US3009498A - Plastic bag with a self-sealing valve - Google Patents

Description

Nov. 21, 1961 M. FOHR PLASTIC BAG WITH A SELF-SEALING VALVE Filed June 11, 1957 INVENTOR. Matthias FBI/1r ATTOfLNEtLs United States Patent PLASTIC BAG WITH A SELF-SEALING VALVE Matthias Fohr, Glattbrugg, Switzerland, assignor to Werkzeugmaschinenfabrik Oerlikon Buhrle '8: C0. Abt.

Elektrodenfabrik, Zurich-Oerlikon, Switzerland, a Swiss company Filed June 11, 1957, Ser. No. 665,044 Claims priority, application Switzerland Nov. 29, 1954 4 Claims. (Cl. 150-9) This invention relates to a bag with a self-sealing valve and refers more particularly to a bag of this type which is particularly suitable for preserving liquids and dispensing them repeatedly.

The present application is a continuation-in-part of my co-pending patent application Ser. No. 549,132, filed November 25, 1955, now abandoned.

Plastic bags capable of repeatedly dispensing their contents have found ready acceptance since they have substantial advantages over bags which can be opened only once and then must be completely emptied.

In prior art the removal of a liquid from a bag having a selfsealing valve took place usually through a so-called drinking straw, namely, a small tube which had to be inserted into the bag through the valve. The total contents of the bag can be then withdrawn at several intervals and it is possible to preserve a bag which has been set in use. Furthermore, such bags can be filled and emptied many times.

It was found that bags of the type known in prior art have several drawbacks. In the first place, the construction of valves for such bags requires many additional operations, since it could not be carried out simultaneously with the manufacture of the bag. Furthermore, such bags required a substantial additional amount of plastic material for their manufacture. On the other hand, it is necessary to maintain the manufacturing costs of such bags as low as possible, since they are mass production articles which are usually thrown away by the user once the bag is empty. Therefore, low manufacturing costs are of paramount importance.

A further drawback of prior art plastic bags provided with self-sealing valves resides in that the contents can be emptied only by means of the above-described tubes or straws, so that in many instances in the absence of such a tube or straw the user was obliged to cut the bag in order to empty its contents.

An object of the present invention is the provision of a plastic bag with a self-sealing valve of such construction that the drawbacks of prior art bags are eliminated.

Other objects of the present invention will become apparent in the course of the following specification:

In accomplishing the objects of the present invention it was found desirable to provide a bag, the valve of which is formed solely by two flaps defining an opening which communicates with the interior of the bag, and which is located between two pairs of interconnected edges belonging to the side walls of the bag body. Each flap is integral with a separate side wall of the bag. The valve may be conveniently opened by pressing against the side walls of the bag body at a place located below the flaps.

The invention will appear more clearly from the following detailed description when taken in connection with the accompanying drawings showing, by way of example, preferred embodiments of the inventive idea.

In the drawings:

FIGURE 1 is a side view of a plastic bag constructed in accordance with the principles of the present invention.

FIGURE 2 is a section through a bag filled with a liquid.

FIGURE 3 is a diagrammatic front view illustrating a method of manufacturing a plurality of bags from a single piece of tubing.

FIGURE 4 illustrates a bag made in accordance with the method illustrated in FIGURE 3.

FIGURES 5 and 6 are side views showing bags of different shapes.

The bag shown in FIGURES l and 2 has a tubular bag body 1 consisting of a plastic sheet, the lower edge of which is closed by two interconnected edges 2 forming a seam. The seam may be produced by welding or any other suitable means.

The upper end of the bag body 1 is formed by two pairs of edges 6 and 7, which are also joined to form seams. Two flaps are integral with the opposite side walls of the bag body and extend outwardly from the bag body to form a neck or tube, the sides of which are joined by welding or the like to form seams 4 and 5. It is ap parent that the seams 4 and 5 extend at right angles to the seams 6 and 7 of the bag body. The flaps forming a tubular or neck like body 3 enclose the opening which leads to the interior of the bag body 1. Normally, this opening is closed, since the two flaps lie fiat one upon the other.

FIGURE 2 is a section through the bag after it is filled with a liquid. It is apparent that the bag is blown up after being filled with the liquid, so that its walls are spread apart and are subjected to tensions. The bag and the liquid filling it will have the tendency to assume its largest volume, in this case a sphere, and thus the tensions will be greatest in the plane II-II indicated in FIGURE 1. These forces P will be transmitted to the base of the neck, that is, between the ends of the seams formed by the pairs of interconnected edges 6 and '7. These edges, which can be considered as the connecting points of the flaps forming the neck 3, produce reaction forces at the lower end of the neck 3, and these reaction forces oppose the tendency of the neck 3 to open under the pressure of the liquid. The reaction forces are greater the greater is the inner pressure within the bag. Thus these reaction forces provide a complete sealing of the neck which becomes liquid-tight and gas-tight.

Practical experience has shown, however, that these reaction forces may be counteracted at a point which is designated by the letters A in FIGURES 1 and 2, to the extent that the neck 3 will not be sealed any more, and that the fluid contained in the bag may be poured out of the bag. This can be accomplished by causing the fluid within the bag to flow toward the neck 3 and, on the other hand, by pressing opposed side walls of the bag body against each other at thepoints A. This makes it possible to empty the bag without the use of any auxiliary means such as straws or tubes.

'Of course, the contents of the bag may be also removed by suction in the well-known manner.

An important feature of the use of pressure at the points A for removing the contents of the 'bag, is thatfective again, as has been described already. It is thus;

possible to withdraw the contents of a bag as desired from time to time after several intervals.

FIGURE 3 illustrates the process of manufacturing plastic bags out of an endless tube of plastic material in a continuous operation. In this construction the tubular valve 3 is cut out of the bottom portion of a preceding bag. Therefore, in this construction the seam forming the bottom of the bag consists of scam portions 2a, 2d, 2c, 2b and 2a. The seams 2d and 2b extend perpendicularly to the seams 2a, 20 and 2a. To form the top seams of the following bag, a seam 6' is provided next to the seam 2a, a seam 4 is provided next to the seam 2d, a

seam is formed next to the seam 2b and a seam 7' is formed next to the seam 2a. Only the seam portion 20 of the upper bag has no corresponding scam in the lower bag, since the valve 3 must remain open. After the seams are formed, the operator separates the upper bag from the lower bag by cutting along the line 8 which extends between the seams 2a and 6' and between the seams 2d and 4; then the cut extends below the seam 2c and between the seams 5 and 2b and 7' and 2a.

A bag of this type is shown in FIGURE 4. It has a recess 9 in the bottom corresponding to the shape of the tube 3 in the next bag.

The continuous process of making bags illustrated in FIGURE 3 has the advantage that losses in material, which would otherwise occur through the provision of the tube 3, are eliminated. Furthermore, the welding or joining operation is facilitated, since the seams 2a, 2d, 20, 2b and 2a of an upper bag may be formed simultaneously with the seams 6, 4', 5' and 7 of the lower bag. The seaming operation may be conveniently carried out with existing welding machines used for the welding of plastic materials, and such machines may be effectively combined with suitable cutting devices.

It is apparent that the provision of seams in the bag can take while the bag is full or when it is empty.

In the first instance, the endless tube filled with a fluid which is to be preserved in the bags, is subjected to the above-described welding operations.

If the bag body is welded when empty, the bag is filled after completion by introducing a tube into the neck 3 and then filling the bag through the tube with the fluid which is to be preserved in the bag.

If desired, the upper end of the tube 3 may be closed by welding or the like after the bag is filled.

FIGURE 5 shows a plastic bag 10 which is also made from a piece of hose or tube, but which has the shape of a tetrahedron. Consequently, in this construction the pairs of interconnected edges 6" and 7" extend at right angles in space to the bottom edges 2'. In other respects this bag is substantially similar to those already described.

FIGURE 6 shows a plastic bag 11 having a rectangular base 12 consisting of a plastic sheet connected with the body of the bag by seams 13. The top of the bag body is closed by two alined seams 14 and 15 located on opposite sides of the tube 3.

When the described bags are manufactured from a piece of plastic hose or tube it is advisable to subject the hose to a preliminary drawing operation in the longitudinal direction so as to stretch it, for example, by about 300%. Then the material of the hose, after the completion of the bag, will have a remaining drawing capacity of 350% as compared to 650% in the transverse direction. This will cause the molecules of the material to become oriented in the longitudinal direction of the bag.

This procedure has the advantages that, firstly, the two flaps will always lie flat one against the other, and, secondly, that a preliminary tension of the material is provided which corresponds to the extent of the three-dimensional closing forces which will be exerted later on upon the valve 3 composed of the flaps.

Practical experience has shown that to provide the greatest possible closing action of the self-closing valve 3, there are certain critical ratios that must be observed as far as the form and arrangement of the valve or neck 3 are concerned. Namely, the width of the valve or neck 3 must have a ratio to the entire width of the bag of substantially 1.5 to 10. Furthermore, the length of the neck must be at least twice its width and the neck must be located precisely in the middle of the bag. Furthermore, the neck 3 and the shoulders of the bag formed by the pairs of interconnected seams 6, 7 must extend at an angle of 90 to each other and the top can be rounded or lightly bent during the welding only to a small extent.

It should be noted that the thickness of the walls of the hose used for the manufacture of the plastic bags should not be substantially less than 0.1 millimeter, since otherwise the softness of the hose made, for example, of usual polyethylene, opposes the forces of the filling fiuid acting upon the valve. In the case of Zeiglers polyethylene, which is much harder by nature, or other harder types of polyethylene, the thickness of the walls can be reduced correspondingly to about 0.05 millimeter without affecting the forces exerted upon the valve when the bag is filled.

It is apparent that various changes may be made in the above-described examples within the scope of the present invention. For example, the bag may be made of ordinary sheets consisting of therrno-plastic material capable of being welded. Such and other variations and modifications are to be included within the scope of the present invention.

What is claimed is:

1. A bag with a self-sealing valve, said bag comprising a bag body consisting of thin pliable sheet-like thermoplastic material and having two side walls joined along their sides and their bottom, said side walls having two pairs of upper interconnected edges and an opening formed between said pairs of upper edges, said two pairs of upper edges being substantially in alinement with each other, and a neck-like body extending outwardly from said side walls and consisting of two flaps adapted to lie fiat one against the other and forming a self-sealing valve, the ratio of the width of said neck-like body to the width of said bag body being about 1.5 to 10, the length of said neck-like body being at least twice the width thereof, said neck-like body being located in the middle of said bag, each of said flaps being integral with a separate side wall, said flaps extending on opposite sides of said opening and having a top opening and interconnected parallel side edges extending relative to and intersecting said pairs of upper edges at an angle of said neck-like body constituting a continuation of the first-mentioned opening and being opened by external pressure exerted through said side walls directly below said flaps upon the contents of the bag.

2. A bag with a self-sealing valve in accordance with claim 1, wherein said side walls have two bottom interconnected edges, said bottom edges and said two pairs of upper edges extending in planes which are substantially perpendicular to each other.

3. A bag with a self-sealing valve in accordance with claim 1, wherein said side walls have two pairs of lower interconnected alined edges, two pairs of parallel lower interconnected side edges constituting a continuation of said lower alined edges and extending perpendicularly thereto, and two interconnected bottom edges constituting a continuation of said lower side edges and extending perpendicularly thereto and parallel to said lower alined edges, the width of the recess formed between the two pairs of parallel lower interconnected side edges being substantially equal to that of said flaps.

4. A bag with self-sealing valve, said bag comprising a bag body consisting of a film of polyethylene of a thickness of at least 0.05 mm. and oriented lengthwise by longitudinal stretching of about 300% of its original length, said body having two side walls joined along their sides and their bottom, said side walls having two pairs of upper interconnected edges and an opening formed between said pairs of upper edges, said two pairs of upper edges being substantially in alinement with each other, and a neck-like body extending outwardly from said side walls and consisting of two flaps adapted to lie flat one against the other and forming a selfsealing valve, the ratio of the width of said neck-like body to the width of said bag body being about 1.5 to 10, the length of said neck-like body being at least twice the width thereof, said neck-like body being located in the middle of said bag, each of said flaps being integral with a separate side wall, said flaps extending on opposite sides of said opening and having a top opening and interconnected parallel side edges extending relative to and intersecting said pairs of upper edges at an angle of 90, said neck-like body constituting a continuation of the first-mentioned opening and being opened by external pressure exerted through said side wall-s directly below said flaps upon the contents of the bag.

References Cited in the file of this patent UNITED STATES PATENTS 172,039 Lazarevitch Jan. 11, 1876 ,517,027 Rado Aug. 1, 1950 2,533,305 Wells Dec. 12, 1950 6 Metzger July 6, Toborg Dec. 7, Webb Mar. 1, Fener Aug. 2, Moore July 17, Schjeldahl Apr. 9, Dreyer et a1. July 16, Thompson Dec. 30,

FOREIGN PATENTS France Dec. 12, Canada Dec. 23, Great Britain Nov. 26,

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