Threaded connection

0001The invention relates to a threaded plug, a threaded bushing, a use of a threaded plug, a use of a threaded bushing and a threaded connection with a threaded plug and a threaded bushing, wherein the described entities can be designed for an earth drilling device.

0002The term "earth drilling device" refers to devices with which the drive power of a drive device is transmitted via a rod to a tool that is arranged on a rod, in particular at the end. This includes in particular earth drilling devices with which earth bores and in particular horizontal bores are made in the ground. In this case, the drive device usually transmits thrust or pressure forces via the rods to the tool designed as a drill head. It is also possible for a rotary movement to be imposed on the rods around their longitudinal axis using the earth drilling device. Using the earth drilling devices, existing boreholes in the ground or in the ground can be drilled. old pipes that have already been laid can be widened or pulled out and, if necessary, a new pipe can be pulled in at the same time. The earth drilling devices are often designed in such a way that they can be used both for creating earth bores and for pulling work, ie for widening an existing bore or an old pipe or for pulling in a new pipe. This makes it possible to first create a pilot bore using the same earthwork device, whereby a pilot drill head is pushed through the ground until it reaches a target excavation pit, and the pilot drill head is replaced in the target excavation pit by an expander head, whereby the pilot bore is expanded when the drill rod is pulled back. If necessary, a new pipe attached to the expander head can be pulled into the expanded earth bore at the same time as the expander head.

0003The rods of such earthwork devices usually consist of a number of rod sections, which are gradually connected to one another in accordance with the drilling advance. The individual rod sections are connected via coupling elements, whereby in addition to plug-in couplings, as in<patcit id="pcit0001" dnum="DE19608980"><text>DE 196 08 980</text></patcit> described, especially screw connections are widely used. The main advantages of screw connections are the low costs associated with their production and the possibility of having the screwing carried out in a simple, automated manner. A major disadvantage of screw connections, however, is that they often represent the greatest weak points of the rod, which is due to the relatively small diameter in the area of ​​the threaded plug of the threaded connection as well as the geometrically high notch effect of the thread itself.

0004Out of<patcit id="pcit0002" dnum="EP2334892B1"><text>EP 2 334 892 B1</text></patcit> A threaded connection is known in which the external thread of a threaded plug is designed in such a way that flanks of this external thread form a section of an ellipse. By designing the flanks in the form of a section of an ellipse, a constantly changing flank angle is achieved, through which an optimized contact can be achieved between the flanks of the threaded plug and the corresponding flanks of an internal thread of a corresponding threaded bushing. The threaded plug and threaded bushing are designed accordingly.

0005API threads and round threads according to DIN 20 400 are also known. However, the service life of such thread forms has proven to be too short in the daily operation of earth drilling devices.

0006Alternative thread forms have therefore been developed which are especially designed for the specific loads on the rods that occur in earth drilling devices.<patcit id="pcit0003" dnum="DE19803304A1"><text>DE 198 03 304 A1</text></patcit> discloses a threaded connection with which rod sections of a drill rod are to be connected, whereby the drill rod is to be used in particular for rotary percussion drilling. The essential features of these threaded connections are the asymmetrical shape of the thread with different pitch angles of the flanks that bear the load during rotary percussion drilling and the non-load-bearing flanks, as well as the provision of a threadless insertion section. The non-load-bearing flanks should also be circular in shape. The<patcit id="pcit0004" dnum="DE19803304A1"><text>DE 198 03 304 A1</text></patcit> The known threaded connection has proven to be insufficiently robust in daily operation.

0007From the<patcit id="pcit0005" dnum="EP0324442B1"><text>EP 0 324 442 B1</text></patcit> and the<patcit id="pcit0006" dnum="US5060740A"><text>US Patent 5,060,740</text></patcit> Asymmetrical threaded connections are also known which were designed for use in connecting rod sections of earth drilling devices. The threaded connections disclosed in these publications are characterized by the fact that the thread root forms a section of an ellipse. This is intended to enable a transition from the thread root to the flat flanks of the thread with as little stress as possible.

0008Also from the<patcit id="pcit0007" dnum="WO2006092649A1"><text>WO 2006/092649 A1</text></patcit> Threaded connections for rods of earth drilling devices are known in which the thread root forms a section of an ellipse. The thread shapes disclosed in this publication can be both asymmetrical and symmetrical.

0009Although particularly with the<patcit id="pcit0008" dnum="EP2334892B1"><text>EP 2 334 892 B1</text></patcit> Although good results can be achieved with a known thread shape, it has been shown that forming and releasing the connection requires more precise handling.

0010Based on this prior art, the invention was therefore based on the object of creating a threaded connection which, in particular, facilitates the formation and release of the connection and whose service life is impaired as little as possible or not at all.

0011This object is achieved by the subject matter of the independent patent claims. Advantageous embodiments are the subject matter of the respective dependent patent claims and emerge from the following description of the invention.

0012According to the core of the invention, the idea of ​​only having to take into account a reduction in the notch effect and wanting to achieve a more homogeneous stress distribution was abandoned, which is why an elliptical shape was previously provided at the thread root. Due to the elliptical shape, the stress maxima occurred less in the thread root than in the area of ​​the flanks. Until now, the perfect thread shape was assumed to be a simple elliptical design, as this has a positive effect on the service life of the threaded connection. In particular, in the field of rod sections for earth drilling devices, the elliptical shape has been retained. The considerations were based on the fact that there was usually no geometric notch in the area of ​​the flanks and the notch effect in the thread base was therefore reduced. According to the invention, it has now been recognized that it is not only the thread root and an extension to the further flank course that are important, but also the design of the flank in the further course at a distance from the thread root. The invention is based on a section of the flank in which the tangent applied to a respective point of the section has an angle to the cone on which the thread is applied that is greater than 45°. The invention extends or changes the design of at least one section of the flank to adapt the geometry of the flank itself, whereby according to the invention, a section of the flank that comes into contact with the other screw element is considered in particular. According to the invention, the design of the flanks for a threaded plug and/or a threaded bushing was changed in such a way that the shape of an ellipse was deviated from. According to the core idea of ​​the invention, the section of the flank is curved and has a significant portion of the thread height in which the angle to a connecting line of adjacent thread roots and/or thread crests is greater than 45°. This makes it possible to obtain an efficient force transmission of the screw connection, wherein the advantageous properties of a shape that is curved at least in the section of the flank can be used. This function makes it possible to extend the shape to the thread root or close to the thread root in order to reduce stresses in the thread root.

0013According to the core idea of ​​the invention, a completely different approach is chosen compared to the prior art. While in the prior art the shape of the thread root was extended to the flank in the direction of a thread crest, in the present case the shape of the flank can be extended to the thread root. Surprisingly, it has been shown that the shape provided for the flank also enables an improvement to reduce stresses in the thread root. Improved power transmission, improved sliding and/or a reduction in stresses in the thread root can be achieved, so that damage to the thread due to shearing or deterioration of the thread guidance, which is colloquially referred to as cold welding of the thread, and/or a notch effect in the thread root can be counteracted.

0014It may seem paradoxical at first that a screw connection that has been known for decades and whose main function is to elastically clamp two parts by means of positive and non-positive locking is not already known in the way proposed here, but the good results achieved so far may have justified sticking to the shapes used so far, in particular the elliptical shape.

0015By means of the above-mentioned form, the operating forces and operating moments can be reliably absorbed and the screwing can be more successful, and on the other hand, a thread form that is easy to construct and whose manufacture or production can surprisingly be carried out without major difficulties can be used.

0016It was recognized by the invention that, especially for a conical thread, a force is present that can be perceived as "pre-tensioning" because there is a gap between the threaded bushing and the threaded plug when initially screwing, although the threads of the threaded bushing and the threaded plug are already congruent. When screwing further, a resulting normal force is generated, which increases the frictional force in the thread. This can lead to part of the screwing torque being absorbed by friction. The overlap that already exists during the initial screwing can lead to the threaded bushing and threaded plug sliding against each other, as the "preload" in the axial direction causes a radial movement due to the cone angle. In order to ensure that sliding can take place over as large a surface area as possible in order to distribute the surface pressure accordingly, it was recognized that the shape of the thread should be designed with a significant section in the thread height, the tangents of which in this area enclose an angle with a connecting line between adjacent thread roots or thread crests that is greater than 45°. The area with a "pitch" of greater than 45° has a height that is at least 0.3 times the thread height, where the pitch is an angle of the section of the function that a tangent at the point of the function encloses with a connecting line between adjacent thread roots or thread crests.

0017The shape described makes it possible, for example, to have a greater pitch or angle over a longer area than, for example, an ellipse, on the surfaces where the thread is applied, particularly in the area with a pitch of more than 45°. Despite previous reservations about this type of shape, it is easy to manufacture. The shape can also be easily planned during construction. An extension to the thread root against the background of an improvement or reduction of stresses in the thread root can be achieved due to the described shape, whereas an ellipse only allows for a limited design option.

0018The invention provides a threaded plug on an elongated body for a threaded connection with a threaded bushing, wherein the threaded plug has a conical external thread, in which a section of a flank of the external thread can be represented as a section of a function which has a curvature, wherein the section of the function forms an angle to a connecting line of adjacent thread roots or flanges over at least a height of 0.3 times the thread height. has thread crests that are greater than 45°.

0019The term "conical (internal or external) thread" includes a design of the (internal or external) thread such that the thread roots and/or the thread crests of the threaded plug or threaded bushing define a jacket that has a conical shape. This allows the threaded plug to be screwed onto the threaded bushing quickly and easily, with both the threaded plug and the threaded bushing preferably having a conical thread. Preferably, the angle that the casing, on which the thread roots and/or thread crests lie, encloses with a parallel to the longitudinal axis of the threaded plug or the threaded bushing (cone angle) can be in the range between 2° and 15°, in particular 2° to 12°, in particular 3° and 12°, more preferably 3° to 10°, more preferably 3° to 8°, more preferably 3° and 7°.

0020It is possible that not all thread roots and/or thread crests are taken into account when considering the cone, but for example only two or more adjacent thread crests and/or thread roots. In this way, a slight variation in the cone and/or manufacturing tolerances over the length in the direction of the longitudinal axis of the elongated body can be taken into account. It is also possible that all thread roots and/or thread crests are located on one shell or cone.

0021As a rule, the shape of the thread is examined in the sense of the description in a sectional view, in which the threaded plug or, analogously, the threaded bushing is cut by a cutting plane that intersects the longitudinal axis of the elongated body or that contains the longitudinal axis. This allows the examination to be carried out in a two-dimensional representation, so that the cone angle is derived from a connecting line of the thread roots or the thread socket. of the thread crests in the sectional view; it can be provided that the cone angle is (locally) given by a connecting line between adjacent thread roots or adjacent thread crests.

0022For the purposes of the description, the term "flank" of the thread essentially includes the area or section of the thread between the thread root and the adjacent thread crest and vice versa. Due to the curved design of the flank section, it can be provided that the allocation of the areas of the "thread root" and the "thread crest" are not necessarily reduced to one point, since the thread root and/or thread crest can, for example, form a plateau or a valley. have an area with a very low pitch. The terms "thread root" and "thread crest" are described in more detail below.

0023For the purposes of the description, the term "section of a flank" includes a partial area or section of the thread between a thread root and an adjacent thread crest and vice versa.

0024In the sense of the description, the term "section of a function" includes a function curve or (function) graph over an argument or value range. The term "section of a function" includes a region of a curve described by means of a function, in particular a mathematical function.

0025In the sense of the description, the term "function" includes a mapping or a relationship between two sets that assigns exactly one element of the other (second) set to each element of one (first) set. In the present case, a height of the flank (y-value or y-axis) can be assigned to a length or a point on a longitudinal axis (x-value or x-axis), which can be, for example, the longitudinal axis of the elongated body or a straight line connecting the thread roots. For the purposes of the description, the term "function" includes a unique assignment or relationship; an element of the first set is assigned only one element of the second set, in particular not two elements. The unique assignment or relationship can be described or expressed using a mathematical function, in particular a calculation rule. By representing a section of the flank as a function, simple planning, design and/or manufacturing can be achieved. In particular, the term "function" can be contrasted with a parametric representation or a shape that cannot be represented by a function. For example, usually and especially within the scope of this description, a circle cannot be represented as a function, so a circular section that can adjoin the section of the function for the flank is to be seen as a supplement to the section of the flank that can be represented as a function. For the purposes of the description, the term "function" includes a configuration that is not circular.

0026In contrast to the prior art, the invention has recognized that the description of the flank or the representation of the flank as a function is important and has thus moved away from the idea of ​​designing a flank, for example, essentially as an ellipse(s) and/or circle(s). The design of a flank can essentially be represented as a function that is neither a circle nor an ellipse. The term "function" takes into account the different design compared to a circle or several circles or an ellipse or several ellipses and/or mixed forms of these. It is not excluded that the section of the flank that can be represented as a function is followed by a section that is designed as a circular section. Unlike in the prior art, an additional shape, if present - for example in the form of a circular section - may indeed be present, but can essentially be arranged in the flank at such a point that there is essentially no contact when the screw connection is loaded with the counter element.

0027Describing a section or a region of a flank as a section of a function can create the advantage that gradients can be flexibly adjusted - especially unlike circles or ellipses.

0028In the sense of the description, it can be provided that the section of the flank that can be represented as a function is the section that comes into contact with the counter element in the screwed state. In particular, it can be provided that the section of the flank that can be represented as a function has a significant proportion of the supporting flank in the loaded case of the screw connection. The high proportion can be reflected in the fact that the function extends over a large area between the thread root and the thread crest (continuous); it can be provided that the function extends over a range of substantially 0.4 to substantially 0.9 times the length between the thread root and the adjacent thread crest, in particular over a range of substantially 0.5 to substantially 0.9 times the length between the thread root and the adjacent thread crest, in particular over a range of substantially 0.6 to substantially 0.9 times the length between the thread root and the adjacent thread crest, in particular over a range of substantially 0.65 to substantially 0.85 times the length between the thread root and the adjacent thread crest, in particular contiguously.

0029The term "thread root" in the sense of the description can include the lowest point between two adjacent thread crests, from which in particular a flank can extend to one of the two adjacent thread crests. If the deepest point between two adjacent thread crests is described as being comprised of the thread root, the thread root within the meaning of the description does not have to be reduced to a single point, in particular the deepest point between two thread crests. Rather, a thread root within the meaning of the description can extend over an area that is extended in the direction of the longitudinal axis of the elongated body or the threaded plug or. of the threaded bushing and can include the lowest point between two adjacent thread crests. The thread root can be plateau-shaped or designed as a plateau, whereby a slight or minor curvature can be present. A punctual or almost punctual design of the thread root is not excluded; in particular in the case of a punctual or In the case of an almost point-like design, it can be provided that a shape for forming a flank is connected to the thread root designed in this way, which can be determined, for example, by the section of the function, a circle radius or other parameters. It can be provided that the thread root indicates the point at which a supporting and a non-supporting flank meet.

0030The term "thread crest" can, within the meaning of the description, include the highest point between two adjacent thread roots. If the highest point between two adjacent thread roots is described as being included in the thread crest, the thread crest within the meaning of the description does not have to be reduced to a single point, in particular the highest point between two thread roots. Rather, a thread crest in the sense of the description can extend over an area that is extended in the direction of the longitudinal axis of the elongated body or the threaded plug or the threaded bushing and can include the highest point between two adjacent thread roots. The thread crest can be plateau-shaped or designed as a plateau, whereby a slight or slight curvature can be present. A point-like or almost point-like design of the thread crest is not excluded; in particular in the case of a point-like or almost point-like design, it can be provided that the thread crest designed in this way is followed by a shape for forming a flank, which can be defined, for example, by the section of the function, a circle radius or other parameters. It may be provided that an area is counted as the thread crest, which may extend from a highest point to a turning point in the flank. It can also be provided that a flank extends from the thread tip in a section of a circular shape, in particular a section of a circle with a radius, to the section of the function, so that the section of the circular shape, in particular the section of a circle with a radius, can directly adjoin the section of the function. It may be provided that the thread crest indicates the point at which a load-bearing and a non-load-bearing flank meet.

0031To describe the function, an X-axis can be laid or positioned such that the X-axis is essentially a connecting line of the thread roots. It is preferred to lay or position the X-axis such that the X-axis essentially coincides with the longitudinal axis of the elongated body or runs parallel to it. In both cases, the design, manufacture and/or planning can be simplified. In the latter case, it is not necessary to tilt a function around an axis, but the function can be used as such.

0032The term "(thread) height" to describe the thread includes the specification of a distance or length related to a cutting plane for viewing the thread, which can contain the longitudinal axis of the elongated body. The (thread) height can result from a length or distance between the thread root and adjacent thread crests, whereby a cone on which the thread crests are arranged can be taken into account. To determine the thread height, it may be provided that the perpendicular is dropped from a connecting line connecting the thread crests to the thread root or a connecting line between adjacent thread roots.

0033For the purposes of the description, a tangent at the respective point of the flank or function is considered when considering the angle that the flank or function has with the connecting line of adjacent thread roots or thread crests.

0034It can be provided that the section of the function describes the flank over a large area in relation to the longitudinal axis of the elongated body or the threaded plug or threaded bushing. It can be provided that the flank essentially has the section of the function except for roundings, "additional pieces" and/or "connecting areas". The section of the function can form a significant part of the flank. It may be provided that an area adjacent to the section of the function is designed to be as small as possible.

0035It is possible for the section of the function to extend into the thread root. It is possible for the section of the function to describe the thread root for the corresponding flank, to which the further flank adjacent to the thread root can be connected. The part of the thread root of the flank that the section of the function affects can be designed as the section of the function. At the thread root, up to which the section of the flank described by the section of the function can extend, a different shape can be provided for the adjacent flank with the same thread root; for example, the section of the function can connect to the other shape in the thread root. In particular, the adjacent flank can be designed to be non-mirror-symmetrical to the flank with the section of the function. It can be provided that the section of the function can extend from the area with an angle greater than 45° to the thread root. However, it is also possible to provide a different shape than the section of the function for the thread root or the area around the thread root.

0036If it is described that a section of the flank is designed as a section of a function, then in the sense of the description in a preferred embodiment this is understood to mean that the section of the flank has exactly the section of the function and no other shape. It can be provided that the thread between two adjacent thread crests can be composed of several sections of more than one function.

0037The shape of the thread root and the thread crest can be formed by the section of the function, another section of another function or shape, or several sections of other functions or shapes. It is possible that the thread root and/or thread crest, in particular directly adjacent to the section of the function, have a shape which can be described in particular by a mathematically describable shape, preferably a circular section, more preferably a circular section.

0038In a preferred embodiment, the section of the function has a height of at least 0.35 times, in particular at least 0.4 times, in particular at least 0.45 times, in particular at least 0.5 times, in particular at least 0.55 times, in particular at least 0.6 times, in particular at least 0.65 times, in particular at least 0.7 times, in particular at least 0.75 times, the thread height has an angle to a connecting line of adjacent thread roots or thread crests that is greater than 45°. This allows the effect according to the invention to be varied, in particular increased.

0039It can be provided that an angle of the section of the function is not greater than 75°, in particular not greater than 70°, in particular not greater than 65°. In this respect, the section of the function can be restricted in such a way that the section of the function has a height of at least 0.3 times, in particular at least 0.35 times, in particular at least 0.4 times, in particular at least 0.45 times, in particular at least 0.5 times, in particular at least 0.55 times, in particular at least 0.5 times, in particular at least 0.6 times, in particular at least 0.65 times, in particular at least 0.7 times, in particular at least 0.75 times the thread height, has an angle to a connecting line of adjacent thread roots or thread crests that is greater than 45° and less than 75°, in particular less than 70°, in particular less than 65°. The section of the function can be designed to increase monotonically over the relative thread height under consideration. A derivative of the section of the function can be designed to increase monotonically over the relative thread height under consideration. By means of the section of the function, a large range can be created with regard to the thread height in which the angle changes over a maximum of 20°, in particular a maximum of 25°, in particular a maximum of 30°. A contact angle can be selected which can be varied or is varied by the function, but over a significant range the contact angle remains in a desired range. Design and handling can be improved.

0040In a preferred embodiment, a length range of the section of the function which has an angle to a connecting line of adjacent thread roots or thread crests which is greater than 45° extends over a length between thread root and thread crest which is 0.1 times the length between thread root and thread crest of the flank whose section can be represented by the section of the function. This allows not only a height of the described area to be taken into account, but also a length that can be varied accordingly, in particular increased. In a particularly preferred embodiment, the length range of the section of the function that forms an angle to a connecting line of adjacent thread roots or has thread crests that are greater than 45°, extend over a length between thread root and thread crest that is 0.15 times, in particular 0.2 times, in particular 0.25 times, the length between thread root and thread crest of the flank, the section of which can be represented by the section of the function.

0041In the aforementioned length range, the angle can vary up to a maximum of 75°, in particular a maximum of 70°, in particular a maximum of 65°, in particular a maximum of 60°, wherein an aforementioned embodiment can be provided with regard to a monotonically increasing course of the section of the function and a monotonically increasing course of the derivative of the section of the function.

0042For the purposes of the description, the term "length range" includes a range that extends in the direction of or along a longitudinal axis of the elongated body, the threaded plug or the threaded bushing, or in particular along a connecting line between adjacent thread roots or thread crests. If a longitudinal axis or connecting line is described with regard to the length range, the term "in the direction of" or "along" a direction essentially parallel to the longitudinal axis or the connecting line. If a thread crest is designed as a plateau, the thread crest can be positioned or arranged or defined on or at the plateau to determine a length in such a way that the thread crest is a point on the flank that describes the edge of the plateau (the first point that is at the level of the plateau). The choice of the length of the plateau can be advantageous.

0043In a preferred embodiment, the section of the function extends in a region around the center of the thread height, which has at least 0.2 times the thread height, wherein the region is designed such that the angle of the section of the function in the region to a connecting line of adjacent thread roots or thread crests changes by less than 20°, in particular 15°. This can further support the core idea. In a particularly preferred embodiment, the aforementioned range can be at least 0.25 times, in particular 0.3 times, in particular 0.35 times, in particular 0.4 times, in particular 0.45 times, in particular 0.5 times, in particular 0.55 times, in particular 0.6 times, the thread height.

0044When considering the section of the function in an area around the middle of the thread height, the middle is determined and it is seen how far the section of the function extends from the middle to both the thread root and the thread crest in relation to the thread height. The smaller extent of the extension from the middle to the thread crest or middle to the thread root is multiplied by two. The chosen consideration can take into account an asymmetrical arrangement of the flank section. For example, the height of the section that adjoins the function to the thread root can be significantly smaller - or non-existent - than the height of the section that adjoins in the direction of the thread crest.

0045In the aforementioned range of the thread height, the angle can vary up to a maximum of 75°, in particular a maximum of 70°, in particular a maximum of 65°, wherein an aforementioned configuration can be provided with regard to a monotonically increasing course of the section of the function and a monotonically increasing course of the derivative of the section of the function.

0046It can be provided that the information on the extension of the section of the flank that can be described by means of the function supplements each other in such a way that the function extends over a length range and a thread height, so that a ratio of extension over thread height and extension over length range results, which is in the range from 1 to 4. There may be a synergistic effect here by correlating the extension ratio with the angle achieved with the function for contact formation.

0047A ratio of extension over thread height and extension over length range can be selected which is in particular in the range of 1 to 4, more preferably 1.2 to 4, more preferably 1.3 to 3.9, more preferably 1.3 to 3.8, more preferably 1.3 to 3.7, more preferably 1.3 to 3.6, more preferably 1.3 to 3.5, more preferably 1.3 to 3.4, more preferably 1.3 to 3.3, more preferably 1.3 to 3.2, more preferably 1.3 to 3.1, more preferably 1.3 to 3.0, more preferably 1.3 to 2.9, more preferably 1.3 to 2.8, more preferably 1.3 to 2.7, more preferably 1.3 to 2.6, more preferably 1.3 to 2.5, more preferably 1.3 to 2.4, more preferably 1.3 to 2.3, more preferably 1.3 to 2.2, more preferably 1.3 to 2.1, more preferably 1.3 to 2.0, more preferably 1.4 to 2.0, more preferably 1.5 to 2.0. It may be provided that the ratio 1.0 is correlated with 45°, the ratio 4.0 with 75°, the ratio 1.5 with 56° and the ratio 2.0 with 63°.

0048In a preferred embodiment, the flank extends over a length from the thread root in the direction of a thread crest over a region in which the angle to a connecting line of adjacent thread roots or Thread crests are smaller than 20°, which is greater than 0.1 times, in particular 0.15 times, in particular 0.2 times, in particular 0.25 times, in particular 0.3 times, in particular 0.35 times, in particular 0.4 times, the length between the thread root and the thread crest of the flank, the section of which can be represented by the section of the function. In this way, the core idea of ​​the invention can be improved or can be further enhanced by counteracting the notch effect at the thread root. A synergistic effect can result.

0049In a preferred embodiment, the section of the function extends into the area of ​​the thread root, in particular into the thread root, whereby the function can embody the properties described in the description. This can result in a synergistic effect that the described properties can be realized with the function, which can enable good planning or construction and good manufacturability.

0050In a preferred embodiment, the curvature is curved inwards, whereby the inward curvature previously designed for the elliptical shape can be retained conceptually.

0051For the purposes of the description, the term "inwardly curved" or "inwardly curved" or "convex" is to be understood as meaning a configuration in which the shape is such that the shape lies below one or each line of connection between two points of the shape.

0052In a preferred embodiment, the flank, the section of which can be represented as the section of the function, has the section of the function and a further shape that connects the section of the flank with the thread crest. This allows a certain degree of variability to be achieved. It can be provided that the flank can have further, different areas or shapes in addition to the section of the function. It can be intended that the flank has or consists of exactly one section of the function and exactly one other form. Simple planning and construction is possible in addition to good manufacturability.

0053In a preferred embodiment, the section of the function is continuous. This can counteract a notch effect. The continuous course also enables a simple design with good production.

0054It can be provided that the section of the function is a section of a hyperbolic function. In particular, the hyperbolic function can be rotated by approximately 45°, in particular 45° reduced by the cone angle.

0055In a preferred embodiment, the function is a power function with an exponent less than 1 and a base with a power argument. Such functions are well known in this field despite a surprising use and can be varied within a certain range in such a way that very good results can be achieved.

0056In the sense of the description, the term power function with an exponent less than 1 basically includes a function of the form<maths id="math0001"><math display="block"><mi mathvariant="normal">e</mi><mn>1</mn><mfenced><mi mathvariant="normal">x</mi></mfenced><mo>=</mo><msup><mfenced><mi>factor</mi><mo>*</mo><msup><mi mathvariant="normal">x</mi><mo>∧</mo></msup><mi>power</mi><mo>+</mo><mo>/</mo><mo>−</mo><mi>Adjustment</mi></mfenced><mo>∧</mo></msup><mi>exponent</mi><mo>+</mo><mo>/</mo><mo>−</mo><mi>shift</mi><mo>,</mo></math><img file="EP4403742A2_D0001.tif" /></maths><ul id="ul0001" list-style="none" compact="compact"><li>where factor is a real number,</li><li>Power a real number,</li><li>Adjustment a real number,</li><li>Exponent is a real number less than 1 and</li><li>Displacement is a real number.</li></ul>

0057In a preferred embodiment, the exponent is in the range from 0.2 to 0.7, in particular from 0.3 to 0.6, and/or the base which is raised to a power has a term in which the argument is raised to a power which is in the range between 2.5 and 5.8, in particular between 2.7 and 5.6, in particular between 2.9 and 5.4. This makes it possible to use a function that is relatively simple in structure and yet allows for a design and/or variability that underlines or supports the core idea of ​​the invention.

0058The flanks of the thread can be divided into load-bearing flanks and non-load-bearing flanks. The load-bearing flanks are responsible for the transmission of force from the threaded plug to the threaded bushing. A load-bearing flank is immediately adjacent to a non-load-bearing flank, ie a load-bearing and an adjacent, non-load-bearing flank are connected to one another by means of exactly one thread root or one thread crest arranged between them.

0059In a preferred embodiment, the flank is a supporting flank. It can be made possible to distinguish between a supporting flank and a non-supporting flank, whereby a design that supports the core idea of ​​the invention can be further improved. In particular, a different design can be selected for the supporting flank than for the non-supporting flank.

0060In an independent aspect of the invention, a threaded plug can be provided on an elongated body for a threaded connection with a threaded bushing. The threaded plug has a conical external thread and can be designed as above, but it can also be considered particularly preferably an initially independent design, wherein a non-load-bearing flank of the thread has a section of a function which is curved outwards over an area around the middle between the thread root and the thread tip. It was recognized that a non-load-bearing flank can meet other requirements and thus a non-symmetrical design of the thread can be provided, in which in particular the non-load-bearing flank of the thread of the threaded plug can have an outwardly curved region.

0061With regard to the prevailing opinion, an outwardly curved area represents a departure from the usual shape, since an inwardly curved shape was previously intended.

0062In a preferred embodiment, the function of the portion of the function for the non-bearing flank has a logarithm.

0063General statements on the design of the supporting flank, in particular with regard to the representation of a section of the flank using a function, also apply to the non-supporting flank. This applies in particular to the difference between a function and a description of a circle or section of a circle and/or an ellipse or section of an ellipse.

0064For the purposes of the description, a function having a logarithm is understood to be a function that has a logarithmic course or a section of a logarithmic spiral.

0065In a preferred embodiment, the section of the function for the non-load-bearing flank extends over a height of at least 0.35 times, in particular at least 0.4 times, in particular at least 0.45 times, in particular at least 0.5 times, in particular at least 0.55 times, in particular at least 0.6 times, in particular at least 0.65 times, in particular at least 0.7 times, the thread height, whereby the construction, the manufacturability and/or use can be improved. The advantageous property can extend over a wide range of thread heights.

0066In a preferred embodiment, a length range of the section of the function for the non-load-bearing flank extends over a length between the thread root and the thread crest which is 0.2 times the length between the thread root and the thread crest of the flank whose section can be represented by the section of the function of the non-load-bearing flank. This allows not only a height of the described area to be taken into account, but also a length, which can be varied accordingly, in particular increased. In a particularly preferred embodiment, the length range of the section of the function of the non-load-bearing flank can extend over a length between the thread root and the thread crest which is 0.25 times, in particular 0.3 times, in particular 0.35 times, in particular 0.4 times, in particular 0.45 times, the length between the thread root and the thread crest of the non-load-bearing flank.

0067In a preferred embodiment, the section of the function of the non-load-bearing flank extends in a region around the middle in the thread height, which is at least 0.25 times the thread height. In a particularly preferred embodiment, the aforementioned region can be at least 0.3 times, in particular 0.35 times, in particular 0.4 times, in particular 0.45 times, in particular 0.5 times, the thread height.

0068When considering the section of the function for the non-load-bearing flank, the same procedure is used as for the particularly load-bearing flank discussed above. The center is determined and it is seen how far the section of the function extends from the center to both the thread root and the thread crest in relation to the thread height. The smaller extent of the extension from the center to the thread crest or the center to the thread root is multiplied by two.

0069In a particularly preferred embodiment, a "function that has a logarithm" is understood to mean a function in which the argument, which can be part of a term, is logarithmized. A logarithm with any base is possible, as is a decimal or natural logarithm.

0070It can be provided that the function having a logarithm has a basic form that is given by<maths id="math0002"><math display="block"><mi mathvariant="normal">e</mi><mn>2</mn><mfenced><mi mathvariant="normal">x</mi></mfenced><mo>=</mo><mi>multiplier</mi><mn>1</mn><mo>*</mo><mi>ln</mi><mfenced><mo>+</mo><mo>/</mo><mo>−</mo><mi>multiplier</mi><mn>2</mn><mo>*</mo><mi mathvariant="normal">x</mi><mo>+</mo><mi>shift</mi><mn>1</mn></mfenced><mo>+</mo><mi>shift</mi><mn>2</mn></math><img file="EP4403742A2_D0002.tif" /></maths> can be given,<ul id="ul0002" list-style="none" compact="compact"><li>where Multiplier1 is a real number,</li><li>Multiplier2 is a real number,</li><li>Shift1 is a real number, and</li><li>Shift2 is a real number.</li></ul>

0071In a preferred embodiment, the section of the function of the non-load-bearing flank begins at a distance from the thread root and the distance between the thread root and the beginning of the section of the function is bridged by means of an arc-shaped, in particular a circular arc-shaped, section, which is most preferably a circular arc. This allows a simple design with a relatively simple function to be used, which allows variability in order to enable adaptation or compromise to different requirements.

0072In a particularly preferred embodiment, the non-load-bearing flank of the thread base has a circular arc-shaped section, in particular a circular arc segment, which is followed by the section of the function. In a particularly preferred embodiment, the section of the function for the non-load-bearing flank is followed by a circular arc-shaped section, in particular a circular arc segment, which extends to the thread tip. In a particularly preferred embodiment, the non-load-bearing flank can be represented or described by means of the section of the function, a circular arc-shaped section, in particular a circular arc segment, which extends from the section of the function to the thread root, and a circular arc-shaped section, in particular a circular arc segment, which extends from the section of the function to the thread tip.

0073In a particularly preferred embodiment, a thread between two adjacent thread roots or two adjacent thread crests can have a supporting flank as described in the description and a non-supporting flank as described in the description. This can result in a synergistic effect.

0074It is possible that the design of the thread with the described non-load-bearing flank and the described load-bearing flank results in a synergistic effect that improves sliding. Alternatively or additionally, it can be achieved that machine-related misalignment errors can be compensated. Alternatively or additionally, better centering can be made possible when screwing in.

0075In a preferred embodiment, the elongated body is a rod section of a drill string for an earth drilling device or a drive element for a rod section of a drill string of an earth drilling device. As a result, the described embodiments of threaded plug and/or threaded bushing can be used in an area that must meet high requirements. In particular, increased stability and durability can be achieved in the area mentioned with the high loads.

0076The term "rod section" within the meaning of the description includes individual, in particular rigid, rod sections that can be connected to one another directly or indirectly and that can be connected to one another in the longitudinal axial direction to form a drill rod or a drill string. The rod sections can be connected to one another by screwing them together with the mechanical interposition of an intermediate element or without the interposition of an intermediate element using a threaded bushing with a threaded plug as described. A rod section does not necessarily have to have an element for screwing at both longitudinal ends, so that it is possible for the rod section to have i) a threaded bushing at one longitudinal end and a threaded plug at the other longitudinal end, ii) a threaded bushing at each of the longitudinal ends, iii) a threaded bushing at one longitudinal end and a different type of coupling element at the other longitudinal end.

0077The term "drill string" in the sense of the description includes several interconnected rod sections. A bore can be drilled using a drill string, which can have a drill head at its front end and, if present, a drill head tip that can be designed as a drilling tool (for example, as an expander head).

0078The term "earth drilling device" in the sense of the description includes a (and thus any) device which can move in particular a drill string comprising rod sections in an existing channel or a channel to be created, in particular in the ground, in order to create or widen a bore, in particular a horizontal bore (HD), or to pull pipelines or other long bodies into the ground. The earth drilling device can in particular be an HD device. An earth drilling device can be a device that drives a drill string, which can in particular work by displacing soil. The drill string can be introduced into the soil in a translatory and/or rotary manner in the longitudinal axial direction of the drill string. The drill string can be moved in the soil by applying tension or pressure and, if necessary, also in a rotary or rotating manner.

0079The term "drive element" in the sense of the description includes an element arranged on the earth drilling device, which is designed to be connected to a drill string or a rod section of the drill string in order to exert a translational and/or rotational force on the drill string. Typically, a rod section to be connected to the drill string is brought into engagement with the drive element in order to then connect the rod section connected to the drive element to the already drilled drill string.

0080The invention also provides a threaded bushing on an elongated body for a threaded connection with a threaded plug, wherein the threaded bushing has a conical internal thread, in which a section of a flank of the internal thread can be represented as a section of a function which has a curvature, wherein the section of the function forms an angle to a connecting line of adjacent thread roots or thread ends over a height of at least 0.2 times the thread height. has a thread crest that is greater than 45°. A threaded bushing that is complementary to the threaded plug can be created.

0081As for the threaded plug, preferred embodiments for the threaded bushing are possible with regard to the design of the shape, in particular a complementary design or a design of the thread corresponding to the threaded plug with similar advantages.

0082The invention also provides, in an aspect relating independently to a patent-founding invention, a threaded bushing which is designed for a threaded connection with a threaded plug. The threaded bushing can have the properties described above, but can also be designed independently of the threaded bushing mentioned above. A non-load-bearing flank of the internal thread has a portion of a function that is curved inward over an area about the middle between the thread root and the thread crest.

0083Also for the threaded bushing, which relates to an aspect that independently justifies patentability, preferred embodiments for the threaded bushing are possible with regard to the design of the shape, in particular a complementary design or a design of the thread corresponding to the threaded plug with similar advantages.

0084The invention also provides a threaded connection which has a threaded plug as described in the description and a threaded bushing as described in the description. By designing both the threaded plug and the threaded bushing with a shape adapted to the other design, the core idea of ​​the invention can be supported or further improved.

0085The invention also provides a use of a threaded plug or a threaded bushing described in the description for a threaded connection with a threaded bushing or a threaded plug. The threaded plug has an external thread or the threaded bushing has an internal thread, in which a section of a flank of the external thread or of the internal thread can be represented as a section of a function which has a curvature, wherein the section of the function has an angle to a connecting line of adjacent thread roots or thread crests which is greater than 45° over a height of at least 0.2 times the thread height.

0086The threaded bushing can be braced against a shoulder on the threaded plug. The threaded plug and threaded bushing can be brought into contact with each other with their end faces, so that a force screw connection is made between an end face of the shoulder and the supporting flanks, particularly those in the area near the shoulder. The shoulder or the end face on the threaded plug can alternatively or additionally serve as a maximum stop for the screw connection. Axial forces and/or torsional moments can also be transmitted by means of the shoulder or the end face(s).

0087In a preferred embodiment, the end face angle of the end faces of the threaded plug and the threaded bushing, which can come into contact with each other, is in the range of 65° to 90°, in particular in the range of 65° to 80°.

0088If the invention is described by means of different embodiments and/or aspects (for example relating to a device or application-related design), the descriptions of the individual designs or aspects complement each other. In particular, the statements regarding the threaded plug can also apply to the threaded bushing and vice versa. Furthermore, the statements regarding threaded plugs and/or threaded bushings can also apply to the aspect of "use". The statements regarding the geometry of the thread, the elongated body connected to it, a rod section and the like also apply to the aspect of a threaded connection in which a described threaded plug is present in addition to the described threaded bushing.

0089It has been shown that a threaded plug, which is designed as described in the description, can also interact with a threaded bushing to a certain extent, if the threaded bushing is not designed to be complementary or corresponding to the threaded plug. The same applies to the interaction of a threaded bushing, which is designed as described in the description, with a threaded plug. However, it has also been recognized that a mutually corresponding or complementary design of threaded plug and threaded bushing may be preferred.

0090In a preferred embodiment, the thread pitch of the threaded bushing and/or the threaded plug is between 5 mm and 9 mm, preferably 7 mm.

0091In a preferred embodiment, the cutting angle is between 20° and 30°.

0092In a preferred embodiment, the cutting dimension of the threaded plug is at least 0.5 mm.

0093In a preferred embodiment, the cutting dimension of the threaded bushing is at least 1 mm.

0094In a preferred embodiment, the difference between the length of the threaded plug and the threaded bushing is at most 0.5 mm.

0095The invention is explained in more detail below with reference to an embodiment shown in the drawings.

0096In the drawings shows:<dl id="dl0001" compact="compact"><dt><u>Fig.1</u></dt><dd>a partial section through a threaded connector;</dd><dt><u>Fig.2</u></dt><dd>an enlarged section of the<figref idref="f0001">Figure 1</figref>, in which additional geometric data are shown;</dd><dt><u>Fig.3</u></dt><dd>one to the threaded plug of the<figref idref="f0001">Figure 1</figref> in one embodiment, corresponding threaded bushing; and</dd><dt><u>Fig.4</u></dt><dd>an enlarged section of the<figref idref="f0003">Figure 3</figref>, with the specification of further geometric data.</dd></dl>

0097<figref idref="f0001">Figure 1</figref> shows in the right of the two representations a section of an elongated body 1 with a threaded plug 2 with an external thread 3 in a sectional view. The threaded plug 2 is located at the end of the elongated body 1, which is designed as a rod section of a drill string for an earth drilling device or a drive element for a rod section of a drill string of an earth drilling device.

0098The right of the two representations of the<figref idref="f0001">Figure 1</figref> is a sectional view of the left representation of the<figref idref="f0001">Figure 1</figref> along AA. The left of the two representations of the<figref idref="f0001">Figure 1</figref> shows a view of the threaded plug 2 of the elongated body 1 in the longitudinal direction of the elongated body 1.

0099The elongated body 1 has a longitudinal axis L. The external thread 3 of the threaded plug 2 is a conical external thread. The external thread 3 of the threaded plug 2 is shown in an enlarged view in the<figref idref="f0002">Figure 2</figref> shown.

0100<figref idref="f0002">Figure 2</figref> shows the external thread 3 with the sizes applicable to the example. In the thread 3 of the threaded plug 2, thread roots GG and thread crests GS are drawn. The thread roots GG are located on a connecting line V_GG adjacent thread roots GG. The thread crests GS are located on a connecting line V_GS adjacent thread crests GS. The connecting line V_GG is parallel to the connecting line Vos in the illustrated embodiment. The thread height is designated GH and indicates the length or distance between the thread root GG and the thread crest GS.

0101A thread has a supporting flank and a non-supporting flank. The supporting flank extends from the thread root GG to the adjacent thread crest GS and is shown in the<figref idref="f0002">Figure 2</figref> to the right of the thread root GG. The non-load-bearing flank extends to the left from the thread root GG to the adjacent thread crest GS.

0102In the embodiment shown, the supporting flank has a section that can be represented by a function ft. The function ft has a curvature. The section of the function f_t has a height H_t of at least 0.3 times the thread height GH an angle to the connecting line V_GG or V_GS adjacent thread roots GG or thread crests GS that is greater than 45°.

0103Furthermore, a length range L_t of the section of the function f_t, in which the function ft forms an angle to the connecting line V_GG or V_GS adjacent thread roots GG or thread crests GS that is greater than 45°. The length range or the length L_t extends over at least 0.1 times the length between the thread root GG and the thread crest GS of the supporting flank.

0104The section of the function f_t extends in an area around the center GM in the thread height GH, which has at least 0.3 times the thread height GH, wherein the area is designed such that the angle of the section of the function ft in the area to a connecting line of adjacent thread roots GG or thread crests GS changes by less than 30°.

0105In the illustrated embodiment, the flank extends from the thread root GG over a length L_GG in the direction of a thread crest GS, in which the angle to a connecting line of adjacent thread roots GG or thread crests GS is less than 20°, and the length L_GG greater than 0.1 times the length GL_t between the thread root GG and the thread crest GS of the load-bearing flank, the section of which is represented by the section of the function ft.

0106The function f_t extends from the thread base GG to the right edge of the thread marked L_t The function f_t another form F closes_t which in the illustrated embodiment is a circular arc-shaped segment.

0107In the embodiment shown, the supporting flank is thus composed of the section of the function ft and a circular arc-shaped segment Ft between function f_t and threaded tip GS together.

0108In the embodiment shown, the non-load-bearing flank is made up of three shapes. The first shape is a circular arc-shaped segment that extends from the thread root GG to the left to the right edge of the area L_nt The circular arc segment is followed by an area which is defined by a function f_nt The height over which the function f_nt is marked H_nt The section is designed as a function with an outward curvature. The function f_nt A circular arc-shaped segment follows up to the thread tip GS.

0109A thread of the embodiment shown in the figures for the threaded plug 2 comprises not only the supporting flank and the non-supporting flank but also at least partially the plateau at the level of the connecting line Vos. For example, the thread of the<figref idref="f0002">Figure 2</figref>, which is marked with the designations for the sizes, comprise a plateau following one of the two thread crests GS up to the next adjacent thread crest GS.

0110<figref idref="f0003">Figure 3</figref> shows in the right of the two representations a section of an elongated body 1 with a threaded bushing 4 with an internal thread 5. The threaded bushing 4 is located at the end of the elongated body 1, which is designed as a rod section of a drill string for an earth drilling device or a drive element for a rod section of a drill string of an earth drilling device.

0111The right of the two representations of the<figref idref="f0003">Figure 3</figref> is a sectional view of the left representation of the<figref idref="f0001">Figure 1</figref> along AA. The left of the two representations of the<figref idref="f0003">Figure 3</figref> shows a view of the threaded bushing 4 of the elongated body 1 in the longitudinal direction of the elongated body 1.

0112The elongated body 1 has a longitudinal axis L. The internal thread 5 of the threaded bushing 4 is a conical internal thread. The internal thread 5 of the threaded bushing 4 is shown in an enlarged view in the<figref idref="f0004">Figure 4</figref> shown.

0113<figref idref="f0004">Figure 4</figref> shows enlarged the internal thread 5, which is complementary to the external thread 3 of the threaded plug 2. The<figref idref="f0004">Figure 4</figref> The sizes given correspond essentially to the sizes of the<figref idref="f0002">Figure 2</figref>.