Patent Abstract:
A hydrodynamically lubricated sealing element for applications where the pressure of a contained fluid can be significantly greater than the pressure of the seal lubricant. The sealing element retains the pressure of the contained fluid and provides hydrodynamic lubricant pumping activity at the dynamic sealing interface to enhance service life. The invention is particularly suitable for oilfield drilling swivel washpipe assemblies, downhole drilling tools, and rotary mining equipment, and for applications such as artificial lift pump stuffing box assemblies and centrifugal pumps where a rotating shaft penetrates a pressurized reservoir that is filled with abrasive-laden liquids, mixtures, or slurries.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Appln. No. 61/268,698 filed Jun. 15, 2009, entitled “Hydrodynamic Washpipe Packing Ring.” U.S. Provisional Patent Appln. No. 61/268,698 is hereby incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to seals that are suitable for containing a pressurized fluid that may be abrasive, and for providing a film of lubricant at the dynamic sealing interface in response to relative rotation to enhance pressure and rotary speed capabilities. 
     The seals of the present invention are particularly suitable for use in rotary swivel assemblies, such as the general type of oilfield washpipe assemblies that are described in U.S. Pat. No. 2,764,428 entitled “Wash Pipe Mounting For Swivels,” IADC/SPE Paper 59107 “A New Hydrodynamic Washpipe Sealing System Extends Performance Envelope and Provides Economic Benefit,” and commonly assigned U.S. Pat. No. 6,007,105 entitled “Swivel Seal Assembly.” 
     2. Description of the Related Art 
     Rotary seals are used to establish sealing between relatively rotatable machine components, for the purpose of retaining a pressurized fluid. The type of sealing ring that is most commonly used in oilfield washpipe assemblies is typically referred to as washpipe packing, and dates at least to U.S. Pat. No. 2,394,800 entitled “Rotary Swivel.” Such conventional washpipe packing is used to retain pressurized drilling fluid. Differential pressure energizes the dynamic sealing lip against the washpipe. While this type of packing has served the oilfield for many years, it is not suitable for the higher speeds and pressures of today&#39;s deep wells. The problems and extreme expenses associated with failures of conventional packing in deep wells are described in IADC/SPE Paper 59107. 
     The antecedents to the packings used in many other types of applications are shown, for example, in U.S. Pat. No. 2,442,687 entitled “Packing For Stuffing Boxes” and U.S. Pat. No. 2,459,472 entitled “Rotary Swivel.” 
     In general, the term “packing” simply refers to a sealing ring that is intended to be used in a “stuffing box” of one sort or another. “Packing” and “stuffing box” are terms that date back to the 1770&#39;s, and perhaps earlier. A stuffing box is a housing with a deep cylindrical cavity that receives a plurality of packing rings. Some or all of the packing rings are often installed in abutting relation with spacer rings that perform a packing ring supporting function. For several examples of spacer/support rings, see the aforementioned U.S. Pat. Nos. 2,394,800, 2,442,687, and 2,459,472, and IADC/SPE Paper 59107. 
     Commonly assigned U.S. Pat. No. 6,334,619, entitled “Hydrodynamic Sealing Assembly,” shows a hydrodynamically lubricated packing ring assembly that has the disadvantage of requiring an expensive wavy backup ring. 
     Kalsi Engineering manufactures various configurations of hydrodynamic rotary seals, and sells them under the registered trademark “KALSI SEALS.” The factors involved in using such seals to contain a pressurized fluid are described in U.S. Pat. No. 6,334,619. Typical seal configurations require a lubricant pressure that is greater than, or nearly equal to, that of the contained fluid. To contain a highly pressurized fluid, one can use a pair of oppositely-facing seals; one to serve as a partition between the lubricant and the pressurized fluid, and the other to retain the lubricant, as described in conjunction with FIGS. 3-38 of the Kalsi Seals Handbook, Revision 1 (Kalsi Engineering, Inc. Document No. 2137 Revision 1, 2005). The lubricant is maintained at a pressure equal to or greater than that of the contained fluid. This scheme ensures that neither seal is exposed to a high differential pressure acting from the wrong side, but requires a special mechanism to maintain the lubricant pressure at or above that of the contained fluid. 
     Many applications, such as the oilfield drilling swivel, the progressive cavity artificial lift pump, centrifugal pumps, and rotary mining equipment, would benefit significantly from a hydrodynamically lubricated rotary packing ring seal having the ability to operate under conditions where pressure of the contained fluid is higher than the lubricant pressure. 
     SUMMARY OF THE INVENTION 
     The present invention is a rotary sealing arrangement that overcomes the above-described shortcomings of the prior art. The rotary seal rings of the present invention are used to establish sealing with respect to a relatively rotatable surface (such as a shaft or washpipe). A dynamic lip deforms against the relatively rotatable surface, establishing an interfacial contact footprint that varies in width from place to place. 
     An aspect of the present invention is to provide a simple and compact rotary sealing arrangement for containing a pressurized media such as oilfield drilling fluid, where the rotary seals employ the advantage of maintaining a film of lubricant at the dynamic sealing interface during rotary operation, without requiring the undesirable complexity of a wavy backup ring, and without the undesirable complexity of maintaining the lubricant at a pressure that is greater than the pressure of the pressurized media. Hydrodynamic geometry on a dynamic sealing lip interacts with a lubricating media during relative rotation to wedge a lubricating film into the dynamic sealing interface between the seal and the relatively rotatable surface. The lubricating film is distributed across the dynamic sealing interface and migrates toward, and into, the pressurized fluid, and thus provides a contaminant flushing action. The lubricating film reduces seal running torque, providing reduced wear and reduced seal-generated heat. In other words, the dynamic sealing lip slips or hydroplanes on a film of lubricating fluid during periods of relative rotation between the dynamic sealing lip and relatively rotatable surface. When relative rotation stops, the hydroplaning activity stops, and a static sealing relationship is re-established between dynamic sealing lip and relatively rotatable surface. 
     One feature of the present invention is a hydrodynamic inlet that is supported by one or more adjacent boundaries, such as a recess support corner, a first recess end and/or a support shoulder, in order to resist differential pressure-induced inlet collapse, so as to retain the hydrodynamic wedging function of the hydrodynamic inlet despite the high differential pressure acting across the rotary seal. 
     The dynamic sealing surface is preferably interrupted by angled slots/recesses that have a shelf-like shape on at least one side thereof. The slots/recesses incorporate a hydrodynamic inlet shape having an end that may be approximately tangent with the dynamic sealing surface. 
     The shelf-like shape or shapes prevent the slots/recesses from collapsing completely against the shaft when the pressure of the contained fluid is higher than that of the seal lubricant. The lubricant is swept into the dynamic interface between the dynamic sealing surface and the washpipe, at the location near the extrusion gap where it is needed most for interfacial lubrication. A shelf-like shape also creates an angled zone of locally increased interfacial contact pressure that diverts lubricant film toward the environment-side edge of the dynamic sealing surface. 
     A feature of a preferred embodiment of the present invention is compatibility with the type of conventional packing ring support structure that is found in conventional stuffing boxes, including, but not limited to, the washpipe assemblies that are used in oil and gas well drilling. 
     An optional feature of the present invention is the compression of a portion of a static sealing rim between a first sealing housing component and a second sealing housing component to establish a static sealed relationship between the first and second sealing housing components, and to prevent rotation of the seal/packing relative to the first and second seal housing components. 
     It is intended that the seal of the present invention may incorporate one or more seal materials without departing from the spirit or scope of the invention, and may be composed of any suitable sealing material, including elastomeric or rubber-like materials that may, if desired, be combined with various plastic materials such as reinforced polytetrafluoroethylene (“PTFE”) based plastic. If desired, the rotary seals may be of monolithic integral, one piece construction or may also incorporate different materials bonded, co-vulcanized, or otherwise joined together to form a composite structure. For use as an oilfield washpipe packing, a preferred seal material is a fabric reinforced elastomer compound. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       So that the manner in which the above recited features, advantages, and objects of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof that are illustrated in the appended drawings. It is to be noted, however, that the appended drawings only illustrate preferred embodiments of this invention, and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments that vary only in specific detail. 
       In the drawings: 
         FIG. 1A  is a fragmentary cross-sectional view of a ring-shaped hydrodynamic seal according to a preferred embodiment of the present invention, the seal shown in an installed condition in the absence of differential pressure; 
         FIG. 1B  is a fragmentary shaded perspective view of a preferred embodiment of the hydrodynamic seal in an uninstalled state; 
         FIG. 1C  is a fragmentary cross-sectional view of the ring-shaped hydrodynamic seal shown in  FIG. 1A  in an installed condition and in the presence of differential pressure; 
         FIG. 1D  is a fragmentary shaded perspective view of the hydrodynamic seal of  FIG. 1B  taken from a different perspective; 
         FIGS. 2-4  are fragmentary cross-sectional views of a ring-shaped hydrodynamic seal according to other preferred embodiments of the present invention; 
         FIGS. 5 and 6  are fragmentary cross-sectional views of a ring-shaped hydrodynamic seal according to other preferred embodiments of the present invention, further showing an energizer element and with the seal arranged in tandem with another seal; and 
         FIG. 7  is a fragmentary perspective view of a ring-shaped hydrodynamic seal according to another preferred embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     
       FIGS. 1A-1D 
     
       FIGS. 1A ,  1 B  1 C and  1 D are views representing one preferred embodiment of the present invention, and should be studied together, in order to attain a more complete understanding of the invention. Features throughout this specification that are represented by like numbers have the same function. While the invention is readily adaptable to various sealing configurations,  FIGS. 1A-1D  illustrate the invention in the context of an oilfield washpipe packing-type seal, and disclose how to achieve hydrodynamic interfacial lubrication using a novel collapse-resistant hydrodynamic inlet geometry. 
     The rotary seal of a preferred embodiment of the present invention is illustrated generally at  2  in its installed condition, in the absence of differential pressure in  FIG. 1A , and  FIG. 1C  illustrates the rotary seal  2  in its installed condition in the presence of differential pressure.  FIGS. 1B and 1D  show two different perspective views of the rotary seal  2  in its uninstalled, uncompressed condition. 
     With reference to  FIGS. 1B and 1D , the rotary seal  2  has a ring-like, generally circular configuration. In other words, the rotary seal is a seal body that forms a ring. As with the seal of U.S. Pat. No. 2,394,800, the cross-section of the seal has a generally V-shape, with one side of the “V” clamped in compression, and the other side of the “V” providing a dynamic sealing function as shown in  FIGS. 1A and 1C . 
     The terms “ring-like” and “ring” are used with the understanding that the term “ring” is commonly understood to encompass shapes other than perfectly circular. As an example, a decorative finger ring often has beaded edges or a sculpted shape, yet is still called a ring. As another example, the “ring” of U.S. Pat. No. 1,462,205 is not everywhere circular. There are thousands of precedents for using the term “ring-like” in a patent, and many patents use the term in conjunction with a seal or a body of a seal. For example, see U.S. Pat. Nos. 612,890, 4,361,332, 4,494,759, 4,610,319, 4,660,839, 4,909,520, 5,029,879, 5,230,520, 5,584,271, 5,678,829, 5,833,245, 5,873,576, 6,109,618, and 6,120,036. Note that in many of the examples, the seal in question has features that result in the shape not being everywhere circular. For example, in some cases the dynamic lip of the ring-like seal has a wavy lubricant-side shape. 
     The rotary seal  2 , being a generally circular ring, defines a theoretical axis. While the theoretical axis is not illustrated, the term “axis” is well-understood in the art, and in the field of drafting is sometimes illustrated using a centerline. For orientation purposes, it should be understood that in all of the cross-sectional views herein, the cutting plane of the cross-section is aligned with and passes through the theoretical axis of the rotary seal  2 ; i.e., the theoretical centerline lies on the cutting plane. The circumferential direction of relative rotation is normal (perpendicular) to the plane of the cross-section, and the theoretical centerline of rotary seal  2  generally coincides with the axis of relative rotation. 
     Referring to  FIGS. 1A-1D , the rotary seal  2  includes a dynamic sealing lip  4  of generally annular form and a static sealing rim  6  of generally annular form. The static sealing rim  6  is sometimes referred to in the art as a “static sealing lip.” The static sealing rim  6  is typically oriented in generally opposed relation to the dynamic sealing lip  4 , but designs are possible where the static sealing rim  6  is not oriented in opposed relation to the dynamic sealing lip  4 . 
     In the preferred embodiment of the present invention, the dynamic sealing lip  4  and the static sealing rim  6  are integral features of the rotary seal  2 . The dynamic sealing lip  4  is adapted for sealing against a relatively rotatable surface  8  of a first machine component  10  as shown in  FIGS. 1A and 1C . In an oilfield washpipe assembly, the first machine component  10  is the washpipe. 
     The rotary seal  2  is installed within a seal groove that is typically defined by a first groove wall  12 , a second groove wall  14 , and a peripheral wall  16 . The seal groove and the relatively rotatable surface  8  together form what is commonly called a seal gland. The peripheral wall  16  is positioned in spaced relation to the relatively rotatable surface  8 . Seal gland arrangements are possible where the second groove wall  14  is unnecessary. When the second groove wall  14  is used, it is positioned in spaced relation to the first groove wall  12 . 
     The seal groove is preferably defined by a second machine component  18  that may be formed of one or more components. In  FIGS. 1A and 1C , the second machine component  18  is an assembly formed by two separable components, a first spacer ring  20  and a second spacer ring  22 . The rotary seal  2  is oriented (i.e., positioned) by the second machine component  18  for sealing with respect to the relatively rotatable surface  8  of the first machine component  10 . 
     If desired, the first spacer ring  20  and a second spacer ring  22  can be generally shaped like the conventional spacer rings that are shown in the conventional washpipe assembly of FIG. 11 of IADC/SPE Paper 59107. The seals of the present invention may, if desired, be shaped to fit directly into such conventional washpipe assemblies as replacement packing elements. 
     The first spacer ring  20  and the second spacer ring  22  may be retained or attached together by any suitable retaining or attachment means, including, for example, threaded means such as threads, bolts, screws, studs, hammer unions, etc., and including external clamping means, bayonet-type latches, deformable rims or tangs, retaining ring(s), welding, soldering, bonding, friction, interference fit, etc., without departing from the spirit or scope of the invention. The first and second spacer rings  20  and  22  may be made from any suitable material, such as, for example, metal, plastic or reinforced plastic, or a combination thereof. 
     The most common method for securing the first spacer ring  20  and the second spacer ring  22  together is to axially clamp them inside of a housing, as shown, for example, in U.S. Pat. No. 2,394,800 and FIG. 11 of IADC/SPE Paper 59107. As shown in U.S. Pat. No. 2,394,800, FIG. 11 of IADC/SPE Paper 59107, and  FIGS. 5 and 6  herein, the spacer rings may, if desired, incorporate one or more lubricant communication passages such as drilled holes. If desired, the first spacer ring  20  and the second spacer ring  22  can have a sealed relationship with a mating housing, as shown in  FIG. 6  of commonly assigned U.S. Pat. No. 6,334,619. 
     Although the second machine component  18  is illustrated as an assembly formed by two separable components, such is not intended to limit the scope of the invention. The manner of positioning the rotary seal  2  admits to other equally suitable forms. For example, the rotary seal  2  could be configured for installation within a groove that is formed in a second machine component  18  that is of one piece construction. 
     On a washpipe, the relatively rotatable surface  8  is an external cylindrical shape. Although the invention is disclosed here in the context of a familiar washpipe packing-type of seal, such is not intended to limit the configuration of the relatively rotatable surface  8 . It is well-established that hydrodynamic rotary seals can be configured for, and used in, both radial- and face-sealing applications. 
     Relatively rotatable surface  8  can take the form of an externally- or internally-oriented, substantially cylindrical surface, as desired, with rotary seal  2  positioned radially between peripheral wall  16  and relatively rotatable surface  8 , in which case the axis of relative rotation would be substantially parallel to relatively rotatable surface  8 . In a radial sealing configuration, dynamic sealing lip  4  is oriented for compression in a substantially radial direction, and peripheral wall  16  may, if desired, be of substantially cylindrical configuration. 
     Alternatively, relatively rotatable surface  8  can take the form of a substantially planar surface, with rotary seal  2  compressed axially between peripheral wall  16  and relatively rotatable surface  8  in a “face-sealing” arrangement, in which case the axis of relative rotation would be substantially perpendicular to relatively rotatable surface  8 . In an axial (face) sealing configuration, dynamic sealing lip  4  is oriented for compression in a substantially axial direction, and peripheral wall  16  may be of substantially planar configuration. In what is contemplated to become the most common configuration, relatively rotatable surface  8  is the external cylindrical surface of a shaft, sleeve, or washpipe. 
     In summary, the rotary seal  2  can be configured for uses as a radial seal or a face seal by configuring the dynamic sealing lip  4  to be located at either the inside diameter, the outside diameter, or the end of the seal, while maintaining the advantages of the invention that are disclosed herein. 
     The static sealing rim  6  is adapted for sealing with respect to the second machine component  18 . Typically, the static sealing rim  6  is adapted for sealing with respect to the second machine component  18  by virtue of being adapted to establish sealing contact pressure with respect to the second machine component  18 . This sealing contact pressure is typically achieved by having some part of the static sealing rim  6  in compressed contact with the second machine component  18 . However it is achieved, when the rotary seal  2  is installed, the static sealing rim  6  establishes a sealed relationship with the second machine component  18 . In the example shown in  FIGS. 1A and 1C , the sealed relationship with the second machine component  18  is established by axial clamping of the static sealing rim  6  between the first spacer ring  20  and the second spacer ring  22 . This is not meant to imply that the invention is limited to seals having a sealing rim  6  that is axially clamped. Other means of establishing a sealed relationship between a static sealing rim  6  and a second machine component are known in the art, and are applicable to the present invention. For example, an energizer element  72  such as a spring ( FIG. 6 ), or an elastomer element ( FIG. 5 ) can be used to establish the sealing contact pressure. For another example, interference is sometimes used to establish the sealing contact pressure. 
     The dynamic sealing lip  4  incorporates a dynamic sealing surface  26  for sealing contact with the relatively rotatable surface  8 . In the uncompressed state of the rotary seal  2  ( FIGS. 1B and 1D ), the dynamic sealing surface  26  is preferably tapered, assuming the general shape of a truncated cone. The dynamic sealing lip  4  also includes at least one force receiving surface  28 . The force receiving surface  28  can be of any suitable shape that performs the functions described herein that the force receiving surface  28  serves. 
     The rotary seal  2  may be composed of any suitable sealing material, including, for example, elastomeric or rubber-like materials such as an elastomer compound or a combination of one or more elastomer compounds, various plastic materials, different materials bonded together to form a composite structure or inter-fitted together, or a combination of a suitable plastic and an elastomer compound. It is preferred, however, that the seal  2  be made from a reinforced material, such as fabric-reinforced elastomer compound. 
     For use in oilfield washpipe assemblies, the rotary seal  2  is typically made primarily from a fabric-reinforced elastomer compound. Commonly used materials include cotton fabric-reinforced nitrile rubber (NBR), cotton fabric-reinforced hydrogenated nitrile rubber (HNBR), and aramid fabric-reinforced HNBR. As is commonly done with oilfield washpipe packings, a local end portion of the static sealing rim  6  may be constructed of a ring of homogeneous elastomer compound (for example, see  FIG. 4 ). 
     It is commonly understood by those of ordinary skill in the art that elastomers used in seal construction are compounds that include one or more base elastomers. Such base elastomers include, but are not limited to, HNBR (hydrogenated nitrile rubber), HSN (highly saturated nitrile), FKM (fluorocarbon rubber), FEPM (also known as TFE/P or tetrafluoroethylene and propylene copolymer), and EPDM (ethylene propylene diene monomer). Such compounds may include other compounding agents including fillers, processing aids, anti-degradants, vulcanizing agents, accelerators, and activators. The effects of the ingredients used are generally understood by those of ordinary skill in the art of compounding elastomers. Likewise, the ingredients used in manufacturing plastics that are used in seal construction are generally understood by those of ordinary skill in the art of developing plastic seal materials. 
     A low pressure end  30  of the rotary seal  2  has a surface that generally faces the first groove wall  12 , and is adapted for being in supporting contact therewith. As shown in  FIGS. 1A-1C , if preferred, the low pressure end  30  can have a “V” shape when viewed in cross-section, for being supported by a mating V-shaped first groove wall  12 . This aspect of rotary seal  2  is simply part of the basic, well-known washpipe packing geometry shown, for example, in  FIG. 3  of U.S. Pat. No. 2,394,800. Referring to  FIG. 1B , the transition between the dynamic sealing surface  26  and the low pressure end  30  is referred to herein as the lubricant end transition  60 . 
     When the low pressure end  30  and the first groove wall  12  have mating “V” shapes, the first groove wall  12  comprises first wall part  12 A and first wall part  12 B, and the low pressure end  30  comprises low pressure end portion  30 A and low pressure end portion  30 B as shown in  FIGS. 1A and 1C . 
     The first groove wall  12  forms a support surface for the rotary seal  2 . As shown, it is preferable that at least a portion of the first groove wall  12  (i.e., first wall part  12 B) establishes a tapered (i.e., shaped like a portion of a cone) support surface for the rotary seal  2 . Preferably, any remaining portion of the first groove wall  12  establishes the first wall part  12 A. A part of the first groove wall  12  is preferably angulated, establishing an acute included angle  62  with respect to the relatively rotatable surface  8  of the first machine component  10 . 
     The rotary seal  2  is designed for relative rotation with respect to the relatively rotatable surface  8 . It is to be understood that this relative rotation can be achieved by rotating the first machine component  10 , or by rotating the rotary seal  2 , or by simultaneously rotating both the rotary seal  2  and the first machine component  10  independently. If the rotary seal  2  is to be rotated, it is preferred that it be accomplished by rotating the second machine component  18 . Referring to  FIG. 1B , the rotary seal  2  shown is adapted for a relatively rotatable surface  8  of a first machine component  10  (e.g., a shaft) having a direction of relative rotation represented by the arrow  46  (i.e., the shaft rotation being shown in a counter-clockwise direction). The seal design is reversed (i.e., made in a minor image version) for applications in which the relatively rotatable surface  8  has a direction of relative rotation  46  opposite of that shown in  FIG. 1B  (i.e., the shaft rotating in a clockwise direction). If the rotary seal design shown in  FIG. 1B  rotates around a stationary shaft, it is to be understood that the seal would rotate in a clockwise direction. 
     The rotary seal  2  preferably has an exclusion edge  32  that is preferably generally circular, in accordance with the teachings of the prior art. When the rotary seal  2  is installed, the exclusion edge  32  contacts the relatively rotatable surface  8  as shown in  FIG. 1A . The exclusion edge  32  is formed by an intersection between the dynamic sealing surface  26  and an adjacent surface of the dynamic sealing lip  4 , as shown. Due to the exclusion edge  32  being substantially circular, it is substantially aligned with the possible directions of relative rotation, so that it does not produce a hydrodynamic wedging action in response to relative rotation, thereby facilitating containment of a contained media  40 . 
     Since perfect theoretical circularity is seldom if ever obtainable in any feature of any manufactured product in practice, it is to be understood that when “circular,” “substantially circular,” “substantial circularity,” or similar terms are used to describe attributes of the invention, the terms are not to be misconstrued as an intent to achieve the unobtainable; i.e., perfect theoretical circularity. 
     As illustrated in  FIG. 1B , the dynamic sealing surface  26  has a maximum surface width  34  and a minimum surface width  36 . When rotary seal  2  is installed, the dynamic sealing lip  4  is deformed into contact with the relatively rotatable surface  8 , and the portion of the dynamic sealing surface  26  near the exclusion edge  32  contacts the first machine component, establishing an interfacial contact footprint having an interfacial contact footprint width  38  as shown in  FIG. 1A . The interfacial contact footprint is often referred to as the “interface” or the “sealing interface.” (It is understood and rather well known in the industry that when extremely stiff aramid fabric-reinforced elastomer is used in packing construction, actual complete sealing doesn&#39;t occur with thin viscosity fluids until some level of differential pressure is applied. This is due to the fabric-induced surface texture of the dynamic sealing surface  26 . Nevertheless, the interfacial contact footprint of such seals can be, and sometimes is, referred to within the industry as the “sealing interface.”) When relative rotation occurs between the rotary seal  2  and the relatively rotatable surface  8 , the above-described interface becomes a dynamic interface, and is often referred to as the “dynamic sealing interface.” 
     The rotary seal  2  is used to retain the contained media  40 , which is from time to time maintained at an elevated pressure. For the purposes of this specification, the term “contained media” encompasses any media that the rotary seal  2  may be required to retain, such as, but not limited to, drilling fluid, other types of fluid, dirt, crushed rock, manure, dust, lubricating media, a process media, seawater, air, sand, metallic projectiles, plastic pellets, etc. For purposes of this specification, the term “fluid” has its broadest meaning, encompassing both liquids and gases. 
     In an oilfield washpipe assembly, the contained media  40  is drilling fluid, which is also known as drilling mud. The contained media  40  is typically communicated to the rotary seal  2  by a media passage  41  that is typically established by clearance between the first machine component  10  and the second machine component  18  as shown in  FIG. 1A . 
     Still referring to  FIG. 1A , a lubricant passage  42  is typically provided, and is typically established by the clearance between the first machine component  10  and an extrusion gap bore  43  of the second machine component  18 . A lubricant  44  is located within the lubricant passage  42 . Within the industry, the lubricant passage  42  is also referred to as the “extrusion gap” or the “extrusion gap clearance.” The lubricant  44  is preferably a liquid-type lubricant such as a synthetic or natural oil, or a lubricating grease. Other types of fluids, however, are also suitable in some applications. The first groove wall  12  and the extrusion gap bore  43  preferably intersect in acute angular relation and preferably form a generally circular intersection. It should be understood, however, that the intersection can be rounded (as shown) or chamfered to eliminate the sharpness of the intersection. 
     The extrusion gap bore  43  may, if desired, establish a journal bearing relationship with the relatively rotatable surface  8 , and that journal bearing relationship may be used to guide the relatively rotatable surface  8  relative to the second machine component  18 , or vice-versa. 
     The lubricant  44  is preferably fed into the lubricant passage  42  from some type of lubricant supply. Various types of lubricant supply systems are known in the art. For example, see the various types of lubricant supply systems that are shown and/or described in the publicly available Kalsi Seals Handbook, Revision 1 and the lubricant supplies shown in various U.S. Patents, such as, for example, U.S. Pat. Nos. 5,195,754, 5,279,365, 6,007,105, and 6,227,547. 
     The purposes of the rotary seal  2  of the preferred embodiment are to establish sealing engagement with the relatively rotatable surface  8  of the first machine component  10  and with the second machine component  18 , to retain the contained media  40 , and to cause a film of the lubricant  44  to migrate toward and preferably into the contained media  40  for lubrication of the rotary seal  2  and the relatively rotatable surface  8 , and for flushing purposes. 
     When the pressure of the contained media  40  is greater than the pressure of the lubricant  44  as illustrated in  FIG. 1C , the resulting differential pressure imposes force on the force receiving surface  28 , which flattens more of the dynamic sealing lip  4  against the relatively rotatable surface  8  and causes the contact footprint width  38  to increase; i.e. the footprint spreads. At some level of differential pressure between the contained media  40  and the lubricant  44 , the maximum local size of the contact footprint width  38  can equal or even slightly exceed the maximum surface width  34  of the dynamic sealing surface  26 . 
     When the pressure of the contained media  40  is greater than the pressure of the lubricant  44 , the resulting differential pressure also deforms the rotary seal  2  in a way that causes all or substantially all of the low pressure end  30  of the rotary seal  2  to be in contact with the first groove wall  12 . Thus, the rotary seal  2  is supported against the pressure of the contained media  40  by the first groove wall  12 , as taught by U.S. Pat. No. 2,394,800. Within the seal industry, the first groove wall  12  is sometimes referred to as the “lubricant-side wall,” and the second groove wall  14  is sometimes referred to as the “environment-side wall.” 
     The dynamic sealing lip  4  has at least one recess  48  of the general type disclosed in more detail below in conjunction with  FIGS. 1B and 1D . The sectional views herein, such as  FIG. 1A , are intended to be interpreted by the standard conventions of multi and sectional view orthographic drawing projection practiced in the United States and described in ANSI Y143-1975, an industry standardization document promulgated by ASME. Section 3-4.2.1 of ANSI Y14.3-1975 has been interpreted to mean that the circumferentially solid portions of the seal, such as the portion of the dynamic sealing lip  4  to the right of the recess  48 , should be crosshatched in sectional view, while the recess  48  should be drawn in outline form without crosshatch lines to avoid conveying a false impression of circumferential solidity. This ASME Section 3-4.2.1-based cross-sectional illustration technique has been employed within the sealing industry in this manner for many years. 
     The recess  48  comprises a hydrodynamic ramp  50  and a recess flank  52 . The recess flank  52  is preferably adjacent to the hydrodynamic ramp  50 , as shown. The recess flank  52  preferably forms a ledge, as shown in  FIGS. 1B and 1D . Preferably, at least part of the recess flank  52  is skewed with respect to the direction of relative rotation  46  between the rotary seal  2  and the first machine component  10 . This skewed orientation is more readily apparent in the fragmentary shaded perspective views of  FIGS. 1B and 1D , which illustrates the recess  48  in more detail. For example, as the recess flank  52  traverses the dynamic sealing surface  26  circumferentially, it may taper from a position adjacent the low pressure end  30  toward the exclusion edge  32 , as shown in  FIGS. 1B and 1D . The purpose of the hydrodynamic ramp  50  is to establish a gently converging relationship with the relatively rotatable surface  8  in the circumferential direction, in order to serve as a hydrodynamic inlet that, in response to relative rotation, hydrodynamically wedges a film of lubricant into the interface between the dynamic sealing surface  26  and the relatively rotatable surface  8  of the first machine component  10 . Where the recess  48  interrupts (i.e., cuts into) the low pressure end portion  30 , it preferably establishes at least one recess support corner  49 . 
     A principal aspect of the recess  48  is that it is exposed to and contains some of the lubricant  44 , and thereby allows at least a part of the hydrodynamic ramp  50  to be exposed to the lubricant  44 . One purpose of the recess flank  52  is to support the recess  48  against total collapse when the pressure of the contained media  40  is greater than the pressure of the lubricant  44  ( FIG. 1C ), so that the recess  48  remains exposed to and preferably filled with the lubricant  44 , so that the hydrodynamic ramp  50  can perform its hydrodynamic wedging function. Another purpose of the recess flank  52  is to create a zone of elevated interfacial contact pressure within the sealing interface. Preferably, as discussed above, at least part of that zone of elevated interfacial contact pressure is skewed with respect to the direction of relative rotation between the first machine component  10  and the rotary seal  2 , in order to divert lubricant film toward and past the exclusion edge  32 , and into the contained media  40 . 
     Referring to  FIGS. 1B and 1D , the recess  48  has a first recess end shown generally at  54 , and a second recess end shown generally at  56 . The second recess end  56  is spaced from the first recess end  54 , and the spacing is generally in the circumferential direction. As a result, the recess  48  can be said to have a circumferential length. The recess flank  52  preferably tapers off to nothing at the second recess end  56 , merging smoothly with the dynamic sealing surface  26 . The entire recess  48  preferably merges smoothly into the dynamic sealing surface  26  at the second recess end  56  as shown, having some depth at the first recess end and preferably tapering to no depth at the second recess end  56 . 
     The recess  48  preferably interrupts (i.e., cuts into) both the dynamic sealing surface  26  and the low pressure end  30 . The dynamic sealing surface  26  varies locally in its width along its circumference as a result of the recess  48 . Preferably, at least part of the recess flank  52  is skewed relative to the direction of relative rotation  46 . For example, and as disclosed above, as the recess flank  52  traverses the dynamic sealing surface  26  circumferentially, it may taper from a position adjacent the low pressure end  30  toward the exclusion edge  32 , as shown in  FIGS. 1B and 1D . Where the recess  48  interrupts (i.e., cuts into) the low pressure end  30 , it preferably establishes at least one recess support corner  49  that may, if desired, be rounded as shown. If desired, the recess flank  52  can be oriented substantially perpendicular to the ramp  50  at or adjacent the first recess end  54 . Optionally, the recess flank  52  can be oriented substantially perpendicular to the dynamic sealing surface  26  at or adjacent the first recess end  54 . 
     The first recess end  54  preferably forms a closed end, as shown. The closed end is preferred because it supports the recess  48  against collapse when differential pressure is acting on the rotary seal  2  in its installed state, thereby preserving lubricant communication to the hydrodynamic ramp  50 . Because the first recess end  54  preferably forms a closed end, the recess  48  ends abruptly, rather than passing on through and forming the alternate first recess end  54 A that is represented by a dashed line in  FIG. 1B . In the presence of differential pressure, the recess  48  is supported on three of its sides via contact between those sides and the first and second machine components  10  and  18  of  FIG. 1C . 
     At least one support shoulder  57  is incorporated along or near the side of the recess  48  that is oriented toward the exclusion edge  32 . The support shoulder  57  is preferably relatively abrupt near the first recess end  54 , and preferably merges smoothly into the dynamic sealing surface  26  at or near the second recess end  56 . If desired, the support shoulder  57  can, as shown, form the transition between the recess flank  52  and the dynamic sealing surface  26 . 
     As shown in  FIG. 1A , the rotary seal  2  may be installed into a seal gland arrangement that is similar to that shown by  FIG. 3  of U.S. Pat. No. 2,394,800. The functional reason that the recess  48  cuts into the low pressure end portion  30 B of the rotary seal  2  is to provide a lubricant passageway to feed lubricant into the recess  48  when most or all of the dynamic sealing surface  26  is forced into contact with the relatively rotatable surface by the force of the pressure of the contained media  40  acting on the at least one force receiving surface  28 . 
     As measured relative to the dynamic sealing surface  26 , the recess  48  preferably has maximum depth at or near the first recess end  54 , as shown in  FIG. 1B , and this depth gradually diminishes along the circumferential length of the recess  48 , preferably becoming zero (no depth) at the second recess end  56 . The change in depth of the recess  48  is established by the slope of the hydrodynamic ramp  50  relative to the dynamic sealing surface  26 . Preferably, the hydrodynamic ramp  50  merges smoothly into the dynamic sealing surface  26  at the second recess end  56  as shown, without producing a facet. The recess  48  preferably has a maximum recess width  58  at the second recess end  56 , and is preferably narrower at the first recess end  54 . By varying the width of the recess  48  as shown, the recess  48  has maximum support against pressure induced collapse near the first recess end  54  because the recess support corner  49 , the support shoulder  57 , and the first recess end  54  are in close proximity to one another and the recess  48  is relatively deep, as measured relative to the dynamic sealing surface  26 . 
     As previously described, the dynamic sealing surface  26  has a maximum surface width  34  and a minimum surface width  36 . The minimum surface width  36  is equal to the maximum surface width  34  minus the maximum recess width  58 . 
     In the absence of differential pressure, some of the area of the dynamic sealing surface  26  near the exclusion edge  32  contacts the relatively rotatable surface of the first machine component, establishing an interfacial contact footprint of some width (as shown, for example, in  FIG. 1A ). 
     When the force produced by high differential pressure acts on the at least one force receiving surface  28 , additional area of the dynamic sealing surface  26  is deformed into contact with the relatively rotatable surface  8 , causing more of the dynamic sealing surface  26  to contact the relatively rotatable surface  8 ; i.e., the footprint spreads. Typically, at some high enough magnitude of differential pressure, all or nearly all of the dynamic sealing surface  26  is deformed into contact with the relatively rotatable surface  8 . It is possible that even a small portion of the low pressure end  30  near the lubricant end transition  60  might also be brought into contact with the relatively rotatable surface  8  when the rotary seal  2  is exposed to severe differential pressure. 
     If desired, the maximum recess width  58  can be sized such that no portion of the hydrodynamic ramp  50  at the second recess end  56  engages the relatively rotatable surface  8  of the first machine component  10  in the absence of differential pressure. That is, the hydrodynamic ramp  50  would only begin to engage the relatively rotatable surface  8  of the first machine component  10  and perform a hydrodynamic wedging function when some level of differential pressure is applied across the rotary seal  2 . When so designed, the hydrodynamic ramp  50  does not serve any hydrodynamic wedging function until the differential pressure applied across the rotary seal  2  is sufficient to cause a portion of the hydrodynamic ramp  50  to contact the relatively rotatable surface  8  of the first machine component  10 . When so designed, the hydrodynamic wedging action provided by the hydrodynamic ramp  50  provides a progressively stronger hydrodynamic wedging action as the differential pressure increases and brings more of the dynamic sealing surface  26  and more of the width of the hydrodynamic ramp  50  into contact with the relatively rotatable surface  8  of the first machine component  10 . In other words, the hydrodynamic ramp  50  can be configured to provide more hydrodynamic interfacial lubrication when more lubrication is needed due to the higher differential pressure. 
     Alternately, if desired, the maximum recess width  58  can be designed so that at least a portion of the hydrodynamic ramp  50  at the second recess end  56  already engages the relatively rotatable surface  8  of the first machine component  10  at the time of installation, even in the absence of differential pressure. When so designed, the hydrodynamic ramp  50  serves a hydrodynamic wedging function even in the absence of differential pressure, whenever relative rotation occurs. 
     One purpose of the support shoulder  57  is to support the recess  48  when differential pressure acting across the seal  2  forces additional area of the dynamic sealing surface  26  against the relatively rotatable surface  8  of the first machine component  10 . The reason for providing such support is so that at least a portion of the recess  48  remains out of contact with the rotatable surface  8  of the first machine component  10 . It is desirable that at least a portion of the recess  48  remains “open” (not in contact with the relatively rotatable surface  8 ), and can thereby provide lubricant communication to the location where the hydrodynamic ramp  50  contacts the relatively rotatable surface  8  of the first machine component  10 . 
     The location where the hydrodynamic ramp  50  contacts the relatively rotatable surface  8  of the first machine component  10  forms a hydrodynamic inlet. When the relatively rotatable surface  8  rotates in the direction of relative rotation  46  with respect to the rotary seal  2  as shown in  FIG. 1B , the lubricant-wetted relatively rotatable surface  8  drags lubricant into the interfacial contact footprint at the location where the hydrodynamic ramp  50  contacts the relatively rotatable surface  8  of the first machine component  10 . This phenomenon is referred to as hydrodynamic wedging activity, and produces a film of oil between the dynamic sealing surface  26  and the relatively rotatable surface  8  of the first machine, component  10 . In other words, the rotary seal  2  hydroplanes on a film of oil. This hydrodynamic wedging activity is facilitated by the fact that the hydrodynamic ramp  50  has a very gradual convergence with the relatively rotatable surface  8  of the first machine component  10  in the circumferential direction. This hydrodynamic wedging activity is represented schematically by the lubricant migration arrow  84  ( FIG. 1B ), however, it is to be understood that this wedging activity occurs not just at one line of action, but occurs across much or all of the width where the hydrodynamic ramp  50  converges with the relatively rotatable surface  8 . 
     The hydroplaning activity that occurs during relative rotation minimizes or prevents the typical dry rubbing wear and high friction associated with conventional non-hydrodynamic packing elements, prolonging the useful life of the rotary seal  2  and the life of the mating relatively rotatable surface  8  of the first machine component  10 , and making higher speed, and differential pressure, practical. 
     As described previously, when the above-described relative rotation is occurring, the interfacial contact footprint becomes a dynamic interface, also known as a “dynamic sealing interface.” During relative rotation, a net hydrodynamic pumping related leakage of the lubricant  44  preferably occurs as lubricant  44  is transferred across the dynamic sealing interface and into the contained media  40 . 
     When all or nearly all of the dynamic sealing surface  26  is in contact with the relatively rotatable surface  8  of the first machine component  10 , the portion of the rotary seal  2  that experiences the most stress is at or near the lubricant end transition  60 , which is the transition between the dynamic sealing surface  26  and the low pressure end  30 . The lubricant end transition  60  often takes the form of a corner, as shown, and if desired, this corner may be slightly rounded, as shown. The material near the lubricant end transition  60  experiences conditions that in the prior art cause significant wear. The hydrodynamic ramp  50 , being circumferentially in line with the dynamic interface near the lubricant end transition  60 , feeds lubricant  44  directly into that critical location. This causes that critical location (and the rotary seal  2  as a whole) to run much cooler than prior art packing. This cooler operation increases the extrusion resistance of the rotary seal  2  at the critical location near the lubricant end transition  60  by increasing the modulus of elasticity of the rotary seal  2  near the lubricant end transition  60  (and near the lubricant passage  42  of  FIG. 1A ). The film of lubricant  44  within the dynamic interface dramatically reduces wear of the dynamic sealing surface  26 , compared to prior art packing, especially in the critical location near the lubricant end transition  60 . 
     Along at least part of the location where the support shoulder  57  contacts the relatively rotatable surface  8  of the first machine component  10 , a zone of elevated interfacial contact pressure occurs within the interfacial contact footprint. Preferably, at least part of this zone of interfacial contact pressure is skewed with respect to the direction of relative rotation  46 , and therefore during relative rotation, the zone of interfacial contact pressure diverts part of the film of lubricant  44  toward and past the exclusion edge  32 , and into the contained media  40 . The skewed zone of interfacial contact pressure created by the support shoulder  57  serves to flush contaminant matter from the dynamic interface, and thereby helps to minimize wear of the dynamic sealing surface  26 . 
     Referring now to  FIG. 1C , the rotary seal  2  is illustrated in its installed condition, in the presence of differential pressure that is the result of the pressure of the contained media  40  being greater than the pressure of the lubricant  44 . The pressure of the contained media  40  forces much or all of the low pressure end  30  of the rotary seal  2  into supporting contact with the first groove wall  12  and forces the static sealing rim  6  into firmer contact with the second machine component  18 . Thus, the rotary seal  2  is supported against the pressure of the contained media  40  by the first groove wall  12 , and preferably the low pressure end portion  30 B is supported by the first wall part  12 B. 
     The pressure of the contained media  40  also imposes force on the at least one force receiving surface  28 , which causes the contact footprint width to increase; i.e., the footprint spreads. It also causes the sealing contact pressure between the dynamic sealing surface  26  and the relatively rotatable surface  8  to increase. Because of the recess  48 , the contact footprint width  38  is smaller at some locations than others. In  FIG. 1C ,  38 A represents a location of smaller footprint width, and  38 B represents a location of comparatively greater footprint width. Thus, the footprint has a wavy lubricant side edge. 
     The recess flank  52  serves to prop at least part of the recess  48  open, so that not all of the hydrodynamic ramp  50  is in contact with the relatively rotatable surface  8 , and so that at least some portion of the recess  48  remains “open” (i.e., not in contact with the relatively rotatable surface  8 ). The recess support corner  49  also preferably helps to keep the recess  48  open. The first recess end  54  ( FIGS. 1B and 1D ) also preferably helps to keep the recess  48  open. It is to be understood that as differential pressure increases, the recess support corner  49  and part of the left hand side of the hydrodynamic ramp  50  near the lubricant passage  42  might be deformed into contact with the relatively rotatable surface  8 . Whether the recess support corner  49  receives its support from the first groove wall  12  or from the relatively rotatable surface  8 , the support helps to keep at least the portion of the recess  48  near the recess flank  52  open. This is true even if part of the left hand side of the hydrodynamic ramp  50  near the lubricant passage  42  might be deformed into contact with the relatively rotatable surface  8 , because the open part of the recess  48  extends more or less circumferentially back to the lubricant passage  42  and provides communication for the lubricant  44  that is being hydrodynamically wedged into the dynamic sealing interface at the location where the hydrodynamic ramp  50  converges with the relatively rotatable surface  8  in the generally circumferential direction. 
     To reiterate, if part of the left-hand side of the recess  48  is collapsed against the relatively rotatable surface  8 , the open part of the recess  48  is still exposed to the extrusion gap bore  43  and the lubricant  44  and the open part of the recess  48  can serve as an open passage (i.e., a communication path) for supplying the lubricant  44  to the hydrodynamic inlet that is formed by the hydrodynamic ramp  50  converging generally circumferentially into contact with the relatively rotatable surface  8 . Since the inlet consumes lubricant  44  and pumps a film of lubricant  44  toward and past the exclusion edge  32 , it is critical that at least part of the recess  48  be propped open and can thereby perform its intended lubricant passageway function. Some features of this invention, such as the recess flank  52 , the recess support corner  49 , and the first recess end  54 , their proximity to each other, and the shape of the recess  48 , cooperate together with the first and second machine components  10  and  18  to allow the recess  48  to remain open despite the actions of high differential pressure, and to perform its intended functions. 
     With regard to  FIG. 1C , it should be appreciated that even if the pressure of the contained media  40  causes the left hand part of the hydrodynamic ramp  50  to contact the relatively rotatable surface  8 , the right hand part of the hydrodynamic ramp  50  will remain out of contact with the relatively rotatable surface  8  as a result of the propping effect of the recess flank  52 . Thus, at least a portion of the recess  48  remains “open” near and along the recess flank  52 , and opens into the lubricant passage  42  created by the clearance between the extrusion gap bore  43  of the first machine component  10  and the second machine component  18 , and serves as an open communication passage for the lubricant  44 , allowing the lubricant  44  to reach the hydrodynamic inlet location that is formed by the hydrodynamic ramp  50  converging into contact with the relatively rotatable surface  8  in the generally circumferential direction. 
     Because the pressure of the contained media  40  is greater than the pressure of the lubricant  44 , the contained media  40  produces a force on the force receiving surface  28  that causes the interfacial contact pressure near the recess flank  52  to be locally elevated. Since at least part of the recess flank  52  is preferably skewed relative to the direction of relative rotation between the relatively rotatable surface  8  and the dynamic sealing lip  4 , at least part of the elevated zone of interfacial contact pressure near the recess flank  52  is also preferably skewed relative to the direction of relative rotation  46 , thereby encouraging the lubricant film within the sealing interface to migrate toward and past the exclusion edge  32  in response to relative rotation between the relatively rotatable surface  8  and the dynamic sealing lip  4 . The direction of relative rotation  46  is normal to the plane of the cross-section; in other words it is normal to the  FIG. 1A  image. 
     A principal advantage of the preferred embodiment of the present invention is that the recess flank  52 , the recess support corner  49 , (and, if desired, the wall-like configuration of the first recess end  54  illustrated in  FIGS. 1B and 1D ) supports the hydrodynamic ramp  50  from being flattened completely against the relatively rotatable surface  8 , thereby preserving an efficient, gently converging hydrodynamic inlet established between the hydrodynamic ramp  50  and the relatively rotatable surface  8  for maintaining efficient hydrodynamic film lubrication of the dynamic sealing surface  26 . This makes the rotary seal  2  operate much cooler than comparable non-hydrodynamic packing. Therefore, the rotary seal  2  retains a relatively high modulus of elasticity near the lubricant passage  42  for optimum extrusion resistance, and has less wear compared to conventional non-hydrodynamic packing. 
     
       FIG. 2 
     
     Referring now to  FIG. 2 , an alternate embodiment of the ring-like, generally circular rotary seal of the present invention is illustrated generally at  2  in its installed condition, in the absence of differential pressure. It is to be understood that features throughout this specification that are represented by like numbers have the same function in the various embodiments of the present invention. The second groove wall  14 , peripheral wall  16 , contact footprint width  38 , contained media  40 , media passage  41 , lubricant passage  42 , extrusion gap bore  43 , lubricant  44 , recess  48 , recess support corner  49 , hydrodynamic ramp  50 , recess flank  52 , and lubricant end transition  60  are labeled in  FIG. 2  for orientation purposes. 
     In the embodiment of  FIG. 2 , the rotary seal  2  is a ring that includes a dynamic sealing lip  4  and a static sealing rim  6  that are preferably integral features of the rotary seal  2 . The dynamic sealing lip  4  is adapted for sealing against a relatively rotatable surface  8  of a first machine component  10 . 
     The static sealing rim  6  is adapted for sealing with respect to the second machine component  18  by establishing sealing contact pressure with respect to the second machine component  18  achieved by having the static sealing rim  6  in compressed contacting relationship with the second machine component  18 . The compressed contacting relationship is established by axial clamping of the static sealing rim  6  between the first spacer ring  20  and the second spacer ring  22  of the second machine component  18 . 
     The dynamic sealing lip  4  incorporates a dynamic sealing surface  26  for sealing contact with the relatively rotatable surface  8 , includes at least one force receiving surface  28 , and preferably has an exclusion edge  32  that is generally circular. 
     The low pressure end  30  of the rotary seal  2  generally faces, and is supported against differential pressure, by the first groove wall  12 . The first groove wall  12  preferably comprises first wall part  12 A and first wall part  12 B, and the low pressure end  30  of the rotary seal  2  preferably comprises low pressure end portion  30 A and low pressure end portion  30 B. 
     When installed, a portion of the dynamic sealing surface  26  contacts the first machine component  10 , thereby establishing a contact footprint width  38  therewith. 
     
       FIG. 3 
     
     Referring now to  FIG. 3 , an alternate embodiment of the ring-like, generally circular rotary seal of the present invention is illustrated generally at  2  in its installed condition, in the absence of differential pressure. 
     In the description of the seal of the embodiment shown in  FIG. 1A , it was disclosed that the seal of the present invention may be composed of any suitable sealing material, including combinations of materials that are joined together.  FIG. 3  illustrates one way of using more than one material in the construction of the rotary seal  2 . In the present embodiment, the rotary seal  2  is a ring that comprises a first material  64  and a second material  66  that are joined together by any appropriate method. If desired, the second material  66  can have a higher modulus of elasticity than the first material  64 . For example, the second material  66  could be a plastic material with appropriate sealing and dynamic running properties, such as (but not limited to) reinforced polytetrafluoroethylene (“PTFE”) based plastic or a mixture of polyetheretherketone and polytetrafluoroethylene, and the first material  64  could be an elastomer compound, with or without fabric reinforcement. An advantage in using a higher modulus material for the second material  66  is that it makes the recess  48  more resistant to differential pressure-induced collapse. 
     
       FIG. 4 
     
       FIG. 4  illustrates another way of using more than one material in the construction of the rotary seal  2 . In this embodiment, the seal comprises a first material  64  and a second material  66  that are joined together by any appropriate method. If desired, and similar to the embodiment of  FIG. 3 , the second material  66  can have a higher modulus of elasticity than the modulus of elasticity of the first material  64  to make the recess  48  more resistant to differential pressure-induced collapse. In the rotary seal embodiment of  FIG. 4 , the second material  66  is shorter than it was in the embodiment of  FIG. 3 , making it easier for pressure acting on the at least one force receiving surface  28  to deform more of the dynamic sealing surface  26  into contact with the relatively rotatable surface  8 . If desired, a combination of the first material  64  and second material  66  may form part of the dynamic sealing surface  26 . 
     If desired, the second material  66  need not extend to the end transition  68  between the low pressure end portion  30 A and the low pressure end portion  30 B, thus making it easier for the pressure of the contained media  40  to force the surface of the second material  66  into contact with the relatively rotatable surface  8  (without flattening the recess  48  against the relatively rotatable surface  8 ). As described previously, a lower modulus portion  70  of the static sealing rim  6  can be incorporated if desired, as is commonly done with washpipe packings. 
     
       FIG. 5 
     
       FIG. 5  shows that if desired, an energizer element  72  can be used to help to energize the dynamic sealing lip  4  of the rotary seal  2  against the relatively rotatable surface  8 . The energizer element  72  may also, if desired, load the static sealing rim  6  against peripheral wall  16 . Figures herein that do not illustrate an energizer element can be thought of as simplifications of the rotary seals that are shown to have an energizer element. 
     The energizer element  72  can take any of a number of suitable forms known in the art including, but not limited to, elastomeric rings and various forms of springs, without departing from the scope or spirit of the invention. If desired, the energizer element  72  can be located by an annular recess of any suitable form, and preferably at least part of the annular recess is defined by a force receiving surface  28 . Differential pressure acting on the energizer element  72  applies force to the annular recess, including the portion of the force receiving surface  28  that is contacted by the energizer element  72 . 
       FIG. 5  also shows that, if desired, the rotary seal  2  of the present invention may be used advantageously in an assembly that also employs a non-chevron-type prior art hydrodynamic seal  74  of the type that is configured for having high differential pressure acting from the lubricant side thereof, such as one of the seal types disclosed in commonly assigned U.S. Pat. Nos. 5,230,520, 5,738,358, 5,873,576, 6,036,192, 6,109,618, 6,120,036, 6,315,302, 6,382,634, 6,494,462, 6,685,194, 6,767,016, 7,052,020, or 7,562,878, or such as one of the seal types disclosed in commonly assigned U.S. Patent Appln. Pub. Nos. 2006/0214379, 2007/0013143, 2007/0205563, or 2009/0001671. 
     The advantage of using such a prior art hydrodynamic seal  74  in conjunction with the rotary seal  2  of the present invention is that the pressure of the lubricant  44  can be maintained at a value that is greater than that of a low pressure environment  76 . Although the low pressure environment  76  can be any type of environment, in an oil well drilling washpipe assembly the low pressure environment  76  is typically the atmosphere, and the objective of the assembly is to prevent escape of the contained media  40  into the low pressure environment  76 . If desired, the lubricant  44  can be supplied via a lubricant port  78 . In other words, the rotary seal  2  of the present invention can be used in the pressure staged manner first taught in the commonly assigned U.S. Pat. No. 6,007,105 entitled “Swivel Seal Assembly,” which teaches that the rotary seals of that pressure-staged invention may take any suitable form, such as hydrodynamic-type or chevron-type seals, and also discloses that the rotary seals may conveniently take the form of hydrodynamic seals such as those patented and sold by Kalsi Engineering, Inc. or any one of a number of rotary shaft seals that are suitable for the purposes intended, such as reinforced elastomeric chevron-type seals that are conventionally used in many swivels. 
     If desired, the lubricant  44  may be supplied through the lubricant port  78  by any suitable lubricant supply system  80 , such as, but not limited to, those described in commonly assigned U.S. Pat. Nos. 6,007,105 and 6,227,547, and/or those shown in the Kalsi Seals Handbook, Revision 1. If desired, the lubricant supply system  80  can be protected against contamination (i.e., contamination due to exposure to the contained media  40  in the event of failure of the rotary seal  2 ) by using a check valve  82 . Thermal expansion of the lubricant  44  is not an issue, because the dynamic sealing lip  4  of the rotary seal  2  will lift and vent any significant lubricant pressure into the contained media  40 . 
     As shown, if desired, the first spacer ring  20  may form a housing that extends over the second spacer ring  22 . A unique feature of  FIG. 5  is the pairing of two different kinds of hydrodynamic seals, one (prior art hydrodynamic seal  74 ) configured for having the pressure of the lubricant  44  greater than that of the low pressure environment  76 , and one (rotary seal  2 ) configured for having the pressure of the contained media  40  greater than that of the lubricant  44 . The prior art hydrodynamic seal  74  not only retains a volume of the lubricant  44  for lubrication of the rotary seal  2 , it also shares part of the differential pressure that exists between the contained media  40  and the low pressure environment  76 . This allows the assembly to handle much higher differential pressure than it could if the seal that retained the lubricant for rotary seal  2  were some non-hydrodynamic seal. At the same time, the rotary seal  2  is immune to the pressure staging-related pressure lag issues that are described in IADC/SPE Paper 59107. 
     
       FIG. 6 
     
       FIG. 6  shows that, if desired, an energizer element  72  in the form of a spring can be used to help to energize the dynamic sealing lip  4  of the rotary seal  2  against the relatively rotatable surface  8 . The energizer element  72  may also, if desired, load the static sealing rim  6  against the peripheral wall  16 . Figures herein that do not illustrate an energizer element can be thought of as simplifications of the rotary seals that are shown to have an energizer element. 
       FIG. 6  shows an arrangement that is appropriate for the differential pressure issues that plague some types of downhole drilling tools. The inboard seal is a non-chevron-type prior art hydrodynamic seal  74  of the type that is not configured for having high differential pressure acting from the drilling fluid side thereof but otherwise works very well in downhole drilling applications. Some examples of such seal types are those that are disclosed in commonly assigned U.S. Pat. Nos. 5,230,520, 5,738,358, 5,873,576, 6,036,192, 6,109,618, 6,120,036, 6,315,302, 6,382,634, 6,494,462, 6,685,194, 6,767,016, 7,052,020, or 7,562,878, and the seal types disclosed in commonly assigned U.S. Patent Appln. Pub. Nos. 2006/0214379, 2007/0013143, 2007/0205563, and 2009/0001671. 
     The outboard seal is the rotary seal  2  of the present invention. The overall objective of the assembly is to partition a contained media  40  from a lubricant  44 A within the assembly, where the pressure of the contained media  40  can occasionally be much greater than the pressure of the lubricant  44 A, but for the most part the pressure of the lubricant  44 A is slightly greater than (or alternately, about equal to) that of the contained media  40 . In a downhole drilling tool, the contained media  40  is drilling fluid (i.e., “drilling mud”), and the lubricant  44 A is typically used by the drilling tool for various purposes, such as lubricating bearings, operating hydraulic motors and hydraulic cylinders, etc. It is necessary to contain the contained media  40  so that it does not enter the drilling tool and contaminate the inner workings of the tool. 
     In this particular type of assembly, the lubricant  44  would typically be called a barrier lubricant, and the outboard seal, the rotary seal  2 , would typically be called a “barrier seal.” This “barrier seal” nomenclature is an understatement as it concerns the present invention because the rotary seal  2  fulfills much more than the traditional barrier seal function. 
     If desired, the initial fill of the lubricant  44  may be supplied through a lubricant port  78 . If desired, the lubricant port  78  may be connected to any suitable lubricant supply system  80  while the assembly is in service, or alternately the lubricant port  78  can be plugged while the assembly is in service. 
     The prior art hydrodynamic seal  74  retains a volume of the lubricant  44 A and its hydrodynamic pumping-related leakage enters the lubricant  44  through the lubricant passage  42 . Since the pressure of the lubricant  44 A is typically greater than that of the contained media  40 , the prior art hydrodynamic seal  74  is used to contain the lubricant  44 A, in view of the fact that the rotary seal  2  of the present invention cannot handle differential pressure acting from that direction. Also, circumstances are possible where the pressure of the lubricant  44 A may temporarily be significantly higher than that of the contained media  40 , and the prior art hydrodynamic seal  74  is configured to deal with such circumstances. 
     When the pressure of the contained media  40  is temporarily significantly greater than that of the lubricant  44 , the rotary seal  2  deforms in the manner described in conjunction with previous figures herein, so that it can operate in a hydrodynamic interfacial lubrication regime. 
     The prior art hydrodynamic seal  74  is not well suited to service where the pressure of the contained media  40  is significantly greater than that of the lubricant, and the rotary seal  2  is not well suited to service where the pressure of the lubricant is greater than that of the contained media  40 . By pairing the two types of seals in the manner illustrated in  FIG. 6 , the strengths of each seal type make up for the weaknesses of the other, allowing longer drilling tool life in harsh downhole drilling conditions. 
     It can be appreciated that the various constructions of rotary seal  2  that are illustrated herein can be used in the assemblies of  FIGS. 5 and 6 , without departing from the spirit or scope of the invention. It can also be appreciated that if desired, the second machine component  18  could be made of one piece, instead of being made from two separate pieces. 
     
       FIG. 7 
     
       FIG. 7  shows that, if desired, the recess  48  of the rotary seal  2  can also comprise one or more support ribs  88  that preferably incorporate a hydrodynamic leading edge  90 . The support ribs  88  can be generally circumferentially oriented, as shown, and serve to provide additional support against the total differential pressure-induced collapse of the recess  48 . In other words, the support ribs  88  help to ensure that at least a portion of the hydrodynamic ramp  50  is not deformed into contact with the mating relatively rotatable surface, thereby preserving lubricant communication and the hydrodynamic wedging function of the hydrodynamic ramp  50 . Figures herein that do not illustrate one or more support ribs  88  can be thought of as representing simplifications of the rotary seals that are shown to have one or more support ribs  88 . 
     If desired, the novel recess  48  described in conjunction with the various embodiments of the present invention may be configured for combination with the basic prior art seal cross-sectional shapes that are shown in U.S. Pat. No. 6,334,619, in order to eliminate the wavy seal lubricant end and wavy backup ring that are described in U.S. Pat. No. 6,334,619. 
     In view of the foregoing it is evident that the present invention is one that is well adapted to attain all of the features hereinabove set forth, together with other objects and features which are inherent in the apparatus disclosed herein. Even though several specific hydrodynamic rotary seal and seal gland geometries are disclosed in detail herein, many other geometrical variations employing the basic principles and teachings of this invention are possible. 
     The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape, and materials, as well as in the details of the construction shown and described, may be made without departing from the spirit of the invention. The present embodiments are, therefore, to be considered as merely illustrative and not restrictive, the scope of the invention being indicated by the claims rather than the foregoing description, and all changes which come within the meaning and range of equivalence of the claims are therefore intended to be embraced therein.

Technology Classification (CPC): 4