Abstract:
A hybrid elastomer/metal on metal motor for a helical gear device includes a rotor and stator comprising a hydraulic motor that produces work when a working fluid is pumped therethrough. The improvement involves the stator being, for part of its length, a conventional or even wall stator, using an elastomer to form a seal against the moving rotor. The stator&#39;s remaining length comprises a profiled rigid surface that forms a seal directly with the moving rotor. This gives the motor the high efficiency of the elastomer sealing against the rotor, and simultaneously provides a backup of the stator&#39; s rigid section allowing continued motor operation at reduced efficiency, if the elastomer part failed in service. The invention also includes combinations of a regular disk stack with a rubber lining, a rigid material disk stack (or unitized element) and a circular rigid sleeve which react to rotor sideloading while permitting proper rotor orbiting.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This bypass continuation-in-part application claims priority under 35 U.S.C. §120 of international patent application PCT/US2015/015404 filed on Feb. 11, 2015 entitled HYBRID ELASTOMER/METAL ON METAL MOTOR, which in turn claims the benefit under 35 U.S.C. §119(e) of Provisional Application Ser. No. 61/938,964 filed on Feb. 12, 2014 entitled HYBRID ELASTOMER/METAL ON METAL MOTOR and all of whose entire disclosures are incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of Invention 
         [0003]    This invention relates generally to motors, and more particularly, to hydraulic motors that produce work when a working fluid is pumped through it. 
         [0004]    2. Description of Related Art 
         [0005]    Today&#39;s downhole drilling motors usually are of the convoluted helical gear expansible chamber construction because of their high power performance and relatively thin profile and because the drilling fluid is pumped through the motor to operate the motor and is used to wash the chips away from the drilling area. These motors are capable of providing direct drive for the drill bit and can be used in directional drilling or deep drilling. In the typical design the working portion of the motor comprises an outer housing having an internal multi-lobed stator mounted therein and a multi-lobed rotor disposed within the stator. Generally, the rotor has one less lobe than the stator to facilitate pumping rotation. The rotor and stator both have helical lobes and their lobes engage to form sealing surfaces which are acted on by the drilling fluid to drive the rotor within the stator. In the case of a helical gear pump, the rotor is turned by an external power source to facilitate pumping of the fluid. In other words, a downhole drilling motor uses pumped fluid to rotate the rotor while the helical gear pump turns the rotor to pump fluid. In prior systems, one or the other of the rotor/stator shape is made of an elastomeric material to maintain a seal there between, as well as to allow the complex shape to be manufactured. 
         [0006]    One of the primary problems encountered when using the standard style of stators is that the profile lobes are typically formed entirely of elastomer. See  FIG. 1 . Since swelling due to thermal expansion or chemical absorption is proportional to the elastomer thickness different parts of the profile expand differently. Moineau, U.S. Pat. No. 1,892,217 and Bourke, U.S. Pat. No. 3,771,906 disclose stators constructed from elastomeric materials of varying section thickness of the elastomer. U.S. Pat. No. 5,832,604 to Johnson et al. discloses a rigid stator made of a disk stack and elastomeric lining. The elastomer allows the stator to begin a run with a tight seal around a rotor from the elastomer or rubber lining, which gives the motor high efficiency. 
         [0007]      FIGS. 1-2  depict a prior art metal rotor and a rubber-lined stator having a rubber or elastomeric stator lining and a metal stator tube. This conventional power section stator configuration comprises a profiled rubber section where the rubber has varying thickness.  FIGS. 3-4  depict a prior art metal rotor and a metal on metal stator having a metal stator lining and a metal stator tube. Furthermore,  FIGS. 5-6  depict another prior art version of a rubber-lined metal stator that utilizes an internally-shaped tube and a profiled rubber section. In this version, referred to as an “even wall power section,” the profile of the rubber has an even thickness, as shown most clearly in  FIG. 6 , as opposed to uneven thickness of the rubber portion in  FIG. 2 . 
         [0008]    However, under difficult conditions of load and temperature, the rubber may not last long enough to finish the planned run. The usual failure mechanism for these conventional power section stators and even wall power section stators is chunking of the rubber as it fatigues due to cyclic loading. The chunking usually commences at the end of the stator where the rotor is connected to the bearing assembly of the motor due to the sideload from the constant velocity joint or flex shaft. Correcting this failure would normally require a time consuming and costly trip out of the well to change the stator. The inventors have contemplated and solved this problem with the realization that a motor with an elastomeric stator could keep operating under such conditions with some modifications that would increase durability and reliability in operation, as will be discussed in greater detail below. 
         [0009]    All references cited herein are incorporated herein by reference in their entireties. 
       BRIEF SUMMARY OF THE INVENTION 
       [0010]    This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify essential features of the claimed subject matter, nor is it intended for us in determining the scope of the claimed subject matter. 
         [0011]    A stator for a hydraulic motor having an elongated and helically-lobed rotor rotatably disposed therein is disclosed. The stator comprises: a cylindrical stator housing; a first section within the stator housing comprising a generally tubular configuration having elastically deformable elastomeric material defining a first helically convoluted chamber section; and a second section adjacent the first section and fixed within the stator housing, and wherein the second section comprises at least one of: a rigid section (e.g., a plurality of rigid disks stacked together, a unitized member, etc.) comprising a second helically convoluted chamber section matching the first helically convoluted chamber section wherein said first and second helically convoluted chambers are rotationally aligned in a continuous helical relationship to form a helically convoluted chamber for supporting the rotor; and a rigid sleeve defining a cylindrical chamber section for further supporting the rotor. 
         [0012]    A method of making a stator for a hydraulic motor adapted to have an elongated and helically-lobed rotor rotatably disposed therein is disclosed. The method comprises: forming a cylindrical stator housing; providing an alignment core tool having at least one of at least one rigid section (e.g., a disk stack, or a unitized member, etc.) positioned thereon and at least one rigid sleeve positioned thereon, wherein the at least one rigid section (e.g., a disk stack or a unitized member, etc.) comprises a helically-convoluted chamber and the at least one rigid sleeve has a cylindrical chamber section; inserting the alignment core tool with the at least one rigid section (a disk stack, or a unitized member, etc.) and the at least one sleeve thereon into the cylindrical stator housing; securing the at least one rigid section (e.g., a disk stack, a unitized element, etc.) and the at least one sleeve to the stator housing; replacing the alignment core tool with an injection core tool, the injection core tool comprising a predetermined stator profile that comprises at least one more lobe than a number of the rotor lobes; injecting an elastomeric material through the stator casing to form a tubular elastomeric section adjacent the at least one of the rigid section (e.g., a disk stack, or a unitized member, etc.) or the at least one rigid sleeve; curing the elastomeric material to form a helically convoluted chamber therein that is aligned with at least one of the helically-convoluted chamber of the at least one rigid section (e.g., a disk stack or at a unitized member, etc.) and of the cylindrical chamber section; and removing the injection core tool. 
         [0013]    A method of making a stator for a hydraulic motor adapted to have an elongated and helically-lobed rotor rotatably disposed therein is disclosed. The method comprises: forming a cylindrical stator housing; forming a plurality of disks, each one of the disks having a respective cutout or aperture such that when the plurality of disks are formed into a disk stack, at least one bleed hole path is formed to permit the passage of a material therethrough; providing an alignment core tool having at least one of at least one disk stack positioned thereon, the at least one disk stack comprising a helically-convoluted chamber; inserting the alignment core tool with the at least one disk stack thereon into the cylindrical stator housing; securing the at least one disk stack to the stator housing; replacing the alignment core tool with an injection core tool, the injection core tool comprising a predetermined stator profile that comprises at least one more lobe than a number of the rotor lobes; injecting an elastomeric material through the at least one bleed hole path to form a tubular elastomeric section adjacent the at least one disk stack; curing the elastomeric material to form a helically convoluted chamber therein that is aligned with the helically-convoluted chamber of the at least one disk stack; and removing the injection core tool. 
         [0014]    Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, and that the invention is not limited to the precise arrangements and instrumentalities shown, since the invention will become apparent to those skilled in the art from this detailed description. 
     
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
         [0015]    The invention will be described in conjunction with the following drawings in which like reference numerals designate like elements and wherein: 
           [0016]      FIG. 1  is a partial, longitudinal cross-sectional view of prior art metal rotor and a rubber lined stator having a rubber or elastomeric stator lining and a metal stator tube; 
           [0017]      FIG. 2  is a transverse cross-sectional view taken along line  2 - 2  of  FIG. 1 ; 
           [0018]      FIG. 3  is a partial, longitudinal cross-sectional view of prior art metal rotor and a metal-on-metal (MOM) stator having a metal stator lining and a metal stator tube; 
           [0019]      FIG. 4  is a transverse cross-sectional view taken along line  4 - 4  of  FIG. 3 ; 
           [0020]      FIG. 5  a partial, longitudinal cross-sectional view of another prior art metal rotor and a rubber lined stator, referred to as an “even wall” power section; 
           [0021]      FIG. 6  is a transverse cross-sectional view taken along line  6 - 6  of  FIG. 5 ; 
           [0022]      FIG. 7  is a partial, longitudinal cross-sectional view of an exemplary hybrid stator of a first embodiment of the present invention; 
           [0023]      FIG. 7A  is a partial, longitudinal cross-sectional view of an exemplary hybrid stator of a first embodiment of the present invention, but using a unitized element for the rigid section; 
           [0024]      FIG. 8  is a transverse cross sectional view of the hybrid stator along line  8 - 8  of  FIG. 7  showing an elastically deformable liner within a stator casing and housing a rotor therein; 
           [0025]      FIG. 9  is a transverse cross-sectional view of the hybrid stator along line  9 - 9  of  FIG. 7  showing a rigid stator section within the stator casing and housing the rotor therein; 
           [0026]      FIG. 10  is a transverse cross-sectional view of the hybrid stator along taken along line  10 - 10  of  FIG. 7  and showing a sleeve within the stator casing and housing a rotor therein; 
           [0027]      FIG. 11  is a partial, longitudinal cross-sectional view of a second embodiment of an exemplary hybrid stator of the present invention; 
           [0028]      FIG. 11A  is a partial, longitudinal cross-sectional view of a second embodiment of an exemplary hybrid stator of the present invention, but using a unitized element for the rigid section; 
           [0029]      FIG. 12  is a transverse cross-sectional view of the hybrid stator along line  12 - 12  of  FIG. 11  showing an elastically deformable liner and rigid disk stack within the stator casing and housing the rotor therein; 
           [0030]      FIG. 13  is an enlarged view of the disk stack of  FIG. 11  showing a saw tooth surface that prevents galling between the rotor and disk stack surfaces during rotor rotation; 
           [0031]      FIG. 14A  depicts a cross-sectional view of the first embodiment, similar to  FIG. 7 , but using a rigid section only on each end of the stator; 
           [0032]      FIG. 14B  depicts a cross-sectional view of the first embodiment, similar to  FIG. 7 , but using a rigid sleeve only on each end of the stator; 
           [0033]      FIG. 14C  depicts a cross-sectional view of the first embodiment, similar to  FIG. 7 , but using a rigid section and a rigid sleeve only on one end (e.g., the distal end) of the stator; 
           [0034]      FIG. 14D  depicts a cross-sectional view of the first embodiment, similar to  FIG. 7 , but using a rigid section only on one end (e.g., the proximal end) of the stator; 
           [0035]      FIG. 14E  depicts a cross-sectional view of the first embodiment, similar to  FIG. 7 , but using a rigid sleeve only on one end (e.g., the distal end) of the stator; 
           [0036]      FIG. 14F  depicts cross-sectional view of the first embodiment, similar to  FIG. 7 , but using a rigid section on one end (e.g., the proximal end) and a rigid sleeve only on the other end (e.g., the distal end) of the stator; 
           [0037]      FIG. 14G  depicts cross-sectional view of the first embodiment, similar to  FIG. 7 , but using a rigid sleeve and a rigid section on one end (e.g., the proximal end) and only a rigid sleeve on the other end (e.g., the distal end) of the stator; 
           [0038]      FIG. 14H  depicts cross-sectional view of the first embodiment, similar to  FIG. 7 , but using a rigid sleeve and a rigid section on one end (e.g., the proximal end) and a rigid section only on the other end (e.g., the distal end) of the stator; 
           [0039]      FIG. 15A  depicts a cross-sectional view of the second embodiment, similar to  FIG. 11 , but using a rigid section only on each end of the stator; 
           [0040]      FIG. 15B  depicts a cross-sectional view of the second embodiment, similar to  FIG. 11 , but using a rigid sleeve only on each end of the stator; 
           [0041]      FIG. 15C  depicts a cross-sectional view of the second embodiment, similar to  FIG. 11 , but using a rigid section and a rigid sleeve only on one end (e.g., the distal end) of the stator; 
           [0042]      FIG. 15D  depicts a cross-sectional view of the second embodiment, similar to  FIG. 11 , but using a rigid section only on one end (e.g., the proximal end) of the stator; 
           [0043]      FIG. 15E  depicts a cross-sectional view of the second embodiment, similar to  FIG. 11 , but using a rigid sleeve only on one end (e.g., the distal end) of the stator; 
           [0044]      FIG. 15F  depicts cross-sectional view of the second embodiment, similar to  FIG. 11 , but using a rigid section on one end (e.g., the proximal end) and a rigid sleeve only on the other end (e.g., the distal end) of the stator; 
           [0045]      FIG. 15G  depicts cross-sectional view of the second embodiment, similar to  FIG. 11 , but using a rigid sleeve and a rigid section on one end (e.g., the proximal end) and a rigid sleeve only on the other end (e.g., the distal end) of the stator; 
           [0046]      FIG. 15H  depicts cross-sectional view of the second embodiment, similar to  FIG. 11 , but using a rigid sleeve and a rigid section on one end (e.g., the proximal end) and a rigid section only on the other end (e.g., the distal end) of the stator; 
           [0047]      FIG. 16A  is a flow diagram illustrating an exemplary method for producing an exemplary hybrid stator in accordance with the broadest configurations of the first embodiment as shown in  FIGS. 13A and 13B ; 
           [0048]      FIG. 16B  is a flow diagram illustrating an exemplary method for producing an exemplary hybrid stator in accordance with the broadest configurations of the second embodiment as shown in  FIGS. 13A and 13B ; 
           [0049]      FIG. 17A  is a flow diagram illustrating an alternative method for forming the tubular elastomer of the broadest configuration of the first embodiment when a rigid disk section having bleed holes is used; and 
           [0050]      FIG. 17B  is a flow diagram illustrating an alternative method for forming the tubular elastomer of the broadest configuration of the second embodiment when a rigid disk section having bleed holes is used. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0051]    The present invention will now be described with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth below. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
         [0052]    Examples of the present invention include a stator for a downhole drilling motor to be used in an oil or gas well, or a utility bore hole. The downhole drilling motor is preferably a hydraulic motor that uses drilling mud flowing through it to create rotary motion that powers a drill bit or other tool. Part of the stator is lined with an elastomer (e.g., rubber, plastic) that fits tightly around a rotor over part of its length. Part of the stator has a profiled rigid section that is shaped like the rubber lined section, but has no rubber. The rigid section part preferably does not fit as tightly around the rotor as the rubber lined part. Part of the stator has a sleeve. The sleeve is sized to allow the rotor to rotate during operation but also to support it. This structure allows the stator to begin a run with a tight seal around the rotor from the rubber lined section, giving the motor high efficiency. Under difficult conditions of load and temperature, the rubber may not last long enough to finish the planned run. This would normally require a time consuming and costly trip out of the well during the run to change the stator. However, a motor with this exemplary stator could continue to operate throughout the run, at reduced efficiency, on the part of the stator that has the profiled metal inside contour plus the profiled metal contour supports the rotor as it orbits thereby reducing the sideload on the rubber section and resulting in longer life of the rubber. 
         [0053]    The current invention includes a manufacturing process for making a hybrid stator for pump and motor applications with internally lined sections of elastomer and a rigid material (e.g., metal) having a lobed internal helical profile which preferably contains one more lobe than the rotor. The internally lined elastomer section is a generally tubular section having elastically deformable elastomeric material defining a first helically convoluted chamber section may be made as well known by a skilled artisan, for example, by conventional molding of rubber articles. This section is generally molded or clamped to the stator casing. The rigid section is preferably made from a laminated stack of thin disks bonded to one another to form the desired stator profile. These disks may be manufactured in a variety of ways, with preferred methods including machining via laser, water jet, electrical discharge machining (EDM), milling etc. or a stamping/punching process. They may also be made to shape originally by casting, powder metallurgy or any similar process. 
         [0054]    While the various components may be constructed of any material suitable for contact with the human body, the preferred materials of the disks includes metal, for example, steel. The disks may be assembled into a helix by stacking the disks about a mandrel or jig that interacts with lobed features of the disks. The disks may be made in such a way that openings following the helix of the stator for passage of controls, sensors, fluid etc. are created down the length of the stator. The disks may then be bonded to one another to form the disk stack. The disk stack and elastomer section(s) may then be inserted into the stator tube casing, where they are bonded or mechanically fixed to the casing. The rigid or metal section(s) preferably does not fit as tightly around the rotor as the rubber lined section. 
         [0055]    The elastomer section (see  FIGS. 11-12 and 15A-15H  below) may also include a rigid disk stack and an elastomer liner. In this example, the disks in that configuration, when combined, results in the disk stack but not as thick radially as the disk stack formed in the rigid section  30  (again, see  FIG. 11 ). The disks of the elastomer section are smaller in radial width or extension than the disk of the rigid section to allow a generally uniform space for the elastomer lining of the elastomer section, which is typically applied by injection molding. 
         [0056]    The present invention also addresses a further deficiency of existing hydraulic motors. A conventional power section when incorporated into a drilling motor is connected to the bearing assembly of the motor using a constant velocity (CV) joint or flex shaft. During operation these connection devices impart a sideload to the rotor that is reacted out by the rubber in the stator. The sideload can be severe enough that it deforms the rubber sufficiently to fatigue it, thereby resulting in short life. For example, as discussed earlier,  FIGS. 1-2  depict a prior art metal rotor and a rubber-lined stator having a rubber or elastomeric stator lining and a metal stator tube;  FIGS. 3-4  depict a prior art metal rotor and a metal on metal stator having a metal stator lining and a metal stator tube and  FIGS. 5-6  depict a prior art combination of these two with a rubber portion of even thickness on the inner surface of the metal stator lining. These prior art devices suffer from, among other things, this sideloading. In contrast, the invention of the present application overcomes the problem by incorporating a rigid (metal or plastic) section  24  (e.g., a plurality of disks  32 ) to react to the rotor  14  sideload while still allowing the rotor  14  to orbit correctly. Additionally, a circular rigid sleeve  40  is incorporated to also help react the sideload of the rotor while it is orbiting; this rigid sleeve  40  is preferably a metallic material but it may also comprise plastic. 
         [0057]      FIG. 7  depicts an exemplary first embodiment of a hydraulic motor or pump  10  that has its principal use as a drilling motor for downhole oil well or slurry applications. The motor  10  is shown partially cut away showing a drill bit or similar power device  12  attached (at a distal or working end DE of the stator  16 ) to an elongated helically lobed rotor  14  extended through a hybrid stator  16 . The stator  16  is also a helically lobed structure preferably having at least one more lobe than the rotor, which creates gaps  18  between the rotor  14  and the stator along the longitudinal length therebetween. These gaps  18  progressively move along the length between the rotor  14  and stator  16  as the rotor rotates within the stator, and progressively move fluid in the gaps from one end of the rotor to the other end with the rotation, as is well understood by a skilled artisan. 
         [0058]    The stator  16  includes at least one tubular elastomer stator section  22  and at least one rigid stator section  24  housed within a cylindrical outer housing or stator casing  26  and at least one sleeve  40  within the casing  26 . By way of example only,  FIG. 7  shows all three components present, with a rigid stator station  24  and a sleeve  40  on both sides of the tubular elastomer stator section  22 . The stator  16  defines a helically convoluted chamber  20  about the rotor  14 . The elastomer stator section  22  includes an elastically deformable liner  28  conventionally made of an elastomeric material. While not being limited to a particular theory, the liner  28  is shown in  FIG. 1  as extended between the chamber  20  and the stator casing  26 . As can be seen in  FIG. 7 , the elastically deformable liner  28  is bonded to the stator casing  26 , and each rigid stator section  24  is bonded to both the elastically deformable liner and the stator casing. The function of the sleeve  40  is to provide added support of the rotor  14  during operation. The sleeve  40  forms a cylindrical chamber section or passageway PW and is sized so that during operation, the rotor orbit touches the inner diameter of the sleeve  40  and is thereby supported. The rigid sleeve  40  is bonded by for example, welding, fusing, soldering, brazing, sintering, diffusion bonding, mechanical fastening, or via an adhesive bond to the inside surface of the stator casing  26 . 
         [0059]      FIG. 8  depicts the hybrid stator  16  in traverse cross section, showing the elastically deformable liner  28  defining a first helically convoluted chamber section  25  within the stator casing  26  and housing the rotor  14  therein.  FIG. 9  depicts the hybrid stator  16  in traverse cross section, showing the rigid stator section  24  within the stator casing  26  and housing the rotor  14  therein. 
         [0060]    The rigid stator section  24  may be a single unit molded into a helical configuration. The single unit is preferably a disk stack  30  having a plurality of like-shaped lobed disks  32 . The disks  32  in the disk stack  30  preferably share a common centerline with each disk rotated slightly from the disks on either side to form a helical winding profile as a second helically convoluted chamber section  34  inside the disk stack. The disks  32  may be placed into a helical configuration of the disk stack  30  by stacking the disks onto an alignment assembly that includes an alignment mandrel/core with a profile that catches lobes  38  of the disks with its profile cut in a helical pattern in the alignment core, as readily understood by a skilled artisan. The disks  32  may also be aligned with an alignment assembly including a jig which interacts with disk features other than the inner profile or through features built into the disks (e.g., apertures through the disk lobes) that rotate each disk slightly relative to neighboring disks. 
         [0061]    In some cases it is then necessary to tighten the alignment of the disk stack  30  by the application of force to the outer diameter of the stack by, for example, swaging, v-blocking or hammering in either a static or rotating condition. The disk stack  30  is set by fixing the rigid disks  32  together with a bond provided by, for example, welding, fusing, soldering, brazing, sintering, diffusion bonding, mechanical fastening, or via an adhesive bond. The stator casing  26 , which preferably is made of metal, may be straightened, chamfered, machined, cleaned and heated as required and understood by a skilled artisan. The stator casing is another bonding member that may then be slid over the disk stack and bonded together (e.g., welding, fusing, soldering, brazing, sintering, diffusion bonding, mechanical fastening, adhesive) to further fix the rigid disk together. The alignment assembly may then be removed from the disk stack  30 . It should be noted that depending on the disk stack alignment methodology, it may be required or preferred to insert the disk stack  30  into the stator casing  26  without the alignment tooling entering the outer housing as well. 
         [0062]    As can best be seen in  FIG. 9 , each disk  32  includes a convoluted cavity  34  with the exemplary disk having a number of equally spaced symmetrical lobes  38  radially extending toward the centerline. Preferably all of the disks have substantially identical construction and dimension. In the exemplary embodiments the disk stack  30  provides the final profile geometry of the stator  16  along the rigid stator section  24 . 
         [0063]      FIG. 10  depicts, among other things, a cross-section of the rigid sleeve  40  which may comprise a metallic material. 
         [0064]      FIGS. 11 and 12  depict a second exemplary embodiment of a hydraulic motor or pump  50  similar to the motor  10  discussed above. The motor  50  also includes a hybrid stator  52  similar to the hybrid stator  16 . By way of example only,  FIGS. 11-12  show all three components present, namely, the hybrid stator  52  includes at least one tubular elastomer stator section  54  and at least one rigid stator section  24  housed within a cylindrical outer housing or stator casing  26  and the sleeve  40 . However, in this embodiment, the elastomer section  54  includes an elastically deformable liner  56  conventionally made of an elastomeric material and defines the first helically convoluted chamber section  25  about the rotor  14 . The elastomer section  54  also includes a supportive section  58  that is bonded to the elastically deformable liner  56  and the stator casing, and is preferably rigid to provide greater support to the hybrid stator  52  against the rotating rotor  14 . Subsequent reference in the Specification and Figures to the elastomer section  54  implies the inclusion of the deformable liner  56  and supportive section  58 . As can be seen in  FIG. 11 , the elastically deformable liner  56  and the supportive section  58  are also bonded to each adjacent rigid stator section  24 . The rigid sleeve  40  is similar to the sleeve discussed previously in the first embodiment. As with the first embodiment, it should be understood that it is within the broadest scope of the present invention to have the hybrid stator  52  include at least one tubular elastomer section  54  and at least either the one rigid stator section  24  or the one rigid sleeve  40 . 
         [0065]    While not being limited to a particular theory, the supportive section  58  is molded into a helical configuration. Similar to the rigid stator section  24 , the supportive section  58  may include a disk stack  60  similar to the disk stack  30  as having a plurality of like-shaped lobed disks  62 . The disks  62  in the disk stack  60  share a common centerline with each disk rotated slightly from the disks on either side to form a helical winding profile inside the disk stack. As can best be seen in  FIG. 12 , each disk  62  defines a convoluted cavity  64  larger than the convoluted cavity  34  defined by the disks  32 . This results in a disk stack  60  with a helically convoluted chamber section  66  preferably broader than the second helically convoluted chamber section  34 . The elastically deformable liner  56  is bonded to the disk stack  60  to form the first helically convoluted chamber section  25 . 
         [0066]      FIG. 13  depicts an enlarged view of the inner surface of the disk stack  30  of the rigid stator section  24 . As can be seen, the inner surface forms a “saw-tooth surface” that creates a “tortuous path” for fluid flow (also referred to as a “labyrinth seal”) between the rotor  14  and disk stack  30  confronting surfaces. This configuration also prevents galling (a form of wear based on adhesion of sliding surfaces) that would normally occur between the rotor  14  and disk stack  30  surfaces. It should be further understood that this saw-tooth surface configuration is applicable to the disk stack  30  surfaces used in the first embodiment ( FIGS. 7-10, 14A-14H ) and the second embodiment ( FIGS. 11-13, 15A-15H ) that supports a labyrinth seal for that embodiment also. 
         [0067]    Although  FIGS. 7 and 11  depict the sequence of the rigid sleeve (RS)  40 , the rigid section  30  and the tubular elastomer (TE)  22 / 54  as one moves inward either from the proximal PE or distal end DE of the hybrid stator  16 , it should be understood that it is within the broadest scope of the present invention to include various combinations and/or arrangements of these three components within the stator casing  26 . As a result, the following configurations of the hybrid stator  16 / 52  are covered by the present invention. 
       Section Combinations in the First Embodiment 
       [0068]    In addition to the arrangement of the different sections shown in  FIG. 7 , the following combinations are within the broadest scope of the present invention: 
         [0069]      FIG. 14A  depicts a cross-sectional view of the first embodiment but using a rigid section only on each end of the stator; or 
         [0070]      FIG. 14B  depicts a cross-sectional view of the first embodiment but using a rigid sleeve only on each end of the stator; or 
         [0071]      FIG. 14C  depicts a cross-sectional view of the first embodiment but using a rigid section and a rigid sleeve only on one end (e.g., only on the distal end or only on the proximal end) of the stator; or 
         [0072]      FIG. 14D  depicts a cross-sectional view of the first embodiment but using a rigid section only on one end (e.g., only on the proximal end or only on the distal end) of the stator; or 
         [0073]      FIG. 14E  depicts a cross-sectional view of the first embodiment but using a rigid sleeve only on one end (e.g., only on the distal end or only on the proximal end) of the stator; or 
         [0074]      FIG. 14F  depicts cross-sectional view of the first embodiment but using a rigid section on one end (e.g., the proximal end) and a rigid sleeve only on the other end (e.g., the distal end) of the stator, or reversing these end locations; or 
         [0075]      FIG. 14G  depicts cross-sectional view of the first embodiment but using a rigid sleeve and a rigid section on one end (e.g., the proximal end) and a rigid sleeve only on the other end (e.g., the distal end) of the stator, or reversing these end locations; or 
         [0076]      FIG. 14H  depicts cross-sectional view of the first embodiment but using a rigid sleeve and a rigid section on one end (e.g., the proximal end) and a rigid section only on the other end (e.g., the distal end) of the stator, or reversing these end locations. 
       Section Combinations in the Second Embodiment 
       [0077]    In addition to the arrangement of the different sections shown in  FIG. 11 , the following combinations are within the broadest scope of the present invention: 
         [0078]      FIG. 15A  depicts a cross-sectional view of the second embodiment but using a rigid section only on each end of the stator; or 
         [0079]      FIG. 15B  depicts a cross-sectional view of the second embodiment but using a rigid sleeve only on each end of the stator; or 
         [0080]      FIG. 15C  depicts a cross-sectional view of the second embodiment but using a rigid section and a rigid sleeve only on one end (e.g., only on the distal end or only on the proximal end) of the stator; or 
         [0081]      FIG. 15D  depicts a cross-sectional view of the second embodiment but using a rigid section only on one end (e.g., only on the proximal end or only on the distal end) of the stator; or 
         [0082]      FIG. 15E  depicts a cross-sectional view of the second embodiment but using a rigid sleeve only on one end (e.g., only on the distal end or only on the proximal end) of the stator; or 
         [0083]      FIG. 15F  depicts cross-sectional view of the second embodiment but using a rigid section on one end (e.g., the proximal end) and a rigid sleeve only on the other end (e.g., the distal end) of the stator, or reversing these end locations; or 
         [0084]      FIG. 15G  depicts cross-sectional view of the second embodiment but using a rigid sleeve and a rigid section on one end (e.g., the proximal end) and a rigid sleeve only on the other end (e.g., the distal end) of the stator, or reversing these end locations; or 
         [0085]      FIG. 15H  depicts cross-sectional view of the second embodiment but using a rigid sleeve and a rigid section on one end (e.g., the proximal end) and a rigid section only on the other end (e.g., the distal end) of the stator, or reversing these end locations. 
         [0086]      FIG. 16A  provides a flow diagram of an exemplary method for forming one of the broadest configurations ( FIGS. 14D and 14E ) of the first embodiment. In particular, the steps  110 - 170  depicted on the left hand side of  FIG. 16A  set forth the method of forming the first embodiment with at least one rigid disk stack  24  whereas the steps  110  - 170  depicted on the right hand side of  FIG. 16A  set forth the method of forming the first embodiment using at least one rigid sleeve  40 .  FIG. 16B  provides a flow diagram of an exemplary method for forming one of the broadest configurations ( FIGS. 15D and 15E ) of the second embodiment. In particular, the steps  210 - 280  depicted on the left hand side of  FIG. 16B  set forth the method of forming the second embodiment with at least one rigid disk stack  24  whereas the steps  210 - 280  depicted on the right hand side of  FIG. 16B  set forth the method of forming the second embodiment using at least one rigid sleeve  40 . It should be noted that the bleed holes BH depicted in  FIGS. 7 and 11  provide an alternative method for forming the tubular elastomer sections  22  and  54  respectively and that alternative method is discussed with regard to  FIGS. 17A-17B . 
         [0087]    As shown in  FIG. 16A , at step  110  an alignment core (not shown), which provides proper disk alignment (e.g., a tool having a circular helix shaped alignment) where a rigid disk stack  30  is used. At step  120 A Individual disks are placed on the alignment core to form the rigid stack section  30  at the proper location along the alignment core and then this disk stack  30  is secured together (e.g., an outer weld, etc.) thereby forming a helically convoluted chamber through the disk stack  30 . This disk stack  30  comprises a plurality of rigid disks in aligned face-to-face stacked relationship with one another, with each disk rotated with respect to the next adjacent disks progressively along the length of the aligned disks in one direction of rotation to define a helically convoluted chamber section. The disks may be placed in compression with compression springs to keep the disk stack tight. Then, the disk stack may be bonded together, for example, by running weld beads down the length of the disk stack or by brazing the stack together. At step  130 A, the alignment core tool with the disk stack is positioned inside the stator casing  26  at the proper location and the disk stack  30  is secured to the stator casing  26 . At step  140 A, the alignment core tool is removed and replaced with an injection core tool (not shown) wherein the injection core tool has a proper stator profile. The phrase “proper stator profile” means that the tool forms a stator volume that includes one more lobe than the number of rotor lobes in order to permit proper rotation of the rotor  14  within the stator  16 , as discussed earlier. At step  150 A, the elastomeric material is injected through the stator casing  26  adjacent the disk stack  30  to form the tubular elastomeric section  22 . At step  160 A, the elastomeric material is cured to form its own helically convoluted chamber that is aligned with the helically convoluted chamber in the disk stack  30 . The disk stack  30  and tubular elastomeric section  22  are secured together and at step  170  the injector core tool is removed. Alternatively, instead of inserting a rigid disk section  30 , the operator can insert a rigid sleeve  40  in accordance with steps  120 B- 160 B. In particular, at step  120 B, a rigid sleeve  40  is applied to the alignment core at the proper position along the alignment core. At step  130 B, the alignment core with the rigid sleeve  40  is positioned inside the stator casing  26  at the proper location and it is secured to the stator casing  26 . At step  140 B, the alignment core tool is removed and replaced with the injection core tool described previously. At step  150 B, the elastomeric material is injected through the stator casing  26  adjacent the rigid sleeve  40  to form the tubular elastomeric section  22 . At step  160 B, the elastomeric material is cured to form its own helically convoluted chamber that is aligned with a cylindrical chamber in the rigid sleeve  40 . The rigid sleeve  40  and tubular elastomeric section  22  are secured together and at step  170  the injector core tool is removed. 
         [0088]    It should be understood that to form the embodiments shown in  FIGS. 14A-14C, 14F-14H  and that shown in  FIG. 7 , the additional stator components (e.g., the second rigid disk stack  30 , the second sleeve  40 , and/or the sequence of the rigid disk stack  30  followed by the rigid sleeve  40 , etc.) can be placed on the alignment core tool at the proper position when the alignment core tool is inserted into the stator casing  26 . Another alternative to placing all of these components on the alignment core tool first, is to place the appropriate components on the alignment core tool, insert them in one end of the stator casing  26 , form the tubular elastomeric section as described and then insert the alignment core tool with the appropriate stator components (e.g., the second rigid disk stack  30 , the second sleeve  40 , and/or the sequence of the rigid disk stack  30  followed by the rigid sleeve  40 , etc.) through the other end of the stator casing  26  and secure those to the stator casing  26  and to each other. 
         [0089]    As shown in  FIG. 16B , steps for forming the broadest configurations ( FIGS. 15D and 15E ) using the second embodiment is shown. At step  210 , a first disk stack is assembled and secured together at its proper location on the alignment core to form the supportive section  58 . If the rigid disk stack  30  is to be used, then at step  220 A the rigid disk stack  30  is assembled and secured together on the alignment tool. At step  230 A, the first disk stack and the rigid disk stack  30  are secured together. At step  240 A, the alignment tool with the two disk stacks is positioned within the stator casing  26  at the proper location and the disk stacks are secured to the stator casing  26 . At step  250 A, the alignment core tool is removed and replaced with the injection core tool having the proper stator profile, as discussed previously. At step  260 A, the elastomeric material is injected through the stator casing  26  to form the tubular elastomeric section  54  against within the supportive section  58 . At step  270 A, the elastomeric material is cured to form a helically convoluted chamber that matches the helically convoluted chamber in the disk stack  30 . In addition, the elastomeric material and the supportive sleeve  58  are bonded, most likely via heat and/or adhesive. At step  280 , the injection core tool is removed. Alternatively, instead of inserting a rigid disk section  30 , the operator can insert a rigid sleeve  40  in accordance with steps  220 B- 270 B. In particular, at step  220 B, a rigid sleeve  40  is applied to the alignment core at the proper position along the alignment core adjacent the first disk stack. At step  230 B, first disk stack and the rigid sleeve are secured together. At step  240 B, the alignment core with the first disk stack and rigid sleeve  40  is positioned inside the stator casing  26  at the proper location and they are secured to the stator casing  26 . At step  250 B, the alignment core tool is removed and replaced with the injection core tool described previously. At step  260 B, the elastomeric material is injected through the stator casing  26  adjacent the rigid sleeve  40  to form the tubular elastomeric section  54 . At step  270 B, the elastomeric material is cured having a helically convoluted chamber that is aligned with a cylindrical chamber section of the rigid sleeve  40 . As mentioned with regard to step  270 A, the elastomeric material and the supportive section  58  are bonded, most likely via heat and/or adhesive. 
         [0090]    As mentioned earlier, it should be understood that to form the embodiments shown in  FIGS. 15A-15C, 15F-15H  and that shown in  FIG. 11 , the additional stator components (e.g., the second rigid disk stack  30 , the second sleeve  40 , and/or the sequence of the rigid disk stack  30  followed by the rigid sleeve  40 , etc.) can be placed on the alignment core tool at the proper position when the alignment core tool is inserted into the stator casing  26 . Another alternative to placing all of these components on the alignment core tool first, is to place the appropriate components on the alignment core tool, insert them in one end of the stator casing  26 , form the tubular elastomeric section as described and then insert the alignment core tool with the appropriate stator components (e.g., the second rigid disk stack  30 , the second sleeve  40 , and/or the sequence of the rigid disk stack  30  followed by the rigid sleeve  40 , etc.) through the other end of the stator casing  26  and secure those to the stator casing  26  and to each other. 
         [0091]    As mentioned earlier, bleed holes BH can be used in the rigid disk stack  30  to provide an alternative method of forming the tubular elastomer  22  or  54 .  FIG. 17A  depicts the process of forming the tubular elastomer  22  of the first embodiment. In particular, at step  310 A, the alignment core tool is provided. At step  320 A, the individual disks that form the disk stack  30  comprise respective cutouts or apertures such that when the plurality of disks are placed on the alignment core tool, a disk stack  30  is formed into the rigid disk section  30  which also comprises “bleed hole paths” therethrough. At step  330 A, the assembled disk stack  30  with the bleed hole paths are secured together to form the rigid disk stack  30  section having a helically convoluted chamber as well as the bleed hole paths. At step  340 A, the alignment core tool with the disk stack  30  is positioned inside the stator casing  26  at the proper location and the disk stack  30  is secured to the stator casing  26 . At step  350 A, the alignment core tool is removed and replaced with an injection core tool having the proper stator profile as discussed previously. At step  360 A, the elastomeric material is injected through the bleed holes in the rigid disk stack  30  to form the tubular elastomeric section  22 . At step  370 A, the elastomeric material is cured to form its own helically convoluted chamber that is aligned with the helically convoluted chamber in the disk stack  30 . The disk stack  30  and tubular elastomeric section  22  are secured together and at step  370 A and at step  380 A the injector core tool is removed. The other configurations where the rigid disk section  30  is used ( FIGS. 7, 14A, 14C-14D and 14F-14H ) can be formed in accordance with the processes described previously. 
         [0092]    If the tubular elastomer  54  of the second embodiment is to be formed using bleed holes BH in the rigid disk section  30 , then the process in  FIG. 17B  is followed. In particular, at step  410 A, a first disk stack is assembled and secured together at its proper location on the alignment core to form the supportive section  58 . At step  420 A, the individual disks that form the disk stack  30  (also referred to as the “second disk stack”) and which comprise respective cutouts or apertures such that when the plurality of disks are placed on the alignment core tool, a disk stack  30  is formed into the rigid disk section  30  which also comprises “bleed hole paths” therethrough. At step  430 A, the second disk stack is secured together on the alignment tool at its proper position. At step  440 A, the first disk stack and the second disk stack  30  are secured together. At step  450 A, the alignment core tool with the two disk stacks secured together is inserted within the stator casing  26  and they are secured to the stator casing. At step  460 A, the alignment core tool is removed and the injection core tool having the proper stator profile is inserted. At step  470 A, the elastomeric material is injected through bleed holes BH in the rigid disk stack  30  to form the tubular elastomeric section  54 . At step  480 A, the elastomeric material is cured to form its own helically convoluted chamber that is aligned with the helically convoluted chamber in the disk stack  30 . As mentioned with regard to step  270 A, the elastomeric material and the supportive section  58  are bonded, most likely via heat and/or adhesive. The disk stack  30  and tubular elastomeric section  54  are secured together and at step  480 A and at step  490 A the injector core tool is removed. The other configurations where the rigid disk section  30  is used ( FIGS. 11, 15A, 15C-15D and 15F-15H ) can be formed in accordance with the processes described previously. 
         [0093]    It is also within the broadest scope of the present invention to include alternative means of injecting the rubber into the stator  16 / 52  that does not require the use of bleed holes BH in the disk stack  30 . 
         [0094]    In all of the embodiments of the present invention described above, the following should be noted that the way in which the rotor  14  rotates within the stator  26  is known as “nutation” or “nutative communication.” In particular, due to the geometry of the rotor  14  and stator  26 , the rotor  14  does not rotate about the axis of the pump but rather rotates in one direction about its own axis while orbiting in the opposite direction around an orbital path defined due to the helix geometry. 
         [0095]    As mentioned previously, the rigid section  24  in both the first and second embodiments is accomplished by the use of a stack  30  of a plurality of thin disks  32  with an internally shaped inside diameter. However, this is by way of example only. The rigid section  24  may also comprise a unitized element  24 A as shown in  FIG. 7A  in the first embodiment and in  FIG. 11A  in the second embodiment, rather than the disk stack  30 . This unitized element  24 A comprises the proper shape formed by the disk stack  30  for positioning in the stator casing  26 , including the helically-convoluted chamber, as well as any bleed holes BH paths discussed previously. Thus, the phrase “disk stack” as used in the Specification and Claims also covers any unitized element  24 A having the requisite shape and helically-convoluted chamber. It also includes any unitized element  24 A having the requisite shape, with the helically-convoluted chamber and with at least one bleed hole BH path. Furthermore, the term “disk stack” covers various materials other than just metal that the unitized element may comprise. Even the supportive section  58  in the second embodiment may be formed as a unitized element (see  FIG. 11A ). 
         [0096]    Exemplary processes for forming the unitized element  24 A include:
       (a) start with a solid bar and electro-chemically machine (ECM) the internal profile along the length of the bar; the resulting rigid section tube is a single one piece section;   (b) start with a solid bar and internally mill the internal profile along the length of the bar; the resulting rigid section is a single one piece section;   (c) cast the rigid section; the resulting rigid section is a single one piece section.       
 
         [0100]    While the invention has been described in detail and with reference to specific examples thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof. Without further elaboration, the foregoing will so fully illustrate the invention that others may, by applying current or future knowledge; readily adapt the same for use under various conditions of service.