Abstract:
A method for filling a flexible container with a flowable material is provided, including the steps of filling the flexible container, suspending the flexible container, transferring the weight of the flexible container from being suspended to being supported by a support surface, and applying a hoop force to the flexible container to substantially maintain a configuration of the flexible container. The flexible container can be a bag-type container for containing flowable material such as chemicals, food products, agricultural products, and plastic pellets. As the container is lowered from the suspended position to a bottom-supported position, the hoop force is applied around the perimeter as the perimeter changes during transfer of the flexible container from being suspend to being bottom-supported. The hoop force can be applied by stretch wrap. Alternatively, the first flexible container can be lowered into a second flexible container. The second flexible container can be formed from a heat shrinkable material and the second flexible container can be shrunk at the perimeter as the perimeter changes. Alternatively, the second flexible container can be a stretchable bag. A stretched portion of the stretchable bag can be released substantially at the perimeter to generate the hoop force.

Description:
FIELD OF THE INVENTION  
   The invention relates to a container configured to hold a plurality of particles and, more specifically, the invention relates to a method for controlling the shape of a flexible container holding a plurality of particles. 
   DESCRIPTION OF THE RELATED ART 
   Flowable materials present unique problems with respect to storage, transportation, dispensing, and handling. Examples of flowable materials include agricultural products like seeds, rice, grains, vegetables, fruits; chemical products like fine chemicals, pharmaceuticals, raw chemicals, fertilizers; plastics like plastic resin pellets, plastic parts, rejected plastic parts, machined plastic parts; cereals and cereal products such as wheat; a variety of machined parts of all sorts; wood products like wood chips, landscaping material, peat moss, dirt, sand, gravel, rocks and cement. Products and materials that are bulk packaged also include prepared foods; partially processed foods like frozen fish, frozen chicken, other frozen meats and meat products; manufactured items like textiles, clothing, footwear; toys like plastic toys, plastic half parts, metallic parts, soft toys, stuffed animals, and other toys and toy products. 
   Flowable material can be transported in substantially rigid shipping containers such as Gaylord boxes. Gaylord boxes are formed in several different sizes; some are approximately two and one-half feet by two and one-half feet and weigh approximately 85 pounds. Such Gaylord boxes can carry approximately 1,100 pounds of flowable material. Flowable materials can also be transported in flexible containers such as bags or sacks. An example of a flexible container for flowable materials is shown in U.S. Pat. No. 4,113,146. Sacks for transporting flowable material are less costly than a Gaylord box. However, sacks are not rigid and tend to distort when placed on a pallet. Distortion of the sack complicates handling of the sack. For example, bulges can be snagged and torn, causing the sack to spill. 
     FIGS. 1-4  illustrate a bag for transporting flowable materials. A bag  10  for transporting flowable material  12  includes a top  14 , a bottom  16 , and straps  18 ,  19 ,  20 , connecting the top  14  and the bottom  16 . A plurality of loops  22 ,  24  can be disposed adjacent the top  14 . The loops  22 ,  24  can be engaged by a transportation device, such as a forklift, for suspending the bag  10 . The bag  10  is shown in a suspended position in  FIG. 1  without the transportation device for clarity. The bottom  16  can include an inner ring, an outer ring, and loops connecting the inner and outer rings to substantially maintain the shape of the bottom  16  (not shown). The bottom  16  can be connected to the straps  18  and  20  at points  26 ,  28  respectively. The top  14 , bottom  16  and straps  18 ,  20  are substantially inelastic. 
   The bag  10  is shown being transferred from a suspended position in  FIG. 1 , to partially bottom-supported position in  FIG. 2 , and to fully bottom-supported positions in  FIGS. 3 and 4 . The distortion of the bag  10  occurs as the weight of the bag  10  is transferred from being suspended at the top  14  to being supported at the bottom  16 . Distortion can take the form of overall leaning as is shown in  FIG. 3 , bulges  19 ,  19   a  which extend over the edge of the pallet  21 , and sags such as sag  23  which drop over the edge of the pallet  21  as shown in  FIG. 4 . The bag  10  can be substantially cylindrical while suspended as shown in  FIG. 1 , or box-like, and be irregularly shaped when completely supported at the bottom  16  as shown in  FIGS. 3 and 4 .  FIG. 2  shows an exaggerated bulge  19  occurring when the weight of the bag  12  is beginning to be transferred to a pallet  21 .  FIG. 3  shows, in exaggeration, the bag  12  leaning after the weight has been transferred to the pallet  21 .  FIG. 4  shows, in exaggeration, the bag  12  being bottom-supported and defining a bulge  19   a  on one side and a sag  21  on a second side. 
   SUMMARY OF THE INVENTION 
   The present invention provides an apparatus and method for controlling a shape of a flexible container which contains a flowable material. The method includes the step of applying a hoop force to the filled, flexible container to at least substantially maintain a shape of the flexible container. The method also contemplates reducing a cross-sectional area of the filled flexible container in some operating environments. The hoop force is applied to the flexible container as the flexible container is transferred from a suspended position to a bottom-supported position. The hoop force is applied at an annular portion of the perimeter, or cross section, of the flexible container and successive annular portions. The hoop force can also be applied to particular cross-sections as the particular cross-section distorts. Alternatively, the hoop force can be applied proactively, before the flexible container distorts. Generally, the position at which distortion occurs rises during the transfer of the filled, flexible container between the suspended position and the bottom-supported position. The hoop force can be generated by a stretch wrap. Alternatively, the filled, flexible container can be lowered into a second flexible container that can apply the hoop force. For example, the filled, flexible container can be lowered into a second flexible container made of heat shrinkable material. The second flexible container can be shrunk along a longitudinal axis of the first flexible container to control the distortion as the weight is transferred. Alternatively, the second flexible container can be a stretchable bag and a stretched portion of the bag can be released as the transfer occurs. 
   Other applications of the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein: 
       FIGS. 1-4  illustrate the prior art transfer of a bag filled with flowable material between a suspended position, a bottom-supported position, and a side supported position, showing the bulging and distortion of the bag; 
       FIGS. 5-8  illustrate the method for substantially reducing bulging of the bag according to the first exemplary embodiment of the invention; 
       FIG. 9  is a more detailed view of the first exemplary embodiment of the invention shown in  FIGS. 5-8 ; 
       FIG. 10  is a detailed view of a second exemplary embodiment of the invention wherein the filled bag is lowered into a second flexible container formed from heat shrinkable material; and 
       FIG. 11  is a detailed view of a third exemplary embodiment of the invention wherein the filled bag is lowered into a second flexible container formed from stretchable material. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to  FIGS. 5-8 , the invention provides a method and apparatus for containing flowable material. The method includes the steps of suspending a first flexible container  10   a  that is filled with flowable material  12   a . The container  10   a  can be cylindrical or cubic or box-like. The first flexible container  10   a  includes a top  14   a  and a bottom  16   a . The first flexible container  10   a  is suspended from the top  14   a  while in the suspended position  32 . The first flexible container  10   a  also includes a longitudinal axis  42  extending between the top  14   a  and the bottom  16   a.    
   A perimeter  17  extends around the axis  42  and defines a cross-sectional area at each position along the axis  42  from the bottom  16   a  to the top  14   a . The perimeter  17  includes the outer surface of the first flexible container  10   a , extending from the top  14   a  to the bottom  16   a . A first configuration of the perimeter is defined when the first flexible container  10   a  is in the suspended position  32 . Furthermore, a first configuration of each of a plurality of individual cross-sectional areas disposed along the axis  42  between the bottom  16   a  and the top  14   a  is defined when the flexible container  10   a  is suspended. The first configuration of the perimeter  17  and cross-sections of the exemplary first flexible containers  10   a  would be largely cylindrical. 
   In the exemplary embodiment of the invention, the first flexible container  10   a  includes straps  18   a ,  20   a  extending between the top  14   a  and the bottom  16   a . Loops  22   a ,  24   a  are disposed adjacent the top  14   a  for suspending the container  10   a . The bottom  16   a  is preferably fixedly associated with the straps  18   a ,  20   a  at points  26   a ,  28   a , respectively. 
   In cross-section, the first flexible container  10   a  defines a minimized diameter  30  when the first flexible container  10   a  is in the suspended position  32 . The first flexible container  10   a  of the exemplary embodiment is cylindrical and so defines a minimized diameter  30 . However, in embodiments of the invention wherein the flexible container is cubic or rectangular box-like, container would define minimum width-like and depth-like dimensions. When the bag  10   a  is in the suspended position  32 , the straps  18   a ,  20   a  are substantially straight and the cross-section of the container is substantially symmetrical about an axis  42  of the container  10   a.    
   The method of the present invention also includes the step of transferring the first flexible container  10   a  from the suspended position  32  to a bottom-supported position  34  in which the first flexible container  10   a  is supported at the bottom  16   a  by a support surface  36 . The shape of the perimeter  17  changes in response to the transferring step in the prior art. For example, the first flexible container  10   a  can form a cylindrical shape or a box-like shape when in the suspended position. However, during transfer to the bottom-supported position, the perimeter  17  of the first flexible container  10   a  can distort such as, for example, by bulging, leaning, and sagging. Distortion of the first flexible container  10   a  will occur at successive cross-sections along the axis  42  from the bottom  16   a  to the top  14   a  during the transfer as more and more of the weight becomes bottom-supported. Distorting of the perimeter  17  represent changes in the cross-sections disposed along the axis  42  from the first configuration to a second configuration. 
   The method also includes the step of incrementally applying a hoop force to the first flexible container  10   a  from the bottom  16   a  to the top  14   a  along the longitudinal axis  42  to at least substantially maintain the first configuration of the cross-sections disposed along the axis  42  during the transferring step. The hoop force is applied adjacent to the portion of the perimeter  17  that exhibits distortion in the form of the second configuration. For example, it may be desirable to allow some distortion in order to identify when and/or where the application of hoop force should commence. 
   In the exemplary embodiment of the invention, bulging begins at a cross-section adjacent to the bottom  16   a  and application of the hoop force begins adjacent the bottom  16   a  as the transfer begins. The application of the hoop force substantially prevents additional changing of shape of the container  10   a  and the first configuration of the perimeter  17  and the cross-section is substantially maintained. 
   Referring now to  FIG. 6 , when the container  10   a  is transferred to engage the support surface  36 , a portion of the weight of the container  10   a  is received and supported by the surface  36  and a second configuration or bulge level  38  is defined adjacent the bottom  16   a . The second configuration  38  is a change from the first configuration of the perimeter  17 . Preferably, a diameter  40 , defined at the second configuration  38 , is only slightly greater than the diameter  30 . A hoop force is applied to the container  10   a  when the second configuration  38  is first detected or observed. The hoop force is applied incrementally along the axis  42  of the container  10   a  from the bottom  16   a  to the top  14   a  as the entire weight of the filled container  10   a  is transferred from the suspended position  32  to the bottom-supported position  34 . In the schematic illustrations of  FIGS. 6-8 , the hoop forces are applied by a stretch wrap  46 . 
   In an alternative embodiment of the invention, the hoop force is applied as soon as the container  10   a  contacts the surface  36 , before a bulge level  38  is defined. This alternative and optional step can be desirable to prevent the container  10   a  from leaning with respect to the support surface  36 . This step can also be performed if maintaining a maximum height of the container  10   a  is desired. 
   The application of the hoop force can be controlled in response to the change in height of the first flexible container as defined by the distance along axis  42  between the top  14   a  and the bottom  16   a  during transfer between the suspended position  32  and the bottom-supported position  34 . For example, the invention can include a sensor  44  for sensing the height of the bag as the height changes. The sensor  44  can detect when the distance between the top  14   a  and the bottom  16   a  has changed and the application of the hoop forces can be initiated and/or continued in response to the sensed reduction in height. The reduction in height of the first flexible container  10   a  corresponds to the movement of the first flexible container  10   a  into the second configuration  38 . For example, the more the height has been reduced, the greater the first flexible container  10   a  will bulge unless a hoop force is applied. The invention can also include a scale  45  integral with the support surface  36  and the application of hoop forces can be initiated and/or continued in response to the amount of weight supported by the support surface  36 . Alternatively, a timing device may be used to coordinate timing of the transferring step with application of the hoop force. 
   As shown in  FIG. 7 , after hoop forces have been applied along one or more of the cross-sections of the flexible container  10   a  (adjacent to the bottom  16   a  in  FIG. 6 ), the bulge level  38  may rise, moving from the bottom  16   a  of the container  10   a  in direction of the top  14   a . Hoop forces are applied to the container  10   a  along the axis  42  from the bottom  16   a  upwardly at a point near the bulge level  38 , preferably plus or minus twelve inches from the bulge level  38 . However, in some alternative embodiments of the invention, the bulge level may not move. For example, the container  10   a  may be reshaped when wrapped to be pear-like or cone-like. 
     FIG. 9  is a more detailed view corresponding to the view of  FIG. 7 . The container  10   a  is filled with flowable material  12   a  and includes a top  14   a , a bottom  16   a , and a plurality of straps  18   a ,  20   a  extending between the top  14   a  and the bottom  16   a . The container  10   a  also includes loops  22   a ,  24   a . A moving device  48  is schematically shown including a motor  50  and a support member  52 . The support member  52  can engage the loops  22   a ,  24   a  and the motor  50  can move the support member  52  along an axis  54  to raise and lower the container  10   a . The motor  50  can be controlled by a controller  56  to enhance the movement of the container  10   a  from the suspended position, such as position  32  shown in  FIG. 5 , to the bottom-supported position, such as position  34  shown in  FIG. 8 . 
   Stretch wrap  46  is dispensed from a wrap head  58  around the container  10   a  to substantially maintain the diameter  40  and first configuration along the height of the container  10   a  between the top  14   a  and the bottom  16   a . The wrap head  58  can be supported and moved by a moving device  60 . The moving device  60  can move the wrap head  58  vertically along an axis  62  extending parallel to the axis  54 . The moving device  60  can also move the wrap head  58  in an angular direction  64 , around the container  10   a . In operation, the wrap head  58  will move along a helical path extending around the container  10   a  and upwardly from the bottom  16   a  to the top  14   a . In an alternative embodiment of the invention, the container  10   a  can be rotated while the wrap head  58  is moved along the axis  62 . 
   The wrap head  58  moves along the helical path to position stretch wrap  46  adjacent the bulge level  38 . More than one layer of stretch wrap  46  can be applied to any particular cross-section during wrapping. For example, a cross-section adjacent the bottom  16   a  can be wrapped more than once before the wrap head is moved upwardly. Additionally, adjacent cross-sections can be wrapped differently. For example, a cross-section adjacent to the bottom  16   a  can be wrapped more than once and a cross-section adjacent to the top  14   a  can be wrapped once. The application of the hoop force to successive cross-sections is controlled by the controller  56  to substantially minimize changes in the first configuration of the perimeter  17  during the transfer of the flexible container  10   a  from being suspended to being bottom-supported. 
   The controller  56  can control the moving device  60  to enhance the wrapping of the container  10   a . For example, movement of the wrap head  58  can be controlled by the controller  56  in response to a change in the height of the container  10   a . The maximum height of the container  10   a,  such as axis  42  shown in  FIG. 5 , can be programmed into the memory of the controller  56 . A sensor  66  can be disposed adjacent a support surface  36  and sense the proximity of the support member  52 . When the height of the container  10   a  decreases from the maximum height, wrapping can start by moving the wrap head  58  along a helical path around the container  10   a . A speed of movement of the wrap head  58  along the helical path can be controlled by the controller  56  in response to a rate of the reduction in height. For example, the more rapidly the container  10   a  is lowered to the bottom-supported position, the quicker the wrap head  58  can be moved along the helical path. Any sensor capable of sensing a distance corresponding to the distance between the top  14   a  and the bottom  16   a  can be used in combination with the present invention. 
   Alternatively, the movement of the wrap head  58  can be controlled in response to the shifting of weight of the container  10   a  from the support member  52  to the support surface  36 . A weight sensor or scale  68  can be operably associated with the support surface  36 . The sensor  68  can communicate with the controller  56  and the controller  56  can move the wrap head  58  in response to the signal received from the scale  68 . As the weight sensed by the sensor  68  increases, the wrap head  58  can be moved along the helical path. For example, the quicker that the weight of the container  10   a  is transferred to the support surface  36 , the quicker the wrap head  58  can move along the helical path. 
   Alternatively, the movement of the wrap head  58  along the helical path can be controlled by the controller  56  in response to both changes in height and changes in weight. In other words, the controller  56  can move the wrap head  58  in response to conditions sensed by the sensor  66  and conditions sensed by the sensor  68 . For example, wrapping can commence when the sensor  68  first detects weight of the container  10   a  and movement of the wrap head  58  along the helical path can be controlled in response to the rate of change of height sensed by the sensor  66 . 
   The method can also include the step of reducing the cross-section. In some operating environments, the flowable material  12   a  and container  10   a  can be compressed by the hoop forces. Generally, if the flowable material  12  defines a high flowability and low density, the container  10   a  can be compressed and reshaped to enhance the transport of the container  12   a . For example, the container  10   a  can be shaped by the hoop forces to be more cone-like. 
   Referring now to  FIGS. 10 and 11 , the invention can also include moving the flexible container into a second flexible container. The second flexible container can apply the hoop force to the first flexible container to substantially maintain and minimize the diameter of the first flexible container during the transferring step. 
   Referring now to  FIG. 10 , a first flexible container  10   b  can be moved with a moving device  48   a  into a second flexible container  70 . The second flexible container  70  can be supported by a ring member  72  defining an aperture  74 . The first flexible container  10   b  can be lowered into the second flexible container  70  through the aperture  74 . The second flexible container  70  can be formed from a heat shrinkable material. 
   The second exemplary embodiment of the invention includes a heater  76  to direct heat  78  near the second configuration  38   a  to shrink the second flexible container  70 . Shrinkage of the second flexible container  70  generates a hoop force at or near the bulge level  38   a  to maintain the diameter  40   a  and the first configuration. A moving device  80  can move the heater  76  along an axis  82  extending parallel to the container  10   b.  A controller  56   a  can control the moving device  80  in response to a change in the height of the container  10   b  or change in the weight supported by the support surface  36   a  in the same manner as set forth more fully above with respect to the first embodiment of the invention. 
   Referring now to  FIG. 11 , a first flexible container  10   c  can be moved into a second flexible container  70   a  by a moving device  48   b . The second flexible container  70   a  can be supported by a ring member  72   a  defining an aperture  74   a . The moving device  48   b  can lower the first flexible container  10   c  into the second flexible container  70   a  through the aperture  74   a . The second flexible container  70   a  can be a flexible and resilient bag. The second flexible container  70   a  can be stretched and expanded by the ring member  72   a  and incrementally released by roller members  84 ,  86 . A controller  56   b  can control the roller members  84 ,  86  to release a stretched portion  88  of the second flexible container  70   a  during the transfer to maintain the diameter  40   b  of the first configuration of the container  10   c . The ring member  72   a  can be moved with a moving device  90  along an axis  92  extending parallel to the container  10   c . The controller  56   b  can control the moving device  90  to move the ring member  72   a  along the axis  92  in response to a change in height of the container  10   c  or in response to a change in the weight supported by the support surface  36   b  as set forth more fully above with respect to exemplary embodiment of the invention. 
   The foregoing invention has been described in accordance with the relevant legal standards and the description is exemplary rather than limiting in nature. Variations and modifications to the disclosed embodiment may become apparent to those skilled in the art and do come within the scope of the invention. Accordingly, the scope of legal protection afforded this invention can only be determined by studying the following claims.