Synthetic resin film bag having valve for preventing free leakage

Abstract

A synthetic resin film bag having a valved opening defined by a set of plied films sealed to a base film or sheet which forms the bag per se. The plied films consist of a long leg and a short leg, one edge of the short leg being heat sealed to the long leg, while the combination is in turn heat sealed to the base film or sheet. The base sheet or film is folded upon itself and sealed, the only opening remaining, for the filling operation, is the valved opening, such preventing any contents of the bag from easily escaping subsequent to completion of the filling operation. In addition, the valved opening further includes a slit or a plurality of apertures provided within an area of the long leg which is not heat sealed with respect to the short leg, such slit or apertures serving to perform the function of a pressure relief valve or as means to facilitate opening of the bag when desired after the bag has been filled with its contents.

Parent Case Text

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part application of application Ser. No. 276,558 filed July 31, 1972 now abandoned.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to synthetic resin film bags and more particularly to a flexible synthetic resin film bag having a valved opening for preventing leakage of the contents of the bag without the necessity of expressly sealing the opening.

2. Description of the Prior Art

Conventional synthetic resin film bags are sealed after being filled with contents through one side of the bag, the sealing of the opening of such a bag being done by heat-sealing since the base film is normally made of a thermoplastic resin. However, when the contents are filled via such an opening in the bag, the contents adhere to the inner surfaces of the opening causing the heat-sealing of such opening to be difficult to complete.

In order to obviate this problem, other conventional synthetic resin film bags have employed valves which need not be heat sealed in order to prevent leakage of the bag contents therefrom under normal conditions. However, if excess pressure builds up within the bag, either within a short period of time or over an extended period of time, such conventional valves tend to be blown open whereupon the contents of the bag may become discharged therefrom.

Still further, although such conventional valves facilitate the filling operation associated with the bags and the closing of such bags, it is sometimes difficult to open such bags when desired due to the presence of the contents therewithin relative to the location of the bag valve means.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide an improved synthethic resin film bag.

Another object of the present invention is to provide an improved synthetic resin film bag which can be simply and continuously prepared.

Still another object of the present invention is to provide an improved synthetic resin film bag which has a valved opening to prevent leakage of the contents therefrom without the necessity of expressly sealing the opening subsequent to the filling operation.

Yet another object of the present invention is to provide an improved synthetic resin film bag which has a valved opening which will prevent the contents of the bag from being expelled therefrom even under pressure conditions.

A further object of the present invention is to provide an improved synthetic resin film bag which has a valved opening which will facilitate opening of the bag when desired after such bag has been filled with particular contents.

The foregoing objectives are achieved according to this invention through the provision of a synthetic resin film bag made of a flexible base film or sheet having a valved opening defining an entrance port formed by a base film or sheet and a set of plied films consisting of a long leg and a short leg, wherein one end of the short leg is sealed upon the long leg, and both sides edges of the plied films are heat sealed to the base film, by a mass production process, thereby preventing any contents of the bag from easily escaping. A slit or a plurality of apertures are also provided within an area of the long leg which is not heat sealed with respect to the short leg, such slit or apertures serving to perform the function of a pressure relief valve or as means to facilitate opening of the bag when desired after the bag has been filled with its contents.

BRIEF DESCRIPTION OF THE DRAWINGS

Various other objects, features, and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood from the following detailed description when considered in connection with the accompanying drawings, in which like reference characters designate like or corresponding parts throughout the several views, and wherein:

FIG. 1 is a perspective view, partly in cross-section, of one embodiment of the bag constructed according to this invention;

FIG. 2 is an enlarged view of the valve opening of the bag illustrated in FIG. 1;

FIG. 3 is a view of the valve used in the present invention showing its cooperative parts before being sealed to the bag per se;

FIG. 4 is another view of the valve illustrated in FIG. 3 in an expanded condition, as it would be during the bag filling process,

FIG. 5 is a sectional view of the bag as illustrated in FIG. 1, taken along line A-A' of FIG. 1;

FIG. 6 is a sectional view of the bag as illustrated in FIG. 1, taken along the line B-B' of FIG. 1;

FIG. 7 is a sectional view of the bag as illustrated in FIG. 1, taken along line C-C' of FIG. 1;

FIG. 8 is an enlarged sectional view of the bag as illustrated in FIG. 1, taken along line A-A' of FIG. 1, wherein the bag is filled with packed material and shows the condition of the opening of the bag when filled;

FIG. 9 is a view of another embodiment of the valve utilized in the present invention, showing its cooperative parts before being sealed to the bag per se;

FIG. 10 is a view of still another embodiment of the valve utilized in the present invention, showing its cooperative parts before being sealed to the bag per se;

FIG. 11 is a view of a further embodiment of the valve utilized in the present invention, showing its cooperative parts before being sealed to the bag per se; and

FIG. 12 is a view similar to that of FIG. 8 illustrating the function of the slits within the valve of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, and more particularly to FIGS. 1 and 3 thereof, the synthetic resin film bag 1 of the present invention is folded over and sealed along its ends 11 and 11', as well as its side 12 except for a region defining opening 2. Within the opening 2, there is fixed a set of flexible synthetic resin plied films 3, and as shown in FIG. 3, the plied films 3 can be formed from two flexible sheets consisting of a long leg 3' and a short leg 3". One end 7 of the short leg 3" is heat sealed to the long leg 3' so as to form a set of overlapping plied films, while both longitudinal side edges, or in other words, those side edges extending parallel to the central axis of the opening 2, of the set of plied films 3 are in turn heat sealed to one of the inner surfaces of the folded base film or sheet comprising bag 1.

Referring particularly to FIG. 1, the plied films 3 may first be fixed to one of the inner surfaces of bag 1 at only its lower edge 4', while the upper edge 4 of the plied films 3 may be fixed to the inner surfaces of both base films or sheets which form the bag per se. The ends of the base films are then heat-sealed to form the heat-sealed end 11. The base film thickness for making a bag ranges from 1/100mm to 1mm.

Referring particularly to FIG. 2, the plied films 3 may alternatively be fixed to only one of the base films 1 at its upper edge 4 and its lower edge 4', so that the opening 2 is displaced relative to that sheet or base film of the bag. In either case, the plied films 3 for the opening 2 is fixed to at least one of the base films 1 at both the upper and lower edges 4, 4' respectively, such that the short leg 3" is within the long leg 3' and within opening 2.

The bag 1 including the valve opening 2 consisting of the base film and the plied films 3 is then cut and heat-sealed to a specific size, the edge 12 of the base films being fixed relative to the end of the valve opening 2 such that the inner surface of one of the base films 1 is fixed to one surface of the long leg 3', along the line 6 (see FIGS. 5 and 8) thereby forming a bag which is completely enclosed and sealed except for the portion defining valve opening 2.

Referring now to FIGS. 7 and 8, the valve action may be described. Flowable material is fed through the opening 2 of the plied films. As the plied films 3 may be fixed upon the inner surface of one base film, only, the plied films are pressed toward that one inner surface of the base film by the contents of the bag thereby serving to close the opening of the bag. Even though the contents flow between the long leg 3' and the base film, leakage is prevented by the contact of the short leg, with the long leg, as well as with the base film 1. The invention thus provides a double valve effect due to the action of the long and short legs of the plied films.

The synthetic resin used in manufacturing the bag of the present invention may be for example, polyethylene; polypropylene; polyvinylchloride; nylon; vinylester copolymers, such as, for example, a copolymer of ethylele and vinylacetate; or any other polymers and copolymers capable of forming flexible films. It is also possible to use complex films made of a synthetic resin film laminated with paper, aluminium foil, fabric or other sheets.

The valve opening 2 is usually located at an upper corner of the bag 1, although it is possible to form the opening at any portion along a seam of the bag if required. It is usual to make the plied films from a more flexible film than that of the base film of the bag in order to make the valve action more effective. A thickness of 1/100mm to 1mm is used for the base film.

The difference in length between the longer leg and the shorter leg depends upon the nature of the contents of the bag. When the length of the long leg is increased compared to the width of the opening any tendency for leakage from the bag is decreased but problems may arise in the filling operation. Accordingly, the length of the long leg is thus determined by such considerations. Where the bag is used for the package of powder, granules, grain, liquid, and gas, it is preferable that the length of the longer leg be approximately equal to the width of the opening or longer, while the length of the short leg should exceed one-fourth, and preferably be about four-fifths, the length of the long leg. For example, in packing granules, such as, for example, granular fertilizer it is preferable that the difference of lengths between the long and short legs be about 50 mm when the width of the opening is 140 mm (the thickness of the plied films being about 100 mm). The length of the long leg should thus be longer than the width of the opening (140 mm), for if the length of the long leg is shorter than the width of the opening, the tendency towards leakage is increased.

Where the bag is used for carrying powder, it is preferable to increase the difference of lengths between long and shorter legs by increasing the length of the long leg. On the other hand, where a liquid such as water is packed, the width of the opening is decreased and the length of the long leg is increased. Where the contents are fine particles and a high efficiency valve is required, the long leg 3' of the plied films can be made of two pieces of flexible film, the pieces being of equal or unequal length. In the instance where unequal length pieces are utilized, the longer piece will nevertheless be of such length so as to overlap the short leg 3" of the plied films.

When the powder, granules, grain, liquid and gas is to be removed from the bag, the valve 2 can be easily opened by providing an elongated slit 8 upon the long leg 3', as seen in FIG. 9. The slit 8 is formed upon an area of the long leg 3' which is not heat sealed with respect to the short leg 3". In lieu of the slit 8, it is also possible to provide a line comprised of a plurality of linear apertures 8 as seen in FIG. 10, by which the line may be broken so as to form a single elongated slit when the bag is packed, transferred or handled, and when the valve is desired to be opened for removing the contents therefrom. As may also be seen from FIG. 11, another embodiment of the valve may include V-shaped slits 8 serially disposed within a line extending along the width of the long leg 3'.

The function of the valve slits 8 can be readily appreciated with particular reference to FIG. 12. After the bag has been filled with any one of its particular type contents, should the bag be subjected to a force, such as that denoted by and applied thereto in the direction F, as might occur during shipping and handling thereof, the surface of the bag upon which the force is impressed will of course be depressed tending to laterally expand the bag in reaction thereto. Within a conventionally valved bag, such reaction would tend to expel the bag contents out of the bag past the valve members 3' and 3", leakage thereby resulting.

With the valve of the present invention however, due to the presence of the slits 8 provided within the long leg member 3', a flow pattern, as denoted by the arrows, is set up within the bag contents in response to the application of force F whereupon in lieu of the contents being forced out of the bag past the valve members 3' and 3", the contents of the bag interposed, for example, between the short leg member 3" and the long leg member 3', will be forced through the slits 8 and into the main portion of the bag, the valve thereby acting as a pressure relief valve whereupon leakage from the bag is substantially prevented or reduced.

Similarly, the valve facilitates opening of the bag when it is desired to remove the contents therefrom. When for example, means are inserted within the valve opening 2 so as to open the valve means, the short leg member 3" will be pushed inwardly toward the long leg member 3' whereupon the bag contents interposed, for example, between the leg members will again be forced through the slits 8 and into the main portion of the bag. Without such slits, opening of conventionally valved bags has been substantially difficult.

There have been various difficulties encountered in mass producing the bags having the described structure. One of the difficulties is to fix the appropriate surfaces of the base films to the appropriate surfaces of the plied films without sealing the inner surfaces of the long leg 3', so as to thereby close opening 2. In the heat sealing operation, a non-adhering insert such as cellophane or paper-aluminium foil can be inserted within the opening to overcome this problem. However, this method may lead to disadvantages in the form of low efficiency and variable quality of production.

According to the improved operation of the present invention, the inner surfaces of the prefabricated plied films are coated with non-adhesive material so as not to adhere to each other in the heat sealing process. Such material may also be coated upon the base film of bag 1 in the region of opening 2. The non-adhesive material may be polyamide; a cross-linked rubber; or a polymer having a high melting point such as, for example, cellulose nitrate, ink, paint containing an inorganic or heat resistant pigment, and silicon oil. It has been found that the use of printing ink containing such a non-adhesive material is preferred.

In production, the coated prefabricated plied films are automatically adjusted to the edge line of the inner surface of the base film of the bag which is continuously supplied, and then heat sealed to it at the appropriate positions as discussed heretofore. The base film is then heat cut, and folded so as to form a bag, adhering the end of the base film corresponding to the edge 12 (see FIG. 2) of the bag 1 with an adhesive composition, and sealed at the top and bottom edges of the bag, the edges of the bag being continuously heat sealed by a belt type heat sealer. The adhesive composition may be one having affinity to the base film, such as for example, a melt of low density of polyethylene; or a copolymer of ethylele, such as, for example, ethylene vinylacetate copolymer; or a hot melt adhesive prepared by admixing low density polyethylene with an ethylene-vinylacetate copolymer and a modifier. The modifiers may be, for example, wood resins, tall oil rosins, alpha pinene rosins, maleic acids, hardened rosins, cumaroneindene rosins, polystyrene resins having a 25.degree. - 125.degree.C softening point, ketone resins, cumarone resins, non-reactive phenolic resins, dibutylphthalate terpene resins and .beta.-pinene resins, or the like.

The invention is further illustrated by the following examples:

EXAMPLE 1

A bag 440 mm in width and 540 mm in length was prepared by using a film having a 0.20 mm thickness made from a copolymer of ethylene and vinylacetate containing about 5% by weight a vinylacetate component. A set of plied films, consisting of two films, for long and short legs respectively, was used and was fixed upon the inner surface of the base film of the bag. The short leg of the plied films was a film 70 mm in length and 130 mm in width, while the long leg of the plied films was a film 120 mm in length and 130 mm in width. The film for the plied films was of the same material as the base film of the bag, but only 0.15 mm in thickness.

Non-adhesive material was coated upon the inner surface of the short leg at the end of the plied films in a strip 20 mm in length and 100 mm in width, such strips being positioned 15 mm from those portions corresponding to the upper and lower parts of the opening. The non-adhesive material used was Glavia ink for polyethylene printing (Type PKH-391 Blue manufactured by Toyo Ink Mfg. C.) and was coated to a thickness about two or three times the thickness of the film.

The long leg and the short leg were presealed to form the plied films, and the end of the plied films was adjusted to the edge of the base film of the bag, the plied films then being heat-sealed at its upper and lower edges 4 and 4' respectively, the width of the sealing edges being 15 mm. Accordingly, the width of the opening of the plied films was 100 mm. The top and bottom parts of the base film of the bag were respectively heat cut and sealed, while the edge having the plied films was heat sealed by a belt type heat sealer to continuously prepare the bag. The opening could be easily opened and a nozzle of a packaging machine was inserted without trouble. Twenty-five kg of calcium silicate powder for fertilizer was packed within the bag and the bag was then dropped from a height of 2.5 m. Leakage of the contents was then measured. Such measurements were carried out for five such drop tests with the opening facing the ground, and subsequently for five drop tests with the opening facing upwards.

The results are shown in Table 1.

TABLE I ______________________________________ Sample Amount of leakage Sample Amount of leakage with plied films with plied films facing up facing down ______________________________________ A 0 g F 0 g B 0 g G 0 g C 0 g H 0 g D 0 g I 0 g E 0 g J 0 g ______________________________________

EXAMPLE 2

A bag 460 mm in width and 650 mm in length using a base film 0.20 mm in thickness, made of the same material as was used in Example 1, was continuously prepared. The film for the plied films consisted of a long leg 150 mm in length and a short leg 100 mm in length, both being 155 mm in width, while the width of the opening was 125 mm. (thickness of plied films being about 80 mm).

Low density polyethylene having a density of 0.917 g/cc and a Melt Index of 6 g/10 min. was melt-extruded at 150.degree.C from an extruder in order to adhere together the end of the bag 1 consisting of the outer surface of the long leg 3 and an inner surface of the base film, the bag being continuously prepared. Twenty-five kg of crystalline ammonium chloride for fertilizer having 2 - 3 mm particle diameter was then packed within the bag.

The effectiveness of the valve was measured by dropping the bag from a height of 2.5 m. The tests consisted of dropping the bag three times with the plied films facing the ground and subsequently dropping the bag three times with the plied films facing upwards.

The results are shown in TABLE 2.

TABLE 2 ______________________________________ Sample Amount of leakage with Sample Amount of leakage plied films facing down with plied films facing up ______________________________________ A 0 g D 0 g B 0 g E 0 g C 0 g F 2 g ______________________________________

Leakage is highest where the tube is fixed to the bottom of the bag.

EXAMPLE 3

A bag 400 mm in width and 400 mm in length, using a film 0.18 mm in thickness and made of polyethylene, was prepared by a high pressure method, the bag having a melt flow index of 0.6 and a density of 0.919 g/cc. Plied films 30 mm in width were utilized, the long leg being 70 mm in length while the short leg was 40 mm in length such legs being fixed to the side of the bag in accordance with Example 1. 4.5 k of water was inserted into the bag and three such bags were stacked and kept for 10 days. No leakage of water was found. In further test, air was inserted into the bag and a weight of 70 kg placed upon the bag. After a full day, no leakage of air was found to have occurred.

Thus, it may be seen from the above, that the synthetic film bag of the present invention has important advantages over the known prior art structures in that complete effective sealing can be obtained without actually sealing the opening of the bag by the use of conventional methods, such as, for example, heat-sealing, with its attendant drawbacks. Moreover, the structures of the valve is relatively simple, and can be easily and automatically prepared.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is to be understood therefore, that within the scope of the appended claims the present invention may be practiced otherwise than as specifically described herein .

Claims

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A bag made of a flexible base film or sheet comprising:

a valved opening having an entrance port defined by said base film or sheet and a set of plied films consisting of a long leg and a short leg;

wherein one end of said short leg is sealed upon said long leg within said valved opening, one end of said long leg is sealed to said base film at said entrance port, and the longitudinal side edges of said set of plied films are heat sealed to said base film, thereby preventing any contents of said bag from easily escaping; and

wherein further at least one slit means is provided within said long leg at a region which is not heat sealed with respect to said short leg for facilitating opening of said valve and removal of the contents from said bag, and for relieving excess pressures within said bag.

2. A bag as set forth in claim 1, wherein one end of said short leg is sealed to one end of said long leg while the opposite end of said short leg is freely movable relative to the opposite end of said long leg.

3. A bag as set forth in claim 1, wherein the length of said short leg of said set of plied films is not less than one-quarter of the length of said long leg.

4. A bag as set forth in claim 1, wherein said set of plied films is formed by two unequal lengths of flexible film or sheet and sealed to said base film or sheet along two opposite edges.

5. A bag as set forth in claim 1, wherein the inner surfaces of said valved opening are coated with non-adhesive material thereby preventing the sealing of said valved opening when the periphery of said bag is sealed.

6. A bag as set forth in claim 1, wherein a plurality of slits are provided within said long leg.

7. A bag as set forth in claim 6, wherein said slits are linearly configured.

8. A bag as set forth in claim 6, wherein said slits are V-shaped.