Abstract:
A progressing cavity pump has a rotor that moves in an eccentric motion, and is driven by a drive shaft that rotates about a fixed axis. Various means have been used to connect the two; mostly using an intermediate shaft called a connecting rod that has a universal joint at either end. This device replaces that with two parallel plates; one with several pins protruding from it, and the other with the same number of holes in it. The holes are sized to allow the eccentric motion of the rotor. There is also a ball between the two plates to transmit loads between the plates.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of Invention 
         [0002]    This invention relates to generally to progressive cavity or positive displacement pumps or motors, and more particularly, to drive arrangements for progressive cavity pumps or motors which have coupling mechanisms. 
         [0003]    2. Description of Related Art 
         [0004]    The use of progressive cavity, helical or single-screw rotary devices is well-known in the art, both as pumps and as driving motors. These devices typically include a rotor of helical contour that rotates within a matching stator. The rotor generally has a plurality of lobes or helices, and the stator has matching lobes. Generally, the rotor has one less lobe than the stator to facilitate pumping rotation. The lobes of the rotor and stator engage to form sealing surfaces and cavities therebetween. For a motor, fluid is pumped into the input end cavity at a higher pressure than that at the outlet end, which creates forces that cause the rotor to rotate within the stator. In the case of a helical gear pump, an external power source turns the rotors to draw fluid in the cavities and facilitate pumping of the fluid. 
         [0005]    In progressive cavity pumps, the pump rotor centerline is eccentrically disposed relative to the centerline of the stator, typically by one unit of eccentricity. In operation, the rotor is rotated about its own centerline within the stator. As the rotor rotates, it also orbits about the centerline of the stator. If the rotor rotation is clockwise, then its orbital motion within the stator is in a counterclockwise direction, and vice versa. The ratio of orbital rotation to axial rotation depends on the number of lobes or helices in the rotor and stator. 
         [0006]    With the rotor centerline being eccentric relative to the stator centerline, and the rotor rotating with axial and orbital rotation movement at the same time, the rotor rotates in a nutating motion relative to the stator and pump/motor housing. However, because of this nutating motion of the rotor, the rotor cannot be directly actuated by an external drive shaft. This problem resulted primarily from the failure to provide a drive train capable of handling the helix rotor driving motion in a durable, reliable and inexpensive manner. Both in the case of a motor, where fluid against the rotor provides the driving action, and also a pump, where the rotor is driven, a drive coupling mechanism, or coupling, is required to transform a rotation about a fixed axis to a rotation about an orbiting axis. 
         [0007]    Various drive arrangements for cavity pumps have been devised to accommodate the nutating motion of the rotor. One common drive arrangement employs universal joint to provide power between the drive/driven shaft and the rotor. Another approach uses a flexible shaft instead of universal joints. 
         [0008]    Still, a long term problem continues in providing an improvement in the operation and durability of couplings between the drive/driven shaft and the rotor of progressive cavity pumps and motors. The inventors have contemplated and solved this problem by inventing a drive coupling mechanism (e.g., coupler) including two spaced apart parallel plates with a driving arrangement between the plates that is inexpensive to produce and is durable and reliable in operation as will be described in greater detail below. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    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 the central feature of the claimed subject matter, nor is it intended for use in determining the scope of the claimed subject matter. 
         [0010]    In accordance with an example of the invention, a drive coupling mechanism or coupling includes a first plate, a second plate, and a pin. The first plate is purposefully designed to be coupled to a shaft having a fixed axis. The second plate is eccentrically disposed adjacent to and spatially separate from the first plate. The second plate is purposefully designed to attach to a rotor having an orbiting axis, wherein a rotation of the rotor produces a circular path of the orbiting axis with a diameter of eccentricity. One of the first and second plates include a first cylindrical bore wall defining a first bore extending longitudinally toward the other one of the first and second plates. The pin is a first pin having a first end attached to the other one of the first and second plates, with the pin extending into the first bore and abutting the first cylindrical bore wall. The pin has a pin diameter less than the diameter of the bore. Preferably, the bore diameter is at least equal to the pin diameter plus the diameter of eccentricity of the orbiting axis of the rotor to allow rotation of the rotor and the shaft via the drive coupling mechanism. The drive coupling mechanism may further include a spacer between the first and second plates to keep the plates spatially separate. 
         [0011]    Preferably, the spacer is a bearing or thrust bearing that may be contained to some degree in a recess of one of the plates. The drive coupling mechanism may also include a third plate, which may also be referred to as a securing plate. For an embodiment having the first pin attached to the first plate, the securing plate is preferably adjacent the second plate opposite the first plate with the first pin extending through the first bore in the second plate and attaching to the securing plate. It is understood that in addition to the first pin and first bore, the drive coupling mechanism may include additional pins and bores connecting the plates as described above with the first pin and first bore. 
         [0012]    In accordance with another example of the invention, the drive coupling mechanism discussed above is part of a progressive cavity device that includes a stator and a rotor. In this example of a progressive cavity device, the stator defines a helically convoluted elongated chamber. The rotor is within the stator and includes a helically shaped shaft and a plurality of lobes with a profile that compliments the helically convoluted elongated chamber of the stator. 
         [0013]    It is understood that one of the plates may be a drive plate attached to a drive shaft, which may also be used as a driven shaft or drill shaft. The other plate may be a rotor plate attached to a rotor shaft. During operation of the coupling in a progressive cavity device such as a pump, pressure at the outlet of the pump causes a net axial force on a rotor that pushes it toward the drive shaft. When the rotor is pushed toward the drive shaft, it pushes the spacer against the drive plate, where the thrust load is carried onto the spacer supporting the drive shaft. The spacer, which may be a thrust bearing, is free to roll around inside a bearing recess in one of the plates and a mating recess in the other plate opposite the bearing recess to allow parallel movement between the two plates. 
         [0014]    In accordance with yet another example of the invention, a method for coupling a shaft having a fixed axis to a rotor having an orbiting axis, wherein a rotation of the rotor produces a circular path of the orbiting axis with a diameter of eccentricity is described. The method for coupling includes attaching a first pin to a first plate, with the first pin extending perpendicularly from the first plate, with the first pin having a pin diameter, a first end and a second end opposite the first end, with the first end being attached to the first plate, placing a second plate adjacent to and spatially separate from the first plate, with the second plate having a first cylindrical bore wall defining a first bore that extends longitudinally toward the first plate, the first bore having a bore diameter that is at least equal to the pin diameter plus the diameter of eccentricity of the orbiting axis, depositing the first pin into the first bore and abutting the first cylindrical bore wall of the second plate while maintaining spatial separation between the first plate and the second plate, fixedly securing one of the first plate and the second plate to the shaft having the fixed axis, and fixedly securing the other one of the first plate and the second plate to the rotor having the orbital axis, the shaft and the rotor being coupled via a drive coupling mechanism including the first plate, the second plate and the first pin to allow rotation of the rotor and the shaft via the drive coupling mechanism. 
         [0015]    Further scope of applicability of the present invention will be apparent from the detailed description given hereafter. However, it should be understood that any examples described herein, 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 the detailed description. 
         [0016]    All references cited herein are incorporated herein by reference in their entireties. 
     
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
         [0017]    The invention will be described in conjunction with the following drawings in which like reference numerals designate like elements and wherein: 
           [0018]      FIG. 1  is a side view, partially in section, of an exemplary drive coupling mechanism or coupler in accordance with the invention; 
           [0019]      FIG. 2  illustrates the coupler of  FIG. 1  in perspective view; 
           [0020]      FIG. 3  is a side perspective view of another example of a coupler in accordance with the invention; 
           [0021]      FIG. 4  illustrates the coupler of  FIG. 3  taken along line  4 - 4  thereof; 
           [0022]      FIG. 5  is a side view of the coupler of  FIG. 3  attached to an exemplary rotor and drive shaft; and 
           [0023]      FIG. 6  illustrates the coupler depicted in  FIG. 5 , including the coupler, within a progressive cavity pump. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    The present invention will now be described with reference to examples provided in the accompanying drawings, in which preferred embodiments and examples 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. 
         [0025]      FIG. 1  depicts an exemplary embodiment of a drive coupling mechanism or coupler  10 , partially in section, to better shown structural features of the coupler. In particular,  FIG. 1  shows the coupler  10  having a drive plate  12 , a rotor plate  14 , pins  16  and a spacer (e.g., bearing  18 ). The drive plate  12  and rotor plate  14  are purposefully designed in parallel and separated by a small gap. The drive plate  12  is attached to an axially rotative drive shaft  20  and the rotor plate  14  is shown attached to an orbitally rotative rotor shaft  22  having a centerline eccentrically disposed (e.g., a diameter of eccentricity D e ) relative to the drive shaft. It is understood that the plates may be attached to their respective drive shaft  20  and rotor shaft  22  directly or indirectly, with central members, such as shafts or couplings therebetween. In this example, it is understood that the drive plate  12  is fixedly secured, directly or indirectly with the drive shaft  20 . Likewise, it is understood that the rotor plate  14  is fixedly attached, directly or indirectly with the rotor shaft  22 . 
         [0026]    At least one of the pins  16  is attached to a first plate, which is illustrated as the drive plate  12  but may be either the drive plate or the rotor plate  14 . The pins  16  are preferably cylindrical and have a first end attached inside apertures  24  of the drive plate  12  such that the pins extend from the drive plate towards and into the rotor plate  14 . Each pin  16  has a diameter slightly smaller than and preferably about the same size as the respective drive plate aperture  24  for each pin. 
         [0027]    Still referring to the example of  FIG. 1 , the pins  16 , preferably made of steel, metal or like material for strength, longevity and rigidity, are attached to the drive plate  12 , preferably with the pin  16  bonded into apertures  24  within the drive plate  12 . While not being limited to a particular theory, the apertures  24  fixedly receive the pins  16  and hold the pins in place during operation of the coupler  10 . It should be noted that the pins  16  preferably are longitudinally fixed within in the apertures  24  of the drive plate. The pins  16  may also be fixed rotationally in the apertures  24 . However, it is understood that the invention is not so limiting, as the pins  16  may rotate within the drive plate apertures  24  if desired, for example via a busing or bearings between the pins  16  and the apertures. 
         [0028]    The rotor plate  14  includes a plurality of cylindrical bore walls  26 , each defining a bore  28  extending longitudinally toward the drive plate  12 . The bore walls  26  and associated bores  28  are spaced apart around the rotor plate  14  so that each bore may receive one of the pins  16  within its bore walls. Each bore  28  is significantly wider than the respective pin  16  housed within its associated bore wall  26 . Preferably, each bore  28  has a bore diameter that is equal to or greater than the diameter of the respective pin  16  within the bore plus the diameter of eccentricity D e  of the orbiting axis to allow rotation of the rotor shaft  22  and the drive shaft  20  via the coupler  10 , with the rotor and drive shafts preferably maintaining a parallel relationship during rotation. The diameter of eccentricity D e  is also understood to be the diameter of the circular path traced by the axis of the rotor shaft  22  during a rotation of the rotor. During a rotation of the drive shaft  20 , contact between the pins  16  and the bore walls  26  drives the rotor plate  14 , and by association, the rotor shaft  22 , while the bores larger diameter relative to the pins  16  allows for the eccentric or gyrational rotation of the rotor shaft and nutating movement of an attached rotor. 
         [0029]    The pins  16  enter bores  28  of the second plate, which in the example is the rotor plate  14 . In particular, the drive and rotor plates  12 ,  14  are aligned so that each pin  16  extends through a mating bore  28  of the second plate and extends at least partially through the bore. As discussed above, each of the mating bores  28  preferably has a diameter at least equal to the diameter of the pin  16  plus the diameter of eccentricity D E  of the orbiting axis of the rotor. During operating, the pins  16  abut the cylindrical bore walls  26  of the second plate to rotate the second plate upon rotation of the first plate. It is understood that in another example, the plates may be reversed, with the drive plate  12  having the bore walls  26  and bores  28 , and the rotor plate  14  holding the pins  16  that extend through bores of the drive plate. In this operation, rotation of the drive plate  12  with the bores drive the pins  16  causing rotation of the attached rotor plate. 
         [0030]    During operation of the coupler  10 , for example within a pump, pressure at the outlet of the pump creates an axial force on the rotor that pushes the rotor shaft  22  toward the drive shaft  20 . However, it is preferred that the parallel drive plate  12  and rotor plate  14  remain spatially separated by a gap  30  to prevent rubbing friction there between that would be caused by the sliding of the plates against each other. In order to prevent this undesired contact between the plates, a spacer may be housed between the plates  12 ,  14 . By non-limiting example, the spacer is preferably a spherical ball or thrust bearing  18  made of steel or other hard durable material. The drive plate  12  includes a bearing recess  32  for containing the bearing  18  between the plates while preferably allowing the bearing to roll. Accordingly, the plates  12 ,  14  are preferably spaced apart by a gap  30  so that the plates do not rub against each other during operation. The spacer (e.g., spherical ball, thrust bearing  18 ) is provided between the plates to maintain a spatial separation of the gap  30  therebetween. 
         [0031]    In operation, the thrust bearing  18  is free to roll around inside the bearing recess  32  and against the rotor plate  14  to allow parallel movement between the two plates. In order to help contain the bearing  18  between the two plates, the rotor plate  14  may include a mating recess  34 . Preferably, the mating recess  34  has a circular cutout or annular groove  36  within the rotor plate  14  that is aligned with the bearing  18  during rotation of the drive and rotor plates  12 ,  14  to allow the bearing to roll around within the mating recess and the bearing recess  32  during rotation for parallel rotational movement between the drive and rotor plates. In other words, the spacer is contained in the recess  32  of one of the plates and also within the mating recess  34  in the other plate so that the spacer may be contained between the plates, thereby providing the gap  30  therebetween. While not being limited to a particular theory, the circular cutout or annular groove  36  is sized with a diameter preferably equal to or slightly larger than the diameter of eccentricity of the orbiting axis. Most preferably the bearing recess  32  and the mating recess  34  are sized to allow the spacer to move around and stay within the recesses during operation. According the size of one of the recesses may affect the preferred sized of the other recess, as readily understood by a skilled artisan. 
         [0032]      FIG. 2  illustrates the exemplary coupler  10  in perspective view. In this view, the relationship of the pins  16  and bores  28  can clearly be seen between the four pins rotatably and orbitally engaged with the bore walls  26  of the matching bores  28 . The rotor plate  14  and rotor shaft  22  are shown in opaque transparent view to show an exemplary rotating orbital relationship between the bearing  18  and the mating recess  34  of the rotor plate  14 . As can be seen in  FIG. 2 , the mating recess  34  is defined by an annular groove  36  having a mean diameter  40  about equal to the rotor plate diameter of eccentricity D e . 
         [0033]    While not being limited to a particular theory, the pins  16  preferably extend completely through the bores  28  to maximize driving contact between the pins  16  and bore walls  26  of the rotor plate  14 . In other embodiments, the pins  16  may extend partially into the rotor plate  14 . However, to maximize the transfer force onto the rotor and reliability of the coupler or coupling mechanism, the pins  16  are preferably extend completely through the bores  28 , with distal ends  38  of the pins extended through the bores  28 . 
         [0034]      FIGS. 3 and 4  depict another example of the inventive coupler substantially similar to the coupler  10  illustrated by example in  FIGS. 1 and 2 . In particular, the coupler  50  includes at least the drive plate  12 , rotor plate  14 , pins  16 , bearing  18 , drive shaft  20  and rotor shaft  22  substantially as discussed above. In addition to the coupler  10 , the coupler  50  includes a securing ring  52  adjacent to and preferably spatially separate from the rotor plate  14 . The securing ring  52  is placed about the rotor shaft  22  and preferably not in contact with the shaft as that would cause greater friction during use. The securing ring  52  includes ring apertures  54  that match the apertures  24  of the drive plate  12 . As can be seen in  FIGS. 3 and 4 , the pins  16  are also attached to both the drive plate  12  and the securing ring  52 , with the ring apertures  54  of the securing ring aligned with the pins. The distal ends  38  of the pins  16  are inserted into the apertures  54  and attached to the securing ring  52  via their attachment to the securing ring walls that define the apertures. In this construction, the second plate, illustrated as the rotor plate  14  is between the first plate illustrated as the drive plate  12  and the securing ring  52 . The securing ring  52  encircles the rotor shaft  22  and includes an opening therein large enough to accept the orbital eccentric rotation of the rotor shaft preferably without contact with the rotor shaft. 
         [0035]    The distal ends  38  of the pins  16  fit into the apertures  54  and attach to the securing ring  52  on the side of the rotor plate  14  opposite the drive plate  12  to provide greater stability to the assembly of the plates, pins and spacer that together form the coupler  50 . For example, the securing ring  52  helps to prevent the deforming of any pin  16  as the pins are secured to the drive plate  12  and securing ring  52  on opposite ends of the rotor plate  14  to structurally secure and stabilize the entire mechanism. The securing ring  52  preferably has an equal number of apertures  54  or fastening holes relative to the pins  16 . 
         [0036]    The drive plate  12  illustrated in  FIG. 3  is directly attached to a connecting rod  56  similar to the drive shaft  20  and having diametrically disposed connecting rod bores  58  for locking the connecting rod  56  to a drive shaft or driven shaft as discussed in greater detail below. Further, the rotor shaft  22  also includes a diametrically disposed connecting rod bore  58  for locking the rotor shaft  22  to a rotor  62  as will be discussed in greater detail below. 
         [0037]      FIG. 5  depicts the coupler  50  of  FIG. 3  attached to a rotor  62  and drive shaft  60 . A shaft clamp  64  is placed about the drive shaft  60  and connecting rod  56  with a sleeve  66  of the drive shaft fitted around and in contact with the connecting rod  56 . Preferably, a bolt  68  is inserted through an opening of the clamp  64  and into the connecting rod bore  58  of the connecting rod  56  to hold the drive shaft  60  and the connecting rod together. While not being limited to a particular theory, the bolts  68  may be threaded for a threaded engagement with at least one of the opening of the clamp  64 , the connecting rod bore  58  and the drive shaft sleeve  66  to fixedly lock the clamp, connecting rod and drive shaft.  FIG. 5  also illustrates a second clamp  64  holding the rotor  62  and the rotor shaft  22  together. In particular, the second clamp  64  is inserted around the rotor sleeve  66 , which is slid over the rotor shaft  22 . Preferably, a bolt  68  is inserted through an opening of the second clamp  64  and into the connecting rod bore  58  of the rotor shaft  22  to hold the rotor  62  and the rotor shaft together. Preferably, the bolt  68  that locks the rotor  62  to the rotor shaft  22  is threaded for threaded engagement with at least one of the opening of the second clamp  64 , the opening in the sleeve  66 , and the rotor shaft bore  58  so that the bolt  68  can easily be tightened against the clamp  64  and fixedly lock the clamp, rotor and rotor shaft together. 
         [0038]      FIG. 6  illustrates the structure depicted in  FIG. 5 , including the coupler  50 , within a progressive cavity pump  80 . The pump  80  includes a stator  82  with the rotor  62  mounted in the stator. In addition, the pump  80  has an intake housing at an inlet of the pump, and a connection or press fitting  86  at the pump outlet. The pump  80  is shown attached to legs  88  which may allow securement of the pump to a floor or base as desired. In operation, a shaft having a fixed axis (e.g., drive shaft  20 , driven shaft, drill shaft) is coupled to the rotor  62  having an orbiting axis, where a rotation of the rotor produces a circular path of its orbiting axis with a diameter of eccentricity D E . 
         [0039]    While the invention has been described in detail 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. For example, the drive shaft  20  of the pump may, for example, also be a driven shaft or drill shaft when the coupler is used in a motor. In addition, the plates  12 ,  14  may be interchanged, with the plate including the bore walls  26  being attached to the drive shaft, and the plate having the pins attached thereto being attached to the rotor shaft. That is, plates and shafts may be interchanged within the scope of the invention. Moreover, the pins  16  that are shown bonded to the drive plate  12  may instead be fixed within the plate apertures  24  and rotatable therein, as would readily be understood by a skilled artisan. Without further elaboration, the foregoing will so fully illustrate the invention that others may, by applying current of future knowledge; readily adapt the same for use under various conditions of service.