Background

[0001] This disclosure relates generally to the field of rotary magnetic couplings. More specifically, the disclosure relates to rotary magnetic couplings having a high torque transfer capacity while having a relatively small external diameter.

[0002] Rotary magnetic couplings are used to transfer rotational energy from a source thereof, for example, an electric motor, to a device that uses the rotational energy (a load), for example, a pump. Rotary magnetic couplings have torque transfer capacity that is related to the numbers of and/or sizes of magnetic elements in a drive member (coupled to the source of rotational energy) and a driven member (coupled to the load). In some circumstances, for example pumps deployed in subsurface wellbores, a rotary magnetic coupling requires a large torque transfer capacity while having a relatively small external diameter in order not to obstruct the flow of fluid in a wellbore. Rotary magnetic couplings used for such purposes therefore are relatively long parallel to the longitudinal axis. Such length may make manufacture of the rotary magnetic coupling difficult because of the need for very small clearances between the drive member and the driven member.

Brief Description of the Drawings

[0003] FIG. 1 is a cross section through an example embodiment of one module of a modular rotary magnetic coupling according to the present disclosure.

[0004] FIG. 2 is a cross section through a different example embodiment of one module of a modular rotary magnetic coupling according to the present disclosure.

[0005] FIG. 2A shows an expanded view of part of the cross section shown in FIG. 2.

[0006] FIG. 3 shows an oblique cut away view of an example embodiment of a rotary magnetic coupling having three modules. [0007] FIG. 4 shows a detailed view of a connection between two modules of the embodiment shown in FIG. 3.

[0008] FIG. 5 shows a detailed view of a pressure barrier between adjacent modules of the coupling shown in FIG. 4.

[0009] FIG. 6 shows an example embodiment a modular outer housing.

[0010] FIG. 7 shows an exploded view of an example embodiment of a longitudinally endmost module.

[0011] FIG. 7 A shows a detailed view of a pressure barrier adapter coupled to an interior of the housing and to the pressure barrier.

[0012] FIG. 8 shows coupling a housing section with a drive section inserted therein to the example embodiment of endmost module shown in FIG. 7.

[0013] FIG. 9 shows the housing section of FIG. 8 coupled to the endmost module of

FIG. 7.

[0014] FIG. 10 shows an enlarged view of attaching a pressure barrier module to the driven section of an adjacent module.

[0015] FIG. 11 shows a detailed view of coupling a drive member to a longitudinally endmost module.

[0016] FIG. 12 shows an assembled view of a rotary magnetic coupling.

Detailed Description

[0017] A cross-section through an example embodiment of a rotary magnetic coupling module is shown in FIG. 1. The rotary magnetic coupling module ("module") 10 comprises a drive element 11 which may be coaxially disposed about the exterior of a driven element 20. In other embodiments, the driven element may be disposed coaxially externally to the drive element.

[0018] The drive element 11 may comprise a plurality of circumferentially disposed magnetic elements 12, which in the present embodiment may be individual permanent magnets each in the shape of a circumferential segment, although the magnet shape is not a limitation on the scope of the present disclosure. The magnets 12 in the drive element 11 may be alternatingly, radially polarized as shown in FIG. 1. An exterior surface of the magnets 12 may be enclosed in a drive shaft 11 A, which in the present example embodiment may be high strength ferromagnetic material such as a low carbon steel tube to act both to transfer rotational energy to the magnets 12 and to act as a flux closure for the magnets 12. An interior surface of the magnets 12 may be enclosed by a magnet retainer 14 such as may be made from plastic or from metal such as an alloy sold under the trademark INCONEL, which is a registered trademark of Huntington Alloys Corp., Huntington, WV, or any other non-magnetic material. The magnet retainer 14 may exclude fluid under pressure from entering the interior of the drive element 11 between the drive shaft 11 A and the magnet retainer 14. The drive shaft 11 A may be rotationally coupled to a source of rotational energy, for example and without limitation, an electric motor, hydraulic motor or pneumatic motor. Features to enable such rotational connection will be further explained with reference to FIG. 3 and FIG. 11. In the present example embodiment, the driven element 20 may be disposed coaxially inside the drive element 11. The driven element 20 may include an output shaft 20C which may be coupled to a rotating load (not shown), e.g., and without limitation a pump. The output shaft 20C may be made from low carbon steel or similar ferromagnetic, high strength material so as to enable transfer or rotational energy to the load (not shown) and to act as a flux closure for a plurality of magnetic elements 18, however, nonmagnetic or nonmetallic materials may be used in other embodiments. In the present example embodiment, the magnetic elements 18 may comprise permanent magnets each in the shape of a circumferential wedge segment disposed about the exterior of the output shaft 20C, although other shapes for the magnets may be used in other embodiments. In the present example embodiment the magnets 18 may be radially alternatingly polarized as shown in FIG. 1. The magnets 18 may be retained in place by another magnet retainer 17 which may be similar in composition to the magnet retainer 14 in the drive element 11 or may be a different material composition. [0020] Another embodiment of a rotary magnetic coupling module 10 is shown in FIG.

2. The rotary magnetic coupling module shown in FIG. 2 may include substantially the same components as the rotary magnetic coupling module shown in FIG. 1, wherein the difference between the rotary magnetic coupling module shown in FIG. 1 and the present example embodiment of FIG. 2 is the arrangement of the magnets, shown at 12A on the drive element 11 and at 18A on the driven element 20. In the present example embodiment, the magnets may be configured in a Halbach arrangement, wherein adjacent magnets are polarized in a continuous, unidirectional rotating pattern. In other embodiments, adjacent magnets may be polarized at 90 degrees polarization direction displacement (in quadrature) with respect to each other as shown by the arrows on each magnet indicating the polarization direction in FIG. 2A.

[0021] An enlarged view of part of the section of the drive element of FIG. 2 is shown in

FIG. 2 A. The drive shaft 11 A may include at least one, and may include a plurality of recesses 12R in its interior surface to receive selected ones of the magnets, such magnets being shown at 12Q. In the embodiment shown in FIG. 2A, magnets adjacent to the one or more magnets 12Q disposed in a corresponding recess 12R, such magnets being shown at 12P, may be disposed between the magnets 12Q received in respective recesses 12R. The one or more magnets 12Q disposed in a recess may be polarized in a direction substantially transverse to a radial dimension of the drive element, while the adjacent magnets 12P are polarized in alternating radial directions (similar to the magnets shown in FIG. 1). A possible advantage of using the Halbach magnet arrangement is that by stepping into the ferromagnetic structures of each magnetic element, the quadrature polarized magnets 12Q physically "lock" into the structure, preventing the magnets 12Q, 12P from slipping within the drive element 11 in the case of adhesive or bonding failure. The Halbach magnet arrangement may also provide greater torque transmission capacity for any give size and magnetization of magnets than other arrangements of magnets (e.g., as shown in FIG. 1).

[0022] A similar magnet/recess structure may be used in the driven element 20 where the magnets 18 are prevented from slipping against the output shaft 20C in the event of an adhesive or bonding failure. The Halbach magnet arrangement, as explained above, may provide two possible benefits. First, the Halbach magnet arrangement provides a magnetic keying feature such that the magnets are locked in place and will remain in place even in the event of bonding. The Halbach magnet arrangement may also enhance the performance of the rotary magnetic coupling by increasing the amount of torque that may be transmitted from the drive element to the driven element for any particular size magnets used.

[0023] The foregoing two example embodiments of arrangements of magnetic elements shown in FIGS. 1 and 2 are not intended to limit the scope of the present disclosure. In both embodiments of FIGS. 1 and 2, the driven element 20 may be enclosed in a pressure barrier 16. The pressure barrier 16 may be assembled from longitudinal segments as will be further explained below. The pressure barrier 16 may be made from high strength, nonmagnetic metal such as the INCONEL® alloy described above or any other nonmagnetic material.

[0024] FIG. 3 shows an oblique cut away view of an example rotary magnetic coupling

50 including three rotary magnetic coupling modules 10 according to the present disclosure. Each rotary magnetic coupling module 10 may include a drive element 11 and a driven element 20 substantially as explained with reference to FIGS. 1 and 2. A longitudinal endmost one of the rotary magnetic coupling modules 10, shown on the left hand side of FIG. 3 may have an output end pressure barrier adapter 22 sealingly engaged with an interior surface of a housing (28 in FIG. 4) and locked in place therein such as by threading, pins, capscrews or other releasable attachment device. The foregoing will be explained in more detail with reference to FIG. 7A. An interior opening 22A in the output end pressure barrier adapter 22 may provide passage for an output coupling 20A on the output shaft 20C of the foregoing module 10. The output coupling 20 A may be rotationally coupled to a rotating load (not shown) for example and without limitation a pump. Each rotary magnetic coupling module 10 may be disposed inside a respective housing 28. Each of the rotary magnetic coupling modules 10 may be rotatably supported in its respective housing 28 by, e.g., journal bearings or hydrodynamic bearings as will be further explained below. [0025] Each of the rotary magnetic coupling modules 10 coupled to an adjacent rotary magnetic coupling module 10 may have its respective output shaft 20C coupled to the adjacent rotary magnetic coupling module's output shaft using any form of torque transmitting feature. In the present example embodiment, each output shaft 20C may have an output coupling 20A that may be a splined shaft. The splined shaft may fit inside a splined opening 20B in the adjacent module's output shaft 20C. Other examples of torque transmitting features may include, without limitation, mating male and female profile features, pins inserted into holes, and threads.

[0026] The housing 28 associated with each rotary magnetic coupling module 10 may be connected to the housing 28 of the adjacent rotary magnetic coupling module 10, for example, by forming male and female threads on adjacent longitudinal housing ends.

[0027] The longitudinal endmost rotary magnetic coupling module 10 to which the rotational input is provided by the source of rotational energy (not shown) is shown on the right hand side of FIG. 3 and may include a pressure barrier end cap 24 threadedly coupled to the pressure barrier 16 and sealed with a seal ring such as an o-ring. The drive shaft adapter 26 may provide rotational coupling between the drive element 11 and the source of rotational energy (not shown).

[0028] The longitudinal endmost housing 28 at the output coupling 20A end thereof may include an adapter 29 coupled thereto for connecting the coupling 50 to any rotating load apparatus (not shown) or other structure. The adapter 29 may include an internal reduced diameter rim 29A that retains the output end pressure barrier adapter 22 inside the housing 28 and may also provide a surface against which the pressure barrier adapter 22 may form a static seal. A corresponding adapter 31 may be coupled to the housing 28 at the input end of the rotary magnetic coupling 50, shown on the right hand side of FIG. 3. The adapter 31 may include an internal rim 31A to retain the pressure barrier end cap 24 within the housing 28.

[0029] FIG. 4 shows an enlarged view of a connection between two adjacent rotary magnetic coupling modules 10. The respective housings 28 may be coupled to each other by forming female threads 28A on one longitudinal end thereof and engaging such threads with mating male threads 28B formed on the opposed longitudinal end of the adjacent rotary magnetic coupling module 10. The threads 28A, 28B may be flush joint (acme) threads or any other suitable threads so that the exterior diameter of the housings 28 is substantially constant along their length. A pressure barrier connection (explained below) may provide sealed connection between pressure barriers 16 surrounding the driven elements of the connected rotary magnetic coupling modules 10. The pressure barrier connection may comprise a pressure barrier back end 16A coupled to the pressure barrier 16 proximate an exterior of an input end of the output shaft 20, a pressure barrier input end adapter 34 sealingly engaged with an interior of the pressure barrier back end 16A and a pressure barrier front end adapter 36 sealingly engaged with the pressure barrier input end adapter 34 and coupled to the pressure barrier 16 proximate an output end of the adjacent output shaft 20C. The pressure barrier input end adapter 34 may include seal grooves 34A, 34B for holding therein seal rings such as face to face seals or diametric seals to sealingly engage the pressure barrier back end 16A and the pressure barrier front end 36. The pressure barrier 16, including the pressure barrier back end 16A and pressure barrier input end adapter 34 may be rotatably supported inside an interior surface of the drive shaft 11 A using journal bearings 32 such as may be made from metal carbide, e.g., tungsten carbide or any other suitable bearing materials. Some embodiments may use hydrodynamic bearings. The drive shaft 11 A may be rotatably supported in the respective housing 28 using similar composition carbide journal bearings 30 (or any other suitable bearing material). Some embodiments may use hydrodynamic bearings. Similarly, the pressure barrier 16 may be rotatably supported on the exterior of the output shaft 20 using journal bearings 35. Some embodiments may use hydrodynamic bearings. Adjacent drive shafts 11 A may be rotationally coupled to each other using pins 37 or any other suitable torque transmitting feature. The pressure barrier 16 enables fluid on the exterior of the pressure barrier adapter (22 in FIG. 3) to enter the interior thereof and act as a lubricant for all of the bearings that rotatably support the driven element (20 in FIG. 3) within the pressure barrier 16. The pressure barrier 16 also separates such fluid from lubricating fluid, e.g., oil, disposed on the input end of the rotary magnetic coupling. Such arrangement provides full fluid separation without the need for any rotating seals.

[0031] FIG. 5 shows a detailed view of the connection between the pressure barrier back end 16A, the pressure barrier input end adapter 34 and the pressure barrier front end 36. The pressure barrier input end adapter 34 may be threadedly coupled to both the pressure barrier back end 16A and the pressure barrier front end 36 (of the adjacent module). A tool engagement feature 34D may be provided in the pressure barrier input end adapter 34 to facilitate threaded engagement of the pressure barrier adapter 34 to the pressure barrier back end 16A. The tool engagement feature 34D may be any device enabling a tool to engage the pressure barrier input end adapter 34 to apply torque thereto, including, without limitation, holes for a pin spanner, wrench flats or splines. Journal bearings 35 or hydrodynamic bearings may be used to rotatable support the pressure barrier front end 36 inside the drive shaft 11.

[0032] FIG. 6 shows assembled sections of the housing 28 including the output shaft end adapter 28C and one or more journal bearings 38, or, for example, hydrodynamic bearings, substantially as described above.

[0033] FIG. 7 shows an exploded view of assembly of a single module prior to insertion into its respective housing. The drive element 11 may be preassembled by inserting the magnets 12 to form a circumferential arrangement as explained with reference to FIGS. 1 and 2. The magnet retainer (14 in FIGS. 1, 2) may be inserted into the interior of the magnets 12. The magnet retainer (14 in FIGS. 1, 2) may be hermetically sealed to exclude entry of any fluid into the space occupied by the magnets 12. The pressure barrier 16 with front end adapter 36 coupled to one end and back end 16A may be inserted into the interior of the pressure barrier 16. The pressure barrier output end adapter 22 may be inserted into the interior of the pressure barrier front end 36; wherein thrust bearings 40A, 40D such as metal carbide bearings, PDC bearings or any other bearing material suitable for the environment in which the coupling is used, and spring washers 40B, 40C such as wave washers or bellville washers may be inserted between the pressure barrier output end adapter 22 and the pressure barrier front end 36. The driven element 20, including drive shaft 20C and magnets 18 may then be inserted inside the pressure barrier 16. The pressure barrier input end adapter 34 may then be threadedly coupled to the back end 16A of the pressure barrier 16. The foregoing may be the rotary magnetic coupling module 10 closest to the rotating load (not shown) to which the rotary magnetic coupling 50 is attached or rotationally coupled to.

[0034] An enlarged view of an embodiment of a pressure barrier output end adapter 22 coupled to the housing 28 and to the pressure barrier is shown in FIG. 7A. The pressure barrier output end adapter 22 may be affixed to the interior of the housing 28 using, for example and without limitation, threads, locking rings, and in the present example embodiment, capscrews 21. An exterior surface of the pressure barrier output adapter 22 may be sealed to an interior surface of the housing 28 using a seal ring such as an o-ring 19. An interior surface of the opening in the pressure barrier input end adapter 22 for the output shaft 20A may be sealed to the exterior surface of the pressure barrier 16 using a seal such as an o-ring 19. The arrangement of pressure barrier output end adapter 22 sealed inside the housing 28 and sealed to the pressure barrier 16 enables fluid on the output shaft side of the rotary magnetic coupling (50 in FIG. 1) to be fully separated from fluid on the input side of the rotary magnetic coupling without the need to use rotating seals.

[0035] FIG. 8 shows connection of the drive element 11 of an adjacent rotary magnetic coupling module 10 to the input end of the assembled module shown in FIG. 7. The adjacent rotary magnetic coupling module drive element 11 may be moved longitudinally until its pressure barrier front end 36 is proximate the pressure barrier input end adapter 34 threadedly engaged in the pressure barrier adapter 34. The pressure barrier 16 in the adjacent module 10 may be rotated to engage the threads in the pressure barrier front end 36 with the pressure barrier input end adapter 34. Referring to FIGS. 9 and 10, the input shaft 11 of the adjacent module 10 may be moved longitudinally away from the assembled module 10 enough to expose tool engaging features 34C in the pressure barrier input end adapter 34 and in the pressure barrier back end 16A in the assembled rotary magnetic coupling module. The present example tool engaging features 34C may be in the form of openings for a pin spanner, however, as previously explained the tool engaging features 34C may be any other type of tool engaging feature to enable application of torque, including, without limitation, wrench flats or splines. The pressure barrier input end adapter 34 and the pressure barrier front end 36 of the adjacent rotary magnetic coupling module 10 may then be tightened to a predetermined thread torque. Following such assembly and torquing of the threads, the driven element 20 of the adjacent rotary magnetic coupling module 10 may be inserted inside the pressure barrier 16 thereof. The foregoing procedure may be repeated for a selected number of modules 10.

[0036] Referring to FIG. 11, when the last module is assembled to the set of modules for any particular rotary magnetic coupling, the pressure barrier end cap 24 may be inserted into the pressure barrier back end 16A of the longitudinally endmost rotary magnetic coupling module 10. The pressure barrier end cap 24 may be engaged to the interior of the pressure barrier back end 16A using a thrust bearing 24 A and a spring washer 24B. After completion of the foregoing assembly, the drive shaft adapter 26 may be coupled rotationally to the first drive element 11 such as through its drive shaft using pins, spline or any other torque transmitting feature. The fully assembled set of modules may then be inserted into the housing 28 (which itself may be assembled from segments as explained with reference to FIG. 6. FIG. 12 shows the assembled rotary magnetic coupling 50.

[0037] A rotary magnetic coupling according to the various aspects of the present disclosure may enable transmitting high torque in a relatively small diameter device by enabling assembly of a selected number of longitudinal segments to provide the required amount of torque coupling capacity. The longitudinal segments may be relatively easy to manufacture and may be separately serviced or replaced as needed.

[0038] While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.