Patent Publication Number: US-11643880-B2

Title: Apparatus for connecting a drill pipe to the drilling drive of a drilling rig, and drilling assembly for boreholes comprising such an apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. National Stage of PCT/EP2020/085611 filed on Dec. 10, 2020, which claims priority to German Patent Application 102019134109.4 filed on Dec. 12, 2019, and German Patent Application 202019106925.2 filed on Dec. 12, 2019 the entire content of both are incorporated herein by reference in their entirety. 
     FIELD OF THE INVENTION 
     The invention relates to an apparatus for connecting a drill pipe having radially extending locking openings to the drilling drive of a drilling rig. 
     The invention further relates to a drilling assembly for ground boring, comprising a drilling drive, at least one drill pipe having radially extending locking openings and a device for connecting the drill pipe to the drilling drive. 
     BACKGROUND OF THE INVENTION 
     The apparatus mentioned hereinbefore and the aforementioned drilling assembly are used in the creation of boreholes for civil engineering works. Such rotary drilling systems are utilized, in particular, in the creation of cased bores. In the production of bores of this type, a frequent tool change is necessary. The drilling tools are driven into the ground by means of drilling or pressing pipes. It is necessary to remove the drill pipes regularly out of the borehole to remove the excavated soil out of the drilling tool and to be able to store it beside the borehole. Subsequently, the drilling tool is to be introduced into the borehole again and accordingly to extend the already achieved drilling depth further by means of drill pipes. During the creation of such a borehole, it is therefore often necessary to connect the drilling drive of a drilling rig to the aforementioned drilling and/or pressing pipes and to release it again. Herein, it often occurs that a drill pipe is held freely hanging on the drilling drive. In this state, an unintended release can lead to severe harm to humans and equipment. 
     From the prior art, numerous methods and apparatuses are therefore known for connecting drill pipes of this type to the drilling drive of such a drilling rig. 
     From DE 10023467 C1, there is known a drilling apparatus in which the connection of the drilling drive to a free end of a drill pipe is locked by means of locking bolts. For this purpose, actuating rods by means of which the locking bolts can be actuated are arranged on the outer shell of a hollow cylindrical receiving device. A disadvantage lies therein that the actuating rods that are required are situated on the outer periphery of the receiving device and so in harsh field conditions are unprotected against dirt and damage. In addition, in the event of a faulty actuation of the locking bolts, the danger exists that, during decoupling without the prior attachment of securing means, a drilling and/or pressing pipe hanging on the receiving device can fall out. 
     SUMMARY OF THE INVENTION 
     A further locking apparatus for a rotary drilling system is disclosed by DE 10 2013 020 761 B4. Herein also, locking bolts that are each adjusted positionally displaceably by means of electric motors are used. The electric motors including the drive mechanism required for the displacement of the locking bolts are arranged on the outer periphery of the tool receptacle and are thus also subject to disruption and damage, as in the case of the above-mentioned rotary drilling system. In addition, for operating the electric motors, electrical control components are required, which are also fault-prone in harsh field conditions. DE 10 2013 020 761 B4 even proposes monitoring the position of the locking bolt by means of a dedicated position monitoring system and thus to check whether each locking bolt is actually in the desired locking position. This is not only complex from the system standpoint, but also does not reduce the risk that, in the event of a possible false operation, the free-hanging drilling or pressing pipe can fall down or fall over in the absence of external support. 
     It is therefore an object of the present invention to propose an apparatus of the aforementioned type that is as robust as possible against disturbance and simultaneously reliably prevents the risk of accidental loosening of the drilling or pressing pipe from the drilling drive. It is a further object of the present invention to propose a corresponding drilling assembly for ground boring operations. 
     The object is achieved with the aforementioned apparatus for connecting a drill pipe which has radially extending locking openings to the drilling drive of a drilling rig, comprising an inner tube designed to receive a free end of the drill pipe by means of the locking opening of the drill pipe, an outer tube which at least partially encompasses the inner tube and is designed for connecting to the drilling drive, the inner tube having, at its end that connects to the drill pipe, radially extending through-recesses designed for guiding and allowing the passage of locking elements, the locking elements being arranged radially slidingly movable in the through-recesses, guide elements arranged externally on the outer tube, each forming a control gate for adjusting the radial position of the locking elements between an open position and a locking position by rotation of the inner tube relative to the outer tube, and a connecting device which is designed to connect the outer tube to the inner tube releasably in a rotationally fixed manner in that positive-locking elements are arranged extending at least partially round the circumference on the inner wall face of the outer tube and on the outer wall face of the inner tube, the positive-locking elements being designed to enter into positive-locking engagement with one another, thereby forming the rotationally fixed connections, or to reach the free-running position out of engagement, depending upon the longitudinal axial position between the outer tube and the inner tube relative to one another. 
     The apparatus according to the invention is particularly robust in relation to dirt and/or the effect of external mechanical forces. Due to the purely mechanical construction, the apparatus according to the invention comprises no sensitive components such as electrical or hydraulic actuating motors, and also no electronic assemblies. In addition, the positive-locking elements are arranged between the outer tube and the inner tube and thus are accordingly protected against external mechanical effects. A further advantage lies therein that by means of the apparatus according to the invention, the connection of a drill pipe to the drilling drive can be carried out solely at the drilling drive and by the machine operator. Thus, a rotationally fixed coupling of the drilling drive to the drill pipe only takes place if, by means of the drilling drive, a corresponding tensile or pressure force is exerted on the drill pipe and immediately, through rotation of the inner tube relative to the outer tube, by means of the guide elements, a locking with the drill pipe takes place by means of the locking elements. The connection between the drill pipe and the drilling drive is then only possible again when the respective longitudinal axial positions between the outer tube and the inner tube relative to one another are set by the operator of the drilling rig such that the positive-locking elements are in the free-running position. It is only possible for the free-running position to be reached when no or at least substantially no tensile or pressure force is exerted in the longitudinal axial direction from the drilling drive onto the drill pipe. This offers the advantage that a decoupling and/or releasing of the drill pipe from the drilling drive by means of the apparatus according to the invention is possible only if no appreciable force acts in the longitudinal axial direction between the drill pipe and the drilling drive via the apparatus according to the invention. It is therefore practically precluded that a drill pipe hanging on the drilling drive via the apparatus according to the invention can be released unintentionally, since due to the weight force of the drill pipe acting upon the apparatus according to the invention, the positive-locking elements always remain in positive-locking engagement and cannot reach the free-running position. 
     A suitable embodiment of the invention is characterized in that the positive-locking elements are a toothed rim pair with tooth profiles facing toward one another, spaced apart from one another in the longitudinal axial direction and a double toothed rim, each having a tooth profile facing the tooth profiles of the toothed rim pair. The use of the toothed rim pair and the double toothed rim as the positive-locking elements offers the advantage that both on application of pressure force and of tensile force, a rotationally fixed connection is created between the outer tube and the inner tube, so that in this state, a relative rotation between the outer tube and the inner tube is precluded due to the rotationally fixed coupling. This further offers the advantage that the locking elements situated in a locking position always remain in their position and in this way, a secure coupling with the drill pipe is guaranteed. 
     A preferred development of the invention is characterised in that the toothed rim pair is arranged on the outer wall face of the inner tube and the double toothed rim is arranged on the inner wall face of the outer tube. By way of the mutual arrangement of the toothed rim pair and the double toothed rim, respectively at the outer wall face of the inner tube and at the inner wall face of the outer tube, the precondition exists for a rotationally fixed coupling of the outer and the inner tube, provided both are in positive-locking engagement. 
     According to a further preferred development of the invention, the double toothed rim is arranged on the outer wall face of the inner tube and the toothed rim pair is arranged on the inner wall face of the outer tube. The aforementioned embodiment regarding the arrangement of the double toothed rim and the toothed rim pair represents a further advantageous embodiment of the invention. It is thus optionally possible to arrange the toothed rim pair on the outer wall face of the inner tube or on the inner wall face of the outer tube. In this case, the double toothed rim is then to be arranged on the relevant other tube. 
     A further suitable embodiment of the invention is characterised in that the tooth flank angle of the tooth profile is less than 7 degrees. The selection of the stated tooth flank angle as smaller than 7 degrees offers the advantage that on transmission of the torque between the inner and outer tubes, no propulsion takes place between the tooth profiles in the longitudinal axial direction. 
     According to a further preferred embodiment, the circumferential surface of the outer tube has recesses in the region of the guide elements. The aforementioned recesses in the circumferential surface of the outer tube give the guide elements the corresponding space to be able to pivot sufficiently far relative to one another on rotation of the inner tube and the outer tube. 
     A further suitable embodiment of the invention is characterised in that the locking elements are biased by means of spring elements such that they abut the guide elements under spring tension. Advantageously, it is thereby achieved that the locking elements are automatically moved radially outwardly on reaching the free-running position, so that they uncover the locking opening of the drill pipe and the coupling with the drill pipe is thereby automatically released. As described above, this automatic uncovering of the locking of the drill pipe only takes place when the positive-locking elements are in the free-running position so that an unintentional releasing of the drill pipe from the apparatus according to the invention is prevented in any event. 
     According to a further preferred embodiment of the invention, each of the guide elements has a gliding surface on which the head side of the locking element is slidingly guided. The gliding surfaces of the guide element each form a sliding guide with the head sides of the locking elements which is particularly robust against dirt or damage by external mechanical effects. 
     A preferred development of the invention is characterised in that the spacing between the outer wall face of the inner tube and a middle region of the gliding surface corresponds at least substantially to the length of one of the locking elements. By this means, it is ensured that in the open position, the locking elements are guided out of the locking openings of the drill pipe at least so far that said drill pipe becomes completely free from the apparatus according to the invention. 
     According to a further preferred embodiment of the invention, the gliding surface is inclined, starting from the middle region, on both sides toward the inner tube. Differently expressed, the gliding surface is configured such that it has the greatest possible spacing from the outer tube in the aforementioned middle region, while at both sides the spacing between the gliding surface and the outer tube is less. Thus, the gliding surface forms a control surface which, on rotation of the inner tube relative to the outer tube in both clockwise and anticlockwise directions, always leads to a movement of the locking elements inwardly in the radial direction. In this way, the functionality of the locking by relative rotation of the inner tube and the outer tube is brought about. 
     A further suitable embodiment of the invention is characterised in that each of the guide elements comprises lateral holding elements between which the gliding surface is arranged. The holding elements therein fulfil a double function. On the one hand, they form spacing elements in order to arrange the gliding surface with the required spacing from the circumferential surface of the outer tube. On the other hand, they form countersupport elements for the locking elements to limit the maximum possible rotation of the outer and inner tube relative to one another. 
     According to a further preferred embodiment of the invention, each locking element comprises at least one head part and at least one locking part. Differently expressed, the locking element is configured in two parts. With this two-part construction, the individual parts can be produced separately. Such separate production processes increase the flexibility in production, offer more possibilities in the design and in the application of the locking elements, in particular, it is therefore possible to exchange only the components that are subject to a high mechanical load and therefore increased wear. Thus, the forces acting during the locking process from the circumferential surface of the outer tube on the locking part are a reason to expect an increased loading of the locking part in relation to the head part and thereby more rapid wearing of the locking part. The two-part construction of the locking element enables a more targeted exchange and also an easier installation and removal of wearing parts. The replacement of the whole locking part is avoided and thereby material and costs therefor are spared. This leads to lower construction and operating costs. 
     A further suitable embodiment of the invention is characterized in that the sides of the head part and the locking part which are inclined toward one another are configured and adapted as coupling sides such that the head part and the locking part are adapted to be releasably connectable to one another in a positive and/or non-positive locking manner. In this way, the head part and the locking part can be joined together in a particularly simple manner and, if needed, separated from one another again. 
     Preferably, the head part and the locking part each have sides which permit a coupling thereof to one another. In this way, they can be joined together such that the firmness and durability thereof is equal to a locking element constructed in one part. At the same time, the connection of the head part and the locking part is releasable again at any time in order to ensure a targeted exchange of defective or worn parts and to ensure a simple installation, removal and re-installation of the head part and the locking part. 
     According to a further preferred embodiment of the invention, the coupling sides in the connected state of the head part are in releasable engagement with the locking part. 
     The releasable engagement on the one hand increases the contact area of the head and the locking part, so that the positive and/or non-positive locking engagement and therefore the cohesion of the individual parts of the locking element is reinforced and, on the other hand, the engagement is releasably constructed, so that the constituents can be separated again without destruction. A complete exchange which would otherwise be required can thereby be avoided. 
     A further suitable embodiment of the invention is characterised in that at least one securing element is designed and configured for releasable locking in place of the head part with the locking part. The securing elements ensure the locking in place of the head part and the locking part and thus bring about the firm holding of the head part and the locking part to one another. In particular, the securing element is designed to prevent an unintentional release of the connection between the head part and the locking part. Additionally, they can be released again and therefore ensure the previously described flexibility of the installation and removal and the exchange and repair of the locking element or its constituents. 
     According to a further preferred embodiment, the securing element is arranged in a plane perpendicular to the rotation plane of the drill pipe. The securing element therefore forms a blocking element which, with forces acting in the rotation plane, remains in its position. 
     Since the securing element is arranged such that it does not lie in the rotation plane, force components that act in the rotation plane do not affect the securing element such that it could become released. In this way, a reliable locking in place is always achieved, even under load. 
     According to a further preferred embodiment of the invention, the locking part has a greater surface hardness as compared with the head part. By reason of the high loading due to the sliding contact of the locking part with the circumference of the outer tube, a higher surface hardness in this component as compared with the head part is advantageous for the wear resistance, longevity and reliability of the locking part. Due to the two-part nature of the locking element, the head part which is exposed to lower mechanical wear can be constructed of a material of lower firmness. In this way, the manufacturing and replacement costs can be significantly reduced, since only one part is to be constructed of a material of higher surface hardness. 
     The invention further relates to a drilling assembly for ground boring, comprising a drilling drive, at least one drill pipe having radially extending locking openings and an apparatus for connecting the drill pipe to the drilling drive. All the advantages and preferred features of the apparatus according to the invention apply in the same way for the drilling assembly according to the invention, so that at this point, for the avoidance of repetition, including in relation to the drilling assembly according to the invention, reference is made to these. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further preferred and/or suitable features and embodiments of the invention are disclosed herein. Particularly preferred embodiments will now be described in greater detail making reference to the accompanying drawings, in which: 
         FIG.  1    shows a perspective view of the apparatus according to the invention in an unlocking state; 
         FIG.  2    shows a cut-away view of the apparatus shown in  FIG.  1   ; 
         FIG.  3    shows a perspective view of the apparatus according to the invention in the locking position under tensile loading; 
         FIG.  4    shows a cut-away view of the apparatus shown in  FIG.  3   ; 
         FIG.  5    shows a perspective view of the apparatus according to the invention in the locking position under pressure loading; 
         FIG.  6    shows a cut-away view of the apparatus shown in  FIG.  5   ; 
         FIG.  7    shows a sectional view of the apparatus shown in  FIGS.  5  and  6   ; 
         FIG.  8    shows a perspective view of the locking element according to the invention; 
         FIG.  9    shows a perspective view of the locking element shown in  FIG.  8    in plan view; 
         FIG.  10    shows a sectional view of the locking element shown in  FIGS.  8  and  9   ; 
       and 
         FIG.  11    shows a perspective view of the locking element with the direction of view toward the locking part. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The drilling apparatuses mentioned hereinbefore are well known from the prior art, so that a detailed representation thereof in the drawings is dispensed with as far as possible. The apparatus according to the invention as shown in the drawings serves on the one hand to be connected to the drilling drive of a drilling rig and on the other hand to create a connection to a drill pipe  39 —shown in the drawings only in  FIG.  7   . 
       FIG.  1    shows a perspective view of the apparatus according to the invention in the unlocking state. The apparatus according to the invention comprises an inner tube  10  which is configured and adapted to receive with its locking opening  40  a free end of the drill pipe  39 . The apparatus according to the invention further comprises an outer tube  11  which partially or completely encompasses the inner tube  10  and is also designed for connection to the drilling drive (not shown in the drawings). 
     As shown in  FIG.  2   , the inner tube  10  has, at its end  12  toward the drill connection, radially extending through-recesses  13 . The through-recesses  13  are configured and adapted to guide locking elements  14  slidingly movably in the radial direction  17 . In other words, the locking elements  14  are arranged radially slidingly movable in the through-recesses  13 . In this way, the locking elements  14  can be displaced radially inwardly to engage in the radially extending locking openings  40  (shown in  FIG.  7   ) of the respective drill pipe  39  and so to form with said bore pipe a connection that is rotationally fixed and simultaneously loadable in the axial direction  15 . 
     As shown in  FIGS.  1  and  2   , the apparatus according to the invention has guide elements  16  further externally on the outer tube  11 . As mentioned above, the locking elements  14  are arranged radially slidingly movable in the through-recesses  13 , that is, in the radial direction  17 . The guide elements  16  each have control gates  18  which are configured for adjusting the radial position of the locking elements  14  between an open position and a locking position (shown in  FIGS.  3 ,  4 ,  5 ,  6  and  7   ). The control gates  18  are adapted so that the locking elements  14  optionally reach the open or the locking position through rotation of the inner tube  10  relative to the outer tube  11 . In order to reach the locking position, the locking elements  14  are moved inwardly by means of the control gate  18  in the radial direction  17 , as show in  FIGS.  3  to  7   . In order to reach the open position, the control gate  18  enables a movement of the locking elements  14  outwardly in the radial direction  17 , as show in  FIGS.  1  and  2   . 
     In the cut-away view in  FIG.  2   , there is a clear view of a portion of the connecting device  19  which in  FIG.  1    is shown entirely covered by the outer tube  11 . The connecting device  19  is preferably configured to connect the outer tube  11  and the inner tube  10  to be both rotationally fixed and also releasable. 
     For this purpose, positive-locking elements  20  are provided, wherein on the inner wall face  21  of the outer tube  11  and on the outer wall face  22  of the inner tube  10 , the aforementioned positive-locking elements  20  are arranged extending at least partially round the circumference. The inner tube  10  and the outer tube  11  are configured to be displaceable relative to one another in the axial direction  15 —mechanically limited only by the positive-locking elements  20 . Otherwise expressed, the respective longitudinal axial positions between the outer tube  11  and the inner tube  10  relative to one another can be changed. Otherwise expressed, the outer tube  11  and the inner tube  10  can be displaced relative to one another in their longitudinal axial position. 
     In the unlocked state shown in  FIGS.  1  and  2   , the positive-locking elements  20  are in the free-running position, and so they are out of engagement with one another. In this case, there is no rotationally fixed connection between the positive-locking elements  20 , so that the inner tube  10  and the outer tube  11  are not connected to one another in a rotationally fixed manner. 
     The positive-locking elements  20  enter into positive-locking engagement with one another if—as shown in  FIG.  4   —the inner tube  10  is displaced relative to the outer tube  11  in the tensile direction  23 . This state arises, for example, if a tensile force is exerted on the drill pipe  39  by the drilling drive (not shown in the drawings). As  FIG.  4    shows, the two upper positive-locking elements  20  enter into positive-locking engagement with one another and thereby form a rotationally fixed connection between the inner tube  10  and the outer tube  11 . 
     In a similar manner, the two lower positive-locking elements  20  enter into interlocking engagement with one another if the inner tube  10  is displaced relative to the outer tube  11  in the pressure direction  24 . This state arises, for example, if a pressure force is exerted on the drill pipe  39 . 
     It is apparent that the positive-locking elements  20  are designed to enter into positive-locking engagement with one another, depending upon the position of the inner tube  10  relative to the outer tube  11  in the axial direction  15 , that is, either on a displacement of the inner tube  10  relative to the outer tube  11  in the tensile direction  23  or in the pressure direction  24 . Thus, in each of the longitudinal axial positions, a rotationally fixed connection is brought about between the inner tube  10  and the outer tube  11 . A decoupling of this rotationally fixed connection between the inner tube  10  and the outer tube  11  takes place when the positive-locking elements  20  are in the free-running position. 
     Preferably, the positive-locking elements  20 —as shown in the drawings—are designed as a toothed rim pair  25  and a double toothed rim  26 . The toothed rim pair  25  has tooth profiles  27  spaced apart from one another in the longitudinal axial direction and facing one another. Arranged between these toothed rim profiles  27  is the double toothed rim  26  with its tooth profile  28  which corresponds to each of the tooth profiles  27  of the toothed rim pair  25 . Further preferably, the toothed rim profiles  27  and the toothed rim profile  28  are configured corresponding with regard to their geometry such that the positive-locking engagement described above takes place in the middle position between the inner tube  10  and the outer tube  11 . 
     Further preferably—as shown in the drawings—the toothed rim pairs  25  are arranged on the outer wall face  22  of the inner tube  10  and the double toothed rim  26  is arranged on the inner wall face  21  of the outer tube  11 . Otherwise expressed, the toothed rim pair  25  forms one structural unit with the inner tube  10 , whilst the double toothed rim  26  forms one such unit with the outer tube  11 . In a further advantageous embodiment—not shown in the drawings—of the present invention, the double toothed rim  26  is arranged on the outer wall face  22  of the inner tube  10  and the toothed rim pair  25  is arranged on the inner wall face  21  of the outer tube  11 . 
     Preferably, the tooth flank angle of the tooth profile is less than 7 degrees. This means that the respective tooth flank angle of the toothed rim profile  27  and of the toothed rim profile  28  do not exceed the aforementioned angular quantity. Through the selection of the specified tooth flank angle, it is always ensured that a torque that acts from the inner tube  10  to the outer tube  11  and vice versa does not lead to any generation of pressure or tensile forces in the axial direction  15 . 
     The circumferential surface  29  of the outer tube  11  has recesses  30  in the region of the guide elements  16 , so that in the region of these recesses  30 , the locking elements  14  enter through the outer tube  11 . The size of the recesses  30  also determines the maximum pivot angle through which the inner tube  10  can be rotated relative to the outer tube  11  before a further rotation of the two tubes relative to one another mechanically blocks a further relative pivoting through a collision of the connecting elements  14  with the circumferential surface  29  of the outer tube  11  to both sides. 
     Further preferably, the locking elements  14  are spring-biased by means of spring elements  31 . The spring-biasing thereby generated serves to press the locking elements  14  against the guide element  16  and automatically to force said guide element outwardly in the radial direction  17 . 
     Preferably, each of the guide elements  16  comprises a gliding surface  32 . The head side  33  of the locking elements  14  is slidingly guided on this gliding surface  32 . The gliding surface  32  thus causes the movement of the locking elements  14  in the radial direction  17  dependent upon its radial distance. 
     Preferably, the spacing  35  between the outer wall face  22  of the inner tube  10  and a middle region  34  of the gliding surface  32  is selected so that it corresponds to the length of one of the locking elements  14  and/or substantially to the length of one of the locking elements  14 . The spacing  35  is thus optimally configured so that the locking elements  14  in the unlocked position—shown in  FIG.  2   —are positioned just far enough outwardly in the radial direction  17  so that they no longer protrude on the inside of the inner tube  10  from the through-recess  13 . Advantageously, the locking elements  14  are not guided only by the through-recesses  13 , but are also mounted slidingly movable in corresponding guide sleeves  36 . 
     According to a further preferred embodiment of the invention, each gliding surface  32  is inclined on both sides  37 , starting from the middle region  34 , tilted toward the inner tube  10 . Otherwise expressed, the gliding surfaces  32  are configured such that they are furthest removed from the inner tube  10  in their middle region  34  by the spacing  35  and are inclined to both their sides  37  toward the inner tube  10 , that is, they have a smaller spacing from the inner tube  10  there than the radial spacing  35 . 
     Preferably, each of the guide elements  16  comprises lateral holding elements  38  between which the gliding surface  32  is arranged. The holding elements  38  fulfil a double function, that is, on the one hand they serve as a holder for the gliding surface  32  and on the other hand form a countersupport for the locking elements  14  for delimiting the maximum relative rotatability between the inner tube  10  and the outer tube  11 . 
       FIG.  8    shows a perspective view of the locking element  14  according to the invention. The locking element  14  comprises a head part  41  and a locking part  42  which is preferably designed to be cylindrical. The head part  41  comprises the head side  33  of the locking element  14  and thus forms a head side  33  facing away from the locking part  42  and interacting with the gliding surface  32 . The free end of the locking part  42  has a locking head  43  which, as the drawing shows, is conically formed and/or chamfered. 
     The sides—not explicitly shown in the drawings—of the head part  41  and the locking part  42  that face toward one another are configured and adapted as coupling sides such that the head part  41  and the locking part  42  are configured to be releasably connectable to one another in a positive and/or non-positive locking manner. For example, for this purpose, in the side of the head part  41  facing the locking part  42 , a recess is provided into which the side of the locking part  42  facing the head part  41  engages exactly fittingly or with a slight oversize to achieve a tight seating to form a compound part. The coupling sides can be released from one another again if needed, and therefore engage releasably with one another. 
     As shown in  FIG.  8   , the head part  41  has a bore  45  which is configured and adapted for receiving a securing element  44 . The securing element  44  is preferably configured as a securing pin, for example, in the form of a split hollow cylinder. Preferably, the diameter of the securing pin is selected to be slightly greater than that of the bore  45 , so that the securing pin is automatically held in the bore  45  with tight seating, but for removal of the securing element  44 , is designed able to be driven out. Optionally, the locking part  42  is configured tapering toward the head part  41 . 
     As  FIG.  10    shows, the locking part  42  also has a transverse bore—not shown in detail in the drawing—which is arranged such that, in the connected state of the head part  41  and the locking part  42 , as shown, said transverse bore aligns with the bore  45 . In this way, the bore  45  together with the transverse bore of the locking part  42  forms a through receiving space for the securing element  44 . In this way, the securing element  44  introduced into the through receiving space locks the locking part  42  in place with the head part  41  against unintended release. It is not necessarily required that the transverse bore of the locking part  42  is configured as a through recess. Alternatively, two countersink bores can be provided in extension of the bore  45 . For locking in place, one of the securing elements  44  is then introduced into each of the countersink bores. 
       FIG.  11    shows a perspective view of the locking element  14  from the front in a perspective view toward the locking head  43 . Optionally, the head part  41  has recesses on oppositely arranged end faces to receive a sighting aid  46 . Preferably, the recesses are designed as countersink bores. The sighting aids  46  serve a machine operator for easy recognition of the respective positions of the locking element  14 . Further preferably, the sighting aids  46  are designed similarly to the securing elements  44 . 
     The invention also relates to a drilling assembly—not shown in detail in the drawings—for ground boring operations, which comprises a drilling drive and at least one drill pipe  39 —shown in  FIG.  7   —with radially extending locking openings  40 . This drilling assembly also has the apparatus according to the invention described above for connecting the drill pipe  39  to the drilling drive, having the aforementioned features. The advantages and functions of the apparatus according to the invention for connecting the drill pipe  39  to the drilling drive have been set out in detail above and apply in the same way for the drilling assembly according to the invention.