Abstract:
A dosing bag for additives that are mixed into a cementitious mixture, wherein the dosing bag is made from a dissolvable starch-based film material. When the dissolving dosing bag with its contents are introduced into a mixture that uses water as an ingredient, the dosing bag dissolves at a particular rate such that the additives are released into the mixture in an even manner. The dosing bag has structural features that enable it to dissolve and release material over an extended period of time. Consequently, the material in the dissolving dosing bag is not released as a clump, but is rather released in a manner that ensures is even distribution during mixing. When the additives are more evenly dispensed throughout a mixture, the quality of the final product is greatly improved.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of U.S. Provisional Patent Application No. 61/384,699, entitled Dosing Bag Structure For Dispensing Fiber And Admixtures And Its Method Of Manufacture, filed Sep. 20, 2010. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to prepackaged dosing bags for dry admixtures and/or fibers that are intended to be added to cementitious mixtures that contain water. 
         [0004]    2. Prior Art Description 
         [0005]    Fibers and/or other admixtures are often added to cementitious products such as concrete. Typically, fibers and/or admixtures are added immediately before or during the mixing of the cementitious product. Fibers and/or admixtures are used to improve or modify the cementitious material. Fibers and/or other admixtures are used to modify the properties of concrete in such a way as to improve the product, make the product more suitable for a particular purpose, or for economy. The primary reasons for using fibers and/or other admixtures in concrete are (1) to achieve certain properties in concrete more effectively than by other means; (2) to maintain a quality of concrete throughout the successive stages of mixing, transporting, placing, and curing; (3) to overcome certain emergencies during concrete making or placing operations; (4) to reduce the cost of concrete construction; and (5) to improve the mixture to control cracking or other detrimental effects. In most instances the desired effect within the cementitious material can only be achieved by the use of fibers or admixtures. In addition, the use of fibers and/or admixture allows the use of less expensive construction methods or designs and thereby offsets the costs of the add materials. 
         [0006]    As an example, consider a mixing truck at the end of a delivery that still contains wet concrete within its mixer. If the wet concrete is left in the truck overnight, the residual product will set and begin to harden. While the wet concrete can be washed out of the truck with a large amount of water, the disposal of the liquid may cause an environmental problem. To avoid this problem, it is desirable to delay or retard the setting of concrete so that it remains fluid and can be used the next day. This affect is achieved by adding a retarding admixture to the wet cement. However, an exact amount of the admixture has to be added. If too much is added, the cement will not properly cure the next day. If too little is added, the concrete may harden prematurely. 
         [0007]    Fibers and other concrete admixtures are typically provided as filaments, solids or powders. As such, they must be mechanically mixed into cement in order to be distributed. The more thorough the mixing, the more uniform the fibers and/or admixtures are dispersed. The successful use of these admixtures depends upon the accuracy with which they are prepared, the rate of which they are dispensed and the thoroughness of their distribution within the mixture. 
         [0008]    Typically, concrete is made by weighing or volumetrically measuring the ingredients for a batch and introducing all ingredients into a wet mixer. It is important that the amount of fiber and/or admixture added during batching is carefully controlled. Inaccuracies in the amount of fiber or admixture added or the thoroughness of dispersion can significantly affect the properties and performance of the concrete products. The need for accuracy in measuring and having even dispersion of the amount of fiber or admixture to be added to a particular batch is particularly acute when a relatively small amount of fiber or admixture is required for the product. 
         [0009]    For fibers and/or admixtures, it is cumbersome and time consuming to accurately weigh the required amount of additives. Thus, workers add fibers and/or admixtures to the concrete in pre-measured and pre-packaged bags. Such bags are known in the industry as dosing bags. The use of pre-measured dosing bags not only minimizes human error in handling and weighing but it also facilitates the process of mixing them into the product. One drawback of using dosing bags is that opening and emptying the pre-packaged dosing bags into the mixer creates a mess, wastes time, and results in some degree of spillage. The spillage contributes to inaccuracies in batching. It also exposes workers to chemicals and dusts that are best not inhaled. 
         [0010]    Another drawback in using prior art dosing bags is that the typical dosing bags is made either from thin paper that is sealed with glue or with a heat seal strip. Workers often just throw these bags into a mix with no concern that the bag and the bag&#39;s seal will not dissolve into the mix. If this debris is not physically removed, it can create flaws in the final concrete product. Furthermore, the additives stuck within the bag tend to get trapped in the bag and clump up. Extra mixing time must therefore be used to ensure that the additives have the opportunity to disperse throughout the mixture. 
         [0011]    Some attempts have been made to develop a dissolving dose bag from dissolvable films such as polyvinyl acetate or polyvinyl alcohol (PVA). Such prior art dosing bags are exemplified by U.S. Pat. No. 4,961,790 to Smith, entitled Concrete Admixture Device and Method Of Using Same. However, such prior art dosing bags are highly sensitive to the humidity in the air. Thus, such prior art dosing bags must be packaged and stored inside an air-tight bag or other low-moisture environment. This is highly impractical at most jobsites where concrete is being mixed for use. One humid night can ruin thousands of pounds of additives, if not stored properly at the jobsite. 
         [0012]    Another problem associated with such prepackaged additives, is that the dissolvable packaging disintegrates so rapidly, that the additives held in the packaging never have the opportunity to disperse before they pass into the mixture. Again, the result is that the additives tend to clump together and remain clumped during the mixing process. Again, extra mixing is needed to ensure that the clumps are broken and that the additives have had the opportunity to disperse evenly throughout the mixture. 
         [0013]    A need therefore exists for an improved packaging system for fibers and admixture that can be thrown directly into a cementitious mixture, where the package disperses its contents slowly and evenly, yet wherein the packaging completely dissolves. This need is met by the present invention as described below. 
       SUMMARY OF THE INVENTION 
       [0014]    The present invention is a dissolving dosing bag for fiber or other concrete admixtures that is made from a dissolvable starch-based film material. When the dissolving dosing bag with its contents are introduced into a mixture that uses water as an ingredient, and which is agitated for a period of time, the dissolving dosing bag dissolves at a particular rate such that the fiber or other concrete admixtures are released into the mixture in an even manner. 
         [0015]    The dissolving dosing bag has structural features that enable it to dissolve and release material over an extended period of time. Consequently, the material in the dissolving dosing bag is not released as a clump, but is rather released in a manner that ensures is even distribution during mixing. When the fiber or other admixtures are more evenly dispensed throughout a mixture, the resulting final product is greatly improved. Furthermore, since the added material is very evenly distributed, often less fibers or admixtures are needed to be effective. The controlled release of the fibers and admixtures overcome the tendency of the fibers or other admixtures to ball up, clump, or suffer from improper dispersion or incomplete mixing. 
         [0016]    The present invention further provides a method for fabricating the dissolving dosing bags. The starch-based film material of the dosing bags may be sealed using the application of heat. Using different heat settings, the film material proximate the heat seal can be altered to dissolve either faster or slower than the remainder of the doing bag. Such alterations are used to produce a dosing bag that releases its contents in a controlled manner over a prolonged period of time. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    For a better understanding of the present invention, reference is made to the following description of an embodiment thereof, considered in conjunction with the accompanying drawings, in which: 
           [0018]      FIG. 1  is a perspective view of an exemplary embodiment of a plurality of dosing bags; 
           [0019]      FIG. 2  is a front view of a dosing bag; 
           [0020]      FIG. 3  is a front view of a dosing bag after dissolving for a first period of time; 
           [0021]      FIG. 4  is a front view of a front view of a dosing bag after dissolving for a second period of time; 
           [0022]      FIG. 5  is a front view of a second embodiment of a dosing bag after dissolving for a first period of time; 
           [0023]      FIG. 6  is a partially fragmented perspective view of a third embodiment of a dosing bag; and 
           [0024]      FIG. 7  is a partially fragmented perspective view of a forth embodiment of a dosing bag. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    Although the present invention dosing bag system can be embodied in many ways, the illustrations selected show only three variations of the invention. These embodiments are selected in order to set forth the best modes contemplated for the invention. The illustrated embodiments, however, are merely exemplary and should not be considered a limitation when interpreting the scope of the appended claims. 
         [0026]    Referring to both  FIG. 1  and  FIG. 2 , a first exemplary embodiment of a dissolving dosing bag  10  is shown. The dosing bag  10  is made from a starch-based water dissolvable film  12 . The film  12  that is heat sealed around a volume of dry additive material  14 . The dry additive material  14  can be fibers or any other dry or powdered admixture that a person may want to add to a cementitious mixture. 
         [0027]    The dissolvable film  12  used to make the dosing bag  10  is a hygroscopic plastarch material PSM. Several formulations of such PSM materials are commercially available in the marketplace. The composition of a preferred PSM is described in U.S. Patent Application Publication No. 2008/0153958 to Ding, entitled Substantially Completely Biodegradable High Starch Polymer, the disclosure of which is incorporated into this specification by reference. 
         [0028]    The dosing bags  10  are made by heat sealing seams  16  between and around deposits of the dry additive material  14 . This creates sealed pockets  18  that isolate the dry additive material  14 . The pockets  18  preferably hold less than 0.5 pounds of additive material  14  and may be so small that they hold only one or two ounces. During manufacturing, the dosing bags  10  are interconnected at the seams  16 . The various interconnected dosing bags  10  are then packaged in larger boxes, such as a five pound box or a twenty pound box. 
         [0029]    For example, suppose that at particular batch of cementitious material requires 16¾ pounds of reinforcement fibers for a particular application. Using the present invention system, the fibers can be prepackaged in ¼ pound dosing bags  10 . Eighty such dosing bags  10  can then be packaged into a twenty pound box. To meet the requirement, a worker needs to open the box and toss sixty seven dosing bags  10  into the mix in order to precisely meet the 16¾ pound requirement without waste. The remaining thirteen remaining dosing bags  10  are saved for later use. Since the dosing bags  10  are tossed whole into a mixer, there is no labor wasted in measuring and dumping the fibers. Furthermore, since the dosing bags  10  are never opened by the worker, there is no danger of chemical contamination or inhalation hazards from the additive material  14 . 
         [0030]    The addition of multiple small dosing bags  10  into a mixer, rather than the addition of a few large bags greatly increases the thoroughness at which the additive material  14  is dispersed throughout the mixture. As a result, the likelihood that additive material  14  clumping will occur is greatly reduced. 
         [0031]    The dissolvable film  12  is heat sealed along the seams  16  that surrounds a peripheral edge of the dosing bag  10 . When the dosing bags  10  are heat sealed, the dissolvable film  12  becomes heated in the area of the seam  16 . The degree of heating is inversely proportional to the distance from the seam  16 . That is, the dissolvable film  12  is heated to into a bond along each seam  16 . However, the dissolvable film  12  is inadvertently heat treated in the areas  20  adjacent to the heated seam  16  by the heating element that creates the seam  16 . 
         [0032]    It has been discovered that the dissolvability of the dissolvable film  12  is affected by such a heat treatment. The dissolvable film  12  dissolves in water. However, the rate at which the dissolvable film  12  dissolves can be either decreased or increased by heat treating the dissolvable film  12  when creating the seams  16 . Consequently, the dissolvable film  12  at the seam  16  and in the heat treated areas  20  adjacent to the seam  16  can be made to dissolve either slower or faster in water than the untreated film  12  within the central areas  22  of the dosing bag  10 . 
         [0033]    The sealing of the dosing bag  10  can be achieved using many commercial plastic sealing machines. A preferred machine is the Model PSF-400 impulse heat sealing machine made by the Cleveland Equipment &amp; Machinery Company of Memphis, Tenn. Using such sealing equipment, it has been discovered that using a sealing machine at low temperatures and with short sealing times creates heat treated areas  20  of the dissolvable film  12  that dissolve slower than the central areas  22  of the dosing bag  10 . Conversely, it has been discovered that using a higher temperature setting for a longer period of time degrades the dissolvable film  12  and the heat treated areas  20  of the dissolvable film  12  can be made to dissolve faster than the central areas  22  of the dosing bag  10 . Both phenomenons can be utilized by the present invention. 
         [0034]    Referring to  FIG. 2 ,  FIG. 3  and  FIG. 4 , it will be understood that the instant before the dosing bag  10  is exposed to water in a wet mixer, the dosing bag  10  is intact and the contents of the dosing bag  10  are confined. This is shown in  FIG. 2 . Assuming that the dosing bag  10  was manufactured in the manner that makes the seams and heat treated areas  20  of the film  12 , slower to dissolve than the central areas  22  of the dosing bag  10 . In this scenario, after a short period of time, such as 5 seconds-10 seconds, the central areas  22  of the dosing bag  10  begin to loose integrity. This releases some of the additive material  14  stored within the dosing bag  10 . This is shown in  FIG. 3 . After the passage of another short period of time, the heat treated areas  20  of the dosing bag  10  begin to dissolve. This releases the remainder of the additive material from inside the dosing bag  10 . This is shown in  FIG. 4 . 
         [0035]    It will therefore be understood that when the dosing bag  10  is thrown into a wet mixer, it begins to dissolve and release its contents. However, this process is not instantaneous. Rather, the additive materials  14  are released over a prolonged period of time that can last between twenty seconds and ninety seconds. This relative slow release of the additive materials  14  is occurring during the mixing of the cementitious material. As a result, the additive material  14  is provided with the opportunity to be thoroughly dispersed throughout the cementitious mixture without any clumping. 
         [0036]    A similar effect can be achieved by making the seams  16  of the dosing bag  10  dissolve at a faster rate than does the central areas  22  of the dosing bag  10 . Starting with the dosing bag  10  shown in  FIG. 2 , it can be seen that the dosing bag  10  is intact as it is thrown into a wet mixer. Referring now to  FIG. 5 , it can be seen that after a few seconds, the seams  16  and heat treated areas  20  begin to dissolve first. This released some of the additive material  14  from various points around the dosing bag  10 . After several more seconds, total integrity of the dosing bag  10  is lost and all of the additive material  14  is released. 
         [0037]    It will therefore be understood that when the dosing bag  10  is thrown into a wet mixer, it begins to dissolve and release its contents. However, this process is not instantaneous. Rather, the additives are released over a prolonged period of time that can last between twenty seconds and ninety seconds. As a result, the additive materials  14  are provided with the opportunity to be thoroughly dispersed throughout the cementitious mixture without any clumping. 
         [0038]    Referring now to  FIG. 6 , another embodiment of the dosing bas  30  is shown. In this embodiment, the dissolving film  32  need not have a uniform construction. Rather, in selected sections  34  of the dosing bag  10 , the dissolvable film  12  can be either thinned or heat treated to rapidly dissolve. In these selected sections  34 , the dissolvable film  32  preferably will dissolve 30% and 70% faster than in other regions of the dosing bag  30 . 
         [0039]    It will be understood that when the dosing bag  30  is placed in a mixer and is exposed to water, the selected sections  34  will dissolve away before the rest of the dosing bag  30 . Likewise, the agitators within the mixer are likely to cause tears in and around the selected sections  34  before tearing the other areas of the dosing bag  10 . Consequently, when the dosing bag  10  is thrown into a mixer, the selected sections  34  open first and release the contents of the dosing bag  30  at a controlled rate. As a consequence, the dosing bag  30  begins to empty. Eventually, the entire dosing bag  30  dissolves, thereby ensuring that the contents of the dosing bag  30  are released. 
         [0040]    Due to the selected sections  34  of the dosing bag  30 , the dosing bag  30  will continuously release its contents over a span of about thirty seconds to ninety seconds. At the end that period of time, the dosing bag  30  dissolves to a point where it loses all structural integrity and all of its contents are released. 
         [0041]    In a mixer, where there are moving agitators and a volume of cementitious material, mixing occurs fairly rapidly. A dosing bag  30  that releases material in a sixty-second timeframe enables the material being dispensed to fully intermix throughout the cementitious mixture. Furthermore, since the dosing bag  30  releases its contents over this prolonged period of time, there are no clumps or balls of material that can pass through the mixer without being properly integrated. 
         [0042]    Referring to  FIG. 7 , an alternate embodiment of a dissolving dosing bag  40  is shown. In this embodiment, there is a primary bag  42 . Inside the primary bag  22  are fibers or admixture material  44  as well as at least one secondary bag  46 . The secondary bag  46  is also filled with the fibers or admixture material  44 . 
         [0043]    When the dosing bag  40  is placed in a mixer, the primary bag  42  dissolves away and releases a first volume of the fibers or admixture material  44 . The secondary bag  46  is then exposed to the water in the mixer. The secondary bag  46  eventually dissolves and releases a second volume of fiber or admixture material  44 . 
         [0044]    If there is more than one secondary bag  46  disposed within the primary bag  42 , each secondary bag  46  may have a different bag thickness so that they dissolve away at different rates. 
         [0045]    The bag within a bag construction enables the fiber and admixture material  44  to be dispensed for prolonged periods of time within a mixer. Depending upon the number of secondary bags  46  used, the complete dispensing process can be prolonged over a period of a few minutes. 
         [0046]    In all the described embodiments, the term water dissolvable as used herein denotes a physical or a chemical property of the starch-based film material. It means that the film will completely dissolve in water, either cold or warm and after only a brief period of time. Prior art bag materials, such as foam, cellulose, paper products, cotton products, and plastic are not dissolvable. 
         [0047]    It can be seen from the foregoing discussion that the present invention solves most of the problems encountered in the prior art practice. It is believed that the operation and construction of the present invention will be apparent from the foregoing description. While the method and device shown and described have been characterized as being preferred, it will be obvious that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined in the claims.