MXPA06002063A - Eccentric screw pump equipped with a rotor that is erosion-resistant - Google Patents

Abstract

The invention relates to an eccentric screw pump or an eccentric screw motor comprising a rotor (4) that is configured from a tubular jacket (19) with at least two layers. The outer layer (45) of the rotor jacket consists of a material that is abrasion- and/or corrosion-resistant.

Description

SCREW PUMP WITHOUT EXCENTRIC ENDORSEMENT WITH ROTOR RESISTANT TO EROSION DESCRIPTIVE MEMORY According to DE 198 52 380 A1, a rotor is known for an eccentric screw pump or for an eccentric screw motor, which is produced by cold forming. The pump or the motor respectively has a stator with a continuous opening in the shape of a screw, in which the rotor rolls during positive displacement operation. The stator forms a cylindrical tube, which is provided with an elastomeric coating. The elastomeric coating itself represents the wall of the continuous opening and acts as a seal with respect to the stator. The stator is composed of a core element and an envelope formed around it. The envelope is cold formed, from a cylindrical tube, to the configuration in the shape of thyme. Therefore, the originally cylindrical tube not only obtains the configuration in the form of a screw, as is necessary for the rotor, but in this way the tube is also fixedly fixed to the core element. In the final state, the valleys of the thread of the stator envelope are fixedly applied and in dynamic union on the core element. In order to improve the drag effect between the core element and the stator envelope, the supporting element can also be provided with longitudinal ribs. The known rotor can be manufactured economically in very large quantities. They can be reached without further lengths of up to 6 meters, without requiring a subsequent treatment by chip removal of the stator surface. The surface of the rotor is very smooth and sufficiently uniform in its dimensions. The core element located in the enclosure prevents the rotor from losing its spiral shape under pressure load, which would lead to an error of passage between stator and rotor, and as a consequence to corresponding imperfections. The steel material used hitherto for the known rotor is not sufficiently strong for a series of applications in view of the abrasion that occurs and for some cases of application is not sufficiently resistant to corrosion. In other words, the known rotor is not characterized by a sufficient resistance to erosion.

By erosion it is to be understood here not only corrosion wear, but also wear due to grinding of the material driven on the surface. According to the state of the art it is also known to provide the stator with an enclosure, which also shows a configuration in the form of a screw, similar to a configuration in the form of a screw of the continuous opening. The elastomeric coating, which also serves as the sealing material, in these cases has practically an almost constant wall thickness. With a stator of this type, higher pressures or higher torques can be generated in the case of an eccentric screw motor. From here, it is a problem of the invention to obtain an eccentric worm pump or an eccentric worm motor, in which the rotor is characterized by a better resistance to erosion. This problem is solved according to the invention with the eccentric screw motor or the eccentric screw pump with the features of claim 1. It is also a problem of the invention to obtain a method for producing a rotor, which shows a greater resistance to erosion. The method is characterized by the features of claim 23. In the eccentric screw pump according to the invention or in the eccentric screw motor according to the invention respectively, the rotor is constituted in the form of a sandwich. It consists of a radially inner layer and a radially outer layer, the radially inner layer being especially adapted to the highest resistance to erosion. It may be more resistant to abrasion or more resistant to corrosion, or both, than the radially inner layer.

Since, incidentally, the more corrosion-resistant materials can be formed less well and / or are much more expensive than the radially inner layer under certain circumstances with large wall thicknesses, the radially inner layer can be selected initially from the viewpoint of resistance and costs, so the result is obtained with a very thin radially outer layer. A very homogeneous structure of the rotor can be obtained, if the inner tube is a seamless tube. Thus, inhomogeneities are avoided, which could otherwise occur when welding. Such inhomogeneities could be prolonged outward as configuration defects. However, it is also possible to use a wound tube as the inner tube. The tube is preferably laser welded in the butt joint in the form of a screw. The propeller should be of the opposite direction to the helix of the outer layer. The inner layer, or respectively the inner tube, consists of an easy to shape steel, which is well suited for deflecting the forces that arise and which can be cold formed in a usable manner. The outer layer may consist of a plugged tube. Nevertheless. A solution of this type is only suitable for rotors of short constructive length. For rotors with a large constructive length it is advantageous if the outer layer is formed by a rolled metal strip. The metal band is rolled up to the stop, so that the individual turns are abutting each other without slit. A particularly good arrangement is achieved if the butt joint extending in the form of a screw, in which the turns abut one another, is welded before the cold forming. The welding is preferably carried out with the aid of a laser. As an external material, it is possible to use, among other high quality steels, V2A steel, V4A or other abrasion resistant steels. Since these have a much higher specific weight than normal steel, the two-layer structure also means a weight saving, compared to a rotor only of high quality steel. This has a frankly remarkable importance in rotors with a length of up to 6 meters. The resistance of the rotor can be improved if it has a core element. The rotor can be formed around the core element, whereby a good connection with the core element is obtained. The core element prevents, in case of long lengths, a loss of the spiral shape of the rotor under load. Furthermore, with the aid of the core element, an additional torque can be transmitted over the rotor length. For this, the essentially symmetrical shaped core of revolution and not in the form of a screw is better suited. The core element itself can be tubular or solid. Furthermore, the intermediate space between the tube or the rotor casing and the core element can be left free or filled with a dough.

In the process according to the invention, a cylindrical tube is first provided. The tube is covered with a metallic layer, with which a double-walled structure is obtained. Next, the double-walled structure, which is cylindrical as above, is shaped into a screw. The lining of the cylindrical tube with the outer layer is very simple and can also be easily effected due to the simple geometrical configuration of the tube provided. Since the outer layer has to be applied only with a small wall thickness, because the strength of the rotor is provided in certain circumstances firstly by the inner tube for the outer layer, materials which could not be deformed can also be used cold in case of large wall thicknesses. In the method according to the invention, a seamless tube is advantageously used. The seamless tube conveniently has a polished metal surface., so that the union of the outer layer with the tube by cold forming is not impeded by oxidation residues. The outer metal layer consists in the simplest case of a metal strip, which is wound on the tube. To increase the tension, the metal band can be heated before its winding, immediately in front of the contact point. The subsequent cooling has as its object a concentration process, which holds the metal strip in a particularly fixed manner on the surface of the tube. The butt joint between adjacent turns is conveniently welded to prevent particle penetration. The double wall structure obtained is cold formed.

During the shaping process, the outer layer joins the lower pipe at least punctually, similar to what happens also in the formation of leaves. The connection is therefore particularly fixed and will not open even in case of temperature changes. In correspondence with the method according to the invention, a core element can be inserted before forming the coated tube. For the rest, developments of the invention are the subject of subordinate claims. From the study of the examples of modalities it is also clear that a series of modifications is possible. An example of embodiment of the object of the invention is shown in the drawings. In the same: Figure 1 shows an eccentric screw pump in a perspective representation, partially cut, Figure 2 shows a longitudinal section through the stator of the eccentric screw pump according to the invention, Figure 3 shows a longitudinal section through the rotor of the eccentric screw pump according to the invention, figure 4 shows a cross section through the rotor according to figure 3, and figure 5 shows the procedure of according to the invention for the manufacture of the rotor of the eccentric screw pump or the eccentric screw motor according to FIG. 1, with symbolic representation of the steps of the method. Figure 1 shows an eccentric screw pump 1 according to the invention, in a schematic representation in perspective.

A pump eccentric screw 1 belong pump head 2, a stator 3, which rotates a rotor 4 shown in Figure 2 fragmented and a connection head 5. The pump head 2 has a housing 6 essentially cylindrical, which at a front end is provided with a closing stage 7, through which a drive shaft 8 is sealed outwardly. In the housing 6, a connection socket 9 opens out radially, ending in A flange is clamped 11. Inside the housing 6 there is, as is usual in eccentric screwless pumps, a coupling part, for coupling with torsional resistance of the drive shaft 8, which is connected to an engine of drive not shown, with the rotor 4. The front end remote from the cover 7, of the housing 6, is provided with a clamping flange 12, whose diameter is greater than the diameter of the housing 6 essentially cylindrical. The clamping flange 12 contains a stepped bore 13, which is aligned with the interior space of the housing 6. In the stepped bore, a non-visible application shoulder is formed, against which the stator 3 is pressed with one end. The connection head 5 has a clamping flange 14 which cooperates with the clamping flange 12, which also contains a stepped hole, in which the other end of the stator 3 is inserted. A pipe 15 is aligned with the stepped hole. drive out. Between the two clamping flanges 12 and 14, the stator 3 is fastened tightly, with the aid of a total of 4 tie rods 16, to the housing of the four tie rods 16 in total, each of the two clamping flanges 12 and 14 is provided with four bores 17 aligned with each other, which is on a primitive circle that is greater than the outside diameter of the housing 6 or the tube 15 respectively. The rods 16 in the form of rods are guided through these bores 17. On the rods 16, nuts 18 are bolted to the opposite sides of the opposite clamping flange 12 or 14, 18, with the help of which the two clamping flanges 12 and 14 are fixed one on top of the other. The stator 3 consists, as shown in Figure 2, in a casing 19 of tubular formula with constant wall thickness, which surrounds an interior space 20. The envelope 19 consists of steel, an alloy of steel, light metal or a light metal alloy. It is shaped so that its lower wall 21 turns out to be the outer configuration of a multi-threaded screw. Its outer side 22 has a corresponding similar configuration, with a diameter corresponding to the wall thickness of the casing 19 is greater than the diameter of the interior space of the casing 19. The casing 19 ends at its front ends with front surfaces 23 and 24, which extend at a right angle with respect to its longitudinal axis 25. The longitudinal axis 25 is the axis of the interior space 20. In the simplest case, the interior space 20 has the configuration of a two-wire screw. Therefore, also the cross section that is surrounded by the outer surface 22, seen in each case perpendicularly the longitudinal axis 25, the configuration of an oval, similar to a race track. In order to adapt this respective geometry to the scaled bore 13, a sealing ring or reducer 26 sits on the housing 19 on each end face. Alternatively, the ends can also be formed in the form of cylindrical tubes. The sealing ring 26 contains a continuous opening 27, which coincides with the development of the outer surface 22 along the length of the sealing ring 26. In other words, the sealing ring 26 acts in the broadest sense as a nut, which is screwed on the thread defined by the casing 19. The length of the thread corresponds to the thickness of the obstruction ring 26. The obstruction ring 26 is limited radially outwards by a cylindrical surface 28, which is transformed in the direction axial on a flat surface 29, which is directed away from the shell 19.

The casing 19 is provided on an inner side 21, along all length, with a continuous coating 32. The coating 32 consists of an elastically flexible material, preferably elastomeric, for example natural rubber or synthetic material, and the present approximately same wall thickness at all points. As can be seen in FIG. 3, the rotor 4 is composed of a core element 33, a shell 34 of the rotor and a coupling head 35. The core element 33 is in the embodiment example shown a thick-walled steel tube with an outer peripheral surface 36 more at least originally cylindrical and a recent continuous cylindrical interior 37. The core element 33 is straight, and is therefore tubularly shaped, because the interior space does not provide any appreciable contribution to the strength, so what matters here, but only increases the weight. However, it can also be solid. The core element 33 is provided at its right end in FIG. 3, with a threaded core 38. The core element 33 has a threaded bore 39 at the opposite end. The envelope 34 of the rotor 4 is also a tube with an inner wall. 40 and an outer surface 41. The outer surface 41 forms a thread, which extends along the entire axial length of the casing 34.

It starts at 42 and ends at 43. The number of threads of the thread formed by the outer surface 41 is smaller by one than the number of threads of the continuous opening 20 in the stator 3. As can be seen the cross section in figure 4 the rotor 4 presents the example of embodiment shown a thread of four threads, namely, along the envelope 34 extends a total of four strips in the form of thyme. Since the continuous opening 20 is in correspondence of five threads, the thread of five threads in the continuous opening 20 forms a total of five strips extending in the form of a screw of elastomeric material. In figure 4 the cross section through the rotor 4 is shown. The envelope 34 of the rotor is two layers and consists of an inner layer 44 and an outer layer 45 placed on it. The inner layer 44 consists of an originally cylindrical steel tube with good deformation capacity and an appropriate resistance for the purpose of application. The outer layer 45 consists instead of an erosion resistant material, namely a material that is little eroded or worn by the medium to be pumped and / or that is not chemically attacked by the medium to be pumped. A suitable material is for example a high quality steel such as a V2A or a V4A. The wall thickness of the inner layer 44 is between 2 mm and 5 mm, while the wall thickness of the outer layer 45 can be between 1 mm and also 5 mm. The manufacture of this rotor 4 is explained below with the help of figure 5.

The envelope 34 is, as already indicated, tubular in shape, so that the inner surface 40 next to the outer surface 41 with constant spacing. Due to the screw-shaped conformation of the casing 34, its outer surface 41 alternately forms screw tops 46 and threaded valleys 47, viewed in the longitudinal direction. Due to the fact that there are several threads, the threaded valleys 47 and the threaded tops 46 appear not only in the longitudinal direction, but, as shown by the cross section according to FIG. 4, also in each cutting plane, seen in the peripheral direction . The dimensions of the straight cylindrical tube, from which the casing 34 is cold-deformed, is chosen so that, after the final deformation to obtain the screw-shaped configuration, the casing 34 touches with its inner peripheral surface 40, less in the area of the threaded valleys 47 (with reference to the outer contour), to the outer peripheral surface 36 of the core element 33. In the case of a correspondingly intense deformationIt is also possible to slightly deform the outer peripheral surface 36 of the core element 33, so that the outer peripheral surface 36 obtains flat grooves 48, which follow the outline of the threaded valleys 47. If the deformation is prolonged in this way, between the housing 34 and the core element 33 not only a dynamic connection but also a positive connection in the region of the threaded valleys 47 bulges towards the interior of the enclosure 34 occurs. with the core element 33. Furthermore, due to the deformation, even cold welding can take place between the shell 34 and the core element 33 at the contact points. As the blank from which, as noted, the casing 34 is manufactured, it is a cylindrical tube whose diameter is larger than the outer diameter of the core element 33, between the core element 33 and the casing 34. they generate intermediate spaces 49 that extend in the form of a screw. The number of these intermediate spaces 49 in the form of a screw is equal to the number of screw tops 46, which can be seen in the peripheral direction in the cross section of the motor 4. Depending on the application case, these intermediate spaces 49 may well remain empty. or be filled with a dough. This mass can be for example synthetic resin or synthetic resin loaded with light metal powder. The manufacturing process of the rotor 4 constituted by the layers 44 and 45 is shown in a very schematic manner in FIGS. 5 to 7. First of all, a seamless steel tube 51 is drawn, polished, with an appropriate wall thickness and an appropriate length of several meters. The steel tube 51 is wound on its outer side with a metal strip 52, which subsequently forms the outer layer 45. The metal strip 52 is a band of a suitable high-quality steel or of other type steel. As can be seen in figure 6, the band 42 is wound as a screw of a thread on the outer side of the steel tube 51. It therefore forms juxtaposed turns 53, which are separated from one another by means of butt joints 54 which They extend in the form of a screw. The winding of the metal strip 52 is carried out in such a way that the butt joint 54 remains as closed as possible. The butt joint 54 is welded during the winding or in a separate step with the aid of a laser beam 55 and filler material, to obtain a smooth and homogeneous cylindrical surface. Other welding procedures are also possible. Furthermore, they can be welded in a penetrating manner in order to join the band 52 in the area of the butt joint 54 with the support tube 51 by joining by material. Immediately prior to placing the metal strip 52 on the tube 51, it is heated, for example inductively or by means of a gas flame 56. In this way, the metal strip 52 generates, after its winding on the tube 51 and its cooling, a remarkable tension in the peripheral direction. Once the band 52 has been wound along the entire length of the tube 51 and the butt joint 54 has also been welded along its entire length, the core element 33 is plugged in according to the figure 7. The structure formed is then carried, by cold deformation, for example lamination by means of a plurality of cylinders, of which only one is shown in 57, to the desired screw shape. During the lamination, the metal strip 52 is bonded very closely to the outer surface of the steel tube 51 located below.

The metallic strip 52 forms on the steel metallic tube 51, once the process step according to FIG. 6 has been completed, a second outer tube, which sits firmly and in dynamic connection under tension in the peripheral direction on the peripheral surface. outside of the tube 51. The two tubes, namely the tube originated by winding and the inner seamless steel tube, are so firmly fixed to each other already after the winding, that they can no longer be separated from each other. The subsequent rolling process according to FIG. 7 results in an even more intimate connection, which assimilates at least to a certain degree to the plating of a metallic layer. By rolling, which leads to a stretching of a single piece of metal, surprisingly the outer tube, manufactured by winding, does not separate from the tube 51 located below. On the contrary, both are conformed together to the desired screw shape, while also obtaining the intimate connection with the core element 33. Instead of a single metal band, several metal bands can also be wound together as a multi-strand screw . In addition, the winding process can be repeated to generate several overlapping layers. The invention has been explained with the aid of an eccentric screw pump. The person skilled in the art will be able to appreciate, however, immediately, that the invention is not limited in any way to screw pumps, without eccentric end. On the contrary, according to the method of the invention in correspondence with FIGS. 5 to 7, rotors for eccentric screw motors or slurry motors can also be produced. As a result, a drive machine is obtained in each case, which contains a rotor with a high resistance capacity. An eccentric worm screw pump or an eccentric worm motor has a rotor, which is formed by a shell consisting of a material, which is resistant to abrasion and / or corrosion.

Claims (32)

NOVELTY OF THE INVENTION CLAIMS

1. An eccentric endless screw pump or an eccentric screw motor (1), characterized in that it comprises a stator (3) containing a continuous stator hole (20), which has a configuration in the form of a screw; a rotor (4) in the form of a screw adapted to the hole (20) of the stator, which has a tube (34) formed in the form of a screw, which is composed of an inner layer (44) and at least one outer layer (45) , which are formed together to obtain the configuration in the form of a screw, the outer layer (45) consisting of a material that is different from the material of the inner layer (44); and a coupling head (35), which is connected to the rotor (4) with resistance to torsion.

2. The eccentric screwless screw pump or the eccentric screwless motor in accordance with claim 1, further characterized in that the material of the outer layer (45) is more resistant to abrasion and / or more resistant to corrosion than the material of the inner layer (44).

3. The eccentric screwless screw pump or the eccentric screwless motor according to claim 1, further characterized in that the inner layer (44) consists of a seamless tube (51).

4. - The eccentric screwless screw pump or the eccentric screwless motor according to claim 1, further characterized in that the inner layer (44) consists of a steel.

5. The eccentric screwless screw pump or the eccentric screwless motor according to claim 1, further characterized in that the outer layer (45) consists of at least one metal strip (52).

6. The eccentric screwless screw pump or the eccentric screwless motor according to claim 5, further characterized in that at least one metal strip (52) of the outer layer (45) is wound in the form of a screw on the inner layer (44).

7. The eccentric endless screw pump or the eccentric endless screw motor according to claim 6, further characterized in that the butt joints (54) between proximal turns (53) of at least one wound metal strip (52) ) are soldered.

8. The eccentric endless screw pump or the eccentric endless screw motor according to claim 7, further characterized in that the butt joints (54) are laser welded.

9. The eccentric endless screw pump or the eccentric endless screw motor according to claim 1, further characterized in that the material of the outer layer (45) is formed by a corrosion resistant steel and / or highly resistant to abrasion.

10. - The eccentric screwless screw pump or the eccentric screwless motor according to claim 9, further characterized in that the steel is selected from the materials V2A, V4A.

11. The eccentric screwless screw pump or the eccentric screwless motor according to claim 1, further characterized in that the rotor (4) contains a core element (33), which is connected by dynamic connection and / or positive shape with the tube (34).

12. The eccentric screwless screw pump or the eccentric screwless motor according to claim 11, further characterized in that the tube (34) is positively connected with the core element (33) in the area of the valleys (47) threaded, so that the core element (33) is inserted under pressure only in the area of the valleys (47) of thread of the tube (34) with formation of at least one flat groove ( 48) which extends in the form of a screw.

13. The eccentric screwless screw pump or the eccentric screwless motor according to claim 11, further characterized in that at least one intermediate space is contained between the core element (33) and the tube (34). 49) which extends in the form of a screw.

14. The eccentric screwless screw pump or the eccentric screwless motor according to claim 11, further characterized in that the core element (33) is tubular in shape.

15. - The eccentric screwless screw pump or the eccentric screwless motor according to claim 11, further characterized in that the core element (33) is solid.

16. The eccentric screwless screw pump or the eccentric screwless motor according to claim 13, further characterized in that the at least one intermediate space (49) that extends in the form of a screw is filled with a mass.

17. The eccentric screwless screw pump or the eccentric screwless motor according to claim 13, further characterized in that the at least one intermediate space (49) extending in the form of a screw is empty.

18. The eccentric screwless screw pump or the eccentric screwless motor according to claim 1, further characterized in that the stator (3) has a wall (32) which is formed by an elastomeric mass.

19. The eccentric screwless screw pump or the eccentric screwless motor according to claim 1, further characterized in that the stator (3) is formed by a casing (19) with an elastomeric coating (32).

20.- The eccentric screwless screw pump or the eccentric screwless motor according to claim 19, further characterized in that the elastomeric mass has an essentially constant wall thickness along a large part of the stator extension (3).

21. The eccentric screwless screw pump or the eccentric screwless motor according to claim 1, further characterized in that the shell (19) has a configuration in the form of a screw, which is similar to that of the stator drill (twenty).

22. The eccentric screwless screw pump or the eccentric screwless motor according to claim 1, further characterized in that the casing (19) has a cylindrical configuration, and the casing (32) has a cylindrical outer peripheral surface.

23. A method for manufacturing a rotor of an eccentric screw pump or an eccentric screw motor, with a stator (3) containing a continuous stator hole (20), having a configuration in the form of a screw, the method characterized in that it comprises the steps: providing a cylindrical tube (51); coating the tube (51) with a metallic layer (52), in such a way that a double-walled structure (51, 52) is obtained; forming the double-walled structure (51, 52) to obtain the configuration in the form of a rotor screw (4).

24. The method according to claim 23, further characterized in that the cylindrical tube (51) is a seamless tube.

25. The method according to claim 24, further characterized in that the cylindrical tube (51) has a polished metallic outer peripheral surface.

26. - The method according to claim 23, further characterized in that the metal layer is formed by at least one metal strip (52).

27. The method according to claim 26, further characterized in that the metal band (52) is wound on the inner tube (51), so that the turns (53) abut one another essentially without slit.

28. The method according to claim 23, further characterized in that the butt joint (54) between proximal turns (53) is welded.

29. The method according to claim 23, further characterized in that the metal strip (52) is continuously heated before being wound on the tube (51).

30. The method according to claim 23, further characterized in that the double-walled structure (51, 52) is cold formed.

31. The method according to claim 30, further characterized in that before the cold forming a core element (33) is inserted into the double-walled structure (51, 52).

32. The method according to claim 31, further characterized in that the core element (33) has longitudinal ribs.