GB2310194A

GB2310194A - Forming a closure on a self-standing bag

Info

Publication number: GB2310194A
Application number: GB9701771A
Authority: GB
Inventors: Raizo Kuge; Yoshiji Moteki
Original assignee: Hosokawa Yoko KK
Current assignee: Hosokawa Yoko KK
Priority date: 1996-02-13
Filing date: 1997-01-29
Publication date: 1997-08-20
Anticipated expiration: 2017-01-29
Also published as: AU1260897A; IT1290923B1; FR2744699B1; JPH09216638A; ITRM970070A1; JP3587406B2; AU718756B2; FR2744699A1; GB9701771D0; GB2310194B

Description

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 as 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 above-described two points are hereinafter referred to as 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 bag body with a thin flexible film having a high strength.

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 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 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.

However, a molded container formed through the blow formation process so as to decrease the thickness of each portions 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 thickness 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 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 arises 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 are 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 at 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 liters, 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.

The present invention was made in view of the problems encountered in the prior art described above.

The first object of the present invention is 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.

The second object of the present invention is 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, thus inhibiting leakage of contents therefrom.

The third object of the present invention to provide a method for manufacturing effectively 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.

The fourth object of the present invention to provide a method for manufacturing effectively 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, thus inhibiting leakage of contents therefrom.

The fifth object of the present invention 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.

SUMMARY OF THE INVENTION In order to achieve the first object, the first bag of the present invention comprises 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, and is characterized in that: the bag body is provided with exposed inner surfaces each formed by folding a lower end portion of each of the side members along the folding line in a direction opposite to an original folding direction thereof and pulling outward the lower end portion thereof; and the rectangular bottom-forming sheet which is provided with a central folding line, is heat-sealed onto the exposed inner surfaces of the bag body so as to form a heat sealed portion along the outer peripheral edge of the bottom-forming sheet.

According to the first bag of the present invention, the bag body is provided at the lower opening end thereof with the exposed inner surfaces of the bag body, and the rectangular bottom-forming sheet which is provided with a central folding line, is heat-sealed onto the exposed inner surfaces of the bag body so as to form a heat sealed portion along the outer peripheral edge of the bottom-forming sheet so that the rectangular bottom-forming sheet can be folded along the central line thereof in the same folding direction of the side members of the bag body. There exists therefore no portion on which stress is concentrated in the bottom-forming sheet, thus imparting an excellent impact resisting property at the time of dropping of the bag and an excellent self-standing property to the bag.

In order to achieve the first object, the second bag of the present invention comprises 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, and is characterized in that:: the bottom-forming sheet is provided with exposed inner surfaces which are formed by folding the bottom-forming sheet along a central folding line thereof, folding each of both end portions of the bottom-forming sheet, which lies between each of both ends of the bottom-forming sheet and a reference point distant therefrom by a prescribed distance on the central folding line of the bottom-forming sheet, in a direction opposite to an original folding direction of the bottom-forming sheet, and further folding the each of the both end portions of the bottom-forming sheet along two lines connecting the reference point with two adjacent corners or vicinities thereof of the each of the both end portions of the bottom-forming sheet so as to form ridge lines protruded inwardly of the bag body; and the exposed inner surfaces of the bottom-forming sheet are heat-sealed onto the lower opening end of the bag body so as to form a heat sealed portion along the outer peripheral edge of the bottom-forming sheet.

According to the second bag of the present invention, the bottom-forming sheet is provided with the exposed inner surfaces, and the exposed inner surfaces of the bottom-forming sheet are heat-sealed onto the lower opening end of the bag body so as to form a heat sealed portion along the outer peripheral edge of the bottom-forming sheet.There exists therefore no portion on which stress is concentrated in the bottom-forming sheet, thus imparting an excellent impact resisting property at the time of dropping of the bag and an excellent self-standing property to the bag.

In order to achieve the second object, the third bag of the present invention comprises 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, and is characterized in that: the bag body is provided at the lower opening end thereof with a rectangular exposed inner surface which is formed by folding each of lower end portions of the 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 the folding line of the side member, in a direction opposite to an original folding direction of the side member; and the rectangular bottom-forming sheet is heat-sealed onto the rectangular exposed inner surface of the bag body so as to form a heat sealed portion along the outer peripheral edge of the bottom-forming sheet.

According to the third bag of the present invention, the bag body is provided at the lower opening end thereof with the rectangular exposed inner surface, and the rectangular bottom-forming sheet is heat-sealed onto the rectangular exposed inner surface of the bag body so as to form a heat sealed portion along the outer peripheral edge of the bottom-forming sheet. There exists therefore no portion on which stress is concentrated in the bottom-forming sheet, thus imparting an excellent impact resisting property at the time of dropping of the bag and an excellent self-standing property to the bag. In addition, since the bottom-forming sheet is not folded, there is no occurrence of pin-holes and wrinkles on the bottom-forming sheet, thus inhibiting leakage of contents therefrom.

In order to achieve the third object, the first method of the present invention for manufacturing the first bag of the present invention, i.e., 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 bottom-forming sheet for sealing a lower opening end of the bag body, is characterized by comprising the steps of:: cutting four corner portions of a lower portion of the bag body in a direction parallel to the folding line of the side member, to form cut portions each having a prescribed length; folding a lower end portion of each of the 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 the folding line of the side member, in a direction opposite to an original folding direction of the side member, and further folding the lower end portion of each of the side members along two lines connecting the reference point with inner ends of each of the 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 the 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.

According to the first method of the present invention, the exposed inner surfaces is formed at the lower opening end of the bag body, the rectangular bottom-forming sheet having a central folding line is placed on the exposed inner surfaces of the bag body, and the peripheral edge portions of the bottom-forming sheet placed on the exposed inner surfaces of the bag body are heat-sealed, thus manufacturing a self-standing bag. In such a bag, there exists therefore no portion on which stress is concentrated in the bottom-forming sheet. It is therefore possible to manufacture effectively a self-standing bag which is excellent in impact resisting property at the time of dropping of the bag and in self-standing property.

In order to achieve the third object, the second method of the present invention for manufacturing the second bag of the present invention, i.e., 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 bottom-forming sheet for sealing at least one of lower and upper opening ends of the bag body, is characterized by comprising the steps of:: forming a cylindrical bag body having lower and upper opening ends at both ends thereof, respectively, the bag body comprising 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;; folding the bottom-forming sheet along a central folding line thereof, folding each of both end portions of the bottom-forming sheet, which lies between each of both ends of the bottom-forming sheet and a reference point distant therefrom by a prescribed distance on the central folding line of the bottom-forming sheet, in a direction opposite to an original folding direction of the bottom-forming sheet, and then, folding the each of the both end portions of the bottom-forming sheet along two lines connecting the reference point with two adjacent corners or vicinities thereof of the each of the both end portions of the bottom-forming sheet so as to form ridge lines protruded inwardly of the bag body, to form exposed inner surfaces of the bottom-forming sheet; inserting the bottom-forming sheet into at least one of the lower and upper opening ends of the bag body; and heat-sealing the bottom-forming sheet onto peripheral edge portions of the at least one of the lower and upper opening ends of the bag body.

According to the second method of the present invention, there is formed the cylindrical bag body having lower and upper opening ends at both ends thereof, respectively, and having the folding line on each of the opposing side members, the exposed inner surfaces are formed in the rectangular bottom-forming sheet, the bottom-forming sheet is inserted into at least one of the lower and upper opening ends of the bag body, and the bottom-forming sheet is heat-sealed onto peripheral edge portions of the at least one of the lower and upper opening ends of the bag body, thus manufacturing a self-standing bag. In such a bag, there exists no portion on which stress is concentrated in the bottom-forming sheet. It is therefore possible to manufacture effectively a self-standing bag which is excellent in impact resisting property at the time of dropping of the bag and in self-standing property.

In order to achieve the fourth object, the third method of the present invention for manufacturing the third bag of the present invention, i.e., 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 bottom-forming sheet for sealing a lower opening end of the bag body, is characterized by comprising the steps of:: forming a cylindrical bag body having lower and upper opening ends at both ends thereof, respectively, the bag body comprising 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; folding each of lower end portions of the 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 the folding line of the side member, in a direction opposite to an original folding direction of the side member, to form a rectangular exposed inner surface of the bag body; placing the rectangular bottom-forming sheet on the expose dinner 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.

According to the third method of the present invention, the rectangular exposed inner surface is formed at the lower opening end of the bag body, peripheral edge portions of the bottom-forming sheet placed on the exposed inner surface of the bag body are heat-sealed, thus manufacturing a self-standing bag. There exists therefore no portion on which stress is concentrated in the bottom-forming sheet, thus imparting an excellent impact resisting property at the time of dropping of the bag and an excellent self-standing property to the bag. In addition, in the third method of the present invention, the bottom-forming sheet is not folded.It is therefore possible to manufacture effectively a self-standing bag which is excellent in impact resisting property at the time of dropping of the bag and in self-standing property, and can solve problems of the occurrence of pin-holes and wrinkles on the bottom-forming sheet, leading to leakage of contents therefrom.

In order to achieve the fifth object, the fourth method of the present invention for manufacturing the fourth bag of the present invention, i.e., a bag for a bag-in-box comprising a cylindrical bag body having a pair of opposing flat members and a pair of opposing side members each of which is inwardly folded in a gusset shape along a folding line, and a pair of opening-sealing sheets for sealing lower and upper opening ends, each of which is inwardly folded in a gusset shape along a folding line, is characterized by comprising the steps of:: heat-sealing four overlapped vertical portions of vertical edges of each of the pair of flat members and vertical edges of each of the pair of side members, to form a cylindrical bag body having upper and lower opening ends; folding each of a pair of opening-sealing sheets along a central folding line thereof, folding each of both end portions of each of the pair of opening-sealing sheets, which lies between each of both ends of the opening-sealing sheet and a reference point distant therefrom by a prescribed distance on said central folding line of the opening-sealing sheet, in a direction opposite to an original folding direction of the opening-sealing sheet, and then, folding said each of the both end portions of each of the pair of opening-sealing sheets along two lines connecting said reference point with two adjacent corners or vicinities thereof of said each of the both end portions of the opening-sealing sheet so as to form ridge lines protruded inwardly of the bag body, to form exposed inner surfaces of each of the pair of opening-sealing sheets; inserting the pair of opening-sealing sheets into the lower and upper opening ends of the bag body, respectively; and heat-sealing the pair of opening-sealing sheets onto peripheral edge portions of the lower and upper opening ends of the bag body, respectively.

According to the fourth method of the present invention, there is formed a cylindrical bag body having upper and lower opening ends by heat-sealing four overlapped vertical portions of vertical edges of each of the pair of flat members and vertical edges of each of the pair of side members, exposed inner surfaces are formed in each of the pair of opening-sealing sheets, the pair of opening-sealing sheets are inserted into the lower and upper opening ends of the bag body, respectively, and then the pair of opening-sealing sheets are heat-sealed onto peripheral edge portions of the lower and upper opening ends of the bag body, respectively, thus manufacturing a bag for a bag-in-box.It is therefore possible to manufacture effectively a bag for a bag-in-box, which has advantageous effects that transportation, storage and disposal of the empty bag can easily be achieved, there is required no air-blowing into the bag prior to the filling of the bag with contents, various kind of demands can easily be satisfied, barrier property can easily be ensured, and further, in case of pouring liquid contents out of the bag, it is possible to completely take out liquid contents therefrom without causing part of them to remain in the bag, and in addition, a larger strength can be imparted to a bag-in-box in cooperation with a corrugated board, to present a stable condition during piling-up and/or transporting the bag-in-boxes.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings: FIGS. 1 to 8 are schematic perspective views 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 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 to a method of the present invention in an unfolded and standing condition; 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 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.

First Embodiment According to the first embodiment of the present invention,a self-standing bag, i.e., the first bag of the present invention comprises, as shown in FIG. 9, a cylindrical bag body 10 having a pair of opposing flat members 11, Al 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 10a of the bag body 10.

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 30a along the outer peripheral edge of the bottom-forming sheet 30.

In such a bag 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 61. In this embodiment, the folding angle 61 is limited under 180 degree. The side members 21, 21 may however be unfolded completely so as to make a folding angle 61 of 180 degree.

Steps for manufacturing the above-mentioned 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 10 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 mitered-bonding method. Another bonding method described later may however be applied.

Then, four corner portions, i.e., 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 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 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 point P with inner ends D of the two adjacent cut portions 15 so as to form ridge lines 17 protruded inwardly of the bag body (refer to FIG. 4). Exposed inner surfaces gila, lia, 21a, 21a of the bag body are thus formed by carrying out the above-mentioned steps. In this embodiment, each of the reference points P1 is positioned so that a length of the line G-H as shown in FIG. 4 is equal to the folded length Li. The exposed inner surfaces lla, lia, 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 63 under 180 degree. In a certain case, the exposed inner surfaces may however be opened fully so 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 1lea, lla, 21a, 21a.

The bottom-forming sheet 30 is folded along the central folding line 31 to form a folding angle 62. The folding angle 62 of the bottom-forming sheet 30 is substantially identical with the folding angles 63 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 edges of the exposed inner surfaces gila, 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 lla, lla, 21a, 21a of the bag body 10.

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 30 with a line K connecting the opening ends H, H of the bag body 10. In the next step, the exposed inner surfaces gila, lla, 21a, 21a of the bag body 10 are folded along the above-mentioned line K together with the bottom-forming sheet 30, 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 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 manufactured bag is reversed upside down and then unfolded.

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

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. 9.

The cylindrical bag body 10 as shown in FIG. 1 may be formed, as shown in FIG. 10, by bonding overlapped vertical 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 According to the second embodiment of the present invention, a self-standing bag, i.e., the third bag of the 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 the bag body 10.

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 of the side member 21. The rectangular bottom-forming sheet 30 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 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 61. In this embodiment, the folding angle 61 is limited under 180 degree.The side members 21, 21 may however be unfolded completely so as to make a folding angle 61 of 180 degree.

First, there is prepared a cylindrical bag body 10 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 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 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 25 of the bag body 10.

A hot plate is pressed to the peripheral edge of the bottom-forming sheet 30 placed on the exposed inner surface 25 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 body 10.

The thus manufactured bag is reversed upside down and then unfolded. Such a bag which is in an unfolded and 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, 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.

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 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.

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 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 the 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 According to the third embodiment of the present invention,there is first prepared a cylindrical bag body 10 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.

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 61. 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 61 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 bottom-forming sheet 30, is folded in a direction opposite to the original folding direction of the bottom-forming sheet 30 to form a folding line 31'.Then, each of the both end portions of the bottom-forming sheet 30 is folded along two lines connecting the reference point P or P' with two adjacent 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 64 which is substantially identical with the above-described folding angle 01 of the 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 10 so that the folding lines 31, 31' of the bottom-forming sheet 30 overlap with the folding lines 23, 23 of the side members 21, 21 of the bag body lO,respectively.

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 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.

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.

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

Fourth Embodiment According to the fourth embodiment of the present invention, there is first prepared a cylindrical bag body 10 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 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 face 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 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 65. In this embodiment, the folding angle 05 is limited under 180 degree. The side members 21, 21 may however be unfolded completely so as to make a folding angle 65 of 180 degree.

Then, a pair of opening-sealing sheets 35, 35 are prepared as shown in FIG. 19. Each of the opening-sealing sheets 35, 35 is folded along a central folding line 36 thereof. Each of both end portions of the opening-sealing 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 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 35 is folded along two lines connecting the reference point P or P' with two adjacent corners or vicinities thereof of each of the both end portions of the opening-sealing sheet 35 so as to 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 10, and the exposed inner surfaces 38a and 38b, and the exposed inner surfaces 38c and 38d have the respective folding angle which is substantially identical with the above-described folding angle 66 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 35 overlap with the folding lines 23, 23 of the side members 21, 21 of the bag body 10, respectively.

Then, a hot plate is pressed to the upper and lower 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 F', 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 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.

Claims

WHAT IS CLAIMED IS:

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, characterized in that: 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 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, characterized in that:: said bottom-forming sheet is provided with exposed inner surfaces which are formed by folding the bottom-forming sheet along a central folding line thereof, folding each of both end portions of the bottom-forming sheet, which lies between each of both ends of the bottom-forming sheet and a reference point distant therefrom by a prescribed distance on said central folding line of the bottom-forming sheet, in a direction opposite to an original folding direction of the bottom-forming sheet, and further folding said each of the both end portions of the bottom-forming sheet along two lines connecting said reference point with two adjacent corners or vicinities thereof of said each of the both end portions of the bottom-forming sheet so as to form ridge lines protruded inwardly of the bag body; and said exposed inner surfaces of the bottom-forming sheet are heat-sealed onto said lower opening end of the bag body so as to forma heat sealed portion along the outer peripheral edge of the bottom-forming sheet.

3. 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, characterized in that: said bag body is provided at said lower opening end thereof with a rectangular exposed inner surface which is formed by folding each of lower end portions of the 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 said side member, in a direction opposite to an original folding direction of the side member; and said rectangular bottom-forming sheet is heat-sealed onto said rectangular exposed inner surface of said bag body so as to form a heat sealed portion along the outer peripheral edge of the bottom-forming sheet.

4. 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 bottom-forming sheet for sealing a lower opening end of the bag body, which is characterized by comprising 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, two 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 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.

5. 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 bottom-forming sheet for sealing at least one of lower and upper opening ends of the bag body, which is characterized by comprising the steps of:: forming a cylindrical bag body having lower and upper opening ends at both ends thereof, respectively, said bag body comprising 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;; folding the bottom-forming sheet along a central folding line thereof, folding each of both end portions of the bottom-forming sheet, which lies between each of both ends of the bottom-forming sheet and a reference point distant therefrom by a prescribed distance on said central folding line of the bottom-forming sheet, in a direction opposite to an original folding direction of the bottom-forming sheet, and then, folding. said each of the both end portions of the bottom-forming sheet along two lines connecting said reference point with two adjacent corners or vicinities thereof of said each of the both end portions of the bottom-forming sheet so as to form ridge lines protruded inwardly of the bag body, to form exposed inner surfaces of said bottom-forming sheet; inserting said bottom-forming sheet into at least one of said lower and upper opening ends of the bag body; and heat-sealing said bottom-forming sheet onto peripheral edge portions of said at least one of the lower and upper opening ends of the bag body.

6. 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 bottom-forming sheet for sealing a lower opening end of the bag body, which is characterized by comprising the steps of:: forming a cylindrical bag body having lower and upper opening ends at both ends thereof, respectively, said bag body comprising 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; folding each of lower end portions of the 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 said side member, in a direction opposite to an original folding direction of the side member, to form a rectangular exposed inner surface of the bag body; placing the rectangular bottom-forming sheet on said exposed inner surface of the bag body; and heat-sealing peripheral edge portions of the bottom-forming sheet placed on the exposed inner surface of the bag body.

7. A method for manufacturing a bag for a bag-in-box comprising a cylindrical bag body having a pair of opposing flat members and a pair of opposing side members each of which is inwardly folded in a gusset shape along a folding line, and a pair of opening-sealing sheets for sealing lower and upper opening ends, each of which is inwardly folded in a gusset shape along a folding line, which is characterized by comprising the steps of:: heat-sealing four overlapped vertical portions of vertical edges of each of the pair of flat members and vertical edges of each of the pair of side members, to form a cylindrical bag body having upper and lower opening ends; folding each of a pair of opening-sealing sheets along a central folding line thereof, folding each of both end portions of each of the pair of opening-sealing sheets, which lies between each of both ends of the opening-sealing sheet and a reference point distant therefrom by a prescribed distance on said central folding line of the opening-sealing sheet, in a direction opposite to an original folding direction of the opening-sealing sheet, and then, folding said each of the both end portions of each of the pair of opening-sealing sheets along two lines connecting said reference point with two adjacent corners or vicinities thereof of said each of the both end portions of the opening-sealing sheet so as to form ridge lines protruded inwardly of the bag body, to form exposed inner surfaces of each of the pair of opening-sealing sheets; inserting the pair of opening-sealing sheets into the lower and upper opening ends of the bag body, respectively; and heat-sealing the pair of opening-sealing sheets onto peripheral edge portions of the lower and upper opening ends of the bag body, respectively.

8. A bag substantially according to any of the embodiments or having the common features of those embodiments as described herein with reference to or as illustrated in the accompanying drawings.