Abstract:
The rotary face seal with magnet loading replaces known spring mechanisms with magnetic technology that provides a consistent load with minimal variation, which is not affected by natural frequency and material fatigue due to cyclic loading. This improves seal performance and service life by eliminating the issues that compromise the effectiveness of conventional spring mechanisms. The repelling pusher magnetic technology is advantageous because it replaces the spring mechanism within a self-contained stationary cartridge with a pusher type magnetic assembly configuration that enable exact drop-in replacement of existing seal configurations.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This patent application claims priority to earlier filed U.S. Provisional Application Ser. No. 62/362,348, filed Jul. 14, 2016 the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The invention relates generally to mechanical rotary face seals. Such mechanical rotary face seals are typically used to seal media (gas or fluid) between the shaft and the housing where one is stationary and the other is rotating. These seals are used in the aerospace industry, commercial industry, nuclear industry, and other high reliability industries, such as, test equipment and race car engines and transmissions or the like. 
         [0003]    There are a number of problems and concerns typically associated with known mechanical rotary face seals. Standard mechanical rotary face seals use a spring mechanism for the mechanical load that provides positive contact against the rotary mating surface that is either a separate ring attached to shaft, shaft flange or end face, or a bearing inner race. The loading of the spring mechanism can have a large variation caused by operating range (stroke) length, compromised when it&#39;s natural frequency is reached during operation from shock and vibration, and load reduction (weakening) due to material fatigue under cyclic loading and temperature extremes. 
         [0004]    There have been a number of attempts in the prior art to address these common problems. 
         [0005]    For example, U.S. Pat. No. 3,708,177 for Magnetic Seal for a Rotary Shaft and Magnet Therefor addresses the well-known eddy current issue but it is unknown if the design was commercially feasible. U.S. Pat. No. 4,795,168 for a Magnetic Seal Assembly does not address the eddy current issue because the magnet inserts rotate. U.S. Pat. No. 5,078,411 for Variable Magnetic Rotary Seal does not address the eddy current issue because the magnet inserts rotate. U.S. Pat. No. 5,730,447 for Self-Aligning Magnetic Rotary Seal also does not address the eddy current issue because the magnet inserts rotate. U.S. Pat. No. 6,805,358 for Magnetic Seal also does not address the eddy current issue because either the magnet inserts rotate or the magnetically attractive member is exposed to continuously changing north and south poles during rotation. 
         [0006]      FIGS. 1 and 2  show an example of such a prior art rotary face seal  10  in detail. It includes an anti-rotation design that uses two (2) tangs  12  on the seal case  16  that engage slots  14  in the cup  18  which permits fluid movement in this area. It has a removable “take apart” cartridge design that facilitates repair, replacement and inspection of internal parts. It has a solid outside diameter cup option with internal milled tangs  12  and seal case slots  14 .  FIG. 1  shows an embodiment with outward radial tangs  24  on the seal case  16  that engages slots in the cup  18 . As a further variation,  FIG. 2  shows a solid outer diameter option with internal radial tangs  26  in the cup  18  that engages the slots in the seal case  16 . 
         [0007]    High pressure, low pressure and reverse pressure capability is achieved within the same cartridge by adjusting the diameters of the seal ring  20 . Since it does not employ magnets, there is unrestricted selection of materials for construction. However, the slotted OD design is not practical for all applications with the majority using the internal milled tangs  12  with slots  14  in the seal case  16 . There is spring load variation due to operating range and the spring load decreases as the seal ring  20  wears compromising re-seating. A wave spring  22  resides between the seal case  16  and the cup to spring-bias them apart. Also, the natural frequency of wave spring  22  is unknown and could cause loading issues under shock and vibration conditions. Moreover, the rotary mating surface which bears against the seal ring  20  mating surface  20   a  is not always part of the seal design, namely, the bearing inner race face, integral with the shaft (not shown) and the mating ring (not shown) obtained from multiple suppliers. 
         [0008]    These solutions are not enough. In view of the foregoing, there is a demand for a rotary face seal that combines the best features of a magnet rotary seal with a non-magnetic seal to avoid the shortcomings associated with prior art rotary face seals. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention preserves the advantages of prior art rotary face seals. In addition, it provides new advantages not found in currently available rotary face seals and overcomes many disadvantages of such currently available rotary face seals. 
         [0010]    The invention is generally directed to the novel and unique rotary face seal that has magnetic repelling loading. The rotary face seal with magnetic loading of the present invention replaces a conventional mechanical spring mechanism with opposing/repelling magnets where the magnetic technology provides a spring-like biasing effect to provide a consistent load with minimal variation, which is not affected by natural frequency and material fatigue due to cyclic loading. This improves seal performance and service life by eliminating the issues that compromise the effectiveness of the spring mechanism. The magnetic technology replaces the mechanical spring mechanism preferably within a stationary cartridge with a “pusher” type magnetic assembly design. As a result, such a stationary cartridge of the present invention is an exact exchange or “drop-in” solution to replace known seal that use mechanical wave springs. 
         [0011]    It is therefore an object of the present invention to provide improved rotary face seal that overcomes the shortcomings associated with the prior art and provides vastly improved performance compared to such prior art designs. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The novel features which are characteristic of the present invention are set forth in the appended claims. However, the invention&#39;s preferred embodiments, together with further objects and attendant advantages, will be best understood by reference to the following detailed description taken in connection with the accompanying drawings in which: 
           [0013]      FIG. 1  is a cross-sectional view of a first known prior art rotary seal construction that uses conventional wave springs; 
           [0014]      FIG. 2  is a cross-sectional view of a second known prior art rotary seal construction that uses conventional wave springs; 
           [0015]      FIG. 3  is a cross-sectional view of a first embodiment of the invention; 
           [0016]      FIG. 4  is a cross-sectional view of a second embodiment of the invention with hydrodynamic lift-off grooves in the seal face of the rotating mating ring; and 
           [0017]      FIG. 5  is an end view of the seal face of the rotating mating ring showing the hydrodynamic lift-off grooves. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0018]    The rotary face seal  100  of the present invention with magnet repelling loading replaces the mechanical spring mechanism with magnetic technology to provide a consistent load with minimal variation, which is not affected by natural frequency and material fatigue due to cyclic loading. This will improve seal performance and service life by eliminating the issues that compromise the effectiveness of the spring mechanism. The present invention, with its magnetic “spring” technology, replaces the mechanical spring mechanism of the prior art of  FIGS. 1 and 2  with the stationary cartridge of the present invention with a pusher type magnetic assembly design that results with the stationary cartridges being an exact exchange. 
         [0019]    Referring to  FIG. 3 , of the rotary face seal  100  of the present invention is shown to include a basic cartridge rotary face seal that is comprised of a cup  102 , seal case  104  with inserted seal ring  106  that fits into the cup  102  with an anti-rotation feature that includes a retaining ring  108  that resides in a groove  110  in the cup  102 . The cup  102 , in turn, resides in a stationary housing  120  to complete the drop-in cartridge configuration. This anti-rotation structure prevents the seal case  104  from rotation when the seal ring  106  contacts a rotating mating face of a rotating mating ring  112  that is rotates with shaft  114  due to being held in place by O-ring  116  in seat  112   c.  Such rotation is prevented as well relative to the shaft end face  114   a  or integral flange face, bearing inner face (not shown). 
         [0020]    Any type of configuration may be used for attaching the rotating mating ring  112  to the shaft  114 , such as the use of O-rings, as shown. In addition, there may be a positive drive with an internal O-ring as secondary seal engagement the shaft with either radial of axial tangs that engage slots in the shaft. Or, there may be the reverse engagement with slots in the mating ring engaging tangs on the shaft. Also, there may be a positive drive with an internal O-ring as secondary seal engagement with the shaft with either radial of axial pins that engage the shaft. Further, there may be a reverse engagement with pins in the shaft engaging with the mating ring. Further, there may be a positive drive with an internal O-ring as secondary seal by using an axial clamping sleeve or a positive drive without an internal O-ring as secondary seal by using an axial clamping sleeve. 
         [0021]    Also, an internal O-ring  118  resides in the cup  102  which interfaces with the seal case  104  to provide a secondary seal while allowing axial movement of the seal case  104  within the cup  102  along the shaft axis  114   b.  The seal case  104  is preferably a metal alloy, as is well-known in the art. Known  0 -ring designs and materials may be used, which are known in the art for the purposes indicated herein. For example, various elastomers may be used, which may or may not be pre-swollen. An internal retaining ring  108  in the cup  102  that prevents the seal case  104  from becoming disengaged from the cup  102 . 
         [0022]    Preferably, a pair of magnets  120   a  and  120   b  are provided in the cavity defined by the space between the cup  102  and the seal case  104 . The pair of magnets are a magnetic pusher assembly that is in the cup  102  and contacts the adjacent flange  104   a  of the seal case  104  when the seal ring  106  is mated to the mating face  112   a  of the rotating mating ring  112  while carrying out operation of the seal with a range of motion indicated as B in  FIG. 3 . The magnets  120   a  and  120   b  are preferably a pair of magnets that repel each other. The magnets  120   a  and  120  are each preferably of a unitary annular shape to reside within the annular-shaped cavity defined between the cup  102  and seal case  104  discussed herein. In the alternative, the opposing/repelling magnets may each be made of a number of separate magnet members to suit the application at hand to provide the designed magnetic field and circuit. The repelling magnet force may also be a drop-in repelling magnetic cartridge-like solution offered by the Polymagnet company under the mark POLYMAGNET, for example as an alternative, which can maintain the seal case  104  in the cup  102  thereby eliminating the internal retaining ring and provide the mechanical load in the spring when the seal case  104  is mated against the rotary mating face  112   a  during operation. Further, the force, travel and the repelling profile of the magnets may be further modified to suit the application at hand. The seal ring  106  may be any material suitable for the application at hand, such as carbon graphite, and the like. The magnets  120   a  and  120  provide an outwardly directed spring-biasing, as shown by arrows A in  FIG. 3 . 
         [0023]    Therefore, the rotary face seal of the present invention eliminates the risks associated with prior art designs. 
         [0024]    Turning now to  FIGS. 4 and 5 , an alternative embodiment  200  of the first embodiment  100  of the present invention of  FIG. 3  is shown. The alternative embodiment  200  is similar to the first embodiment except that the rotating mating ring  212  has a bearing surface  212   a  which incorporates lift-off technology using hydrodynamic grooves  250 , as can be best seen in  FIG. 5 , which is an end view of the bearing face  212   a  of the rotating mating ring  212 . It should be noted that the configuration of the grooves  250  is shown by way of example, and it should be understood that any type, configuration and array of grooves  250  may be used in connection with the alternative embodiment  200  to provide the benefits of such hydrodynamic lift-off grooves. 
         [0025]    The alternative embodiment  200  has all of the same other components as the first embodiment, such as a cup  202 , seal case  204 , with seal ring  206  that is pushed outwardly by magnets  220   a,    220   b.  The seal ring  206  bears against the rotating mating ring  212 . The entire seal assembly  200  receives a shaft  214  to be sealed. 
         [0026]    It would be appreciated by those skilled in the art that various changes and modifications can be made to the illustrated embodiments without departing from the spirit of the present invention. All such modifications and changes are intended to be covered by the appended claims.