US 3733024 A
A paper container of the bag type is provided wherein the wall structure incorporates an elastic, longitudinally oriented strip overlying a weakened section of the wall. The elastic strip is bonded to the wall along bonding zones on both sides of the weakened section of the wall, leaving the area of the strip overlying the weakened section free and unattached to the wall. This arrangement concentrates undue dynamic and static stresses at the weakened section of the wall where they are taken up by the elastic strip after rupture of the weakened section.
Claims available in
Description (OCR text may contain errors)
United States Patent [191 Bolling, Jr. et al. May 15, 1973 [5 1 CONTAINER 3,325,082 6/1967 Naylor ..229 55 3,507,443 4/1970 Gerard ..229/55 [75| lnventorszRobert W. Bolling, Jr., Frank S.
McCall, Henry J. Rawl, all of Savannah, Ga.
 Assignee: Union Camp Corporation, Wayne,
 Filed: Sept. 18, 1969  App]. No.: 858,947
 US. Cl ..229/55, 229/53  Int. Cl. ..B65d 33/02  Field of Search ..229/55, 53, DIG. 14
 References Cited UNITED STATES PATENTS 3,276,671 10/1966 Fleitman ..229/53 Primary Examirier-David M. Bockenek Attorney- Kane, Dalsimer, Kane, Sullivan & Kurucz  ABSTRACT A paper container of the bag type is provided wherein the wall structure incorporates an elastic, longitudinally oriented strip overlying a weakened section of the wall. The elastic strip is bonded to the wall along bonding zones on both sides of the weakened section of the wall, leaving the area of the strip overlying the weakened section free and unattached to the wall. This arrangement concentrates undue dynamic and static stresses at the weakened section of the wall where they are taken up by the elastic strip after rup ture of the weakened section.
6 Claims, 9 Drawing Figures PATENTEDMAYI 5 I915 13; 733 024 SHEET 1 BF, 3
Ail, JM, 4
ATTORNEYS PATENTED 3, 733,024
SHEET 2 OF 3 h cf rkirf CONTAINER BACKGROUND OF THE INVENTION Containers of the paper bag type occasionally undergo extreme stresses, dynamic and/or static for short periods during use. Such extreme stress conditions may arise during commodity filling operations or when the filled bag is subsequently handled.
It is a principal object of the present invention to provide a paper container capable of withstanding without total failure such temporary undue dynamic or static stresses which exceed the normal rupture stress of the paper forming the container.
SUMMARY OF THE INVENTION The aforementioned and other beneficial objects and advantages are attained in accordance with the present invention by providing a paper bag, the walls of which include one or more longitudinally extending weakened zones. A strip of elastic material overlies each of the weakened zones and each strip is bonded to the bag wall along bonding zones which do not comprise portions of the weakened zones. The weakened zone may be in the form of a series of perforations in the wall; a longitudinal seam of the bag; an area in the wall of a multi-ply bag formed of fewer plies than the remainder of the bag wall; a chemically weakened zone such as may be obtained by subjecting sections of the bag wall to a suitable acid or alkaline solution; or a zone weakened by any other suitable method. Any undue stress applied to the bag would concentrate at the weakened section, causing a rupture thereof whereafter the elastic strip would absorb the increased stress thereby preventing a total failure of the bag. The bag walls are sufficiently strong to withstand normal loads applied to the bag wall.
BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:
FIG. 1 is a perspective view of a bag incorporating the construction of the present invention;
FIG. 2 is a fragmentary sectional view taken along reference lines 22 of FIG. 1 in the direction indicated by the arrows;
FIG. 3 is a perspective view of an alternate embodiment of the bag of the present invention;
FIG. 4 is an exaggerated top plan view of the bag depicted in FlG. 3;
FIG. 5 is a perspective view of a multi-ply bag in accordance with the present invention.
FIG. 6 is a sectional view taken along reference lines 6-6 of FIG. 5 in the direction indicated by the arrows;
FIG. 7 is a sectional view similar to FIG. 6 illustrating a modified multi-ply bag construction; and
FIGS. 8 and 9 are further modifications depicting plastic lined multi-ply bags wherein portions of the plastic liner serve to reinforce the weakened area of the bag wall.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT standard machine. In this connection the bag is provided with the usual folded front and rear walls 12 and 14 and side walls 16, as well as a closed bottom end and an open top end. It should be understood that the form of bag 10 is chosen merely for illustrative purposes and that the bag could assume any other desired shape, as for example, bag 10 could be a sewn or pasted valve bag. A portion of the bag wall weaker than the remaining portions of the bag wall in the form of a line of perforations 18 extends longitudinally along front wall 18. A strip 20 formed of an elastic or stretchable material overlies the perforations and is secured to the wall by a bonding medium along bonding zones 22 which extend substantially parallel to the perforations and are spaced somewhat apart from the perforations on both sides thereof. Thus, the portion of strip 20 that actually overlies the line of perforations is free and unattached to wall 12. The operations of perforating the bag wall and overlaying and attaching strip 20 to wall 12 could be accomplished in the web section of a conventional bag forming machine prior to the process of folding, scoring, bottoming, and otherwise fabricating the bag. The bonding agent may be a suitable paste or glue or, if the strip is formed of a thermoplastic material the strip may be heat bonded to the bag wall.
The material used for strip 20 may be any web-like substance with both transverse and longitudinal stretch, that is, an elastic material. Alternately, a material which stretches with a measurable degree of resistance and no appreciable recovery could be employed. In any event, strip 20 should have a greater stretch factor or a greater stretch and recovery factor than the paper substrate to which it is bonded. The width of the strip is not limited to any specific dimension as will become more evident in accordance with the alternate embodiments to be described forthwith, but should be of a width sufficient to span the weakened zone and bond to both the bonding zones 22.
This arrangement provides a sufficient unattached region overlying the weakened zone to permit the special properties of the selected material for the strip to function as contemplated, that is, to provide for the stretching of the wall and for a volumetric expansion of the bag after an undue stress has caused the perforations to separate, and hence the paper wall to fail at the perforations.
Preferably, the material selected for strip 20 will possess a suitable degree of resistance to stretch or will be elastic to the extent that it will recover all or part of its initial tensile-stretch properties after being exposed to repeated stresses along both its transverse and longitudinal dimensions. Examples of materials for strip 20 having the above properties include a rubber modified high density polyethylene such as W. R. Grace & Company's No. 2201 resin or Phillips Petroleum Companys Marlax TR-lOl, a copolymer having tensile energy recovery of about 50 percent based on about 10 percent elongation in its transverse direction such as DuPonts Alathon 3120, or a latex or rubber sheet such as is used in familiar toy balloons, but having strength and recovery properties adequate to supplement the properties of the paper to which it is to be bonded. The dimension of the free or unattached portion. of strip 20 between adhesive zones 22 will depend on the material, thickness and physical characteristics of the material from which the strip is produced, as well as the properties, size, shape, capacity and contemplated use of the bag.
The bag stock 24 between the bonded edges of strip 20 is weakened so that that portion of the bag wall will break or rupture under stress before any other part of the paper wall structure. After the weakened section ruptures, the plastic material is free to stretch across the rupture in either direction, but especially in the transverse direction to absorb the applied load. In the first illustrated embodiment, weakening of the wall stock 24 was occasioned by perforating the wall along a longitudinally extending line. Altemately, any other means for concentrated undue stress in a known area of the bag wall may be employed. Thus, the stock underlying the bonded edges of strip 20 may be thinner than the remaining wall stock or the stock may be completely separated (as at a seam of the bag). Similarly a dilute acid, caustic, or other cellulosic debilitating chemical may be applied to the bag to produce the desired weakening. The bag may be designed so that rupture of the weakened area occurs immediately upon the application of a force thereto or a delay factor may be introduced which would cause the weakened section to rupture some time after the force is applied. The amount of delay is related to the strength of the weak ened section.
Reference is now made to FIGS. 3 and 4 wherein the novel concept of the present invention is applied to a dual-ply bag 30. Bag 30 comprises inner ply 32 and outer-ply 34 having substantially aligned perforations 36 forming weakened zones in opposing walls 38 and 40. Strips 42 having the characteristics of strip 20 of the previous example are located between the plies overlying the aligned lines of perforations 36 in the opposing walls. If desired, the perforations and strips may be extended into the portion forming the bottom of the bag. Each strip 42 is secured to each of the plies along adhesive zones 44 which, as in the previous example, do not abut the perforations but are spaced apart therefrom thereby forming a zone or region wherein each strip is free and unattached to each of the plies forming the wall.
Again, in lieu of perforations, the wall may be weakened in the areas underlying strips 42 in any of the manners set forth above. Thus, a conventional seam of the bag may be utilized as the weakened area. In this connection, the seam would not be completely glued or bonded during the assembly of the bag, but rather lightly tacked together by spots of adhesive material or other similar means. Alternatively, the conventional seam could be left entirely unglued, in which case, the actual securing of the wall across the seam would be assumed entirely by the strip bonded to the wall on both sides of the seam.
FIGS. and 6 illustrate a further modification of the bag of the present invention. In FIG. 5, bag 50 is formed of multiple plies, as for example, three plies, 52, 54, and 56. The ends of the plies terminate in a seam formation with ply 56 terminating at seam 58, ply 54 terminating at seam 60, and ply 52 terminating at seam 62. The ends of each of the plies substantially overlie one another to form a seam of the bag. As will be noted, the ends of each ply are not secured together. Plastic strip 64 is provided disposed between plies 52 and 54 and extending beyond both seams 60 and 62. One face of strip 64 is secured by suitable bonding agents to ply 52 on both sides of seam 62, along zones 66 and 68. The other face of strip 64 is similarly joined to ply 54 on both sides of seam 60 along bonding zones 70 and 72. The ends of the remaining ply 56, the outer face of which comprises the outside of the bag, are adhesively secured to intermediate ply 54 along zones 74. It will be observed that in the above described structure, the weakened area comprises the unattached seams 60 and 62 of inner and intermediate plies 52 and 54 which are spanned by strip 64.
FIG. 7 shows a further modification. In this instance, the bag comprises an inner ply 82 having a folded end 84 and a straight end 86; and intermediate ply 88 having straight ends 90 and 92; and an outer ply 93 having a folded end 94 and a straight end 96. The folded end 84 of inner ply 82 is bonded to the straight end 86 along longitudinally extending bonding zone 98. A longitudinally extending elastic strip 100, identical to the strips previously described, is provided with the inner face of one edge 102 bonded along bonding zone 104 to inner ply 82 and the outer face of edge 102 bonded along bonding zone 106 to the inner face of end 92. The outer face of end 92 in turn, is bonded to the inner face of end 96 along bonding zone 108 and the outer face of end 96 is bonded to the folded end 524 of outer ply 93. The other end 110 of strip 100 is bonded to the inner face of end 86 along the bonding zone 112. The outer face of end 86, in turn, is bonded to the inner face of end 90 which is bonded to the outer ply 93.
As seen in FIG. 7, strip 100 spans across a weakened section of the bag wall which comprises two plies, whereas the remainder of the bag is formed of three plies. It will be noted that the folded ends 84 and 94 of the inner and outer ply provide excess material at the weakened section which causes a bellow-like action to occur when an undue stress is applied to the bag. The bag will thus expand somewhat prior to the rupture of the weakened section and this expansion thus serves to delay the time of rupture.
FIGS. 8 and 9 depict further modifications of the present invention wherein the container comprises a plastic lined multi-ply bag and the weakened section of the bag wall comprises a zone of fewer plies than the remainder of the bag wall. Thus, in FIG. 8 the wall of bag includes outer ply 122 formed of paper stock and inner ply 124 also formed of paper stock. The ends 126 and 128 of ply 124 are spaced apart from each other. A flap 130 extending from one end of outerply 122 and forming a continuation of the outer-ply spans ends 126 and 128 of inner-ply 124. As in the previous example, flap 130 is longer than the distance between ends 126 and 128 and the flap is suitably folded on itself to neatly absorb the excess material. A plastic liner 132 extends about the inner face of inner-ply 124 and the liner is bonded to ends 126 and 128 along bonding zones 135 located proximal one end 134 of liner 132. The other end 136 of liner 132 underlies end 134 and is bonded to end 134 along bonding zones 137 aligned with bonding zones 135.
In use when the bag is overly filled or otherwise mishandled, stresses due to such mishandling will concentrate at the weakened portion of the bag, namely that area between ends 126 and 128 where only a single ply of paper stock is provided. Initially the forces will tend to unfold the folded portion of flap 130, thereafter they will cause a rupture of the bag at the flap whereafter they will be absorbed by the elastic strip which comprises the portions of the plastic liner underlying the flap. In this embodiment a double ply of the plastic liner material forms the elastic strip. The bag 140 depicted in FIG. 9 is identical to the bag 120 of FIG. 8 with the sole exception that the underlying portion 142 of plastic liner 132 is coupled to only one side of the portion of liner 132 extending across the weakened section of the bag and hence only a single ply of the plastic liner material serves as the elastic member to absorb undue stresses.
Thus, in accordance with the above description the aforementioned objects and advantages are effectively obtained.
Having thus described the invention, what is claimed 1s: 1'. A paper bag comprising continuous wall means; a bottom end and a top end; at least one longitudinally oriented section of said wall means being structurally weaker than the remaining sections of said wall means, said weakened section being sufficiently strong to withstand normal stresses to which said bag may be subjected; and a strip of elastic material overlying said weakened wall section, reinforcing said weakened section, and bonded to said remaining wall sections on bonding zones extending substantially parallel to said weakened section, said elastic strip being free of and unattached to said weakened section whereby when undue dynamic stresses are applied to said bag they are concentrated at said weakened section and are taken up by said elastic strip without rupture of the bag.
2. The paper bag in accordance with claim 1 wherein said wall means comprises a single ply of paper stock and wherein a longitudinally oriented line of perforations is formed in said ply and said elastic strip overlies said line of perforations.
3. The paper bag set forth in claim 2 wherein said wall means further comprises an additional inner-ply of paper stock, said additional ply having a line of perforations substantially aligned with the line of perforations of said first ply and wherein said elastic strip is bonded to said inner-ply.
4. The paper bag as set forth in claim 1 wherein the wall structure comprises multiple plies of paper stock, each ply terminating in opposing ends, corresponding ends of the several plies being adjacent each other and wherein said elastic strip is bonded to opposing ends of certain plies and each of the remaining ends of the plies is bonded to an adjacent end.
5. The paper bag as set forth in claim 1 wherein the wall means comprises a first inner-ply of paper stock, a second intermediate-ply of paper stock, and a third outer-ply of paper stock with the ends of each ply overlapping and wherein said elastic strip overlies the overlapped ends of the first and second plies and is bonded on one face to the ends of the first ply and on the opposite face to the overlapping ends of the second ply, and
means bonding narrow portions on adjacent sides of adjacent ends of the second and third plies together, said narrow portions being located on each side of the area of the overlapping ends of the plies.
6. The paper bag as set forth in claim 1 wherein the wall means comprises a first inner-ply of paper stock having a terminal folded end; a second intermediate ply of paper stock; and a third outer-ply of paper stock having a terminal folded end opposite to the folded end of the first ply; wherein one face of said elastic strip is bonded to the non-folded end of the first ply and to one end of the second ply, the opposite face of the elastic strip is bonded to the other end of the first ply at a point before the terminal folded end of said first ply, and means bonding the folded end of the first ply to said one end of the second ply; means bonding together the non-folded end of the first ply, the other end of the second ply and the folded end of the third ply; and means bonding together the one end of the second ply, the non-folded end of the third ply and the portion of the other end of the third ply adjacent the terminal folded end.