Patent Publication Number: US-11643270-B2

Title: Extraction bag

Description:
TECHNICAL FIELD 
     The present invention relates to an extraction bag for obtaining extraction liquid by immersing an extraction material filled in a bag main body made of a water permeable filter sheet in hot water. 
     BACKGROUND ART 
     For the purpose of brewing beverages such as green tea, black tea, and oolong tea in an easy and simple manner, tea bags in which such tea leaves are filled in water permeable bag main bodies having hanging strings have been widely used conventionally. Also for coffee, a tea bag type coffee extraction bag according to which a bag main body filled with ground coffee is immersed in hot water has been used in addition to a drip type extraction bag according to which hot water is poured into ground coffee. When it is attempted to immerse such a tea bag type coffee extraction bag into hot water, however, the bag main body filled with ground coffee is apt to float in the hot water due to carbon dioxide contained in the ground coffee, thus making it difficult to extract coffee sufficiently. In view of this, an extraction bag in which a hooking piece formed by a thin plate-like member is attached to one surface of a bag main body to be filled with ground coffee so that the hooking piece can be hooked onto an edge of a cup in order to prevent the bag main body filled with ground coffee from floating in hot water has been proposed (Patent Literature 1). 
     It has been also proposed that a handle portion configured to expand and contract like a pantograph by folding a thin plate-like member is attached to a bag main body filled with ground coffee and the extraction of the coffee is facilitated by moving the handle portion up and down in hot water in which the bag main body is immersed (Patent Literature 2). 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: Japanese Utility Model Registration No. 3140084 
         Patent Literature 2: Japanese Patent Application Laid-Open No. 2006-273379 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     In such a conventional coffee extraction bag according to which the bag main body filled with ground coffee is immersed in hot water, however, even when it is attempted to sink the floating bag main body forcibly into the hot water by gripping the hooking piece or the handle portion formed by the thin plate-like member, the thin plate-like member undergoes bending or deflection, thus making it difficult to sink the bag main body into the hot water. Even when the hooking piece or the handle portion is moved up and down in order to facilitate the extraction of the coffee, the bag main body cannot move up and down in the hot water in the same manner as the handle portion. Even if the bag main body temporarily sinks into the hot water, only a surface layer of the entire ground coffee filled in the bag main body swells by hot water, and the hot water is less likely to penetrate into the inside of the entire ground coffee. Thus, it is difficult for such a tea bag type extraction bag according to which the bag main body is immersed in hot water to obtain coffee liquid having a concentration about equal to that of a drip type extraction bag in an amount of time about equal to or less than that of the drip type extraction bag. 
     In view of this, it is an object of the present invention to provide a tea bag type extraction bag configured to obtain extraction liquid by immersing a bag main body filled with an extraction material such as ground coffee in hot water, capable of allowing the bag main body to be easily sunk into the hot water or moved up and down and capable of allowing the hot water to be distributed through the entire extraction material in the bag main body so as to obtain extraction liquid having a sufficient concentration easily. 
     Solution to Problem 
     The present inventor has achieved the present invention by conceiving the following: in a tea bag type extraction bag in which a thin plate-like member is attached to a bag main body filled with an extraction material, the thin plate-like member can be formed into a rigid stick shape extending from a central portion of the bag main body by configuring the thin plate-like member so as to have a particular shape. By gripping the stick-shaped portion, the bag main body can be easily sunk into hot water or moved up and down; moreover, the area of an upper surface of a portion occupied by the extraction material in the bag main body as well as its headspace can be increased; consequently, when the bag main body is moved up and down in the hot water, the hot water flows downwardly with respect to the upper surface of the extraction material in the bag main body, thus facilitating the penetration of the hot water into the inside of the extraction material. 
     Specifically, the present invention provides an extraction bag including: a bag main body formed of a water permeable filter sheet; a thin plate-like member provided on an outer surface of the bag main body; and an extraction material filled in the bag main body, wherein 
     the bag main body has a first surface and a second surface opposed to each other, and an upper side corresponding to edges of the first and second surfaces; 
     when the bag main body is developed so that the first surface is located under the upper side and the second surface is located above the upper side, 
     the thin plate-like member includes a first member on the first surface of the bag main body, and a second member on the second surface of the bag main body, and the first member and the second member are continuous with each other via a first horizontal folding line extending along the upper side; and 
     the thin plate-like member includes
         a central bonded portion bonded to the first surface of the bag main body in a central portion of the first member,   a pair of elongated regions sandwiching the central bonded portion from its left and right sides that are provided astride the first member and the second member and are capable of being pulled out from the bag main body, and   a vertical folding line along which the pair of elongated regions can be pulled out from sides closer to lateral sides of the bag main body so as to be opposed to each other.       

     The present invention also provides a hand-filled extraction bag in which the bag main body in the above-described extraction bag is unfilled with the extraction material and an opening for filling an extraction material is provided in the bag main body. 
     Advantageous Effects of Invention 
     According to the present invention, by folding the pair of elongated regions of the thin plate-like member provided on the outer surface of the bag main body filled with the extraction material so as to be opposed to each other, the pair of elongated regions suppress deflection with respect to each other and have a rigid stick shape extending from the one surface of the bag main body. Thus, the bag main body can be easily sunk into hot water or moved up and down by gripping such a stick-shaped portion. Consequently, the hot water can easily run through the bag main body. 
     Moreover, since the pair of elongated regions are provided across the two surfaces of the bag main body opposed to each other, the stick-shaped portion obtained by forming such elongated regions into a stick shape has a longer length as compared to a stick shape formed by a pair of elongated regions provided only on one surface of the bag main body. Thus, the hand gripping the stick-shaped portion can be prevented from getting hot by steam when the bag main body in the hot water is sunk or moved up and down by gripping the stick-shaped portion. 
     Furthermore, according to the present invention, the shape of the portion occupied by the extraction material in the bag main body can be changed so as to increase the area of its upper surface, and its headspace can be also increased by gripping the stick-shaped portion in such a manner as to be inclined. Consequently, hot water flowed into the bag main body is more likely to flow downwardly from the upper surface of the extraction material. Thus, extraction not only from the surface of the portion occupied by the extraction material in the bag main body but also from the entire extraction material can be facilitated. In particular, in an aspect in which the second surface of the bag main body is pulled up by a central pull-up portion of the thin plate-like member, flattening of the bag main body as a result of the bag main body being pulled in a downward direction due to the weight of the extraction material can be prevented also by the pulling up of the bag main body by the central pull-up portion, thus increasing the headspace. According to an aspect in which a reinforced portion extending in a width direction of the bag main body is further provided below the stick-shaped portion, contraction of the bag main body in the width direction thereof can be prevented from occurring, thus expanding the whole space in the bag main body. 
     Therefore, the present invention can increase the extraction rate, and thus enables extraction liquid having a concentration about equal to or higher than that of a drip type extraction method to be obtained easily in a short amount of time. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1 A  is a front view of an extraction bag  1 A (a plan view illustrating a first member side) according to an embodiment. 
         FIG.  1 B  is a rear view of the extraction bag  1 A (a plan view illustrating a second member side) according to the embodiment. 
         FIG.  2    is a developed view of the extraction bag  1 A according to the embodiment. 
         FIG.  3    is a perspective view illustrating the extraction bag  1 A with the second member of a thin plate-like member being pulled up from a second surface of a bag main body. 
         FIG.  4 A  is a side view illustrating the extraction bag  1 A according to the embodiment with elongated regions being pulled out. 
         FIG.  4 B  is a perspective view illustrating the extraction bag  1 A according to the embodiment with the elongated regions being pulled out, as viewed from a first surface side of the bag main body. 
         FIG.  4 C  is a perspective view illustrating the extraction bag  1 A according to the embodiment with the elongated regions being pulled out, as viewed from a second surface side of the bag main body. 
         FIG.  5    is a plan view illustrating a sheet for producing extraction bags. 
         FIG.  6    is an explanatory view for a producing method of extraction bags. 
         FIG.  7    is a developed view of an extraction bag  1 B according to an embodiment. 
         FIG.  8    is a side view of the extraction bag  1 B according to the embodiment with the elongated regions being pulled out. 
         FIG.  9    is a developed view of an extraction bag  1 C according to an embodiment. 
         FIG.  10    is a perspective view illustrating the extraction bag  1 C according to the embodiment with elongated regions being pulled out. 
         FIG.  11    is a developed view of an extraction bag  1 D according to an embodiment. 
         FIG.  12    is a perspective view illustrating the extraction bag  1 D according to the embodiment with elongated regions being pulled out. 
         FIG.  13    is a perspective view illustrating the extraction bag  1 D with the elongated regions being pulled out and with hooking portions  16  being hooked onto a cup. 
         FIG.  14    is a developed view of an extraction bag  1 E according to an embodiment. 
         FIG.  15    is a perspective view illustrating the extraction bag  1 E according to the embodiment with elongated regions being pulled out. 
         FIG.  16    is a developed view of an extraction bag  1 F according to an embodiment. 
         FIG.  17    is a perspective view illustrating the extraction bag  1 F according to the embodiment with elongated regions being pulled out. 
         FIG.  18    is a developed view of an extraction bag  1   x  according to a comparative example. 
         FIG.  19    is a perspective view illustrating the extraction bag  1   x  according to the comparative example with elongated regions being pulled out. 
         FIG.  20    is a developed view of an extraction bag  1 G according to an embodiment. 
         FIG.  21    is a perspective view illustrating a hand-filled extraction bag  30  according to an embodiment. 
         FIG.  22    is a perspective view illustrating the hand-filled extraction bag  30  according to the embodiment with an opening thereof being closed. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The present invention will be specifically described below with reference to the drawings. Note that the same reference signs in the drawings denote the identical or equivalent components. 
     General Configuration 
       FIGS.  1 A and  1 B  are a front view (a plan view illustrating a first member side) and a rear view (a plan view illustrating a second member side), respectively, illustrating an extraction bag  1 A with elongated regions of a thin plate-like member not being pulled out according to an embodiment of the present invention.  FIG.  4 A  is a side view illustrating the extraction bag  1 A with the elongated regions of the thin plate-like member being pulled out.  FIG.  4 B  is a perspective view illustrating the extraction bag  1 A as viewed from a first surface side of a bag main body.  FIG.  4 C  is a perspective view illustrating the extraction bag  1 A as viewed from a second surface side of the bag main body. 
     The extraction bag  1 A includes: the bag main body  3  constituted of a flat bag formed by a water permeable filter sheet; the thin plate-like member  10  provided on an outer surface of the bag main body  3 ; and an extraction material filled in the bag main body  3 . The bag main body  3  has a first surface  3 A and a second surface  3 B opposed to each other, and an upper side  4   a  corresponding to edges of these surfaces. The upper side  4   a  in the present embodiment corresponds to a mountain fold between the first surface  3 A and the second surface  3 B. 
       FIG.  2    is a developed view of the extraction bag  1 A. On the lower side of the figure from the upper side  4   a , the first surface  3 A of the bag main body and a first member  10 A of the thin plate-like member  10  provided on the first surface  3 A are shown. On the upper side of the figure from the upper side  4   a , the second surface  3 B of the bag main body and a second member  10 B of the thin plate-like member  10  provided on the second surface  3 B are shown. In this figure, a region filled with oblique lines represents a bonded region between the thin plate-like member  10  and the bag main body  3 , and a region filled with dots represents a portion where the bag main body  3  is exposed in the developed view. Note that the bonded region in the present invention is not limited to the illustrated aspect. 
     The first member  10 A and the second member  10 B are continuous with each other via a first horizontal folding line Lh 1 . The first horizontal folding line Lh 1  overlaps with the upper side  4   a  of the bag main body, and extends along the upper side  4   a.    
     A central bonded portion  11  bonded to the first surface  3 A of the bag main body is formed in a central portion of the first member  10 A. The bonded region of the central bonded portion  11  preferably includes at least a region near the first horizontal folding line Lh 1 . In the present embodiment, an approximately entire surface of the central bonded portion  11  is bonded to the bag main body  3 . 
     The thin plate-like member  10  includes a pair of elongated regions  12  (regions surrounded by long dashed double-short dashed lines in  FIG.  2   ) sandwiching the central bonded portion  11  from its left and right sides. The elongated regions  12  are formed astride the first member  10 A and the second member  10 B, and are capable of being pulled out from the bag main body  3 . 
     The thin plate-like member  10  is provided with vertical folding lines along which the pair of elongated regions  12  can be pulled out from sides closer to lateral sides  4   b  of the bag main body so as to be opposed to each other as shown in  FIGS.  4 A,  4 B, and  4 C . The vertical folding lines extend in the long-side direction of the elongated regions  12 , and serve as rotary axes of a pulling out operation when the pair of elongated regions  12  are pulled out. Note that the vertical folding lines along which the pair of elongated regions  12  can be pulled out so as to be opposed to each other in the present invention are not limited to those formed strictly in the long-side direction of the elongated regions or the up-and-down direction of the bag main body. The vertical folding line may be formed obliquely to the long-side direction of the elongated regions  12  as in a fourth vertical folding line Lv 4  to be described later. On the other hand, it is preferable in the present invention that a pair of such vertical folding lines be formed at least in the first member  10 A. It is more preferable that at least a pair of such vertical folding lines be formed also in the second member  10 B. It is yet more preferable that a vertical folding line of the second member  10 B be formed as an extension of a vertical folding line of the first member  10 A. In the present embodiment, since right and left lateral sides  11   a  of the central bonded portion  11  in the first member  10 A are separated from the elongated regions  12 , a pair of first vertical folding lines Lv 1  are formed in the first member  10 A at ends of the elongated regions  12  disposed closer to a lower side  4   c  of the bag main body than the central bonded portion  11 . Moreover, a pair of second vertical folding lines Lv 2  extending from the first horizontal folding line Lh 1  are formed in the second member  10 B. Furthermore, a third vertical folding line Lv 3  is formed in a portion where ends of the pair of elongated regions  12  are continuous with each other. 
     Note that the horizontal folding line Lh 1  and the vertical folding lines Lv 1 , Lv 2 , and Lv 3  of the thin plate-like member  10  can be formed, for example, by perforation, half cutting, or creasing. 
     Configuring the pair of elongated regions  12  extending across the first member  10 A and the second member  10 B to be capable of being pulled out from the bag main body  3  along the vertical folding lines so as to be opposed to each other is a characteristic configuration of the present invention. The pair of elongated regions  12  pulled out from the bag main body  3  can serve as a long rigid stick-shaped handle when the extraction material in the bag main body  3  is sunk into hot water. 
     In the present embodiment, the first member  10 A includes a reinforced portion  13  bonded to the bag main body  3  in a region closer to the lower side  4   c  of the bag main body than lower end portions of the elongated regions  12  ( FIG.  2   ). Consequently, the vertical folding lines Lv 1 , which serve as the axes of the pulling out operation, at the lower end portions of the elongated regions  12  are interposed between the central bonded portion  11  and the reinforced portion  13 , thereby improving the strength of the lower end portions. Moreover, the reinforced portion  13  extends in the width direction of the bag main body. This can prevent the contraction of the bag main body in its width direction due to the weight of the extraction material, thus ensuring a wide space in the bag main body  3 . Note that the reinforced portion  13  is provided as necessary in the present invention. 
     The second member  10 B in the present embodiment, on the other hand, includes a central upper end portion  14  extending from the first horizontal folding line Lh 1  between the pair of elongated regions  12 . The central upper end portion  14  is continuous with the elongated regions  12  via the second vertical folding lines Lv 2 , and floated without being bonded to the bag main body  3 . The second member  10 B also includes a central pull-up portion  15  continuous with the central upper end portion  14  via a second horizontal folding line Lh 2 . The central pull-up portion  15  is separated from the elongated regions  12 . Moreover, the central pull-up portion  15  includes a bonded region  15 A bonded with the bag main body at a portion distant from the central upper end portion  14 . Thus, when the pair of elongated regions  12  are pulled out from the bag main body  3  so as to be opposed to each other, a central portion of the second surface  3 B of the bag main body is pulled up in the direction of the upper side  4   a  of the bag main body as shown in  FIGS.  4 A and  4 C . This increases the area of an upper surface of the portion occupied by the extraction material in the bag main body, and also increases its headspace. Therefore, the extraction material can be efficiently extracted with hot water flowed into the bag main body, and an amount of time required to obtain extraction liquid having a predetermined concentration can be reduced. 
     Extraction Material 
     Examples of the extraction material filled in the bag main body  3  may include ground coffee, tea leaves such as black tea or green tea, and Chinese herbs. When ground coffee is filled in the bag main body  3  and it is attempted to immerse such a bag main body into hot water, the bag main body is generally apt to float due to carbon dioxide contained in the ground coffee, thus making extraction difficult. According to the present invention, however, the bag main body  3  can be forcibly sunk into hot water in a cup or moved up and down in the hot water in an easy manner by pulling out the elongated regions  12  so as to have a rigid stick shape and using the stick-shaped portion as a handle extending from the central portion of the bag main body  3 . This allows the hot water to penetrate into not only a surface layer of the entire ground coffee in the bag main body but also the inside of the entire ground coffee, thus making it possible to obtain extraction liquid efficiently from the entire ground coffee. With regard to an extraction material other than ground coffee, hot water can be similarly allowed to permeate the extraction material, so that extraction liquid can be obtained efficiently from the entire extraction material. 
     Since the extraction bag of the present invention is used with the extraction material being sealed in the bag main body  3 , no extraction material is spread into the outside of the bag main body during the use of the extraction bag. 
     Bag Main Body 
     The bag main body  3  in the present embodiment has a shape of a flat bag having the upper side corresponding to the mountain fold of the water permeable filter sheet and three sealed sides. The shape of the bag main body  3  in the present invention is not limited to such a flat bag. For example, a gusset bag having a gusset at its bottom or side may be used. Moreover, the upper side  4   a  of the bag main body  3  is not limited to a mountain fold, but may be a sealed side. In consideration of the producing method of the extraction bag, however, it is preferable that the upper side be a mountain fold. 
     Net planar dimensions of the bag main body  3  can be set appropriately in accordance with the size of a cup or a container used when obtaining extraction liquid using the extraction bag. For example, the bag main body  3  may have a size suitable for a commercially-available coffee cup. 
     Water Permeable Filter Sheet 
     A variety of sheets having water permeability and filterability so as to be used for extracting an extraction material can be employed as a water permeable filter sheet for forming the bag main body. A constituent material of the water permeable filter sheet can also be selected appropriately in accordance with a type of the extraction material. For example, synthetic fibers such as polyester, nylon, polyethylene, polypropylene, and vinylon; semisynthetic fibers such as rayon; woven fabrics or non-woven fabrics made of natural fibers, such as  Broussonetia papyrifera  and  Edgeworthia papyrifera , used alone or as composite fibers; mixed paper, or the like, made of Manila hemp, wood pulp, a polypropylene fiber, or the like; and paper materials such as a tea bag base sheet have been generally known as water permeable filter sheets for extracting beverages. These water permeable filter sheets can be used also in the present invention. In terms of the disposability of a used extraction bag, the water permeable filter sheet preferably contains biodegradable fiber. Examples of such biodegradable fiber may include polylactic acid, polybutylene succinate, and polyethylene succinate. In terms of imparting transparency to the water permeable filter sheet so that the state of the extraction material in the bag main body can be seen, it is preferable that a content of an inorganic pigment be reduced or no inorganic pigment be contained. 
     Whereas hot water is directly poured into an extraction material in a drip type extraction bag, hot water is always supplied to the extraction material through the water permeable filter sheet according to the extraction bag of the present invention. Thus, as far as no powder leakage of the extraction material occurs, it is preferable to employ a water permeable filter sheet having meshes larger than those of the water permeable filter sheet used in the drip type extraction bag. When the extraction material is ground coffee, for example, the air permeability of the water permeable filter sheet can be set to 130 to 600 cm 3 /cm 2 /sec (Method A of JIS LH1096 for air permeability (the method using a Frazier air permeability tester)). 
     Thin Plate-Like Member 
     The thin plate-like member preferably has water repellency. The thin plate-like member can be formed by punching a thin plate-like material such as a paper board having a surface on which a resin is laminated, or a plastic sheet. In terms of the disposability of the used extraction bag  1 A, it is preferable that the thin plate-like member be formed of a biodegradable material such as polylactic acid, polybutylene succinate, and polyethylene succinate. 
     Method of Use 
     As a packaging and distribution form of the extraction bag  1 A, it is preferable that the entire thin plate-like member  10  be provided on the surfaces of the bag main body  3  and the bag main body be flattened as shown in  FIGS.  1 A and  1 B . As a method of use starting from such a state, the second member  10 B of the thin plate-like member is first pulled out from the second surface  3 B of the bag main body so that the first member  10 A and the second member  10 B are approximately in the same plane as shown in  FIG.  3   . At this time, the bonded region  15 A ( FIG.  2   ) of the central pull-up portion  15  on the second surface  3 B of the bag main body is pulled up in the direction of the upper side  4   a , thereby changing the shape of the bag main body  3  from the flattened state to a state in which the first surface  3 A is bent. This increases the area of the upper surface of the portion occupied by the extraction material in the bag main body, and also increases its headspace. 
     Thereafter, the thin plate-like member is folded along the first vertical folding lines Lv 1 , the second vertical folding lines Lv 2 , and the third vertical folding line Lv 3  so that the pair of elongated regions  12  are opposed to each other as shown in  FIG.  4 B . Consequently, the pair of elongated regions  12  have a long rigid stick shape. The extraction bag is put into a container such as a cup by gripping such a stick-shaped portion, and hot water is poured into the container. Alternatively, the extraction bag is put into a container filled with hot water. The extraction rate of the extraction material can be increased by sinking the bag main body into the hot water or moving the bag main body up and down in the hot water with the stick-shaped portion formed by the elongated regions  12 . At this time, a part of the stick-shaped portion having a length extending across the first surface  3 A and the second surface  3 B of the bag main body that is formed by the elongated regions  12  of the first surface  3 A is fixed to the first surface  3 A, and a part of the stick-shaped portion that is pulled out from the second surface  3 B is located above the upper side  4   a  of the bag main body  3 . Since the part of the stick-shaped portion that is located above the upper side  4   a  of the bag main body  3  can be gripped by hand, the hand gripping the stick-shaped portion can be prevented from getting hot by steam even when very hot water is in the container. Of course, extraction may be performed with cold water as necessary. Alternatively, the bag main body may be left in a container such as a cup with the stick-shaped portion leaning against an inner wall of the container. 
     The bag main body after the extraction can be taken out from the container by gripping the stick-shaped portion. 
     According to such an extraction bag  1 A, extraction liquid having a desired concentration can thus be obtained easily and speedily. 
     Producing Method 
     As a method of producing the extraction bag  1 A, a sheet  20  for producing extraction bags is prepared as shown in  FIG.  5   . For example, the thin plate-like members  10  are arranged on, and bonded to, a long water permeable filter sheet  21  at predetermined intervals with the first horizontal folding line Lh 1  of the thin plate-like member  10  aligning with the long-side direction of the water permeable filter sheet  21 . In this figure, a region interposed between long dashed double-short dashed lines is used to produce a single extraction bag. 
     The extraction bags  1 A can be produced successively by using such a sheet  20  for producing extraction bags in a packaging and filling machine. In this case, the sheet  20  for producing extraction bags is first folded in half so that lateral sides thereof in the long-side direction of the sheet  20  for producing extraction bags are overlapped with each other as shown in  FIG.  6   . The lateral sides in the long-side direction are welded to form a vertical seal  22 , thereby forming a tubular body. Thereafter, a continuous extraction bag form including the extraction bags  1 A joined one above the other at the lateral sides of the bag main body  3  of the extraction bag  1 A is produced by alternately repeating the formation of a horizontal seal  23  by which the tubular body is welded in the short-side direction thereof and the filling of an extraction material M in the bag main body  3 . Such a continuous extraction bag form is separated off into individual extraction bags so as to obtain the extraction bags  1 A. Alternatively, individually-separated extraction bags  1 A are produced successively by performing cutting by melting simultaneously with the formation of the horizontal seal  23  in the short-side direction of the tubular body. 
     Modifications 
     Various changes can be made to the extraction bag of the present invention. For example, an extraction bag  1 B having a developed view shown in  FIG.  7    differs from the extraction bag  1 A having the developed view shown in  FIG.  2    in that the central pull-up portion  15  is omitted and a part of the bag main body corresponding to that portion is exposed. According to this extraction bag  1 B, the central bonded portion  11  of the bag main body  3  can be held by the stick-shaped portion formed by the pair of elongated regions  12  even when the stick-shaped portion is inclined as shown in  FIG.  8   . Thus, by inclining the stick-shaped portion when the extraction material is extracted, the shape of the portion occupied by the extraction material in the bag main body  3  can be changed so as to increase its upper surface, and its headspace can be also increased as compared to when the stick-shaped portion is vertically erected. Therefore, this extraction bag  1 B also facilitates extraction from the entire extraction material in the bag main body. 
     An extraction bag  1 C having a developed view shown in  FIG.  9    differs from the extraction bag  1 A having the developed view shown in  FIG.  2    in that the elongated regions  12  provided on the right and left sides of the central bonded portion  11  in the first member via cut lines are continuous with each other via vertical folding lines Lv 1 ′. The vertical folding lines Lv 1 ′ are those obtained by extending the second vertical folding lines Lv 2  between the central upper end portion  14  and the elongated regions  12  provided on the right and left sides of the central upper end portion  14  in the second member  10 B to the first member  10 A. This increases the length of the portion serving as a rotary axis when the elongated regions  12  are pulled out and being held by the surface of the bag main body as compared to the extraction bag  1 A having the developed view shown in  FIG.  2   , thus improving attachment strength of the stick-shaped portion formed by pulling out the pair of elongated regions  12  with respect to the bag main body  3 . 
     According to this extraction bag  1 C, the first member  10 A includes a reinforced portion  13   a  bonded to the bag main body  3  in an outer peripheral portion of the elongated regions  12 . The reinforced portion  13   a  is extended to an upper portion of the second member  10 B beyond the upper side  4   a  of the bag main body so as to form a reinforced portion  13   b  bonded to the bag main body also in the upper portion of the second member  10 B. Consequently, when the elongated regions  12  are pulled out, the upper portion of the second surface  3 B of the bag main body is held down by the reinforced portion  13   b , and the second surface  3 B of the bag main body is partially pulled up by the central pull-up portion  15  as shown in  FIG.  10   . This makes it easier to increase the headspace in the bag main body, thus further increasing the extraction rate. 
     An extraction bag  1 D having a developed view shown in  FIG.  11    differs from the extraction bag  1 C having the developed view shown in  FIG.  9    in that hooking portions  16 , each protruded in an L shape, are provided in lateral side portions of the pair of elongated regions  12  in the first member  10 A. When the elongated regions  12  are pulled out in the extraction bag  1 D, the hooking portions  16  can protrude from the surface where the central bonded portion  11  is formed as shown in  FIG.  12   . Thus, the hooking portions  16  can be hooked onto a wall of an opening of a cup  100  during the extraction of the extraction material as shown in  FIG.  13   . This allows one&#39;s hands to get off of the extraction bag  1 D while the bag main body  3  is immersed in hot water in the extraction. Before the disposal of the extracted extraction bag  1 D, the extraction bag  1 D may be hooked onto an empty cup in order to drain the extraction bag  1 D. 
     An extraction bag  1 E having a developed view shown in  FIG.  14    differs from the extraction bag  1 D having the developed view shown in  FIG.  11    in that ends of the pair of elongated regions in the second member  10 B are independently provided without making the ends continuous with each other via the third vertical folding line Lv 3 . Moreover, the ends of the pair of elongated regions  12  in the second member  10 B are provided with notches  17 . Thus, the ends of the elongated regions  12  pulled out from the bag main body can be engaged with each other by the notches  17  as shown in  FIG.  15   . The elongated regions  12  serve as a rigid stick-shaped portion also in this extraction bag  1 E. 
     Unlike the above-described extraction bags, an extraction bag  1 F having a developed view shown in  FIG.  16    includes no central pull-up portion  15 , reinforced portions  13 ,  13   a , and  13   b , etc. The extraction bag  1 F, however, includes the central bonded portion  11  in a central portion of the first member  10 A, and the pair of elongated regions  12  interposing the central bonded portion  11  therebetween are formed astride the first member  10 A and the second member  10 B. Moreover, a pair of fourth vertical folding lines Lv 4  formed obliquely to the long-side direction of the elongated regions  12  are provided between the central bonded portion  11  and the elongated regions  12 . 
     Also in this extraction bag  1 F, a rigid stick-shaped portion extending from the first surface  3 A of the bag main body can be formed by the elongated regions  12  as shown in  FIG.  17    by pulling out the pair of elongated regions  12  from the bag main body  3  while folding the thin plate-like member along the vertical folding lines Lv 3  and Lv 4  so that the elongated regions  12  are opposed to each other. By gripping this stick-shaped portion, the bag main body  3  can be sunk into hot water or moved up and down in the hot water. Thus, the extraction rate can be increased. 
     Moreover, an upper bonded portion  18  bonded to the bag main body is formed in a portion interposed between the pair of elongated regions  12  in the second member  10 B. Consequently, when the elongated regions  12  are pulled out so as to be opposed to each other, a middle portion of the bag main body expands as shown in  FIG.  17   , thus increasing the headspace. The extraction bag  1 F can increase the extraction rate of the extraction material also by such expansion. 
     An extraction bag  1   x  having a developed view shown in  FIG.  18    according to a comparative example differs from the extraction bag  1 F having the developed view shown in  FIG.  16    in that the pair of elongated regions  12  are formed only in the second member  10 B. Consequently, when the pair of elongated regions  12  are pulled out from the bag main body so as to be opposed to each other, the first member  10 A and the second member  10 B are folded along the first horizontal folding line Lh 1  as shown in  FIG.  19   . The bag main body  3  vertically suspends from the first horizontal folding line Lh 1  while keeping a flattened state. This makes it difficult to sink the bag main body  3  in hot water or move the bag main body up and down in the hot water with the elongated regions  12  pulled out from the bag main body  3 . Thus, the effects of the present invention cannot be obtained. 
     Lengths of the first member and the second member in the long-side direction may be identical with, or different from, each other in the present invention. For example, in an extraction bag  1 G having a developed view shown in  FIG.  20   , a portion capable of being gripped is elongated by extending the length of the second member in the above-described extraction bag  1 A having the developed view of  FIG.  2    toward the lower side  4   c  of the second surface  3 B of the bag main body so as to increase the length of the elongated regions  12 . 
     Hand-Filled Extraction Bag 
     A hand-filled extraction bag may be produced by leaving the bag main body  3  as an empty bag without filling the extraction material in the bag main body  3  in each of the above-described extraction bags  1 A,  1 B,  1 C,  1 D,  1 E,  1 F, and  1 G and providing an opening used for filling an extraction material in the bag main body  3 . With such a hand-filled extraction bag, an individual user of the extraction bag can fill the empty bag with an extraction material according to his or her taste, and its extraction liquid can be obtained. 
     It is preferable that the opening of the hand-filled extraction bag be provided with a means to close the opening after an extraction material is filled. For example, as an empty hand-filled bag corresponding to the above-described extraction bag  1 A, a fold-back portion  5  obtained by folding back the water permeable filter sheet that forms the first surface  3 A toward the front surface side may be provided at a lower part of the first surface  3 A of the bag main body  3 , and an opening  6  may be provided without sealing the lower end of the bag main body  3  as in a hand-filled extraction bag  30  shown in  FIG.  21   . A user of the extraction bag can close the opening  6  as shown in  FIG.  22    by inverting the front and back surfaces of the fold-back portion  5  after the extraction material M is filled by hand through the opening  6  of the bag main body  3 , which is an empty bag. 
     The means to close the opening  6  of the empty bag is not limited to the provision of the fold-back portion  5  at the lower part of the bag main body  3 . For example, a zipper described in Japanese Patent No. 4289363 may be provided in the opening  6 , or a double-faced tape for food packaging may be used. 
     Although various aspects of the present invention have been described above, the changes in the various aspects may be combined as appropriate in the present invention. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1 A,  1 B,  1 C,  1 D,  1 E,  1 F,  1 G,  1   x  extraction bag 
               2  water permeable filter sheet 
               3  bag main body 
               3   a  upper side of bag main body 
               3 A first surface 
               3 B second surface 
               4   a  upper side 
               4   b  lateral side 
               4   c  lower side 
               5  fold-back portion 
               6  opening 
               10  thin plate-like member 
               10 A first member 
               10 B second member 
               11  central bonded portion 
               11   a  lateral side of central bonded portion 
               12  elongated region 
               13 ,  13   a ,  13   b  reinforced portion 
               14  central upper end portion 
               15  central pull-up portion 
               15 A bonded region 
               16  hooking portion 
               17  notch 
               18  upper bonded portion 
               20  sheet for producing extraction bags 
               21  long water permeable filter sheet 
               22  vertical seal 
               23  horizontal seal 
               30  hand-filled extraction bag 
               100  cup 
             Lh 1  first horizontal folding line 
             Lh 2  second horizontal folding line 
             Lv 1  first vertical folding line 
             Lv 1 ′ vertical folding line 
             Lv 2  second vertical folding line 
             Lv 3  third vertical folding line 
             Lv 4  fourth vertical folding line 
             M extraction material