Abstract:
A system unloads material, such as bulk quantities of dry product, from a container, such as a railroad hopper car, in a fast and efficient manner. The container defines an interior adapted to contain a product and includes a product discharge section adapted to allow the product to pass therethrough. The material unloading system includes a product outlet line adapted to communicate with the product discharge section. The product outlet line includes a product outlet adapted to allow the product to pass therethrough. A source of pressurized fluid communicates with the product outlet line and is adapted to move product from the product discharge section to the product outlet. A source of vacuum communicates with the product outlet and is adapted to unload the product from the product outlet.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application claims the benefit of U.S. Provisional Application No. 60/220,095, filed Jul. 21, 2000. 

   BACKGROUND OF THE INVENTION 
   This invention relates to an improved structure for unloading bulk quantities of dry product from a railroad hopper car in a fast and efficient manner. 
   Railroad hopper cars are well known in the art and are commonly used to transport bulk quantities of dry product from one location to another. A typical railroad hopper car includes a sealed container that is supported on a pair of spaced apart wheel assemblies. The container has upper surface that is usually provided with a plurality of spaced apart hatches to facilitate the loading of the product into the container. The lower portion of the container is often segmented into a plurality of tapered discharge sections to facilitate the unloading of the product therefrom. 
   In some instances, the unloading of the railroad hopper cars occurs solely under the influence of gravity. To accomplish this, a valve provided on the bottom of the tapered discharge section of the container is opened, allowing the product to flow downwardly therethrough into a receiving apparatus. Such gravity unloading is simple and inexpensive from an equipment standpoint, but has been found to be rather inefficient. This is because the product unloads from the container at a relatively slow rate, which undesirably increases the amount of time and resources required to empty the product from the container. Also, portions of the product often coalesce and adhere to the interior of the container. When this occurs, portions of the product do not unload under the sole influence of gravity, thus requiring additional time and effort to dislodge such portions for unloading. 
   To address these problems, some railroad hopper cars are provided with equipment that introduces pressurized air within the container during the unloading process. The introduction of pressurized air within the container increases the magnitude of the air pressure therein, thus positively urging the product out of the container at a rate that is faster than if the product was unloaded solely under the influence of gravity. Additionally, the flow of pressurized air within the container tends to stir up or fluidize the product therein so as to minimize the occurrence of coalescence and adherence of the product to the interior of the container. Thus, the benefits of pressure differential unloading have been found to outweigh the additional costs associated with the additional equipment that is necessary to perform it. 
   Although railroad hopper cars provided with this pressure differential equipment have functioned successfully for many years, the occurrence of coalescence and adherence of the product to the interior of the container remains a concern. Furthermore, it would be desirable to provide a structure for unloading product from a is railroad hopper car that is even faster than known pressure differential unloading techniques. 
   SUMMARY OF THE INVENTION 
   This invention relates to an improved structure for a system for unloading material, such as bulk quantities of dry product, from a container, such as a railroad hopper car, in a fast and efficient manner. The container defines an interior adapted to contain a product and includes a product discharge section adapted to allow the product to pass therethrough. The material unloading system includes a product outlet line adapted to communicate with the product discharge section. The product outlet line includes a product outlet adapted to allow the product to pass therethrough. A source of pressurized fluid communicates with the product outlet line and is adapted to move product from the product discharge section to the product outlet. A source of vacuum communicates with the product outlet and is adapted to unload the product from the product outlet. 
   Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic side elevational view of a portion of a conventional pressure differential railroad hopper car. 
       FIG. 2  is a schematic side elevational view of a portion of a pressure differential railroad hopper car in accordance with this invention. 
       FIG. 3  is an enlarged side elevational view of the air inlet valve assembly illustrated in  FIG. 2 . 
       FIG. 4  is an enlarged side elevational view of the venturi valve assembly illustrated in  FIG. 2 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to the drawings, there is schematically illustrated in  FIG. 1  a portion of a pressure differential railroad hopper car, indicated generally at  10 , that is conventional in the art. The illustrated railroad hopper car  10  includes a sealed container  11  that is adapted to be filled with a bulk quantity of a material, such as flour or other dry particulate materials, for example. The lower portion of the container  11  is segmented into a plurality (five, for example, as shown) of product discharge sections  11   a . The container  11  can be supported on a pair of spaced apart wheel assemblies (not shown) for facilitating transportation of the railroad hopper car  10  and the material contained therein from one location to another along a railroad line. A standpipe  12  is provided on the container  11  of the railroad hopper car  10 . The standpipe  12  is a hollow tubular member having an upper end that extends within the interior of the container  11  and a lower end that extends out of and below the container  11 . A cap  13  is provided in the upper surface of the container  13  adjacent to the upper end of the standpipe  12 . The cap  13  is removable to provide access to the interior of the container  11  for inspection and cleaning purposes, particularly for cleaning the standpipe  12  when it has become clogged. The lower end of the standpipe  12  has a primary pressure relief valve  15  provided thereon for a purpose that will be explained below. The lower end of the standpipe  12  selectively communicates through a blowdown valve  16  with the atmosphere. A secondary pressure relief valve  17  can be provided on the upper surface of the container  11  for a purpose that will also be explained below. 
   The railroad hopper car  10  also includes a material unloading system that includes an air inlet  20  that is adapted to be connected to a source of pressurized air  20   a , such as a motor driven blower (not shown). The air inlet  20  may be provided with a dust cap or other protective cover structure (not shown) when not in use. The air inlet  20  communicates through a check valve  21  with a main aerator valve  22 . The check valve  21  permits the one-way flow of air from the air inlet  20  to the main aerator valve  22 . The main aerator valve  22  provides selective communication with a main aerator line  23  that extends along most of the length of the railroad hopper car  10 . When the main aerator valve  22  is opened, pressurized air from the source of pressurized air  20   a  can flow therethrough into the main aerator line  23 . When the main aerator valve  22  is closed, pressurized air from the source of pressurized air  20   a  is prevented from flowing therethrough into the main aerator line  23 . 
   The main aerator line  23  selectively communicates through a plurality of individual aerator valves  24  with each of the discharge sections  11   a  of the container  11 . When the individual aerator valves  24  are opened, pressurized air from the main aerator line  23  can flow therethrough into respective aerators (not shown) provided within each of the associated discharge sections  11   a  of the container  11 . When the individual aerator valves  24  are closed, pressurized air from the main aerator line  23  is prevented from flowing therethrough into the associated discharge sections  11   a  of the container  11 . 
   Each of the discharge sections  11   a  of the container  11  selectively communicates through a plurality of individual product discharge valves  25  with a product discharge line  26  that extends along most of the length of the railroad hopper car  10 . When the individual product discharge valves  25  are opened, product contained within the associated discharge sections  11   a  of the container  11  can flow therethrough into the product discharge line  26 . When the individual product discharge valves  25  are closed, product contained within the associated discharge sections  11   a  of the container  11  is prevented from flowing therethrough into the product discharge line  26 . The product discharge line  26  communicates with a product outlet  27  that allows product to flow therethrough out from the railroad hopper car  10 , such as into an external storage facility or another transportation vehicle (not shown). The product outlet  27  is shown in  FIG. 1  in an upwardly facing position, where it is usually maintained for transport. However, the product outlet  27  can be rotated relative to the product discharge line  26  to a sideways or downwardly facing position to unload product from the container  11 . To further facilitate the flow of the product through the product discharge line  26 , the air inlet  20  also communicates through the check valve  21  with a pressure control valve  28  and a check valve  29  with the product discharge line  26 . In the manner described below, this provides additional air flow through the product discharge line  26  to facilitate the movement of the product therethrough. 
   The operation of the material unloading assembly of the railroad hopper car  10  will now be described. Initially, the blowdown valve  16 , the main aerator valve  22 , and all of the individual aerator valves  24  are opened, while each of the individual product discharge valves  25  and the pressure control valve  28  are closed. Then, the source of pressurized air  20   a  is activated to cause pressurized air to flow through the air inlet  20 , the check valve  21 , and the main aerator valve  22  into the main aerator line  23  and each of the discharge sections  11   a  of the container  11 . Initially, some flow of air should be detected from the lower end of the standpipe  12 . If such airflow occurs, then it can be assumed that the standpipe  12  is not undesirably clogged with product. Accordingly, the blowdown valve  16  can then be closed. However, if no airflow occurs from the lower end of the standpipe  12 , then it can be assumed that the standpipe  12  is undesirably clogged with product. In this instance, the source of pressurized air  20   a  should be shut down, and the cap  13  can be removed to facilitate cleaning of the standpipe  12 . 
   Assuming that the standpipe  12  is not clogged, then the blowdown valve  16  is closed. The pressurized air that flows into the discharge sections  11   a  of the container  11  fluidizes the product located in the vicinity of the individual product discharge valves  25  of the discharge sections  11   a . At the same time, the flow of such pressurized air causes the magnitude of the air pressure within the container  11  to increase. A gauge (not shown) is usually provided on the exterior of the container  11  to monitor the magnitude of the air pressure therein. Typically, the air pressure in the container  11  is increased to a relatively high level, such as approximately fourteen p.s.i., for example. The primary pressure relief valve  15  provided on the standpipe  12  and secondary pressure relief valve  17  provided on the container  11  prevent the magnitude of such increased pressure from exceeding a predetermined maximum value. 
   When the magnitude of the air pressure within the container  11  reaches a desired value, the pressure control valve  28  is then opened. As a result, some of the pressurized from the source  20   a  flows through the pressure control valve  28  into the product discharge line  26  and out through the product outlet  27 . Consequently, the magnitude of the air pressure within the container  11  can be maintained at or near a desired value. When it is desired to unload material from the container  11 , one of the individual product discharge valves  25  is opened, while the other individual product discharge valves  25  are left closed. As a result, product contained within the associated discharge section  11   a  of the container  11  can flow through the opened individual product discharge valve  25  into the product discharge line  26 . The flow of product through the product discharge line  26  is facilitated by the flow of air from the air inlet  20  through the check valve  21  and the pressure control valve  28  into the product discharge line  26 . The pressure control valve  28  can be used to regulate the amount of pressurized air that flows into the product discharge line  26 . When the discharge section  11   a  associated with the opened individual product discharge valve  25  is empty, that individual product discharge valve  25  is closed, and the process is repeated for the next individual product discharge valve  25  and associated discharge section  11   a.    
   Referring now to  FIG. 2 , there is schematically illustrated a portion of a pressure differential railroad hopper car, indicated generally at  30 , that is conventional in the art. The illustrated railroad hopper car  30  includes a sealed container  31  that is adapted to be filled with a bulk quantity of a material, such as flour or other dry particulate materials, for example. The lower portion of the container  31  can be segmented into a plurality (five, for example, as shown) of product discharge sections  31   a , although such is not necessary. The container  31  can be supported on a pair of spaced apart wheel assemblies (not shown) for facilitating transportation of the railroad hopper car  30  and the material contained therein from one location to another along a railroad line. Although this invention will be described in the context of the illustrated wheeled railroad hopper car  30 , it will be appreciated that this invention may be used to unload a product from any type of containing structure, regardless of whether it is provided with wheels or other structures for facilitating transportation from one location to another. 
   A standpipe  32  is provided on the container  31  of the railroad hopper car  30 . The standpipe  32  is a hollow tubular member having an upper end that extends within the interior of the container  31  and a lower end that extends out of and below the container  31 . A cap  33  is provided in the upper surface of the container  33  adjacent to the upper end of the standpipe  32 . The cap  33  is removable to provide access to the interior of the container  31  for inspection and cleaning purposes, particularly for cleaning the standpipe  32  when it has become clogged. The lower end of the standpipe  32  has a vacuum relief valve  34  and a primary pressure relief valve  35  provided thereon for purposes that will be explained below. The lower end of the standpipe  32  selectively communicates through a blowdown valve  36  with the atmosphere. A secondary pressure relief valve  37  can be provided on the upper surface of the container  31  for a purpose that will also be explained below. If desired, the vacuum relief valve  34  can be provided on the upper surface of the container  31  in lieu or, or in addition to, the vacuum relief valve  34  provided on the standpipe  32 . 
   The railroad hopper car  30  also includes a material unloading material unloading system that includes a pressurized air inlet  40  that is adapted to be connected to a source of pressurized air (or other fluid)  40   a , such as a motor driven blower (not shown). The pressurized air inlet  40  may be provided with a dust cap or other protective cover structure (not shown) when not in use. The pressurized air inlet  40  communicates with an air inlet valve assembly, indicated generally at  41 . The structure of the air inlet valve assembly  41  is illustrated in detail in  FIG. 3 . As shown therein, the air inlet valve assembly  41  includes a check valve  41   a  that provides for the one-way flow of air from the air inlet  40  to one end of a T-fitting  41   b . The other end of the T-fitting  41   b  is connected to a main aerator line  42  that extends through most of the length of the railroad hopper car  30 . The branch portion of the T-fitting  41   b  selectively communicates through a pressure reducing valve  41   c  with the atmosphere. When the pressure reducing valve  41   c  is opened, air can flow from the check valve  41   a  to the atmosphere. When the pressure reducing valve  41   c  is closed, air is prevented from flowing from the check valve  41   a  to the atmosphere. The purpose for the pressure reducing valve  41   c  will be explained below. 
   The main aerator line  42  selectively communicates through a plurality of individual aerator valves  43  with each of the discharge sections  31   a  of the container  31 . When the individual aerator valves  43  are opened, pressurized air from the main aerator line  42  can flow therethrough into respective aerators (not shown) provided within each of the associated discharge sections  31   a  of the container  31 . When the individual aerator valves  43  are closed, pressurized air from the main aerator line  42  is prevented from flowing therethrough into the associated discharge sections  31   a  of the container  31 . 
   Each of the discharge sections  31   a  of the container  31  selectively communicates through a plurality of individual product discharge valves  44  with a product discharge line  45  that extends along most of the length of the railroad hopper car  30 . When the individual product discharge valves  44  are opened, product contained within the associated discharge sections  31   a  of the container  31  can flow therethrough into the product discharge line  45 . When the individual product discharge valves  44  are closed, product contained within the associated discharge sections  31   a  of the container  31  is prevented from flowing therethrough into the product discharge line  45 . The product discharge line  45  communicates with a product outlet  46  that allows product to flow therethrough out from the railroad hopper car  30 , such as into an external storage facility or another transportation vehicle (not shown). The product outlet  46  is shown in  FIG. 2  in an upwardly facing position, where it is usually maintained for transport. However, the product outlet  46  can be rotated relative to the product discharge line  45  to a sideways or downwardly facing position to unload product from the container  31 . 
   The main aerator line  42  selectively communicates through a pressure control valve  47  with one end of a T-fitting  48 . The other end of the T-fitting  48  communicates through a check valve  49  with an air inlet  50 . The air inlet  50  may be embodied as a hollow cylindrical or tapered member having a screen  50   a  or similar device for restricting the passage of airborne articles therethrough. The check valve  49  permits the one-way flow of air from the air inlet  50  to the T-fitting  48 . The branch of the T-fitting  48  communicates through a check valve  51  with the product outlet line  45 . The check valve  51  permits the one-way flow of air from the T-fitting  48  to the product outlet line  45 . 
   A venturi valve assembly, indicated generally at  52 , is connected between the product outlet  46  and a source of vacuum  53 . The structure of the venturi valve assembly  52  is shown in detail in  FIG. 4 . As shown therein, the venturi valve assembly  52  includes a venturi pipe  52   a  that communicates through a check valve  52   b  with the product outlet  46 . The check valve  52   b  permits the one-way flow of air from the venturi pipe  52   a  to the product outlet  46 . The venturi pipe  52   a  may be provided with a dust cap or other protective cover structure  52   c  when not in use. The purpose for the venturi valve assembly  52  will be explained below. 
   The operation of the material unloading assembly of the railroad hopper car  30  will now be described. Initially, the blowdown valve  36  and all of the individual aerator valves  43  are opened, while the pressure reducing valve  41   a  of the air inlet valve assembly  41 , each of the individual product discharge valves  44 , and the pressure control valve  47  are closed. Then, the source of pressurized air  40   a  is activated to cause pressurized air to flow through the check valve  41   a  and the T-fitting  41   b  of the air inlet valve assembly  41  into the main aerator line  42  and each of the discharge sections  31   a  of the container  31 . Initially, some flow of air should be detected from the lower end of the standpipe  32 . If such airflow occurs, then it can be assumed that the standpipe  32  is not undesirably clogged with product. Accordingly, the blowdown valve  36  can then be closed. However, if no airflow occurs from the lower end of the standpipe  32 , then it can be assumed that the standpipe  32  is undesirably clogged with product. In this instance, the source of pressurized air  40   a  should be shut down, and the cap  33  can be removed to facilitate cleaning of the standpipe  32 . 
   Assuming that the standpipe  32  is not clogged, then the blowdown valve  36  is closed. The pressurized air that flows into the discharge sections  31   a  of the container  31  fluidizes the product located in the vicinity of the individual product discharge valves  44  of the discharge sections  31   a . At the same time, the flow of such pressurized air causes the magnitude of the air pressure within the container  31  to increase. A gauge (not shown) is usually provided on the exterior of the container  31  to monitor the magnitude of the air pressure therein. Unlike the conventional embodiment described above, the air pressure in the container  31  is increased to a relatively low level, such as approximately two to three p.s.i., for example. The primary pressure relief valve  35  provided on the standpipe  32  and secondary pressure relief valve  37  provided on the container  31  prevent the magnitude of such increased pressure from exceeding a predetermined maximum value. 
   At the same time that the source of pressurized air  40   a  is activated, the source of vacuum  53  can be activated as well to evacuate the product discharge line  45  through the venturi valve assembly  52 . When this occurs, air from the atmosphere is drawn in through the air inlet  50  and the check valve  51  to the product discharge line  45 . However, because all of the individual product discharge valves  44  are closed, no product is moved through the product discharge line  45 . 
   When the magnitude of the air pressure within the container  31  reaches a desired value, the pressure control valve  47  is then opened. For reasons that will be explained below, the pressure control valve  47  is preferably opened only partially to a relatively small amount of the pressurized air in the main aerator line  42  to flow through the T-fitting  48  and the check valve  51  into the product discharge line  45 . Thus, some of the pressurized from the source  40   a  flows through the product discharge line  45  and out through the product outlet  46  and the venturi valve assembly  52 . Consequently, the magnitude of the air pressure within the container  31  can be maintained at or near a desired value. If necessary, the magnitude of the air pressure within the container  31  can also be adjusted by selectively opening the pressure reducing valve  41   c  of the air inlet valve assembly  41 . 
   When it is desired to unload material from the container  31 , one of the individual product discharge valves  44  is opened, while the other individual product discharge valves  44  are left closed. As a result, product contained within the associated discharge section  31   a  of the container  31  can flow through the opened individual product discharge valve  44  into the product discharge line  45 . The pressurized air generated by the source  40   a  functions to accomplish two objectives. First, some of the pressurized air generated by the source  40   a  is supplied through the individual aerator valves  43  to the interior of the container  31  for the purpose of fluidizing the product located in the vicinity of the individual product discharge valves  44  of the discharge sections  31   a . This facilitates the flow of product through the opened individual product discharge valve  44  and minimizes the occurrence of coalescence and adherence of the product to the interior of the container  31 . 
   Second, some of the pressurized air generated by the source  40   a  is supplied through the pressure control valve  47 , the T-fitting  48 , and the check valve  51  to the product discharge line  45  for the purpose of moving the product through the product discharge line  45  to the product outlet  46  (the check valve  49  prevents such pressurized air from escaping through the air inlet  50 ). The magnitude of the pressurized air generated by the source  40   a  need only be relatively small (two to three p.s.i., for example, as mentioned above) to accomplish both of these purposes. Once the product has been moved to the product outlet  46 , the vacuum generated by the source  53  draws the product therefrom. The venturi valve assembly  52  allows air from the atmosphere to be drawn therein to be mixed with the product to facilitate the flow of the product outwardly from the product outlet  46 . When the discharge section  31   a  associated with the opened individual product discharge valve  44  is empty, that individual product discharge valve  44  is closed, and the process is repeated for the next individual product discharge valve  44  and associated discharge section  31   a.    
   The magnitude of the pressurized air generated by the source  40   a  and the magnitude of the vacuum generated by the source  53  often varies from location to location when unloading the railroad hopper car  30 . Typically, one or more gauges (not shown) are provided at the unloading location for allowing the unloading of the product to occur at a rate that is optimal with the magnitude of the pressurized air generated by the source  40   a  and the magnitude of the vacuum generated by the source  53 . The pressure reducing valve  41   c  of the air inlet valve assembly  41  and the pressure control valve  47  can be adjusted during the unloading process to accommodate these varying pressurized air and vacuum conditions. Also, during the unloading process, it may be desirable to vary the magnitude of the pressurized air generated by the source  40   a  and the magnitude of the vacuum generated by the source  53 . For example, the farther the individual product discharge valve  44  is located from the product outlet  46 , the greater amount of pressurized air will be required to move the product through the product outlet line  45 . Thus, adjustment of the various valves discussed above may be desirable to maintain optimum flow of product. 
   As mentioned above, the vacuum relief valve  34  is provided on the lower end of the standpipe  32 . The vacuum relief valve  34  is provided to allow air to be drawn within the interior of the container  31  if, for some reason, the magnitude of the air pressure therein drops below a predetermined amount. Typically, the container  31  is designed to withstand relatively high pressures therein, such as the approximately fourteen p.s.i. discussed above in connection with the conventional container  11 . However, such containers  31  are not usually designed to withstand negative pressures of significant magnitude. Such a negative pressure situation could occur if, for example, the person operating the material unloading system improperly adjusted the positions of the various valves discussed above. In that instance, the vacuum relief valve  34  would allow air to be drawn within the interior of the container  31  and prevent the magnitude of the air pressure therein from dropping below a predetermined amount. 
   It will be appreciated that the material unloading system of this invention is readily retrofit onto an otherwise conventional pressure differential railroad hopper car. If desired, the railroad hopper car  30  of this invention can be unloaded using the same pressure differential method described above in connection with the conventional railroad hopper car  10 . Thus, this invention provides maximum flexibility for use at unloading locations having both types of systems. Furthermore, the material unloading system of this invention can be retrofit onto other types of pressure differential railroad hopper cars than as specifically shown in  FIG. 1 . 
   In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.