Abstract:
An installation and method for rapidly and efficiently unloading material from bulk bags in an unloading station surrounded by an air lock enclosure while the bags move suspended from a closed look conveyer in continuous progress from a loading station to said unloading station then through a bag dumping station. The material is dumped on an air slide and directed into a trough from which it is conveyed to a temporary tank before being repackaged in smaller containers or otherwise distributed.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to bulk material handling equipment and more specifically to bulk bag emptying and discharging systems. 
       BACKGROUND 
       [0002]    Powder and granular materials such as salt, sugar, rice, flour, cement, aggregates, detergents, skimmed milk are commonly carried in so-called “bulk bags” made of synthetic fabric with a moisture-proof liner. The typical capacity of such bags varies from 1 cubic meter (35 cubic feet) to 4 cubic meters (140 cubic feet). They usually weigh from 1 to 2 metric tons. The whole process of conveying a bag and lowering it into the discharging device, opening and shaking the bag, then removing and disposing of the emptied bag is time consuming and labor extensive. As the use of bulk bags in transportation becomes prevalent in many industries, there appears to be a need for a more rapid and more cost effective way of unloading bulk bags. For example, Portland cement which used to be processed at limestone and chalk quarries relatively close to use or distribution centers is now manufactured halfway around the globe in countries like the Peoples Republic of China, shipped in bulk bags on cargo ships then repackaged in small bags or otherwise distributed domestically. Concrete aggregates, coal and other such commodities are similarly handled in large numbers of bulk bags. 
         [0003]    The invention results from attempts to expedite the discharging of bulk bags and reduce the cost of the labor involved in such a process. 
       SUMMARY 
       [0004]    Bulk bags are automatically picked up one by one by an overhead closed loop conveyer at a loading station, then carried to a bag unloading station where a lower portion of the bag is ripped open allowing its contents to be dumped into a gathering facility that carries the material into a temporary storage tank from which it can be either repackaged into smaller containers or otherwise disposed of. 
         [0005]    After ripping off the lower portion, each bag is driven by the conveyer into momentary bumping contacts with barriers in order to dislodge any remaining contents. The empty bags are then carried by the conveyer to another station where they are dumped for disposal. The various operations are conducted while the bags are passing through the various stations in a continuous process. The unloading station and material gathering facilities are contained in an airlock enclosure which prevents escape of vapors or dust particles. 
         [0006]    The installation for unloading material from bulk bags, gathering said unloaded material and conveying it to a storage tank comprises a bag loading station (BLS), a bag unloading station (BUS), an empty bag dumping station (BDS), a closed loop conveyer (CLC) for transporting said bags along a closed circuit path from said BLS, through said BUS and to said BDS, at the BUS, a bag ripping means (BRM) and a material gathering facility (MGF); wherein said bags are loaded, emptied and dumped as they successively enter said stations. 
         [0007]    The BRM comprises at least one tool sized and positioned to come in ripping contact with a lower portion of each bag, and the tool comprises a rotating sawing blade having a vertically adjustable support. 
         [0008]    The BUS further comprises a bag shaking device (BSD) including at least one barrier sized and positioned to momentarily contact said bags as they move past the tool. 
         [0009]    The BSD comprises a plurality of said barriers disposed at a different heights at spaced apart intervals along said path. 
         [0010]    The BUS further comprises an airlock enclosure. 
         [0011]    The MGF comprises a material collecting pit and means for moving material from said pit to said storage tank. 
         [0012]    The pit comprises a slide under said tool and said BSD, a trough at the end of the slide and, means for conveying material out of said trough to the tank. 
         [0013]    The installation may also comprise a bag loading station (BLS), a bag unloading station (BUS), an empty bag dumping station (BDS), a closed loop conveyer (CLC) for transporting said bags along a closed circuit path from said BLS, through said BUS and to said BDS, in said BUS, a bag ripping means (BRM) and a material gathering facility (MGF), wherein said bags are loaded, emptied and dumped as they continuously move through said stations, and said BRM comprises at least one tool sized and positioned to come in ripping contact with a lower portion of each of said bags. 
         [0014]    The BLS comprises means for lifting the bags according to their sizes for ease or attachment to said conveyor. 
         [0015]    The tool comprises at least two rotating sawing blades positioned astride said lower portion. 
         [0016]    The BUS further comprises a bag shaking device (BSD) including at least one barrier sized and positioned to momentarily contact the bags as they move past said tool. 
         [0017]    The BSD further comprises a plurality of said barriers disposed at a different heights at spaced apart intervals along said path. 
         [0018]    The storage tank comprises a silo having a plurality of delivery chutes. 
         [0019]    The BUS further comprises an airlock enclosure and means for maintaining a negative air pressure within the enclosure. 
         [0020]    The MGF comprises a material collecting pit and means for moving material from the pit to the silo. 
         [0021]    The pit comprises an air slide under said tool and the BSD, a trough at the end of the slide, and means for conveying material out of the trough to the silo. 
         [0022]    The method for emptying contents of bulk bags comprises, at a bag loading station (BLS), loading said bags on closed loop conveyer passing through a bag unloading station (BUS) and a bag dumping station (BDS); at the BUS, ripping open a lower portion of said bags to unload said contents into a material gathering facility (MGF); at the BDS, removing the bags from the conveyer; performing said steps during continuous progress of the conveyer through the stations, moving said material from the MGF to a storage tank, and performing said step of ripping in an enclosure, and maintaining a negative air pressure inside the enclosure. 
         [0023]    The step of ripping comprises cutting a slit through said lower portion with a rotating blade positioned in the path of the bags. 
         [0024]    The method further comprises shaking the bags after ripping in the enclosure. 
         [0025]    The method further comprises dispensing material out of the tank to a plurality of means such as a repackaging plant, a concrete mixer, or a bulk carrier. 
     
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0026]      FIG. 1  is a diagrammatical illustration of the entire bulk bag discharger installation according to the invention; 
           [0027]      FIG. 2  is a perspective view of a bulk bag equipped with a cross-hanger; 
           [0028]      FIG. 3  is a partial side view of the conveyer, trolley and bag suspending hook; 
           [0029]      FIG. 4  is an illustration of the bag loading station; 
           [0030]      FIG. 5  is a top diagrammatical view of the bag unloading station; 
           [0031]      FIG. 6  is a side diagrammatical view thereof; 
           [0032]      FIG. 7  is a partial, cross-sectional view of the bag unloading station; 
           [0033]      FIG. 8  is a side view of the bag unhooking operation; and 
           [0034]      FIG. 9  is a diagrammatical view of the temporary storage facility. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0035]    Referring now to the drawing there is diagrammatically illustrated in  FIG. 1  a bulk bag discharging installation  1  which comprises an overhead closed loop conveyer (CLC)  2  passing through a bag loading station (BLS)  3 , a bag unloading station (BUS)  4  and a bag dumping station (BDS)  5 . The CLC operates continuously and automatically picks up loaded bulk bags  6  that are sequentially fed to the conveyer, and transports them to the BUS  4 . 
         [0036]    The BUS  4  is surrounded by an airtight enclosure  7  into which is maintained a negative pressure in order to prevent escape of dust particles or vapors into the surroundings. In the BUS, the bags are contacted by a bag ripping means (BRM)  8  which cuts a slit in the lower portion of each bag causing its contents to drop into a material gathering facility (MGF)  9 . The bags are then dragged by the conveyer against a bag shaking device (BSD)  10  in order to dislodge any material remaining therein. The conveyer then moves the empty bag  11  to the BDS  5  where it is automatically detached from the conveyer and dumped for disposal. The MGF comprises a pit that lies under the BRM and BSD and the material gathered therein is fed to an extractor (EXT), that is a pump, Archimedes screw or other apparatus  12  for moving the material into a storage tank or silo  13  from which it is later packaged in smaller containers or otherwise distributed. The EXT  12 , depending upon its construction, may be within or without the enclosure  7 . 
         [0037]    As shown on  FIG. 2 , bulk bags are usually provided with a lifting loop  14  at each of the four upper corners or with a stevadoring strap  15  spanning the median portion of two opposite rim sides, and sometimes with both corner loops and strap. In order to facilitate the handling and discharging of the bags, each one is equipped with a cross-hanger  16  having each of its four arms engaging one of the corner loops  14 . A ring  17  at the top of the vertical central shank  18  is sized to be engaged by one of the hooks  19  hanging from the overhead conveyer  2  as illustrated in  FIG. 3 . The hook is rotatively and swivelingly attached to a trolley  20 . The trolley is suspended from a pair of roller bearings  21  riding in the conveyer track  22 . The trolley is also linked to the conveyer driving chain  23 . 
         [0038]    At the BLS, the bulk bags  6 , filled with material  6   a  are fed over a roller mat  24  to an hydraulic lift  25  positioned under the conveyer  2  as shown in  FIG. 4 . For each bag, the lift is adjusted to bring either the hanger loop  17  or the bag spanning strap  15  in the path of the hook  19 . 
         [0039]    If the stevadoring strap is to be used, it may be advantageous, in some cases, to add a spring clip ring  17   a  between the strap and the hook  19 , as illustrated in  FIG. 4A . 
         [0040]    The trolleys and hooks dangling from the conveyer are spaced apart every 7 meters (21 feet) approximately. The conveyer speed is preferably between 30 to 60 centimeters (12 to 24 inches) per second. Accordingly, one bag may be loaded every 10 to 20 seconds approximately. The rate of bag pickup can be slowed by skipping one or more trolleys between bag pickups. 
         [0041]    It should be noted that the various stations can be spaced at a regular interval along the conveyer  2  that may be momentarily stopped as the bag arrive into a station in order to allow manual loading and unloading. 
         [0042]    As shown in  FIGS. 5 and 6 , each full bag  6  enters the BUS through an airlock  26  defined between two sets of double doors  27 ,  28 . After exiting the entry airlock, the bag proceeds through a dumping area  29  where it is first contacted by a pair of ripping tools  30 ,  31  more specifically illustrated in  FIG. 7 . Each ripping tool comprises a rotary saw whose blade  32 ,  33  is obliquely oriented and positioned to rip into a lower portion of one of the sides of the bag. As the bag progresses through the dumping area  29  the entire widths of its lower side portions are slit by the blades  32 ,  33  positioned astride the lower part of the bag. Each rotary saw is supported by a vertically movable carriage  34 ,  35 . The vertical position of each blade can thus be adjusted to accommodate various sizes of bulk bags. 
         [0043]    As shown in connection with saw  30 , the blade can slice the entire lower corner of the bag for a more reliable cut in some applications. Further, the saw  30   a , 30   b  may alternately be positioned under the bag as shown in dotted lines in  FIG. 7  and provided with similar height adjustment mechanisms as the one shown at  34 , 35 . Stationary blades can be used in lieu of rotating ones in some applications. 
         [0044]    At this point, a rod cam  36  projecting laterally from the hook  19  as shown on  FIG. 3 , contacts a barrier  37  extending from the ceiling of the BUS, causing the hook and bag to rotate 90 degrees, and present what used to be the front of the bag to another ripping tool  38  That third ripping tool is constituted by another obliquely oriented rotary saw whose blade slits the lower portion of what used to be the front of the bag, causing the entire bottom of the bag to flap down and release the contents of the bag into an underlying pit  39 . It should be noted that the third ripping tool  38  is positioned in the path of the bag at the same height as the other two side ripping tools  30  and  31 . A series of three barriers  40 ,  41 ,  42  are positioned at progressively increasing heights in the path of the bags and sized to come in momentary contact with each bag as it moves past the ripping tools. As the bag is driven against each barrier the resulting shaking action dislodges any remaining contents. The empty bag  11  exits the BUS through a second airlock  43  similar to the entry airlock  26 , dragging its bottom flap  44 . 
         [0045]    As more specifically illustrated in  FIG. 7 , the pit  39  comprises an auger formed by two slanted walls  45 ,  46  converging toward a trough housing the EXT  12 . In this case, the EXT, comprises an Archimedes screw  47  driven by an electrical motor  48 , and pushing the dumped material into a pipe  49  leading to a temporary storage tank. 
         [0046]    In order to improve the fluidity of certain powder materials such as Portland cement, the walls of the pits are provided with a pair of air slides  50 ,  51 . The air slides comprise an air pump  52 ,  53  injecting air drawn from the upper ridges of the enclosure  7  surrounding the BUS into a manifold  54 ,  55  that feeds the pressurized air to an array of small holes  56  in the entire surface of the pit walls  45 ,  46 . These holes have a diameter within a range of about 2 to 5 millimeters (80 to 200 mils). 
         [0047]    A negative pressure is maintained within the enclosure according to techniques well-known in the art by a powerful blower  66 . The trolley suspension passes through a slot in the ceiling of the enclosure. 
         [0048]    The edges of the slot are provided with feathered strips of elastomeric material that minimize leakage of outside air into the enclosure. 
         [0049]    At the BDS, the empty bag  11  is released by a withdrawing movement of the suspending hook  19  when the roller cam  57  mounted at the end of the shaft  58  projecting from the back of the hook as shown in  FIG. 3 , is captured by a pair of rising ramps  59  that force the hook to swing about its universal joint  60  causing the loop  17  of the hanger to slide off the hook. The empty bag and hanger fall off the conveyer into a disposal bin (not shown on the drawing). As the trolley  20  progresses out of the BDS toward the BLS, the shaft  58  of the cam encounters another barrier similar to the first barrier  37  that causes the hook to shift back 90 degrees toward its original position, ready to pick up the next bag at the BLS. 
         [0050]    The material moves through the pipe  49  which feeds a silo or other type of temporary storage  13 . The material out of the silo can be fed to a bagging plant  61  where it is packaged in smaller bags  62  for the trade or the retail business. 
         [0051]    In the case of Portland cement, the material can also be fed to a concrete mixer  63  that also receives aggregate from an adjacent storage  64 , and delivers it to concrete trucks  65 . The material can also be delivered in bulk through an alternate chute  66 . 
         [0052]    It should be understood that depending on the type of material being handled, other types of processing equipment can draw material from the temporary storage  13 . 
         [0053]    While the preferred embodiment of the invention has been described, modifications can be made and other embodiments may be devised without departing from the spirit of the invention and the scope of the appended claims.