Abstract:
A pinch bottom bag construction, for a multiwall bag, incorporating an easy open feature, which permits the controlled opening of a portion of the mouth opening of the bag, to create a spout-like opening, with the use of a tear strip disposed on the upper step of the manufacturer&#39;s opening.

Description:
BACKGROUND OF THE INVENTION 
     1. The Technical Field 
     The present invention relates in general to multiwall pinch bottom bags, of the type, which are typically fabricated as a tube formed from one or more paper plies. 
     2. The Prior Art 
     Multiwall bags, fabricated as tubes formed from a plurality of paper plies, are known. Typically, the ends of the tubes are cut, so that when the end or ends of the bag are flattened, the plies of the bag, on both sides of the mouth opening of the bag, are provided with steps. The stepped-end cut pattern creates a closure flap on one side (the “high” side) of the mouth opening of the bag. The side of the bag on the opposite side of the mouth opening is the “short” side. Closure of the bag is typically accomplished by applying adhesive (e.g., hot melt or sonically activatable adhesive) to the outer surface of the short side of the bag. In addition to, or alternative to, providing adhesive on the face of the bag, adhesive may be applied to the inside surface of the closure flap. When the closure flap is folded over the mouth opening of the bag, preferably, the stepped plies of the flap substantially align with and overlie correspondingly cut steps in the bag plies on the face of the bag on the short side of the mouth opening. 
     Closing the bag by simply folding and adhesively affixing the flap provides the pointed, pinch bottom closure. The opposite end of the bag may be likewise provided with a pinch bottom closure, or it may be closed and sealed in a different configuration, such as a diamond- or rectangular configuration, so that the pinch “bottom” may actually be the top of the bag, as may be found commonly in bags containing dry granular material, like dog food or cat litter. 
     In addition to having paper plies, one or more plies, typically the innermost one or more plies, may be fabricated from a thin plastic material, or may be coated with a resinous material, to provide a degree of moisture resistance to the finished bag. 
     While the bag may be formed initially as a simple flattened tube, with folded closure flaps, pinch bottom bags are also known, in which typically both sides of the bag are gusseted, so that there are inward V-folds at each side of the bag, prior to folding the closure flap. Often, because of the stepped-end cutting of the bag plies, in the region of the gussets, the bag material extends beyond the topmost edge of the innermost ply of bag material on the “short” side of the mouth opening, so that in folding over and affixing the closure flap, the tops of the gussets are likewise folded over and captured by the closure flap. Such a prior art gusseted pinch bottom bag is disclosed in Goodrich, U.S. Pat. No. 4,008,850. 
     When such a bag is closed and sealed, the folded over closure is typically quite strong, and requires cutting of the bag plies, below the folded over and sealed closure, in order to gain access to the contents of the bag. 
     In order to facilitate opening of such bag structures, multiwall bag structures are known that incorporate tear structures that may be formed by extended perforations, usually in parallel pairs, through one or more plies of the bag, or by providing ripcord structures that are embedded in the bag plies, that lead to pull tabs, that extend to the outer surface of the bag. Such prior art bag opening structures are disclosed in such references as EP 0 596 747 A1; Rodkey, U.S. Pat. No. 3,272,424; Allen, U.S. Pat. No. 2,560,535; Brady et al., U.S. Pat. No. 2,870,955; Vogt, U.S. Pat. No. 4,088,264; Robinson, U.S. Pat. No. 4,557,385; Jacobs, U.S. Pat. No. 4,768,654; Lepisto et al., U.S. Pat. No. 4,483,445; and Thrall, U.S. Pat. No. 5,281,027. 
     Whether opened by the simple expediency of a cutting or piercing implement, or whether opened through a prior art opening mechanism such as those disclosed in the aforementioned references, typically, opening of the bag either requires substantial effort and/or results in a ragged opening that may include opening the entire mouth of the bag. When the contents of such an opened bag are poured out, because the entire mouth has been opened there is little control over the contents, and undesired spilling of the contents may occur. 
     It would be desirable to provide a multiwall bag formed from one or more plies of bag material, of which at least the outermost ply or plies is/are formed from paper, that has an easy open feature, to enable facilitated access to the contents of the bag, without requiring the use of a cutting or piercing implement. 
     It would also be desirable to provide a multiwall bag, such as a pinch bottom closure bag, that is provided with a secure closure, but which is also provided with an easy open feature, which creates a controlled opening of only a portion of the mouth of the bag, for controlled dispensing of the contents of the bag. 
     These and other desirable features of the present invention will become apparent in light of the present description, claims and drawings. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a bag apparatus for the containment of material, comprising a tubular body, fabricated from at least one ply of material. The tubular body has a longitudinal axis. The tubular body also has a first end configured to form an elongated mouth opening. When in a flattened condition, the tubular body has first and second opposing sides adjacent the elongated mouth opening, and first and second side edges. 
     One of the opposing sides forms an upper step and the other of the opposing sides forming a lower step. A fold line extends across the tubular body, transversely to the longitudinal axis, wherein the elongated mouth and portions of the lower step are disposed longitudinally between the upper step and the fold line. 
     A portion of the lower step, disposed adjacent the first side edge of the tubular body, extends further longitudinally away from the fold line, than other portions of the lower step. 
     A tear string member is disposed transversely across the first end of the tubular body, and extends across the longitudinally extending portion of the lower step, laterally inwardly from the first side edge of the tubular body toward the second side edge of the tubular body. A line of weakness is disposed in at least one layer of the upper step of the tubular body, the line of weakness being substantially aligned with that portion of the tear string member that extends across the longitudinally extending portion of the lower step of the tubular body, and extending at least from the first side edge of the tubular body, laterally inwardly toward the second side edge of the tubular body. 
     In a preferred embodiment of the invention, the upper step is folded about the fold line, over and against the lower step and affixed thereto, the tear string member and the line of weakness remaining in substantially alignment, with the tear string member being in longitudinally spaced position with respect to the fold line. 
     In a preferred embodiment of the invention, the at least one ply of material is paper material. Preferably, the tubular body is formed from three plies of material. 
     In a preferred embodiment of the invention, the tubular body further comprises at least one inwardly folded gusset. The at least one inwardly folded gusset extends inwardly from the first side edge of the tubular body. In such an embodiment of the invention, the longitudinally extending portion of the lower step of the tubular body extends longitudinally beyond at least portions of the at least one inwardly folded gusset. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of the top end of a bag according to a preferred embodiment of the invention, with the bag end open and the tear string omitted. 
     FIG. 2 is a sectional view of the top end of the bag according to FIG. 1, taken along line  2 — 2  of FIG. 1, in which the portions of the plies forming the left-side gusset are shown. 
     FIG. 3 is a sectional view of the top end of the bag according to FIG. 1, taken along line  3 — 3  of FIG.  1 . 
     FIG. 4 is a face elevation of a bag with the manufacturer&#39;s end sealed, according to the embodiment of FIGS. 1-3. 
     FIG. 5 illustrates the cut pattern for forming the upper and lower steps of the bag according to the embodiment of FIGS. 1-4. 
     FIG. 6 is a sectional plan view of the bag of FIGS. 1-5, taken along lines  6 — 6  of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While this invention is susceptible of embodiment in many different forms, there are shown in the drawings and will be described in detail herein, several specific embodiments, with the understanding that the present invention is to be considered as an exemplification of the principles of the invention and is not intended to limit to the invention to the embodiments illustrated. 
     FIG. 1 is a fragmentary front elevation of one end of a pinch bottom bag, according to a preferred embodiment of the invention, in which the flap is unfolded and the mouth of the bag 
     Bag  10  is, in a preferred embodiment of the invention, a multiwall bag having a pinch bottom type of closure structure, at least at one end. Aside from the structure of the end of the bag that is illustrated in FIGS. 1-3, in particular, the remaining structure of bag  10  may be of otherwise conventional construction. The structure that is illustrated is expected to represent, typically, the end of the bag that is opened by the consumer/ultimate customer. The other end of the bag is typically left open, when leaving the manufacturer, to permit filling of the bag by the intermediate customer (manufacturer of the goods to be bagged) and subsequent sealing. 
     Bag  10  is constructed as a tubular body  12  formed from a plurality of plies of material. Tubular body  12  has a longitudinal axis L. In a preferred embodiment of the invention, as shown in FIGS. 1-3 and  6 , tubular body  12  is formed from three plies of material, although a greater or lesser number of plies may be used if desired or as required by the particular application. In a preferred embodiment of the invention, bag  10  has an end  14 , including mouth opening  16 . After tubular body  12  is formed, preferably as part of a continuous tube web from a tube forming machine (not shown), using conventional bag tube forming techniques, the elongated tube web is flattened, and the web cut into discrete tubular bodies  12 . In the cutting process, the ends of each successive bag  10  are step-cut, to create an end structure and profile as illustrated. 
     Bag  10 , as mentioned, in the embodiment of FIGS. 1-6 comprises outermost ply  20 , middle ply  22  and inner ply  24 . These plies are shown in FIGS. 2 and 3. In FIG. 2, the sectional view is taken through the left-side gusset as seen in FIG.  1 . In a preferred embodiment, the longitudinal seams  26 ,  28 ,  30 , for each of plies  20 ,  22 ,  24 , respectively, are laterally staggered, so that the overlaps of each of the seams do not accumulate in thickness, so as to create a longitudinally extending ridge or bump which might adversely affect the manufacturability or handling of the bags during filling and shipping. 
     In the preferred embodiment of FIGS. 1-3, bag end  14  comprises an upper step  32  and a lower step  34 . When bag end  14  is folded, it is folded about a transverse fold line  36 . Fold line  36  may be somewhat higher or lower than the position indicated in FIG. 1, but should not be higher than the lowest edge  38  of ply  24  of lower step  34 , or lower than the upper edge  40  of ply  20  of lower step  34 . 
     To provide a facilitated opening mechanism for bag  10 , after tubular body  12  has been cut and formed into a tube, a perforation  42  is formed in each of plies  20 ,  22  and  24 , in the upper step  32  (the back side of the bag, as shown in FIGS.  1 - 3 ). No perforation is formed in either the gusset layers or in the lower step. A tear string  44  is positioned on bag end  14 , as shown in FIG. 1, aligned substantially over perforation  42 . Note that tear string  44  is actually laid atop portions of the plies of lower step  34 . Tear string  44  is positioned upwardly (with respect to the longitudinal axis of the bag) above the top edges of the innermost plies  22 ,  24  of the gusset portions. 
     In a preferred embodiment of the invention, tear string  44  is positioned either just before or after the adhesive is applied to the upper step  32 , and just prior to folding over of upper step  32 . Adhesive is applied on the inside surface of upper step  32 , as well as those portions of lower step  34 , as indicated by the diagonal broken lines in FIG. 1, being substantially all the exposed surfaces of end  14  that are above fold line  36 . Those portions of upper step  32  that are shielded by covering portions of lower step  34  that are above fold line  36 , are not contacted by adhesive, so that when tear string  44  is pulled, the adjacent portions of the upper and lower steps are not stuck together, so that a pour spout opening can be formed. When upper step  32  is folded over, tear string  44  is thus positioned, as indicated, preferably about ⅜ inch below fold line  36 . In particular, a raised, generally rectangular portion  60  of layer  24 , which is part of the lower step  34 , prevents adhesive from touching those portions of the upper step  32  that are underneath or shielded by portion  60 . Referring to FIG. 1, at least innermost layer  24  of lower step  34  extends completely across tubular body  12 , longitudinally above fold line  36 . That means that portions of innermost layer  24  of lower step  34  are folded over and affixed to other adjacent portions of innermost layer  24  and/or intermediate layer  22  across the entire width of bag  10 . 
     A longitudinally extended portion  36  of innermost ply  24  of lower step  34  extends longitudinally “above” tear string  44 , prior to folding over of the upper step  32 . This extended portion  36  of the lower step  34  permits the adjacent overlying upper step  32  layers to be released when tear string  44  is pulled, whereas, those portions of upper step  32 , to the right side of tubular body  12 , that are not shielded by the lower step are affixed by adhesive “above” tear string  44 , when it is pulled, and preferably, will remain affixed to those portions of the lower step to which they have been adhesively affixed, even if the tear string has been pulled substantially all the way to the right side of the tubular body. 
     Upon pulling of tear string  44 , tear string  44  tears through two thicknesses of ply  20 , in the gusset region, before encountering the perforation  42  in the upper step layers of plies  20 ,  22 ,  24 . 
     When end  14  of bag  10  has been folded over and sealed, opening of the end of the bag is accomplished by pulling tear string  44  through extended portion  46  of ply  24  of lower step  34 . A free end  48  of tear string  44  extends to the side of tubular body  1   2 , for grasping. Perforation  42  preferably extends only a portion of the distance from the left-side edges of bag body  12 , toward the middle of the width of the bag. 
     FIG. 4 is an elevation of bag  10 , shown with end  14  folded over and sealed. In a preferred embodiment of the invention, the positioning of string  44  and perforation  42  will be such that they will be preferably approximately ⅜ inch of the fold, although this distance may be varied, depending upon the requirements of a particular application. The inwardly tucked folds  50 ,  52  of the side gussets are shown by the broken lines, in both FIGS. 1 and 4. The layers of bag  10  below the level of mouth  16 , are shown in FIG. 6, wherein the inward fold  50  of the left-side gusset, as seen in FIG. 1, is also indicated. 
     FIG. 5 illustrates the patterns for the cuts for forming the upper and lower steps for the bag end  14  for the embodiment of the invention, according to FIGS. 1-3, which cutting specifications will be readily understood by one of ordinary skill in the art of paper bag manufacturing, having the present disclosure before them. 
     The opening mechanism of the present invention allows the consumer to create an opening at the side of the bag, which can be more easily controlled than prior art bag opening systems, in which the opening is typically formed toward the midpoint along the width of the bag end. In particular, prior art tear string opening mechanisms have usually created an opening at the center of the width of the bag, often leading to particularly ragged openings, that are awkward to manipulate. 
     The foregoing description and drawings merely explain and illustrate the invention, and the invention is not limited thereto except insofar as the appended claims are so limited, as those skilled in the art who have the disclosure before them will be able to make modifications and variations therein without departing from the scope of the invention.