pull-off protection. In particular, tools are preferred which act on an end face of the head which is essentially exposed in the longitudinal direction of the pull-off protection. Actions of a tool from the side from the outside, for example in the form of a socket wrench or a wrench, are possible, but not preferred, since they attack from the outside on the circumference and space is required for this. A tool which only engages in a recess in the head, which is formed in the longitudinal direction of the pull-off protection, enables the tool to engage in this recess and allows the pull-off protection with its head, in particular, to bear at least partially on the circumference of one or both drill rod members. A receptacle formed on the pull-off protection for interaction with an Allen key, hexagon socket, Torx or XZN (internal multi-tooth profiles) is preferred.

In a preferred embodiment, the head of the pull-off protection can be at least partially countersunk in a receptacle on the socket. This ensures that the cross-sectional area of the drill string members is not significantly increased or that there is no change in the cross-sectional area compared to a drill string member without a pull-off protection. In addition, a receptacle in the socket provides the possibility that the pull-off protection can at least rest with its head on the circumference of the socket, so that the tensile forces can be transmitted not only via a shaft section of the pull-off protection but also via the head of the pull-off protection. The receptacle on the socket can in particular with its inner contour The outer contour of the head of the pull-off protection at least partially match or be adapted to this. A form fit is possible. The cross section of the head of the pull-off protection and the cross section of the receptacle can be round, in particular in the form of a circle. Other shapes are possible, for example the head and / or receptacle can be elliptical, polygonal, rectangular, square or polygonal or have mixed forms thereof. The plug can preferably also have a receptacle for the head of the pull-off protection, so that the head of the pull-off protection can at least partially be countersunk in the direction of the extension of the through hole in the plug. In this way, the possibility can be created that the head also abuts the periphery of the receptacle in the plug, or only on the circumference, and that a power transmission is possible. A form fit is possible. The receptacle in the plug can be designed in accordance with the receptacle in the socket.

It is possible for securing elements to be pushed onto the pull-off protection in the longitudinal direction, one of which, in particular, can rest against the edge of the pull-off protection. Alternatively or additionally, it can be provided that a securing element can be pushed onto the exposed end of the pull-off protection when the pull-off protection is inserted and / or screwed on. Such a securing element has been described above in connection with the head system. The securing element to be pushed onto the exposed end of the pull-off protection can be designed in the same way as the securing element described above with reference to the system at the head of the pull-off protection.

In a preferred embodiment, a counterpart cooperating with the thread of the pull-off protection is present. The counterpart can be replaced without the need to replace one or both of the drill string links.

In connection with the counterpart, a securing element pushed onto the exposed end can represent an additional securing which offers a release of the pull-off protection in addition to the securing by means of the counterpart. For example, a counterpart can be screwed onto the thread configured at the end of the pull-off protection and, in conjunction with the screw connection between the pull-off protection and the thread on the end of the plug, can act like a lock nut. In this way, protection against loss of the pull-off protection can be formed. The securing element pushed onto the exposed end of the pull-off protection, which can be pushed onto the pull-off protection in front of the counterpart, can be a third securing.

In a preferred embodiment, the counterpart is designed to interact with a tool. This makes it possible to act on the counterpart with a device. The tool can preferably grip the counterpart “from above”, just as with the head of the pull-off protection. In particular, it can be provided that the tool does not engage the side of the counterpart. Preferably, an upward-oriented recess (substantially longitudinally spaced from the end) is provided, into which the tool can engage. In this way, the possibility can be created that the counterpart lies at least partially circumferentially on one or both of the drill rod members. In particular, the counterpart can at least partially abut the socket on the circumference. In particular, tools are preferred which act exclusively on the end face of the counterpart, which exists essentially in the longitudinal direction to the thread cooperating with the thread configured at the end of the pull-off protection. Actions of a tool from the side, for example in the form of a socket wrench or a wrench, are possible, but not preferred, since they attack from the side and space is required for this. A tool engaging in a recess of the counterpart, which is designed in the longitudinal direction, enables the tool to engage in this recess and allows the counterpart to bear, in particular at least partially on the circumference, against one or both drill rod members. A receptacle formed on the counterpart for interaction with an Allen key, hexagon socket, Torx or XZN (internal multi-tooth profiles) is preferred.

In a preferred embodiment, the counterpart is at least partially retractable in a receptacle on the socket. In this way it can be achieved that no substantial increase in the cross-sectional area of the drill string member is achieved, or that there is no increase in the cross-sectional area of the drill string member. A partial sinking of the counterpart in a receptacle formed in the plug is also possible.

A receptacle for the head of the pull-off protection or a receptacle for the counterpart is achieved by means of a dimension of the through hole which is adapted to the outer edge dimension of the head or the counterpart. A receptacle can thus be formed by means of a cross section of the through hole which is adapted to the cross section of the head or the counterpart. The edge of the receptacle can essentially correspond to the edge of the head or the counterpart, or can be larger than this. The recording can be ended by reducing the cross section of the through hole.

In a preferred embodiment, a shaft section is provided on the pull-off protection between the head and the end, which is threadless and / or whose circumference is greater than the circumference of the end. This can achieve that the stability of the system of the pull-off protection on the two drill string members is improved or increased. The stability can be improved by the non-machining and / or the choice of the dimension of the shaft section. Due to the fact that the circumference at the end is reduced compared to the circumference at the shaft section, a material weakening in the area of the plug is reduced or excluded. Any tensile loads on the drill string members that are at least partially transmitted via the pull-off protection can be transmitted through the shaft section, which is reinforced.

In a preferred embodiment, the through holes of the socket and / or the plug are configured without threads. This enables a particularly simple configuration of the drill string members. In particular, no thread has to be formed in the through hole with which the pull-off protection can interact. The step of creating or forming a thread on the drill string member is omitted. The maintenance of the drill string members is unaffected by the threadless design of the through holes.

In a particularly preferred embodiment, as described above, a thread is formed at the end of the through hole of the plug, which is in particular an internal thread and is designed to interact with a thread of the pull-off protection. This can provide protection against losing the pull-off protection, which is effective.

In a particularly preferred embodiment, the through holes are formed essentially transversely to the longitudinal axis of the drill string and / or are formed centrally in cross section. This enables the engagement and the connection to be stable under tensile load. The loading of the through holes, in particular for the connector, takes place in the area in which most of the material is present. Furthermore, a tensile load can be transmitted across the entire width and angling is almost impossible.

In a preferred embodiment, a plurality of through holes are formed in at least one of the plug elements, spaced apart in the longitudinal direction of the drill string members. As a result, several pull-off safeguards can be introduced and used when connecting the drill string links, which can transmit a tensile force.

In a preferred embodiment, the plug and socket each have a profile on the circumference, which can cooperate clockwise and / or counterclockwise around the longitudinal axis when the plug connection is formed for the transmission of rotational forces.

The profile allows the transfer of rotational forces between the drill string members with a trained plug connection. The plug has contact surfaces on the outer circumference which can be brought into engagement with contact surfaces in the socket, the contact surfaces being able to extend at least partially in the radial direction in order to be able to transmit the rotational forces. In the radial direction, as described, includes contact surfaces which can have an angle of 0 ° to 45 ° to the radial direction. The profile can be at least partially unchanged in the direction of insertion. The profile makes it possible to transmit rotational forces from one drill string link to the other drill string link. A profile can be provided that is at least partially unchanged in the longitudinal direction. As an alternative or in addition, however, it can also be provided that the profile changes in the longitudinal direction, for example in that a plug connection is selected in which protrusions / grooves extend spirally on a threaded plug with a circular cross section or in a corresponding threaded bushing. Profiles that are unchanged in sections in the longitudinal direction are particularly preferred. This enables simplified production. A splined profile is preferably used.

The invention also provides a method of connecting two drill string members of a drill string for earth drilling. The two drill string members are plugged into one another at the ends and aligned so that through holes arranged in the drill string members are aligned, a pull-off protection being inserted through the through holes, the exposed end of which can be screwed to a counterpart.

A method is created which, in particular, reduces the risk of injury to the user who connects the drill string members to one another, and yet enables a secure and resilient connection which can be carried out easily and / or is simply constructed.

The invention also provides use of a pull-off protection when connecting two drill string members of a drill string for earth drilling. The two drill string members are plugged into one another at the ends and aligned in such a way that through holes arranged in the drill string members are aligned. The pull-off protection is inserted through the through holes, a pull-off protection being used, the exposed end of which can be screwed to a counterpart.

The statements on the individual aspects of the invention, as described in relation to the system, the method and the use, are to be understood as complementary statements. Comments on one aspect also apply to the comments on one of the other aspects.

Like the following description of exemplary embodiments, the above statements do not constitute a waiver of specific embodiments or features.

The invention is explained in more detail below on the basis of exemplary embodiments illustrated in the drawings.

Fig. 1

zwei Bohrstrangglieder eines Bohrstrangs zum Erdbohren mit einer Abziehsicherung und einem Gegenstück;

Fig. 2

eine Schnittdarstellung der zwei in Fig. 1 dargestellten Bohrstrangglieder mit eingeführter Abziehsicherung und montiertem Gegenstück.

In the drawings:

Fig. 1

two drill string links of a drill string for earth drilling with a pull-off protection and a counterpart;

Fig. 2

a sectional view of the two in Fig. 1 shown drill string links with inserted pull-off protection and mounted counterpart.

Fig. 1 shows an isometric view of two drill string members 1, 2 of a drill string for earth drilling. The two drill string members 1, 2 are shown in a position in which they can be connected to one another. The drill string member 1 has a plug element 3 arranged at the end in the form of a plug 4. The drill string member 2 has a plug element 5 arranged at the end in the form of a bush 6.

Plug 4 and socket 6 are designed to form a plug connection. In particular, the outer circumference or the outer contour of the plug 4 is at least partially adapted to the inner contour of the socket 6. The outer contour of the plug 4 can essentially correspond to the inner contour of the socket 6.

For the transmission of rotational forces between the two drill string members 1 and 2 of the drill string, a profile is formed on the connector 4 in the circumferential direction, which has contact surfaces which have a maximum deviation of 45 ° with respect to a radial direction. The socket 6 has a profile 8 cooperating with the profile 7 of the plug 4 in the circumferential direction, which also has contact surfaces which have a maximum deviation of 45 ° with respect to a radial direction. In in Figure 1 illustrated embodiment are the profiles 7, 8 as Toothed shaft profiles designed, which is at least partially unchanged in the longitudinal direction of the drill string members.

A stop 9, which is shown closed in the exemplary embodiment but can also be interrupted, is formed on the drill string member 1 for the drill string member 2. With its bush 6, the drill string member 2 can rest against the stop 9 with the peripheral edge 10, which can also be interrupted, in order to transmit compressive forces in the longitudinal direction of the drill string members 1, 2.

Two through holes 11 are formed on the connector 4, which are at a defined distance from the stop 9. Two through holes 12 are formed on the bush 6 of the drill string member 2, each of which has a defined distance from the edge 10. The through holes 11, 12 are each arranged in the center parallel to one another.

In the assembled state of the drill string members 1, 2, the through holes 11 on the plug 4 are aligned with the through holes 12 on the socket 6, since the distance from the stop 9 or the edge 10 is chosen accordingly. The through holes 11, 12 form a through hole through plug 4 and socket 6, which has a different cross section over its extension.

A pull-off protection 13 can be inserted through the aligned through-holes 11, 12, which prevents the plug 4 from being pulled off the socket 6 or the socket 6 from the plug 4. Pull-off protection 13 allows tensile forces to be transmitted between the two drill string members 1, 2.

The pull-off protection 13 has a head 14 and an end 15 spaced apart from the head. A thread is formed at the end 15 of the pull-off protection 13. The length of the pull-off protection 13 with the head 14 and the end 15 is selected such that the end 15 is exposed at the end when the pull-off protection 13 is inserted and protrudes from the plug 4. The end 15 of the pull-off protection 13 can be screwed in the inserted position.

To screw off the pull-off protection 13 from the outside, a counterpart 16 is provided which has an internal thread adapted to the external thread of the end 15 of the pull-off protection 13.

The head 14 of the pull-off protection 13 can be arranged in a receptacle of the bushing 6 in such a way that the head 14 of the pull-off protection 13 lies at least partially circumferentially against a contour arranged in the bushing 6. The head 14 of the pull-off protection 13 is sunk in the receptacle in the socket 6. The counterpart 16 is in one in the Socket 6 arranged recording sunk. On the circumferential side, the counterpart 16 bears against the outer contour of the receptacle in the socket 6. Between the head 14 and the receptacle in the socket 6, a securing element 17 is arranged in the form of a wedge lock washer, which surrounds a shaft 18 of the pull-off protection 13 and bears against the head 14. The securing element 17 can prevent loosening of the screw connection between the pull-off protection 13 and counterpart 16 and / or the pull-off protection 13 and the plug. Between the counterpart 16 and the receptacle in the socket 6, a further securing element 19 is arranged, which surrounds the shaft 18 in the region of the end 15. By means of the securing element 19, loosening of the screw connection between counterpart 16 and pull-off protection 13 can be prevented.

In in Fig. 1 In the illustrated embodiment, the through holes 11 in the connector 4 are designed such that the cross section of the through holes 11 changes in the extent through which the connector 4 is connected. At the end of the connector 4, the through holes 11 are designed with a larger cross section, which decreases in the middle of the connector 4. The enlarged edge-side cross section of the through holes 11 forms an at least partial receptacle for the head 14 of the pull-off protection 13 or the counterpart 16. The head 14 of the pull-off protection 13 is thus not only in contact with the periphery of the bushing 6, but also in a peripheral region of the through hole 11. The same applies to the counterpart 16, which not only lies circumferentially in a section of the through hole 12 of the bushing 6, but also in an edge region of the through hole 11.

At the end there is an internal thread 20 in the through hole 11 in the plug 4, which can cooperate with a thread of the pull-off protection 13. The pull-off protection 13 can be inserted through the aligned through holes 12 and 11 with the securing element 17 pushed on and first screwed with a thread 20 of the plug 4. The end 15 of the pull-off protection 13 is then exposed and protrudes from the plug 4. The securing element 19 can be pushed on and the counterpart 16 can be screwed onto the end 15 of the pull-off protection 13.

The head of the pull-off safety device 13 is arranged partly in the plug 4 and partly in the socket 6, the enlarged bore being adapted to the head diameter in such a way that the head of the pull-off safety device 13 can act like a shear pin which allows the occurring ones Tractive forces (longitudinal forces) can be transmitted, for example, when pulling in pipes between plug 4 and socket 6. In the exemplary embodiment shown in the figures, the counterpart 16 is also arranged partly in the plug 4 and partly in the socket 6 and is configured similarly to the head for transmitting longitudinal forces, it also being possible for only the head or only the counterpart or neither is designed to transmit the longitudinal forces.

Claims (13)

System for connecting two drill string members (1, 2) of a drill string for earth drilling, with one drill string member (1) an end plug element (3) in the form of a plug (4) and the other drill string member (2) an end plug element (5) in Has the form of a socket (6), the plug (4) and socket (6) being designed to form a plug connection in such a way that the two drill string members (1, 2) have through holes (11) aligned with one another, through which a pull-off protection (13) is insertable, and the pull-off protection (13) has a head (14) and an end (15) spaced from the head, a thread being formed at the end (15) and the head (14) and end (15) being spaced apart from one another, that the end (15) is exposed at the end when the pull-off protection (13) is inserted. System according to claim 1, wherein the head (14) of the pull-off protection (13) is designed to interact with a tool, in particular an Allen key. System according to claim 1, wherein the head (14) of the pull-off protection (13) is at least partially retractable in a receptacle on the socket (5). System according to one of claims 1 to 3, wherein there is a counterpart (16) cooperating with the thread of the pull-off protection (13). The system of claim 4, wherein the counterpart (16) is configured to cooperate with a tool. System according to claim 4 or 5, wherein the counterpart (16) is at least partially retractable in a receptacle on the socket (6). System according to one of claims 1 to 6, wherein a shaft section is provided on the pull-off protection (13) between the head (14) and the end (15), which is designed in particular without a thread and / or the circumference of which is greater than the circumference of the end. System according to one of claims 1 to 7, wherein the through holes (11, 12) are threadless. System according to one of claims 1 to 7, wherein a thread is provided at the end of the through hole (11) of the plug (4), which is designed to interact with a thread of the pull-off protection (13). System according to one of claims 1 to 9, wherein the through holes (11, 12) extend substantially transversely to the longitudinal axis of the drill string member (1, 2) and / or are formed centrally in cross section. System according to one of claims 1 to 10, wherein the plug (4) and socket (6) each have a profile (7) which interact when plugged in. Method for connecting two drill string members (1, 2) of a drill string for drilling into the ground, the two drill string members (1, 2) being plugged into one another at the ends and being aligned such that through holes (11) arranged in the drill string members (1, 2) are aligned, wherein a pull-off protection (13) is inserted through the through holes (11), the exposed end of which can be screwed to a counterpart (16). Use of a pull-off protection (13) when connecting two drill string links (1, 2) of a drill string for drilling into the ground, the two drill string links (1, 2) being plugged into one another at the ends and being aligned so that through holes arranged in the drill string links (1, 2) (11, 12) are aligned, the pull-off protection (13) being inserted through the through holes, a pull-off protection (13) being used, the exposed end (15) of which can be screwed to a counterpart (16).

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