Abstract:
A material return system of a material collection system and appertaining method permits fine material collected in a fine material collector to be returned to a main debris tank by taking advantage of the venturi effect, thus permitting a relatively trouble-free operation of the material collection system.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The invention relates to a material return system of a material collection system that uses the venturi effect to flush fine material back into a collection vessel.  
           [0003]    2. Description of the Related Art  
           [0004]    Various systems have been designed to collect bulk materials into a storage receptacle using a vacuum. Most bulk materials comprise a wide range of particle sizes from large/coarse to fine. One of the known problems is that when collecting material having this wide range of particle sizes, it is difficult to contain the fine material because of its tendency to be disturbed and blown around by the forces on the air exerted by the vacuum. These fine materials can, over time, collect in undesirable locations and prevent proper operation of the system  
           [0005]    The traditional way of returning the fine materials or carry over from the process of vacuuming dense bulk materials into a vacuum collection vessel or debris tank is to use mechanical devices such as augers, conveyers or other mechanisms to hold the fine material in a collection chamber, bag house or dump tubes that have to be mechanically empted/dumped when the debris tank is full. Vacuum sealing of augers, conveyers and dump tubes are high maintenance items. Since the tubes can only be dumped after the material is transported to a dump site, the material settles and packs during transport and requires vibrators or manual cleaning to clean out the tubes or bag houses. In order to prevent an accumulation of this fine material that would preclude operation of the system, frequent inefficient stops may be needed to empty the fine material.  
           [0006]    U.S. Pat. No. 4,227,893 discloses an auger used for mechanically returning fine materials to the bulk collection portion of the debris tank, however the auger represents a mechanical apparatus that increases the system complexity and introduces costs to the system.  
           [0007]    U.S. Pat. No. 4,017,281 discloses a material collection system in which the fine material is collected from a dust collecting chamber by a pipe connected to a door/port and relies exclusively on a pressure differential between the dust collection chamber and the hopper to remove the fine material. Since the pressure differential is of concern for performing an effective job, this differential must be maximized in order to maximize the cleanout of the dust collecting chamber. This results in a nonoptimized solution.  
         SUMMARY OF THE INVENTION  
         [0008]    The object of the present invention is to provide a more effective and simpler to operate system and method for collecting and returning fine material back into a main debris tank based on the venturi effect. This system may be used in a pneumatic/vacuum conveying device that may be skid mounted, on mobile truck mounted trailer mount or in plant system using a collection vessel, and comprises a separator or bag house that returns the fine materials or liquids to the collection vessel while continuing to convey bulk materials into the collection vessel. The system is designed to automatically return fine materials or liquids separated and/or filtered from the air that is pneumatically conveying dense materials into a collection vessel, vacuum box, debris collection tank or container.  
           [0009]    The object of the invention is achieved by providing a valve under the bag house or separator having a small fine material collection vessel that is located under the valve in which fine materials or liquids can be collected. When the fine material collection vessel is full, a bag house valve is closed. A venturi tube is present which is mounted under the fine material collection vessel and connected to the top of the debris tank. When the venturi valve is momentarily opened to atmosphere, the vacuum in the debris tank and atmospheric air rush through the venturi tube and induct the fine materials into the air stream and back into the debris tank. The venture valve is then closed and the bag house valve is opened allowing the process to be repeated as often as necessary during the operation of the vacuum conveying device. The process of returning the fine materials or liquids to the debris tank happens so quickly that the bulk material being pneumatically conveyed into the debris tank are not affected, and there is no loss of production while cleaning the bag house or separator. All material from the fine material collection vessel is transported in the debris tank. The above procedure may be made automatic by the addition of a programmable control, sequence valves and/or timers.  
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a pictorial diagram illustrating the inventive system and method; and  
         [0011]    [0011]FIG. 2 is a flowchart illustrating the inventive method. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0012]    According to an embodiment of the invention shown in FIG. 1, a material collection system  10  uses suction to vacuum up bulk material using an intake hose  12 . The bulk material enters a debris tank (bulk material collector body)  14  via a bulk material inlet  13 . The heavier collected bulk material  16  generally settles in the bottom of the debris tank  14  where, after some amount has collected there, the debris tank  14  is emptied.  
         [0013]    Air and fine material  18  exit the debris tank  14  vial a debris tank exit vent  20  and enter a baghouse separator  22  (fines filtration) that filters the fine material from the air. There may be more than one separator  22 , and an embodiment of the invention has two side-by-side separators, although more may be used where practical. The baghouse separator  22  may utilize centrifugal mechanisms to perform the separation, but any known mechanism may be used. Filtered air exits the baghouse separator  22  through a baghouse exit vent  26  from which the filtered air  27  is provided to a blower or vacuum source (not shown). The fine material may collect on the filters  24  and, optionally, filter shaker that may be an air cannon or any type of air pulsing mechanism or even a mechanical shaker  30  may be used to dislodge fine material from the filters  24 . The air cannon  30  may operate by blasting air into the filters, and the energy from the blast causes the dislodging. This air canon pulsing may take place prior to the operation of the return of fine material back to the debris tank  14  to help ensure that the filters  24  are clean. The fine material collects in the bottom of the fine material collector  28  where it accumulates up to some predefined amount or for some predetermined period of time.  
         [0014]    After some predetermined period of time has elapsed or after some predefined amount of fine material collected, the fine material is sent back into the debris tank  14  as follows. A baghouse valve  32  is closed. This closure prevents two things: first, it prevents additional material from accumulating into the fine material collector  28  from the baghouse separator  22 , but second, and more importantly, it prevents any material and air from going from the fine material collector  28  back up into the baghouse separator  22 .  
         [0015]    Once the baghouse valve  32  is closed, a venturi valve  35  is opened letting air from the atmosphere in past a fine material collector atmospheric air inlet  34 . Advantageously, this may be operated while the bulk material is being vacuumed via the hose  12 , although it is also possible to seal the debris tank off when the fine material is being collected. This air is drawn into the debris tank  14  by the vacuum created within this tank. The air moves through the air inlet  34  and past a venturi tube  37  that is connected to the air inlet by an airtight conduit, the venturi tube  37  being located directly below the fine material collector  28 . The air then moves past a fines collector exhaust vent  36  and through a fines collector material return conduit  38  and into the debris tank  14  via a debris tank fine material inlet  40 . Given the long distance that the fine material must travel, most of it settles into the debris tank  14 —in general, the air in the debris tank is moving at a relatively slow speed that permits the fine material to settle out.  
         [0016]    The fine material is pulled from the fine material collector by the venturi effect. This effect is based on the concept that as the speed of a moving fluid (liquid or gas) increases, the pressure within that fluid decreases. This principle states that the total energy in a steadily flowing fluid system is a constant along a flow path. This implies that an increase in the speed of the fluid must therefore be matched by a decrease in its pressure. As the air streams past an opening in the bottom of the fine material collector  28  in the venturi tube  37 , a vacuum is created that pulls the fine material into the venturi tube  37  so that it is carried along by the air into the debris tank  14 . This is also assisted by the force of gravity. The inventive use of the venturi system to transfer fine material back to the debris tank  14  permits a simple solution to a problem with material collection systems. When such a system utilizes automated valve operations, the system can result in significant reduced effort for operating such collection systems. When side-by-side baghouse separators  22  are used (not shown), the sequence can be run concurrently for all separators  22 , run sequentially, or in any other manner.  
         [0017]    As noted above, the sequencing may be triggered by a timer that triggers the sequence to operate on some periodic interval. This periodic interval could be determined based on the type of material being vacuumed, possibly including the material&#39;s propensity to produce fine particles, the physical amount of material in a particular area, etc. Alternately, a sensor  39  may be provided that detects an amount of accumulated fine material. The sensor should be located appropriately so that it can detect the accumulated fine material. The sensor could utilize some form of light emitter/detector pair or an acoustic mechanism or some form of proximity detector, pressure sensor, mass/weight measuring device, float, or other known mechanism. A simplified embodiment of the system may not require an automated system, but rather could be operated by a button conveniently located for manual operation.  
         [0018]    In an exemplary embodiment, the baghouse valve  32  may be, e.g., approximately 8″ in diameter, and the venturi valve may be 3″ in diameter. The valves themselves may utilize a butterfly valve or any other type of valve that can produce an airtight seal. The valves can be controlled pneumatically, electrically with solenoids, or via any other type of know control mechanism.  
         [0019]    The flowchart in FIG. 2 highlights an embodiment of the inventive method  100  that, in a basic illustration, involves connecting the fine material collector to the baghouse separator  22 ,  102 . The venturi tube  37  is connected to the fine material collector  104  and to the debris tank  14 ,  106 . In operation, and air stream is provided through the venture tube  37 ,  108  which blows the fine material back into the debris tank  14 .  
         [0020]    For the purposes of promoting an understanding of the principles of the invention, reference has been made to the preferred embodiments illustrated in the drawings, and specific language has been used to describe these embodiments. However, no limitation of the scope of the invention is intended by this specific language, and the invention should be construed to encompass all embodiments that would normally occur to one of ordinary skill in the art.  
         [0021]    The present invention may be described in terms of functional block components and various processing steps. Such functional blocks may be realized by any number of hardware and/or software components configured to perform the specified functions. Furthermore, the present invention could employ any number of conventional techniques for hardware configuration, electronics configuration, control technology, data processing and the like.  
         [0022]    The particular implementations shown and described herein are illustrative examples of the invention and are not intended to otherwise limit the scope of the invention in any way. For the sake of brevity, conventional electronics, control systems, and other functional aspects of the systems (and components of the individual operating components of the systems) may not be described in detail. Furthermore, the connecting lines, or connectors shown in the various figures presented are intended to represent exemplary functional relationships and/or physical or logical couplings between the various elements. It should be noted that many alternative or additional functional relationships, physical connections or logical connections may be present in a practical device. Moreover, no item or component is essential to the practice of the invention unless the element is specifically described as “essential” or “critical”. Numerous modifications and adaptations will be readily apparent to those skilled in this art without departing from the spirit and scope of the present invention.  
         [0023]    List of Reference Characters  
         [0024]    [0024] 10  material collection system  
         [0025]    [0025] 12  intake hose  
         [0026]    [0026] 13  debris tank bulk material inlet  
         [0027]    [0027] 14  debris tank/bulk material collector body  
         [0028]    [0028] 16  collected bulk material  
         [0029]    [0029] 18  fines/fine collected material  
         [0030]    [0030] 20  debris tank exit vent  
         [0031]    [0031] 22  fines filtration/baghouse separator  
         [0032]    [0032] 24  filters  
         [0033]    [0033] 26  baghouse exit vent  
         [0034]    [0034] 27  filtered air to blower  
         [0035]    [0035] 28  fine material collector  
         [0036]    [0036] 30  air cannon pulsing mechanism  
         [0037]    [0037] 32  baghouse valve  
         [0038]    [0038] 34  fine material collector atmospheric air inlet  
         [0039]    [0039] 35  venturi valve  
         [0040]    [0040] 36  fine material collector exhaust vent  
         [0041]    [0041] 37  venturi tube  
         [0042]    [0042] 38  fine collector fine material return conduit  
         [0043]    [0043] 39  sensor  
         [0044]    [0044] 40  debris tank fine material inlet  
         [0045]    [0045] 42  transport safety valve