Patent Publication Number: US-2023150757-A1

Title: Drip bag

Description:
TECHNICAL FIELD 
     The present invention relates to a drip bag that can be easily used to obtain an extraction liquid such as coffee, black tea, green tea, and herbal medicine by hooking the drip bag onto the top of a container such as a cup. 
     BACKGROUND ART 
     Conventionally, as drip bags that enable easy enjoyment of drip coffee, drip bags that are provided with hooking portions made of thin plate-like materials on two opposite surfaces of a bag main body made of a water permeable filter sheet, to enable the drip bag to be hooked onto an opening wall of a cup by opening a top end portion of the bag main body and pulling the hooking portions in opposite directions to each other, are widely used (Patent Literature 1). In these drip bags, one arm portion that can be pulled up from the bag main body is connected to the hooking portions. 
     For such drip bags, it has been proposed to form specific folding lines in the thin plate-like materials provided along an opening portion of the bag main body, and to provide two arm portions that are to be pulled up from the bag main body, such that the opening portion of the bag main body opens wider (Patent Literatures 2 and 3). 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Patent No. 4079041 
     Patent Literature 2: Japanese Patent No. 5892262 
     Patent Literature 3: Japanese Patent No. 5858172 
     SUMMARY OF INVENTION 
     Technical Problem 
     In the conventional drip bags described above, the opening portion of the bag main body opens wide when the drip bag is hooked onto a cup with a large opening diameter. However, when the drip bag is hooked onto a cup with a small opening diameter, the opening portion of the bag main body opens small, so that it becomes difficult to pour hot water into the opening portion. More specifically, for example, when a drip bag  1   x  described in Patent Literature 2, as illustrated in  FIG.  20 A , is hooked onto a cup  100 A with a large opening diameter by pulling hooking portions  23  on the front and back of a bag main body  10  in opposite directions to each other, as illustrated in  FIGS.  20 B and  20 C , the center of the bag main body  10  is pulled to the side closer to an opening wall of the cap  100 A at central portions  21  with which lower ends of arm portions  22  pulled up from the bag main body  10  are continuous, so that the opening portion of the bag main body  10  opens wide. However, when the drip bag  1   x  is hooked onto a cup  100 B with a small opening diameter, as illustrated in  FIGS.  21 A and  21 B , the opening portion of the bag main body  10  opens small even though the arm portions  22  are pulled up from the bag main body  10 . 
     The present invention aims at providing a drip bag having hooking portions on two opposite surfaces of a bag main body to be pulled in opposite directions to each other and hooked onto an opening wall of a cup or another container, in which an opening portion of the bag main body is capable of opening wider than before, even when an opening diameter of the cup or the like is small. 
     Solution to Problem 
     The present inventor has found that the reason why, when a conventional drip bag is hooked onto a cup with a small opening diameter, an opening portion of a bag main body opens small even though arm portions are pulled up from the bag main body is because lower ends of the arm portions are easily bent against the bag main body and the bag main body is not easily pulled by the lower portions of the arm portions. To address this, the present inventors have discovered that it is effective to shift the positions of the lower ends of left and right sides of the arm portions in a vertical direction of the bag main body such that the lower ends of the arm portions do not bend easily when the arm portions are pulled up. As a result, the present inventors have conceived of the present invention. 
     Specifically, the present invention provides a drip bag including: 
     a bag main body formed of a water permeable filter sheet; and 
     hooking members made of a thin plate-like material provided on two opposite outer surfaces of the bag main body, wherein 
     each of the hooking members provided on the two surfaces includes:
         an upper bonded portion provided along an upper side of the bag main body;   a central portion provided in the center of the hooking member, the central portion being unable to be pulled up from the bag main body;   a pair of arm portions provided from the central portion to a direction toward the upper bonded portion, the pair of arm portions being spaced apart from each other with a center line of a width of the bag main body located between them; and   a pair of hooking portions continuous with upper parts of the arm portions, the pair of hooking portions each extending between a side of the bag main body and the arm portion downward in the bag main body, the pair of hooking portions being not bonded onto the bag main body, and       

     each of the arm portions is capable of being pulled up from the bag main body at an upper part thereof, each of the arm portions has a fixed side fixed onto the bag main body at a lower part thereof, and the fixed side is inclined with respect to a width direction of the bag main body or extends downward vertically with respect to the width direction of the bag main body from a lower end of a side, closer to the side of the bag main body, out of left and right sides of each of the arm portions. 
     The fixed side of the arm portion does not mean a side that forms the outline of the arm portion, but a virtual side that is a straight line connecting lower end portions of both the two sides of the arm portion. This fixed side is fixed onto the bag main body and cannot be pulled up from the bag main body. The fixed side fixed onto the bag main body does not necessarily mean that the fixed side is bonded to the bag main body. The fixed side fixed onto the bag main body means to include a case in which the fixed side is floating from the surface of the bag main body, as long as the position of the fixed side on the bag main body is constant by bonding surroundings of the fixed side. 
     Advantageous Effects of Invention 
     According to the drip bag of the present invention, the fixed side at the lower part of the arm portion is inclined with respect to the width direction of the bag main body, or extends downward vertically with respect to the width direction of the bag main body from the lower end of, out of the sides of the arm portion, the side closer to the side of the bag main body. Thus, when the hooking portions on the two opposite surfaces of the bag main body are pulled up from the bag main body and pulled in opposite directions to each other, the lower parts of the arm portions are twisted and become difficult to bend. Thus, a tensile force not only bends the lower ends of the arm portions to move the upper ends of the arm portions in a pulling direction, but also moves the bag main body in the pulling direction at portions where the lower ends of the arm portions are fixed. As a result, the arm portions are pulled up from the bag main body while the lower ends of the arm portions pull the bag main body. Therefore, even when an opening diameter of a cup is small and the length of pulling the hooking portions in the opposite directions is short, an opening portion of the bag main body can be opened wider than before, thus facilitating pouring hot water into the drip bag. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a plan view of a drip bag  1 A according to an embodiment. 
         FIG.  2    is a perspective view of the drip bag  1 A according to the embodiment after being opened, in a state of starting pulling up hooking portions. 
         FIG.  3    is a perspective view of the drip bag  1 A according to the embodiment after being opened, in a state of being hooked onto a cup. 
         FIG.  4    is a perspective view of the drip bag  1 A according to the embodiment after being opened, in a state of being hooked onto the cup with hooking portions folded. 
         FIG.  5 A  is a side view of the drip bag  1 A according to the embodiment after being opened, in a state of being hooked onto a cup with a large opening diameter. 
         FIG.  5 B  is a top view of the drip bag  1 A according to the embodiment after being opened, in a state of being hooked onto the cup with the large opening diameter. 
         FIG.  6 A  is a side view of the drip bag  1 A according to the embodiment after being opened, in a state of being hooked onto a cup with a small opening diameter. 
         FIG.  6 B  is a top view of the drip bag  1 A according to the embodiment after being opened, in a state of being hooked onto the cup with the small opening diameter. 
         FIG.  7    is a plan view of a drip bag  1 B according to an embodiment. 
         FIG.  8    is a plan view of a drip bag  1 C according to an embodiment. 
         FIG.  9    is a plan view of a drip bag  1 D according to an embodiment. 
         FIG.  10    is a plan view of a drip bag  1 E according to an embodiment. 
         FIG.  11    is a plan view of a drip bag  1   y  according to a comparative example. 
         FIG.  12    is a plan view of a drip bag  1 F according to an embodiment. 
         FIG.  13    is a plan view of a drip bag  1 G according to an embodiment. 
         FIG.  14    is a plan view of a drip bag  1 H according to an embodiment. 
         FIG.  15    is a plan view of a drip bag  1 I according to an embodiment. 
         FIG.  16 A  is a plan view of a drip bag  1 J according to an embodiment. 
         FIG.  16 B  is a plan view of a drip bag  1 K according to an embodiment. 
         FIG.  17    is a plan view of a drip bag  1 L according to an embodiment. 
         FIG.  18    is a plan view of a production sheet for the drip bag  1 A according to the embodiment. 
         FIG.  19    is an explanatory view of a producing method of drip bags. 
         FIG.  20 A  is a plan view of a conventional drip bag  1   x.    
         FIG.  20 B  is a side view of the conventional drip bag  1   x  being hooked onto a cup with a large opening diameter. 
         FIG.  20 C  is a top view of the conventional drip bag  1   x  being hooked onto the cup with the large opening diameter. 
         FIG.  21 A  is a side view of the conventional drip bag  1   x  being hooked onto a cup with a small opening diameter. 
         FIG.  21 B  is a top view of the conventional drip bag  1   x  being hooked onto the cup with the small opening diameter. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The present invention will be described in detail below with reference to the drawings. In each drawing, the same reference numerals indicate identical or equivalent components. 
     Overall Configuration of Drip Bag 
       FIG.  1    is a plan view of a drip bag  1 A according to an embodiment of the present invention in an unopened state.  FIG.  2    is a perspective view of the drip bag  1 A after being opened, in a state of starting pulling up hooking portions  23 .  FIG.  3    is a perspective view of the drip bag  1 A in a state of being hooked onto a cup  100 .  FIG.  4    is a perspective view of the drip bag  1 A hooked onto the cup, with the hooking portions  23  of the drip bag  1 A folded. In  FIG.  1   , diagonally hatched portions represent bonded regions in which a hooking member  20  is bonded to a bag main body  10 . The bonded regions are not limited to the illustrated mode. Due to the opacity of the hooking member  20 , the bonded regions cannot usually be visually observed from an outer surface of the bag main body  10 . 
     The drip bag  1 A has the bag main body  10  formed of a water permeable filter sheet, and the hooking members  20  made of a thin plate-like material provided on two opposite outer surfaces of the bag main body  10 . The bag main body  10  is filled with an extraction material, and an opening portion  11  of the bag main body  10  is closed. 
     Each of the hooking members  20  on the front and back of the bag main body  10  has an upper bonded portion  24  provided along an upper side of the bag main body  10 , a central portion  21  provided in the center of the hooking member  20  so as not to be pulled up from the bag main body  10 , a pair of arm portions  22  that extend from the central portion  21  to a direction of the upper bonded portion  24  and that are spaced apart from each other with a center line A of the width of the bag main body  10  located between them, and a pair of hooking portions  23  each of which is continuous with an upper part of the arm portion  22  and extends between a side  10   b  of the bag main body and the arm portion  22  downward in the bag main body  10 . The hooking portions  23  are not bonded to the bag main body  10 . The pair of arm portions  22  can be pulled up from the bag main body  10  at upper parts thereof. The pair of arm portions  22  each have a fixed side  22   a,  which is fixed onto the bag main body  10  at a lower part thereof. The fixed side  22   a  is inclined with respect to a width direction of the bag main body. 
     In the drip bag  1 A of the present embodiment, the hooking members  20  are independently provided on two opposite surfaces of the bag main body  10  and the hooking members  20  are symmetrically formed, but in the present invention, the hooking members  20  on the two opposite surfaces of the bag main body  10  may be continuous with each other. 
     Bag Main Body 
     The bag main body  10  is formed of a water permeable filter sheet, and filled with coffee powder as an extraction material. 
     As the water permeable filter sheet forming the bag main body  10 , for example, various types of sheet that are capable of leaching coffee when a predetermined amount of coffee powder is filled and hot water is poured can be used. Generally, as the sheet for leaching, for example, a woven or non-woven fabric made of synthetic fibers such as polyester, nylon, polyethylene, polypropylene, and vinylon, semi-synthetic fibers such as rayon, and natural fibers such as broussonetia and edgeworthia chrysantha individually and in composites, paper including mixed paper made of Manila hemp, wood pulp, polypropylene fibers, and the like, tea bag base paper, metal mesh sheet; and the like are known, and these can be used in the present invention. However, from a viewpoint of disposability after use of the drip bag, biodegradable fibers are preferably contained in the water permeable filter sheet material. Examples of the biodegradable fiber include polylactic acid, polybutylene succinate, and polyethylene succinate. In order to provide a moderate steaming effect to the coffee powder when dripping, when producing the water permeable filter sheet from these fiber materials, the porosity of fiber layers is preferably adjusted so as to create a sparse-dense multi-layer structure in which a layer in direct contact with the coffee powder is made “sparse” and a layer not in direct contact with the coffee powder is made “dense”. It is preferable to increase the content of hydrophobic fibers in the layer that is in direct contact with the coffee powder, and to decrease the content of hydrophobic fibers in the layer that is not in direct contact with the coffee powder (Japanese Patent No. 3674486). 
     In the present embodiment, the bag main body  10  is a rectangular flat bag in plan view with an upper side  10   a  and left and right sides  10   b  sealed, and has two opposite surfaces. In the vicinity of the upper side  10   a  of the bag main body  10 , an opening guide line  12  is formed along the upper side  10   a.  As the opening guide line  12 , perforations or the like can be formed. As the perforations, micro-perforations are preferred from the viewpoint of facilitating opening. Instead of the perforations for opening, a seal at the upper side  10   a  of the bag main body may be a weak seal. That is, the seal strength of the upper side  10   a  is made weaker than seal strengths of the other sides of the bag main body  10  so that the upper side  10   a  of the bag main body  10  may easily open by pulling the hooking portions  23  provided on the two opposite surfaces of the bag main body  10  in opposite directions to each other, although the seal does not peel off unintendedly except in opening operation. In the present invention, a bottom portion and side portions of the bag main body  10  may be gusseted as necessary. 
     The net planar dimension of the bag main body  10  can be appropriately set according to the size of a cup or container onto which the drip bag is to be hooked. For example, the net planar dimension should be large enough to be used with commercially available coffee cups. 
     Hooking Member 
     The hooking member  20  can be formed by, for example, punching out the thin plate-like material such as paperboard, plastic sheet, thin metal sheet, or the like. The thin plate-like material is also preferably formed of a biodegradable material such as polylactic acid, polybutylene succinate, or polyethylene succinate, from the viewpoint of disposability after use of the drip bag  1 A. 
     The hooking member  20  has the upper bonded portion  24  provided along the upper side  10   a  of the bag main body  10 . The upper bonded portion  24  is bonded to the bag main body  10 , but the bonded region need not be the entire surface of the upper bonded portion  24 . For example, as illustrated in  FIG.  1   , line-shaped bonded regions can be provided intermittently. 
     In the present invention, the upper bonded portion  24  may be formed as a band shape with a constant width, but as illustrated in  FIG.  1   , the upper bonded portion  24  preferably includes a protruding portion  25  in which a central portion thereof in the width direction of the bag main body  10  protrudes downward, and a pair of oblique folding lines L 1  provided with the center line A of the width of the bag main body  10  located between them. The oblique folding lines L 1  each preferably are a line extending in a direction away from the center line A from a lower part of the protruding portion  25  to an upper side of the upper bonded portion  24 , without touching an edge side  25   a  of the protruding portion  25 . This allows bending of the upper bonded portion  24  at the oblique folding lines L 1  by pulling the hooking portions  23  provided on the two opposite surfaces of the bag main body  10  in opposite directions to each other, so that an opening shape of the bag main body  10  becomes polygonal of octagonal or more, and an opening area can be expanded. 
     In the present embodiment, there is no folding line formed on the upper bonded portion  24  of the drip bag  1 A, other than the oblique folding lines L 1 . This enables an opening portion of the bag main body to be opened wider and the opening shape to be closer to a circle than when vertical folding lines of the bag main body are formed just below the oblique folding lines L 1 . 
     The oblique folding lines L 1  can be formed by perforations, half-cutting, streak pressing, or the like. The oblique folding lines L 1  can also be formed by cut lines through the front and back of the hooking member  20  so that the upper bonded portion  24  is easily folded at the oblique folding lines L 1 , as long as underlying water permeable filter sheet of the bag main body  10  is continuous. 
     From left and right ends of the upper bonded portion  24 , reinforcing portions  26  extend along the sides  10   b  of the bag main body  10  toward the bottom side of the bag main body. In the present invention, the reinforcing portions  26  are provided as necessary. 
     In the present invention, the central portion  21  is a portion that is provided at the center of the hooking member  20  and cannot be pulled up from the bag main body  10 . The central portion  21  is preferably provided on the center line of the width of the hooking member  20 , but is not limited thereto. In order to make the central portion  21  unable to be pulled up from the bag main body, a bonded region, which is bonded to the bag main body  10 , may be formed in the central portion  21 , as with the drip bag  1 A of the present embodiment, or regions connected to the top and bottom of the central portion  21  may be bonded to the bag main body  10  while the central portion  21  itself may not be bonded to the bag main body  10 . 
     From the left and right sides of the central portion  21 , the pair of arm portions  22  are provided to the direction of the upper bonded portion  24  with the center line A located between them. The arm portions  22  are separated by a central bonded portion  27  extending upward from the central portion  21 . 
     Each of the arm portions  22  can be pulled up from the bag main body  10 . An upper part of each of the arm portions  22  is continuous with the hooking portion  23 . In a lower part of each of the arm portions  22 , the fixed side  22   a  fixed onto the bag main body  10  is formed. 
     The reason why the pair of arm portions  22  are provided with the center line A located between them is, as described below, to make the fixed sides  22   a  at the lower parts of the arm portions  22  inclined with respect to the width direction of the bag main body. In contrast, if the central bonded portion  27  is omitted and a single arm portion is provided as described in FIG. 1 of Patent Literature 1 by connecting the arm portions on the left and right of the center line A, it becomes difficult to provide inclined fixed sides at a bottom part of the arm portion. 
     In the drip bag  1 A according to the present embodiment, the fixed sides  22   a  are inclined with respect to the width direction of the bag main body. To make the fixed sides  22   a  inclined like this with respect to the width direction of the bag main body, in the drip bag  1 A, one of both left and right sides of each arm portion  22 , a side  22   c  closer to the side  10   b  of the bag main body is curved into an arc shape at an adjoining portion to the fixed side  22   a  relative to the position of a lower end of a side  22   b  closer to the center line A, thereby shifting the position of the lower end of the side  22   c  to the side closer to the bottom side  10   c  of the bag main body. 
     Due to this inclination of the fixed sides  22   a,  when the hooking portions  23  provided on the two opposite surfaces of the bag main body  10  are pulled in opposite directions to each other, a tensile force more strongly acts on, out of both left and right end portions of the fixed side  22   a  of the arm portion  22 , the end portion closer to the center line A than the end portion closer to the side  10   b  of the bag main body. The arm portion  22  is twisted and the lower part of the arm portion  22  becomes difficult to bend. Therefore, the tensile force not only bends the lower end of the arm portion  22  to move an upper end of the arm portion  22  in a pulling direction by a movement amount Δx 1 , but also moves the bag main body  10  at a portion fixed to the lower end of the arm portion  22  in the pulling direction by a movement amount Δx 2 . Therefore, the arm portions  22  are pulled up from the bag main body  10  while pulling the bag main body  10 . Not only in a case in which, as illustrated in  FIGS.  5 A and  5 B , the hooking portions  23  are hooked onto an opening wall of a cup  100 A with a large opening diameter, but also in a case in which, as illustrated in  FIGS.  6 A and  6 B , the hooking portions  23  are hooked onto an opening wall of a cup  100 B with a small opening diameter, the arm portions  22  curve in the shape of the letter S in side view ( FIGS.  5 A and  6 A ). As a result, the two opposite surfaces of the bag main body  10  are pulled in the opposite directions to each other by the lower parts of the arm portions  22 , thus resulting in wide opening of the opening portion of the bag main body  10 . This advantageous effect is remarkable with the use of the cup  100 B with the small opening diameter compared with the conventional drip bag ( FIGS.  21 A and  21 B ). Thus, according to this drip bag  1 A, the opening portion  11  of the bag main body  10  can be opened wide, regardless of the cup opening diameter, thus facilitating pouring hot water into the drip bag  1 A. 
     When the fixed side  22   a  of the arm portion  22  is inclined with respect to the width direction of the bag main body, the inclination angle αα( FIG.  1   ) is preferably 30° or more from the viewpoint of obtaining the advantageous effect of the present invention. 
     The pair of arm portions  22  provided with the center line A located between them are connected to each other at upper parts thereof by an upper connecting portion  28 . The provision of the upper connecting portion  28  prevents the pair of hooking portions  23  from coming apart when the pair of hooking portions  23 , which are continuous with the upper parts of the pair of arm portions  22 , are hooked onto the opening wall of the cup or the like, thereby facilitating hooking the hooking portions  23  onto the opening wall of the cup or the like. 
     In the present invention, the hooking portions  23  are continuous with the upper parts of each of the arm portions  22  provided on the left and right of the center line A. In the drip bag  1 A according to present embodiment, the hooking portion  23  is continuous with the upper part of the arm portion  22  at one end of the upper part of the hooking portion  23 , has a portion  23   a  extending in the width direction of the bag main body at a middle of the upper part of the hooking portion  23 , and extends between the arm portion  22  and the reinforcing portion  26  downward in the bag main body  10  at the other end of the hooking portion  23 . The provision of the portions  23   a  extending in the width direction of the bag main body at the upper parts of the hooking portions  23 , as illustrated in  FIGS.  3  and  4   , stabilizes hooking of the hooking portions  23  onto the opening wall of the cup  100 . In addition, vertical folding lines L 2  are formed in the upper parts of the hooking portions  23 , and vertical folding lines L 3  are formed in lower parts of the hooking portions  23  on an extended line of the vertical folding lines L 2  in the upper parts. This facilitates folding the hooking portions  23  as illustrated in  FIG.  4   . These folding lines L 2  and L 3  can also be formed by perforations, half-cutting, streak pressing, or the like. 
     The pair of hooking portions  23  located on the left and right of the center line A are connected at lower parts thereof by a lower connecting portion  29 . This facilitates operation of hooking the pair of hooking portions  23  onto the opening wall of the cup or the like. 
     Second central bonded portions  30  are each formed between the arm portion  22  and the hooking portion  23 . With this configuration, end portions of the arm portions  22  on the side closer to the fixed sides  22   a  can each be enclosed by the central portion  21 , the central bonded portion  27 , and the second central bonded portion  30 . In particular, providing bonded regions to the bag main body in these portions that surround the end portions of the arm portions  22  on the side closer to the fixed sides  22   a  is preferred because the stability of the arm portions  22  is improved in the direction of pulling up the arm portions  22 . 
     Variations of Drip Bag 
     The drip bag of the present invention can take various forms. For example, in comparison to the drip bag  1 A illustrated in  FIG.  1   , a drip bag  1 B illustrated in  FIG.  7    is prepared by curving the side  22   b,  one of both sides of each arm portion  22 , closer to the center line A at the adjoining portion to the fixed side  22   a  into an arc shape and shifting the position of the lower end of the side  22   b  to the side closer to the bottom side  10   c  of the bag main body than the position of the lower end of the side  22   c  closer to the side  10   b  of the bag main body to incline the fixed side  22   a  of the arm portion  22 . Also, in this drip bag  1 B, by pulling the hooking portions  23  provided on the two opposite surfaces of the bag main body  10  in the opposite directions to each other, the lower parts of the arm portions  22  are twisted, thus making it difficult to form folding lines in the width direction of the bag main body at the lower parts of the arm portions  22 . As a result, even in a case in which the drip bag  1 B is hooked onto a cup with a small opening diameter, the opening portion  11  of the bag main body opens wide, which facilitates pouring hot water. 
     In comparison to the drip bag  1 A illustrated in  FIG.  1   , a drip bag  1 C illustrated in  FIG.  8    is prepared by making one side  22   c  of each arm portion  22  straight without curving the side  22   c  in an arc shape at the adjoining portion to the fixed side  22   a  and shifting the position of the lower end thereof to the side closer to the bottom side of the bag main body than the position of the lower end of the other side  22   b  to incline the fixed side  22   a.  Also, in comparison to the drip bag  1 A illustrated in  FIG.  1   , a drip bag  1 D illustrated in  FIG.  9    is prepared by making one side  22   b  of each arm portion  22  straight without curving the side  22   b  in an arc shape at the adjoining portion to the fixed side  22   a  and shifting the position of the lower end thereof to the side closer to the bottom side of the bag main body than the position of the lower end of the other side  22   c  to incline the fixed side  22   a.  In these manners, the shape of the lower part of the arm portion  22  adjoining to the fixed side  22   a  may be straight or curved. 
     In a drip bag  1 E illustrated in  FIG.  10   , in contrast to the above-described drip bags  1 A,  1 B,  1 C, and  1 D, the fixed side  22   a  is not inclined with respect to the width direction of the bag main body, and the fixed side  22   a  extends downward vertically with respect to the width direction of the bag main body from the lower end of the side  22   c  closer to the side  10   b  of the bag main body, out of sides  22   b  and  22   c  of each arm portion  22 . Even when the fixed sides  22   a  are formed in this manner, the lower parts of the arm portions  22  are twisted by pulling the hooking portions  23  provided on the two opposite surfaces of the bag main body  10  in the opposite directions to each other, thus making it difficult to form folding lines in the width direction of the bag main body at the lower parts of the arm portions  22 . As a result, even in a case in which the drip bag  1 E is hooked onto a cup with a small opening diameter, the opening portion  11  of the bag main body opens wide, which facilitates pouring hot water. 
     On the other hand, in a drip bag  1   y  illustrated in  FIG.  11   , the fixed side  22   a  of the arm portion  22  extends downward vertically with respect to the width direction of the bag main body from the lower end of the side of each arm portion  22 . However, since this fixed side  22   a  extends downward from the side  22   b  closer to the center line A, one of the left and right sides  22   b  and  22   c  of each arm portion  22 , the advantageous effect of the present invention cannot be obtained. This is presumably because when the hooking portions  23  provided on the two opposite surfaces of the bag main body  10  are pulled in opposite directions to each other, a tensile force is generally applied on the center line A of the width of the bag main body, so that the arm portion  22  of the drip bag  1 E illustrated in  FIG.  10    is twisted, while the arm portion  22  of the drip bag  1   y  illustrated in  FIG.  11    is hardly twisted. 
     In comparison to the drip bag  1 A illustrated in  FIG.  1   , a drip bag  1 F illustrated in  FIG.  12    is prepared by omitting the upper connecting portion  28 . From the viewpoint of making it easier to hook the pair of hooking portions  23  on both the left and right sides of the center line A of the width of the bag main body onto the cup  100 , the upper connecting portion  28  is preferably provided. 
     In comparison to the drip bag  1 A illustrated in  FIG.  1   , a drip bag  1 G illustrated in  FIG.  13    is prepared by forming the oblique folding lines L 1  of the upper bonded portion  24  on the side closer to the upper side  10   a  relative to the protruding portion  25 . According to this drip bag  1 G, in contrast to the drip bag  1 A illustrated in  FIG.  1   , when the opening portion  11  of the bag main body  10  is opened by pulling the hooking portions  23  provided on the two opposite surfaces of the bag main body  10  in the opposite directions to each other, a portion along the upper bonded portion  24 , out of the opening shape of the bag main body  10 , tends to be straight, so that the opening shape of the bag main body is difficult to be polygonal of octagonal or more. However, when this drip bag  1 G is hooked onto a cup with a small opening diameter, there is no practical problem with the ease of pouring hot water. 
     In comparison to the drip bag  1 A illustrated in  FIG.  1   , a drip bag  1 H illustrated in  FIG.  14    is prepared by omitting the oblique folding lines L 1  of the upper bonded portion  24 , providing vertical folding lines L 4  in the upper bonded portion  24  at portions closer to the sides  10   b  of the bag main body  10  than the protruding portion  25 , and further omitting the reinforcing portions  26  therefrom. The provision of such vertical folding lines L 4  in the upper bonded portion  24  facilitates opening of the bag main body  10  into a rectangular shape. However, when this drip bag  1 H is hooked onto a cup with a small opening diameter, there is no practical problem with the ease of pouring hot water. 
     In comparison to the drip bag  1 H illustrated in  FIG.  14   , a drip bag  1 I illustrated in  FIG.  15    is prepared by omitting the provision of the protruding portion  25  in the upper bonded portion  24 . This drip bag  1 I also has no practical problem with the ease of pouring hot water, when hooked onto a cup with a small opening diameter. 
     In comparison to the drip bag  1 A illustrated in  FIG.  1   , a drip bag  1 J illustrated in  FIG.  16 A  is prepared by omitting the second central bonded portion  30 , and widening the central bonded portion  27  and making the arm portions  22  and the hooking portions  23  adjacent to each other. This drip bag  1 J also has no practical problem with the ease of pouring hot water, when hooked onto a cup with a small opening diameter. 
     In comparison to the drip bag  1 J illustrated in  FIG.  16 A , a drip bag  1 K illustrated in  FIG.  16 B  is prepared by widening the width of each of the arm portions  22  to increase the twist occurring in the fixed side  22   a.    
     In comparison to the drip bag  1 A illustrated in  FIG.  1   , a drip bag  1 L illustrated in  FIG.  17    is prepared by omitting the lower connecting portion  29  of the hooking portion  23 . This drip bag  1 L also has no practical problem with the ease of pouring hot water, when hooked onto a cup with a small opening diameter. 
     The above-described variations of the drip bag can be combined with one another as appropriate. 
     Drip Bag Usage 
     An aspect of the drip bag according to the present invention that is not filled with an extraction material can be used as a filter to be filled with an extraction material when obtaining an extraction liquid from the extraction material. On the other hand, as a use method of an aspect of the drip bag according to the present invention filled with an extraction material while the bag main body being closed, for example, the bag main body  10  is opened at the opening portion  11  when obtaining an extraction liquid, the hooking portions  23  on the two opposite surfaces of the bag main body are pulled in opposite directions to each other and hooked onto a cup, and hot water is poured into the opening portion  11  of the bag main body  10 , thereby obtaining an extraction liquid. In this case, regardless of the opening diameter of a cup, the opening portion  11  of the bag main body  10  is formed to spread easily, facilitating pouring hot water. 
     Producing Method of Drip Bag 
     The drip bag according to the present invention can be produced by applying a drip bag production sheet to a known filling and packaging machine. For example, when producing the drip bag  1 A illustrated in  FIG.  1   , a drip bag production sheet  40  illustrated in  FIG.  18    is first prepared. In this drip bag production sheet  40 , a pair of the hooking members  20  is arranged in a long water permeable filter sheet  41  with portions on the side closer to the bottom portion facing each other and with portions on the side closer to the opening portion being directed to sides of the long water permeable filter sheet  41  with a predetermined spacing therebetween. In the same drawing, a region sandwiched between adjacent chain double-dashed lines is a region used for production of one drip bag. 
     Next, as illustrated in  FIG.  19   , the drip bag production sheet  40  is folded in two so that longer sides of the sheet  40  overlap each other, and the sides are welded together (longitudinal sealing) to form a cylindrical body. Welding of the cylindrical body in a short-side direction (transverse seal) and filling of an extraction material are repeatedly performed alternately to produce a continuous drip bag body in which the sides  10   b  of the bag main bodies of the drip bags  1 A are connected to each other. The continuous drip bag body is then separated to obtain individual drip bags  1 A. Alternatively, the sides are welded and cut at the same time, so that the individually separated drip bags  1 A are continuously produced. 
     REFERENCE SIGNS LIST 
       1   x,    1 A,  1 B,  1 C,  1 D,  1 E,  1 F,  1 G,  1 H,  1 I,  1 J,  1 K,  1 L drip bag 
       10  bag main body 
       10   a  upper side of bag main body 
       10   b  side of bag main body 
       10   c  bottom side of bag main body 
       11  opening portion 
       12  opening guide line 
       20  hooking member 
       21  central portion 
       22  arm portion 
       22   a  fixed side 
       22   b  side closer to center line 
       22   c  side closer to side of bag main body 
       23  hooking portion 
       23   a  portion of hooking portion 
       24  upper bonded portion 
       25  protruding portion 
       25   a  edge side of protruding portion 
       26  reinforcing portion 
       27  central bonded portion 
       28  upper connecting portion 
       29  lower connecting portion 
       30  second central bonded portion 
       40  drip bag production sheet 
       41  water permeable filter sheet 
       100  cup 
       100 A cup with large opening diameter 
       100 B cup with small opening diameter 
     A center line of width of bag main body 
     L 1  oblique folding line 
     L 2  vertical folding line 
     L 3  vertical folding line 
     L 4  vertical folding line 
     α inclination angle