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You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND 
     Formation degradation, such as pavement milling, mining, drilling and/or excavating, may be performed using degradation assemblies. In normal use, these assemb lies and auxiliary equipment are subjected to high impact, heat, abrasion, and other environmental factors that wear their mechanical components. Many efforts have been made to improve the service life of these assemblies, including efforts to optimize the method of attachment to the driving mechanism. 
     One such method is disclosed in U.S. Pat. No. 5,261,499 to Grubb, which is herein incorporated by reference for all that it contains. Grubb discloses a two-piece rotatable cutting bit which comprises a shank and a nose. The shank has an axially forwardly projecting protrusion which carries a resilient spring clip. The protrusion and spring clip are received within a recess in the nose to rotatably attach the nose to the shank. 
     Another such method is disclosed in U.S. Patent Publication No. 2008/0309146 to Hall, et al., which is herein incorporated by reference for all that it discloses. It discloses, in one aspect, a degradation assembly comprising a shank with a forward end and a rearward end, the rearward end being adapted for attachment to a driving mechanism, with a shield rotatably attached to the forward end of the shank. The shield comprises an underside adapted for rotatable attachment to the shank and an impact tip disposed on an end opposing the underside. A seal is disposed intermediate the shield and the shank. 
     BRIEF SUMMARY 
     In one aspect of the present invention, a degradation assembly comprises a pressing seal element and a pressurized rigid element disposed intermediate a rotating component and a stationary component. The stationary component may be attached to a driving mechanism through a block. The rotating component may comprise an impact tip bonded to an end opposing the stationary component. The seal element may energize the rigid element against one of the components to form a slidable seal capable of holding lubricant within the assembly and keeping debris out while still rotating. 
     The rotating element may comprise a shield with a recess opposite the impact element. The recess of the shield may rotatably connect to the first end of a shank. A second end may be retained in a holder attached to a driving mechanism. In another embodiment, the shield and the shank may comprise a single component and rotate with respect to the holder. A pressing seal element may be disposed intermediate the rotating component and the stationary component, and a pressurized rigid element may be disposed adjacent to the seal element. 
     The rigid element may comprise a concave and/or textured surface facing the seal element and a flat, convex, polished, and/or wear resistant surface opposing the seal element. 
     The seal element may comprise an O-ring, a rubber washer, or a compression spring. The seal element may comprise a textured outer surface. The assembly may comprise a wiper or a ring disposed axially around the assembly, adjacent to both the shield and the shank. The assembly may comprise a lubricant chamber. The assembly may comprise a spring clip. The shank may comprise a ledge. The assembly may comprise a pick. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional diagram of an embodiment of a pavement milling machine. 
         FIG. 2  is a cross-sectional diagram of an embodiment of a degradation assembly. 
         FIG. 3  is a cross-sectional diagram of another embodiment of a degradation assembly. 
         FIG. 4  is a cross-sectional diagram of another embodiment of a degradation assembly. 
         FIG. 5  is a cross-sectional diagram of another embodiment of a degradation assembly. 
         FIG. 6  is a cross-sectional diagram of an embodiment of a degradation assembly retained in a holder and further retained in a block. 
         FIG. 7   a  is a perspective diagram of an embodiment of a rigid element. 
         FIG. 7   b  is a perspective diagram of an embodiment of a protective ring. 
         FIG. 7   c  is a cross-sectional diagram of an embodiment of a protective ring with a wiper. 
         FIG. 7   d  is a perspective diagram of an embodiment of an O-ring. 
         FIG. 7   e  is a perspective diagram of an embodiment of a rubber washer. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a cross-sectional diagram of a pavement milling machine  103  that shows a plurality of pick degradation assemblies  101  attached to a driving mechanism  102 , such as a rotatable drum, attached to the underside of the pavement milling machine  103 . The pavement milling machine  103  may be an asphalt planer used to degrade man-made formations  104  such as pavement, asphalt, concrete, tarmac, blacktop or other manmade formations known in the art prior to placement of a new layer of the formation  104 . The formation  104  may also comprise naturally occurring material such as stone, dirt, minerals, rubble, debris or the like. The pick degradation assemblies  101  may be attached to the rotatable drum, bringing the pick degradation assemblies  101  into engagement with the formation  104 . A holder  105 , such as a block or other type holder, is attached to the driving mechanism  102  by means of a weld, bolt(s) or other sturdy fastening means known in the art. The pick degradation assembly  101  may be inserted into the holder  105 . The holder  105  may hold the pick degradation assembly  101  at an angle offset from the direction of rotation, such that the pick degradation assembly engages the formation  104  at a preferential angle. While an embodiment of a pavement milling machine  103  was used in the above example, it should be understood that pick degradation assemblies  101  disclosed herein have a variety of uses and implementations that may not be specifically discussed within this disclosure. 
     It is believed that while in use, a nonrotatable pick degradation assembly  101  may receive uneven wear on a single side because the same side is continuously engaging a formation  104 . This uneven wear may shorten the life of the pick degradation assembly  101 . It is further believed that the life of the assembly  101  may be lengthened by rotating the assembly such that different sides of the assembly  101  are engaging the formation  104  throughout the life of the pick degradation assembly  101 . 
     Referring now to  FIG. 2 , a cross-sectional view of an embodiment of a pick degradation assembly  101 A is depicted. The pick degradation assembly  101 A may comprise a shield  202 A and a shank  201 A. The shield  202 A may comprise a recess  215 A. The recess  215 A may be a blind recess  215 A that travels into the shield  202 A without passing out the other side. The recess  215 A may be rotatably connected to the shank  201 A. A spring clip  208 A within the recess  215 A may secure the shield  202 A over the shank  201 A while still allowing the shield  202 A to rotate relative to the shank  201 A. The spring clip  208 A may be compressed to allow the shield  202 A to fit over the shank  201 A and then spring back substantially to its original form once within a depression or other ledge within the shank  201 A. The shield  202 A may have an axial diameter  250  sufficient to cover the shank  201 A and generally protect it from impact with a formation. The shield  202 A may form a cap over the shank  201 A. The side of the shield  202 A opposite the recess  215 A may comprise a frustum or a substantially conical geometry. The substantially conical geometry may comprise an impact tip  203 A bonded to the shield  202 A opposing the recess  215 A. 
     The impact tip  203 A may comprise a super hard material  211 A bonded to a carbide substrate  210 A. The super hard material  211 A may comprise diamond, polycrystalline diamond with a binder concentration of 1 to 40 percent weight, cubic boron nitride, refractory metal bonded diamond, silicon bonded diamond, layered diamond, infiltrated diamond, thermally stable diamond, natural diamond, vapor deposited diamond, physically deposited diamond, diamond impregnated matrix, diamond impregnated carbide, monolithic diamond, polished diamond, coarse diamond, fine diamond, non-metal catalyzed diamond, cemented metal carbide, chromium, titanium, aluminum, tungsten, or combinations thereof. 
     The shank  201 A may remain stationary with respect to a holder (not shown). The shank  201 A may comprise a ledge  214 A that may flare out to meet the shield  202 A. The ledge  214 A may have a ledge diameter  252  larger than a shank diameter  254  of the majority of the shank  201 A. The shank  201 A may include a lubricant chamber  204 A. The pick degradation assembly may also comprise a seal  206 A,  209 A and a protective ring  205 A. A rigid element  207 A may be disposed adjacent to the seal  206 A,  209 A. The rigid element  207 A and seal  206 A,  209 A may be disposed adjacent to the ledge  214 A. 
     The shield  202 A may be able to freely rotate around the shank  201 A. The lubricant chamber  204 A may dispense lubricant intermediate, or between, the shank  201 A and the shield  202 A. The lubricant may aid in the rotation of the shield  202 A with respect to the shank  201 A. It is believed that by allowing the shield  202 A to freely rotate around the shank  201 A, that the wear on the pick degradation assembly  101 A during operation will on average be spread around the entire assembly as opposed to just a single side. Furthermore, it is believed that by spreading the wear around the entire assembly  101 , the assembly  101  may last longer. 
     The seal  206 A,  209 A may be disposed intermediate, or between, the shank  201 A and the shield  202 A. The seal may comprise an O-ring  209 A and a rubber washer  206 A. The seal  206 A,  209 A may serve the purpose of sealing lubricant within the pick degradation assembly  101 A and keeping dirt and debris from penetrating the space intermediate, or between the shield  202 A and the shank  201 A. A protective ring  205 A may be disposed axially around the assembly  101 A, adjacent to both the shield  202 A and the shank  201 A. The protective ring  205 A may prevent particles from entering the vicinity of the rigid element  207 A and the seal  206 A,  209 A. The protective ring  205 A may comprise a wiper  255  (see  FIG. 7   c ), a metal ring, a plastic ring, or another ring of sufficient dimensions to be disposed around the pick degradation assembly  101 A while limiting access to the space intermediate, or between, the shank  201 A and the shield  202 A. It is believed that the seal  209 A,  206 A may prematurely wear and fail if it is physically exposed to the rotating surface of the pick degradation assembly  101 A. A rigid element  207 A disposed adjacent to the seal  209 A,  206 A may extend the life of the seal  209 A,  206 A. 
     The rigid element  207 A may comprise a ring with a concave inner surface  213 A. The rigid element  207 A may comprise a metal. The rigid element  207 A may be disposed between the shank  201 A and the shield  202 A. The concave inner surface  213 A of the rigid element  207 A may be disposed adjacent to the O-ring  209 A such that the O-ring  209 A lies within a contour of the rigid element  207 A. The concave inner surface  213 A may comprise a texture. The textured surface may allow the rigid element  207 A to more easily engage the O-ring  209 A. The O-ring  209 A may also comprise a textured surface to further aid in a frictional engagement with the rigid element  207 A. The rigid element  207 A may also have a surface that engages the rubber washer  206 A. It is believed that the friction created by the interaction between the rigid element  207 A, the O-ring  209 A and the rubber washer  206 A may prevent the rigid element  207 A from rotating with respect to the shank  201 A. 
     The rigid element  207 A may also comprise a flat surface  212 A. The flat surface  212 A may be polished such that it is smooth. The flat surface  212 A may be adjacent to the shield  202 A. The polished flat surface  212 A of the rigid element  207 A may provide a surface for the shield  202 A to rotate upon with respect to the shank  201 A. The rigid element  207 A may place the O-ring  209 A under compression. The elastic nature of the O-ring  209 A may in turn place an opposing force on the rigid element  207 A forcing it into contact with the shield  202 A. As the pick degradation assembly  101 A is used and the shield  202 A rotates with respect to the shank  201 A, the friction exerted by the shield  202 A onto the polished flat surface  212 A of the rigid element  207 A may cause it to wear and grow thinner. It is believed that the force exerted by the O-ring  209 A onto the rigid element  207 A will force the rigid element  207 A to remain in contact with the shield  202 A even after it has become worn. 
     In some embodiments the rigid element  207 A may comprise a wear resistant surface  212 A. The wear resistant surface  212 A may comprise a material such as diamond, cubic boron nitride, lonsdaleite, tungsten carbide, or a combination thereof. The wear resistant surface  212 A may aid in extending the useable working life of the pick degradation assembly  101 A. 
     Now referring to the embodiment of a pick degradation assembly  101 B depicted in  FIG. 3 , a rigid element  207 B has been flipped  180  degrees with respect to the rigid element  207 A in  FIG. 2 . A rubber washer  206 B has been disposed in a shield  202 B instead of in the shank  201 A as in  FIG. 2 . In this embodiment the rigid element  207 B may be frictionally engaged with the shield  202 B, such that during rotation, the rigid element  207 B may remain stationary with respect to the shield  202 B. In this embodiment, a flat surface  212 B may be adjacent to a shank  201 B. 
     Referring now to  FIG. 4 , a rigid element  207 C may comprise a convex surface  401 . The convex surface  401  may extend into the shield  202 C. During degradation operations the degradation pick assembly  101 C may experience lateral jarring and vibrations. It is believed that the convex surface  401  may provide the shield  202 C with additional lateral stability during rotation and degradation operations. This additional support may extend the life of the pick degradation assembly  101 C by lowering the amount of wear that the pick degradation assembly  101 C receives. 
     Referring now to  FIG. 5 , a pick degradation assembly  101 D may comprise a spring  501 . The spring  501  may be disposed intermediate, or between, a rigid element  207 D and a shank  201 D. The spring  501  may exert a force onto the rigid element  207 D pushing the rigid element  207 D into contact with a shield  202 D. This may aid in maintaining contact between the rigid element  207 D and the shield  202 D as the rigid element  207 D wears. A rubber washer  206 D may function as a seal. 
     Referring now to  FIG. 6 , a pick degradation assembly  101 E may be retained in a holder  605  and further retained in a block  620 . The pick degradation assembly  101 E may also comprise a shield  602  and a shank  601 . In this embodiment, the shield  602  may be rigidly connected to the shank  601  and rotate within the holder  605  together with the shank  601 . An impact tip  603  may be bonded to the distal end of the shield  602 , the impact tip comprising a superhard material  611  bonded to a carbide substrate  610 . A rigid element  607  may be disposed intermediate, or between, the shield  602  and the holder  605 . The rigid element  607  may be pressurized by a pressing seal element  606 ,  609 . In this embodiment the seal element  606 ,  609  comprise a rubber washer  606  and an O-ring  609 . The seal element  606 ,  609  may press the rigid element into the holder  605  as shown or alternately into the shield  602 . This embodiment may allow the shield  602  and shank  601  to rotate relative to the holder  605  while maintaining lubricant within the assembly  101 E. 
       FIGS. 7   a ,  7   b,    7   c,    7   d  and  7   e  depict embodiments of various components of a pick degradation assembly.  FIG. 7   a  depicts an embodiment of a rigid element  207 F. The rigid element  207 F may comprise a rigid and wear resistant material such a metal. The rigid element  207 F may comprise a concave inner surface  213 F. The concavity of the surface  213 F may change based upon the O-ring size that it is designed to receive. 
       FIG. 7   b  depicts an embodiment of a protective ring  205 F. The protective ring  205 F may comprise a rigid material such as metal or plastic. The girth of the protective ring  205 F may substantially cover any gap that may exist between a shield and a shank. It is believed that the protective ring  205 F may aid in preventing debris from penetrating between the shield and the shank. 
       FIG. 7   c  depicts a cross-sectional view of another embodiment of a protective ring  205 G comprising a wiper  255 G. The wiper  255 G may comprise an elastic material. It is believed that the wiper  255 G may further aid in preventing debris from penetrating between a shield and a shank. 
       FIG. 7   d  depicts an embodiment of an O-ring  209 G. The O-ring  209 G may comprise an elastic material. 
       FIG. 7   e  depicts an embodiment of a rubber washer  206 G. The rubber washer  206 G may function as a seal and as a friction surface. 
     Whereas the present invention has been described in particular relation to the drawings attached hereto, it should be understood that other and further modifications apart from those shown or suggested herein, may be made within the scope and spirit of the present invention.

Summary:
In one aspect of the present invention, a degradation assembly comprises a pressing seal element and a pressurized rigid element disposed intermediate a rotating component and a stationary component. The rotating component comprising an impact tip bonded to an end opposing the stationary component. The seal element may energize the rigid element against one of the components to form a slidable seal capable of holding lubricant within the assembly and keeping debris out while still rotating.