Patent ID: 12247628

DETAILED DESCRIPTION

Embodiments are described more fully below in sufficient detail to enable those skilled in the art to practice the system and method. However, embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. The following detailed description is, therefore, not to be taken in a limiting sense.

Various embodiments of the systems and methods described herein relate to universal joint assemblies, or U-joint assemblies, for transferring torque in a variety of drilling environments involving a down-hole mud motor including, for example, transferring torque between an eccentrically rotating rotor and a concentrically rotating output shaft of a mud motor to drive a drill bit or in traversing a bend in a housing of a mud motor. More specifically, this description discusses embodiments of a U-joint assembly that transmits torque across the articulating joint assembly, or between U-joint members, by maintaining a near constant face-to-face contact between a male U-joint member and a female U-joint member as the joint articulates.

Embodiments of the disclosed U-joint assembly and associated drive assemblies may be operated in any drilling environment with minimal wear or damage to the components due to a minimal number of components required to form the assemblies, the primary material used to manufacture the assembly components, and the ability for the U-joint assembly and drive assemblies to be operated in either a sealed and lubricated environment or, should a loss of sealing and lubrication occur, operated with only drilling fluid as a lubricating fluid.

Turning to the exemplary embodiments,FIGS.1A-1Dillustrate respective perspective-exploded, side-exploded, side-plan, and cross-sectional views of one embodiment of a U-joint assembly100for transmitting torque across an angled or articulating joint. In this embodiment, the U-joint assembly100may include a female U-joint member104defining a longitudinal axis L, as well as a male U-joint member102, a central ball seat106, and a retaining device108, all coaxially mounted along the longitudinal axis, L.

FIGS.2A-2Cillustrate respective perspective, side-plan, and cross-sectional views of one embodiment of the male U-joint member102. In this embodiment, the male U-joint member102may include a male-threaded end110separated from an opposing drive end112by a smaller diameter shaft114extending therebetween. The male-threaded end110may form a male threaded connection116configured to be threadably engaged directly or indirectly with an appropriate drive component such as, for example, a rotor of a mud motor or a drive shaft coupled with the rotor of the mud motor, as discussed below.

The drive end112may include four multi-angled faces118, each situated longitudinally at a 90-degree interval about an outer circumference or periphery of the drive end112. Each of the multi-angled faces may feature a crown126located at an apex of a first angled surface128and a second angled surface130where each of the first and the second angled surfaces128,130angle away from the crown126. Four convex radiused surfaces120may correspond to the four multi-angled faces118, each traversing between a crest122of each one of the multi-angled faces118to a root124of the adjacent multi-angled face118. As shown inFIG.2C, the drive end112may also include a conical end cavity132that extends from a circular opening134within the drive end112to a concave, semi-spherical bearing surface136at its termination.

FIGS.3A-3Dillustrate respective perspective, side-plan, longitudinal cross-sectional, and end cross-sectional views of one embodiment of the female U-Joint member104. In this embodiment, the female U-joint member104may include a male threaded end138and an opposing receptacle end140. The male threaded end138may form a male threaded connection configured to engage directly or indirectly with an appropriate driven component, such as, for example, a radial bearing or an output shaft of a mud motor, as discussed further below.

The receptacle end140may include a female threaded connection142and a cavity144extending away from the female threaded connection142. In this embodiment, the cavity144may include four flat surfaces146extending longitudinally from the cavity144at 90-degree intervals about an inner diameter145of the cavity144. Four concave radiused surfaces143may arc between each of the flat surfaces146and may align with or oppose the radiused surfaces120of the male U-joint member102when the drive end112of the male U-joint member102is inserted coaxially into the receptacle end140of the female U-joint member104. The cavity144may terminate in a circular receptacle148located at the bottom of the cavity144. A threaded lubrication channel147may extend longitudinally from an end of the male threaded end138to the circular receptacle148.

FIGS.4A-4Dillustrate perspective, top-plan, side-plan, and cross-sectional views of one embodiment of the central ball seat106, respectively. In this embodiment, the central ball seat106may include a flat circular base150having a centrally located shaft152that extends proximally-to-distally therefrom. In an assembled configuration, a distal end154of the shaft152may terminate in a convex semi-spherical bearing surface156configured to impinge upon the concave semi-spherical bearing surface136of the conical end cavity132of the male U-joint member102, discussed above. A grease passage158may be formed axially through the shaft152and the base150for lubrication purposes.

FIGS.5A-5Cillustrate respective perspective-exploded, side-exploded, and front-exploded views of one embodiment of the retaining device108. In this embodiment, the retaining device108may include first and second semi-circular segments160,162configured to clamp about the shaft114of the male U-joint member. Specifically, the first and the second semi-circular segments160,162may be held in alignment about the shaft114by two alignment sleeves164disposed within corresponding counterbores165located 180 degrees apart from one another within the second semi-circular segment162and two appropriate fasteners166(e.g., socket head fasteners). The fasteners166may secure the first and the second semi-circular segments160,162by extending through a pair of alignment apertures168formed within the first semi-circular segment160, through the alignment sleeves164disposed within the counterbores165, and into a corresponding pair of threaded apertures170formed in the second semi-circular segment162, as shown inFIGS.5A-5B. In one embodiment, the assembled retaining device108, formed from the assembled first and second semi-circular segments160,162, may also include a circumferential threading172about its circumference. The circumferential threading172may be threadably coupled with the female threaded connection142of the female U-joint member104.

Returning toFIGS.1C-1Dillustrating the assembled configuration of the U-joint assembly100, the retaining device108may be secured about the smaller diameter shaft114of the male U-joint member102using the fasteners166. In this regard, the retaining device108may be sized to provide an articulation offset, O, between the shaft114and the retaining device108when the retaining device108is secured about the shaft114. This articulation offset, O, provides sufficient space for radial movement of the shaft114within the retaining device108when the drive end112of the male U-joint member articulates within the cavity144of the female U-joint member104.

The circular flat base150of the central ball seat106may be received within the circular receptacle148located at the bottom of the receptacle cavity144of the female U-joint member104. In turn, the drive end112of the male U-joint member102may be inserted into the receptacle cavity144of the receptacle end140of the female U-joint member104, thereby causing the convex semi-spherical bearing surface156of the shaft152of the central ball seat106to be received by the concave semi-spherical bearing surface136of the conical end cavity132of the male U-joint member102, such that the male and the female U-joint members102,104may rotate and/or articulate about the longitudinal axis, L, with the bearing surfaces136,156impinging upon each other. The circumferential threading172of the retaining device108may be threaded into the female threaded connection142of the female U-joint member104to secure the female U-joint member104about the central ball seat106and the drive end112of the male U-joint member102.

In one embodiment, a single U-joint assembly100, as shown and discussed in relations toFIGS.1-5above, may be used in connection with a flex shaft180, shown inFIGS.6A-6B. Embodiments of the flex shaft180may feature opposing first and second ends182,184separated by a flexible shaft185disposed therebetween. The first end182of the flex shaft180may form a female threaded connection186, and the second end184of the flex shaft180may form a male threaded connection188.

FIGS.7A-7Cillustrate respective perspective-exploded, side-plan, and cross-sectional views of a drive assembly200including a single U-joint assembly100assembled to and used in concert with an embodiment of the flex shaft180. As assembled, the male threaded connection116of the male-threaded end110of the male U-joint102may be threaded into the female threaded connection186of the flex shaft180. The U-joint assembly100, and particularly the assembled drive assembly200, transmits torque between the male U-joint member102and the female U-joint member104through an interfacing of the angled and radiused surfaces spaced about the periphery of the drive end112of the male U-joint member102and about the inner diameter145of the cavity144of the receptacle end140of the female U-joint member104.

Specifically, and as shown inFIG.7C, as the drive end112of the male U-joint member102articulates within the cavity144of the female U-joint member104relative to (e.g., in a direction orthogonal to) the longitudinal axis, L, the first angled surface128of the drive end112positioned parallel to an articulation angle of the flex shaft180engages the corresponding opposing flat surface146(FIG.3A) situated longitudinally about the inner diameter145(FIG.3D) of the cavity144of the female U-shaped member102. At the same time, the second angled surface130on the opposing side of the drive end112, also positioned in parallel with the articulation angle of the flex shaft180, simultaneously engages the corresponding opposing flat surface146situated longitudinally about the inner diameter145of the cavity144of the female U-shaped member102. The crowns126positioned orthogonal to the engaged multi-angled surfaces118—or the crowns126between the first and the second angled surfaces128,130of the multi-angled surfaces118offset 90 degrees from the engaged first and second angled surfaces128,130—may engage the corresponding opposing flat surfaces146.

As the angle of the flex shaft180increases, an area of contact between the respective angled surfaces128,130of the male U-joint member102and the flat surfaces146of the female U-joint member104correspondingly increases, thereby transmitting torque from the male U-joint member102to the female U-joint member104. The angled surfaces128,130of the male U-joint member102and the flat surfaces146of the female U-joint member104may be configured such that the U-joint assembly100distributes the applied or driving torsional force over a combined surface area of at least 14 square inches, which spreads the force over a substantial flat surface and dramatically reduces wear on the joint and increases a life of the joint before failure.

The radiused surfaces120corresponding to each of the four multi-angled surfaces118of the drive end112of the male U-joint member102(FIGS.2A-2B), each traversing between the crest122of each one of the multi-angled faces118to the root124of the adjacent multi-angled face118, provide substantial resistance to shearing from high-torque power sections. Moreover, the central ball seat106facilitates smooth articulation with minimal wear, while the convex semi-spherical bearing surface156of the ball seat106, which is seated within the concave semi-spherical bearing surface136of the male U-joint member102, acts as a thrust bearing between the male and the female U-joint members102,104to support significant axial loading.

In this embodiment of the drive assembly200incorporating the flex shaft180, and due to the articulating nature of the U-joint assembly100and the flexible nature of the flex shaft180, a single U-joint assembly100accomplishes what has previously required two U-joint assemblies in existing designs, thereby saving money in both inventory, assembly time, and repair time required.

FIG.8provides a perspective view of an alternative embodiment of a drive end112aof the male U-joint member102. In this embodiment, the drive end112aincludes features identical to the drive end112ofFIGS.2A-2C, but contains a provision for the installation of a hardened roller or cylindrical bearing113within a cylindrical pocket115located on the crown122between each of the first and the second angled surfaces128,130. The addition of the cylindrical bearing113serves to reduce frictional wear between the crowns122and the flat surfaces146of the female U-joint member104during operation.

FIG.14illustrates a perspective view of another alternative embodiment of a drive end112bof the male U-joint member102. In this embodiment, the drive end112bmay include a plurality of rectangular-shaped extensions that protrude radially outward from the drive end112b. In one embodiment, the extensions may take the form of a plurality of machined, rectangular-shaped inserts402, each situated longitudinally at equal intervals about and extending radially outward from an outer circumference or periphery of the drive end112b. The rectangular-shaped inserts402may each be received within and retained by a corresponding receptacle404formed in an outer radial surface406of the drive end112b. In other embodiments, the rectangular-shaped extensions may take any appropriate size, shape, type, and/or configuration. For example, in one embodiment, they may be incorporated directly into the drive end112bas manufactured protrusions.

FIGS.15A-15Dillustrate respective perspective, longitudinal side, end, and bottom views of one embodiment of the rectangular-shaped insert402of the drive end112bof the male U-joint member102. In this embodiment, the rectangular-shaped insert402may have a generally rectangular profile formed from two opposing longitudinal sides408(i.e., identical left and right sides), two opposing ends410, a top side412, and a bottom side414. Each of the opposing left and right sides408may include a planar lower surface415and two upper angular surfaces416extending axially from a side apex or crest418inward toward a center of the insert402. Similarly, the top side412may include two angular surfaces420extending axially from a top crest422downward toward the center of the insert402. In one embodiment, each of the side and top angular surfaces416and420may be angled away from the side and top crests418and422, respectively, by an angle between 1.5 and 5 degrees.

The bottom side414and the planar lower surfaces415of the opposing left and right sides408of the insert402may be received and retained within the corresponding receptacle404, such that the angular surfaces416and420of the opposing left and right sides408and the top side412, respectively, protrude outward from the receptacle404, as shown inFIG.14. The inserts402may be retained within the receptacles404in any appropriate manner including, for example, an interference fit.

FIGS.16A-16Billustrate respective side-plan and cross-sectional views of another embodiment of a receptacle end140bthe female U-joint member104. In one embodiment, the receptacle end140bmay define the longitudinal axis, L, and be configured to coaxially receive the drive end112bof the male U-joint member102, discussed above in relation toFIGS.14and15A-15D.

In this embodiment, the receptacle end140bmay include a similar configuration to the receptacle end140, discussed above in relation toFIGS.3A-3D, but may include a female threaded connection142band a cavity144bextending inward from the threaded connection142b. The receptacle cavity144bmay include a plurality of rectangular channels or grooves430situated radially at equal intervals about an inner diameter432of the cavity144bin a pattern that mirrors the pattern of the rectangular-shaped inserts402of the drive end112bof the male U-joint member102, discussed above, where each of the rectangular channels or grooves430extends radially outward from an inner diameter432of the cavity144band is defined by three planar drive surfaces434.

In this embodiment, when the drive end112bof the male U-joint member102is received coaxially within the receptacle cavity144bof the female U-joint member104, as shown inFIGS.17A-17B, the rectangular inserts402protruding from the drive end112bare received within aligned ones of the rectangular channel/grooves430such that the angular surfaces416and420of the inserts402oppose corresponding ones of the drives surfaces434of the rectangular grooves430.

Under normal drilling operations, eccentric radial movement of the rotor within the stator and/or the angular bend of either a fixed bend or an adjustable angle housing causes the drive end112bof the male U-joint member102to move at various articulation angles about the pivot of the central ball seat106, relative to the longitudinal axis, L, defined by the female U-joint member140b. This articulation relative to the longitudinal axis, L, causes select ones of the angular surfaces416,420to come into contact with the corresponding opposing drive surfaces434of the rectangular grooves430formed in the female receptacle end140b. This contact between the respective side and top angular surfaces416and420of the inserts402and the opposing drive surfaces434of the rectangular grooves430allows the resulting force of the torque applied to the drive head112bto be transmitted across a contact area between the angular surfaces416,420and the opposing drive surfaces434in a direction that is perpendicular to the angular surfaces416and420, thereby transmitting the torsional forces from the drive head112bof the male U-joint member to the receptacle end140bof the female U-joint member in a manner that eliminates the wedge effect that prior art balls and barrel rollers create in operation.

The drive end112bdiffers from the prior art ball and barrel rollers in that the assembled U-joint components may be operated in any drilling environment with minimal wear or damage to the components. In addition, the mated drive end112bof the male U-joint member102and the receptacle end140bof the female U-joint member104may either be operated in a sealed, lubricated environment or, should the loss of sealing and lubrication occur, the assembly may function as designed with only drilling fluid as a lubricating fluid. As discussed above, current ball-and-groove or barrel roller-and-groove arrangements have minimal points of contact between the driving and driven components, which concentrates the applied torque to such a small area that the material yields immediately causing surface deformation, which leads to rapid wear and failure.

FIG.9provides a perspective view of an alternative embodiment of a retaining device108aused in assembling the U-joint assembly100. In this embodiment, the retaining device108aincludes features identical to the retaining device108detailed inFIGS.5A-5C, but includes a retaining shoulder109, which provides a leverage surface for the installation of a sealing boot or other gasket (not shown).

FIGS.10A-10Billustrate side and cross-sectional views of one embodiment of an alternative drive assembly250. In this embodiment, the drive assembly250may include two U-joint assemblies100connected by a common cylindrical shaft252having integral provisions for a sealing boot installation. Specifically, and as shown inFIG.10Cshowing a drive sub-assembly254comprising two of the male U-joint members102coupled by the common cylindrical shaft252extending therebetween, the shaft252may having opposing first and second ends256,258. Each of the first and the second ends256,258may include an O-ring groove260, a retaining shoulder262, and a radiused surface264configured to reduce the force of the drilling fluid bearing on the drive shaft boot.

FIGS.11A-11Billustrate side and cross-sectional views of one embodiment of an alternative drive assembly300. In this embodiment, the drive assembly300may include a flex shaft180asimilar to the flex shaft180ofFIGS.6A-6B. Flex shaft108amay be identical to the flex shaft180, except rather than a female connection, the first end182of the flex shaft180amay form the drive end112of the male U-joint member102. As assembled, the female U-joint member104, the central ball seat106, and the retaining device108may be assembled to the drive end112of the flex shaft180bin the manner discussed above in relation toFIGS.1C-1D.

FIG.12illustrates a side view of the drive assembly300ofFIGS.11A-11B, as assembled to an upper male radial bearing310, which is, in turn, assembled to an output shaft312of a mud motor and placed within a sectional view of a fixed bend housing314.

The components forming the U-joint assembly100and drive assemblies200,250, and300may be formed of any appropriate material such as, for example, 17-4 stainless steel, heat treated to a PH900 condition after machining, primarily for its corrosion resistance, abrasive resistance, and torsional strength. Some embodiments may be formed of 4145HT, 4330 V MOD, and/or 4130HT steels given their abilities to harden the drive surfaces of the male and the female U-joint members. Both the male and the female U-joint members102,104are repairable via welding and the resurfacing of worn areas through either machining or hand grinding.

Embodiments of the male U-joint member102, the flexible shaft180,180b, and the common cylindrical shaft252may be either machined from billet or closed die forged to near net, with machining used to complete the features such as the cavity144terminating in the concave semi-spherical bearing surface136and the angled surfaces128,130of the male U-joint member102. As new, higher torque power sections become available, the closed die forging process may become the preferred method of manufacture for these components.

Embodiments of the U-joint assembly100and the drive assemblies200,250,300may be implemented in any high torque application in which the driving and driven components require an angular connection. As discussed above, exemplary operational environments include transferring torque in a variety of drilling environments involving a down-hole mud motor such as transferring torque between an eccentrically rotating rotor and a concentrically rotating output shaft of a mud motor to drive a drill bit or in traversing a bend in a housing of a mud motor.

Embodiments the disclosed U-joint assembly and drive assemblies differ from existing solutions in that the assembled components may be operated in any drilling environment with minimal wear or damage to the components due to the elegant design requiring minimal interfacing components, the manufacturing materials, and the ability to operate within or in absence of a sealed, lubricated environment. Existing U-joints and/or drive shafts utilizing ball and groove arrangements feature minimal points of contact between the driving and driven components. This configuration concentrates the applied torque on a small area and causes the material to yield immediately, resulting in surface deformation and leading to rapid wear and failure. The unique configuration of the disclosed U-joint assembly distributes the applied torsional forces through a combined surface area of 14 square inches, which spreads the force over substantial flat surfaces that minimize component wear and drastically increase component life.

FIG.13provides a flowchart depicting an exemplary method (350) of using embodiments of the U-joint assembly100, incorporating an embodiment of the male and the female U-joint members disclosed herein, and drive assemblies200,250,300to transmit torque across an articulating or angled joint. In this embodiment, the method (350) may begin with operably coupling the U-joint100between a drive component such as a mud motor rotor and a driven component such as a mud motor output shaft (352). In one embodiment, the male U-joint member102may be coupled with or incorporated into the flexible rod180,180b. In this regard, the female U-joint member104may be operably coupled with the driven component, or the mud motor output shaft312, as shown inFIG.12, and the male U-joint member102may be operably coupled with the drive component, or the mud motor rotor, via the flexible shaft180,180b.

The U-joint assembly100may be positioned at an angled or articulating joint such as, for example, a bend in the mud motor housing314(354), and the male U-joint member may be articulated relative to or in a direction orthogonal to the longitudinal axis, L, defined by the female U-joint member104until the male U-joint member102is disposed at an articulation angle relative to the longitudinal axis, L (356). The drive component may then be actuated such that a torque is transmitted across the angled U-joint assembly, or from the male U-joint member102coupled with the drive component to the female U-joint member104coupled with the driven component (358). The transmission of torque occurs, in an example employing the drive end112of the male U-joint member102and the receptacle end140of the female U-joint member104, through a contact between select ones of the first and the second angled surfaces128,130, which combine to form the multi-angled surfaces118, that are positioned parallel to the articulation angle of the male U-joint member relative to the longitudinal axis, L, and opposing ones of the flat surfaces146of the cavity144of the female U-joint member102. In another example employing the drive end112bof the male U-joint member102and the receptacle end140bof the female U-joint member104, the transmission of torque occurs through a contact between select ones of the side and the top angular surfaces116,120and opposing ones of the drive surfaces434of the rectangular grooves430formed in the receptacle cavity144bof the female U-joint member.

Although the above embodiments have been described in language that is specific to certain structures, elements, compositions, and methodological steps, it is to be understood that the technology defined in the appended claims is not necessarily limited to the specific structures, elements, compositions and/or steps described. Rather, the specific aspects and steps are described as forms of implementing the claimed technology. Since many embodiments of the technology can be practiced without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.