Patent Publication Number: US-2022234630-A1

Title: End cap for vacuum discharge outlet gate and method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority pursuant to 35 USC Sec. 119(e) to U.S. provisional application Ser. No. 63/142,031, filed Jan. 27, 2021, entitled “End Cap for Vacuum Discharge Outlet Gate and Method,” the entire specification and drawings of which are hereby incorporated by reference herein as if fully set forth. 
    
    
     BACKGROUND 
     This disclosure relates to outlet gate assemblies on railroad hopper cars employing a vacuum discharge system for unloading the lading from the car. More particularly, it relates to an end cap for such assemblies that permits vacuum discharge with access to only one side of the car. 
     Vacuum discharge outlet gates are illustrated, for example, in U.S. Pat. Nos. 3,797,891 and 4,902,173. U.S. Pat. No. 9,493,172 discloses, in particular, with reference to  FIGS. 11 and 12 , vented end caps or covers to removably close the opposite ends of a conventional vacuum discharge outlet gate of a railroad hopper car. This arrangement permits vacuum unloading with access to only one end of the outlet gate. The disclosure of this latter patent is hereby incorporated herein by reference and hereby made a part hereof as if fully set forth. 
     SUMMARY 
     This disclosure is directed to an apparatus and method useful for unloading a railroad hopper car for carrying particulate lading employing a vacuum discharge transfer system. Such cars include several lading compartments with an outlet discharge gate or valve mounted adjacent the bottom of each compartment. 
     A vented end cap for an outlet gate for unloading a railroad car carrying particulate lading, comprises a generally cylindrical body, a disc-shaped end wall with an interior and exterior surface and at least one flow aperture extending therethrough; a vent hood on the exterior surface of the end wall defines air flow passage having an inlet opening communicating with the flow aperture; a filter support housing on the interior surface of the end wall, defines an air flow chamber having an exit opening communicating with the flow aperture, and with the interior of the vented end cap, and a filter media is supported on the filter support housing between the flow aperture and the exit opening. 
     An outlet gate for unloading a railroad car carrying particulate lading, comprises a manual valve closure mechanism, a discharge tube disposed below the manual valve closure mechanism, and an end adapter at each end having a cylindrical outlet tube defining a discharge opening, a removable vented end cap is secured to each outlet tube having a generally cylindrical body surrounding the cylindrical outlet tube, a disc-shaped end wall with an interior and exterior surface and at least one flow aperture extending through the end wall; a vent hood on the exterior surface defining an air flow passage having an inlet opening communicating with the flow aperture; a filter support housing defining an air flow chamber having an exit opening communicating with the flow aperture and with the interior of the vented end cap; and a filter media is supported on the filter support housing between the flow aperture and exit opening. 
     A method of unloading a railroad car carrying particulate lading having an outlet gate mounted adjacent the bottom of the car, comprises a manual valve closure mechanism, a discharge tube disposed below the manual valve closure mechanism and an end adapter at each end having a cylindrical outlet tube defining a discharge opening, a removable vented end cap is secured to each outlet tube having a generally cylindrical body having surrounding the cylindrical outlet tube, a disc-shaped end wall with an interior and exterior surface and at least one flow aperture extending therethrough; a vent hood on the exterior surface of defining an air flow passage having an inlet opening communicating with the flow aperture; a filter support housing defining an air flow chamber having an exit opening communicating with the flow aperture and with the interior of the vented end cap; and a filter media supported on the filter support housing between the flow aperture and the exit opening; the method comprises: removing one of the end caps from one of the outlet tubes, attaching a vacuum mechanism to the outlet tube from which said vented end cap has been removed, opening the manual valve closure mechanism and applying a vacuum to the discharge opening connected to the vacuum mechanism. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an outlet gate for a hopper car having a vacuum discharge tube with opposite ends closed by removable end caps. 
         FIG. 2  is a fragmentary sectional view of a portion of the outlet gate of  FIG. 1  with a discharge tube closed by a removable end cap. 
         FIG. 3  is an end view of a discharge opening of an end adapter at one end of the discharge tube of the outlet gate of  FIG. 1 . 
         FIG. 4  is a plan view of a clean seal component utilized in the discharge opening at each end of the discharge tube of the outlet gate of  FIG. 1 . 
         FIG. 5  is a fragmentary sectional view, similar to  FIG. 2 , showing a portion of the outlet gate of  FIG. 1  and a vented end cap illustrative of principles of the present disclosure. 
         FIG. 6  is a perspective view of the interior of the end cap of  FIG. 5 , illustrative of features of the present disclosure. 
         FIG. 7  is a perspective view of the interior of the end cap of  FIG. 5 , illustrative of other features of the present disclosure. 
         FIG. 8  is a perspective view of a clean seal suitable for use in conjunction with the end cap of  FIG. 5 . 
         FIG. 9  is a perspective view of the interior of the end cap of  FIG. 5  with the clean seal of  FIG. 8  assembled within the interior of the end cap. 
         FIG. 10  is a fragmentary sectional view similar to  FIGS. 2 and 5  showing a portion of the outlet gate of  FIG. 1  with a modified form of vented end cap and clean seal illustrative of the principles of the present disclosure. 
         FIG. 11  is a fragmentary sectional view, similar to  FIGS. 2, 5 and 10 , showing a portion of the outlet gate of  FIG. 1  with another modified form of vented end cap and clean seal screen illustrative of the principles of the present disclosure. 
         FIG. 12  is a perspective view of the exterior of the vented end cap of  FIG. 11 . 
         FIG. 13  is a perspective view of the interior of the vented end cap of  FIG. 12 , showing an installed, removable filter screen of the present disclosure. 
         FIG. 14  is a plan view of the removable filter screen of the vented end cap of  FIG. 12 . 
         FIG. 15  is a perspective view of the interior of a modified form of the vented end cap of  FIG. 11 . 
         FIG. 16  is a perspective view of a modified form of removable filter screen in the embodiment of the vented end cap of  FIG. 15 . 
         FIG. 17  is a perspective view of the interior of the vented end cap of  FIG. 15 , showing the modified form of removable filter screen of the present disclosure. 
         FIG. 18  is a perspective view of a filter clean seal of the embodiment illustrated in  FIG. 11 . 
         FIG. 19  is a sectional plan view of the filter clean seal of  FIG. 18 . 
     
    
    
     DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
       FIGS. 1 and 2  of this application show views of an outlet gate assembly, generally designated  20 , for attachment to the bottom end of a hopper car lading compartment. As is well known, the outlet gate assembly  20  includes a manually operable valve mechanism  25  to contain the lading within the hopper car compartment above a discharge tube  30  located at the bottom of the outlet gate  20 . When opened, valve mechanism  25  permits the contained materials to flow into discharge tube  30 . 
     Disposed transversely, perpendicular to the length of the car, the discharge tube extends between end adapters  40 , each of which includes a cylindrical outlet tube  41 , having an interior cylindrical surface  42 , and an exterior cylindrical surface  43 , defining discharge opening  45 . (See  FIG. 2 .) 
       FIG. 3  is an end view of one end adapter  40 . It shows the cylindrical outlet tube  41  with discharge opening  45 . A circular back wall  46  includes a semicircular passage  47  that communicates with discharge tube  30 . The passage  47  is formed to occupy the lower 180° of the circular back wall  46 . 
     The cylindrical outlet tubes  41  of an outlet gate  20  are each configured for connection of a vacuum hose of the unloading station or terminal. Since the end adapters  40  at each opposite end of the outlet gate discharge tube  30  each include a cylindrical outlet tube  41 , the car may be connected to an unloading station regardless of its orientation within the terminal. 
     On a hopper car filled with lading, the discharge openings  45  are secured from the elements by removable caps or covers  50  releasably connected to each of the end adapters  40 , usually by eye bolts  51  seen in  FIGS. 1 and 3 . 
     Covers, or caps  50  have a generally cylindrical body  52 , an attachment flange  54  at an open end and a disc-shaped end wall  56 . Radial tabs  58  receive eye bolts  51  to secure the covers in place. In addition, to ensure against intrusion of contaminants, each cylindrical outlet tube  41  is protected by a disposable “clean seal”  90 . Illustrated in  FIGS. 2 and 4 , seal  90  is impervious and positioned within each cylindrical outlet tube  41  at the discharge opening  45 . Clean seals  90  may comprise a molded polymeric disc  91  held in the inner cylindrical surface  42  of discharge openings  45  by compressive friction on outer cylindrical surface  93  of an integral outer rim  92  of somewhat increased cross-section. 
     Hopper cars of the type described here traditionally carry plastic pellets, often color concentrate, used in the manufacture of plastic components. In these processes, avoidance of contamination of pellets or intermixing of colors is of paramount concern. Clean seals  90  positioned within the outlet tubes  41  are an important element of this procedure. The presence of clean seals represents a confirmation that after cleaning and loading, the car lading compartment has not been tampered with or contaminated. 
     Emptying the lading of a hopper car compartment at a terminal having vacuum discharge requires removal of the end caps or covers  50  from each end adapter  40 . Removal of the clean seal  90  from each of the outlet tubes  41  is also necessary to the removal flow path. A vacuum hose is connected to one outlet tube  41  of one end adapter  40 . The end cap  50  and clean seal  90  at the other end must be removed to permit adequate air flow. The vacuum hose draws a vacuum within the discharge tube  30  with inward air flowing through the far end outlet tube  41 . Atmospheric pressure on the lading causes it to move into and through discharge tube  30  to a storage container for later consumption. 
     As described in U.S. Pat. No. 9,493,172, use of the vented end cap there disclosed permits the process to proceed without removal of the end cap at the inaccessible end of the discharge tube. (The far side of the car relative to the vacuum hose connection at the accessible, or, near end). It is only necessary to remove one cover, to attach the vacuum hose to the discharge tube  30 . As described, air flow necessary to lading removal is provided through the passages and filters of the vented cap or cover at the far end of the discharge tube. 
     Turning now to  FIGS. 5 through 9 , there is disclosed a system, including vented end cap or cover  150 , that provides the known advantages of car unloading with single side access, and in addition, provides improved flow and enhanced lading removal rate. In addition to vented end cap or cover  150 , the system incorporates an insertable filter clean seal  190  to provide lading integrity and security reliance. 
       FIG. 5  illustrates the vented end cap or cover  150  and filter clean seal  190  in association with a typical outlet gate  20  with discharge tube  30  connected between end adapters  40 , each having a cylindrical discharge tube  41 . As is understood, though only one transverse end of discharge tube  30  is illustrated, the outlet gate  20 , as illustrated in  FIG. 1 , includes two end adapters  40  connected to opposite ends of discharge tube  30 . Each end adapter  40  includes a cylindrical outlet tube  41  having an interior cylindrical surface  42 , an exterior cylindrical surface  43  defining a discharge opening  45 . 
     Each end of the discharge tube  30  is protected from the elements by a vented cover  150  on cylindrical outlet tube  41 , as illustrated by  FIG. 5 . As stated, in this arrangement, removal of cover  150  at the far end of the outlet gate  20  is not necessary to the unloading process. It should be understood, however, that the near end of outlet gate  20  accessible to the unloading operator, including discharge tube  30  and end adapter  40 , is configured identically to the far end described here in reference to  FIG. 5 . 
     In this embodiment, except during unloading, each end of outlet gate  20  includes an attached protective vented cover  150  and filter clean seal  190 . As previously described, the unloading process involves removal of only the near or accessible end cover  150  which carries associated filter clean seal  190 . When the hopper car compartment is being unloaded, a vacuum hose is connected to the outlet tube  41  of the accessible end of the discharge tube  30 , the end not shown in  FIG. 5 . 
     Referring to  FIGS. 6 and 7 , each vented end cap or cover  150  of this embodiment includes a generally cylindrical body  152  with an attachment flange  154  at an open end and a circular or disc-shaped end wall  156  closing its other end. 
     The cap is usually a molded plastic component. It includes pairs of radial tabs  158  disposed 180° apart on the flange  154 . As shown in  FIG. 7 , tabs  158  are located equidistant from the horizontal centerline of the generally cylindrical body of vented end cap  150  and define slots to receive attachment eye bolts such as eye bolts  51  seen in  FIG. 3 , pivotally connected to the associated end adapter  40 . These bolts releasably secure the cap  150  in place over the discharge opening  45  of the cylindrical outlet tube  41 , with the generally cylindrical body  152  surrounding the outlet tube  41 . As illustrated, each cover or end cap  150  may include an upstanding radial hanger  160  on flange  154  to indicate the orientation (upward) of the cover  150  relative to the end adapter  40 . 
     In this embodiment, as seen in  FIGS. 5 and 7 , the disc-shaped end wall  156  of vented end cap or cover  150  includes a plurality of through holes or flow apertures  162  that provide an inlet for ambient air through the cover. As illustrated in  FIG. 7 , flow apertures  162  are positioned generally at, or above, a horizontal centerline of the disc-shaped end wall  156 . 
     As illustrated in  FIGS. 5 and 6 , the air inlet defined by flow apertures  162  is protected from the elements by a shield or vent hood  164  on the exterior of disc-shaped end wall  156 . As best seen in  FIG. 7 , end wall  156  includes an elongated central keyhole slot  165  to cooperate with filter clean seal  190  associated with the vented end cap  150 , as will be explained below. 
     Vent hood  164  has triangular side walls  166  that support planar wall  168  that is integral with the exterior surface of disc-shaped end wall  156  at a location above the flow apertures  162 . Side walls  166  diverge toward an enlarged inlet opening  170  at the bottom end of the planar wall  168 . Thus, the inlet opening  170  communicates with the flow apertures  162  via the open passage defined by triangular side walls  166 , planar wall  168  and disc-shaped end wall  156 . The pattern of flow apertures  162  is selected to ensure sufficient air flow inward to the interior of cover  150  during the unloading process. 
     Referring to  FIGS. 5, 8 and 9 , there is illustrated a filter clean seal  190  intended for cooperative association with each cover  150  of this embodiment in that it is vented and permits air flow entering end cap  150  though flow apertures  162  to continue into discharge tube  30  through a filtered passage in the clean seal  190  and through semi-circular passage  47  in end adapter  40 . 
     As best illustrated in  FIGS. 8 and 9 , filter clean seal  190  is a molded polymeric disc having a generally planar circular body  191  with a perimeter rim  192  of increased thickness. The rim has an outer cylindrical surface  193  and annular facing surface  194 . 
     Centrally disposed on one side of disc  190  is a horizontally extending post  195  with a transverse retention flange  196 . Post  195  extends in the same direction as annular facing surface  194  of the rim  192 .  FIGS. 5 and 9  show that the central post  195  also extends from wall  191  on the opposite side of body  191  and forms manipulation element or rotation knob  199 . This element is used to rotate clean seal  190  to lock retention flange  196  to wall  156 , beyond elongated central slot  165  of cover  150 . 
     The portion of post  195  carrying transverse retention flange  196  is of a length such that when filter clean seal  190  is placed within the cylindrical body  152  of vented end cap  150 , transverse retention flange  194  is positionable through slot  165 , outside the disc-shaped end wall  156  within the passage defined by vent hood  164 . Through manipulation of knob  199 , rotation of the filter clean seal  190  one-quarter turn releasably secures it within the end cap  150  between disc-shaped end wall  156  and generally semi-circular passage  47  that leads to discharge tube  30 . 
     As seen in  FIGS. 8 and 9 , the bottom area below the horizontal axis of clean seal  190  defines a passage  197  protected with a molded mesh web  198 . Alternatively, the mesh  198  could be replaced by or augmented with a filter media. It is contemplated that a  30 -micron pore size would be satisfactory. 
       FIGS. 5 and 9  show the filter clean seal  190  affixed within the cover or end cap  150 . To restrict air leakage past clean seal  190 , it is contemplated that when filter clean seal  190  is installed in cover  150 , the rim outer cylindrical surface  193  may seal against interior of cylindrical body  152  of cap  150 . Or, as shown in  FIG. 5 , an annular facing surface  194  may seal against disc-shaped end wall  156 . Alternatively, filter clean seal  190  may be sized such that outer cylindrical surface  193  seals against the interior of cylindrical body  152  of end cap  150 . 
       FIG. 10  is an illustration of an alternative arrangement for a filter clean seal  290  housed within end cap  150 . Here, the cap  150  is the same configuration as the cap shown in  FIG. 5  and provides air flow as previously described. That is vented end cap  150  includes disc-shaped end wall  156  with a plurality of flow apertures  162 , protected by vent hood  164  defining inlet opening  170 . 
     Filter clean seal  290  is disclosed, which, like the filter clean seal  190  of  FIGS. 5, 8 and 9 , provide for filtered air flow into semi-circular passage  47  of end adapter  40  and into discharge tube  30 . In this embodiment, the filter clean seal is a disc  291  with an outer rim  292  sized such that its outer cylindrical surface  293  can seal against inner cylindrical surface  42  of cylindrical outlet tube  41  of end adapter  40 . Disc  291  includes central post  295  with retention flange  296  at one end for releasable connection of filter clean seal  290  to vented end cap  150 . Rotation knob  299  at opposite end of post  295  is used to rotate filter clean seal  290  to achieve connection. Filter clean seal post  295  has a length sufficient, such that, with cover  150  attached to end adapter  40  and transverse retention flange  296  in place, outward of wall  156  of cover  150 , the filter clean seal is disposed within cylindrical outlet tube  41 . Outer cylindrical surface  293  of the rim of filter clean seal  190  seals against the inner cylindrical surface  42  of outlet tube  41 . As in the previous embodiment, filter clean seal  290  includes an opening or passage  297  in the lower portion of disc  291  below the horizontal centerline covered by mesh or filter media  298 . 
     A cleaned and empty hopper car may be prepared for its next load by installation of end caps  150  (with attached filter clean seal  190  or  290 ) onto the opposite ends of discharge tube  30  at end adapters  40 . Of course, the manual operator handles of manual valve closure mechanism  25  are placed in the closed position. As seen in  FIG. 3 , the flow path within the end adapter  40  is through semi-circular cross-section passage  47  at the lower half of the end adapter  40 , generally below the horizontal centerline of the discharge opening  45  of the cylindrical outlet tube  41 . 
     During car unloading, with a vacuum hose connected to outlet tube  41 , at the accessible end of outlet gate  30 , air is drawn into the far end vented cover or end cap  150  flow apertures  162  in disc-shaped end wall  156 . Air flowing vertically upward enters vented end cap  150  through the passage formed by vent hood  164  and flows upward from inlet opening  170  to flow apertures  162 . Within the cap volume, the air is directed downwardly to the passage  197  or  297  in clean seal  190  or  290 , where it enters the end adapter  41  through mesh or filter  198  or  298  and ultimately discharge tube  30  at its lower portion, generally below the horizontal centerline of discharge tube  30 . This air flow permits efficient unloading of the lading at the opposite end adapter  40  by virtue of the applied vacuum. Notably, the air entering discharge tube  30  from the end adapter  40  at the far end of the outlet gate travels along the bottom portion of discharge tube  30  toward the near end of the outlet gate, sweeping along particulate matter and remnants of the lading. 
     As previously stated, in the embodiment of  FIG. 5 , air is restricted against bypassing filter clean seal  190  by the sealing engagement of annular facing surface  194  the rim  192  against the interior surface of disc-shaped end wall  156 . Or, outer cylindrical surface  293  seals against the interior of generally cylindrical body  152  of end cap  150 . 
     In the embodiment of  FIG. 10 , outer cylindrical surface  293  at rim  292  of filter clean seal  290  seals against inner cylindrical surface  42  of cylindrical outlet tube  40  of outlet gate  20 . 
       FIGS. 11 through 14  illustrate a further embodiment of a vented end cover or cap  350 . It is configured for association with end adapter  40  of an outlet gate  20  of a hopper car, and compliments the principals and accomplishes the goals of the embodiment of  FIG. 5 or 10 , as well as the vented end cap of the earlier patent  9 , 439 , 177 . 
       FIG. 11  shows one vented end cap  350  installed upon the outlet tube  41  of a typical outlet gate  20 .  FIGS. 11 through 14  illustrate details of its structural configuration and function. It is understood that, as in the previous embodiment, outlet gate  20  is secured from the elements by two vented end cap assemblies  350 , one at each end adapter  40  at each end of discharge tube  30 . In this embodiment, the vented end cap  350  includes an internal filter support housing, generally  374 , and a removable filter element  390 . 
       FIG. 11  also illustrates a form of filter clean seal generally  300 , suitable for use in association with vented end caps of the embodiment of  FIGS. 11 to 17  of the present disclosure to provide vacuum discharge lading removal necessitating access to only one side of the railroad car. The filter clean seal  300  is illustrated in further detail in  FIGS. 18 and 19 . 
     The filter clean seal  300  is a monolithic molded polymeric element with an annular or cylindrical body  301 . Body  301  includes a surrounding radial flange  303  at one end. A radially inward rib  306  extends about the open end of body  301  at radial flange  303 . A conical transition portion  304 , having a cone angle of about five degree (5°) extends to transverse disc-shaped filter screen  305 . 
     As will be understood, the axial length of annular body  401  and conical transition portion  304  from surrounding radial flange  303  to disc-shaped screen  305  is sufficient to accommodate the interior structural configuration of vented end cap  350  of the embodiment shown in  FIGS. 11 to 14 , as well as the modified embodiment of end cap  350  shown in  FIGS. 15 to 17 . 
     Screen  305  may be of a mesh size suitable to pass flowing air consistent with the flow requirements of the unloading process. An example is a fifty percent (50%) open area. 
     Referring to  FIG. 11 , a cleaned railroad car prepared for use will have a filter clean seal  300  installed in each outlet tube  41  of each outlet gate  20 . Filter clean seal  300  is fully inserted into cylindrical outlet tube  41  with radial flange  303  abutting the open end of outlet tube  41 . The polymeric material of the filter clean seal  300  is sufficiently flexible that it may be readily removed. The radial inward rib  306  is provided to better grasp the filter clean seal  300  to facilitate its removal. 
     Filter clean seals  300  are placed within each cylindrical outlet tube  41  of outlet gates  20  as confirmation of readiness for loading. At the unloading site, the near end vented end cap  350  and filter clean seal  300  are removed for attachment of a vacuum hose, as previously described. There is no need to remove filter clean seal  300  at the inaccessible, far end of the car because incoming air passing through the vented end cap  350  would also pass through filter screen  305  of the far end filter clean seal  300 . It is also noted that the filter clean seal  300  used in this arrangement would not include post  295 , transverse retention flange  296  or rotation knob  299  of the earlier embodiments described above. The filter clean seals of the embodiments of  FIGS. 11 to 19  are not connected to end caps  350  or  450 . 
     Filter clean seals disclosed herein, such as shown in  FIGS. 10, 11, and 19 , provide a benefit not heretofore associated with the typical “clean seal” discussed in connection with  FIGS. 2 and 4 . As disclosed herein, employment of vented end caps as disclosed in the embodiments of  FIGS. 10 through 19 , obviate the need to remove the end cap at the far, or inaccessible side of the hopper car. Similarly, the disc-shaped filter clean seals  290  in  FIG. 10  associated with far end cap  150 , or the filter clean seals  300  associated with far end caps  350  or  450  of  FIGS. 11 to 19 , need not be removed during unloading. Thus, these clean seals represent secondary debris filters in the air flow system. Notably, the filter clean seals also act as loose pellet barriers, minimizing spillage of the transported product. 
     Referring to  FIGS. 11 through 14 , each vented end cap or cover  350  is a molded component that includes a generally cylindrical body  352  with an attachment flange  354  at an open end and a disc-shaped end wall  356  closing its other end. 
     The cover or cap  350  is shaped generally like cap 150  of  FIG. 5 . Each cap  350  includes a generally cylindrical body  352  disposed surrounding one cylindrical outlet tube  41  closing discharge openings  45 . The cap  350  includes pairs of radial tabs  358  disposed 180° apart on the flange  354 . As best seen in  FIG. 13 , tabs  358  are located equidistant from the horizontal centerline of the generally cylindrical body of vented end cap  350 . Tabs  358  define slots to receive attachment eye bolts such as eye bolts  51  seen in  FIG. 3 , pivotally connected to the associated end adapter  40 . 
     As seen in  FIGS. 11 and 13 , vented end cap  350  is illustrated to include a drain hole or “weep hole”  311  extending through cylindrical body  352 . It is located at the bottom of the cap to permit egress of moisture within the hopper car or contained lading. Pelletized plastic, a common commodity carried in hopper cars, is often at elevated temperature when loaded. Cooling of the lading may form condensate, which presents as water that finds its way down through the outlet gates and into the end caps. Hole  311  is provided to permit escape of any such contaminant. Such a weep hole may be employed in any of the end caps of the embodiments disclosed. 
     In this embodiment, as seen in  FIG. 11 , the disc-shaped end wall  356  of vented end cap or cover  350  includes a plurality of through holes or flow apertures  362  that provide an inlet for ambient air through the cap end wall  356 . As in the earlier embodiments, through holes or flow apertures  362  are positioned at, or above, the horizontal centerline of the disc-shaped end wall  356 . (Refer to  FIG. 7 ) 
     The ambient air inlet defined by flow apertures  362  is protected from the elements by exterior shield or vent hood  364 , which includes triangular side walls  366  that support planar wall  368  that is integral with the exterior surface of disc-shaped end wall  356  at a location above the flow apertures  362 . Side walls  366  diverge toward an enlarged inlet opening  370  at the bottom end of the planar wall  368 . Thus, the inlet opening  370  communicates with the flow apertures  362 , via air flow passage defined by triangular side walls  366 , planar wall  368  and exterior surface of disc-shaped end wall  356 . The pattern of flow apertures  362  is selected to ensure sufficient air flow during the unloading process. 
     Internally of cap  350 , there is provided a filter support housing  374  molded or otherwise affixed to the interior disc-shaped end wall  356 . Filter support housing  374  is shaped similarly to the vent hood  364  on the exterior of disc-shaped end wall  356 . It includes spaced generally triangular side walls  376 , that support a planar wall  378 . These walls commence above through holes  362  and diverge downwardly toward a closed bottom wall  380  forming an air flow chamber surrounding flow apertures  362  within cover  350 . Planar wall  378  is shorter than corresponding planar wall  368  of exterior vent hood  364  and defines with bottom wall  380  and side walls  376  an air flow chamber with an exit opening  382  open to the interior of vented end cap  350 . A filter element support frame  384  is formed on walls  376 ,  378  and  380  at exit opening  382 . This frame defines a slot that slidably receives, and retains, filter screen element  390 , described in detail below. 
     As illustrated, and previously described, vented end cap or cover  350  may be molded of plastic or other similar material. In this regard, the additional elements of the external vent hood  364 , and filter support housing  374 , may be integrally molded, or, as shown, separate elements attachable to the end wall  356  in surrounding relation to flow apertures  362 . 
       FIG. 11  illustrates one option which is to provide cylindrical connection posts  386  and  387 , which, during assembly housing, can be adhered together to secure the vent hood  364  and air flow chamber defining filter support housing  374  together. An alternative to connection posts  386  and  387  would be weld tabs along the edges of triangular side walls  366  of vent hood  364  and edges of triangular side walls  376  of filter support housing  374  that contact the disc-shaped end wall  356  of vented end cap  350 . Appropriate slots would be provided in disc-shaped end wall  356  to receive the weld tabs and the components are connected by sonic welding. The vent hood  164  of the embodiments of  FIGS. 5 and 10  could be similarly attached to the disc-shaped end wall  156  of vented end cap  150 . 
     Turning now to  FIG. 14 , this is illustrated filter screen element  390 . This is a generally planar frame  392  with handle portion  394  and filter media  396 . Filter media  396  may be a molded mesh or other medium and may have a  30 -micron capture capability. 
     As seen in  FIG. 14 , filter screen element  390  includes lateral edges  398  that slide into channels defined on walls  376  so as to overlie that exit opening  382 . In this embodiment, filter screen element  390  includes retention prongs  397 , which releasably secure filter screen element  390  in place on filter support housing  374  at the filter element support frame  384 . 
     In the embodiment of  FIGS. 11 to 14 , the air flow path is similar to that in the earlier embodiments. With a vacuum hose connected to outlet tube  41  at the accessible end of an outlet gate  20 , air is drawn into the far end of the discharge tube  30  through the vented end cap  350 . Air enters vent hood  364  at inlet opening  370  and travels upwardly to flow apertures  362  in disc-shaped end wall  356 , at or above the horizontal centerline of wall  356 . Filter support housing  374  directs flow downward from flow apertures  362  toward exit opening  382 . The incoming air flows out of the filter support frame  374  through filter media  396  below the horizontal centerline. Thereafter, flowing air travels through semi-circular opening  47  of end adapter  40  and enters the lower portion of discharge tube  30  where it combines with the discharging lading (pellets) and flows into storage. Importantly, the flow within the discharge tube  30  is concentrated on the bottom portion of discharge tube  30  and aids in sweeping that area clear of material. This action improves unloading efficiently and enhances effectiveness of the discharge process. 
       FIGS. 15 to 17  illustrate a vented end cap  450 , similar to, but somewhat modified from, the vented end cap  350  of the embodiment of  FIGS. 11 to 14 . It includes a vent hood on the exterior surface of disc-shaped end wall. It includes a removable filter screen element  490  and varies only in the manner of attachment and retention of the filter screen element  490  within the end cap  450 . Vented end caps  450  are utilized and function in the manner described in relation to vented end caps  350  of  FIGS. 11 to 14 . 
       FIGS. 15 through 17  illustrate details of structural configuration and function of vented end caps  450 . It is understood that, as in the previous embodiment, outlet gate  20  is secured from the elements by two vented end caps  450 , one at each end adapter  40  at each end of discharge tube  30 . The vented end caps  450  include an internal filter support housing, generally  474 , and removable filter element  490 . Also, a filter clean seal  300  is contemplated in this embodiment, as discussed in connection with end caps  350  of the embodiment of  FIGS. 11 to 14 . 
     Referring to  FIGS. 15 through 17 , each vented end cap cover  450  is a molded component that includes a generally cylindrical body  452  with an attachment flange  454  at an open end and a disc-shaped end wall  456  closing its other end. 
     The cap  450  is shaped generally like cap  150  of  FIG. 5 . The caps  350  are disposed with generally cylindrical body  352  surrounding each cylindrical outlet tube  41  closing discharge openings  45 . The cap  450  includes radial tabs  458  on the flange  454 . Tabs  458  define slots to receive attachment eye bolt such as eye bolt  51  seen in  FIG. 3 , pivotally connected to the associated end adapter  40 . 
     In this embodiment, the disc-shaped end wall  456  of vented end cap or cover  450  includes a plurality of through holes or flow apertures  462  similar to apertures  362  of  FIGS. 11 to 14 , that provide an inlet for ambient air through the cap end wall  456 . As in the earlier embodiments, flow apertures  462 , seen in  FIG. 15 , are positioned at, or above a horizontal centerline of the disc-shaped end wall  456 . (Refer to  FIG. 7 ) 
     The vented end cap  450  of the embodiment of  FIGS. 15-17 , the air inlet defined by the through holes flow apertures  462  are protected from the elements by an exterior shield, or vent hood, which is the same as the vent hood  364  of the embodiment of  FIG. 11 . It includes triangular side walls that support a planar wall that is integral with the exterior surface of disc-shaped end wall  456  at a location above the through holes  462 . The side walls diverge toward an enlarged inlet opening at the bottom end of the planar wall. Thus, an inlet opening communicates with the flow apertures  462  via the air flow passage defined by triangular side walls, planar wall and the exterior surface of disc-shaped end wall  456 . The pattern of flow apertures  462  is selected to ensure sufficient air flow during the unloading process. 
     As seen in  FIG. 15 , internally of cap  450 , filter support housing  474  is molded or otherwise affixed to the interior of disc-shaped end wall  456 . Filter support housing  474  is shaped similarly to the vent hood on the exterior of disc-shaped end wall  456 . It includes spaced generally triangular side walls  476 , that support a planar wall  478 . These walls commence above flow apertures  462  and diverge downwardly toward a closed bottom wall  480  forming an air flow chamber surrounding flow apertures  462  within cap  450 . Planar wall  478 , bottom wall  480  and side walls  476  define an exit opening  482  open to the interior of vented end cap  450 . A channel-shaped filter element support frame  484  is formed on walls  476 ,  478  and  480  in surrounding relation to exit opening  482 . This frame slidably receives, and retains, filter screen element  490 , described in detail below. 
     In this embodiment, planar wall  478  terminates in a transverse edge  479 , which includes centrally disposed arcuate relief  481 . This arcuate relief coacts with filter screen element  490 , as will be explained. 
     As illustrated, and previously described, vented end cap or cover  450  may be molded of plastic or other similar material, and the additional elements of the external vent hood  464  and filter support housing  474 , may be separate molded components attachable to the end wall  456  in surrounding relation to the flow apertures  462  in the manner described in connection with vented end cap  350 . 
     Turning now to  FIG. 16 , this is illustrated filter screen element  490 . It is a generally planar frame  492  with handle portion  494  and filter media  496 . Filter media  496  may be a molded mesh or other medium and may have a  30 -micron capture capability. 
     As seen in  FIGS. 16 and 17 , filter screen element  490  includes lateral edges  498  that slide into the channels defined on walls  476  so as to overlie exit opening  482 . Centrally disposed on planar frame  492  at handle portion  494 , filter screen element  490  includes a detent  491 . On installation of filter screen  490  into the channels on filter support housing  474 , detent  491  releasably engages the transverse edge  479  within the arcuate relief  481  to releasably secure filter screen element  490  in place on filter support frame  474 . 
     In the embodiment of  FIGS. 15 to 17 , the air flow path is similar to that in the earlier embodiments. With a vacuum hose connected to outlet tube  41  at the accessible end of an outlet gate  20 , air is drawn into the far end of the discharge tube  30  through the vented end cap  450 . Air enters the vent hood at its inlet opening and travels upwardly to the flow apertures in disc-shaped end wall  456 . Filter support housing  474  directs flow downward from the flow apertures  462  toward exit opening  482 . The incoming air flows out of filter support housing  474  through filter media  496  below the horizontal centerline. Thereafter, flowing air travels through semi-circular opening  47  of end adapter  40  and enters the lower portion of discharge tube  30  where it combines with the discharging lading (pellets) and flows into storage. Importantly, the flow within the discharge tube  30  is concentrated on the bottom portion of discharge tube  30  and aids in sweeping that area clear of material. Again, as in earlier embodiments, this action improves unloading efficiently and enhances effectiveness of the discharge process. 
     In this application, terms inner or outer, interior or exterior, are to be given their ordinary meaning in relation to the disclosed embodiments of vented end caps for an outlet gate of a railcar. Reference to a “horizontal centerline” is made to aid understanding of the position of features of the disc-shaped end wall of the disclosed outlet gate vented end caps. It comprises an imaginary line that bisects the disc-shaped end wall of end caps  150 ,  350 , or  450 . (Refer to  FIG. 7 ) 
     Various features of the present invention have been described with reference to the illustrative embodiments. It should be understood, however, that modifications may be made without departing from the scope of the disclosed subject matter.