Abstract:
A gear case seal is provided for use with a traction motor. The seal may have an arcuate body with an outer annular layer forming a centrally located channel extending along its length, and an inner annular layer bonded to the outer annular layer along opposing axial edges so as to close off the centrally located channel. The body may also have a middle layer disposed within the centrally located channel and made from a material different than a material of the inner and outer layers.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure is directed to a seal and, more particularly, to a pinion seal for a traction motor gear case. 
       BACKGROUND 
       [0002]    A locomotive includes multiple different traction motors that drive separate wheel sets to propel the locomotive. Each traction motor receives electricity from a generator powered by one or more engines of the locomotive. The traction motor converts the electricity to mechanical rotation, and transfers the rotation to the corresponding wheel set via a shaft and a set of reduction gears. 
         [0003]    The reduction gears are housed within a gear case, and the shaft passes through an opening in a first side wall of the gear case. A pinion gear is connected to an end of the shaft opposite the motor and engages a bull gear inside the gear case. The bull gear is connected to a corresponding wheel shaft, which extends through an opening in an opposing second side of the gear case. Seals are located around the motor shaft and the wheel shaft at the first and second side walls to help retain lubricating fluids within the gear case. The seal around the motor shaft is commonly known as a pinion seal. 
         [0004]    Historically, the pinion seal has been fabricated from an adhesive. In particular, an adhesive was applied to the gear case and to surfaces of the traction motor and allowed to set, so as to create a fluid tight seal around the motor shaft. This type of seal, however, often does not bond properly with the gear case and/or the traction motor due to residual oil or debris left on the surfaces from machining processes. In order to try to improve bonding of the adhesive, strict cleaning regimes have been implemented. The adhesive seal has still proven to fail under certain conditions, allowing lubricant to leak from the gear case, and the strict cleaning regimes have increased a cost of seal fabrication. 
         [0005]    An alternative pinion seal is described in U.S. Pat. No. 5,123,297 that issued to Renk et al. on Jun. 23, 1992 (“the &#39;297 patent”). Specifically, the &#39;297 patent discloses a lubricant retaining device molded from a deformable elastomeric material. The device has a base, a rim with compressible lips, a column connecting the rim to the base, and deformable legs extending from the base. The rim is configured to receive a traction motor collar, with the lips extending radially inward into a groove of the collar. The legs of the base are configured to extend in an opposite direction (i.e., radially outward) into a holding channel of an associated gear case. When installed, the lips and the legs provide a slight interfering fit within the groove and the channel, thereby creating a seal that inhibits leakage of lubricant from the gear case. 
         [0006]    While the lubricant retaining device disclosed in the &#39;297 patent may have improved sealing over the traditional adhesive discussed above, it may still be problematic. In particular, the device, because of the need for precise placement of the lips and legs within corresponding grooves and channels, may be prone to improper assembly and/or damage during assembly. In addition, because the device relies on a single means of sealing (i.e., an interference fit), the device may have reduced applicability (e.g., applicability to only low-pressure applications and/or highly viscous applications). 
         [0007]    The pinion seal of the present disclosure is directed at solving one or more of the problems sot forth above and/or other problems in the art. 
       SUMMARY 
       [0008]    In one aspect, the disclosure is related to a seal for a gear case of a traction motor. The seal may include an arcuate body having an outer annular layer forming a centrally located channel extending along its length, and an inner annular layer bonded to the outer annular layer along opposing axial edges so as to close off the centrally located channel. The body may also have a middle layer disposed within the centrally located channel and made from a material different than a material of the inner and outer layers. 
         [0009]    In another aspect, the disclosure is related to a traction motor gear case assembly. The traction motor gear case assembly may include a traction motor shaft, a pinion gear mounted to a distal end of the traction motor shaft, and a bearing configured to support rotation of the traction motor shaft. The traction motor gear case assembly may also have a bearing support structure configured to contain the bearing and having an annular flange extending radially outward at the pinion gear. The traction motor gear case assembly may also include a gear case configured to contain the pinion gear. The gear case may have a wall with an annular groove that is generally concentric with the annular flange of the bearing support structure, and a seal may be disposed between the bearing support structure and the gear case. The seal may have an outer annular layer fabricated from a synthetic flouropolymer and forming a first centrally located channel extending along its length and an outer protrusion configured to be received within the annular groove of the wall of the gear case. The seal may also have an inner annular layer fabricated from a synthetic flouropolymer, bonded to the outer annular layer along opposing axial edges so as to close off the centrally located channel, and forming a second centrally located channel configured to receive the annular flange of the bearing support. The seal may additionally have a closed-cell foam middle layer disposed within the first centrally located channel and annularly bonded to the inner and outer annular layers. The inner and outer annular layers may together form legs at the opposing axial edges that extend away from the centrally located channel. The body at the centrally located channel may be configured to form a radial compressive seal and the legs may be configured to form gap seals. 
         [0010]    In another aspect, the disclosure is related to a method of forming a pinion seal for a traction motor gear case. The method may include molding an outer arcuate layer from a synthetic flouropolymer to form a first centrally located channel extending along its length, and molding an inner arcuate layer from the synthetic flouropolymer to form a second centrally located channel extending along its length. The method may also include laying a closed-cell foam middle layer having an adhesive backing into the first centrally located channel of the outer arcuate layer, applying an adhesive backing to the inner arcuate layer, and placing the inner arcuate layer over the outer arcuate layer and the closed-cell foam middle layer. The method may further include rolling the inner arcuate layer, the outer arcuate layer, and the closed-cell foam middle layer to bond the closed cell foam middle layer to the inner and outer arcuate layers and to bond axial edges of the inner and outer arcuate layers to each other. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is an isometric illustration of an exemplary disclosed locomotive; 
           [0012]      FIGS. 2 and 3  are isometric and cross-sectional illustrations, respectively, of an exemplary traction motor gear case assembly that may be used in conjunction with the locomotive shown in  FIG. 1 ; and 
           [0013]      FIGS. 4-7  are side, end, cross-sectional, and enlarged view illustrations, respectively, of an exemplary seal that may be used in conjunction with the traction motor gear case assembly of  FIGS. 2 and 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0014]      FIG. 1  illustrates an exemplary locomotive  10  that includes a car body  12  supported at opposing ends by a plurality of trucks  14  (e.g., two trucks  14 ). Each truck  14  nay be configured to engage a track (not shown) and support a base platform  16  of car body  12 . Any number of engines may be mounted to base platform  16  and configured to drive a plurality of wheels  18  included within each truck  14 . In the exemplary embodiment shown in  FIG. 1 , locomotive  10  includes a first engine  20  and a second engine  22  that are lengthwise aligned on base platform  16  in a travel direction of locomotive  10 . One skilled in the art will recognize, however, that first and second engines  20 ,  22  may be arranged transversally or in any other orientation on base platform  16  and/or that a different number of engines may be included. 
         [0015]    Each truck  14  may have two or more axles  26  that are each configured to rigidly support wheels  18  at opposing ends thereof, such that wheels  18  and axles  26  rotate together. A traction motor  28 , for example an electric motor driven with power generated by first and/or second engines  20 ,  22  (referring to  FIG. 1 ), may be disposed at a lengthwise center of each axle  26 , connected to a frame of truck  14 , and configured to drive paired wheels  18  via axles  26 . 
         [0016]    As shown in  FIGS. 2 and 3 , a gear case assembly  30  may be associated with each traction motor  28 , and configured to affect a speed-to-torque ratio of the power output of traction motor  28 . For example, gear case assembly  30  may be disposed between a motor shaft  32  (shown only in  FIG. 3 ) of traction motor  28  and a wheel shaft  34  (shown only in  FIG. 2 ) of wheel  18 . Gear case assembly  32  may include, among other things, a housing  36 , a first gear (e.g., a pinion gear—shown only in  FIG. 3 )  38  connected to a distal end of motor shaft  32 , and a second gear (e.g., a bull gear—shown only in  FIG. 2 )  40  connected to an end of wheel shaft  34 . First gear  38  may be configured to mesh with and drive second gear  40 . Housing  36  may be configured to protect first and second gears  38 ,  40  from dust and debris in the environment, as well as to retain a lubricating fluid at an interface of first and second gears  38 ,  40 . 
         [0017]    Housing  36  may be split into a first half  42  and a second half  44  that are connected to each other along a parting line  46 . Parting line  46  may pass through an axial center of a pinion bore  48  (referring to  FIG. 3 ) associated with motor shaft  32  and through an axial center of a bull bore  50  associated with wheel shaft  34 . Together, first and second halves  42 ,  44  may form a generally hollow structure defining an at least partially enclosed space that houses first and second gears  38 ,  40 . An annular lip  51  may be formed in a side wall  60  of housing  36  at first gear  38  to aid in sealing housing  36  to traction motor  28 . Housing  36  may be equipped with a conventional bull seal (not shown) that engages wheel shaft  34  at a side wall  52 , and a pinion seal  54  that engages lip  51  and a bearing support  56  (i.e., a support structure configured to mount and contain a bearing  58 ) of traction motor  28  at side wall  60 . 
         [0018]    As seen in the enlarged portion of  FIG. 3 , pinion seal  54  may be configured to seal against lip  51  of housing  36  at an outer periphery thereof, and seal against a flange  62  of bearing support  56  at an inner periphery. Specifically, flange  62  may extend radially outward at first gear  38  and be generally concentric with an annular groove  64  located within, an inner surface of lip  51 ; and pinion seal  54  may be insertable into groove  64  and configured to internally receive flange  62 . As will be described in more detail below, pinion seal  54  may create a sealing interface in two different ways. In particular, pinion seal  54  may create a radial compression seal between flange  62  and groove  64 , and create a gap seal within a clearance that exists between radial surfaces of bearing support  56  and lip  51  located at axial ends of flange  62  and groove  64 . 
         [0019]    As seen in  FIGS. 4-7 , pinion seal  54  may be generally arcuate and include a single circular body or two substantially identical semi-circular bodies (shown in  FIG. 4 ) that are configured to be installed end-to-end to create the complete circular shape that surrounds motor shaft  32 . A two-piece design may be simpler to assemble than a single piece design, in some applications. A single piece design, however, may be more robust and/or have enhanced sealing properties, in other applications. 
         [0020]    Pinion seal  54  may be fabricated from three different layers, including an outer annular layer  66 , an inner annular layer  68 , and a middle layer  70  disposed between inner and outer annular layers  66 ,  68 . Each of inner and outer annular layers  66 ,  68  may include a centrally-located channel  72 .  74  that extends along its length, and channels  72 ,  74  may be generally concentric with each other and form an enclosed annular space that is substantially filled with middle layer  70 . Opposing axial edges  76 ,  78  of inner and outer annular layers  66 ,  68  may be bonded to each other during manufacture, such that the enclosed annular space is substantially sealed from the environment. 
         [0021]    The formation of channel  74  within outer annular layer  68  may create a corresponding annular protrusion at an outer surface thereof having a profile generally matching the inner surface profile of channel  72 . Channel  72  of inner annular layer  66  may be configured to receive flange  62  of traction motor  28 , while the annular protrusion of channel  74  may be configured to be received within groove  64  of housing  36  of gear case assembly  30 . As pinion seal  54  is installed between flange  62  and groove  64 , annular portions of channels  72 ,  74  and middle layer  70  may be pressed together by opposing surfaces of flange  62  and groove  64 , thereby sealing an interface between traction motor  28  and gear case assembly  30 . 
         [0022]    Middle layer  70  may include a filler material that is different from a material of inner and outer annular layers  66 ,  68 . In the disclosed embodiment, inner and outer annular layers  66 ,  68  are fabricated from a synthetic flouropolymer, while middle layer  70  is fabricated from a closed-cell foam. For example, inner and outer layers  66 ,  68  may be fabricated from a skived polytetraflouroethylene, while middle layer  70  may be fabricated from silicone foam. The material of inner and outer layers  70 ,  72  may allow pinion seal  54  to deform elastically and fill voids within flange  62  and/or groove  64 , while the material of middle layer  70  may allow for compression and expansion that fills spaces therebetween during assembly. Middle layer  70  may be bonded to surfaces of channels  72 ,  74  of inner and outer layers  66 ,  68 , respectively. 
         [0023]    In the disclosed embodiment, annular spaces  80  exist at the axial ends of middle layer  70  (shown only in  FIG. 6 ) when pinion seal  54  is uncompressed. These spaces  80  may allow the foam material to expand in an axial direction when compressed during assembly. Spaces  80  may be substantially filled with the foam material of middle layer  70  when pinion seal  54  is compressed. 
         [0024]    In a similar manner, an arc length of middle layer  70  may be less than an arc length of inner and outer annular layers  66 ,  68  when pinion seal  54  is uncompressed. With this configuration, as pinion seal  54  is compressed, the foam material may be pushed out into spaces  82  at ends thereof between inner and outer layers  66 ,  68 . When pinion seal  54  is installed (and middle layer  70  is compressed), the installed arc length of middle layer  70  may be about the same as arc lengths of inner and outer layers  66 ,  68 . 
         [0025]    Axial edges  76 ,  78  of inner and outer layers  66 ,  68  may form legs  84  that extend away from channels  72 ,  74  in opposing axial directions. In the disclosed embodiment, a cross-section of pinion seal  54  through channels  72 ,  74  and legs  84  has a general W-shape. That is, each leg  84  may extend radially inward and axially away from channels  72 ,  74  at an oblique angle (e.g., at about 45°) relative to side walls thereof, distal ends of legs  84  may be located away from the side walls by a distance about equal to an internal width of channels  72 ,  74 , and the distal ends of the legs  84  may be located radially closer to channel  74  than a mid-point thereof. In a particular example, a thickness of legs  84  is about 0.030 inches, and pinion seal  54  has a leg-to-body thickness ratio of about 1:3 when uncompressed. In this same configuration, an internal width of channel  72  may be about equal to an internal height. This configuration may help ensure proper assembly of pinion seal  54  by inhibiting binding or folding of legs  84  within channel  72  and/or within undesired spaces between flange  62  and groove  64 , while still ensuring proper compressive and gap sealing. It should be noted that legs  84  may have the same general configuration (i.e., shape and size) or a different configuration (shown in  FIG. 6 ) to match the corresponding gap geometry between traction motor  28  and housing  36 , as needed. It is contemplated that many different shapes and configurations may be possible. 
       INDUSTRIAL APPLICABILITY 
       [0026]    The disclosed seal may be used in any application requiring lubricant retention. In exemplary embodiments, the disclosed seal is used to seal an interface between a traction motor and a gear case assembly, specifically around a motor axle at a pinion gear of the gear case assembly. In this application, the disclosed seal creates a radial compression seal and a gap seal, both of which help to retain high-pressure and/or low-viscosity fluids. 
         [0027]    Pinion seal  54  may be fabricated by molding inner and outer layers  66 ,  68  to form channels  72 ,  74 . A first adhesive backing may then be applied to one side of middle layer  70 , and then middle layer  70  may be laid within channel  74  of outer annular layer  68  such that the first adhesive backing is located therebetween. A second adhesive backing may then be applied to the outer surface of inner annular layer  66 , and inner annular layer  66  may be laid on top of middle layer  70 , such that the second adhesive backing is located therebetween. The resulting composite may then be rolled to bond middle layer  70  to inner and outer layers  66 ,  68  at channels  72 ,  74 , and to bond axial edges  76 ,  78  of inner and outer layers  66 ,  68  to each other. 
         [0028]    The design of pinion seal  54  may improve manufacture of gear case assembly  30 . In particular, the shape and configuration of legs  84  may help to inhibit improper assembly and reduce a likelihood of pinion seal  54  (i.e., of legs  84 ) folding or binding within channels  72 ,  74  during the assembly process. In addition, because pinion seal  54  may provide two forms of sealing, applications of pinion seal  54  may be increased. 
         [0029]    It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed seal without departing from the scope of the disclosure. Other embodiments of the seal will be apparent to those skilled in the art from consideration of the specification and practice of the system disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.