Abstract:
A bearing cup having a ring and a shoulder extending radially inward from an inner surface of the ring. At least one tang extends axially outward from a first side of the ring. At least one tab extends axially outward from a second side of the ring opposite the first side. And, at least one slot is formed in the second side. The bearing cup prevents the outer race of a conventional rolling element bearing from rotating while allowing the bearing to move in an axial direction. The assembly is designed for use with either a single rolling element bearing or a set of two bearing assemblies or any number of closely spaced bearings. The advantage of the device is that it eliminates spinning of the bearing assembly outer race. The device also prevents frictional sliding between a bearing assembly outer race and a preload spring. Frictional sliding imposed on a bearing outer race can induce galling and subsequently lead to part failure.

Description:
FIELD OF THE INVENTION 
     The present invention relates to bearing assemblies and more particularly to a bearing cup for a bearing assembly. 
     BACKGROUND OF THE INVENTION 
     Typically, rolling element bearings are used in rotating machinery designs (e.g. liquid rocket engine turbopumps) to provide radial and axial support of a rotating shaft assembly. These rolling element bearings are often a single ball bearing or a pair of preloaded angular contact ball bearings. The bearings are typically mounted to the rotating shaft and provide axial and radial positional control of the shaft. 
     One method of obtaining adequate radial and axial load carrying capabilities with some amount of damping is to use a combination of preloaded angular contact ball bearings and a hydrodynamic bearing. Yet many designs, including turbopumps for rocket engine applications, typically incorporate a balance piston to control the axial position of the shaft at various operating speeds. The balance piston utilizes the controlled pressures in a fluid flow circuit to provide axial thrust of the shaft while balancing the loads applied to the turbine. However, the angular contact ball bearings only control the axial position of the rotor during start-up and shut-down conditions. At operating speed, the axial position of the shaft is controlled by the balance piston, as noted above. The amount of axial movement of the shaft is considerable and the design requires that the outer race of the bearing assembly be slidably fitted in the bearing support housing. 
     A hydrodynamic bearing may center the shaft at operating speeds, potentially eliminating contact of the bearing outer race with the bearing support housing. In the absence of contact, the bearing outer race will spin and potentially gall as the race intermittently contacts the bearing housing. This spinning and galling of the bearing outer race can lead to part failure. 
     Accordingly, it would be highly desirable to provide a mechanism for preventing this failure by implementing a bearing cup rotational locking assembly that allows for significant shaft axial travel while preventing rotational movement of the outer race of the bearings. 
     SUMMARY OF THE INVENTION 
     A bearing cup apparatus for use with a bearing is provided. In one disclosed embodiment, the apparatus includes a ring and a shoulder extending radially inward from an inner surface of the ring. At least one tang extends axially outward from a first side of the ring. At least one tooth extends axially outward from a second side of the ring opposite the first side. At least one slot is formed in the second side. The apparatus prevents the outer race of a conventional rolling element bearing from rotating while allowing the bearing to move in an axial direction. The apparatus can be readily used with either a single rolling element bearing, a set of two bearing assemblies, or any number of closely spaced bearing assemblies. The advantage of the apparatus is that it eliminates spinning of the bearing assembly outer race. The apparatus also prevents frictional sliding between a bearing assembly outer race and a preload spring. Frictional sliding imposed on a bearing outer race can induce galling and subsequently lead to part failure. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a partial cross sectional view of an exemplary turbopump having a bearing cup rotational lock assembly constructed according to the principles of the present invention 
         FIG. 2  is an exploded perspective view of the bearing cup rotational lock assembly; 
         FIG. 3  is a perspective view of the bearing cup rotational lock assembly; 
         FIG. 4  is a front perspective view of a bearing cup of the bearing cup rotational lock assembly constructed according to the principles of the present invention; 
         FIG. 5  is a back perspective view of the bearing cup of  FIG. 4 ; and 
         FIG. 6  is a cross sectional view of the bearing cup rotational lock assembly indicated by the box  6 - 6  shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the disclosed embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     Referring to  FIG. 1 , a bearing cup rotational lock assembly (bearing assembly)  10  constructed according to the principles of the present invention is shown mounted in an exemplary turbopump  12 . It is to be understood, however, that the bearing assembly  10  may be employed in numerous other mechanical devices having one or more bearings, including engines, turbines, or rotating shafts. 
     The turbopump  12  generally includes a housing  14 , a damper seal  16 , a shaft  18 , and a rotating component  20 . The bearing assembly  10  is mounted within the housing  14  and supports the shaft  18  for rotation. The damper seal  16  provides rotordynamic damping and radial support to the shaft  18 . The rotating component  20  is mounted on the shaft  18   
     Turning to  FIGS. 2 and 3 , the bearing assembly  10  is illustrated in greater detail. In one disclosed embodiment, the bearing assembly  10  includes a first bearing  30 , a first bearing cup  32 , a second bearing  34 , a second bearing cup  36 , a spring  38 , and a shim  40 . The first and second bearings  30 ,  34  and the first and second bearing cups  32 ,  36  are substantially identical. Accordingly, only the first bearing  30  and first bearing cup  32  will be described in detail, it being understood that the detailed description applies equally to the second bearing  34  and second bearing cup  36 , respectively. In this regard, the various components of the second bearing  34  and second bearing cup  36  will be designated with the number of the component corresponding to the first bearing  30  and the first bearing cup  32  followed by a “′” symbol. 
     The first bearing  30  is illustrated as a preloaded angular contact ball bearing as is known in the art. However, various other rolling element bearing assemblies may be employed. The first bearing  30  includes an outer race  42 , an inner race  44 , a bearing cage  45 , and a plurality of balls  48  (two of which are visible). The inner race  44  is rotatably supported by the plurality of balls  48  within the outer race  42 . The outer and inner races  42 ,  44  are generally ring shaped. 
     Referring now to  FIG. 4 , the first bearing cup  32  is generally ring shaped and defines an axis indicated by line A-A in  FIGS. 4 and 5 . The first bearing cup  32  includes a front side  50 , a rear side  52 , an outer surface  54 , and an inner surface  56 . A pair of tangs  58  extend out from the front side  50  in the direction of axis A-A. While only two tangs  58  are illustrated, it is to be understood that as many or as few as one tang may be employed. The tangs  58  fit within a portion of the housing  14  and prevent rotation of the first bearing  30  while allowing axial movement therein, as will be described in greater detail below. A chamfered edge  60  is formed along the front side  50  and transitions the front side  50  to the outer surface  54 . The chamfered edge  60  aids in inserting the bearing cup  32  into the housing  14  during assembly of the bearing assembly  10 . The chamfered edge  60  also prevents galling from axial travel during operation. A rounded edge could be substituted for the chamfered edge. 
     As best seen in  FIG. 5 , the first bearing cup  32  further includes a plurality of teeth  62  extending out from the rear side  52  in the direction of axis A-A. A plurality of slots  64  are formed between each of the plurality of teeth  62  on the rear side  52 . The plurality of slots  64  are sized to receive the plurality of teeth  62  from the second bearing cup  36  as will be described in greater detail below. While in the particular example provided six teeth  62  and six slots  64  are illustrated, it is to be understood that any number of teeth and slots may be employed. Moreover, the first bearing cup  32  can be used singly by itself in which case no teeth or slots are required. 
     A shoulder  66  is formed on the inner surface  56  adjacent the rear side  52  and extends radially inward. The shoulder  66  is sized to accommodate the spring  38  as will be described below. Moreover, the bearing cup  32  can have lubricated surfaces to reduce sliding friction. The bearing cup surfaces in contact with the outer race  42  are not lubricated in the disclosed configuration. 
     The bearing cup  32  is sized to fit over the outer race  42  of the first bearing  30 . The inner diameter of the inner surface  56  of the first bearing cup  32  is smaller than the outer diameter of the outer race  42  such that the bearing cup  32  is press fitted onto the bearing  30  thereby creating an interference fit between the two. In one disclosed embodiment, the bearing cup  32  is constructed from a high strength steel, although various other materials may be employed. 
     Returning to  FIG. 2 , in the particular example provided the spring  38  is a cylindrical beam spring having raised areas  38 A upon a generally planar surface  38 P. The raised areas  38 A are located on opposite sides of the planar surface  38 P at radial locations such that the raised areas  38 A are not opposed and thereby generate a circumferential wave shape to the spring  38  when under an axial load. Compression of the spring  38  creates the circumferential wave shape and preloads the outer races  42  of the first and second bearings  30 ,  34  in the direction of axis A-A. Alternatively, other biasing members may be used for the spring  38 . 
     Turning now to  FIG. 6 , the interrelationship of the various components of the bearing assembly  10  will be described in greater detail. The first and second bearings  30 ,  34  are mounted onto the shaft  18  between the rotating component  20  and a shaft shim  70 . The shaft  18  extends through the inner races  44 ,  44 ′ of the first and second bearings  30 ,  34  and is supported for rotation therein. The inner races  44 ,  44 ′ are rotatingly and axially fixed to the shaft  18 . The first and second bearings  30 ,  34  are spaced apart from one another by the shim  40  mounted therebetween. 
     As noted above, the first and second bearing cups  32 ,  36  are press fitted onto the first and second bearings  30 ,  34 , respectively. In this regard, the inner surfaces  56 ,  56 ′ have an interference fit with the outer races  42 ,  42 ′. Preferably, the bearing cups  32 ,  36  are installed on the outer races  42 ,  42 ′ by heating the bearing cups  32 ,  36  and chilling the outer races  42 ,  42 ′ such that the bearing cups  32 ,  36  expand and the outer races  42 ,  42 ′ contract. The interference fit that results is designed such that the load imparted on the outer races  42 ,  42 ′ result in a negligible change in the size of the bearing raceway of the outer races  42 ,  42 ′. In addition, the press fit is sized such that the hoop stresses in the bearing cups  32 ,  36  remain within desired limits and a satisfactory amount of fit is maintained during all operating conditions. The first and second bearing cups  32 ,  36  are fixed to the first and second bearings  30 ,  34  such that the rear sides  52 ,  52 ′ ( FIGS. 2 and 4 ) of the first and second bearing cups  32 ,  36  face one another. 
     As best seen in  FIG. 3 , the first and second bearing cups  32 ,  36  engage one another. The teeth  62  of the first bearing cup  32  fit within the slots  64 ′ of the second bearing cup  36  while the teeth  62 ′ of the second bearing cup  36  fit within the slots  64  of the first bearing cup  32 . In the disclosed embodiment, the slots  64 ,  64 ′ are wider than the teeth  62 ,  62 ′ thereby creating a gap, indicated by reference numeral  72 . This allows the bearing cups  32 ,  36  to rotate slightly before locking each other from further rotation. 
     Returning to  FIG. 6 , it can be seen that there is a further gap in the axial direction between the teeth  62 ,  62 ′ and the slots  64 ,  64 ′ such that the bearing cups  32 ,  36  may move in the axial direction. The spring  38  is mounted between the first and second bearing cups  32 ,  36  and is enclosed by the teeth  62 ,  62 ′, and by the shoulders  66 ,  66 ′. The shoulders  66 ,  66 ′ in turn engage the outer races  42 ,  42 ′ of the bearings  30 ,  34 . The shoulders  66 ,  66 ′ further act to ensure that a proper axial fit with the bearings  30 ,  34  is achieved when the bearing cups  32 ,  36  are mounted thereon. 
     After assembly, the spring  38  exerts a force in the direction of axis A-A and urges the outer races  42 ,  42 ′ away from each other. This in turn urges the plurality of balls  48  against the inner races  44 ,  44 ′ thereby preloading the bearings  30 ,  34 . In addition, the shoulders  66 ,  66 ′ prevent frictional sliding between the spring  38  and the outer races  42 ,  42 ′. 
     Pockets  74  (one of which is shown) are formed within the housing  14  for receiving the tangs  58  of the first bearing cup  32 . In the particular example provided, the pockets  74  are illustrated as being formed in part by the housing  14  and the damper seal  16 . However, the pockets  74  may alternatively be formed entirely by the housing  14  (not shown) or entirely by the damper seal  16  (not shown). The pockets  74  have a depth, indicated by reference numeral  76 , that is greater than the length of the tangs  58 , indicated by reference numeral  78 . In this way, movement of the bearing assembly  10  in the direction of axis A-A will never lead to the tangs  58  from escaping the pockets  74  or the tangs  58  from bottoming in the pockets  74 . In addition, the width and thickness of the tangs  58  are designed such that the stresses induced in the tangs  58  are within desired limits for all loading conditions. 
     The bearing cups  32 ,  36  can significantly extend the operational life of a turbopump  12 . At the start of an engine (not shown), the preloaded bearing assembly  10  will provide radial support to the shaft  18 . As the engine (not shown) transitions to operating speeds, a balance piston (not shown) will control the position of the shaft  18  in the direction of axis A-A and the bearing assembly  10  will slide to accommodate the change in axial position. The radial loads between the housing  14  and the bearing assembly  10  may be completely eliminated. In the event that environmentally induced torque on the outer races  42 ,  42 ′ is greater than resisting frictional load between the bearing cups  32 ,  36  and the housing  14 , the bearing cup tangs  58  will prevent rotational movement of the outer races  42 ,  42 ′. The bearing cups  32 ,  36  will also eliminate potential galling of the outer races  42 ,  42 ′ due to the required axial movement of the shaft  18  and due to sliding friction between the spring  38  and the outer races  42 ,  42 ′. 
     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.