Abstract:
A bearing assembly and method in which a bearing cage is disposed around a rotating member and a housing is disposed around the cage. A first portion of the radial outer surface of the cage extends in a slightly spaced relation to the corresponding portion of the inner surface of the housing, and a second portion of the radial outer surface of the cage projects from the first portion in a radial direction and engages the corresponding portion of the inner surface of the housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This application is a continuation-in-part of pending application Ser. No. 09/970,319 filed Oct. 3, 2001. 
     
    
     
       BACKGROUND  
         [0002]    This invention relates to a bearing assembly and method for a rotating member, and, more particularly, to a bearing assembly and method involving a bearing cage that extends between the rotating member and a bearing housing.  
           [0003]    In many bearing designs of the above type, it is necessary to have a fairly precise engagement between the bearing cage and the bearing housing that will be sufficient through the range of manufacturing clearances of these components, yet will maintain a positive seal at the joint between the housing and cage. Also, it is important that the bearing geometry be controlled and that the clamping force not be high enough to cause bending or deformity. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]    [0004]FIG. 1 is a cross-sectional view of the bearing assembly according to an embodiment of the present invention, shown in operative engagement with a rotor, which is shown in elevation.  
         [0005]    [0005]FIG. 2 is an enlarged cross-sectional view of a portion of the bearing assembly of FIG. 1.  
         [0006]    [0006]FIGS. 3 and 4 are views, similar to FIGS. 1 and 2, respectively, but depicting an alternate embodiment of the present invention.  
         [0007]    [0007]FIGS. 5 and 6 are views, similar to FIGS. 1 and 2, respectively, but depicting another alternate embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0008]    Referring to FIG. 1 of the drawings, the reference numeral  10  refers in general to the bearing assembly according to an embodiment of the invention which surrounds a rotor  12 . It is understood that the rotor  12  is rotated about its axis and forms part of an assembly that includes a driving system for imparting torque to the rotor, in a conventional manner.  
         [0009]    An annular bearing cage  16  extends around the rotor  12  and has an internal recess formed therein for receiving a series of tilt pads  18 , one of which is shown, which form the bearing members. Since the tilt pads  18  are conventional, they will not be described in detail.  
         [0010]    Two axially-extending grooves  16   a  and  16   b  are formed in the outer periphery of the cage  16  with each extending for approximately 180 degrees. The grooves  16   a  and  16   b  are spaced radially inwardly from the outer radial surface of the cage  16  a predetermined amount to form cantilevered portions  16   c  and  16   d  that extend radially outwardly from the respective grooves. The thickness of each cantilevered portion  16   c  and  16   d  is such that it functions as a mechanical spring. It is understood that the thickness of each portion  16   c  and  16   d,  and therefore the stiffness of the mechanical spring formed by each portion, can be adjusted relative to the bearing stiffness of the tilt pads  18 .  
         [0011]    A radially-extending passage  16   e  is formed through the center of the cage  16  for supplying lubricating oil to the tilt pad  18 , in a manner to be explained.  
         [0012]    An annular housing  20  surrounds the cage  16  and has an internal annular recess  20   a  which communicates with the passage  16   e  of the cage  16  and with a radially-extending through passage  20   b.  Oil can thus be introduced to the passage  20   b  and passes through the latter passage, the recess  20   a  and the passage  16   e  for supplying oil to the tilt pads  18 .  
         [0013]    A majority of the radial inner surface of the housing  20  is slightly spaced from the radial outer surface of the cage  16 , including the cantilevered portions  16   c  and  16   d , to form an annular clearance C which communicates with the recess  20   a  of the housing  20  and thus receives some of the above-mentioned oil.  
         [0014]    As better shown in FIG. 2, the axial end portion of the radial outer surface of each cantilevered portions  16   c  and  16   d  is enlarged as shown by the reference numeral  16   f  in connection with the cage portion  16   c.  The enlarged portions, including the portion  16   f,  project radially outwardly from the plane of the latter portions. Although the enlarged portion  16   f  is shown slightly spaced from the corresponding inner surfaces of the housing  20  in FIG. 1 in the interest of clarity, the enlarged portions actually engage the latter surfaces in an interference fit to prevent the leakage of oil from the clearance C. Also, the axial lengths of the enlarged portions, including the portion  16   f  are designed to minimize contact stresses between the cage  16  and the housing  20 .  
         [0015]    The system  10  thus has the following advantages:  
         [0016]    1. A relatively low clamping force acts on the bearing housing  20  to eliminate the risk of deformation and leakage.  
         [0017]    2. No deformation of the inside of the cage  16  occurs where the tilt pads  18  contact the cage, allowing a much better control of the tilt pad bearing geometry.  
         [0018]    3. There is less sensitivity to temperature effects on the housing  20  resulting in minimum deleterious effects on the interference fit between the enlarged portions, including portion  16   f,  of the cantilevered portions  16   c  and  16   d  and the corresponding surfaces of the housing  20 .  
         [0019]    4. The presence of the oil in the clearance C provides additional damping of the bearing assembly  10  in general, thus significantly increasing the damping provided to the rotor  12 .  
         [0020]    Referring to FIG. 3, the reference numeral  30  refers, in general, to the bearing assembly according to another embodiment of the invention. The bearing assembly  30  surrounds a rotor  32  which is rotated about its axis and forms part of an assembly that includes a driving system for imparting torque to the rotor, in a conventional manner.  
         [0021]    An annular bearing cage  36  extends around the rotor  32  and has an internal recess formed therein for receiving a series of tilt pads  38 , one of which is shown, which form the bearing members. Since the tilt pads  38  are conventional they will not be described in detail. A radially-extending passage  36   a  is formed through the center of the cage  36  for supplying lubricating oil to the tilt pad  38 , in a manner to be explained.  
         [0022]    An annular housing  40  surrounds the cage  36  and has an internal annular recess  40   a  which communicates with the passage  36   a  of the cage  36  and with a radially-extending through passage  40   b.  Oil can thus be introduced to the passage  40   b  and passes through the latter passage, the recess  40   a  and the passage  36   a  for supplying oil to the tilt pads  38 .  
         [0023]    Two axially-extending grooves  40   c  and  40   d  are formed in the outer periphery of the housing  40  and each extends for approximately 180 degrees. The grooves  40   c  and  40   d  are spaced radially outwardly from the inner radial surface of the housing  40  a predetermined amount to form cantilevered portions  40   e  and  40   f  that extend radially inwardly from the respective grooves. The thickness of each cantilevered portion  40   e  and  40   f  is such that it functions as a mechanical spring. It is understood that the thickness of each cantilevered portion  40   e  and  40   f,  and therefore the stiffness of the mechanical spring formed by each portion, can be adjusted relative to the bearing stiffness of the tilt pads  38 .  
         [0024]    A majority of the radial inner surface of the housing  40 , including the cantilevered portions  40   e  and  40   f,  is radially spaced from the radial outer surface of the cage  36  to form an annular clearance C which communicates with the recess  40   a  of the housing  40  and thus receives some of the above-mentioned oil.  
         [0025]    As better shown in FIG. 4, an axial end portion  36   b  of the radial outer surface of the cage  36  is enlarged so as to project radially outwardly from the plane of the latter portion. Although FIG. 3 depicts the end portion  36   b  slightly spaced from the corresponding inner surfaces of the housing  40  in the interest of clarity, it actually engages the latter surfaces in an interference fit to prevent the leakage of oil from the clearance C. Also, the axial length of the enlarged end portion  36   b  is designed to minimize contact stresses between the cage  36  and the housing  40 .  
         [0026]    Thus, the embodiment of FIGS. 3 and 4 enjoys all the advantages of the embodiment of FIGS. 1 and 2 set forth above.  
         [0027]    A bearing assembly according to another embodiment of the invention is shown, in general by the reference numeral  50  in FIGS. 5 and 6. As shown in FIG. 5, the bearing assembly  50  surrounds a rotor  52  which is rotated about its axis and forms part of an assembly that includes a driving system for imparting torque to the rotor, in a conventional manner.  
         [0028]    An annular bearing cage  56  extends around the rotor  52  and has an internal recess formed therein for receiving a series of tilt pads  58 , one of which is shown, which form the bearing members. Since the tilt pads  58  are conventional, they will not be described in detail.  
         [0029]    Two axially-extending grooves  56   a  and  56   b  are formed in the outer periphery of the cage  56  with each extending for approximately 180 degrees. The grooves  56   a  and  56   b  are spaced radially inwardly from the outer radial surface of the cage  56  a predetermined amount to form cantilevered portions  56   c  and  56   d  that extend radially outwardly from the respective grooves. The thickness of each cantilevered portion  56   c  and  56   d  is such that it functions as a mechanical spring. The thickness of each cage portion  56   c  and  56   d,  and therefore the stiffness of the mechanical spring formed by each portion, can be adjusted relative to the bearing stiffness of the tilt pads  58 .  
         [0030]    A radially-extending passage  56   e  is formed through the center of the cage  56  for supplying lubricating oil to the tilt pad  58 , in a manner to be explained.  
         [0031]    An annular housing  60  surrounds the cage  56  and has an internal annular recess  60   a  which communicates with the passage  56   e  of the cage  56  and with a radially-extending through passage  60   b.  Oil can thus be introduced to the passage  60   b  and passes through the latter passage, the recess  60   a,  and the passage  56   e  for supplying oil to the tilt pads  58 .  
         [0032]    A majority of the radial inner surface of the housing  60  is slightly spaced from the radial outer surface of the cage  56 , including the cantilevered portions  56   c  and  56   d , to form an annular clearance C which communicates with the recess  60   a  of the housing  60  and thus receives some of the above-mentioned oil.  
         [0033]    As better shown in FIG. 6, the axial end portion of the radial outer surface of each cantilevered portions  56   c  and  56   d  is enlarged as shown by the reference numeral  56   f  in connection with the cage portion  56   c.  The enlarged portions, including the portion  56   f,  project radially outwardly from the plane of the latter portions and engages the corresponding inner surfaces of the housing  60  in an interference fit. Although the enlarged portions, including the portion  56   f,  are shown slightly spaced from the corresponding inner surfaces of the housing  60  in FIGS. 5 and 6 in the interest of clarity, they actually engage the latter surfaces in an interference fit to prevent the leakage of oil from the clearance C. Also, the axial lengths of the enlarged portions, including the portion  56   f,  are designed to minimize contact stresses between the cage  56  and the housing  60 .  
         [0034]    Two axially-extending grooves  60   c  and  60   d  are formed in the outer periphery of the housing  60  and each extends for approximately 180 degrees. The grooves  60   c  and  60   d  are spaced radially outwardly from the inner radial surface of the housing  60  a predetermined amount to form cantilevered portions  60   e  and  60   f  that extend radially inwardly from the respective grooves. The thickness of each cantilevered portion  60   e  and  60   f  is such that it functions as a mechanical spring. The thickness of each cantilevered portion  60   e  and  60   f,  and therefore the stiffness of the mechanical spring formed by each portion, can be adjusted relative to the bearing stiffness of the tilt pads  58 .  
         [0035]    Thus, the embodiment of FIGS. 5 and 6 enjoys all the advantages of the embodiment of FIGS. 1 and 2, and the embodiment of FIGS. 3 and 4.  
         [0036]    It is understood that variations may be made in each of the above embodiments without departing from the scope of the invention. For example, the number of angularly-spaced grooves formed in the cage and the housing in each of the above embodiments can vary and, in fact, there can be only one groove that is continuous in an angular direction. Also, the radial and axial lengths of the cage portions, including the enlarged portions, can vary from those shown in the drawings. Also, the sealing between the housings and their respective cages can be done by other means than metal-to-metal contact as shown on the drawings. Further, the cages and/or the housings can be formed by two split arcuate sections that are attached at their respective ends, in a conventional manner.  
         [0037]    Since other modifications, changes, and substitutions are intended in the foregoing disclosure, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.