Abstract:
A modular rotary union and method of fabricating the same. The modular rotary union includes a housing and a rotor. The rotor includes a shaft portion rotatably supported in an axial bore of the housing. The rotor further includes a head portion secured to one end of said shaft portion. The shaft portion is selected from a quantity of shafts of a predetermined size and of a predetermined number of ports machined from a first quantity of material. The head portion is selected from a quantity of heads of a predetermined type, size, number of ports and port type machined from a second quantity of material.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Application No. 60/804,208 Filed Jun. 8, 2006, which is incorporated herein in its entirety. 
     
    
     BACKGROUND 
       [0002]    Rotary unions or rotating unions are used in applications where it is necessary to communicate fluid between stationary and rotating components of a machine or device or between relatively rotating components of a machine or device. 
         [0003]    A typical rotary union includes a housing and a rotor. The housing generally includes an axial bore and one or more ports that are open at one end to the exterior of the housing and open at the other end to the axial bore. The rotor includes a shaft portion that rotates within the axial bore of the housing. The other end of the shaft portion typically includes a coaxial head portion that extends a distance from the end of the housing and secures or couples to the rotating component of the machine or device being served by the rotary union. One or more fluid passages in the rotor communicate fluid to the respective ports in the housing. 
         [0004]    Rotary unions vary considerably in sizes, types of fluids (liquids and gases) communicated, fluid pressures, relative rotational velocities and the number of ports. In addition, there are several fluid coupling conventions that govern the manner of coupling the ports and passages to the fluid lines and components of the machines or devices being served by the rotary unions. For example, depending on the application, the ports and passages may need to be tapped and threaded according to NPT (National Pipe Taper) standards, SAE (Society of Automotive Engineers) standards, BSP (British Standard Pipethread) standards, ISO, etc. Furthermore, the type of thread standards may vary between different ports in the housing or between different passages in the rotor. 
         [0005]    Furthermore, the type of rotor connection may vary. For example, some rotors may incorporate a flanged head for bolting to a mating flange on the rotating component of the machine or device being served. Other types of rotors may incorporate a slip ring for accommodating an electrical connection between electrical elements on the rotating component and electrical elements on the stationary component of the machine or device being served by the rotary union. Still other rotors may couple with a shaft extension or the particular application may require an end cap or other feature. 
         [0006]    Accordingly, it is not practical to stock a quantity of rotary unions of various ports, port sizes, port types, head types, etc. However, there is a need for a system and method for suppliers to reduce lead time needed to deliver rotary unions to meet customer needs. 
         [0007]    Apart from the inefficiencies associated with stocking multiple rotary unions of various sizes, different numbers of passages, different thread standard types, and different types of rotor couplings, etc., there are often problems associated with the conventional manner of manufacturing the rotors used in rotary unions. Typically, rotors are machined from a single piece of metal using a turning lathe machine. For rotors that include a larger diameter flanged head, the flanged head and shaft of the rotor are usually machined from the same metal piece such that they are integrally formed. Thus, the finish diameter of the flanged head dictates the size of the metal piece from which the rotor is machined. As such, it should be appreciated that depending on the difference in outside diameters between the shaft and the head, the amount of machining required to reduce the metal piece to a finished rotor may be substantial. The more machining required, the higher the labor costs will be and the higher will be the costs associated with tool wear and maintenance. Additionally, material costs will necessarily be higher because larger diameter metal pieces must be purchased from which the head and shaft are machined as a single integral rotor. 
         [0008]    Related to the foregoing, for rotors with flange heads, because the flange head is typically larger in diameter relatively thin in comparison to the length of the shaft, the flanged head and shaft portion generally gain and lose heat at different rates during the heat treatment process. Similarly, with cylindrical heads, due to the differences in mass of the head compared to the shaft, heat gain and loss occurs at different rates. This difference in heat loss often results in distortions in the flatness and/or roundness of the flanged head or with respect to the shaft, thereby requiring further machining operations or other measures to correct the distortions or to minimize the occurrence of distortions. While some distortions can be ignored in many applications, in other applications where greater precision is required due to high rotational speeds or other tight tolerance requirements, such distortions are not acceptable. 
         [0009]    Thus, there is a need for an improved system and method for producing rotors which overcomes the increased labor, maintenance and material costs associated with machining the shaft and flanged heads from a single piece, while also eliminating or reducing the occurrence of distortions of the head and/or of the head with respect to the shaft. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is an exploded perspective view of a conventional four-port rotary union. 
           [0011]      FIG. 2  is an exploded cross-sectional view of the conventional four-port rotary union of  FIG. 1  as viewed along lines  2 - 2  of  FIG. 1  showing the integral rotor  16  construction. 
           [0012]      FIG. 3  is an assembled cross-sectional view of the conventional four-port rotary union of  FIG. 2 . 
           [0013]      FIG. 4  is an exploded perspective view of one embodiment of the modular rotary union of the present invention which is otherwise substantially the same as the rotary union of  FIG. 1  except for its modular rotor construction. 
           [0014]      FIG. 5  is an exploded cross-sectional view of the modular rotary union of  FIG. 4  as viewed along lines  5 - 5  of  FIG. 4  showing the modular rotor construction. 
           [0015]      FIG. 6  is an assembled cross-sectional view of the modular rotary union of  FIG. 5 . 
           [0016]      FIG. 7  is a side elevation view of another embodiment of the modular rotary union of the present invention, also with four ports, and also showing the modular rotor, but with a flange head and with other conventional rotary union components. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views,  FIGS. 1-3  illustrate a conventional four-port rotary union  10 . It being understood that rotary unions may vary in size (length and diameter), number of ports (from one to twenty or more), port type (NTP, SAE, BSP, ISO, etc.), port size and head type, such as an NTP head as illustrated in  FIGS. 1-3  or a flanged head as illustrated in  FIG. 7 . Accordingly, the four-port rotary union with NTP head illustrated in  FIGS. 1-3  is provided only as an example of a typical conventional rotary union. 
         [0018]    Also as is conventional, the four-port rotary union  10  depicted in  FIG. 1  comprises a housing  12  and a rotor  14 . Rotors for rotary unions are typically machined from a single billet or a single piece of bar stock using a turning lathe machine thereby producing a rotor with an integral shaft portion  16  and head portion  18  as illustrated in  FIGS. 1-3 . The shaft portion  16  of the rotor  14  is rotatably supported within an axial bore  20  in the housing  12  by a pair of bearing assemblies  22 ,  24  which are seated within annular bearing recesses  26 ,  28  disposed coaxial with the annular bore  20  at each end of the housing  12 . 
         [0019]    The housing  12  includes four axially spaced annular recesses  30 ,  32 ,  34 ,  36  each of which is open to the exterior of the housing by a corresponding port  40 ,  42 ,  44 ,  46 . The ports in the housing are typically radially offset to provide sufficient clearance for connecting lines or tubes (not shown) which convey the fluid to or from the rotary union. The rotor  14  likewise includes four separate passages  50 ,  52 ,  54 ,  56  open at the head  18  and at points along the shaft  16  that correspond to one of the annular recesses  30 ,  32 ,  34 ,  36 . It should be noted that passage  52  is not visible in  FIGS. 2 and 3  because it is disposed behind the through-bore  70  (discussed later). Similarly, passage  56  is not visible in  FIGS. 2 and 3  because it is disposed in the cut-away portion of the rotor  14 . In the embodiment of the rotary union  10 , the passages  50 ,  52 ,  54 ,  56  through the head  18  open into a set of ports ( 50   a ,  50   b ;  52   a ,  52   b ;  54   a ,  54   b ;  56   a ,  56   b , respectively) one of the ports from each set serving as a bypass port for excess fluid. If a flanged head were provided (as in  FIG. 7 ), each passage  50 ,  52 ,  54 ,  56  would open into a single port  50   a ,  52   a ,  54   a ,  56   a.    
         [0020]    In operation, as the rotor  14  rotates within the housing  12 , and as indicated by arrows  60  in  FIG. 3 , fluid is communicated via tubes or lines (not shown) through the ports  30 ,  32 ,  34 ,  36  and through the rotating rotor  14  through the passages  50 ,  52 ,  54 ,  56  open to the annular recesses  20 ,  22 ,  24 ,  26 . Thus, fluid is communicated to and from the stationary element (i.e. the housing  12 ) of the rotary union  10  to and from the rotating element (i.e., the rotor  14 ). 
         [0021]    Also as is conventional,  FIGS. 1-3  depict that the rotor  14  includes a central through-bore  70  through which electrical wires  72  may pass. To prevent the wires  72  from twisting as the rotor  14  rotates, a conventional slip ring  74  is provided which permits the wires  72  to rotate with the rotor  14  relative to the stationary wires  76  leading into the slip ring  74 . 
         [0022]    Turning now to  FIGS. 4-6  one embodiment of a rotary union  100  of modular construction in accordance with the present invention is illustrated. As with the conventional rotary union  10  illustrated in  FIGS. 1-3 , the modular rotary union  100  of the present invention includes a housing  112  and a rotor  114 . Likewise, as with the conventional rotor  14 , the rotor  114  comprising the present invention includes a shaft portion  116  and a head portion  118 . However, unlike the conventional rotor, the head  118  and shaft  116  of the rotor  114  are of modular construction, in that they are separately fabricated, thereby enabling different heads  118  to be interchangeable with different shafts  116 . For example, instead of a cylindrical NTP head as illustrated in  FIGS. 4-6  a flanged head as illustrated in  FIG. 7  may be secured to the modular shaft  116 . Alternatively a head with different port thread standards (i.e., SAE, BSP, ISO, etc.) may be used, etc. It should be appreciated that other than the modular rotor construction, upon assembly, the modular rotary union  100  comprises substantially the same elements and functions identically to the conventional rotary union  10 . 
         [0023]    With a modular rotor, to ensure coaxial alignment of the modular heads  118  and shafts  116 , the modular heads  118  preferably include a recess  120  into which the modular shaft  116  is press fit. To facilitate alignment of the passages  50 ,  52 ,  54 ,  56  in the modular heads and shafts and to ensure that the heads and shafts are securely fixed together, the two parts may be fastened by threaded connectors  200  extend through apertures  202  in the head  118  and are threadably received into threaded apertures  204  ( FIG. 4 ) in the shaft  116 . Alternatively or in addition to threaded connectors, the shafts and heads may be welded together after press fitting or the heads and shafts may be threaded together. Depending on the materials used for the modular heads and shafts, other means of fixedly securing the parts together may be suitable, including, for example, adhesives or other boding agents, ultrasonic welding, heating, or any other suitable means as recognized by those of skill in the art. 
         [0024]    To ensure a fluid tight connection between the passages  50 ,  52 ,  54 ,  56  of the modular head  118  which mate with the passages  50 ,  52 ,  54 ,  56  in the modular shaft  116 , small annular recesses  204  are preferably machined into the face of the modular head  118  to receive an o-ring seal (not shown) of suitable material for the fluid with which the rotary union  100  is to be used. As previously identified, once the modular heads  118  and modular shafts  116  are secured together, the rest of the elements comprising the modular rotary union  100  and the manner of assembling those elements are substantially the same as a conventional rotary union assembly as previously discussed. Additionally, as with a conventional rotary union, the material used for the housing  112  and modular rotor  114  comprising the modular rotary union  100  may be of any material suitable for the type of fluids, pressures, tolerances, and environments with which the rotary union is to be used, including, for example, steel, aluminum, brass, and various other metal alloys, various types of plastics, composites, etc. 
         [0025]    As previously discussed, an advantage that the modular rotary union  100  has over the conventional rotary union, is that the head  118  and shaft  116  are interchangeable. For example, instead of a cylindrical NTP head as illustrated in  FIGS. 4-6  a flanged head as illustrated in  FIG. 7  may be secured to the modular shaft  116 . Alternatively a head with different port thread standards (i.e., SAE, BSP, ISO, etc.) may be used, etc. Also as illustrated in  FIG. 7 , other conventional components may be used when assembling the rotary union. For example, rather than the slip-ring  74  and bearing cover  80 , a conventional shaft extension  82  of any desired length may be coupled to the shaft  16 . Alternatively, an end cap  84  may be secured over the end of the housing. Other known attachments may also be incorporated when assembling the modular rotary union  100 . 
         [0026]    As noted above, one of the advantages of modular construction is that it enables a supplier (manufacturer or distributor) to maintain an inventory of parts that are interchangeable and therefore the supplier is more likely to be able to more efficiently meet the needs of its customers. Rather than fabricating and stocking complete rotors, the supplier is able to stock a quantity of shafts that are interchangeable with a variety of different heads, whether flanged heads or cylindrical heads of various port types. 
         [0027]    An added benefit of fabricating heads and shafts separately as opposed to machining the rotors as an integral unit from a single billet or bar stock is that it reduces material waste. Since the shafts are generally smaller in diameter than the heads, smaller diameter bar stock may be used to machine the shafts. The larger diameter bar stock required for the heads can be used to machine multiple heads from material that would otherwise be machined away for the shafts. Furthermore efficiencies in labor can be gained through less machining time, since less material will need to be machined to produce the shafts separately from the heads. Additionally, efficiencies in labor and precision may be achieved by the machinists being able to produce identical heads multiple times and identical shafts multiple times. Also, with less machining time required to produce the same number of rotors, the fabrication costs will be reduced due to less tool wear and maintenance requirements. 
         [0028]    With modular rotor construction, because the heads can shafts can be separately heat treated, there is less distortion during heat treatment due to the fact that the pieces are of a more uniform diameter and mass. Thus, providing head/shaft assemblies in lieu of one-piece rotors allows higher precision manufacturing of components, resulting in rotary unions that comply with tighter tolerances and therefore meet higher performance standards. 
         [0029]    It should be appreciated that although the modular rotary union  100  of the present invention is shown and described as a four-port rotary union, the rotary union  100  may comprise any number of ports, and may be of any size and length. Additionally, as previously identified, the heads may be of any type and the ports may be of any size and type. As such it should be understood that the foregoing description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the preferred embodiment of the apparatus and the general principles and features described herein will be readily apparent to those of skill in the art. Thus, the present invention is not to be limited to the embodiments of the apparatus and methods described above and illustrated in the drawing figures, but is to be accorded the widest scope consistent with the spirit and scope of the appended claims.