SUCTION ROD ASSEMBLY FOR WELL FLUID EXTRACTION AND RELATED METHODS

Abstract

The present invention provides a downhole suction rod pump assembly for use in pumping formation fluid from an oil well, and more specifically, provides a rotor operable to generate a vortex in a pump barrel without imparting torque to the plunger. The improvements to a suction rod pump assembly may be incorporated into any oil well pumping system having a linear rod and or rod string. The rotor vortex displaces formation fluid above a plunger assembly, thereby preventing heavier debris in the formation fluid from settling or lodging between a plunger and barrel boundary, thus extending the practical life of the pump.

Claims

1. A downhole suction rod pump assembly, comprising: a. a plunger having an internal conduit operable to allow for the passage of formation fluid through said suction rod pump assembly during a suction rod downstroke; b. a freely rotatable rotor having flutes, said rotor concentrically coupled to a suction rod assembly, and operable to generate a vortex within a barrel or tube; c. a reciprocating rod string operable to linearly translate said suction rod assembly vertically in said barrel; and d. wherein said rotor flutes are operable to produce a rotation of said rotor in a direction opposite to said vortex during said suction rod downstroke.

2. (canceled)

3. The assembly of claim 1, further comprising a plunger inlet operable to receive said formation fluid and a traveling valve therein said plunger inlet being operable to linearly translate to an open and closed position in response to reciprocation of said rod string.

4. The assembly of claim 1, wherein said plunger includes an open-type cage having a plurality of ports with a total combined cross-sectional area equal to said inlet of said plunger.

5. (canceled)

6. The assembly of claim 3, wherein said flutes have a cross-sectional area equal to the cross-sectional area of said plunger inlet cross-sectional area.

7. The assembly of claim 1, wherein said rotor is operable to prevent debris and particulates from settling between said plunger and barrel boundary, thereby preventing fouling of said barrel and plunger boundary.

8. The assembly of claim 1, further comprising a collar operable to rotatably couple said rotor to said connecting rod.

9. The assembly of claim 1, wherein said rotor flute has a constant pitch and a helical path around the exterior surface of said rotor with a starting angle of 0 degrees from a rotors bottom surface and has an ending angle ranging from 60 to 210 degrees at a rotors top surface.

10. A downhole suction rod pump assembly, comprising: a. a plunger having at least one internal conduit operable to receive formation fluid from a traveling valve intake port and directing formation fluid to a cage for distribution through at least one cage port; b. a reciprocating rod string operable to linearly translate a suction rod vertically in a barrel; and c. a rotor concentrically coupled to a connecting rod, wherein said rotor has at least one flute with a cross-sectional area equal to said traveling valve intake port and is operable to generate a vortex of formation fluid in said barrel above said rotor during a down-stroke of said reciprocating rod string without imparting a torque on said connecting rod.

11. (canceled)

12. The assembly of claim 10, wherein said connecting rod has a distal and proximal end wherein said distal end is fastened to said cage and said proximal end is rotatably secured to said rod string.

13. The assembly of claim 10, further comprising a pair of collars secured between said connecting rod and said rotor.

14. The assembly of claim 10, wherein said rotor intermittently rotates during a downstroke of said rod string in a direction opposite to said vortex rotation and rotation of said rotor seizes during an upstroke of said rod string.

15. The assembly of claim 10, wherein said at least one cage port is a plurality of ports each having a port sized to be substantially equal to said plunger intake.

16. The assembly of claim 10, wherein said rotor flute has a helical path with a substantially constant pitch wrapping around an exterior surface of said rotor starting a bottom surface and ending at a top surface.

17. The assembly of claim 10, wherein said rotor flute has a total combined cross-sectional area substantially equal to said plunger intake.

18. (canceled)

19. (canceled)

20. (canceled)

21. (canceled)

22. (canceled)

23. (canceled)

24. (canceled)

25. (canceled)

26. A downhole suction rod pump assembly, comprising: a. a reciprocating rod string operable to linearly translate a suction rod vertically in a barrel; b. a plunger having an internal conduit operable to direct a flow of formation fluid from at least one traveling valve intake port; and c. a rotor rotatably coupled to said assembly and positioned at or between a reciprocating rod string and said plunger, wherein said rotor has an internal conduit, a flute positioned between a top surface and a bottom surface of said rotor, and at least one discharge port for formation fluid to flow into said flute.

27. (canceled)

28. The assembly of claim 26, wherein said flute is operable to rotate said swivel and generate a vortex of formation fluid above said swivel when said suction rod is in a downstroke.

29. The assembly of claim 26, wherein said discharge port and said flute have a combined cross-sectional area that is substantially equal to said traveling valve intake port;

30. (canceled)

31. The assembly of claim 26, wherein said swivel flutes starts between the bottom surface and midline of said flute and ends between the tops surface and said midline having a constant pitch and a helical path with a starting angle of 0 degrees and an ending angle of 360 degrees.

32. The assembly of claim 26, wherein said at least one discharge port is a plurality of ports equidistantly arranged along a helical path symmetrical to said at least two flute paths.

33. (canceled)

34. The assembly of claim 28, wherein said flutes are operable to intermittently produce a rotation of said swivel in a direction opposite to said vortex during a suction rod downstroke, and intermittently stops rotating during a suction rod upstroke.

35. (canceled)

36. (canceled)

37. (canceled)

38. (canceled)

39. (canceled)

40. (canceled)

41. (canceled)

42. (canceled)

43. (canceled)

44. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1 provides an exemplary view of a suction pump rod assembly during an upstroke according to an embodiment of the present invention.

[0031] FIG. 2 provides an exemplary view of a suction pump rod assembly during a downstroke according to an embodiment of the present invention.

[0032] FIG. 3 provides an exploded view of a plunger assembly and a rotor cross-sectional view, according to an embodiment of the present invention.

[0033] FIG. 4 provides an exemplary view of a plunger assembly during a downstroke and illustrates streamlines of the fluid path, according to an embodiment of the present invention.

[0034] FIG. 5 provides an exploded view of a plunger assembly and a rotor cross-sectional view, according to an embodiment of the present invention.

[0035] FIG. 6 provides an exemplary view of a plunger assembly during a downstroke and illustrates streamlines of the fluid path, according to an embodiment of the present invention.

[0036] FIG. 7 provides a cross-sectional view of a barrel and streamlines of a fluid in a plunger assembly during a downstroke, according to an embodiment of the present invention.

DETAILED DESCRIPTION

[0037] Reference will now be made in detail to certain embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in reference to these embodiments, it will be understood that they are not intended to limit the invention. To the contrary, the invention is intended to cover alternatives, modifications, and equivalents that are included within the spirit and scope of the invention. In the following disclosure, specific details are given to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that the present invention may be practiced without all of the specific details provided.

[0038] The present invention concerns a Suction Pump Rod (SPR) system that may be incorporated into a downhole pumping system or other pumping equipment. FIGS. 1-7 provide views of an exemplary SPR assembly 100. FIGS. 1-4 provide views of the SPR assembly 100 incorporating a plunger assembly 120 that includes a rotor 121. FIGS. 5-6 provide views of the SPR assembly 100 incorporating a plunger assembly 120 that includes a flute 200. FIG. 7 provides a view of the SPR assembly 100 incorporating a plunger assembly 120 that includes a rotor 121 and a swivel rotor 200. Detailed discussions of the embodiments of FIGS. 1-4, 5-6, and 7 are provided below.

[0039] In the embodiment of FIGS. 1-4, the exemplary SPR assembly 100 may include a barrel 101 that may house a standing valve 102 and a plunger assembly 120, which includes a plunger 123, a cage 125, a distal collar 124A, a rotor 121, a proximal collar 124B, and a rotor lock 126A, that is pulled by a rod string 107. The standing valve 102 at the distal end of barrel 101 that may be operable to prevent and allow fluid to enter through an inlet 110. The plunger 123 may house a traveling ball valve 128 that may be operable to allow fluid to enter the plunger through a conduit 122 and enter an interior cavity 123.

[0040] FIG. 1 shows a cross-sectional view of all the components about the centerline A-A of an exemplary SPR assembly 100 during an upstroke of the reciprocating rod string 107, which may be operable to move the plunger assembly 120 up through the barrel 101 by fluid pressure differential. The upstroke of the rod string 107 may pull the plunger 123 upward by pressure differential, causing the ball valve 128 to seat into the plunger's inlet 122, and with the fluid within the plunger conduit 127 at a higher pressure than that in a variable control volume 130. The barrel 101 may have a standing valve 102 in the open position due to differential pressure between the well and the variable control volume 130, allowing fluid to enter through the inlet 110 and fill the space between the plunger assembly 120 and barrel 101. The fluid column above the traveling valve 128 may lift toward the surface during the upward movement of the plunger assembly 120, pushing formation fluid at the top of the barrel 101 to the surface. FIG. 2 shows a cross-sectional view of the barrel 101 exposing the novel components of the exemplary SPR assembly 100 during a downstroke of the reciprocating rod string 107. The standing ball valve 102 may be in the closed position, and traveling valve 128 may be in the open position due to a reversal in the differential pressures between the plunger assembly 120 and the variable control volume 130. The downstroke of the rod string 107 may push the plunger 123 downward, and the fluid enclosed in the variable control volume 130 (the space between the plunger assembly 120 and barrel 101) during the upstroke may enter into the plunger system through the plunger inlet 122 and may travel through the interior conduit 127 of the plunger and exit out of the cage 125 through cage ports 113 and may fill a region between a cage neck 125B and may secured to the plunger assembly at a junction where a rotor lock 126A is fastened to the cage threading 125A. The fluid may then enter into a rotor's flutes 121A, causing rotation of the rotor 121 about the neutral axis of the plunger assembly 120. The rotor flutes 121A are discussed further in more detail below.

[0041] The fluid in the system may transition through a variety of different fluid flow states. For example, during the upstroke, as described in FIG. 1, the pressure of an incompressible fluid (e.g., formation liquid) in the space between the standing valve 102 and traveling valve 128 drops causing the standing valve 110 to open. The open standing valve allows wellbore pressure to drive fluid into the inlet 110 of barrel 101, and the fluid may enter the inlet 110 in substantially laminar flow. The fluid may fill the variable control volume 130 defined by the boundary between the standing valve 102 and traveling valve 128. At the top of the upstroke, the fluid in the control volume 130 and the plunger assembly 120 may be in a substantially hydrostatic relationship.

[0042] During the downstroke of the rod string 107, the traveling valve immediately opens, and the standing valve 102 closes due to the pressure differential in the plunger's interior cavity 123 and the control volume 130. During the plungers 123 decent fluid may be transferred through the plunger's interior conduit 127, into the plunger's interior cavity 123, and out of the cage 125. When the fluid encounters the plunger's interior cavity 123, the fluid may be in a transient state and return to a substantially laminar flow and may exit cage 125 through cage ports 113 in a transient state. The formation fluid may include a substantial amount of particulates and sediment therein. The sediment and particulates cause damage to conventional drill string components as they flow through the system. Because of the tight tolerances in the suction rod assemblies, granular material (e.g., sand) causes scoring and other damage to components in the suction rod assembly. In embodiments of the present invention, the cage neck 125B may provide a fluid region (area available for fluid to flow) with a greater cross-sectional area than at any other location in the plunger assembly 120, because the fluid region is greater (fluid fills the region around the cage neck 125B and the barrel 101), the fluid has a negative pressure differential after the ports 113. However, when the fluid encounters the rotor 121 the negative pressure differential of the fluid may return to the initial pressure of the fluid when in the plunger's interior conduit 127. The rotor's plurality of flutes 121A when combined have a cross-sectional fluid area equal to the plunger inlet 122, but when the flutes are analyzed independently an individual flute 121A may provide a fluid area as a ratio of one to a plurality of flutes. Individually a rotor flute 121A provides a reduced cross-sectional area for example, if a plurality of provided flutes is six then the rotor flute 121A may provide a one to six cross-sectional fluid region, and if a plurality of provided flutes is four then the rotor flute 121A may provide a one to four cross-sectional fluid region. The individual cross-section of a rotor flute 121A provides a substantially smaller region for fluid to fill and the fluid enters into the flute 121A in a substantially transient state and as the fluid flows through the helical passage of the flute the pressure and velocity increase and the fluid may transition to a turbulent state, at the mid-section of the rotor 121, and may exit the rotor flute 121A in a turbulent state. The rotor flutes 121A may be operable to generate a turbulent region that maintains a substantially helical flow above the rotor 121. During the turbulent state of fluid exiting the rotors flutes 121A, the sediment and debris carried toward the rod string 107 is maintained in the turbulent water column and does not have sufficient time or weight to settle between the plunger 123 and barrel 101 walls. As a result the sediment and debris cannot flow into spaces between the plunger assembly 120 and the barrel 101, or between other structures, thereby preventing the scoring and other damage experienced by conventional SPR systems. The fluid after the turbulent region may transition back to transient state, and ultimately laminar flow as the fluid is lifted to the surface. Thus, the rotor 120 is operable to extend the life of the SPR assembly 100 of the present invention and improves the overall operation of the system.

[0043] FIG. 3 shows a perspective exploded view of a section of the plunger assembly 120 according to the present invention. The rotor 121 may couple to the plunger assembly with a cage 125 that may have a plurality of ports 113 circumferentially distributed about the central axis. The cage 125 may have threading in the interior of the cage junction 125A to connect with the rod lock 126 having, e.g., male threading 126A. Rotor 121 may have a distal collar 124A and a proximal collar 124B, for coupling the rotor 121 to the plunger assembly 120. The rotor 121 may have a plurality of flutes 121A operable to direct the fluid on a rotational path. The cross-sectional area A-A of the rotor 121 shows the flutes 121A equidistantly distributed around the neutral axis of the rotor and may have a cumulative area substantially equal to the inlet 122 cross-sectional area of the plunger 123. The helical path of the flutes 121A may have a rotational path starting from the distal end and ending at a proximal end of the rotor 121. The rotational path may have a length substantially equal to the length of the rotor 121 and may have a starting angle of 0 degrees with respect to the longitudinal axis of the rotor 121 and have a final angle ranging from about 60 degrees to about 210 degrees with respect to the longitudinal axis of the rotor 121. The pitch of the helix 121A may be constant, and the combined cross-sectional area at any point along the path may be equal to the cross-sectional area of the intake port 122 of the plunger 123 in order to have a negligible effect on fluid pressure in the interior conduit 127. The rotational path of the flutes 121A may be distributed around the rotor 121 in a clockwise or counter-clockwise orientation; the flutes 121A are illustrated in a clockwise orientation.

[0044] An exemplary view of the upper portion of a plunger assembly 120 during the downstroke is illustrated in FIG. 4 and provides insight into fluid flow when entering and exiting the rotor 121 of the present invention. The flow of a particle in the formation fluid is illustrated with dashed lines, and the arrows indicate the corresponding direction of the particle's path. The fluid in the plunger's internal conduit 127 may, during a downstroke, enter the cage 125 in a substantially laminar flow and may exit through the cage ports 113 in a transient state. The fluid may come into contact with the distal end of the rotor 121 s and may be directed into the rotor flutes 121A. The fluid may travel upward through the flutes 121A and may have generally rotational turbulent flow, and the force of the fluid in contact with the flutes 121A may produce a torque T.sub.1 on the rotor 121. The rotor 121 may be operable to rotate opposite to the path of the rotor flutes 121A. If the rotor flutes 121A have a clockwise orientation, the rotor 121 may rotate counter-clockwise, as shown by the torque line T.sub.1. Similarly, if the rotor flutes 121A has a counter-clockwise orientation, the rotation of the rotor may be in a clockwise direction. However, during the upstroke of the rod string, the traveling valve 128 may be in the closed position as shown in FIG. 1, preventing the fluid from flowing through the plunger inlet 122. Thus, fluid may flow through the rotor 121 or rotor flutes 121A during upstroke, and no rotation or torque is acting on the rotor 121. Therefore, the rotor 121 rotates intermittently, only during each downstroke. In some embodiments, the rod string 107 may be coupled to the rotor lock 126 by a swivel coupling allowing for rotation of the plunger 123 with respect to the rod string 107.

[0045] FIG. 5 shows a view of an upper portion of the plunger assembly 120 according to an embodiment of the present invention. The plunger assembly 120 may include a swivel rotor 200 in place of the rotor 121 discussed above. FIG. 5 illustrates a frontal view and two sectional views A-A and B-B. The swivel rotor 200 may have a plurality of flutes 210 and through passages 205 and may be configured to attach the plunger assembly 120 and via collars 124A, 124B on each end. Cage 125 may have internal threading operable to receive the threaded rotor lock 126A, thereby securing the swivel rotor 200 in the rod string 107. The swivel rotor 200 may have a plurality of flutes 210 having a rotational path around the exterior surface. The flutes 210 may have a depth that does not penetrate through to an internal conduit 202 of the swivel rotor 200. The swivel rotor 200 may also have through passages 205 that are operable to allow fluid to pass through and enter in the internal conduit 202. The swivel rotor 200 may have a plurality of through passages 205 symmetrically distributed between the flutes 210. The cross-section B-B shows the cross-sectional area of the flutes 210, which have a geometry substantially equal to the cross-sectional area of the inlet 122 of the traveling valve 128 shown in FIG. 2. The swivel rotor 200 may have a varying cross-sectional area, and the through passage 205 may have a cross-sectional area equal to the inlet 122 of the traveling valve 128. The helical structure of the flutes 210 may be formed in the exterior surface 203 between a top surface 206 and bottom surface 207 without passing through the top surface 206 and bottom surface 207 of the swivel rotor 200. The top surface 206 may receive proximal collar 124A and the bottom surfaces 207 may receive the distal collars 124B, allowing the swivel rotor 200 to freely rotate about the central axis of the plunger assembly 120. The proximal and distal collars may assist the swivel rotor 200 to freely rotate and aid in preventing wear to the rotor lock 126A, connecting rod 126, and other structures in the SPR assembly 100, by operating like journal bearings where the rotation of the swivel rotor provides lubrication from the formation fluid and a boundary layer of fluid may form between the collar and rotor swivel and the collars interior conduit and the connecting rod 126. The connecting rod 126 may be secured to the cage 125 and may provide sufficient pressure to the proximal collar 124A and distal collar 124B to prevent the swivel rotor 200 from linear translation but allowing for rotation about the neutral axis.

[0046] On the downward stroke, the control volume and formation fluid 130 between the plunger-barrel boundary 101 may enter into the plunger 127 with the traveling valve 128 and standing valve 102 configured as shown in FIG. 2. The formation fluid may travel upward through the inlet 122, and transition to a relatively uniform velocity profile inside the plunger's interior conduit 127. The fluid may enter into cage 125 and exit out of the cage ports 113 and may have a lower pressure when entering into the boundary between cage 125 and the rotor lock 126A.

[0047] FIG. 6 illustrates an exemplary embodiment of the swivel rotor 200 coupled to the plunger assembly 120 during a downstroke and shows the flow velocities of formation fluid, according to the present invention. The fluid in the interim space between cage 125 and the bottom surface 207 of the swivel rotor 200 may experience wakes due to interference from the swivel rotor bottom surface 207. The fluid may attempt to compress between the barrels 101 walls and the swivel's exterior surface 203. Between the swivels, exterior perimeter 203 and the barrel 101 interior wall may be a boundary layer of a formation fluid that may flow freely into the flutes 210 and into the through passages 205 and fills the interior conduit 202 of the swivel rotor 200. The swivel rotor 200 may rotate in a direction opposite to the torque line T.sub.2, and the swivel rotor 200 may output a small rotation vortex of fluid above the swivel's top surface 208. On the upstroke of the rod string, the traveling valve 128 may be in the closed position as shown in FIG. 1, preventing the fluid from flowing into the plunger inlet 122. Thus, there may be fluid flowing through the swivel rotor 200 and the flutes 210, but substantially no torque output from the swivel rotor 200. As a result, the swivel rotor 200 may rotate intermittently, only during each downstroke.

[0048] In some embodiments, the swivel rotor 200 may fixedly attach to the cage 125 on the bottom surface 207 of the swivel rotor 200, and the top surface 206 may be rotatably coupled to the rotor lock 126, allowing for the transfer of torque to the plunger assembly 120 about the rod lock 126. In other embodiments, the swivel rotor 200 may provide the same function as the cage 125 and replace the cage 125. In such embodiments, the fluid may flow upwards through the plunger 127 and out the through-holes 205, and fluid may flow into flutes 210 and producing a rotary torque to the plunger 127. In another embodiment, the swivel's bottom surface 207 may be rotatably coupled to the plunger 123, and the top surface 206 may be rotatably coupled to the rod lock 126 and allowing the swivel rotor 200 to rotate without applying torques to either the rotor lock 126 or the plunger 123.

[0049] In another embodiment, it may be advantageous to provide a combination of the rotor 100 and swivel rotor 200 as illustrated in the exemplary view of an upper plunger assembly 120 according to the embodiment shown in FIG. 7. The bottom surface 207 of the swivel rotor 200 may be fixed to the plunger 123, and the top surface 206 may be rotatably attached to the collar 124B. A rotor swivel junction 150 may be operable to couple the rotor 121 and the swivel rotor 200 via collars 124A and 124B. The rotor 121 may be rotatably coupled with the rod lock 126 and junction 150 via collar 124A. On a downstroke of the rod string 107, the column of formation fluid between the standing valve 102 and the plunger inlet 122 may flow into the plunger's internal passage 127 and flow upward into the internal conduit 202 of the swivel rotor 200.

[0050] The fluid may flow out the through-holes 205 and enter swivel flutes 210, and travel upwards along the barrel's boundary 101. The fluid may exit out the through-holes 205 in a transient state and may interface with the swivel flutes 210, which may be operable to impart a torque in a clockwise rotation to the plunger 123 without imparting a torque on the rotor swivel junction 150, as shown by the torque line T.sub.3. The fluid may then exit the swivel flutes 210 on a rotational path substantially equivalent to the swivel flutes 210, and the fluid may then come into contact with the rotor 121. The fluid may enter into the rotor flutes 121A, displacing debris and particulates in the formation fluid, and may exit the rotor flutes 121A in a substantially turbulent state. The flutes 121A may be operable to impart a rotation to the rotor 121 as shown by the torque line T.sub.4 without applying any additional torque to the system, and the fluid may be in a vortex when exiting the flutes 121A. The plunger 123, swivel rotor 200, and rotor may rotate in their respective directions, and the junction 150 rotor lock 126 and rod string 107 may not rotate. The swivel rotor 200 rotation distributes the wear on the plunger 123 to be more uniformly around the circumference of the plunger, and the rotor 121 may rotate in the opposite direction and displace debris in the fluid preventing debris from settling between the boundary of the inner wall of the barrel 101 and the plunger 120.

[0051] On the upstroke of the rod string, the traveling valve 128 may be in the closed position as shown in FIG. 1, and the fluid may be prevented from flowing into the plunger inlet 122. Because there is no fluid flowing through the rotor 121 or swivel rotor 200, The flutes 121, 210 produce no torque, and the plunger assembly 120, rotor 121, and swivel rotor 200 may rotate intermittently, only during each downstroke. In another embodiment, the swivel rotor 200 may be rotatably coupled to the plunger 123, and the swivel flutes 210 are operable to rotate the swivel rotor without imparting torque to the plunger or the junction 150.

[0052] In other implementations of the present invention, the rotor flutes 121A helical path may have a counter-clockwise path that orients the flutes 121A in the opposite direction as illustrated in FIGS. 1-4, and FIG. 7. The rotation and torque of the rotor 121 may have a rotational path that is opposite to the helical path of the flutes 121A. Likewise, flutes 210 may have a clockwise rotational path opposite to the rotation of the flutes illustrated in FIG. 5-FIG. 7. The through-holes 205 of the swivel rotor 200 may be placed on the flutes 210 path and may provide more torque to the swivel rotor and a higher flow.

CONCLUSION/SUMMARY

[0053] The present invention provides an improved suction rod pump assembly with a rotor operable to displace formation fluid above a plunger assembly, thereby preventing debris in formation fluid from settling between a plunger and barrel boundary. The present invention is operable to generate a vortex of fluid above the plunger assembly without imparting a torque onto the system. It is to be understood that variations, modifications, and permutations of embodiments of the present invention, and uses thereof, may be made without departing from the scope of the invention. It is also to be understood that the present invention is not limited by the specific embodiments, descriptions, or illustrations or combinations of either components or steps disclosed herein. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. Although reference has been made to the accompanying figures, it is to be appreciated that these figures are exemplary and are not meant to limit the scope of the invention. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.