Heavy duty bag

Abstract

 A heavy duty bag for powder or granular material consists of an inner sheet (2) and an outer sheet (4) shifted slightly relative to each other to provide margins for pasting and folded and pasted to form a cylindrical body which is simultaneously formed with an inlet (64) by folding an upper portion (56) of one of the folded portions along substantially triangular lines (50, 52, 54). The upper and lower margins of the cylindrical body are folded and pasted to form the bag.
According to the invention, the bag has a closing strip (66) applied with a hot-melt adhesive at an area (68) arranged to cover the inlet (64) of the bag. The remaining area (70) of the strip (66) is attached with a conventional adhesive in the form of overriding to the upper portion (56) of the bag prior to filling the bag with the material. After filling, the closing strip (66) is urged onto the inlet (64) whilst being heated to cause the area (68) to adhere and thus to prevent material leaking through the inlet (64) during transportation and storage of the bag.
In an embodiment, a flexible film (74) is interposed between the inner sheet (2) and the outer sheet (4) near to the inlet. An upper end (76) of the film (74) extends into the bag to also ensure that material is prevented from leaking through the inlet (64).

Description

[0001] This invention relates to a heavy duty bag having an inside valve, and more particularly to a heavy duty bag for powder or granular material for food or industrial use, such as wheat flour or cement, consisting of an inner and an outer sheet slightly shifted to each other for providing stepwise margins for pasting and folded and pasted to form a cylindrical body which is formed with an inside valve at an upper portion of one of the folded portions and is folded and pasted to form the bag.

[0002] Such a heavy duty bag has been proposed in, for example, Japanese Utility Model Application Publication No. 1,831/66 published on February 9, 1966. However, the bag disclosed in the publication has a disadvantage allowing a powder or granular material filled in the bag to leak through a inside valve during its transportation or storage although the opening is designed to prevent the leakage of the material.

[0003] Accordingly, it is a general object of the invention to provide an improved heavy duty bag which eliminates the disadvantage of the prior art.

[0004] It is a specific object of the invention to provide an improved heavy duty bag of the first mentioned kind for powder or granular material, which comprises a closing strip attached in the form of overriding to an upper portion of the bag except an inside valve and adapted to close the opening with the aid of a hot-melt adhesive after the material has been filled in the bag, thereby preventing the material filled therein from leaking through the inside valve during its transportation or storage.

[0005] It is a further object of the invention to provide an improved heavy duty'bag of the first mentioned kind for powder or granular material which in addition to the closing strip, comprises a flexible film preferably a synthetic resin film in the proximity of the inside valve, thereby completely preventing the material filled therein from leaking through the opening during its transportation or storage.

[0006] In order to achieve the above objects, the heavy duty bag for powder or granular material consisting of an inner and an outer sheet slightly shifted to each other for providing stepwise margins for pasting, said sheets being folded and pasted to form a cylindrical body which is formed with an inside valve by folding an upper portion of one of the folded portions along substantially triangular lines, and said upper and lower margins of said cylindrical body being folded and pasted to form the bag according to the invention, comprises a closing strip attached in the form of overriding to an upper portion of said bag covering over at least part thereof but covering completely said inside valve by a part of the strip whose surface in opposition to said inside valve is applied with a hot-melt adhesive.

[0007] In a preferred embodiment of the invention, the bag further comprises a flexible film interposed between the inner and outer sheets in the proximity of the inside valve and extending somewhat into the bag.

[0008] In order that the invention may be more clearly understood, preferred embodiments will be described, by way of example, with reference to the accompanying drawings.

Fig. 1 is a development view of a typical blank consisting of an inner and an outer sheet for manufacturing a bag according to the invention;

Fig. 2 is a front elevation of a cylindrical body formed by the blank as shown in Fig. 1 as in one step of manufacturing the bag;

Fig. 3 is a sectional view taken along a line III-III in Fig. 2 illustrating an adhesive by small circles on an exaggerated scale;

Fig. 4 is a front elevation of the bag obtained by folding and pasting an upper and a lower portion of the cylindrical body shown in Fig. 2;

Fig. 5 is a plan view of a closing strip to be attached to the bag according to the invention;

Fig. 6 is a front elevation of the bag comprising the closing strip shown in Fig. 5 according to the invention;

Fig. 7 is a perspective view of the bag according to the invention after filled with a powder material but prior to closing an inside valve with the aid of hot-melt adhesive applied to the closing strip;

Fig. 8 is a partial front elevation showing a preferred embodiment of the bag according to the invention comprising a flexible film interposed between an inner and an outer sheet of the bag;

Fig. 9 is a plan view of an upper portion of the bag shown in Fig. 8 opening the upper portion of the bag to disclose the part of the flexible film extending into the bag;

Fig. 10 is a development view of a blank for constituting the bag according to the invention advantageous in avoiding waste sheets of paper;

Fig. 11 is a plan view of a patch piece for reinforcing a single sheet portion of the bag shown in Fig. 10; and

Fig. 12 is a partial front elevation of a cylindrical body formed by the blank shown in Fig. 10 for explaining the single sheet portion of the bag.

[0009] Fig. 1 illustrates an exemplary blank for constituting a bag according to the invention, which consists of an inner sheet 2 and an outer sheet 4 arranged shifted or offset with each other for providing spaces or margins for pasting. In this embodiment, the blank is of kraft paper. However, any kinds of material may be used for this purpose, so long as they are suitable for heavy duty bags. The inner sheet 2 includes an upper projection 6, a bottom portion 8 and upper shoulders 10 and 12 and bottom shoulders 14 and 16 continual to both ends of the inner sheet 2. The outer sheet 4 also includes an upper projection 18, a bottom portion 20 and upper shoulders 22, 24, 26 and 28 and bottom shoulders 30, 32, 34 and 36. Chain lines 38-54 illustrate folding lines among which one-dotted lines 40, 46 and parts of 50 and 52 are outwardly folded lines and two-dotted lines 38, 42, 44, 48 and 54 and parts of 50 and 52 are inwardly folded lines.

[0010] As above described, the inner and outer sheets 2 and 4 are shifted relative to each other as shown in Fig. 1.

[0011] An adhesive is applied to right and left ends of the inner and outer sheets 2 and 4 as viewed in Fig. 1. The sheets are then folded along the folding lines shown in Fig. 1 to form an open ended envelope as shown in Fig. 2. At the same time, the sheets are folded along the lines 50, 52 and 54 into a substantial triangular shape to form an inside valve whose particular function will be explained later. The edges of the inner and outer sheets 2 and 4 at upper and lower portions 56 and 58 are shifted in a stepwise manner as shown in Fig. 2.

[0012] As shown in Fig. 3 which is a schematic sectional view taken along the line III-III in Fig. 2, the adhesive (shown by small circles on an exaggerated scale) is applied to the step portions of the upper and lower portions 56 and 58, which are then folded along lines 60 and 62 to form a bag having a blowing-in opening or inlet 64 which is referred to as "inside valve" for filling powder or granular material into the bag by blowing as shown in Fig. 4. Inwardly extending edges 65 formed by folding the parts of the sheets along the lines 50, 52 and 54 as above described form a check valve for preventing the material from leaking or escaping through the inside valve 64.

[0013] According to the invention, there is provided a rectangular closing strip 66 to be applied to the upper portion 56 as shown in Figs. 5 and 6. The closing strip 66 is coated with a hot-melt adhesive schematically shown by small dots on an area 68 of its one surface, which is sufficient to cover the opening 64 of the bag. A conventional adhesive such as starchy paste is applied to the remaining area 70 of the closing strip 66. The closing strip 66 is inwardly folded along a two-dotted chain line 72 and attached in the form of overriding to the flat upper portion 56 prior to filling the material with the area 70 of the closing strip 66, the area 68 being free from attaching to the bag, to complete the heavy duty bag according to the invention.

[0014] The hot-melt adhesive may be one of thermoplastic resin such as polyolefin resin or polyvinyl acetate. The hot-melt adhesive may be applied all over the surface of the closing strip 66 without using the starchy paste, although it is somewhat expensive. In this embodiment, the closing strip 66 has adjacent sides substantially corresponding to a width and a thickness of the bag completely filled with the material. However, the adjacent sides of the closing strip may be shorter than the width and thickness of the bag.

[0015] The closing strip 66 may be an ornament paper or having patterns illustrating a trademark or quality or weight of the material enclosed therein. The closing strip 66 may be of kraft paper or any other sheets different from that of the bag.

[0016] When the bag is filled with the powder or granular material, it becomes substantially a neat square or rectangular box-shaped bag. The free end of the closing strip is positioned above the inside valve 64. The end area 68 of the closing strip 66 is urged onto the inside valve 64 while heating at 150-200°C to cause the area 68 of the closing strip 66 to adhere to the top of the bag completely concealing it. Even if, the strip is shorter than the width of the bag, at least the inside valve 64 is completely covered by the latest adhered area 68 of the closing strip 64.

[0017] The bag according to the embodiment can therefore prevent the material filled therein from leaking or escaping therefrom during transportation and storage with the aid of the closing strip covering the inside valve in conjunction with the function of the check valve owing to the particular configuration of the inside valve itself.

[0018] Fig. 8 illustrates a second embodiment of the invention, wherein like components have been designated by the same reference numerals as those in the preceding embodiment. A bag partially illustrated in Fig. 8 is similar to the bag shown in Fig. 2 with exception that a flexible film 74 is interposed between an inner and an outer sheet 2 and 4 at folded portion along lines 38, 40 and 42 in the proximity of the lines 50, 52 and 54. As shown in Fig. 9, an upper end 76 of the flexible film 74 somewhat extends in the bag to the right as viewed in this drawing. It is preferable to apply an adhesive in a spot-like manner to the film or any one of sheets to prevent the film from shifting from its initial location therebetween. The flexible film is preferably a synthetic resin film such as polyvinyl chloride but does not preclude any other flexible materials.

[0019] It is of course understood that the bag of the embodiment shown in Fig. 8 is provided with a closing strip 66 identical with that shown in Fig. 5.

[0020] With this arrangement, when the closing strip is urged against an inside valve 64 of the bag while heatig, the extending end of the flexible film is in close contact with an upper inside of the inside valve 64 and a lower portion of the inside valve 64 is then brought in close contact with the upper inside of the opening, thereby effectively and completely preventing the material from leaking through the opening in conjunction with the function of the closing strip.

[0021] Fig. 10 illustrates a preferable blank for a bag according to the invention, cosisting of an inner and an outer sheet 82 and 84. In this drawing, phantom lines 82', 84', 82" and 84" illustrate adjacent blank for the bags to be cut from long blank sheets of paper. As can be seen from the drawing, cutting of respective blanks from the long blank sheets of paper does not cause any waste sheets of paper, which is advantageous in economical viewpoint. However, such economical cutting causes a missing portion 90 in the outer sheet so that the complete bag includes a single paper portion consisting of the inner sheet. A patch piece or reinforcing piece 86 (Fig. 11) of the same paper of the blank is attached to that missing portion of the outer sheet 84 to reinforce the strength of the single paper portion of the bag, thereby avoiding any breaking down of the bag during its transportation or storage.

[0022] As can be seen from the above description, the bag according to the invention can prevent powder or granular material filled therein from leaking or flowing out through an inside valve of the bag during its transportation or storage by the closing strip covering the inside valve. Furthermore, the bag of the preferred embodiment of the invention comprises a flexible film preferably synthetic resin film interposed between the inner and outer papers at folded portions in the proximity of the inside valve, thereby securing the prevention of the material filled therein from leaking or flowing out through the inside valve of the bag in conjunction with the function of the closing strip during the transportation or storage of the bag. The bag according to the invention is very useful in practical use for the above advantages.

[0023] It is further understood by those skilled in the art that the foregoing description is that of preferred embodiments of the disclosed bags and that various changes and modifications may be made in the invention without departing from the spirit and scope thereof.

Claims

1. A heavy duty bag for powder or granular material consisting of an inner and an outer sheet slightly shifted to each other for providing stepwise margins for pasting, said sheets being folded and pasted to form a cylindrical body which is formed with an inside valve by folding an upper portion of one of the folded portions along substantially triangular lines, and said upper and lower margins of said cylindrical body being folded and pasted to form the bag, said bag comprising a closing strip attached in the form of overriding to an upper portion of said bag covering over at least part thereof but covering completely said inside valve by a part of the strip whose surface in opposition to said inside valve is applied with a hot-melt adhesive.

2. A heavy duty bag as set forth in claim 1 wherein said bag further comprises a flexible film interposed between said inner and outer sheets in the proximity of said inside valve and extending somewhat into the bag.

3. A heavy duty bag as set forth in claim 2, wherein said flexible film is attached to at least one of said sheets by a spot-like applied adhesive.

4. A heavy duty bag as set forth in claim 3, wherein said flexible film is a synthetic resin film such as polyvinyl chloride.

5. A heavy duty bag as set forth in claim 1, wherein said closing strip is rectangular having adjacent sides substantially corresponding to a width and a thickness of said bag when completely filled with the material so as to substantially cover the upper surface of the completely filled bag.

6. A heavy duty bag as set forth in claim 1, wherein said closing strip is rectangular which is longitudinally folded and attached to the upper portion of the bag so as to extend over both surfaces of the bag in a flat condition before filling the material.

Drawing