Abstract:
A pneumatic conveying apparatus, having a conveyor line path installed with a first valve and a second valve. An article is conveyed through the conveyor line path. The first and second valves are both open to a vacuum source to provide a sucking force to the article, so as to initiate conveying the article. After a flow of the article through the whole conveyor line path is established, the second valve is closed to form an air cushion at the terminal end of the conveyor line path. The terminal velocity of the article is thus reduced without causing any damage or breakage.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    (Not Applicable)  
         STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT  
         [0002]    (Not Applicable)  
         BACKGROUND OF THE INVENTION  
         [0003]    The present invention relates generally to conveying apparatus, and more particularly to a pneumatic conveying apparatus that rapidly conveys products while safely reducing the terminal velocity of the product to avoid damaging the same.  
           [0004]    Mechanical conveyors have been commonly used for transporting articles. However, such prior art mechanical conveyers are costly, possess substantial product contamination concerns and often time damage fragile product such as cereals and/or coffee beans.  
           [0005]    To address the problems of mechanical conveyors, pneumatic conveyors have heretofor been developed. In conventional pneumatic conveyors, product is conveyed in a pipe or conduit via air, i.e., vacuum. Articles to be conveyed in such pneumatic systems require a sufficient initial velocity to prevent product dropout during conveyance; yet, the terminal velocity of the articles must be reduced to prevent product damage and degradation.  
           [0006]    The prior art mechanisms for reducing the terminal velocity of the articles under pneumatic conveyance typically comprise using a cyclone or alternatively gradually increasing conduit/line size through the conveyance path. In a cyclone, mechanical frictional deceleration often causes the article to break and become damaged. By gradually increasing the line size, the articles often time drop out causing the conveyor line to plug.  
           [0007]    As such, there exists a substantial need in the art for an improved pneumatic conveyor system that safely conveys fragile product without damage and eliminate product drop out during transport.  
         SUMMARY OF THE INVENTION  
         [0008]    To obtain a fluent conveyance of articles without breakage or damage, the present invention provides a pneumatic conveying apparatus having a unique terminal velocity dissipater. Instead of using the prior art mechanical decelerating methods such as a cyclone or gradually increasing the line size for the articles under conveyance, the present invention utilizes a pressure gradient (dead) air cushion formed at the terminal end of the conveyor. Traveling through the air cushion, the velocity of the articles is rapidly reduced without substantially physical impact or friction thereby significantly reducing damage or breakage of the articles being conveyed.  
           [0009]    In the preferred embodiment of the invention, the pneumatic conveying apparatus comprises two valves installed along the conveyor line path for the articles to be conveyed. Both valves are initially opened to a pressure source to allow a high initial force to be applied to the product to initiate flow and ensure against product dropout thereby establishing a steady product flow from the entrance to the exit of the conveyor line path. Subsequently, a second one of the valves is closed, or supplied with a reduced pressure or a pressure in an inverse direction, to the initial pressure to establish a dead air space at a terminal end of the conveyor line path while maintaining sufficient inertia and velocity to continue product flow toward the terminal end of the conveyor line path. The articles flowing from the open valve to the terminal end of the conveyor line path experience a draw back pressure gradient due to the vacuum supplied by the open valve; that is, a (dead) air cushion formed between the open valve and the exit of the line path to cause a controlled and dampened deceleration of the articles at the terminal end of the line path.  
           [0010]    In the above embodiment, as the articles are not decelerated by any frictional force or physical contact, damage or breakage of the articles is prevented with articles conveyed with velocities of about 8000 ft/min to about 9000 ft/min in a conveyor line path having a length of about 200 ft to about 300 ft.  
           [0011]    In another embodiment of the present invention, only one valve is installed on the conveyor line path. By suppying a pressure to the conveyor line path via the valve, the product is drawn into the conveyor line path and accelerated to a required velocity. After a steady state flow of the product is established, the pressure is adjusted to a magnitude to form a gradient pressure at a terminal end of the conveyor line path. The terminal velocity of the product is thus retarded by the gradient pressure while a sufficient internia and velocity is maintained to continue product flow towards the terminal end.  
           [0012]    A container is further provided to connect with the exit of the conveyor line path. The container is so designed that the article entering therein is directed tangentially about an inside diameter thereof. Preferably, the flow velocity of the articles is monitored to determine the timing for closing the second one of the valves adjacent the terminal end of the conveyor line path, to ensure that the product flows within the conveyor at sufficient velocity to prevent product dropout yet avoid product damage heretofore occurring at the terminal end of the conduit line. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    These, as well as other features of the present invention, will become more apparent upon reference to the drawings wherein:  
         [0014]    [0014]FIG. 1 shows the pneumatic conveying apparatus according to the invention; and  
         [0015]    [0015]FIG. 2 shows flow of the articles under conveyance; and  
         [0016]    [0016]FIG. 3 shows the back flow of the articles under conveyance caused by closing one of the valves in the pneumatic conveying apparatus. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]    [0017]FIG. 1 shows the pneumatic conveying apparatus  10  of the present invention, which conveys articles/product  200  (FIG. 2) from a source container  12  to a destination container  14  through a conveyor line path  100 . Along the conveyor line path  100  of the pneumatic conveying apparatus  10 , a pair of valves  16  and  18  are installed which are preferably connected to a suitable common vacuum source indicated schematically by the arrows in FIG. 1. The conveyor line path  100  comprises a conduit  102   a , a conduit  102   b  and a vessel  102   c . The conduit  102   a  connects between the source container  12  and the valve  16 . The conduit  102   b  extends from the valve  16  to a top portion of the vessel  102   c . A bottom portion of the vessel  102   c  connects to the destination container  14 .  
         [0018]    As shown, the valves  16  and  18  are preferably disposed upon the conveyor path  100 , with valve  16  being located upstream of the terminal end of the conveyor path while valve  18  is disposed just downline of the terminal end of the conveyor path. Valve  18  is preferably disposed adjacent the upper end of the vessel  102   c , while valve  16  is preferably installed adjacent the upper portion of vessel  103 . As best shown in FIG. 2, a pair of conventional filters  110  are provided in the upper portion of the vessels  102   c  and  103  which allow air flow through the filters  110  and valves  16  and  18  while preventing product or article flow there across. As such, upon opening of the valves  16  and  18  to the vacuum source, the articles conveyed within the conveyor line  100  and its portions  102   a ,  102   b  and  102   c  are exposed to vacuum pressure through the valves  16  and  18  but are prevented from traveling into the vacuum source via the filters  110 .  
         [0019]    The exit container  102   c  is preferably designed with a configuration such that the product entering thereto is directed tangentially about the inside diameter thereof. Such design includes a hopper configuration with the inlet opening  112  oriented tangentially with the inside diameter, for example. It will be appreciated to the people of ordinary skill in the art that a container with other configuration resulting in the same effect is also applicable for the exit container  102   c . The lower portion of the vessel  102   c  preferably includes an articulating gate  206  which may be selectively opened or closed, as desired, to allow product  200  contained within the vessel  102   c  to be selectively dropped via gravity force into the destination vessel  14 .  
         [0020]    With the structure defined, the operation of the improved pneumatic conveyor system  10  of the present invention may be described. To initiate article/product flow within the conveyor line  100  from the source container  12  to the destination container  14 , both valves  16  and  18  are initially opened such that a maximum vacuum source is provided within the interior of the entire conduit line  100 . Upon encountering this large vacuum source, product is rapidly accelerated within the conveyor line  102   a  from the source container  12  and transported within the interior of the conduit line  102   a ,  102   b  and into the exit container  102   c . During this initial product transport, sufficient vacuum is maintained within the entire length of the conduit line  100 , such that articles within the line have sufficient velocity to maintain a generally steady state flow and thereby avoid product dropout occurring within the conduit line  100 .  
         [0021]    After obtaining this generally steady state initial flow, the downline valve  18  is closed such that the only vacuum source transporting articles within the conduit line  100  is applied through the upstream valve  16 . As best shown in FIG. 3, the closing of the valve  18  while maintaining the valve  16  opened, causes upstream air  300  to be pulled through the conveyor section  102   a , while downstream air  302  existing within conduits section  102   b  and the interior of the vessel  102   c  to additionally be drawn back toward the valve  16  as indicated by the arrows in FIG. 3. As previously mentioned, due to filter element  110 , upstream air  300  and downstream air  302  pass through the filter  110  while product contained remains within the conveyor system. By drawing back the downline air flow  302  from the interior of conduit  102   b  and vessel  102   c , a pressure gradient exists on opposite side of the valve  16  with the conveyor line forming a dead air space which is established within the interior of the container  102   c  and conveyor  102   b . The pressure gradient/dead air space applies a pneumatic deceleration force or air cushion which rapidly decelerates the articles once they have passed the valve  16 . Preferably, by proper sizing of the valve  16  along with the diameter of the conveyor section  102   b  and length thereof, the terminal velocity of particles entering into the vessel  102   c  can be maintained within suitable limits such that the exit velocity of particles into the container  102   c  is substantially zero and the same can fall via gravity force into the lower hopper portion  202  of the vessel  102   c . Additionally, those skilled in the art will recognize that the vacuum source applied to the conveyor section  102   a  through valve  16  is preferably adjusted such that sufficient vacuum is applied to the articles to prevent product dropout.  
         [0022]    In the above embodiment, the articles  200  are conveyed with a sufficiently high flow velocity, yet, with a sufficiently low terminal velocity to avoid damage or breakage. The structure allows conveying articles through a conveyor line path of about 200 ft to about 300 ft with a velocity of about 8000 ft/min to about 9000 ft/min. The velocity of the conveyance can be monitored by many ways, for example, by installing a flow meter or visual observation or the article removal rate from the source container, or accumulation rate in the destination container.  
         [0023]    Further, the conduits  102   a  and  102   b  can be made from a single conduit, or by assembling several parts together. The magnitude of vacuum provided by the valve  16  and the valve  18  can be adjusted individually as required.  
         [0024]    The valves  16  and  18  in the above embodiment can also be connected to a pressure source or a pressure pump other than a vacuum source. By controlling the pressure supplied to the convey line path  100  via the valves  16  and  18 , the same objective can be achieved. For example, a pressure is applied to both valves  16  and  18  to accelerate the product and draw the product into the conveyor line path  100  initially. Again, the initial pressure is sufficiently high to avoid any dropout of the product. After a steady flow of the product is obtained, the pressure applied to the valve  18  is reduced, terminated or supplied in an inverse direction, such that a dead air space is formed in the terminal end of the conveyor line path  100 . Consequently, the terminal velocity of the product is reduced, while a sufficient inertia and velocity is maintained for the product to flow from the source container  12  to the terminal end. In addition, the pressure supplied via the valve  16  can also be adjusted while the pressure supplied via the valve  18  is altered.  
         [0025]    Alternatively, only one valve is installed on the conveyor line path instead of incorporating two valves. An initial pressure is supplied to the conveyor line path via the valve until a steady state flow of the product is obtained. The initial pressure is sufficiently to avoid any dropout of the product. While reaching a steady state flow of the product, the pressure supplied via the valve is adjusted to a magnitude allowing a pressure gradient formed in a terminal end of the conveyor line path.  
         [0026]    Indeed, each of the features and embodiments described herein can be used by itself, or in combination with one or more of other features and embodiment. Thus, the invention is not limited by the illustrated embodiment but is to be defined by the following claims when read in the broadest reasonable manner to preserve the validity of the claims.