US3456868A - Bag - Google Patents

Description

July 22, 1969 A, A, SNABB ET AL BAG Filed April 30, 1968 FIG.2

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United States Patent O 3,456,868 BAG Avron A. Snabb, Minneapolis, and Ralph C. Goodwin,

Wayzata, Minn., assignors to Bemis Company, Inc.,

Minneapolis, Minn., a corporation of Missouri Filed Apr. 30, 1968, Ser. No. 725,444 Int. Cl. B65d 33/00, 31/14 U.S. Cl. 229-66 4 Claims ABSTRACT OF THE DISCLOSURE A plastic bag having heat-seal-inhibiting material on the inside in a pattern for preventing wall-to-Wall sealing across a major portion of the width of the tube during the heat-sealing of an end closure to achieve a substantially peel-free closure, with a corner area free of the heat-seal-inhibiting material to allow wall-to-wall sealing in that area upon heat-sealing of the end closure, and further having a slit extending inward adjacent that corner to facilitate tearing the bag open.

Background of the invention This invention is in the field of plastic bags, more particularly heavy-duty plastic bags, made from polyethylene or the like.

One type of heavy-duty polyethylene bag which has been on the market is a bag made from a length of polyethlylene tubing having end closures each constituted by a polyethylene tape folded around the respective end of the bag and heat-sealed to the front and back walls of the bag, the tubing being provided on the inside with heat-seal-inhibiting materia1 at its ends so that the bag walls are wholly free of any face-to-face seal therebetween at the ends of the bag from one side thereof to the other. This desirably provides closures in which stresses incurred on dropping or other rough handling of the bag are taken by the seals between the tapes and the bag walls in shear rather than in peel, these seals being strongly resistant to separation in shear. A problem attendant upon such a bag is that of providing for easy opening of the bag without having to cut it open, noting that since it is made of heavy-duty polyethylene, it is ditiicult to tear it open witho-ut a starting slit or other line of weakness, without making the bag subject to being torn open at the slit or line of weakness due to rough handling, and without introducing the possibility of undue leakage of the bag contents through the slit.

Summary of the invention Among the several objects of the invention may be noted the provision of a plastic bag such as above described desirably retaining substantially the full advantage of the shear-stressed rather than the peel-stressed type of closure and having an easy-opening feature involving the provision of a slit or other line of weakness at an edge of the bag adjacent a corner of the bag functioning as a starter for tearing the bag open at its end; the provision of such a bag which is not prone to being torn open at the slit or other line of weakness due t dropping or other rough handling of the bag; and the provision of `such a bag having a slit as described as to which leakage of the contents of the bag (e.g., relatively finely divided material such as fertilizer) through the slit is minimized.

3,456,868 Patented July 22, 1969 ICC In general, a bag made in accordance with this invention comprises a tube made of flexible heat-scalable sheet material having opposed Walls, the tube having an end closure comprising two additional layers of exible heatscalable sheet material, with said layers and walls being heat-sealed together along a line of seal extending transversely across the tube throughout the width of the tube. The tube is provided with heat-seal-inhibiting material on the inside thereof at said end in register with said line of seal terminating short of one side of the bag and precluding heat-sealing together of the inside faces of said walls along said line of seal except for the region between said one side of the bag and the adjacent end of the heat-seal-inhibiting material where the walls are sealed together in inside face to inside face relation along said line of seal. A line of weakness is provided in both walls of the bag extending inward from said one side of the bag inward of and adjacent said line of seal.

Brief description of the drawings FIG. 1 is a view in elevation of a flat plastic valve bag of this invention;

FIG. 2 is an enlarged view in elevation of the lower left corner of the valve bag of FIG. 1;

FIG. 3 is a view in elevation of a length of flat plastic material of which a bag of this invention is made, broken away in part;

FIGS. 4 and 5 are sections of the bag taken on lines 4-4 and 5 5, respectively, of FIG. 1, with thicknesses exaggerated; and

FIGS. 6 and 7 are enlarged sections taken on lines 66 and 7-7, respectively, of FIG. 2 with thicknesses exaggerated.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

Description of the preferred embodiment Referring to the drawings, there is indicated at 1 a at plastic valve bag made of heat-sealable sheet plastic material, e.g., polyethylene, having a front wall 3 and a back wall 5, a back seam 7 in the back Wall 5, as may best be seen in FIGS. 4 and 5, and side edges 9` and 11 constituted by folds in the material. These folds appear in FIG. 3, which shows the tube opened up. While a seamed bag is shown, it is contemplated that the bag might also be made from seamless tubing. As shown in FIG. 1, the bag has at its upper left corner a valve 15 of the type disclosed in Heimos U.S. Patent 3,281,060, issued Oct. 25, 1966, permitting the bag to be filled by means of a filling spout. A top end closure is indicated at 17 and a bottom end closure at 19.

It will be understood that bags as shown in FIG. 1 may be made by forming a continuous web of polyethylene into tubing, segmenting the tubing into individual bag tubes, and forming each such tube with valve 15 and the end closures 17 and 19. Each such tube, shown opened up in FIG. 3, is specially prepared in accordance with this invention by applying to the surface of the web which will become the inside surface of a tube a coaing of heat-seal-inhibiting material (i.e., polyamide-based ink of a type such as is used in preparing the valve 15 in accordance with said U.S. Patent 3,281,060), in a suitable pattern comprising bands 23, 25 and 27 at the top and bands 29', 31 and 33 at the bottom. Band 27, as may be seen by reference to said patent, is utilized in the formation of the valve 15. Bands 31 and 25 are also shown in outline form by heavy dashed lines in FIGS. l and 2. It is to be especially noted that the bands of heat-seal-inhibiting material terminate short of the side edges or folds 9 and 11 so that the bag walls at the ends of the bag in the areas immediately adjacent the lower corners and upper right corner are free of the heat-sealinhibiting material for reasons which will be explained hereinbelow. It will be understood that the pattern of heat-seal-inhibiting material shown in FIG. 3 may most advantageously be applied to the web of polyethylene during the process in which continuous bag tubing is formed and then segmented into individual bag tubes. Although only narrow bands of heat-seal-inhibiting material are shown, it is contemplated that suitable patterns of heat-seal-inhibiting material could simultaneously be applied not only to inhibit sealing but for other purposes as well, e.g., decorative printing.

Each end closure 17 and 19 comprises a tape of heatsealable sheet plastic material such as polyethylene folded around the lrespective end of the bag tube and heat-sealed to the walls 3 and 5 of the bag along a line of seal 43 extending transversely across the tube throughout the width of the tube. The two halves of the folded tape are designated 45. Due to the interposition of the heatseal-inhibiting material between the walls of the tube, heat-sealing together of the inside faces of the walls of the bag is precluded along the line of seal except for the regions between the side edges 9 and 11 of the bag and the adjacent ends of the bands of heat-seal-inhibiting material where the walls of the bag are sealed together in inside face to inside face relation along the line of seal.

This is illustrated in FIGS. 6 and 7, FIG. 6 showing how bands 31 and 33 preclude heat-sealing together of the inside faces of the bag walls at 47 throughout the extent of these bands, and FIG. 7 showing how seal 43 penetrates through at 49 in the region outward of the ends of these bands to effect sealing together of the walls in this region, and also heat-sealing together of the two halves 45 of the folded tape where it extends beyond the side edge of the bag.

To form an end closure of maximum strength, it is desirable that the inside faces of the walls of the bag along at least a substantial portion of the end of the bag be prevented from sealing together so that stresses resulting from dropping or other rough handling of the filled bag are taken in shear by the seals between the tape closure and the outer surfaces of the bag walls, rather than in peel, as would be the case if the walls of the bag were permitted to seal together in face-to-face relation y at the inner surfaces thereof. As above described, the bag walls are prevented from sealing together along a substantial portion of the bag ends in the areas to which heat-seal-inhibiting material has been applied, eg., bands 25 and 31 as outlined by dashed lines in FIG. l for this purpose. While the walls are allowed to seal together at 49 in the areas immediately adjacent both lower corners and the upper right corner, this does not materially detract from the freedom from peel stress of the seals, and has advantages as will appear below.

In accordance with the present invention, a slit 51 is provided in one side edge of the bag adjacent the folded tape bottom end closure 19, as indicated in FIGS. 2 and 7. Slit 51 constitutes a line of weakness which functions as a starter for facilitating tearing the bag open. In this respect, the protruding end 53 of tape closure 19 is adapted to be grasped and pulled for tearing off the closure 19 and a portion of the bag walls 3 and 5 starting at the slit. It may be noted that slit 51 would also provide a line of weakness along which the bag could accidentally or prematurely rupture when subjected to the stresses due to dropping or other rough handling were it not for the face-to-face seal 49 between the walls 3 and 5 of the bag which holds the walls in close proximity adjacent the slit to reduce the likelihood of accidental or premature rupture of the bag by taking the strain olf the walls in the region of the slit. Also, in holding the walls in close proximity at the bag corners, the face-toface seal 49 provides a corner of greater rigidity which is more easily grasped for tearing open the bag.

While the tear starter is herein illustrated as a slit, it will be apparent to those skilled in the art that the use of other types of lines of weakness, eg., a notch, imperforate score line, or a line of perforations, would achieve the objects of the present invention and, in the ease of a score line, provide the additional advantage of preventing any moisture or finely-comminuted product from passing through the line of weakness yet providing for a bag which may be easily opened.

While the slit 51 is shown illustratively in the side edge near only one corner of the bag, it will be readily apparent that the objects of the invention could also be achieved by placing the slit near another corner or plurality of corners.

An additional advantage of this invention is that it desirably provides for venting of entrained air, i.e., air entrapped in the bag upon filling, while reducing the possibility of moisture entering the bag so as to avoid caking of the contents of the bag. FIG. 7 shows how application of the end closure 19 provides an air vent channel 55 through which entrained air may escape from the bag between the bottom end 57 of the tube and the fold of tape 19'. Similar vent channels are created at the upper right and lower right corners of the bag. Since the walls 3 and 5 of the bag are sealed together above the vent channel but are not sealed in the area outlined by dashed line 31, the vent channel of a bag of this invention is substantially longer than in bags of the prior art wherein heat-seal-inhibiting material prevented the walls from sealing together along the entire length of the end closure as thus created only a short vent channel in the projecting end of the tape. The provision of a longer vent channel provides for venting of entrained air while reducing entry of moisture, also reducing leakage of the contents.

It will further be seen that slit 51 serves to enhance the attainment of these same objects because the walls 3 and 5 of the bag are held in close proximity to each other in the area of the slit by the sealing of the bag walls at 49, thereby allowing entrained air to escape through the slit under pressure but otherwise tending to keep the slit closed against leakage and entry of moisture when the bag has been illed.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A bag comprising a tube made of -exible heat-sealable sheet material having opposed walls, and having an end closure comprising two additional layers of flexible heat-sealable sheet material, said layers and walls being heat-sealed together along a line of seal extending transversely across the tube throughout the width of the tube, said tube having heat-seal-inhibiting material on the inside thereof at said end in register with said line of seal terminating short of one side of the bag precluding heatsealing together of the inside faces of said walls along said line of seal except for the region between said one side of the bag and the adjacent end of the heat-seal-inhibiting material where the walls are sealed together in inside face to inside face relation along said line of seal, and a line of weakness in both walls of the bag extending inward from said one side of the bag inward of and adjacent said line of seal.

2. A bag as set forth in claim 1 wherein said line of 4. A bag as set forth in claim 3 wherein said line of weakness is a slit in both walls of the bag. weakness is a slit in both walls of the bag.

3. A bag as set forth in claim 1 wherein said end closure comprises a tape of exible heat-sealable sheet material References Cited folded around one end of the tube, one side of the folded 5 UNITED STATES PATENTS tape being heat-sealed only to the outside of one wall and the other side of the folded tape being heat-sealed gZig/sut' only to the outside of the other wall along said line of 3:394871 7 /1968 Williams et ai: 229 62 5 seal throughout the extent of said heat-seal-inhibiting material, and both sides of the tape and both walls of the 10 DAVID M. BOCKENEK, Primary Examiner bag all being heat-sealed together along said line of seal between said one side of the bag and the adjacent end of U'S' C1 X'R' heat-seal-inhibiting material. 150-9; 229--62.5

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