Patent Publication Number: US-2009226120-A1

Title: Sack for storing and dispensing bulk dry materials

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application claims priority from, and incorporates by reference the entire disclosure of U.S. Provisional Patent Application No. 61/031,876, filed on Feb. 27, 2008. 
    
    
     FIELD OF THE INVENTION 
     The invention relates generally to bulk sacks and, in particular, to improved bulk sacks for transportation and delivery of bulk quantities of powdered or granular material. 
     BACKGROUND OF THE INVENTION 
     Dry flowable materials such as fertilizer are often supplied in bulk sacks designed to hold pre-metered quantities of material based on consumer needs and handling equipment limitations. Bulk sacks of this kind are generally constructed of a woven plastic material, cut and sewn into a generally rectangular box shape. 
     For filling and discharge, such bulk sacks typically include an upper filling spout, through which materials are charged into the sack, and a bottom discharge closure arrangement through which the flowable material may be discharged at the point of use. 
     Known examples of sacks having closable openings at the top and bottom are described in U.S. Pat. Nos. 3,961,655 (Nattrass, et al.), 4,364,424 (Nattrass), and 6,431,752 (Rogers, et al.). 
     In conventional bulk sacks, there is provided a bottom spout which is tied off prior to filling and a top or filling spout which is tied off after filling is complete. In use, emptying the sack of its materials requires the operator to lift the sack over its target, and either to cut or to untie the knot which has been keeping the emptying spout closed. Where, as is often the case, the sack includes an interior liner to provide airtight storage, the operator must also reach up inside the sack and cut that liner substantially to allow the material to flow out freely. 
     This conventional process is characterized by inconvenience and costs which the present invention is intended to eliminate. The complexity of sewing two spouts and tying mechanisms onto a conventional bulk sack adds to manufacturing costs, and the procedure of untying the emptying spout of the sack is time-consuming. Further, the dimensions of the spout impose a limit on the rate of flow of the product out of the sack which could be disadvantageous if this rate is not commensurate with the speed at which material can be processed as it exits the sack. 
     One attempt which has been made to simplify and lower the cost of use of bulk sacks of this general kind has been to provide the sack with a filling hole only and no emptying tube. The sack is elevated over the target where the operator wishes the material to be delivered and the bottom of the sack is sliced open, using a sharp instrument. While such sacks are generally less expensive, the procedure of cutting the woven sack bottom often results in the breakage of fibers from the sack itself, which enter into the product as it is discharged. That is undesirable, particularly where the materials carried or their subsequent processing must be free of contaminants. 
     SUMMARY OF THE INVENTION 
     To address the aforementioned disadvantages, a bulk sack according to the present invention is manufactured with an integral patch over an opening in the bottom of the sack, in lieu of the bottom discharge spout. This patch is of a size, material and thickness chosen to be strong enough to hold back the weight of the contents during transport. When sliced open manually at the point of delivery of the sack contents, the patch allows for the outflow of materials. Importantly, such bottom cutting patches can be made from materials which will not lead to contamination of the end product. A number of plastic materials, with or without internal webbing, have been found suitable. 
     The perimetrical shape of the patch and of the opening formed when the patch is cut is selectively formed so that a desired rate of discharge of materials inside the sack is achieved. 
     Using a bulk sack with integral cutting patch according to the present invention, less costly sacks can be manufactured and less time required by the operator to begin emptying the sack. Too, the patch size can be predetermined for regulation of the outflow of product at a desired mass flow rate. 
     The construction of bulk sack according to the invention also permits use of a piercing/discharge structure containing a blade upon which the sack patch can be set to initiate and facilitate emptying of the sack. 
     In a large industrial application, the efficiencies afforded by using sacks according to the invention are cumulative and can be substantial. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of various embodiments of the invention may be obtained by reference to the following Detailed Description when taken in conjunction with the accompanying Drawings wherein: 
         FIG. 1  is a perspective view of a conventional dry material bulk sack illustrating an upper filling spout; 
         FIG. 2  is a top plan view of the bulk sack of  FIG. 1 ; 
         FIG. 3  is a bottom plan view of the bulk sack of  FIG. 1  illustrating an emptying spout open in a discharge position; 
         FIG. 4  is a bottom perspective view of the bulk sack of  FIG. 1  illustrating a centrally disposed cuttable patch; 
         FIG. 5  is a bottom plan view of an exemplary bulk sack illustrating a substantially rectangular shaped bottom patch according to an exemplary embodiment; and 
         FIG. 6  is a bottom plan view of an exemplary bulk sack illustrating a substantially cruciform shaped bottom patch according to an exemplary embodiment providing a predetermined opening area which uses less patch material, and hence less material exposed to a pressure of the sack contents. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION 
     Various embodiments of the invention will now be described more fully with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, the embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The above summary of the invention is intended to represent exemplary embodiments of the invention. 
       FIGS. 1-2  illustrate perspective and top plan views of a conventional bulk sack. The bulk sack according to an exemplary embodiment of the present invention will appear in its upper portion and sides much like the conventional bulk sack of  FIGS. 1-2  having a top wall  10 , generally rectangular sides  12 , support/carrying loops  14 , and a filling spout  16 . 
       FIGS. 3-4  illustrate bottom plan and bottom perspective views of the bulk sack of  FIG. 1 . The bulk sack includes a bottom wall  18  having an emptying spout  20  and an associated collar structure  21 . 
     According to an exemplary embodiment of the present invention, the bulk sack does not include the emptying spout  20  and associated collar structure  21 , as illustrated in the conventional bulk sack of  FIGS. 3-4 . According to an exemplary embodiment of the present invention, the exemplary bulk sack includes a cuttable bottom patch covering an opening in the bottom of the bulk sack. 
       FIG. 5  is a bottom plan view of an exemplary bulk sack illustrating a substantially rectangular shaped bottom patch  22   a  according to an exemplary embodiment. According to an exemplary embodiment of the invention as illustrated in  FIG. 5 , the opening and patch  22   a  are of a generally rectangular form. The four sides of the opening and of the overlapping section of patch are slightly rounded, so that they merge smoothly into each other, rather than at sharp corners when resistance of the patch material might be lessened presenting a risk of unintended tearing. In a typical embodiment, a preferred material for patch  22   a  is a cross-laminated high density polyethylene plastic which may be sliced open, as noted above, without the production of contaminating fibers or fragments. 
       FIG. 6  is a bottom plan view of an exemplary bulk sack illustrating a substantially cruciform shaped bottom patch  22   b  according to an exemplary embodiment providing a predetermined opening area which uses less patch material, and hence less material exposed to a pressure of the sack contents. 
     According to an exemplary embodiment of the invention as illustrated in  FIG. 6 , the patch  22   b  is of a generally cruciate shape. The generally cruciate shaped patch  22   b  is operable to cover an opening at a bottom portion of the sack. The area of the planar opening from an inside to an outside of the sack is much smaller than for the rectangular patch  22   b , thereby exposing less patch material to the pressure of the sack contents. However, slicing along an intersecting axis of the substantially cruciform shaped patch  22   b  leads to a pouring out of the flowable material and to the part-flaps  23   a ,  23   b ,  23   c  and  23   d , formed by cutting to open downwardly and allow the material to flow out centrally and smoothly. 
     For a particular product/application, the size and shape of cuttable patch can be selected to regulate the outflow of material to a desired degree. 
     The specific embodiments illustrated in the drawings should not be construed as limitations on the scope of the invention but, rather, only as exemplifying preferred variations of the invention which is defined in the attached claims.