Patent Publication Number: US-2009223179-A1

Title: Bagging Machines and Bags Made Thereby

Description:
BACKGROUND OF THE INVENTION 
     1) Field of the Invention 
     The present invention relates to improved bags made from flexible plastics material webs, particularly adapted for retaining, storing and transporting flowable materials including particulate solids and semi-solid materials, and liquids. The present invention also relates to improved apparatus for, and a method of making the aforesaid bags. 
     2) Description of Related Art 
     It is known, for example, to make bags from tubing formed by wrapping flexible plastics material web in a plurality of overlapping helical spirals and closing opposed ends of lengths of such tubing to form a bag. Such bags are inexpensive to produce and can provide quite strong bags to enable heavy loads to be packed, stored or transported therein. One such arrangement is disclosed in U.S. Pat. No. 5,566,530. These types of bags work quite well and are generally inexpensive to manufacture, however, they do have in some forms, certain disadvantages. One such disadvantage is that the helical or spiral wrapping of the film web layers does provide a “washboard effect” in that transverse join regions are formed both internally and externally on the side walls of the bag. Pressure from the filling apparatus or the filling material itself may cause these join regions to open up to some extent, particularly if the edge regions face the filling direction, which may over time cause leakages or bag/wall failure. Similar effects may also occur on the outer surface of the bag over time by weathering or other external influences. Another disadvantage of these systems is the speed of bag formation, filling and closing can be limited if high speed operation in a continuous or semi-continuous basis is desired. A still further disadvantage of known arrangements of this type, particularly when the formed bag is filled under pressure in a vertical direction is that the overall height of the machinery needed for relatively continuous operation is too great for many conventional building sites. 
     BRIEF SUMMARY OF THE INVENTION 
     A first objective of the present invention is to provide an improved bag construction for bags made from plastics material webs, that will overcome some or all of the aforementioned difficulties associated with known bags of this type. A further objective is to provide both a method of making and apparatus for making improved bags of the aforementioned type that can be produced quickly and efficiently on a continuous or semi-continuous basis. A still further objective is to incorporate a method of filling and closing such bags in a continuous or semi-continuous operation. 
     According to a first aspect of this invention, there is provided a flexible tube for making a bag, said tube being formed from overlapping layers of flexible plastics material webs adhered to one another, the bag being formed as a tube with a first region formed by a plurality of said flexible plastics material webs extending in a longitudinal direction with adjacent edge zones overlapping and adhered to one another, and a second region formed by at least one said flexible plastics material web wrapped in spiral layers with at least adjacent transverse edge zones overlapping and adhered to one another, said first and said second regions being adhered to one another with said first region forming either an inside or an outside surface of the tube. 
     Preferred features of the aforementioned aspect may be as defined in claims  2  to  8  annexed hereto, the subject matter of these claims being hereby incorporated in the disclosure of this specification by this reference thereto. 
     In accordance with a second aspect of this invention, a bag making machine is provided including a support frame means for making a tube from plastics material web, the support frame means extending in a longitudinal direction defining an internal space having a predetermined area, first means for laying a plurality of first flexible webs in the longitudinal direction over said support frame or over plastics material web positioned on said support frame whereby said first flexible webs overlap and adhere to one another to form a first region of the tube, second means for laying at least one second said flexible web in a plurality of spiral windings over said support frame or over plastics material web positioned on said support frame whereby said spiral windings include overlapping edge zones adhered to one another to form a second region of the tube, movement means for moving said tube formed by adhering said first and said second regions together in said longitudinal direction, sealing means whereby said tube is closed and sealed across at least one transverse dimension, and separation means to separate a length of said tube from the tube being formed on said support frame to form a bag closed and sealed at at least one end. 
     Preferred features of the above described second aspect may be as defined in claims  10  to  27  annexed hereto, the subject matter of these claims being hereby incorporated in the disclosure of this specification by this reference thereto. 
     In accordance with a third aspect of this invention, a method of making a bag formed from overlapping layers of flexible plastics material webs adhered to one another is provided, the method including the steps of laying a plurality of first said flexible webs in the longitudinal direction over a support frame with longitudinal edges of said first flexible webs overlapping to form a tube, laying at least one further said flex web in a plurality of spiral windings outwardly of said first flexible web whereby said spiral windings include overlapping edge zones while said first flexible webs are moved in a longitudinal direction, and transversely separating said tube into lengths with at least one end of said tube lengths being transversely sealed to form a bag. 
     Preferred features of the above described third aspect may be as defined in claims  29  to  30  and  32  to  36  as annexed hereto, the subject matter of these claims being hereby made part of the disclosure of this specification by this reference thereto. 
     In accordance with a fourth aspect, the present invention also provides a method of making a bag formed from overlapping layers of flexible plastics material webs adhered to one another, said method including the steps of laying at least one first said flexible web in a plurality of spiral windings on a support frame to form a flexible tube while moving the tube thus formed forwardly in a longitudinal direction, laying a plurality of second said flexible webs in a longitudinal direction over said spiral windings with said second flexible webs having overlapping edge regions, and transversely separating said tube into lengths with at least one end of said tube lengths being transversely sealed to form a bag. 
     Preferred features of the above described aspect may be as defined in claims  32  to  36  as annexed hereto, the subject matter of these claims being hereby made part of the disclosure of this specification by this reference thereto. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Several preferred embodiments of the present invention will hereinafter be described with reference to the accompanying drawings, in which: 
         FIG. 1  is a schematic side elevation view of apparatus for making a bag according to a preferred embodiment of the present invention; 
         FIG. 2  is a schematic view similar to  FIG. 1  showing an alternative embodiment. 
         FIG. 3  is a schematic section view along line III-III of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     Referring to the drawings,  FIG. 1  shows schematically one form of machinery for making and filling bags according to the present invention. 
     The apparatus  10  includes a support frame  11  which in this embodiment is formed by a closed wall duct  12  having an interior zone  13  for the supply of filling material therethrough. The duct  12  in this embodiment is generally square or rectangular with transport devices  14  located in each of the corners. In the illustrated embodiment, longitudinally extending conveyors with an endless belt  15  supported on a plurality pulleys  16 , at least one of which is driven at a desired take off speed that is the same for all of the transport devices  14 . In an alternative arrangement, the endless belt conveyors may be replaced by a plurality of in line driven support wheels or by any other equivalent means of transporting the tube  20  to be formed thereon in a forward direction, ie to the right in  FIG. 1 . In another possible arrangement, the support frame  11  might be formed by an open frame structure, again with transport devices  14  located at its corners. With such a structure, if the bags formed by the machine are to be filled, a separate filling duct may extend through the support frame  11  such that it opens into the tube as it passes from the support frame  11 . As further shown in  FIG. 1 , the filling arrangement might include a hopper  17  delivering material to an infeed chamber or zone  18 , which is provided with a reciprocable press platen  19  to press the filling material along the interior zone  13  of the closed wall duct  12  and subsequently into the bag. The press platen  19  may also be used to compress the filling material when it is positioned at least partly in the bag being formed by the machine. 
       FIG. 1  further schematically illustrates sealing means in the form of sealing jaws  21  for forming a transverse closure and seal  22  in the tube  20  and separation means (cutter knife or the like)  23  for separating the filled and closed bags  24  once produced. A conveyor means  25  of any suitable type may be provided to convey the bags  24  to a storage or transport point as may be desired. The sealing means  21  may form two separate seals or one relatively wide seal with the separation means  23  separating the bags between the two seals or midway between the longitudinal edges of one seal. If considered desirable, guides or guide rollers may be provided to form appropriate gussets in the tube material to assist with the closure and sealing of the tube. The sealing jaws  21  may be heat sealing jaws if the material of the tube  20  is suitable to be sealed in this manner. Any other suitable closure and sealing arrangement could be employed.  FIG. 2  illustrates a similar embodiment to that of  FIG. 1  except that the longitudinal axis of the machine in  FIG. 2  has an inclined downward acute angle to the horizontal whereas in  FIG. 1 , the longitudinal direction is generally horizontal. As can be seen by providing such arrangements, the overall height of the machine is restricted while still permitting continuous or semi-continuous empty or filled bag production. 
     Production of the tube  20  and ultimately of the bags formed therefrom may be as follows. In the illustrated embodiment four rolls  26 ,  27 ,  28 ,  29  of flexible plastics material film web  30  are provided located around the support frame  11  such that they each feed a web  30  in the longitudinal direction of the support frame  11  with the respective webs  30  passing along one face each of the closed wall duct  12 . The edge zones of each of these webs  30  overlap one another, at least at the corners where the transport devices  14  are located. A further roll  31  of a flexible plastics material film web  32  is provided supported on a rotating carriage device (not shown) to traverse a circumferential path  33  about the support frame  11  with the axis of rotation of the roll  31  extending in the longitudinal direction. As the film webs  30  are moving to the right in  FIG. 1  transported by the transport devices  14 , the further film web  32  is laid in a plurality of spiral windings over the webs  30  with the edge regions of the web  32  overlapping one another. The film web  32  adheres itself to the underlying layers, particularly at the corner regions and moreover applies pressure in these corner regions to the overlapping zones of the web  30 . It will of course be appreciated that more than one roll  31  applying multiple spirally wound webs  32  may be provided if a stronger walled bag is required given the load to be carried thereby. 
     At the downstream end of the support frame  11 , a further array of rolls  34 ,  35 ,  36 ,  37  of flexible plastics material film web are provided each laying a respective second film web  38  over the spirally wound layers with the edge regions overlapping at the corner zones as with the rolls  26  to  29 . Press rollers  39  are shown schematically to finally press the adhered layers together. Alternatively, the laminated layers forming the tube  20  might be pressed together by passing the material through circumferentially spaced nip rollers. In a still further possible alternative, the layers may be heat sealed together by passing same through heat sealing jaws that form longitudinal lines of sealing at spaced locations around the tube. 
     The film web material used for making the laminated tube  20  may conveniently be plastics film having some degree of self adherent characteristics. Plastics film such as linear low density polyethylene is suitable however other plastics film material could also be used. If desired the plastics resin used for making the film might include additives to improve its self adhesive characteristics. If necessary, separate application of adhesives might be utilised between some or all layers. In one preferred arrangement the plastics film may be stretched beyond its yield point to increase its length and decrease its thickness. 
     In a further preferred arrangement, the machine schematically shown in  FIGS. 1 and 2  might be assembled in a portable manner, for example on wheels or other transport devices, such that it might be used in agricultural applications where the filling material might be cut grass collected and stored in the bags produced by the machine for making silage. 
     While the annexed drawings illustrate a support frame  11  that is used to produce a substantially square cross-sectioned laminated tube  20 , other rectangular or polygonal shapes could be used as well as circular or oval cross-sectioned tubes  20 . The support frame  11  may readily be constructed such that it is adjustable to vary the size of the tube to be produced. Other variations and modifications within the scope of the annexed claims will be understood by the skilled addressee.