Abstract:
An apparatus and method suitable for supporting a cylindrical component. The apparatus includes a pedestal having an upper surface with a semispherical concave shape, and a carriage supported on the upper surface of the pedestal. The carriage has a lower surface and an oppositely-disposed upper surface with elements for contacting and rotatably supporting the cylindrical component. The lower surface of the carriage engages the upper surface of the pedestal and has a semispherical convex shape complementary to the semispherical concave shape of the upper surface of the pedestal. The apparatus further includes a reservoir at and recessed in the upper surface of the pedestal, and a feature for delivering a lubricant to the lubricant reservoir. The lower surface of the carriage and the upper surface of the pedestal define an enclosure around the reservoir.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention generally relates to equipment adapted for supporting articles. More particularly, this invention relates to a self-aligning support assembly capable of supporting a cylindrical component, and in particular large rotatable cylindrical components such as during the manufacture, inspection, and/or servicing of rotors and shafts of turbomachinery, generators, and other axisymmetric components. 
         [0002]    Depending on particular operating conditions, rotors used in steam turbines, gas turbines, and jet engines can have assembled or monolithic constructions. For example, large steam turbines typically have a bolted construction made up of separate rotors, each having a shaft with an integrally-formed wheel whose rim is configured for mounting buckets (blades). The configuration and composition of each separate rotor segment are chosen for the particular section of the turbine (for example, high pressure and low pressure stages) in which the segment will be located. Rotors for gas turbines and jet engines are often constructed by bolting a series of disks and shafts together. Another rotor construction involves welding together rotor segments formed of dissimilar materials, forming what may be termed a multiple alloy rotor (MAR). Monolithic multiple alloy rotors have also been proposed. 
         [0003]    Turbine rotors operate at high rotational speeds in a thermally-hostile environment. Though significant advancements have been made in alloys to achieve long service lives, wear, erosion, corrosion, shock, fatigue and/or overstress may occur, necessitating periodic inspection and, if necessary, repair or replacement of a rotor or shaft. Inspection and servicing of turbine components typically entail mounting the component in a lathe or similar apparatus adapted to rotate the component about its axis, for example, during cleaning, dimensional inspection, nondestructive examination (NDE), disassembly/assembly, and machining. The component is often supported from beneath with rollers that help support the weight of the component without interfering with its ability to rotate. Rollers used for this purpose are typically hardened to resist deformation and hold tolerances under the weight of the component. The non-pliant nature of hard rollers necessitates a long and careful setup to ensure proper alignment of the rollers to the component, including precisely orienting the axes of the rollers parallel to the component. For example, hard roller assemblies are often “blued-in” by applying layout dye to the surfaces of the component, and then adjusting the rollers to achieve a uniform pattern in the dye. As an alternative, soft rollers can be used that are sufficiently compliant to better tolerate misalignments. In some situations, soft rollers are used in an unaligned condition, in which case the surfaces of the rollers are sacrificial. While simplifying setup, soft rollers can be incapable of holding sufficiently tight tolerances for such operations as dimensional inspect and machining. 
         [0004]    In view of the above, it would be desirable if the process of aligning hard rollers to a rotor component could be simplified without degrading the dimensional accuracy normally required of hard rollers when supporting a rotor during inspection and servicing. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0005]    The present invention provides an apparatus and method suitable for supporting a cylindrical component in a manner that permits the component to rotate. An exemplary but nonlimiting example is supporting a turbine rotor component during cleaning, dimensional inspection, nondestructive examination, disassembly, assembly, and/or machining of the component. 
         [0006]    According to a first aspect of the invention, the apparatus includes a pedestal having an upper surface with a semispherical concave shape, and a carriage supported on the upper surface of the pedestal. The carriage has an upper surface and an oppositely-disposed lower surface, with the upper surface having one or more elements for contacting and rotatably supporting the cylindrical component. The lower surface of the carriage engages the upper surface of the pedestal and has a semispherical convex shape complementary to the semispherical concave shape of the upper surface of the pedestal. The apparatus further includes a lubricant reservoir at and recessed in the upper surface of the pedestal, and a feature for delivering a lubricant to the lubricant reservoir. The lower surface of the carriage and the upper surface of the pedestal define an enclosure around the lubricant reservoir. 
         [0007]    According to a second aspect of the invention, the pedestal and the carriage of the apparatus are used to support the cylindrical component through the contact elements of the carriage, and sufficient lubricant pressure is provided within the lubricant reservoir to fluidically decouple the lower surface of the carriage from the upper surface of the pedestal to enable the carriage and its contact elements to self-align with the cylindrical component. 
         [0008]    According to another aspect of the invention, a method of supporting a cylindrical component more broadly entails supporting the cylindrical component above a carriage supported on a pedestal, raising the pedestal and the carriage together to engage the cylindrical component with the carriage, and providing sufficient lubricant pressure between the carriage and the pedestal to fluidically decouple a lower surface of the carriage from an upper surface of the pedestal and thereby enable the carriage to self-align with the cylindrical component. 
         [0009]    A significant advantage of this invention is that the decoupling and self-alignment effect provided by the combination of the lubricant and semispherical surface interface defined by and between the carriage and the pedestal allows for the use of a variety of components as the means for contacting the cylindrical component. For example, the apparatus can employ hard rollers as the contact elements, with the self-alignment capability serving to simplify the alignment of the rollers to the cylindrical component without degrading the dimensional accuracy normally achieved with hard rollers. The self-alignment capability of this invention further permits the use of other contact elements that might not otherwise be practical, for example, a rigid V-block or hydrostatic bearings that define a cradle for supporting a cylinder. In each case, the contact element is capable of holding sufficiently tight tolerances for such operations as dimensional inspections, machining, and other precision operations, during which rotation of the cylindrical component may be required. 
         [0010]    Other aspects and advantages of this invention will be better appreciated from the following detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a perspective view of a turbine rotor repair station in accordance with an embodiment of this invention. 
           [0012]      FIG. 2  is a more detailed perspective view of a support assembly of the repair station of  FIG. 1 . 
           [0013]      FIGS. 3 and 4  are perspective views of a table of the support assembly of  FIG. 2  in raised and lowered positions, respectively. 
           [0014]      FIG. 5  is a perspective view of a carriage and pedestal assembly of the support assembly of  FIGS. 2 through 4 , showing the carriage equipped with a V-block for supporting a rotor component in accordance with an embodiment of this invention. 
           [0015]      FIG. 6  is a perspective view of the carriage and pedestal assembly of  FIG. 5 , showing internal components of the assembly. 
           [0016]      FIG. 7  is a perspective view of a carriage and pedestal assembly similar to  FIGS. 5 and 6 , but equipped with rollers instead of the V-block in accordance with another embodiment of this invention. 
           [0017]      FIG. 8  is an end view of the carriage and pedestal assembly of  FIGS. 5 and 6 , schematically showing cylinders of various diameters supported on the V-block. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]      FIG. 1  represents a turbine rotor repair station  10  in accordance with an embodiment of this invention. A rotor component  12  is represented as being mounted in the station  10  for the purpose of undergoing inspection, service, or some other operation that may be desired during manufacturing or after the component  12  is returned from service. The component  12  is represented as a relatively large diameter rotor, though rotors and rotor shafts with far smaller diameters ( FIGS. 2 and 8 ) are also within the scope of the invention. While the invention will be described in reference to rotor components, which may be rotors and shafts configured for installation in a steam turbine, gas turbine, jet engine, etc., cylindrical components other than rotors are also within the scope of this invention, including generator rotors, steel mill rolls, coal crushers, etc. Furthermore, though particularly adapted to support rotating components, from the following it will become apparent that the repair station  10  is also capable of supporting and preventing the rotation of eccentrically-loaded components, such as during the mounting of buckets (blades) on a rotor. 
         [0019]    The station  10  is represented as having a motor  14  equipped with a drive shaft  15  adapted for coupling to the component  12  to enable the motor  14  to rotate the component  12  about its axis of rotation. Opposite the motor  14 , a thrust bearing assembly  16  is represented for opposing axial forces resulting from rotation of the rotor  12 . The component  12  is supported between the motor  14  and thrust bearing assembly  16  with a support assembly  18 , and all of the equipment depicted in  FIG. 1  is shown mounted to a platform  20 . The station  10  can be a permanent facility within a service center, or can be configured with its platform  20  to have a portable capability. 
         [0020]      FIG. 2  shows the support assembly  18  of  FIG.1  in greater detail, with the large-diameter component  12  replaced by a small-diameter component  12  (e.g., a shaft) to reveal more detail of the assembly  18 . The assembly  18  is represented as generally comprising a frame  22 , a table  24  mounted within the frame  22 , an actuation system  26  for raising and lowering the table  24  within the frame  22 , a pedestal unit  28  mounted on top of the table  24 , and a carriage unit  30  supported on the pedestal unit  28 . The frame  22  can be rigidly attached to the platform  20 , or can be supported by bearings (not shown) to mechanically decouple the support assembly  18  and its components from the motor  14  and the surroundings. 
         [0021]    The frame  22 , table  24 , and actuation system  26  are represented in more detail in  FIGS. 3 and 4 , which are isolated views of the support assembly  18  without the component  12 , pedestal unit  28 , and carriage unit  30 .  FIG. 3  shows the table  24  in a raised position resulting from the operation of the actuation system  26 , which is represented as an electrically-actuated power screw assembly though it could be another mechanical system, a hydraulic system, or an electrical system. The horizontal orientation of table  24  is maintained in part by coupling the table  24  to posts  32  mounted to the frame  22 . In  FIGS. 1 through 4 , four posts  32  are shown coupled to the table  24  with journal bearings  34 , though any number of posts  32  could be used, for example one at each end of the table  24 . While the actuation system  26  and posts  32  are represented as two separate units, it is also foreseeable that the actuation system  26  could be integrated into the posts  32 . Furthermore, the frame  22  and table  24  can have a variety of configurations capable of promoting their mechanical integrity while, if so desired, minimizing their weight. As such, the frame  22 , table  24 , actuation system  26 , posts  32 , etc., shown in  FIGS. 1 through 4  are merely for illustrative purposes and, aside from their functions of supporting and raising the pedestal and carriage units  28  and  30  into engagement with the component  12 , do not limit the scope of the invention. 
         [0022]      FIGS. 5 and 6  show more detailed views of the pedestal and carriage units  28  and  30  shown in  FIGS. 1 and 2 . The pedestal unit  28  comprises a base plate  36  adapted to be secured to the table  24  with bolts. The base plate  36  has a raised central rail  38  integrally machined with the base plate  36 , though it is foreseeable that the central rail  38  could be separately fabricated and attached to the plate  36 . The central rail  38  defines an upper surface  40  of the pedestal unit  28  on which the carriage unit  30  is supported through contact with a lower surface  50  ( FIG. 6 ) of the carriage unit  30 . A pair of mounting blocks  42  are shown bolted to opposite ends of the central rail  38 , from which trunnions  44  ( FIG. 8 ) extend toward each other to provide a support for the carriage unit  30 . The trunnions  44  are shown as defined by ends of bolts  45  threaded into the blocks  52 , which allow the trunnions  44  to be threaded into clamping engagement with slots or recesses  52  ( FIGS. 6 and 8 ) defined at opposite ends of the carriage unit  30 , enabling the trunnions  44  to secure the carriage unit  30  to the pedestal unit  28  and preferably immobilize the carriage unit  30  on the pedestal unit  28  when supporting the weight of the component  12 . Alternatively, the trunnions  44  can be hydraulically operated to engage and disengage the recesses  52 . Still another alternative is to couple the carriage unit  30  to the pedestal unit  28  by other types of clamps mounted to the pedestal unit  28  and operable to engage the ends and/or sides of the carriage unit  30 . 
         [0023]      FIG. 6  shows the upper surface  40  of the pedestal unit  28  as defining a semispherical concave shape within which a reservoir  46  is centrally formed. As will be discussed in greater detail below, the reservoir  46  is intended to contain a fluid, and more particularly a lubricant such as a hydraulic fluid, oil or grease capable of decoupling the carriage unit  30  from the surface  40  of the pedestal unit  28 . The fluid capacity of the reservoir  46  necessary for this purpose will depend on the surface area of the reservoir  46  and the lubricant pressure available to the reservoir  46 . The lubricant can be delivered to the reservoir  46  through fittings  54 , which are shown located at either end of the carriage unit  30  though various other locations are also possible, including up through the table  24  and pedestal unit  28 . Surrounding the reservoir  46 , the semispherical concave upper surface  40  of the pedestal unit  28  is preferably continuous and smooth to provide uniform contact with the semispherical convex lower surface  50  of the carriage unit  30 . 
         [0024]    The lower surface  50  of the carriage unit  30  preferably has a semispherical convex shape complementary to the semispherical concave shape of the upper surface  40  of the pedestal unit  28 , such that the upper and lower surfaces  40  and  50  achieve a close surface-to-surface contact. In addition, the perimeters of these surfaces  40  and  50  provide a surface-to-surface seal that encloses the lubricant reservoir  46 . This surface-to-surface seal is preferably fluid-tight or nearly so under the weight of the component  12  when the carriage unit  30  is pressed downwardly onto the pedestal unit  28 , such that the lubricant within the reservoir  46  can be pressurized to force lubricant from the reservoir  46  and provide a lubrication film between the upper and lower surfaces  40  and  50  of the pedestal and carriage units  28  and  30 . Lubricant expelled from between the surfaces  40  and  50  of the pedestal and carriage units  28  and  30  can be collected and returned to the reservoir  46  with troughs/flanges  48  provided along the sides of the carriage unit  30 . 
         [0025]    The trunnions  44  and their respective recesses  52  prevent the carriage unit  30  from being unintentionally displaced from the surface  40  of the pedestal unit  28 . Furthermore, the trunnions  44  define an axis about which the carriage unit  30  can pivot when not subject to the clamping load of the trunnions  44 . As the carriage unit  30  becomes subject to the weight of the component  12 , the complementary semispherical shapes of the upper and lower surfaces  40  and  50  of the pedestal and carriage units  28  and  30  and the lubrication film therebetween enable the carriage unit  30  to slide and move relative to the pedestal unit  28 , enabling the carriage unit  30  to align to the loading imposed by the component  12 . The trunnions  44  restrict the movement of the carriage unit  30  to the extent that it narrowly limits the pitching motion (in a plane through the axis of the trunnions  44  and normal to the surface  40 ) of the carriage unit  30 , while allowing a limited degree of yaw (twisting) motion (about an axis normal to the pedestal surface  40 ) and rolling motion (about the axis of the trunnions  44 ). 
         [0026]    The carriage unit  30  is provided with one or more contact elements capable of supporting the rotor component  12 , preferably to allow the component  12  to rotate while supported by the support assembly  18 . As represented in  FIGS. 1 ,  2 ,  5  and  6 , the contact elements comprise a V-block  58 . The V-block  58  generally has opposing pads  60  inclined relative to each other and separated by a linear joint  62  at the base of the V-shape. The pads  60  are aligned in a direction parallel to the axis defined by the trunnions  44 , such that the V-block  58  and its pads  60  remain substantially centered on the pedestal unit  28 . As evident from  FIGS. 1 and 2  and particularly  FIG. 8 , the carriage unit  30  is oriented on the support assembly  18  so that the axis of the component  12  is parallel to and directly above the joint  62  between the pads  60 , and the pads  60  approximately symmetrically oppose each other when contacting the component  12 .  FIG. 8  further evidences the ability to accommodate rotor components  12  of a wide range of diameters on the carriage unit  30 . To minimize wear and promote a low-friction contact with the component  12 , the pads  60  are preferably formed of a material softer than the material of the component  12  being supported, with particularly suitable materials believed to be Babbitt metals, nylon, and textolite. The V-block  58  is further represented in  FIGS. 5 and 6  as equipped with ports  56  from which a suitable lubricant (e.g., hydraulic fluid) can be directed onto the surfaces of the pads  60  to generate a lubricant film that serves as hydrostatic bearings capable of supporting the component  12  above the pads  60 . It is foreseeable that the hydrostatic bearings could be used without the pads  60 . 
         [0027]    Finally,  FIG. 7  is a perspective view of the pedestal and carriage units  28  and  30  similar to what is shown in  FIG. 5 , but equipped with rollers  64  instead of the V-block  58  as contact elements in accordance with another embodiment of this invention. As with the pads  60  of the V-block  58  in  FIG. 5 , the rollers  64  are aligned in a direction parallel to the axis defined by the trunnions  44 , such that the rollers  64  remain substantially centered on the pedestal unit  28 . Furthermore, the axes of rotation of the rollers  64  are oriented transverse to the axis of the trunnions  44  but parallel to the axis of the component  12  supported on the carriage unit  30 , such that the rollers  64  are approximately symmetrically opposed from each other when contacting the component  12 . Because of the self-alignment capability providing by the complementary semispherical shapes of the upper and lower surfaces  40  and  50  of the pedestal and carriage units  28  and  30 , enabling the axes of the rollers  64  to automatically align with the axis of the component  12  under the load imposed by the component  12 , the drawbacks of using hard rollers are avoided, permitting the rollers  64  to be manufactured from very wear-resistant materials with hardnesses of 25 Rockwell C or greater, such as an alloy steel. Particularly preferred materials are believed to be AISI 4140 with hardnesses of 30 Rockwell C or greater. Suitable diameters for the rollers  64  are generally about eight inches (about 20 cm), with greater and lesser diameters being foreseeable. Finally,  FIG. 7  shows the carriage unit  30  as equipped with multiple yokes  66  in which the rollers  64  can be supported to accommodate rotor components  12  of various diameters. 
         [0028]    Based on the foregoing, it should be understood that a wide variety of bearings and other contact elements could be used in place of the V-block  58  (with hydrostatic bearings  56  and/or pads  60 ) and the rollers  64 . Furthermore, various materials can be used to construct the pedestal and carriage units  28  and  30 , with nonlimiting examples being carbon steels and structural steels such as ASTM A36. 
         [0029]    In use, the support assembly  18  and its pedestal and carriage units  28  and  30  are adjusted to the centerline of the motor  14 , the carriage unit  30  and its contact elements (V-block  58 , rollers  64 , etc.) are hydraulically lifted with the fluid within the lubricant reservoir  46 , and the component  12  is coupled to the motor  14  through the drive shaft  15  before placing the weight of the component  12  on the carriage unit  30  and its contact elements. Hydraulic pressure is then released from the reservoir  46 , allowing the carriage unit  30  to settle into alignment on the pedestal unit  28 . The trunnions  44  are then moved into engagement with the recesses  52  to secure and preferably immobilize the carriage unit  30  on the pedestal unit  28 . 
         [0030]    While the invention has been described in terms of specific embodiments, it is apparent that other forms could be adopted by one skilled in the art. For example, the physical configuration of the pedestal and carriage units  28  and  30 , as well as the turbine rotor repair station  10  with which the units  28  and  30  are to be used, could differ from those shown in the figures, and materials and processes other than those noted could be used. Therefore, the scope of the invention is to be limited only by the following claims.