Valve bag

[57] ABSTRACT

A valved plastics bag which has its valve adjacent and parallel to the top of the bag and is constructed of overlapping multi-ply panels in the front wall of the bag, the valve being formed between the panels, and one ply of the inner panel forming a sift-proof flap for the valve.

Claims, 4 Drawing Figures

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PATENTED» 31971

3.833.166

SHEET 1 OF 2

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<img file="US3833166A_D0003.tif" />

FIG. 2

PATENTEDSEP 31974

3,833.166

SHEET 2 OF 2

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<img file="US3833166A_D0005.tif" />

FIG. 4

3,833,166

VALVEBAG

This application is a continuation-in-part of United States application Ser. No. 210,836 filed on Dec. 22, 1971 now abandoned.

This invention relates to plastics valved bags.

Valved bags are in general used for packaging materials such as fertilizers and cement. These bags possess the important commercial advantage of easy filling through a valve structure and self-closing of this valve structure after filling. However, the presence of the valve in the bag structure introduces problems in bag manufacture. In plastics bags suitable for the industrial packaging and shipping of powdered or granular products, it is desirable to attach to the end of the valve sleeve a flap or extension formed of a thinner flexible membrane to provide the required anti-sift characteristics. The complexity of the equipment required to form this type of valve automatically has been a major drawback in plastics valved bag manufacture.

It has now been found that a suitable valved bag can be provided by forming the valve between separate panels of the front wall of the bag, and can be very easily manufactured by means of automatic bag making equipment.

In accordance with the invention, a plastics valved bag of the type comprising a back wall and a front wall joined together around the entire periphery of the bag, the front wall consisting of a first panel and a second panel, of greater combined width than the width of the back wall, said first panel at least partially overlapping said second panel throughout the length of the bag and said panels in their common area being joined together along a line substantially parallel with and at a distance from one end of the bag, thus forming a tubular selfclosing filling sleeve extending transversely of the bag adjacent to said one end thereof, with said second panel forming the inner wall of said filling sleeve, and being also joined together along at least one line extending from said first-mentioned line substantially to the opposite end of the bag, is characterized in that said second panel consists of at least two plies that are noncoextensive with each other so that at least the end portion of the inner wall of said filling sleeve is formed of a number of plies that is less than the total number of plies in said second panel.

Preferably the back wall and the two panels of the front wall all have the same number of plies, and in such case the front panels are preferably integral with the back panel, being joined to it by folds. A particularly preferred form of the bag has two plies in the back wall and in the front panels; such a bag may be made very conveniently from flattened tubular film. In such a two-ply bag, the edge of the first front panel is preferably constituted by a fold joining the plies. This may be one of the side folds of the tubular film, which may then be slit along the other fold, or, more usually, along a line close to and parallel therewith, to provide the separate plies, coextensive or non-coextensive, of the second front panel.

Two embodiments of the bag of this invention will now be more particularly described by way of example with reference to the accompanying drawings, of which;

FIG. 1 is an elevational view of the first embodiment of the bag;

FIG. 2 is a sectional view along line II—II of FIG. 1;

FIG. 3 is an elevational view of the second and preferred embodiment of the bag; and

FIG. 4 is a sectional view along line II—II of FIG. 3.

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

In FIGS. 1 and 2 is shown a generally rectangular pillow-type bag, 10, having a single-ply back wall 11 and a front wall made of first and second partially overlapping panels 12 and 13. As shown, the first panel 12 is single-ply while the second panel 13 has two plies 16 and 17. Panel 12 and outer ply 17 of panel 13 are integral with back wall 11 and thus form with the back wall a flattened single-ply tube, which is closed at both ends by transverse seals 14 and 15. Panel 13 lies beneath panel 12 in the area of overlap, and the free edge of its inner ply 16 which is a strip of film extending the whole length of the bag and being somewhat wider than ply 17, projects somewhat beyond the free edge of outer ply 17. A seal 18 unites both plies of panel 13 with panel 12, and a seal 19 unites the projecting end of ply 16 of panel 13 with panel 12. The portion left unsealed in the common area of overlap at the top end of the bag constitutes a tubular valve sleeve suitable for insertion of a filling spout. The top ends of seals 18 and 19, together with dot seals 20 delineate the tubular valve sleeve. When the bag has been filled, the projecting end portion of the inner ply 16 of panel 13 acts as a siftproof closing flap for the valve.

In FIGS. 3 and 4 is again shown a generally rectangular pillow-type bag, 10, having a two-ply back wall 21 and a front wall made of two-ply partially overlapping panels, the said first panel being shown at 22 and the second at 13. Panels 22 and 13 are integral with back wall 21 and thus form with the back wall a flattened two-ply tube, which is closed at both ends by transverse seals 14 and 15. Panel 13 lies beneath panel 22 in the area of overlap, and the free edge of its inner ply 16 projects somewhat beyond the free edge of its outer ply 17. A seal, 18, unites both plies of panel 13 with the two plies of panel 22, and a seal, 19, unites the projecting end of ply 16 of panel 13 with the two plies of panel 22. The portion left unsealed in the common area of overlap at the top end of the bag constitutes a tubular valve sleeve, suitable for insertion of a filling spout. The top ends of seals 18 and 19, together with dot seals 20, delineate the tubular valve sleeve. When the bag has been filled, the projecting end portion of the inner ply 16 of panel 13 acts a siftproof closing flap for the valve.

Although in the particular embodiment of the invention described with reference to FIGS. 1 to 4, the end of the valve sleeve is shown as being formed out of a projecting portion of the inner ply 16 of panel 13, it should be understood that it can alternatively be formed by a portion of outer ply 17 projecting beyond the edge of inner ply 16. In other words, either one of plies 16 and 17 can project beyond the edge of the other to form the valve closing flap. Seal 19, while not being essential, prevents the contents of the filled bag from entering the space between the panels, from which it might not be easily emptied. Dot seals 20 may be replaced by a continuous seal extending substan

3,833,166 tially parallel to transverse seal 14 from the top end of seal 18 to the inward edge of ply 16.

While, in the drawings, the valve opening of each bag is shown as being located close to one side of the bag, it should be understood that it can be located anywhere adjacent to the end seal 14 of the bag, provided that sufficient space is left between its inner mouth and the side of the bag facing it to allow insertion of a reasonably long filling spout and free delivery of filling material therefrom. Generally, it is preferred to arrange the front panels so that the valve opening is located within one vertical half of the bag, with the valve sleeve extending into or towards the other vertical half. The width of the wider front panel will not significantly exceed, and preferably is less than, the width of the back wall.

It is preferred that the longitudinal seals between the front panels, shown at 18 and 19 in FIGS. 1 and 3, stop short of and thus do not intersect transverse seal 15 at the bottom of the bag. Such intersection might result in weakening of the end seal at the points of intersection, and thus in weakening of the bottom of the bag.

The bags are preferably made from plastics tubular film of appropriate width. Preferably the plastics film is readily heat-sealable, or is provided with a heatsealable coating. Films of olefine polymer or copolymer, or of polyvinyl chloride, are very suitable. Film of lowdensity polyethylene is particularly suitable because of its inherent heat-sealability, its toughness, and its low cost.

The bags illustrated in FIGS. 2 and 3 may each be made by continuously feeding a flattened tubing to a bag making machine, where one wall of the tubing is slit longitudinally close to one fold and that fold is thereafter unfolded. A longitudinally folded web results, having one ply somewhat wider than the other; such a web may of course, alternatively be formed by longitudinally folding a length of single sheet of the film. The web is then passed over a suitable A-frame where it is folded longitudinally to form a double-ply tubing adapted to form the back wall and the overlapping front panels of the bags. The common area between the front panels is provided at regular longitudinal intervals with the required longitudinal and transverse seals to join them together and provide the valve sleeves of successive bags. The double-ply tubing is finally transversely sealed and cut at regular intervals to provide bags as shown in the drawings. The bags may of course alternatively be made by longitudinally sealing separate sheets to provide the back wall and front panels of the bag, or any part or parts thereof, and to form the tubular web from which successive bags may be sealed and severed.

Where it is desired to make bags such as shown in FIGS. 1 and 2, a web of proper width is continuously fed to a bag making machine where it is folded longitudinally to provide the back wall 11 and overlapping panel 12 and outer ply 17 of panel 13. A single-ply tubing is so formed into which is also continuously fed a strip of film which forms inner ply 16 of panel 13. The formation of the bag is then as hereinbefore defined for the double-ply bags.

It should be understood that the principles of the invention are applicable to the fabrication of bags having walls comprising more than two plies, e.g. three plies, four plies, etc. The important feature in all such bags is that one ply of panel 13 of the bags, preferably the innermost ply projects some distance beyond the edge of the other plies and constitutes a sift-proof closing flap for the filling sleeve.

In the foregoing description, the invention has been described in connection with bags where only second panel 13 is double ply or where the back wall and first and second panels of the front wall comprise a similar number of plies. It is within the scope of this invention, however, to provide bags wherein at least one of the back wall and two panels making the front wall comprises an individual additional ply. In such bags the additional ply is united to the other ply or plies of the bag only by top and bottom seals 14 and 15. Where, however, said additional ply is part of one or both panels of the front wall, it can be united to the other plies of said panels in the common area of overlap such as along seals 18, 19 and 20.

Bags comprising an additional ply as above described can be fabricated by simple adaptation of the method outlined hereinabove for making bags such as illustrated in FIGS. 1 to 4.

It is not necessary for all plies of the bag to be made of the same material. In the case of the twoply bag it has been found advantageous to make the innermost ply of a plastics material that melts at a higher temperature than the plastics material of the outermost ply. Such bags are particularly useful in applications in which materials such as, for example, crystalline or powdered chemicals or pigments, are packed into the bags while hot. In one particularly preferred form of such a bag, the inner ply is formed of film of highdensity polyethylene, and the outer ply is formed of low-density polyethylene. The inner ply then allows the bag to be filled with material at a temperature considerably higher than could be tolerated by a double-walled bag of low-density polyethylene film, but the outer ply, supported by the inner ply while hot, provides on cooling a wall of higher strength than would be the case with a double-walled bag of high-density polyethylene film. Other combinations of films may be selected to provide characteristics suited to particular applications. Where only the second panel of the front wall consists of two plies, the inner ply may be, for example, of a plastics material more flexible than that used for the remaining construction of the bag.