Patent Publication Number: US-2022228554-A1

Title: Wind turbine rotor blade, mounting sleeve and method for connecting two rotor blade segments

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation application of international patent application PCT/EP2019/076708, filed Oct. 2, 2019, designating the United States, the entire content of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The disclosure relates to a wind turbine rotor blade which is formed by two rotor blade segments. The disclosure also relates to a mounting sleeve for a wind turbine rotor blade, and to a method for connecting two rotor blade segments. 
     BACKGROUND 
     A multiplicity of wind turbines having wind turbine rotor blades (also for short below: rotor blades) are known from the prior art and are used for converting wind power into electrical energy. Wind turbines have a multiplicity of components which are connected to one another, for example by means of a flange connection. For example, in the region of a rotor blade root, the rotor blades have a rotor blade connection with a multiplicity of mounting sleeves which are integrated in the laminate and via which the rotor blades are connected by means of fastening screws or fastening screw bolts to a bearing ring of what is referred to as a pitch bearing or to a component connected to the bearing ring, for example what is referred to as an extender of the wind turbine. The mounting sleeves can be part of a flange insert for the rotor blade connection. Such a construction is known, for example, from US 2017/0045032. 
     Alternatively, use is also made of (flange) connections for the connection of rotor blade segments that, arranged and assembled according to length, form a rotor blade. Such a rotor blade is referred to as a divided or segmented rotor blade. For example, mounting sleeves are then located in the laminate of a connection end or dividing flange of the rotor blade segments. The rotor blade segments can be connected to one another directly or via suitable intermediate pieces by means of screw bolts. 
     Divided rotor blades are preferred in particular for transport reasons and are gaining increasing importance especially because of the increasing overall length of rotor blades. 
     SUMMARY 
     It is an object of the disclosure to specify a concept for divided rotor blades that ensures a particularly advantageous connection of rotor blade segments. 
     According to an aspect, a wind turbine rotor blade which is formed by two rotor blade segments is disclosed. In other words, it involves a segmented or divided rotor blade. The first rotor blade segment has, at a first connection end (also connecting or coupling end), a plurality of first mounting sleeves which each have a first internal thread. The second rotor blade segment has, at a second connection end assigned to the first connection end, a plurality of second mounting sleeves. A second internal thread is arranged within each of the second mounting sleeves. Each second internal thread is displaceable axially with respect to a longitudinal axis of the corresponding second mounting sleeve. A connecting bolt is screwed into each pair of mutually aligned first and second mounting sleeves, into the two corresponding internal threads, such that the two rotor blade segments are mechanically connected to one another at the connection ends. 
     The described wind turbine rotor blade is formed by two releasable connected rotor blade segments. For this purpose, a number of connecting bolts (also screw bolts) which correspond to the respective first and second mounting sleeves and which screw together the two connection ends is provided. By means of the provision of a movable internal thread in the mounting sleeves of the one rotor blade segment, one side of the connection of the two rotor blade segments becomes what is referred to as a “movable bearing”. One side of the bolt screw connection is therefore mounted in an axially displaceable manner. As a result, when the required screw-in length is correspondingly taken into consideration, each connecting bolt can be fitted to the corresponding other rotor blade segment without stress and without a tool. This arrangement or connection permits a simple, in particular installation-friendly, joining of the two blade segments. In particular, simple threading in of all of the bolts during the installation of the two rotor blade segments is made possible. In particular, the installation is conceived in such a manner that first of all the connecting bolts are screwed into one connection end, and then the corresponding mounting sleeves of the other rotor blade segment are pushed onto the connecting bolts. The axial displaceability of the second internal thread considerably simplifies the threading in for such large components as wind turbine rotor blades. All of the connecting bolts can therefore be fitted without constraining forces. A retrospective screwing together (tightening) or maintaining of the connections is also made possible in a particularly simple manner. Furthermore, an installation of the inner side or outer side of the blade is possible. In addition, a particularly easy connecting system is made possible, as a result of which the blade loads as a whole can be kept small. 
     In the case of the wind turbine rotor blade described, a particularly torque-resistant connection of the two blade segments is made possible. The absorption and transmission of particularly high tensile and compressive forces of the root-side segment or to the tip-side segment is made possible. Furthermore, the described connecting arrangement permits transmission of forces from one blade segment into the second blade segment exclusively via the connecting bolt. Such a force flux is also referred to as “in-line”. In other words, the blade segments are releasably joined without force deflections as in the case of eccentric screw connections or intermediate pieces subjected to a tensile or bending load. Such a force flux permits a very good use of material and contributes to a low tendency to gapping of the connection and to a small bending loading of the screw connections, in particular in contrast to flange connections. Furthermore, a uniform distance between the mounting sleeves, and therefore between connection ends, is ensured over the entire connecting circumference. 
     The wind turbine rotor blade is divided into at least two rotor blade segments which are arranged in the longitudinal direction. Two or more dividing points are also conceivable, wherein the further segments can be mechanically coupled analogously to the described connecting system. 
     The first and second mounting sleeves are, for example, elements which are laminated into the connection ends of the blade segments. It is also conceivable for the two mounting sleeves to be formed by dividing an overall sleeve. In this case, the rotor blade is first of all manufactured as a whole, that is, with an integral casing or shell, and is subsequently separated, for example cut or sawn, at a dividing point. The separation takes place in the region of the overall sleeves, and therefore two sleeve halves arise per overall sleeve, one each for the two blade segments produced by division. These sleeve halves correspond to the first and second mounting sleeves mentioned. The mounting sleeves typically have a passage bore or passage opening, wherein the cross section, contours, wall thickness or the like partially changes or varies over the longitudinal axis of the sleeves. That is, the sleeves have different sections over the length. 
     According to an embodiment, each first internal thread is in a fixed position with respect to the corresponding first mounting sleeve. In other words, the first internal thread is not displaceable or movable and is therefore configured as a fixed bearing. For example, the first internal thread is formed integrally as part of the mounting sleeve. This contributes to the aforementioned advantages and functions, wherein in particular the screwing in of the bolts during the installation in combination with the movable bearing of the other blade segment is simplified. 
     According to an embodiment, each first internal thread is displaceable axially with respect to a longitudinal axis of the corresponding first mounting sleeve. As an alternative to the above embodiment, the first internal thread can likewise be displaceable axially and therefore permit more clearance and axial play during the installation of the two rotor blade segments. 
     According to an embodiment, an axial displaceability of each second internal thread is limited. Analogously, the displaceability of each first internal thread is limited, should the first internal threads likewise be configured to be movable. The limiting takes place, for example, by means of two opposite axial stops. This contributes to a simple and secure installation of the bolts in the internal threads and thus to a connection of the two rotor blade segments. 
     According to an embodiment, each second mounting sleeve has an axially displaceable thread insert having the second internal thread. A movable threaded insert is therefore involved. The movable threaded insert is placed in the sleeve, for example, before the sleeves are laminated in the corresponding rotor blade segment. The threaded insert permits the configuration as a movable bearing. The threaded insert is arranged in the interior of the sleeve, that is, in the passage bore or in a corresponding recess. 
     According to an embodiment, an outer shaping of each threaded insert is matched to an inner shaping of the corresponding second mounting sleeve in such a manner that each threaded insert is guided in the corresponding second mounting sleeve in a manner secure against rotation by means of a form fit. The threaded inserts and therefore the second internal threads therefore cannot be rotated with respect to the longitudinal axes of the second mounting sleeves. It is thus reliably made possible, for example, for the bolts to be able to be correspondingly screwed into the threaded insert. 
     According to an embodiment, the outer shaping of each threaded insert includes a polygon shape, in particular with rounded edges. Such a configuration contributes to the threaded insert being able to be produced simply and a low stress concentration being produced at the corresponding component, namely the mounting sleeve. 
     According to an embodiment, each connecting bolt has a tool engagement point, in particular a hexagon. The tool engagement point is a means or a device on the connecting bolt that permits engagement of a tool, for example a wrench or a pair of pliers, in order to rotate the screw connection. 
     According to an embodiment, a plurality of pressure pieces is arranged between the two connection ends of the two rotor blade segments, wherein each pressure piece is configured as a sleeve and applied to a corresponding connecting bolt. In other words, pressure pieces are mounted or pushed onto the connecting bolts between the two connections ends. In the connected state of the two rotor blade segments, the pressure pieces are clamped between the connection ends by means of the screw connection of the connecting bolts. The connection ends are therefore in touching contact with the pressure pieces. The pressure pieces are mounted on the bolts coaxially about the connecting bolts. 
     The pressure pieces arranged next to one another in the state mounted in accordance with the operation are, for example, individual pieces, that is, are mounted independently of one another. Two or more such pressure pieces arranged next to one another are alternatively connected to one another. For example, two or more such pressure pieces form a stiff unit, the pressure pieces being mounted as one part on the corresponding bolts. Alternatively, for example, all of the pressure pieces of one side, that is, suction side or pressure side, are connected. Also, all of the pressure pieces can be connected to one another such that only one unit has to be mounted. 
     The pressure pieces are configured in such a manner that only compressive forces act on them or are transmitted by them. The pressure pieces do not absorb any tensile forces or bending torques by force deflection. The prestressing force in the bolt is sufficiently large for the pressure piece to always be subjected to a pressure loading. For example, during bending of the rotor blades because of the wind loads which are in action, no movement of the pressure pieces relative to the connection ends takes place, for example sliding (that is, along a direction perpendicular to the longitudinal axes of the sleeves), since the pressure pieces are fixedly connected to the connection ends. 
     The pressure pieces can also be in form-fitting engagement with the connection ends of the segment. 
     This has the result that the tensile forces are transmitted substantially exclusively via the bolts. This is advantageous since very long tension rods can be selected as bolts, the tension rods being favorable for forces, torques and stresses. Transmission of the tensile forces is therefore not interrupted or is deflected via other elements, such as screwheads or intermediate pieces. Furthermore, a high thread distance between the first and second internal threads is made possible, which in turn has a favorable effect on the tensile forces being transmitted. The pressure pieces themselves therefore have to withstand or transmit lower loads, which has an advantageous effect on the service life of the pressure pieces. 
     According to an embodiment, each pressure piece has at least one opening, and therefore the tool engagement point is accessible via the opening. The opening may also be referred to as clearance or aperture and creates access for actuating a corresponding bolt. 
     According to an embodiment, walls of each pressure piece that delimit the opening are provided with one or more bevels. This facilitates the accessibility by the clearance being enlarged. 
     According to an embodiment, the first internal threads include either a right-handed thread or left-handed thread and the second internal threads the respective other. As a result, by rotation of the bolt, the latter can be screwed simultaneously into the internal threads of the mounting sleeves of both connection ends. 
     According to a further aspect, a mounting sleeve for a wind turbine rotor blade according to the first aspect is disclosed. An internal thread is arranged within the mounting sleeve, wherein the second internal thread is displaceable axially with respect to a longitudinal axis of the second mounting sleeve. 
     The mounting sleeve permits the aforementioned advantages and functions. What has been stated above applies analogously. 
     According to a further aspect, a pressure piece for a wind turbine rotor blade in the above-described aspect is disclosed. The pressure piece is configured as a sleeve through which a connecting bolt can be passed. 
     According to a further aspect, a method for connecting two rotor blade segments of a wind turbine rotor blade is disclosed. The first rotor blade segment has, at a first connection end, a plurality of first mounting sleeves which each have a first internal thread. The second rotor blade segment has, at a second connection end assigned to the first connection end, a plurality of second mounting sleeves which each have a second internal thread, wherein each second internal thread is displaceable axially with respect to a longitudinal axis of the corresponding second mounting sleeve. The method has the steps of:
         partially screwing each connecting bolt into a respective second internal thread of the second connection end in such a manner that each connecting bolt projects by a predetermined length from the second connection end,   bringing the first connection end of the first rotor blade segment to the second connection end of the second rotor blade segment,   partially screwing the respective connecting bolts into a respective first internal thread of the first connection end,   pushing together the two rotor blade segments, and   tightly screwing each connecting bolt in such a manner that a predetermined distance between a reference point defined on the connecting bolt and one of the two connection ends is achieved.       

     The method substantially permits the aforementioned advantages and functions. 
     To maintain the predetermined length during the step of partially screwing into the second internal thread, the length of the protruding bolt is compared with a desired value. When tightly screwing a bolt, the installation progress can be monitored continuously by, for example, looking at the reference point which migrates between the connection ends during the screw connection. 
     Owing to the axial displaceability of the second internal thread, each connecting bolt which is at least partially screwed in is displaced individually during the installation. 
     According to an embodiment, after the step of partially screwing the connecting bolts into the second internal thread, a respective pressure piece is applied to one connecting bolt each. In the tightly screwing step, the predetermined distance is achieved on the basis of a tool engagement point of the pressure pieces as reference point. 
     Further advantages, features and developments emerge from the exemplary embodiment below which is explained in conjunction with the figures. Identical, similar or identically acting elements are provided with the same reference signs in the figures. For clarity reasons, not all of the described elements in all of the figures may be identified by associated reference signs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described with reference to the drawings wherein: 
         FIG. 1  shows a schematic illustration of a wind turbine; 
         FIG. 2  shows a schematic illustration of a divided rotor blade with two rotor blade segments; 
         FIG. 3  shows a schematic basic sectional illustration of a bolt connection of two rotor blade segments of a rotor blade according to the prior art; 
         FIG. 4  shows a schematic cross-sectional view of the rotor blade with bolt connections according to an embodiment of the disclosure; 
         FIG. 5  shows a perspective view of an individual bolt connection between two rotor blade segments according to an embodiment of the disclosure; 
         FIG. 6  shows a schematic cross-sectional view of the bolt connection according to  FIG. 5 ; 
         FIGS. 7 to 9  show detailed views of the bolt connection according to  FIGS. 5 and 6 ; 
         FIG. 10  shows a schematic sequence diagram of a method for producing the divided rotor blade according to an embodiment of the disclosure; 
         FIGS. 11A and 11B  show a starting state during the installation of the divided rotor blade; and, 
         FIGS. 12A to 12G and 13  show various installation states during the connection of two rotor blade segments with bolt connections according to  FIGS. 4 to 9 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a schematic illustration of a wind turbine  100 . The wind turbine  100  has a tower  102 . The tower  102  is secured on an underlying surface by means of a foundation  104 . A nacelle  106  is mounted rotatably at an end of the tower  102  opposite the underlying surface. The nacelle  106  has, for example, a generator which is coupled to a rotor  108  via a rotor shaft (not shown). The rotor  108  has one or more rotor blades  110  (wind turbines) which are arranged on a rotor hub  112 . 
     During operation, the rotor  108  is set into rotation by an airflow, for example wind. This rotational movement is transmitted to the generator via the rotor shaft and optionally a transmission. The generator converts the kinetic energy of the rotor  108  into electrical energy. 
       FIG. 2  shows a wind turbine rotor blade  110 . The rotor blade  110  is in the form of a conventional rotor blade and has a rotor blade root region  114  which faces the rotor hub  112 . The rotor blade root region  114  has typically a substantially circular cross section. The rotor blade root region  114  is adjoined by a transition region  116  and a profile region  118  of the rotor blade  110 . The rotor blade  110  has, with respect to a direction of longitudinal extent  120 , a pressure side  122  and an opposite suction side  124 . The rotor blade  110  is configured to be substantially hollow in the interior. 
     In the rotor blade root region  114 , a rotor blade connection end  126  is provided with a flange connection  128  by means of which the rotor blade  110  is mechanically connected to a pitch bearing or to an extender. 
     The rotor blade  110  has a dividing point  130  at which a blade-root-side rotor blade segment  132  and a blade-tip-side rotor blade segment  134  are connected to each other. For this purpose, the two segments  132 ,  134  have a respective rotor blade segment connection  136 ,  138  (also connection ends). The rotor blade  110  is therefore a divided rotor blade, as described at the beginning. Each connection end  136 ,  138  has a multiplicity of mounting sleeves which are arranged following the profile and have internal threads for receiving screw bolts, also called bearing bolts or connecting bolts. A connection end is realized, for example, as a flange insert which is inserted as an insert into a production mold for producing the rotor blade  110 . However, it is also conceivable for no flange insert to be provided and for the mounting sleeves to be embedded and laminated directly into the rotor blade half shells. The mounting sleeves are, for example, steel sleeves. The connection of the two rotor blade segments  132 ,  134  is described in more detail below, wherein details are explained by way of example with reference to an individual bolt connection. 
       FIG. 3  shows a schematic sectional view through two connected rotor blade segments  132 ,  134  corresponding to the prior art, wherein an individual bolt connection is illustrated. The first connection end  136  of the first rotor blade segment  132  has a multiplicity of first mounting sleeves  140 , as described at the beginning. The second connection end  138  of the second rotor blade segment  134  has a multiplicity of second mounting sleeves  142 . A connecting bolt  146  is screwed into in each case one pair of mutually aligned first and second mounting sleeves  140 ,  142 , the connecting bolt  146  mechanically fixedly connecting the two connection ends  136 ,  138  and therefore the two rotor blade segments  132 ,  134 . 
     In addition, one pressure piece  144  per bolt connection  148  is clamped between the two connection ends  136 ,  138 . 
       FIG. 4  shows a rotor blade  110  having a first rotor blade segment  132  and a second rotor blade segment  134  according to an embodiment of the disclosure in a perspective view in the region of the dividing point  130 . On the suction side  124  and on the pressure side  122 , a multiplicity of bolt connections  148  can be seen, in which pressure pieces  144  are in each case used. A bolt connection  148  is in each case illustrated in sectioned form, wherein it can be seen that a connecting bolt  146  is configured as a continuous bolt which connects the two connection ends  136 ,  138 . 
       FIGS. 5 to 9  show an individual bolt connection  148  of the rotor blade  110  in detail. 
       FIG. 5  illustrates a first and a second mounting sleeve  140  and  142  into which a connecting bolt  146  is screwed, wherein a pressure piece  144  is arranged between the mounting sleeves  140  and  142 . The pressure piece  144  is configured as a type of sleeve and is arranged on the connecting bolt  146 . Each connecting bolt  146  has a tool engagement point  150  (here a hexagon in a suitable, typical wrench width) which is accessible via an opening  152  in the pressure piece  144 . 
       FIG. 6  shows the bolt connection  148  in a perspective schematic sectional view. The mounting sleeves  140  and  142  each have a continuous opening  154  into which the connecting bolt  146  is at least partially inserted. For the screw connection to the connecting bolts  146 , the first mounting sleeves  140  have a first internal thread  156  and the second mounting sleeves  142  have a second internal thread  158 . The first internal threads  156  are configured as right-handed threads and the second internal threads  158  as left-handed threads. The connecting bolt  146  has corresponding external threads  164 ,  166  at its opposite ends  160 ,  162 . The first internal threads  156  are fixed in position and, in the example, are formed integrally with the first mounting sleeves  140 . The second internal threads  158  are axially displaceable, as will also be described. The mounting sleeve  142  having the second internal thread  158  is arranged in the first rotor blade segment  132 . The latter can be arranged at the rotor-blade-tip end or rotor-blade-root end. 
       FIG. 7  shows the pressure piece  144  in detail. The pressure piece has a plurality of bevels  168  on the walls  170  delimiting the opening  152 . This optimizes the opening  152  in terms of space and therefore the access for a tool for fitting onto the tool engagement point  150 . 
       FIG. 8  shows details of the second internal thread  158 . The second internal thread  158  is part of a threaded insert  172  which is arranged in a corresponding section  174  of the continuous opening  154  in the second mounting sleeve  142 . The threaded insert  172  is displaceable in the portion  174  axially with respect to a longitudinal axis  176  of the second mounting sleeve  142  (see double arrow). The axial displaceability is limited on both sides along the longitudinal axis  176 , for example by means of an outer stop element  178  facing the second connection end  138  and an inner stop element (not illustrated in  FIG. 8 ) facing away from the second connection end  138 . 
       FIG. 9  shows the shaping of the threaded insert  172 , wherein the outer shaping corresponds to a polygon shape P3G with rounded edges. The section  174 , which may also be referred to as recess, is matched in respect to its inner shaping to the outer shaping of the threaded insert  172 , wherein a form fit is formed such that the threaded insert  172  is guided so as to be displaceable in the second mounting sleeve  142  in a manner secure against rotation. 
     The described bolt connection  148 , a multiplicity of which are provided in the divided rotor blade  110 , permits the advantages and functions mentioned at the beginning. 
     A method for connecting the two rotor blade segments  132  and  134  of the divided rotor blade  110  according to an embodiment of the disclosure is described below with reference to  FIGS. 10 to 13 .  FIG. 10  shows a schematic sequence diagram of the method, while  FIGS. 11 to 13  show various installation states. 
     Initially, a rotor blade segment (here the second rotor blade segment  134 ) is in a starting situation (see  FIG. 11A ). In this situation, the threaded insert  172  of the second mounting sleeves  142  is located in any position between an inner stop element  177  and an outer stop element  178  (see  FIG. 11B ). 
     In a first step S 1  (see  FIGS. 12A and 12B ), the connecting bolts  146  are partially screwed into the second internal thread  158  of the second rotor blade segment  134 , wherein the threaded insert  172  is pressed against the second, inner stop  177 . The connecting bolt  146  can have a marking up to which it is screwed in. Each connecting bolt  146  projects here by a predetermined length  180  out of the second connection end  138 . Alternatively, in order to check a predetermined length  180 , the connecting bolt  146  can be pulled out of the second connection end  138  until the threaded insert  172  lies against the outer stop element  178 . The predetermined length  180  is compared with a predefined desired value in order to ensure correct installation. This is crucial so that a sufficient thread overlap of the two internal threads  156 ,  158  is later achieved. The assignment of the correct bolt end  160 ,  162  or of the correct external thread  164 ,  166  follows from the different threads (right-handed thread or left-handed thread) per rotor blade segment  132 ,  134 . 
     In a next step S 2  (see  FIG. 12C ), the pressure pieces  144  are pushed onto the connecting bolts  146 , wherein the connecting bolts  146  are displaced inward. This can be seen by the fact that the threaded inserts  172  are moved toward the inner stop element  177 . 
     In a next step S 3  (see  FIG. 12D ), the first rotor blade segment  132  or the first connection end  136  is brought up to the second connection end  138  until it nearly touches the connecting bolts  146 . The threaded inserts  172  are pushed here into the second mounting sleeves  142  of the second rotor blade segment  134  as far as the inner stop  177 . Subsequently, the connecting bolts  146  are pulled one after another out of the second mounting sleeves  142  and are in each case threaded into a first mounting sleeve  140  aligned with the corresponding second mounting sleeve  142 . 
     In a next step S 4  (see  FIGS. 12E and 12F ), the first rotor blade segment  132  is moved in the direction of the second rotor blade segment  134  until the connecting bolts  146  are screwed to a predetermined extent into the first internal threads  156  of the first mounting sleeves  140 . 
     In a next step S 5  (not illustrated), the two rotor blade segments  132 ,  134  are pushed together to a stop, wherein the connection ends  136 ,  138  lie against the pressure pieces  144  and the threaded insert  172  lies again against the inner stop  177 . Owing to the axial displaceability of the second internal threads  158  by means of the threaded inserts  172  (“movable bearings”), the required axial (and also radial) plays for threading in and mounting are present. In particular, the inside diameter of the sleeve is greater than the outside diameter of the threaded insert. 
     In a next step S 6  (see  FIG. 12G ), the connecting bolts  146  are tightly screwed. The two connection ends  136 ,  138  are tightened here with respect to each other, with the threaded inserts  172  also striking against the outer stop elements  178 . The screw connection takes place by means of a suitable tool which is fitted onto the respective tool engagement points  150 . During the screwing tight, each tool engagement point  150  is used as a reference point  182  in order to check the progress of the installation. The reference point “migrates” within the respective pressure piece  144  depending on the installation state, and this can be monitored via the opening  152 . 
       FIGS. 12G and 13  show the final installation state. A predetermined distance  184  between the first connection end  136  and each reference point  182  should prevail here. 
     It should be mentioned at this juncture that the above statements also apply equally to a divided rotor blade having two or more dividing points  130 . In this case, the divided rotor blade would have three or more rotor blade segments. 
     It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims. 
     LIST OF REFERENCE SIGNS 
     
         
           100  wind turbine 
           102  tower 
           104  foundation 
           106  nacelle 
           108  rotor 
           110  rotor blade 
           112  rotor hub 
           114  rotor-blade-root region 
           116  transition region 
           118  profile region 
           120  direction of longitudinal extent 
           122  pressure side 
           124  suction side 
           126  rotor blade connection end 
           128  flange connection 
           130  dividing point 
           132  first rotor blade segment 
           134  second rotor blade segment 
           136  first connection end 
           138  second connection end 
           140  first mounting sleeve 
           142  second mounting sleeve 
           144  pressure piece 
           146  connecting bolt 
           148  bolt connection 
           150  tool engagement point 
           152  opening 
           154  continuous opening 
           156  first internal thread 
           158  second internal thread 
           160  first end 
           162  second end 
           164  first external thread 
           166  second external thread 
           168  bevel 
           170  wall 
           172  threaded insert 
           174  section of the second mounting sleeve 
           176  longitudinal axis 
           177  inner stop element 
           178  outer stop element 
           180  predetermined length 
           182  reference point 
           184  predetermined distance 
         S 1  to S 6  steps