WO1992002428A1

WO1992002428A1 - A self-sealing bag

Info

Publication number: WO1992002428A1
Application number: PCT/AU1991/000327
Authority: WO
Inventors: Kevin John Walker
Original assignee: Kevin John Walker
Priority date: 1990-08-01
Filing date: 1991-07-24
Publication date: 1992-02-20

Abstract

A self-sealing bag (10) is provided with a valve-type arrangement which is operative when the bag is filled to substantially prevent or restrict the egress of the contents from the bag. The valve-type arrangement comprises a flexible sheet of material (15) juxtaposed with a portion of the bag in which a slit (14) is formed. The sheet of material (15) is joined to the bag around the slit (14), but a portion of the sheet, spaced from the slit (14) is not joined to the bag to thereby provide an opening. The bag may be filled by inserting a nozzle or spout through the opening and into the slit. On removal of the filling nozzle, the contents of the bag (10) bias the side of the bag against the sheet of material (15), thereby automatically closing the bag. The bags (10) may be formed form a continuous roll of flat tubular material (20), the sheet (15) being heat-sealed to one side of the tubular material (20). To prevent sealing through to the opposite side of the material (20), a floating board is located within the tubular material (20).

Description

"A SELF-SEALING BAG"

THIS INVENTION relates to a self-sealing bag, and apparatus and method for making same. In particular, the invention is directed to an improved valve bag, as well as apparatus and method for manufacturing the valve bag.

BACKGROUND OP THE INVENTION

Throughout this specification, the term "valve bag" is intended to mean a bag, sack or similar container having an opening defined by two juxtaposed sheets of flexible material. The bag is filled typically by inserting a filling spout into the opening between the two flexible sheets. However, upon filling of the bag, internal pressure, expansion or other deformation of the bag urges the two sheets against each other to thereby seal the opening automatically in a valve-like action.

There is a known valve bag which is manufactured from a roll of continuous flat plastic sheet. The plastic sheet is folded longitudinally and the overlapping portions are sealed in a complex procedure, but not along their complete length. That is, f.: .: each bag length along the folded sheet, a portion of the overlapping sheets remains unsealed. Gussets are typically formed in the sides of the bag, and the top and bottom of the bag are sealed and cut from the continuous sheet. The unsealed portion between the overlapping edges of the sheet forms a valve-type opening through which the bag may be filled. When the bag is filled, the inner sheet is urged against the outer sheet to close the opening and seal the bag.

However, the known valve bag has several inherent disadvantages. First, the machinery required to manufacture the bag is quite complex, and hence expensive. Secondly, the machinery is normally designed to produce a bag of predetermined size, and any variation to the size of the bag requires a considerable and expensive modification to the bag forming machinery. Thirdly, due to the manner of forming the bag, the position of the valve opening is usually limited to one end of the bag adjacent the edge thereof. Although such positioning of the opening is generally convenient, in some cases it may be desired to have the valve opening at some other location on the bag.

It is an object of the present invention to overcome or substantially ameliorate the disadvantages of the known valve bag by providing an improved valve bag, as well as apparatus and method for forming the valve bag.

SUMMARY OF THE INVENTION

In one broad form, the present invention provides a substantially closed bag having an aperture in a first portion thereof, and a flexible sheet of material juxtaposed with the first portion, the sheet of material being joined to the first portion around the aperture but having a part thereof spaced from the aperture which is not joined to the first portion so as to form an opening between the sheet of material and the first portion whereby the bag may be filled through the opening and the aperture, wherein in use, the juxtaposed first portion and the sheet of material coact to substantially prevent or restrict egress of the bag's contents through the aperture and/or the opening. Typically, the aperture is a slit, and the sheet of material is located on the outside of the bag, over the slit. The bag is preferably provided with gusseted side edges, or gusseted ends. The slit may be located on a flat side of the bag, or in a gusseted end portion.

Although the bag is otherwise substantially closed, the slit or other aperture is formed at a predetermined location on the bag, this aperture being covered by the juxtaposed sheet of material. As an opening is left between the sheet of material and the bag, a nozzle or spout may be inserted through that opening and into the aperture or other slit to enable the bag to be filled. Upon removal of the filling nozzle or spout after filling, the contents within the bag urge a portion of the bag against the juxtaposed sheet of material, thereby preventing the contents from passing from the aperture to the opening between the sheet of material and the bag. Furthermore, if the aperture is a thin slit, the juxtaposition of the sheet of material with the bag will restrain the slit from opening. Thus, after filling, the bag is largely self-sealing. The valve-type opening provided on the bag is independent of the size or type of bag. Thus, the invention is applicable to bags of different sizes and shapes.

The self-sealing bag significantly reduces packaging costs as the usual steps of post-filling closure and sealing are eliminated.

In another form, the present invention provides a method of making a self-sealing bag, comprising the steps of forming an aperture in a first portion of the bag; juxtaposing a flexible sheet of material with the first portion; joining the sheet of material to the first portion around the aperture but leaving a part of the sheet, spaced from the aperture, not joined to the first portion so as to form an opening between the sheet of material and the first portion whereby the bag may be filled through the opening and the aperture, wherein in use, the juxtaposed first portion and the sheet of material coact to substantially prevent or restrict egress of the bag's contents through the aperture and/or the opening.

In yet another form, the present invention provides apparatus for forming a self-sealing bag, comprising means for forming an aperture in a first portion of the bag; means for joining a sheet of material to the first portion around the aperture but leaving a part thereof, spaced from the aperture, not joined to the first portion so as to form an opening between the sheet of material and the first portion whereby the bag may be filled through the opening and the aperture, wherein in use, the juxtaposed first portion and the sheet of material coact to substantially prevent or restrict the egress of the bag's contents through the aperture and/or the opening.

Typically, the bags are formed in a continuous process from a roll of flat tubular material. The sheet of material is joined to the first portion of the bag by any suitable method, but preferably by heat-sealing the sheet of material around three sides thereof to the bag, over the slit or other aperture.

Such a heat-sealing process normally requires the sheet of material to be clamped against the first portion of the bag momentarily while heat is applied. To prevent the opposite side of the bag being similarly sealed to the sheet of material or otherwise damaged, an intermediate planar member is located within the tubular blank of material from which the bags are formed. To permit the bags to be formed from the tubular material in a continuous process, this planar member is in the form of a "floating board" which is not connected to the machine frame, yet is constrained to remain in the same location while the tubular material passes thereover. In the illustrated embodiment, the board is provided with a pair of rollers located internally of the tubular material. A pair of external rollers are located on the outside of the tubu .. material, adjacent the internal rollers. The tubular material passes around the board and its internal rollers, but between the external rollers. Consequently, the tubular material is able to pass between the internal and external rollers while the board remains relatively stationary, with no substantial friction or other restrictive force hindering the movement of the tubular material.

In order that the invention may be more fully understood and put into practice, a preferred embodiment thereof will now be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a partially cut-away perspective view of a valve bag according to one embodiment of the invention;

Fig. 2 is a schematic perspective view of the apparatus used for forming the valve bag of Fig. 1;

Fig. 3 is a schematic partially cut-away side view of part of the apparatus of Fig. 2; and

Fig. 4 is a perspective view of a valve bag according to another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in Fig. 1, a valve bag 10, made according to a first embodiment of the invention, is of generally flat tubular form having its opposite ends 11, 12 sealed to form a substantially closed container. The valve bag 10 may be formed from a roll of continuous tubular material, or by two sheets of material joined along their longitudinal edges, or by a single sheet folded upon itself and having its free longitudinal edges joined.

Preferably, gussets 13 are formed in the longitudinal sides of the bag 10 so that the bag, when filled, will adopt a more prismatic shape, thereby facilitating stacking of the bags. The bag 10 is preferably dimensioned so that four such bags, each laid adjacent to and orthogonally to the next, will fit on a standard pallet.

A slit 14 is formed in one side of the bag 10 to provide access to the interior of the bag for filling. A second sheet 15 is located over the slit 14 and joined to the bag 10 along three sides thereof, typically by heat sealing, but any suitable joining means, such as adhesive or stitching, may be used. The fourth edge 16, spaced from the slit 14, is not joined to the bag 10, thereby providing an opening between the sheet 15 and the bag 10.

The sheet 15 and the bag 10 are typically made from flexible material, such as plastics material, woven textile fabrics, or woven plastic fibres.

To fill the bag 10, a filling nozzle or spout (not shown) is inserted between the free edge 16 of sheet

15 and the bag 10, and through the slit 14. Once the bag

10 has been filled with the desired quantity of material, the filling spout or nozzle is withdrawn. As a consequence of the volume of material within the bag 10, the expansion of the bag, the internal pressure within the bag, the natural or electrostatic attraction between sheet 15 and the underlying portion of the bag, or any combination of the foregoing, the portion of the bag 10 below sheet 15 will be biased against that sheet, thereby closing the opening of the bag and sealing same.

Due to the size of the "valve" formed by the sheet 15 and the juxtaposed portion of the bag 10, even a small pressure on the sheets will be sufficient to provide relatively secure sealing of the bag. It has been found that if the bag 10 is filled with compressed air, the seal provided by the valve-type arrangement illustrated in Fig. 1 is sufficient to maintain internal air pressure in the bag for a considerable period of time.

The bag 10 has a wide variety of uses.

Although the bag 10 is typically used for holding particulate or powdered material, it can also be used to hold liquids, gels, slushes or other semi-liquid materials.

The bag is simple and economic to manufacture, and eliminates post-f ling sealing, thereby reducing overall packaging costs.

The bag 10 may be manufactured using the apparatus illustrated schematically in Figs. 2 and 3, and the procedure for forming the bags will now be described with reference to such apparatus. The bags 10 are formed in a continuous process from a roll of flat tubular material 20. A folding mechanism 21 turns the outer edges of the flat tube inward to form gussets 13 in the finished bag 10. The mechanism 21 used to form the side gussets can be any known suitable device.

At the start-up of operation, the leading end of the roll of flat tubular material 20 is fed over a planar member such as a board 22 having a width approximately equal to the width of the finished bag 10. The leading end is fed through index rollers (not shown) which pull the material 20 from the roll over the board 22 in the direction shown. Any suitable number and arrangement of index rollers may be used. Preferably, a tensioning device is provided at the roll of material 20 to maintain an even tension on the tubular blank, and to prevent overrun of the roll.

The board 22 is located wholly within the tubular blank of material 20 from which the bags 10 are formed and cut. In this manner, the board 22 is laterally constrained within the tubular material 20.

A die 24 is provided on the upper side of board 22. The die 24 is typically a length of neoprene rubber having a longitudinal slot therein.

The board 22 is also provided with a pair of (top and bottom) transverse idler rollers 23 at its forward end (defined with respect to the direction of motion of the tubular material over the board 22).

External (top and bottom) transverse idler rollers 25 are located on either side of the flat tubular material 20 directly ahead of the internal rollers 23, as best seen in Fig. 3. (The idler rollers are not drawn to scale, but exaggerated for understanding) .

It will be apparent to those skilled in the art that as the tubular material 20 is pulled over the board

22, the board 22 will also be urged forward in the direction of motion until the leading internal idler rollers 23 reach external idler rollers 25. The tubular material 20 will then be pulled between idler rollers 23 and 25, causing directly opposed pairs of idler rollers

23, 25 to rotate in opposite senses. In this manner, the rollers 25 prevent further travel of the board 22 in the direction of motion of the tubular material, yet without applying any substantial frictional forces to the material 20 or otherwise hindering the travel of the tubular material 20. (The board 22 is relatively lightweight so that no significant weight or restrictive force is applied to the bottom sheet of the material 20).

The abovedescribed "floating board" arrangement enables the tubular blank of material 20 to be pulled over the board 22 without significant friction or other restriction, yet the board 22 will remain stationary within the tubular blank in the desired location and provide the required degree of isolation between the top and bottom sides of the flat tubular material 20.

A blade or knife 26 or other slit forming device is located directly above the die 24 on the board 22, and is controlled to move vertically so as to cut a slit in the upper side of the tubular blank 20.

A roll of sheet material 27 is arranged to be fed over the top sheet of the tubular blank 20 as shown in Fig. 2. The material 27 may be fed from its roll by any known suitable mechanism, such as coacting index rollers which feed the end of the roll into the desired position, or a reciprocating member on the opposite side with a suction pad at its end which pulls the end of the roll to the desired position. In either case, the roll of material 27 is positioned and arranged so as to be fed transversely over the top side of the tubular blank 20 in predetermined increments of length.

A sealing and cutting head 28 is located over the extended end portion of material 27, and is adapted to press the end portion of material 27 down on the top side of material 20 against the board 22. The cutting and sealing head 28 seals the end portion of material 27 along the three free edges thereof to the top side of tubular blank 20. A particularly advantageous feature of this apparatus is the use of the "floating" board 22 to prevent any sealing or damage to the bottom side of tubular blank 20. The cutting and sealing head 28 also severs a predetermined length from the end portion of material 27. Typically, the material 27 is heat sealed to the tubular blank 20, and the cutting function is provided by a heated wire, a knife, or the like. A second cutting and sealing head 29 is located on the other side of the rollers 25, and is adapted to be pressed down into contact with the tubular blank 20. A die (not shown) may suitably be located below the tubular blank 20. The cutting and sealing head 29 comprises a cutting device, such as a heated wire or a blade, interposed between two longitudinal sealing heads. When the cutting/sealing head 29 is pressed against the tubular blank 20, it cuts through the tubular blank and seals closed the open ends formed on both sides thereof. The severed portion is now a finished bag ready for stacking.

The abovedescribed apparatus is designed to produce the bags in a continuous process. At start-up, the tubular blank 20 is first unrolled and passed around board 22 and its idler rollers 23, between idler rollers 25 and between the index rollers (not shown) located after the idler rollers 25, and slightly beyond the cutting/sealing head 29. The sheet material 27 is also unrolled through index rollers and placed across the top side of tubular blank 20 below the cutting/sealing head 29. Thereafter, the delivery of the tubular material 20 and the sheet material 27 from their respective rolls, and the operation of the knife 26, and the cutting/sealing heads 28, 29 are automatically controlled, typically by microprocessor-based controlled circuitry. The knife 26 is depressed automatically against die 24 to cut a slit in the top side of the tubular blank 20. Preferably, the cutting edge of knife 26 is serrated and the tubular blank 20 is pulled forward slightly during this cutting phase so that the slit is cut, rather than pressed, into the material of the tubular blank 20. At the same time, the cutting/sealing head 28 is depressed temporarily to seal the end portion of the sheet material 27 around three sides thereof to the top side of the tubular material 20 around a previously formed slit, and to sever the sealed portion from the rest of the roll 27. Further, the cutting/sealing head 29 is depressed to cut the end of the tubular blank 20 and heat-seal the cut ends closed.

The tubular blank 20 is then driven forward automatically by index rollers by one bag length, and the leading portion of material 27 is rolled onto the upper side of tubular blank 20 beneath cutting/sealing head 28 by the predetermined length increment. The distance between the knife 26 and the cutting/sealing head 28 is so chosen that the slit previously formed by knife 26 will now be located below sealing head 28 under the (extended) end portion of material 27. The knife 26 and the cutting/sealing heads 28, 29 are again actuated to perform their cutting and sealing functions. The cutting/sealing head 29 will cut through the tubular blank 20 and seal the ends newly formed on either side thereof. Each severed portion is a newly formed valve bag 10 having closed top and bottom ends, and a slit 14 covered by a sheet of material 15 which is partially sealed around its perimeter to the bag so as to form a valve-like opening for the bag. The above process is repeated, automatically, to produce the desired quantity of bags 10. It is to be noted that the abovedescribed apparatus can be varied simply and economically to cater for bags of different sizes. For example, the bag length and hence bag capacity, can be varied without any substantial change to the apparatus or the procedure; the length through which the tubular length 20 travels during each cycle is simply altered by reprogramming the control circuitry, and the distance between the knife 26 and cutting/sealing head 28 is adjusted accordingly.

If the width of the bag is to be altered, the board 22 is removed and replaced by a board of commensurate width.

The location of the valve opening on the bag can also be varied simply by adjusting the position of the cutting/sealing h ad 28 relative to the cutting/sealing head 29.

The abovedescribed apparatus can be constructed economically, yet readily allows for variation in the size of the bag to be manufactured.

The foregoing describes only one embodiment of the invention, and modifications which are obvious to those skilled in the art may be made thereto without departing from the scope of the invention as defined in the following claims. For example, although the apparatus illustrated in Figs. 2 and 3 places the valve sheet 15 on the outside of the bag 10, the valve sheet can alternatively be placed within the bag. In this modification, two sheets, or two halves of a sheet folded longitudinally, are passed on either side of the board 22. The material 27 is inserted between one such sheet and the board, and sealed in the abovedescribed manner. Opposed longitudinal ends of the two sheets, or opposed longitudinal ends of the folded sheet, are sealed together, and the top and bottom ends of the bag are then sealed, and each bag cut from the roll. In yet another embodiment of the invention, illustrated in Fig. 4, the valve-type opening is provided at an end of the bag. The bag 30 illustrated in Fig. 4 is manufactured using apparatus similar to that illustrated in Fig. 2, the orientation of the bags 30 being orthogonal to the orientation of the bags 10. That is, the gussets are formed at the top and bottom of bag 30, rather than at the sides of the bag 10 as illustrated in Fig. 1.

During the manufacture of the bag 30, the tubular blank 20 is unrolled and the gussets are formed at opposite ends as previously described. However, one folded portion of the bifold gusset on one side is opened flat, typically by a curved guide rail, and a sheet of material 32 is joined around three sides thereof to the gusseted end over a slit 33 previously formed in the gusset portion 31 in the previously described manner. The unsealed edge 34 of the sheet material 32 provides an opening through which a nozzle may be inserted into slit 33 to fill the bag. The bag 30 therefore has its valve- like opening at the top thereof, rather than the side. The construction of the bag 30 is particularly, but not solely, suited for smaller capacity bags.

Claims

CLAIMS :

1. A substantially closed bag having an aperture in a first portion thereof, and a flexible sheet of material juxtaposed with the first portion, the sheet of material being joined to the first portion around the aperture but having a part thereof spaced from the aperture which is not joined to the first portion so as to form an opening between the sheet of material and the first portion whereby the bag may be filled through the opening and the aperture, wherein in use, the juxtaposed first portion and the sheet of material coact to substantially prevent or restrict egress of the bag's contents through the aperture and/or the opening.

2. A bag as claimed in claim 1, wherein the aperture is a slit.

3. A bag as claimed in claim 2, wherein the sheet of material is located on the outside of the bag.

4. A bag as claimed in claim 3, wherein the bag has gusseted side edges and both the first portion and the sheet of material are made of flexible plastics material, and further wherein the sheet of material is heat-sealed to the first portion.

5. A bag as claimed in claim 3, wherein the bag has gusseted ends, and the slit and the juxtaposed sheet of material are located at one gusseted end of the bag.

6. A method of making a self-sealing bag, comprising the steps of forming an aperture in a first portion of the bag; juxtaposing a flexible sheet of material with the first portion; joining the sheet of material to the first portion around the aperture but leaving a part of the sheet, spaced from the aperture, not joined to the first portion so as to form an opening between the sheet of material and the first portion whereby the bag may be filled through the opening and the aperture, wherein in use, the juxtaposed first portion and the sheet of material coact to substantially prevent or restrict egress of the bag's contents through the aperture and/or the opening.

7. A method as claimed in claim 6, wherein a plurality of the bags are made in a continuous process from a roll of flat tubular material, further comprising the step of locating a planar member within the tubular material to separate the sides thereof.

8. A method as claimed in claim 7, wherein the sheet of material is joined to the outside of the first portion by a heat-sealing device which clamps the sheet of material on the first portion against the planar member, the planar member preventing any sealing to the opposite side of the tubular material.

9. A method as claimed in claim 8, wherein the aperture is a slit formed by a blade member pressing the first portion against the planar member.

10. A method as claimed in claim 6, further comprising the step of forming gusseted sides in the bag.

11. Apparatus for forming a self-sealing bag, comprising means for forming an aperture in a first portion of the bag; means for joining a sheet of material to the first portion around the aperture but leaving a part thereof, spaced from the aperture, not joined to the first portion so as to form an opening between the sheet of material and the first portion whereby the bag may be filled through the opening and the aperture, wherein in use, the juxtaposed first portion and the sheet of material coact to substantially prevent or restrict the egress of the bag's contents through the aperture and/or the opening.

12. Apparatus as claimed in claim 11, wherein a plurality of the bags are formed in a continuous process from a roll of continuous tubular material, further comprising means for cutting predetermined lengths of material from the roll and sealing the open ends of the cut lengths.

13. Apparatus as claimed in claim 12, further comprising a planar member located within the tubular material in use, and wherein the joining means comprises a heat-sealing device for clamping the sheet of material onto the first portion against the planar member and heat-sealing the sheet of material to the flexible portion.

14. Apparatus as claimed in claim 13, further comprising a pair of internal rollers located at one end of the planar member within the tubular material, and a pair of external rollers located outside the tubular material adjacent the internal rollers, wherein the tubular material is arranged to pass externally over the planar member and the internal rollers, but between the external rollers.

15. Apparatus as claimed in claim 11, wherein the means for forming an aperture comprises a blade member for cutting a slit in the first portion of the bag.