AU718756B2

AU718756B2 - Bag and method for manufacturing same

Info

Publication number: AU718756B2
Application number: AU12608/97A
Authority: AU
Inventors: Raizo Kuge; Yoshiji Moteki
Original assignee: Hosokawa Yoko KK
Current assignee: Hosokawa Yoko KK
Priority date: 1996-02-13
Filing date: 1997-02-10
Publication date: 2000-04-20
Anticipated expiration: 2017-02-10
Also published as: JPH09216638A; GB9701771D0; FR2744699B1; GB2310194A; ITRM970070A1; IT1290923B1; JP3587406B2; FR2744699A1; AU1260897A; GB2310194B

Description

.1 I S F Ref: 366499

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name and Address of Applicant: Actual Inventor(s): Address for Service: Kabushiki Kaisha Hosokawa Yoko No. 11-5 Niban-cho Chlyoda-ku Tokyo-to

JAPAN

Raizo Kuge and Yoshljl Motekl Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Hales, 2000, Australia Bag and Method for Manufacturing Same Invention Title: The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5845 BAG AND METHOD FOR MANUFACTURING SAME BACKGROUND OF THE INVENTION The present invention relates to a self-standing bag in which a bottom portion thereof is widened so that the bag can stand itself upward, when the contents are received in the bag, and to a method for manufacturing such a bag.

As typical examples of a self-standing bag, there are provided a gusset type bag formed of a plastic film material and another bag having a bottom portion specifically worked so lOas to stand itself. In both the examples, a base plate or sheet is secured in general to the bottom portion of the bag, in order to improve the self-standing characteristics. More specifically, such a bag is composed of a bag body and a folded bottom sheet, in which the bag body and the bottom sheet are "heat-sealed together so as to form a heat sealed portion having an oblong shape. The heat sealed portion has two points, and in each of these two points, the bottom sheet and two sheets for forming the bag body are fixed together. The Sabove-described two points are hereinafter referred to as cO "fixed points".

When the bag having such fixed points is dropped down, a stress caused by the drop of the bag may be concentrated on these fixed points, and hence, the bag may be broken at these fixed points. This problem can be eliminated by forming the Kbag body with a thin flexible film having a high strength.

-1- Such a thin flexible film may degrade the self-standing property of the bag because of a low rigidity of the thin flexible film.

A bag-in-box as a disposal one-way container has widely 6 been used for the transportation and storage of various liquids such as drinks such as mineral water and industrial chemicals.

In such a bag-in-box, a foldable bag or container made of plastic material is used as an inner bag, which is then accommodated in an outer box formed of such as a corrugated board. The inner bag formed of the plastic material has a liquid tight property, anti-chemical property and gas-barrier property with respect to the liquid contents received therein.

The outer box has a rigidity required for the transportation and the storage of the bag-in-box. It is not required for the bag-in-box having such a structure .to be recovered in comparison with glass bottles or tin containers, thus i providing economical merits. In addition, since the bag-in-box has a foldable structure, the empty bag-in-box can easily be transported and stored, thus providing advantageous effects of reducing distribution costs.

A molded container formed through a blow-forming process or a flat bag with peripheral edges thereof being heat-sealed together has been used as the inner bag of the above described bag-in-box.

0 5 However, a molded container formed through the blow formation process so as to decrease the thickness of each -2portions of the molded container, has in general an insufficient strength. It is accordingly necessary to increase the thickness of each portions of the molded container. Such a molded container with the increased 6thickness therefore does not become easily broken when it is emptied and disposed, thus maintaining its bulky condition, resulting in occurrence of problems of inconvenient transportation, storage and disposal of the empty container.

Furthermore, since a mold used for this blow formation is Ic generally expensive, it is hard to satisfy various requirements for the formation in an economical manner. Still furthermore, when contents are received in the bag, it is first required to preliminarily blow air in the empty bag to properly maintain its shape, thus being also troublesome. There also I5arises a problem such that a polyethylene or polypropylene material usually used as a material of a container by means of the blow-forming process has a difficulty in maintaining its barrier property. On the other hand, with the flat bag having "..the peripheral edge heat-sealed, even when the liquid contents Tare attempted to be poured out of the inner bag, part of them liably remains in the inner bag and it is difficult to completely take out the liquid contents. In addition, as can be understood from the shape of the flat bag, when the flat bag is accommodated in the corrugated board box, there remain spaces the corner portions of the corrugated board box, and accordingly, various loads when stacking up such boxes or dropping them are applied to the corrugated board boxes, thus leading to a problem.

Furthermore, the flat bag has a disadvantage in the fact that a large amount of materials used for forming the flat bag is required, and when forming, for example, the flat bag having a capacity of 20 litres, there is required a material having a total area which is larger by about 40 percent than that of a material for forming a cubical bag having the same capacity.

It is therefore desirable to provide a self-standing bag which is excellent in impact resisting property at a time of dropping down of the bag in addition to the essential self-standing property.

It is further desirable to provide a self-standing bag which is excellent in impact resisting property and self-standing property, and wherein a bottom-forming sheet is not folded, resulting in no occurrence of pin-holes and wrinkles on the bottom-forming sheet, S: thus inhibiting leakage of contents therefrom.

It is further desirable to provide a method for manufacturing effectively a selfis standing bag which is excellent in impact resisting property at a time of dropping down of oa.: 'the bag in addition to the essential self-standing property.

~It is further desirable to provide a method for manufacturing effectively a selfstanding bag which is excellent in impact resisting property and self-standing property, and wherein a bottom-forming sheet is not folded, resulting in no occurrence of pin-holes 20 and wrinkles on the bottom-forming sheet, thus inhibiting leakage of contents therefrom.

a [R:\LIBLL]09203.doc:vjp It is further desirable to provide a method for manufacturing effectively a bag for a bag-in-box, which is excellent in impact resisting property and self-standing property, easily ensures barrier property, permits easy transportation, storage and disposal of the empty bag, and requires no air-blowing into the bag prior to the filling of the bag with contents.

It is the object of the present invention to substantially overcome or at least ameliorate one or more of the prior art disadvantages or achieve one or more of the above desires.

Summary of the Invention l0 There is disclosed herein a self-standing bag comprising a cylindrical bag body having a pair of opposing flat members for forming front and back surfaces of the bag and a pair of opposing side members each of which is inwardly folded in a gusset shape along a folding line, and a rectangular bottom-forming sheet for sealing a lower opening end of the bag body, wherein; is said bag body is provided with exposed inner surfaces each formed by folding a lower end portion of each of said side members along said folding line in a direction Sopposite to an original folding direction thereof and pulling outward said lower end portion thereof; and said rectangular bottom-forming sheet which is provided with a central folding 20 line, is heat-sealed onto said exposed inner surfaces of said bag body so as to form a heat sealed portion along the outer peripheral edge of the bottom-forming sheet.

•0Io ••ooe IL]020*o~j There is further disclosed herein a method for manufacturing a self-standing bag comprising a cylindrical bag body having a pair of opposing flat members for forming front and back surfaces of the bag body and a pair of opposing side members each of which is inwardly folded in a gusset shape along a folding line, and a rectangular bottomforming sheet for sealing a lower opening end of the bag body, the method including the steps of: cutting four corner portions of a lower portion of said bag body in a direction parallel to said folding line of the side member, to form cut portions each having a prescribed length; folding a lower end portion of each of said side members, which lies between a lower end of each of the side members and a reference point distant therefrom by a prescribed distance on said folding line of the side member, in a direction opposite to an original folding direction of the side member, and further folding said lower end portion of each of said side members along two lines connecting said reference point with inner Is ends of each of said cut portions so as to form ridge lines protruded inwardly of the bag body, to form exposed inner surfaces of the bag body; placing the rectangular bottom-forming sheet having a central folding line on said exposed inner surfaces of the bag body; and heat-sealing peripheral edge portion of the bottom-forming sheet placed on the oooo o• 20 exposed inner surfaces of the bag body.

•o •o ~Brief Description of the Drawings S Preferred forms of the present invention will now be described by way of examples only, with reference to the accompanying drawings, wherein: Figs. 1 to 8 are schematic perspective views [R:\LIBLL09203.doc:vjp illustrating sequential steps for manufacturing one embodiment of a self-standing bag as a first bag according to a method of the present invention; FIG.. 9 is a schematic perspective view illustrating the S first bag of the present invention in an unfolded and standing condition; FIG. 10 is a schematic perspective view illustrating one manufacturing mode of a bag body for constituting the first bag of the present invention; FIG. 11 is a schematic perspective view illustrating one embodiment of a self-standing bag as a third bag according So to a method of the present invention in an unfolded and standing condition; *o S" FIGS. 12 to 14 are schematic perspective views illustratings equential steps for manufacturing the third bag according to the method of the present invention; FIG. 15 is a perspective view illustrating one o i embodiment of a bottom-forming sheet for constituting a self-standing bag as a second bag of the present invention; FIGS. 16 and 17 are schematic perspective views illustrating sequential steps for manufacturing the second bag according to the method of the present invention; FIG. 18 is a schematic perspective view illustrating a step for manufacturing an embodiment of a bag for a bag-in-box according to a method of the present invention; FIG. 19 is a schematic perspective view illustrating one embodiment of an opening-sealing sheet used for manufacturing the bag for a bag-in-box according to the method of the present invention; and FIGS. 20 and 21 are schematic perspective views illustrating sequential steps for manufacturing the bag for a bag-in-box according to the method of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments according to the present invention will be described hereunder with reference to the accompanying drawings.

e: :First Embodiment According to the first embodiment of the present invention,a self-standing bag, the first bag of the !present invention comprises, as shown in FIG. 9, a cylindrical J bag body 10 having a pair of opposing flat members 11, 11 for forming front and back surfaces of the bag and a pair of a opposing side members 21, 21 each of which is inwardly folded in a gusset shape along a folding line 23, and a rectangular bottom-forming sheet 30 for sealing a lower opening end lOa of the bag body The bag body 10 is provided with exposed inner surfaces. Each of the exposed inner surfaces is formed by folding a lower end portion of each of the side members 21, 21 along the folding line 23, 23. in a direction opposite to the original folding direction thereof and pulling outward the lower end portion thereof. The rectangular bottom-forming sheet 30 is provided with a central folding line. The bottom-forming sheet 30 is heat-sealed onto the exposed inner surfaces of the bag body so as to form a heat sealed portion S along the outer peripheral edge of the bottom-forming sheet In such a bag 1, each of the side members 21, 21 of the bag body is folded along the folding line 23 so as to form a folding angle 61. In this embodiment, the folding angle 61 is limited under 180 degree. The side members 21, 21 may however be 0 unfolded completely so as to make a folding angle 01 of 180 degree.

Steps for manufacturing the above-mentioned *o self-standing bag 1 of the present invention will be described hereafter so as to more clearly explain the structure of the self-standing bag 1.

First, there is prepared a cylindrical bag body having upper and lower opening ends as shown in FIG. 1. The cylindrical bag body 10 comprises a pair of opposing flat members 11, 11 for forming the front and back surfaces of the lO bag and a pair of opposing side members 21, 21. Each of the side members 21, 21 is inwardly folded in a gusset shape along a folding line 23.

The cylindrical bag body 10 is usually made by bonding four pieces of the same material by means of a so-called 5 mitered-bonding method. Another bonding method described later may however be applied.

Then, four corner portions, connected vertical portions of the flat members 11, 11 and the side members 21, 21 of- the lower portion of the bag body 10 are cut in a direction.

parallel to the folding line of the side member 21, to form cut S portions 15, 15, 15, 15 each having the same prescribed length.

The formation of such cut portions can provide especially advantageous effects of facilitating the bag manufacturing work and of easily making the shape of the manufactured bags uniform by a cutting-out work described later.

Then, the lower end portion of each of the side members 21,21, which lies between the lower end H of each of the side members 21, 21 and a reference point P distant therefrom by a :".prescribed distance on the folding line 23 of the side member 21, is folded, as shown in FIG. 3, in a direction opposite to 1 the original folding direction of the side member 21, so as to form folding lines 23a outwardly protruded. The lower end portion of each of the side members 21, 21 is further folded along two lines 17 which connect the above-described reference

S..

point P with inner ends D of the two adjacent cut portions so as to form ridge lines 17 protruded inwardly of the bag body (refer to FIG. Exposed inner surfaces lla, lla, 21a, 21a of the bag body are thus formed by carrying out the above-mentioned steps. In this embodiment, each of the reference points Pl is positioned so that a length of the line as shown in FIG. 4 is equal to the folded length Ll. The exposed inner surfaces lla, lla, 21a, 21a are not fully opened in relation to the shape of the bottom-forming sheet 30, and as shown in FIG. 5, the exposed inner surfaces 21a, 21a have prescribed folding angles 03 under 180 degree. In a certain case, the exposed inner surfaces may however be opened fully so S that the exposed inner surfaces lla, lla lie on the same plane.

Then, as shown in FIG. 5, the rectangular bottom-forming sheet 30 having a central folding line 31 is conveyed above the exposed inner surfaces Ila, lla, 21a, 21a.

The bottom-forming sheet 30 is folded along the central folding line 31 to form a folding angle 02. The folding angle 02 of the bottom-forming sheet 30 is substantially identical with the folding angles 03 of the exposed inner surfaces 21a, 21a.

In this embodiment, the bottom-forming sheet 30 has an area which is substantially equal to an area determined by four Sedges of the exposed inner surfaces ila, lla, 21a, 21a. The bottom-forming sheet 30 may however have an area which is larger than the area determined by four edges of the exposed inner surfaces ila, lla, 21a, 21a of the bag body Then, the rectangular bottom-forming sheet 30 is placed, as shown in FIG. 6, on the exposed inner surfaces lla, lla, 21a, 21a of the bag body 10 so that the four corners of the rectangular bottom-forming sheet 30 are substantially coincided with the four edges of the exposed inner surfaces lla, lla, 21a, 21a. This working can be easily made by aligning the folding line 31 of the bottom-forming sheet with a line K connecting the opening ends H, H of the bag body 11 In the next step, the exposed inner surfaces lla, lla, 21a, 21a of the bag body 10 are folded along the above-mentioned line K together with the bottom-forming sheet as shown in FIG. 7. Thereafter, a hot plate is pressed to a portion shown by oblique lines in FIG. 7 to perform a heat seal treatment to the entire peripheral edge portion of the bottom-forming sheet 30. Then, superfluous tabs 29, 29 projecting from the both sides of the bag body 10 are cut away along the vertical edge portions of the bag body 10, and at the L same time, superfluous portions28 of the bag body 10 are also cut away along a horizontal line F. In such a manner, the self-standing bag according to this embodiment of the present invention is manufactured as shown in FIG. 8. The thus .oo.oi manufactured bag is reversed upside down and then unfolded.

fee.

i Such a bag which is in an unfolded and self-standing condition is shown in FIG. 9.

I*When contents are received in the thus manufactured ooeo self-standing bag 1, the contents are usually poured into the S. bag 1 through the upper opening end thereof. Then, the upper Sopening end of the bag 1 is heat-sealed. A pouring member may be provided to the upper end portion of the bag 1. Without heat-sealing the upper opening end of the bag 1, the bag 1 may be used as an ordinary bag having the upper opening end for receiving something as shown in FIG. 9.

The cylindrical bag body 10 as shown in FIG. 1 may be formed, as shown in FIG. 10, by bonding overlapped vertical 12 portions of vertical edges of each of a pair of flat members 51, 51 and vertical edges of each of a pair of side members 71, 71 each of which inwardly folded in a gusset shape along a folding line 73, so that the pair of flat members 51, 51 face to each other, and the pair of side members 71, 71 also face to each other. In such a case, material different from that for the side members 71 may be used for forming the flat members 51.

Second Embodiment *1 According to the second embodiment of the present invention, a self-standing bag, the third bag of the S: present invention comprises, as shown in FIG. 11, a cylindrical bag body 10 having a pair of opposing flat members 11, 11 for forming front and back surfaces of the bag and a pair of opposing side members 21, 21 each of which is inwardly folded in a gusset shape along a folding line 23, and a rectangular bottom-forming sheet 30 for sealing a lower opening end lOa of i .the bag body The bag body 10 is provided with exposed inner surfaces. Each of the exposed inner surfaces is formed by folding each of lower end portions of the side members 21, 21, which lies between the lower end of each of the side members 21, 21 and a reference point P or P' distant therefrom by a prescribed distance on the folding line 23 of the side member 21, in a direction opposite to the original folding direction R, R4 13 of the side member 21. The rectangular bottom-forming sheet is heat-sealed onto the exposed inner surfaces of the bag body so as to form a heat sealed portion 30a along the outer peripheral edge of the bottom-forming sheet 30. In such a bag r 1, 'each of the side members 21, 21 of the bag body 10 is folded along the folding line 23 so as to form a folding angle 91. In this embodiment, the folding angle 01 is limited under 180 degree. The side members 21, 21 may however be unfolded completely so as to make a folding angle 81 of 180 degree.

Steps for manufacturing the above-mentioned self-standing bag 1 of the present invention will be described

S

hereafter so as to more clearly explain the structure of the i. self-standing bag 1i.

S

First, there is prepared a cylindrical bag body having upper and lower opening ends as shown in FIG. 1. The cylindrical bag body 10 comprises a pair of opposing flat members 11, 11 for forming the front and back surfaces of the bag and a pair of opposing side members 21, 21. Each of the side members 21, 21 is inwardly folded in a gusset shap.e along Q a folding line 23. The cylindrical bag body 10 is usually made by bonding four pieces of the same material by means of a so-called mitered-bonding method. Another bonding method may however be applied.

As shown in FIG. 12, each of lower end portions of the side members 21, 21, which lies between the lower end of each of the side members 21, 21 and a reference point P or P' distant 14 therefrom by a prescribed distance on the folding line 23 of the side member 21, is folded in a direction opposite to the original folding direction of the side member 21. Then, the lower end portion of one of the flat membersll, 11 is folded back to form a rectangular exposed inner surface 25 as shown in FIG. 13.

There is prepared a rectangular bottom-forming flat sheet as shown in FIG. 13. The thus prepared bottom-forming sheet is placed on the above-mentioned exposed inner surface I 25 of the bag body A hot. plate is pressed to the peripheral edge of the s" bottom-forming sheet 30 placed on the exposed inner surface to form a heat sealed portion along the peripheral edge of the bottom-forming sheet30 as shown in FIG. 14. The thus formed heat sealed portion is shown in oblique lines in FIG. 14. In this step, a side sealing process is usually applied to the bag S .O body s #The thus manufactured bag is reversed upside down and so* .046.0 then unfolded. Such a bag which is in an unfolded and C self-standing condition is shown in FIG. 11.

When. contents are received in the thus manufactured self-standing bag 1, the contents are usually poured into the bag 1 through the upper opening end thereof. Then, the upper opening end of the bag 1 is heat-sealed. A pouring member may be provided to the upper end portion of the bag 1. Without heat-sealing the upper opening end of the bag 1, the bag 1 may be used as an ordinary bag having the upper opening end for receiving something as shown in FIG. 11. It is possible to manufacture a foldable bag for a bag-in-box by forming the exposed inner surface 25 on each of the upper and lower opening ends of the bag body 10, heat-sealing the peripheral edge portions of the rectangular bottom-forming flat sheets 30, onto the respective exposed inner surface 25, forming a pouring hole on one of the flat members 11, and providing an appropriate pouring instrument onto the pouring hole.

)O The cylindrical bag body 10 as shown in FIG. 11 may be formed, as shown in FIG. 10, by bonding overlapped vertical portions of vertical edges of each of a pair of flat members 0. 51, 51 and vertical edges of each of a pair of side members 71, 71 each of which inwardly folded in a gusset shape along a g one iSfolding line 73, so that the pair of flat members 51, 51 face i to each other, and the pair of side members 71, 71 also face to 00. each other. In such a case, material different from that for the side members 71 may be used for forming the flat members 51.

According to the self-standing bag manufactured in accordance with the method of the present invention, the rectangular exposed inner surface 25 is formed at least one of the lower and upper opening ends of the bag body 10, the peripheral edge portions of the rectangular bottom-forming sheet 30 placed on the exposed inner surface of the bag body are heat-sealed. Since the bottom-forming sheet has no folded F 16 portion, it is possible to solve problems of the occurrence of pin-holes and wrinkles on the folded portion of the bottom-forming sheet, leading to leakage of contents therefrom. In addition, the bottom-forming sheet of the bag of present invention has no portion on which stress is concentrated. The bag manufactured in accordance with the method of the present invention is excellent in impact resisting property and self-standing property.

Third Embodiment 1 o According to the third embodiment of the present invention, there is first prepared a cylindrical bag body *oo *having upper and lower opening ends as shown in FIG. 1. The cylindrical bag body 10 comprises a pair of opposing flat members 11, 11 for forming the front and back surfaces of the 'bag and a pair of opposing side members 21, 21.Each of the side members 21, 21 is inwardly folded in a gusset shape along a folding line 23.

The cylindrical bag body 10 is usually made by-bonding four pieces of the same material by means of a so-called X mitered-bonding method. Another bonding method described later may however be applied.

In such a bag body 10, each of the side members 21, 21 of the bag body 10 is folded along the folding line 23 so as to form a folding angle 01. In this embodiment, the folding angle 0/ 01 is limited under 180 degree. The side members 21, 21 may S17 however be unfolded completely so as to make a folding angle 0 1 of 180 degree.

Then, a rectangular bottom-forming sheet 30 is prepared as shown in FIG. 15. The bottom-forming sheet 30 is folded along a central folding line 31 thereof. Each of both end portions of the bottom-forming sheet 30, which lies between each of both ends of the bottom-forming sheet 30 and a reference point P or P' distant therefrom by a prescribed distance on the central folding line 31 of the 'O bottom-forming sheet 30, is folded in a direction opposite to the original folding direction of the bottom-forming sheet to form a folding line 31'. Then, each of the both end portions o of the bottom-forming sheet 30 is folded along two lines connecting the reference point P or P' with two adjacent lj5 corners or vicinities thereof of each of the both end portions of the bottom-forming sheet 30 so as to form ridge lines 32 protruded inwardly of the bag body, to form exposed inner surfaces 33a, 33b, 33c, 33d of the bottom-forming sheet 30. In this embodiment, the exposed inner surfaces 33a, 33b, 33c, 33d -^of the bottom-forming sheet 30 are not fully opened in relation to the shape of the bag body 10, and the exposed inner surfaces 33a and 33b, and the exposed inner surfaces 33c and 33d have the respective folding angle 04 which is substantially identical with the above-described folding angle 01 of the -A side members 21, 21.

Then, the bottom-forming sheet 30 is inserted into at leastone of the lower and upper opening ends of the bag body so that the folding lines 31', 31' of the bottom-forming sheet overlap with the folding lines 23, 23 of the side members 21, 21 of the bag body 4 Then, as shown in FIG. 16, a hot plate is pressed to the lower peripheral edge portions of the bag body 10 and the exposed inner surfaces 33a, 33b, 33c, 33d of the bottom-forming sheet 30 to form a heat sealed portion along the lower peripheral edge portions of the bag body 10. The thus formed \O heat sealed portion is shown in oblique lines in FIG. 17.

Superfluous portions 28 of the bottom-forming sheet 30may be cut away along a line F, if necessary.

The thus manufactured bag is reversed upside down and then unfolded. Such a bag which is in an unfolded and I5 self-standing condition is shown in FIG. 11.

When contents are received in the thus manufactured self-standing bag 1, the contents are usually poured into the Sbag 1 through the upper opening end thereof. Then, the upper opening end of the bag 1 is heat-sealed. A pouring member may be provided to the upper end portion of the bag 1. Without heat-sealing the upper opening end of the bag 1, the bag 1 may be used as an ordinary bag having the upper opening end for receiving something as shown in FIG. 11.

The cylindrical bag body 10 as shown in FIG. 11 may be a I formed, as shown in FIG. 10, by bonding overlapped vertical portions of vertical edges of each of a pair of flat members 19 51, 51 and vertical edges of each of a pair of side members 71, 71 each of which inwardly folded in a gusset shape along a folding line 73, so that the pair of flat members 51, 51 face to each other, and the pair of side members 71, 71 also face to S each other. In such a case, material different from that for the side members 71 may be used for forming the flat members 51.

The bag manufactured in accordance with the method of the present invention, in which there exists no portion on \o which stress is concentrated in the bottom-forming sheet, unlike the conventionalbag, is excellent in impact resisting property and self-standing property.

S."i Fourth Embodiment •According to the fourth embodiment of the present invention, there is first prepared a cylindrical bag body having upper and lower opening ends as shown in FIG. 18. The *cylindrical bag body 10 comprises a pair of opposing flat members 11, 11 and a pair of opposing side members 21, 21. Each of the side members 21, 21 is inwardly folded in a gusset shape C along a folding line 23. Such a sylindrical bag body 10 is prepared by bonding overlapped vertical portions of vertical edges of each of the flat members 42, 42 each having a flat face 11 and vertical edges of each of the side members 62, 62 each having a side face 21, so that the pair of flat members 42, 42 dTface to each other, and the pair of side members 62, 62 also face to each other. In this embodiment, one of the pair of flat faces 11, 11 is provided with a mouth member 50 through which a liquid is supplied in or taken out from the bag body 10. The mouth member 50 is formed by forming a hole on the one of the S flat faces 11, 11, and fitting a mouth piece made of aplastic material, for example, to the above-mentioned hole.

In such a bag body 10, each of the side members 21, 21 of the bag body 10 is folded along the folding line 23 so as to form a folding angle 05. In this embodiment, the folding angle )0 95 is limited under 180 degree. The side members 21, 21 may however be unfolded completely so as to make a folding angle 0 of 180 degree.

Then, a pair of opening-sealing sheets 35, 35 are prepared as shown in FIG. 19. Each of the opening-sealing I sheets 35, 35 is folded along a central folding line 36 thereof. Each of both end portions of the opening-sealing ii!!ii sheet 35, which lies between each of both ends of the opening-sealing sheet 35 and a reference point P or P' distant therefrom by a prescribed distance on the central folding line X 36 of the opening-sealing sheet 35, is folded in a direction opposite to the original folding direction of the opening-sealing sheet 35 to form a folding line 36'. Then, each of the both end portions of the opening-sealing sheet is folded along two lines connecting the reference point P or :4 P' with two adjacent corners or vicinities thereof of each of the both end portions of the opening-sealing sheet 35 so as to 21 form ridge lines 37 protruded inwardly of the bag body, to form exposed inner surfaces 38a, 38b, 38c, 38d of the opening-sealing sheet 35. In this embodiment, the exposed inner surfaces 38a, 38b, 38c, 38d of the opening-sealing sheet 35 are not fully opened in relation to the shape of the bag body and the exposed inner surfaces 38a and 38b, and the exposed inner surfaces 38c and 38d have the respective folding angle 0 6 which is substantially identical with the above-described folding angle 06 of the side members 21, 21.

Then, as shown in FIG. 20, the pair of opening-sealing sheets 35 thus prepared are inserted respectively into the lower and upper opening ends of the bag body 10 so that the folding lines 36', 36' of each of the opening-sealing sheets overlap with the folding lines 23, 23 of the side members 21, 1 21 of the bag body 10, respectively.

Then, a hot plate is pressed to the upper and lower o peripheral edge portions of the bag body 10 and the exposed inner surfaces 38a, 38b, 38c, 38d of each of the opening-sealing sheets 35, 35 to form heat sealed portions along the upper and lower peripheral edge portions of the bag body 10, respectively. The thus formed heat sealed portions are shown in oblique lines in FIG. 21. Superfluous portions 39 of the opening-sealing sheets 35 may be cut away along a line if necessary.

The thus manufactured bag for a bag-in-box is adapted to be accommodated in a corrugated board box to form a bag-in-box. When filling the bag with contents such as mineral water, the mineral water is poured into the bag through the mouth member 50 formed on the flat face 11.

The bag for a bag-in-box, manufactured in accordance with the method of the present invention can be folded in a small size, thus permitting effective transportation, storage and disposal of the bags in an empty condition. In addition, the bag has a rectangular shape in an outward appearance, so that when it is accommodated in a rectangular corrugated board lo box, there exists substantially no space at inner corner portions of the box, thus improving its strength in stacking them and its impact resisting property in comparison with the corrugated board box itself. Furthermore, due to this rectangular shape, it is not necessary to preliminarily blow air into the bag prior to the filling of the bag with contents, and an improved barrier property is also easily attainable by laminating each of the pair of flat members and each of the pair of side members with a barrier layer.

S*

Claims

1. A self-standing bag comprising a cylindrical bag body having a pair of opposing flat members for forming front and back surfaces of the bag and a pair of opposing side members each of which is inwardly folded in a gusset shape along a folding line, and a rectangular bottom-forming sheet for sealing a lower opening end of the bag body, wherein; said bag body is provided with exposed inner surfaces each formed by folding a lower end portion of each of said side members along said folding line in a direction opposite to an original folding direction thereof and pulling outward said lower end portion thereof; and said rectangular bottom-forming sheet which is provided with a central folding line, is heat-sealed onto said exposed inner surfaces of said bag body so as to form a heat sealed portion along the outer peripheral edge of the bottom-forming sheet.

2. A method for manufacturing a self-standing bag comprising a cylindrical bag body having a pair of opposing flat members for forming front and back S- surfaces of the bag body and a pair of opposing side members each of which is inwardly folded in a gusset shape along a folding line, and a rectangular bottom-forming sheet for sealing a lower opening end of the bag body, the method including the steps of: cutting four corner portions of a lower portion of said bag body in a direction 20 parallel to said folding line of the side member, to form cut portions each having a prescribed length; ?folding a lower end portion of each of said side members, which lies between a lower end of each of the side members and a reference point distant therefrom by a prescribed distance on said folding line of the side member, in a direction opposite to an 25 original folding direction of the side member, and further folding said lower end portion of each of said side members along two lines connecting said reference point with inner ends of each of said cut portions so as to form ridge lines protruded inwardly of the bag body, to form exposed inner surfaces of the bag body; placing the rectangular bottom-forming sheet having a central folding line on said exposed inner surfaces of the bag body; and heat-sealing peripheral edge portions of the bottom-forming sheet placed on the exposed inner surfaces of the bag body.

3. A self standing bag, substantially as herein described, with referenceto Figs. 1 tolO; Figs. 11 to 14; Figs. 15 to 17; or Figs. 18 to 21 of the accompanying Sdrawings. [R:\LIBLL092 IOdoc:vj p

4. A method for manufacturing a self-standing bag, the method substantially as hereinbefore described with reference to Figs. 1 to 10; Figs. 11 to 14; Figs. 15 to 17; or Figs. 18 to 21 of the accompanying drawings. Dated 14 February, 2000 Kabushiki Kaisha Hosokawa Yoko Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON [R:\LIBLL]O9203.doc:vjp