EP1129292A1

EP1129292A1 - Worm for an eccentric screw pump or a subsurface drilling motor

Info

Publication number: EP1129292A1
Application number: EP99972291A
Authority: EP
Inventors: Bruno Kächele
Original assignee: Wilhelm Kachele Elastomertechnik GmbH
Current assignee: Wilhelm Kachele Elastomertechnik GmbH
Priority date: 1998-11-13
Filing date: 1999-09-21
Publication date: 2001-09-05
Anticipated expiration: 2019-09-21
Also published as: DE19852380A1; US6544015B1; DE59912836D1; CA2350578C; NO332950B1; NO20012250L; WO2000029750A1; CA2350578A1; DE19852380C2; EP1129292B1; NO20012250D0; ATE310906T1

Abstract

A rotor (4) for an eccentric screw pump or a subsurface drilling motor consists of a straight, essentially cylindrical core element (21), onto which a shell (22) is forged by a cold-forging process. The forging gives the shell (22) the helical external form required for eccentric screw pumps (1). The rotor (4) described can be produced by non-cutting shaping, which is of considerable advantage in particular in the case of large rotor dimensions, since no waste material is produced.

Description

Screw for an eccentric screw pump or a sub-drill motor

Eccentric screw pumps are used to pump viscous, fluid media, especially media that are highly abrasive. The eccentric screw pumps consist of a stator with a continuous opening. The inner wall of the through opening has the shape of a multi-start screw and is formed by an elastomer. The elastomer is located in a tubular jacket made of high-strength material, for example steel, the inner contour of the jacket either being cylindrically smooth or the thread contour following the through-hole at a constant radial distance. A rotor rotates in the through hole of the stator, the number of threads of which is one less than the number of threads in the through hole. The rotor is made of a solid material and has a particularly high abrasion resistance.

In the case of an eccentric screw pump, the rotor

-1- driven from the outside by a motor and it works in cooperation with the stator through the through hole. During the rotation of the rotor, in cooperation with the inner wall of the through hole, in the broadest sense, crescent-shaped or banana-shaped chambers are formed, which gradually move through the stator as the rotor rotates.

Such arrangements can also be used as a motor if the liquid is pressed through the arrangement at high pressure. The pressure of the liquid sets the rotor in revolutions and mechanical energy can be taken from the rotor. This arrangement is used, for example, in underground drilling motors.

The stators are comparatively simple to produce. They are vulcanized via a mold core and in this way receive the complicated shape of the through opening. In contrast, the manufacture of the rotors, which has hitherto usually been produced from the full material in a machining process, has been more difficult.

It is known from DE-A-1 703 828 to forge the rotor from a tube. Rotors of this type are not sufficiently dimensionally stable in the axial direction at high driving forces or high pressures, such as occur in underground drilling motors. Among other things, the drive torque causes the rotor to twist due to its helical shape and thereby shorten it. The result is that the computed pitch of the rotor no longer corresponds to the computed thread pitch of the multi-start thread in the stator and leaks occur, which too Loss of pressure and thus loss of performance.

Another type of construction of a rotor is known from DE-A-195 01 514. The rotor is composed of a jacket and a core element contained in the jacket. The jacket is produced by cold forming from a cylindrical tube. Here, a drawing tool is pulled through the cylindrical tube, which gives the tube the helical shape required for the rotor. The core element, which is connected to the tube at both ends, is subsequently loosely inserted into the jacket produced in this way.

However, it has been shown that the dimensional accuracy on the outside of the jacket is insufficient and the jacket has to be treated. In addition, the known rotor twists relatively strongly because of its lack of torsional strength. The torsion leads to a change in the pitch of the thread to the stator, which in turn negatively affects the seal to the stator.

DE-D-18 16 462 describes a rotor whose jacket consists of a ceramic mass. A steel shaft also penetrates the hollow shell, the space between the inside of the shell and the steel shaft being filled with a binder.

Proceeding from this, it is an object of the invention to provide a rotor for an eccentric screw pump or an eccentric screw motor, for example an underground motor, which is comparatively inexpensive to produce and is torsionally stable. This object is achieved by the rotor with the features of claim 1.

The new rotor uses a core element that is encased in a jacket. The outside of the jacket forms the thread-like structure, i.e. the helical surface. In this way, the jacket can be manufactured by cold forming in a relatively inexpensive non-cutting manufacturing process. Inside the jacket is a core element that runs the entire length of the jacket and gives the jacket the necessary axial stability.

In this way, rotors can also be made from materials that are ductile but difficult to machine like stainless steel, e.g. V2A or V4A steels. The core element, however, can consist of a non-stainless steel.

Due to the helical shape of the jacket, this could theoretically change in length under the influence of the torque in the manner known from the prior art when it is twisted. By using the core element, the jacket is prevented from this axial shortening.

The core element can be a simple, externally cylindrical body which is very simple and inexpensive to manufacture.

Because the jacket of the rotor according to the invention is forged onto the core element, a very firm connection is established between the core element and the jacket. de. This fixed connection improves the torsional strength and also contributes to the fact that the length of the rotor practically does not change appreciably even under load.

Forming the jacket onto the core element also has the advantage that the surface of the rotor no longer has to be reworked. The shaping gives it its final and smooth surface, which on top of that is bare when the shaping is done by cold working.

Cold forming has the further favorable side effect that the pitch of the rotor does not change, as would be the case if a warm forging process were used. In the case of hot forging, the change in length which occurs during cooling would have to be taken into account previously.

The overall structure can thus be manufactured without cutting.

The jacket applied to the core member has substantially the same wall thickness over its entire length and circumference, i.e. it is about the same thickness at every point.

The core element is only partially in contact with the jacket. These sections are areas of the thread valleys of the jacket. In the area between the thread valleys, i.e. the thread tips of the jacket, there are gaps between the core element and the jacket. These spaces have the shape of a single or multi-start screw. When the jacket is cold-formed, the deformation can only go so far that the thread valleys of the jacket just touch the core element. The connection between the core element and the jacket is then practically only frictional.

However, it is possible to allow the cold deformation to go so far that the core element is also deformed or the wall thickness of the jacket changes slightly at the point of contact with the core element. The connection to the core element is then to a certain extent also form-fitting in this area, and it can also become material-fit as a result of cold welding.

A particularly torsion-resistant connection between the core element and the jacket is achieved if the core element contains at least in one section of its longitudinal extension at least one groove which has a different course than the threaded valley. With a corresponding relative position of this groove to the threaded valley, it can be achieved that the jacket is forged into this groove of the core element during the manufacturing process. Since the direction of this groove deviates from the course of the threaded valley, it can be prevented with certainty that the casing can unscrew from the core element along the screw formed by the threaded valley.

A particularly effective locking is achieved if the core element carries at least one groove that runs over its entire axial length. The production of the core element becomes very simple if this groove follows the surface line. The groove expediently has a width, as seen in the direction of the start, which corresponds approximately to the contact area of the inside of the jacket in the area of the threaded valley with the core element. The depth of the groove is between 0.1 to 1.5 mm. It has been found to be useful to have approximately 0.5 mm.

It is favorable if the core element has several grooves.

The rotor according to the invention can have wall thicknesses between 2 and 20 mm with a diameter measured between 30 and 300 mm. The length of the new rotor can be up to 8 m.

In order to connect the coupling head to the rotor, the core element has at one end a pin which projects beyond the jacket. This pin is expediently designed as a threaded pin.

The rotor according to the invention can be used in eccentric screw pumps or arrangements which are used as motors, for example underground drilling motors.

In addition, further developments of the invention are the subject of dependent claims.

In the drawing, an embodiment of the object of the invention is shown. Show it:

1 an eccentric screw pump in a perspective view, partially cut away, 2 shows the rotor of the eccentric screw pump according to FIG. 1, in a longitudinal section,

3 shows the rotor according to FIG. 2, cut along the line III-III,

4 shows an underground drilling motor in a longitudinal section,

Fig. 5 shows another embodiment of the rotor of the eccentric screw pump according to Fig. 1, in a longitudinal section, and

6 shows the rotor according to FIG. 5 in a cross section similar to FIG. 3.

1 shows a perspective view, partially cut away, of an eccentric screw pump 1. The eccentric screw pump 1 includes a pump head 2, a stator 3, a rotor 4 running in the stator 3 and a mouthpiece 5.

The stator 3 consists of a tubular cylindrical stator jacket 6, for example made of steel, which is provided with connection threads 7, 8 at both ends. The stator jacket 6 forms a cylindrically smooth inner surface 9 on which a stator lining 11 is vulcanized from an elastomeric material. The lining 11 delimits a continuous opening 12 with a helical inner wall 13. The through opening 12 extends through the entire stator 3 and is coaxial with its outer contour, in particular with its connecting threads 7 and 8.

The helical inner wall 13 forms a multi-start thread, the number of threads being greater than the number of threads of the rotor 4 and a correspondingly large number of helically wound strips which project radially inwards.

Instead of using a stator jacket 6, which has a cylindrically smooth inner wall 13, a stator jacket 6 can also be used, which itself shows a helically wound inner contour. In this case, the elastomeric lining 11 has a constant wall thickness, as seen over the length of the stator 3. With the latter type of stators, higher pressures can be generated. However, since the design of the stator 3 is not the subject of the invention in the present case, a cursor see explanation.

The pump head 2 has a housing 14 with a sealed through bore 15 for a drive shaft 16 running therein. The drive shaft 16 is to be set in rotation by means of a drive motor (not shown) and coupled to the rotor 4.

At its front end, the housing 14 is provided with an internal thread 17 into which the stator 3 with the connecting thread 8 is screwed. The bearing bore 15 is aligned coaxially with the through opening 12 of the stator 3.

Between the stator 3 and the beginning of the bearing bore 15 there is an inlet chamber 18 into which a connection 19 coming from the outside opens.

Finally, the mouthpiece 5, which consists of a substantially tubular part with an internal thread 20, is screwed onto the outlet-side end of the stator 3.

Instead of the external threads 7 and 8 shown, the mouthpiece 5 and the pump housing 14 can also be connected to the stator 3 via corresponding internal threads on the stator 3, or the parts are connected to one another via tie rods and the stator 3 clamped between them.

The structure of the stator 3 is explained below with reference to FIGS. 2 and 3:

As can be seen in FIG. 2, the stator 3 exposes itself a core element 21, a stator jacket 22 and a coupling head 23 together.

In the exemplary embodiment shown, the core element 21 is a thick-walled steel tube with an at least originally cylindrical outer peripheral surface 24 and a continuous cylindrical inner space 25.

The core element 21 is straight and therefore tubular, because the interior does not make any noteworthy contribution to the strength that is at stake here, but merely increases the weight. However, it can also be massive.

At its right end in FIG. 2, the core element 21 is provided with a threaded pin 26 onto which the coupling head 23 is screwed. At the opposite end, the core element 21 contains a threaded bore 27.

The jacket 22 of the rotor 4 is also a tube with an inner wall 28 and an outer surface 29. The jacket 22 is cold forged, as is e.g. is described in DE-A-17 03 828, helically formed. The outer wall 29 forms a thread that continues over the entire axial length of the jacket 22. It begins at 31 and ends at 32. The number of threads of the thread formed by the outer surface 29 is one less than the number of threads of the through opening 12 in the stator 3.

As can be seen from the cross section in FIG. 3, the rotor 4 in the exemplary embodiment shown has a four-start thread, ie a total of four strips extend helically along the casing 22. Since the through Opening 12 is accordingly five continuous, the five-start thread five helically extending strips of Elastomerma ^¬ forms TERIAL in the through hole 12th

The jacket 22 is, as already mentioned, tubular, which is why the inner surface 28 follows the outer surface 29 at a constant distance.

As a result of the screw-like shaping of the casing 22, its outer surface 29 alternately forms a thread apex 33 and a thread valley 34 when viewed in the longitudinal direction seen each cutting plane in the circumferential direction.

The dimensions of the cylindrical straight tube from which the jacket 22 is cold-formed are selected such that after the final deformation to the screw-like shape, the jacket 22 with its inner peripheral surface 28 in the area of the thread valleys 34 (based on the outer contour) the outer peripheral surface 24 of the core element 21 at least touched.

With a correspondingly greater deformation, it is also possible to additionally slightly deform the outer peripheral surface 24 of the core element 21, as a result of which the outer peripheral surface 24 has flat grooves 35 which follow the contour of the threaded valleys 34. If the deformation is continued in this way, not only a frictional but also a positive connection is created between the jacket 22 and the core element 21 in the region of the neren of the jacket 22 bulging threaded valleys 34 with the core element 21. In addition, due to the deformation, cold welding can even take place between the jacket 22 and the core element 21 at the contact points.

Since, as mentioned, the semifinished product from which the jacket 22 is made is a cylindrical tube, the diameter of which is larger than the outer diameter of the core element 21, there are helical gaps 36 between the core element 21 and the jacket 22. The number of these helical gaps 36 is equal to the number of thread crests 33 which can be seen in the cross-section of the rotor 4 in the circumferential direction. Depending on the application, these spaces 36 can either remain empty or be filled with a mass. This mass can e.g. Synthetic resin or synthetic resin filled with light metal powder, cast metal or sintered metal.

The drive head 23 is a machined cylindrical turned part with two threaded blind bores 37 and 38. With the threaded blind bore 37, the drive head 23 is screwed onto the threaded pin 26 and serves to connect the rotor 4 to the drive shaft 16. Instead of the blind bore 38, other driving means also come into play Question. In a departure from the connection shown, the drive head 23 can also be screwed into a threaded bore in the core element 21.

In order to prevent the drive head 23 from becoming detached from the rotor 4, the thread direction of the threaded pin 26 is opposite to the thread direction on the jacket

22 trained screw. In addition, the drive head

23 be welded to the jacket 22 in a liquid-tight manner, which also increases the torsional strength between the drive head 23 and the jacket 22. If the jacket 22 carries, for example, a multi-start right-hand screw, the thread of the threaded pin 26 is a left-hand thread. The same applies analogously to the thread in the threaded blind bore 37.

In order to finally fix the jacket 22 relative to the core element 22 on the outlet or pressure side, a disk-shaped spacer element 41 is provided, which is fixed by means of a screw 42 which is screwed into the internal thread 27. The spacer element 41 fixes the core element 21 in the radial direction with respect to the jacket 22 with the aid of a correspondingly contoured shoulder 43 and a correspondingly shaped short extension. Instead of the screw connections shown, the spacer element 41 can be ver ^¬ both with the core element 21 and with the jacket be welded.

The rotor 4 shown is produced by coaxially and simultaneously passing the tubular core element 21 and the tube which forms the jacket 22 through the cold-forming device according to DE-A-17 03 828. As a result, the helically wound jacket 22 is cold forged from the cylindrical outer tube. The core element 21, however, remains essentially completely undeformed, apart from the flat grooves 35. After the cold forging process, the component obtained is shortened to the desired length and the threaded pin 26 is machined by swirl milling or turning and subsequent thread cutting or rolling.

The stator 4 produced by cold working has a straight line, as is customary in eccentric screw pumps Axis.

Cold forging achieves a structure that is favorable in terms of the forces that occur.

With the structure described and in the manner described, rotors can be produced in which the wall thickness of the casing 22 is between 2 and 20 mm. The overall diameter of the rotor 4 measured can be up to 300 mm, while the entire length of the rotor 4 can reach up to 8 m. The large lengths are required for high delivery pressures for pumps or high torques for motors, such as occur when delivering in the subsea or underground area.

In the rotor 4, the core element 21 can be made of a different material than the jacket 22. In addition, at least the jacket 22 can be formed from a material that is difficult to machine but ductile, e.g. V4A steel.

The rotor 4 described can, however, not only be used in the eccentric screw pump 1 shown in FIG. 1, but is also suitable in the same way for motors which are constructed like eccentric screw pumps, for example underground drilling motors. With the help of such an arrangement, hydraulic energy is converted into mechanical energy in that a drive fluid is pressed through the “eccentric screw pump” at high pressure. As a result, the rotor 4 is rotated and drive power can be drawn from the shaft 16. Since the basic structure of the rotor 4 is independent of whether it is in connection with an underground drilling motor or an eccentric screw pump is used, it is not necessary in addition to the eccentric screw pump according to FIG. 1 to produce a basically identical section through an underground drilling motor.

FIG. 4 shows the use of the rotor 4 according to the invention in an underground drilling or mud motor 51. The basic construction of the underground drilling motor 51 is basically similar to the construction of an eccentric screw pump, as shown in FIG. 1.

While mechanical energy is converted into hydraulic energy in the eccentric screw pump, the reverse energy conversion takes place in the underground drilling motor 51. The underground drilling motor 51 is subjected to liquid under high pressure, whereby its rotor 4 is rotated.

Insofar as there are structural elements in the underground drilling motor 51 which have already been explained in connection with FIGS. 1 to 3, no detailed description is given again.

The underground drilling motor 51 has a stator 3, which in turn consists of a cylindrical steel tube 6 as a jacket with an elastomeric lining 9. At the inlet end of the stator 3, the stator jacket 6 is provided with a conical internal thread 52, into which a hydraulic connection coupling piece 54 with a continuous channel is screwed with a conical external thread 53.

The connector piece 54 is tubular and serves to feed the drive fluid into the underground drilling motor 51. The outlet-side end of the stator 3 is also provided with a conical internal thread 55, into which an outlet mouthpiece 56 is screwed. For this purpose, the outlet mouthpiece 56 has a corresponding conical external thread 57 and also contains a continuous channel 58.

The outlet nozzle 56 also serves as a bearing for an output shaft 59, which is connected to a drill bit, not shown. The outer diameter of the output shaft 59 is smaller than the clear width of the channel 58 in the outlet mouthpiece 56. In this way, the liquid passing through the underground drilling motor 51 can escape in the direction of the drill bit and at the same time be used as a rinsing liquid.

The coupling head 23 connects the rotor 4 to the output shaft 58.

The basic structure of the rotor 4 does not differ from the structure of the rotor 4 according to FIGS. 2 and 3, which is why a new explanation is unnecessary at this point.

The underground drilling motor 51 according to FIG. 4 works in such a way that pressurized liquid, for example flushing liquid, such as is used in the underground area, is supplied via the hydraulic connection coupling piece 54. The pressurized fluid penetrates into the pump chambers which are formed between the rotor 4 and the inner lining 9 of the stator 3. The pressure of the liquid tends to enlarge the chamber, whereby the rotor 4 is rotated in the stator 3. Since as many chambers as possible formed between the stator 3 and the rotor 4 should be open on the inlet side of the underground drilling motor 51, a rotor 4, which is used for motor purposes, has significantly more threads than a rotor 4, which is used for pump purposes . Since the number of threads in the stator 3 is in each case one more than the number of threads of the rotor 4, the number of threads in the stator 3 is also significantly larger in the case of an underground drilling motor 51 than in the eccentric screw pump 1 according to FIG. 1.

The axial length of an undivided underground drilling motor 51 can be up to 8 m. If longer lengths are required, several of the underground drilling motors 51 shown in FIG. 5 are connected in series, in which case the rotor 4 of the subsequent motor stage is provided with the threaded pin 26 at both ends in order to on the one hand provide the coupling with the upstream rotor 4 and a downstream one to produce another rotor 4 or the tool.

Figures 5 and 6 show a rotor 4 similar to the rotor of FIG. 2 in each case in a longitudinal and in a cross section.

The structure is almost identical, which is why the same reference numerals are used for parts and construction features already described, without a new explanation.

The essential difference from the rotor according to FIG. 2 is that the core element 21 in its cylindrical outer peripheral surface 24 in the embodiment shown. example contains a total of four straight grooves 61 continuous in the longitudinal direction. As can be seen from the cross section according to FIG. 6, the grooves 61 have a rectangular cross section with a depth of approximately 0.5 mm. The width of the groove 61 measured in the circumferential direction is approximately 5 mm.

The production takes place as explained in connection with FIG. 2. Due to the cold forging process or drawing process, the material of the casing 22 flows into the grooves 61 in the region of the threaded valleys 34 during the cold forming, specifically at the points at which the inside of the casing 22 that bulges inward in the region of the threaded valleys 34 cuts. Since the jacket 22 forms a four-start screw on its outside, a total of four threads run over the length of the rotor 4. The threads form corresponding inward-facing convex surfaces, the course of which intersects the grooves 61 at the pitch angle of the respective thread. In the exemplary embodiment shown, a thread cuts one of the grooves 61 every 90 °. The number of grooves 61 can also be greater than the number of threads of the rotor 3.

Since the material of the jacket 22 flows into the groove 61 during cold forming, a positive connection is established between the jacket 22 and the core element 21.

Because the course of the grooves 61 does not follow the course of the threaded valleys but has a different angle, the core element 22 cannot be unscrewed from the jacket 22 even when force is used. The embodiment shown with straight grooves 61 is particularly simple with regard to the manufacture of the core element 21. However, it is also possible to provide the grooves 61 as helically extending grooves, the grooves advantageously forming a screw which runs counter to the screw of the threads, ie if the jacket 21 forms a right-hand screw on its outside, the grooves 61 on the core element 22 form a left-hand screw. In order to further increase the strength of the connection between the jacket 22 and the core element 21, the slope can be chosen such that the grooves 61 lie at right angles to the threaded valleys 34.

Due to the positive connection between the jacket 22 and the core element 21, there is a very high torsional strength. The rectangular cross section of the grooves 61 prevents the material of the casing 22 which has been pushed into the grooves 61 from coming out of the grooves 61 or pressing out the threaded valleys 34 when 22 shear forces become effective between the core element 21 and the casing.

A rotor (4) for an eccentric screw pump (1) or an underground drilling motor (51) consists of a straight, essentially cylindrical core element (21) onto which a jacket (22) is forged in the cold forging process. The jacket (22) is given the helical outer shape required for eccentric screw pumps (1) by forging. The rotor (4) described can be produced without cutting, which is of considerable advantage in particular in the case of large rotor dimensions, since there is no material waste.

Claims

Claims:

1. Rotor (4) for an eccentric screw pump (1) or eccentric screw motor (51), or a stator

(3) have a continuous interior (12), project radially in the strips and in which the rotor (4) is arranged,

with a substantially cylindrical core element (21),

with an outer casing (22) forming a helically deformed outer surface (29), which essentially surrounds the core element (21) over its entire length and whose outer surface has thread valleys (34) and thread apex (33), the casing (22) also is connected to the core element (21) in that a cylindrical tube forming the jacket (22) is deformed into a helical tube until the jacket lies with its inner circumferential surface in the region of the threaded valleys on the core element, and

with a coupling head (23) which is rotatably connected to the rotor (4).

2. Rotor according to claim 1, characterized in that the rotor (4) forms a single or multiple thread.

3. Rotor according to claim 1, characterized in that the casing (22) consists of a different material than the core element (21).

4. Rotor according to claim 1, characterized in that the jacket (22) is tubular over its entire length.

5. Rotor according to claim 1, characterized in that the casing (22) has essentially the same wall thickness over its entire length and its entire circumference.

6. Rotor according to claim 1, characterized in that the casing (22) with the core element (21) is only in sections in contact.

7. Rotor according to claim 1, characterized in that the casing (22) with the core element (21) in the region of the at least one threaded valley (34) is frictionally connected.

8. Rotor according to claim 1, characterized in that the casing (22) with the core element (21) is positively connected only in the region of the at least one threaded valley (34).

9. Rotor according to claim 8, characterized in that the positive connection of at least one groove

(61) is formed, which follows the course of the at least one threaded valley of the casing (22) and into which the inside of the casing (22) projects in the region of the at least one threaded valley.

10. A rotor according to claim 9, characterized in that the groove (61) is formed when the tube (22) forming the tube is formed.

11. A rotor according to claim 9, characterized in that the core element (21) in at least a portion of its longitudinal extent contains at least one groove (61), the course of which deviates from the course of the at least one threaded valley.

12. Rotor according to claim 9, characterized in that the groove (61) has a rectangular cross section.

13. Rotor according to claim 9, characterized in that the groove (61) continues over the entire length of the core element (21).

14. A rotor according to claim 9, characterized in that the groove (81) is a straight groove which runs along the surface line of the core element (21).

15. Rotor according to claim 9, characterized in that the groove (61) is a helical groove

16. Rotor according to claim 1, characterized in that the jacket (22) is connected to the core element (21) by the cylindrical tube forming the jacket (22) being deformed by cold working.

17. A rotor according to claim 1, characterized in that between the core element (21) and the casing (22) at least one helically extending space (36) is included.

18. Rotor according to claim 17, characterized in that the at least one helically extending intermediate schenrau (36) is filled with a mass.

19. Rotor according to claim 17, characterized in that the at least one helically extending space (36) is empty.

20. Rotor according to claim 1, characterized in that the core element (21) is tubular.

21. A rotor according to claim 1, characterized in that the core element (21) is solid.

22. A rotor according to claim 1, characterized in that the core element (21) forms a pin (26) projecting from the jacket (22) on at least one end.

23. Rotor according to claim 22, characterized in that the pin (26) with the coupling head (23) is rotatably connected.

24. Rotor according to claim 22, characterized in that the pin (26) is a threaded pin and that the coupling head (23) contains a threaded bore (38).

25. A rotor according to claim 22, characterized in that the thread of the threaded pin (26) has a different pitch than the rotor (4).

26. A rotor according to claim 1, characterized in that the core element (21) is connected at one end to the casing (22) via a radially acting centering piece (41).

27. Eccentric screw pump, characterized in that it contains a rotor (4) according to one or more of the preceding claims.

28. Eccentric screw motor (51), characterized in that it contains a rotor (4) according to one or more of the preceding claims.

29. underground drilling motor (51) having a stator (3) with a continuous interior (12) projecting radially in the strips, characterized in that it contains a rotor (4) according to one or more of the preceding claims.