Patent Publication Number: US-2011052111-A1

Title: Modular rotor assembly

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 10/889,146, entitled “MODULAR ROTOR ASSEMBLY”, filed Jul. 12, 2004, which is herein incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The field of this invention is modular pre-assembly of rotating components of industrial machinery and more specifically compressors. 
     BACKGROUND OF THE INVENTION 
     Typically, when an end user specifies a compression need from a manufacturer the manufacturer tries to provide a unit from an available product line to meet the performance and price parameters given. Since the potential applications and the specific parameters given by different users can vary, each unit may be specifically built for a unique application. For example, in a drive system, the final driven speed for a unit can vary. Generally, various components of the drive system to be installed in a gearbox have to be individually assembled and aligned with significant precision to prevent premature wear and failure. The assembly in the gearbox includes inner bearings and outer housings, a driven pinion/shaft, oil seals, an impeller to go into the gearbox housing with a gas seal around the shaft, associated bits and pieces of the oil lubrication system, and a shaft end cap and associated fittings. 
     Assembling these components for every unit is labor intensive and therefore expensive. It requires stocking of many options for given components that can be assembled together in only so many discrete ways. This requires greater costs for storage, proper inventory and, most of all, in assembly costs for a given unit. 
     Another costly issue is the need to precision fabricate all the components to facilitate the alignment procedure. The individual part tolerances can add up, making the ultimate alignment more difficult. A failure to properly control alignment can result in premature bearing, seal, or gear set wear. Manually assembling and aligning each unit can be a significant portion of the total labor cost. 
     SUMMARY OF THE INVENTION 
     There is provided a modular pre-assembly of some components of a drive into a carrier. In accordance with an embodiment of the present invention, a carrier is precision machined to accept drive components in an aligned condition to each other for quick assembly into the gearbox housing. Portions of the drive system for a piece of rotating equipment are pre-assembled into a subassembly. The subassembly can be held together by a carrier that is fabricated to accept the components in a proper alignment so that the carrier can be installed as a unit. In one embodiment, the carrier becomes a gearbox housing component that is installed, saving the need for individual component alignment. This modular approach allows an assembly having a single part number to apply to a given compressor unit and further allows standardization of air ends of compressors with specific impellers and inlets added to meet requirements of a specific application. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is the currently known way of assembling the components of the drive that requires significant time to insure proper component alignment; and 
         FIG. 2  shows the modular approach of the present invention where some of the drive components are pre-assembled into a carrier. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
       FIG. 1  represents the known way to assemble the illustrated components. Inner bearings  10  and  11  and outer housings  12  and  13  are mounted on a gearbox or compressor housing. Generally, the gearbox housing is horizontally split and the mating halves have a semicircular cutout so that upon assembly, the bearings are respectively supported in the opposed gearbox housing walls. A geared pinion shaft  14  extends through bearings  10  and  11 . An end cap  18  goes over the end of the shaft  14 . Various piping manifolds  20 , which are connected to each of the bearings  10  and  11 , are illustrated. An oil seal  21  and a gas seal  22  are mounted to respective housings  17  and  19 . The gearbox housing can be integrally cast in halves to form the gearbox lower and upper housings so that the assembly is completed around the housings  12  and  13  and housings  17  and  19 . An impeller  24  is fitted to the end of the pinion shaft  14  and secured with a bolt  26 , preferably through the open end of the scroll or gearbox housing. The stocking of these individual components and the custom combination of them to meet the requirements of a specific unit adds assembly, record keeping, and storage costs. The bearings  10  and  11  must be aligned to the pinion shaft  14  so as to maintain alignment of the gear meshes in the gearbox housing. 
       FIG. 2  illustrates an embodiment of the present invention. A carrier or cartridge  28  holds the bearings  10  and  11 , seals  21  and  22 , end cap  18 , and pinion shaft  14 . The carrier  28  has an opening  30  to allow a bull gear access to mesh with the pinion shaft  14 . Oil passages  32  can be integrated into the carrier  28  and single or multiple end connections  34  can be provided at an end  36  of the carrier  28 . A reconfigured end cap  18  is mounted at the end  36  of the carrier  28 . Oil seal  21  is now within the carrier  28  while gas seal  22  is at end  38  of the carrier  28 . 
     Those skilled in the art will appreciate that the components mounted to the carrier  28  are aligned by virtue of assembly to the precision machined carrier  28 . The carrier  28  with the components mounted to it can be fitted to the lower part of the gearbox housing and scroll until the gas seal  22  is in a proper location as determined by alignment of groove  40  with an opening in the scroll or gearbox housing for insertion of a retaining Woodruff key or equivalent through the scroll or gearbox housing and into the groove  40 . At that point the top of the gearbox housing and scroll can be mounted to complete the assembly shown in  FIG. 2 . The impeller  24  can be mounted to pinion shaft  14  either before or after the top halves of the gearbox housing and scroll are put on. 
     Those skilled in the art will appreciate that although the preferred embodiment illustrated is in the context of a centrifugal compressor, the illustrated pre-assembly technique can be used on a variety of rotating equipment applications and is applicable regardless of the size of the components or the horsepower of the connected driver. The pre-assembly technique can be applied to directly driven rotating equipment that does not employ a gearbox and a pinion such as  14 . Configuring the carrier  28  to include oil passages  32  further speeds up the assembly process. The use of an alignment groove such as  40 , which can take a variety of forms and does not need to extend circumferentially, also insures that the carrier  28  is properly positioned with respect to the gearbox and the impeller  24  in the surrounding scroll. The use of the carrier  28  assures alignment of the components mounted therein and reduces assembly time. The assembly can be stocked as a single part number and be warehoused pre-assembled. For a centrifugal compressor assembly, the assembled components in a carrier  28  allow the air end of the compressor to become a common assembly. That is, the impeller  24  and inlets (not shown) can be assembled locally to meet the requirements of a specific installation. The high level of alignment that can be obtained with the use of the carrier or cartridge will enhance the reliability of the rotating equipment and will provide additional hours of running time without maintenance or costly repairs. The cartridge concept is applicable on installations where there is a gearbox housing that serves as a base or in other applications where the base is a structure, such as when the drive is direct from driver to the shaft. 
     The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made without departing from the spirit of the invention.