Patent Publication Number: US-6986729-B2

Title: Zippered bag and a method for manufacturing same

Description:
This application is a divisional of application Ser. No. 10/199,322 filed Jul. 22, 2002, now U.S. Pat. No. 6,773,163. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a zippered bag having a zipper by which a mouth portion to be formed can be opened or closed, and a method for manufacturing such a zippered bag. 
     2. Description of the Related Art 
     There have conventionally been known a self-standable pouch or a flat bag with a zipper by which a mouth portion to be formed could be opened or closed. The zipper provided on such a bag is composed of a male track and a female track engageable therewith. The male track and the female track are formed on the inner surfaces of a pair of opposing face members of a main bag body, respectively, so as to face each other and extend in the lateral direction of the main bag body. The zipper substantially extends over the main bag body in the lateral direction so that an opening operation of the zipper causes the main bag body to be opened over the entire region in the lateral direction thereof. 
     When the bag with the zipper opened is inclined and shaken lightly to hit softly the mouth portion of the bag against the rim of a vessel such as a cup, in order to pour the powdery or granular contents, with which the bag is filled, directly into the vessel, the contents may suddenly be spilled out in an unexpectedly large amount, thus causing inconvenient problems in handling. 
     In addition, the full length of the zipper is so long to substantially extend over the main bag body in the lateral direction, thus increasing the probability of occurrence of clogging of the female track with the contents. Especially in case where the bag is filed with the fine granular contents, the probability of occurrence of clogging may remarkably increase. The occurrence of clogging of the female track with the contents may make it impossible to keep the zipper in a completely closed state, thus deteriorating a function of maintaining quality of the contents in an appropriate manner. 
     SUMMARY OF THE INVENTION 
     An object of the present invention, which was made in order to solve the above-described problems, is therefore to provide a zippered bag, which has an excellent handling property facilitating a pouring operation of the bag, and prevents occurrence of clogging of the zipper, as well as a method for manufacturing such a zippered bag. 
     In order to attain the aforementioned object, a zippered bag of the first aspect of the present invention comprises: 
     a main bag body having first and second opposing face members, a top, a bottom, and first and second opposing sides; and 
     a zipper disposed on said main bag body, 
     wherein: 
     said zipper extends from one of said top and said bottom to one of said first and second opposing sides so as to be oblique relative to said one of said top and said bottom. 
     According to the above-mentioned features of the first aspect of the present invention, it is possible to form a mouth portion at a corner of the main bag body, thus decreasing the size of the mouth portion. As a result, there can be provided the zippered bag, which permits to facilitate the pouring operation of the bag filled with the powdery or granular contents, without suddenly spilling the contents. 
     In addition, decrease in size of the mouth portion leads to decrease in length of the zipper. It is therefore possible to reduce the probability of occurrence of clogging of the zipper, even when the bag is filled with fine powdery or granular material. Even if the clogging of the female track occurs, the material with which the zipper is clogged can easily be removed therefrom. 
     In the second aspect of the present invention, said zipper may comprise a male track and a female track engageable therewith. According to the feature of the second aspect of the present invention, the structure of the zipper becomes simple and reliable functions thereof can be ensured. 
     In the third aspect of the present invention, said male track and said female track may be formed on inner surfaces of said first and second opposing face members by an injection molding, respectively. According to the above-mentioned feature of the third aspect of the present invention, formation of the male track and the female track can be facilitated. 
     In the fourth aspect of the present invention, each of said male track and said female track may comprise a main portion and end portions provided on opposite ends of said main portion in a longitudinal direction thereof, each of said end portions having a smaller height than that of said main portion. According to the above-mentioned feature of the fourth aspect of the present invention, it is possible to reduce the probability that a gap may be formed between heat-sealed portions of the main body and the longitudinal edge of the zipper. 
     In the fifth aspect of the present invention, said main bag body may have a sealed zone, which is placed on an outer side of said zipper, said sealed zone having opening guide portions, which are provided in parallel with said zipper so that said sealed zone is to be easily torn open along said opening guide portions. According to the above-mentioned feature of the fifth aspect of the present invention, the sealed zone can easily be torn open along the opening guide portions and the mouth portion completely formed in the bag along the straight line can be obtained. In addition, the opening guide portions may serve as a reinforcement member for the mouth portion of the bag. 
     In order to attain the aforementioned object, a method of the sixth aspect of the present invention for manufacturing a zippered bag comprises the steps of: 
     folding a sheet of film to provide first and second opposing face members, said first and second opposing face members having a folded bottom edge, first and second opposing side edges and opposing top edges; 
     folding upper portions of said first and second opposing face members outward along reference lines, which respectively extend on said first and second opposing face members in parallel with said opposing top edges so as to be apart therefrom by a prescribed distance, to provide first and second folded portions with their inner surfaces exposed; 
     heat-sealing said first and second opposing side edges together except said first and second folded portions; 
     subjecting said first and second folded portions to an injection molding to form a male track on the inner surface exposed of one of said first and second folded portions and a female track on the inner surface exposed of an other of said first and second folded portions, said male track and said female track being placed along straight lines, which extend from respective side edges of said first and second folded portions to respective top edges thereof, said male track and said female track being engageable with each other to constitute a zipper; 
     unfolding said first and second folded portions to bring the opposing side edges of the one of said first and second folded portions into contact with the opposing side edges of the other thereof to convert said first and second folded portions into first and second unfolded portions and engage said male track with said female track to keeping said zipper in a closed state so as to be oblique relative to said opposing top edges, thus providing upper and lower engaging points of the zipper; 
     heat-sealing the opposing side edges of one of said first and second unfolded portions to the opposing side edges of an other thereof, respectively, to form a first upper-side heat-sealed portion including said lower engaging point and a second upper-side heat-sealed portion; and 
     heat-sealing the top edges of said first and second unfolded portions together in a region from said upper engaging point to an upper end of said first upper-side heat-sealed portion, thus forming a non-sealed opening portion in a region from said upper engaging point to un upper end of said second upper-side heat-sealed portion. 
     According to the above-mentioned features of the sixth aspect of the present invention, it is possible to form a mouth portion at a corner of the main bag body, thus decreasing the size of the mouth portion. As a result, there can be provided the zippered bag, which permits to facilitate the pouring operation of the bag filled with the powdery or granular contents, without suddenly spilling the contents. In addition, decrease in size of the mouth portion leads to decrease in length of the zipper. It is therefore possible to reduce the probability of occurrence of clogging of the zipper, even when the bag is filled with fine powdery or granular material. Even if the clogging of the female track occurs, the material with which the zipper is clogged can easily be removed therefrom. Application of the injection molding facilitates formation of the zipper, which extends from the top of the main bag body to the side thereof so as to be oblique relative to the top of the main bag body. The zippered bag as manufactured has the non-sealed portion at the top of the bag, thus making it possible to fill the bag with the contents through the non-sealed portion. 
     In order to attain the aforementioned object, a method of the seventh aspect of the present invention for manufacturing a zippered bag comprises the steps of: 
     continuously providing an elongated linear zipper on an inner surface of a strip of film, while traveling said strip of film in a longitudinal direction thereof, to prepare a film-material strip with the elongated linear zipper; 
     determining areas, each of which has a top, a bottom and opposing sides, of the film-material strip to which a heat-sealing step is to be applied, so that said elongated linear zipper extends from said top to one of said opposing sides so as to be oblique relative to said top; 
     subjecting said areas of the film-material strip to said heat-sealing step; and 
     cutting said film-material strip into a plurality of zippered bags. 
     According to the above-mentioned features of the seventh aspect of the present invention, it is possible to manufacture the zippered bag utilizing the linear zipper, which has previously been formed through an extrusion molding, even with the use of the other molding method than the injection molding. As a result, it is not necessary to provide a manufacturing line for the zippered bag with the injection molding machine, thus making it possible to simplify the manufacturing process. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view illustrating a zippered bag of an embodiment of the present invention; 
         FIG. 2  is a perspective view illustrating the zippered bag as shown in  FIG. 1 , with the mouth portion opened; 
         FIG. 3  is a cross-sectional view of a zipper provided in the zippered bag as shown in  FIG. 1 ; 
         FIG. 4  is a plan view illustrating the zipper as shown in  FIG. 3 ; 
         FIG. 5  is a perspective view illustrating an example of a heat-sealing step in a method for manufacturing the zippered bag as shown in  FIG. 1 ; 
         FIG. 6  is a cross-sectional view of an injection molding machine used to carry out an injection molding step for forming the zipper, which is provided in the zippered bag as shown in  FIG. 1 ; 
         FIG. 7  is a perspective view illustrating a strip of film on which a plurality of sets of male and female tracks for the zipper has been formed through the injection molding step as shown in  FIG. 6 ; 
         FIGS. 8(   a ),  8 ( b ) and  8 ( c ) are views illustrating the steps for heat-sealing the edges of the main bag body to complete formation of the zippered bag, after formation of the male and female tracks on the first and second folded portion with their inner surfaces exposed; 
         FIG. 9  is an enlarged front view illustrating a portion of the zippered bag provided with opening guide portions, the portion of which is to be torn open to form a mouth portion; 
         FIG. 10  is an enlarged perspective view illustrating the zippered bag as shown in  FIG. 9 , in which the portion of the zippered bag has been torn open to form the mouth portion as opened; 
         FIG. 11  is a descriptive view illustrating the other method for manufacturing the zippered bag of the present invention; and 
         FIG. 12  is a front view of the zippered bag as manufactured in accordance with the method as shown in  FIG. 11 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Now, embodiments of a zippered bag of the present invention will be described in detail below with reference to the accompanying drawings. 
       FIG. 1  is a front view illustrating the zippered bag of the embodiment of the present invention and  FIG. 2  is a perspective view illustrating the zippered bag as shown in  FIG. 1 , with the mouth portion  10  opened. The zippered bag is manufactured in the form of self-standable pouch  1 , which is composed of a pair of opposing face members  2 ,  2  and a curved bottom  3 . The opposing side edges  5 ,  6  and the top edge  8  of the one face member  2  are heat-sealed to the corresponding side edges  5 ,  6  and the corresponding top edge  8  of the other face member  3 , respectively. The curved bottom  3  is inserted into the lower opening of the bag body so that the convex side of the curved bottom  3  faces downward. The curved bottom  3  is heat-sealed at its periphery to the lower inner surfaces of the face members  2 ,  2 . A main bag body  1 A is prepared in this manner. 
     The self-standable pouch  1  is provided on its upper side with a zipper  20 . The zipper  20 , which is formed on the inner surfaces of the face members  2 ,  2 , permits to open or close a mouth portion  10 , which is to be formed by tearing a triangular sealed zone. The zipper  20  extends linearly from the left-hand side of the main bag body  1 A to the top thereof so as to be oblique to the top thereof. The mouth portion  10  of the self-standable pouch  1  is located at the upper and left-hand corner portion of the main bag body  1 A, in the vicinity of which the zipper  20  is formed. The top edge  8  and the left-hand side edge  5  of the main bag body  1 A are provided with notches  11 ,  11 , respectively, which are located outside the zipper  20  in the vicinity thereof. The notches  11 ,  11  serve as an opening facilitation member from which the triangular sealed zone of the main bag body  1 A can be torn open so as to form the mouth portion  10  of the self-standable pouch  1 . The mouth portion  10  can be easily be formed by tearing the triangular sealed zone of the main bag body  1 A from one of the notches  11 ,  11  along the zipper  20 . 
     With respect to material of which the face members  2 ,  2  and the bottom  3  forming the self-standable pouch  1 , there may be used a sheet of resin such as polyester, nylon, polypropylene and polyethylene, or a laminate of at least two sheets of such resin. 
     In case where the transparent self-standable pouch  1  is formed of a laminate, the laminate may have the layer structure of (a) (1) a biaxial oriented polyester (PET) or biaxial oriented nylon layer, (2) a printing layer, (3) a dry laminate (DL) adhesive layer and (4) a non-oriented polypropylene (CCP) layer or (b) (1) a biaxial oriented polyester (PET) or biaxial oriented nylon layer, (2) a printing layer, (3) a dry laminate (DL) adhesive layer and (4) a straight chain-low density polyethylene (L-LDPE) layer. 
     In case where the opaque self-standable pouch  1  is formed of a laminate including an aluminum foil layer, the laminate may have the layer structure of (a) (1) a biaxial oriented polyester (PET) or biaxial oriented nylon layer, (2) a printing layer, (3) a dry laminate (DL) adhesive layer, (4) an aluminum (AL) layer, (5) a dry laminate (DL) adhesive layer and (6) a non-oriented polypropylene (CCP) layer or (b) (1) a biaxial oriented polyester (PET) or biaxial oriented nylon layer, (2) a printing layer, (3) a dry laminate (DL) adhesive layer, (4) an aluminum (AL) layer, (5) a dry laminate (DL) adhesive layer and (6) a straight chain-low density polyethylene (L-LDPE) layer. 
     The zipper  20  formed in the vicinity of the mouth portion  10  of the bag is composed of a male track  21  and a female track  24  engageable therewith, as shown in  FIG. 3 . The male track  21  has an elongated base  22  secured on the inner surface of the face member  2  and an elongated engaging projection  23 , which projects from the central portion of the base  22  in the lateral direction thereof toward the female track  24 . The engaging projection  23 , which substantially has a circular cross-section, extends over the whole base  22  in the longitudinal direction. The female track  24  has an elongated base  25 , an elongated connection portion  27 , which is integrally formed with the base  25  so as to project from the central portion of the base  25  in the lateral direction thereof toward the male track  21  and an elongated receiving portion  26 , which is integrally formed with the longitudinally extending edge of the connection portion  27 . The receiving portion  26  has an elongated groove  28  into which the engaging portion  23  of the male track  21  can detachably be inserted. The receiving portion  26 , which substantially has an outer curved surface corresponding to a cylindrical shape in the cross section of the female track  24 , extends over the whole base  25  in the longitudinal direction. The groove  28  of the receiving portion  26  also substantially has a circular cross-section. 
     As shown in  FIG. 4 , the male track  21  is composed of a main portion and end portions  21   a ,  21   a  provided on the opposite ends of the main portion. The female track  24  is also composed of a main portion and end portions  24   a ,  24   a  provided on the opposite ends of the main portion. Each of the end portions  21   a ,  21   a  of the male track  21  has a smaller height than that of the main portion so as to be gradually smaller toward the opposite ends of the male track  21 . Each of the end portions  24   a ,  24   a  of the female track  24  also has a smaller height than that of the main portion so as to be gradually smaller toward the opposite ends of the female track  24 . A pair of end portions  21   a ,  24   a  of the male and female tracks  21 ,  24  is placed on the heat-sealed side edge  5  of the face members  2 ,  2  and the other pair of end portions  21   a ,  24   a  thereof is placed on the heat-sealed top edge  8  of the face members  2 ,  2 . Decrease in height of the end portions  21   a ,  24   a  of the male and female tracks  21 ,  24  ensures the complete heat-sealing condition of the face members  2 ,  2  without causing defects in heat-sealing of such a position. In addition, gradual decrease in height of the end portions  21   a ,  24   a  of the male and female tracks  21 ,  24  prevents a gap from being formed between the heat-sealed side edge  5  and the heat-sealed top edge  8  of the face members  2 ,  2 , on the one hand, and the opposite ends of the zipper  20 , on the other hand, respectively. 
     The male track  21  and the female tack  24  are formed of thermoplastic resin on the inner surfaces of the face members  2 ,  2  by an injection molding in a manner as described later. 
     Description will be given below of a method for manufacturing the self-standable pouch  1 . 
     As shown in  FIG. 5 , a strip of film  30  is subjected to the first folding step to form a folded bottom portion  32  placed in the central position thereof in the lateral direction so that the opposite edges of the strip of film  30 , which extend in the longitudinal direction thereof, face each other and are placed above the folded bottom portion  32 , while traveling the strip of film  30  in the longitudinal direction. The folded bottom portion  32  has a single pleat a convex side of which faces upward. Then, the second folding step is carried out to fold the upper portions of the strip of film  30  outward along reference lines, which respectively extend on the opposing faces of the strip of film  30  in parallel with the upper opposite edges thereof so as to be apart therefrom by a prescribed distance, to provide the first and second folded portions  33 ,  33  with their inner surfaces exposed. 
     Then, the first heat-sealing step is applied to the portion  31 ,  31  of the strip of film  30 , which are located below the first and second folded portions  33 ,  33 , in the vertical direction to form the vertical heat-sealed portion  35  having the prescribed width. After completion of the heat-sealing step, the strip of film  30  is traveled by a prescribed distance, and then the same heat-sealing step is carried out to form the other vertical heat-sealed portion. A plurality of vertical heat-sealed portions  35  is continuously formed in this manner by carrying out the first heat-sealing step. The adjacent two vertical sealed portions define the space for the single self-standable pouch  1  and also form the opposing side edges  5 ,  6  of the pouch  1 . After completion of formation of the vertical sealed portions, the second heat-sealing step is applied to the folded bottom portion  32  and the corresponding lower portions  31 ,  31  of the strip of film  30  to form a horizontal heat-sealed portion  36 , which is to form the bottom  3  of the pouch  1 . The above-mentioned horizontal heat-sealed portion  36  has a curved portion a convex side of which face downward. 
     The first and second folding steps and the first and second heat-sealing steps as described above may be carried out simultaneously, while traveling the strip of film  30  in the longitudinal direction. 
     The strip of film  30  provided with the vertical heat-sealed portions  35  for forming the opposing side edges  5 ,  6  of the pouch  1  and the horizontal heat-sealed portions  36  for forming the bottom  3  thereof is transferred into an injection molding machine  40 , as shown in  FIG. 5 . The injection molding machine  40  is to form the male and female tracks of the zipper  20  by which the mouth portion  10  of the self-standable pouch  1  can be opened or closed, on the inner surfaces of the first and second folded portions  33 ,  33  of the strip of film  30 . 
     As shown in  FIG. 6 , the male track  21  and the female track  24  are formed on the inner surfaces of the first and second folded portions  33  of the strip of film  30 , which is transferred into the injection molding machine  40 . A mold  41  of the injection molding machine  40  has a male track forming section  42  for forming the male track  21  on the inner surface of the first folded portion  33  of the strip of film  30 , on the one hand, and a female track forming section  43  for forming the female track  24  on the inner surface of the second folded portion  33  thereof, on the other hand. In addition, the injection molding machine  40  is provided with a pair of supporting tables  45 ,  45  for supporting horizontally the first and second folded portions  33 ,  33  thereon. 
     The male track forming section  42  and the female track forming section  43  communicate through passages  46 ,  46  with a cylinder (not shown), which is filled with molten resin having fluidity. Consequently, the molten resin flows into these forming sections  42 ,  43  through the passages  46 ,  46  from the cylinder. The resin supplied into the forming sections  42 ,  43  is cooled therein to solidify so as to form the male track  21  and the female track  24 . 
     The male track  21  and the female track  24  are oblique relative to the longitudinal central line of the strip of film  30  so as to be symmetric with respect to the above-mentioned longitudinal central line, as shown in  FIG. 7 . More specifically, the male track  21  linearly extends from the edge of the first folded portion  33 , which is to form the top edge  8  of the self-standable pouch  1 , to a border line  5   a  of the strip of film  30 , which is perpendicular to the traveling direction of the strip of film  30  and corresponds to the vertical heat-sealed portion  35 . The female track  24  also linearly extends from the edge of the second folded portion  33 , which is to form the top edge  8  of the self-standable pouch  1 , to a border line  5   a  of the strip of film  30 , which is perpendicular to the traveling direction of the strip of film  30  and corresponds to the vertical sealed portion  35 . Then, the strip of film  30  is cut along the vertical central line of the respective vertical heat-sealed portions  35  into a plurality of semi-finished goods for the self-standable pouch  1 . 
     Then, the steps as shown in  FIGS. 8(   a ) to  8 ( c ) are carried out to complete manufacture of the self-standable pouch  1  filled with the contents. 
     More specifically, in the step as shown in  FIG. 8(   a ), the first and second folded portions  33 ,  33  are unfolded upward to bring the opposing side edges of the first folded portion  33  into contact with the opposing side edges of the second folded portion  33  to convert the first and second folded portions into the first and second unfolded portions  33 ,  33  and engage the male track  21  with the female track  24  to keeping the zipper  20  in a closed state so as to be oblique relative to said opposing top edges, thus providing the upper and lower engaging points of the zipper  20 . Then, the opposing side edges of the first unfolded portion  33  and the opposing side edges of the second unfolded portion  33  are heat-sealed to each other to form the first upper-side heat-sealed portion including the above-mentioned lower engaging point of the zipper  20  and the second upper-side heat-sealed portion. Then, the top edges of the first and second unfolded portions  33 ,  33  together in a region from the above-mentioned upper engaging point of the zipper  20  to the upper end of the first upper-side heat-sealed portion, thus forming a non-sealed opening portion  8 A in a region from the above-mentioned upper engaging point of the zipper  20  to the upper end of the second upper-side heat-sealed portion. Then, the notches  11 ,  11  serving as the opening facilitation member are formed on the top edge  8  and the left-hand side edge  5  of the main bag body  1 A so as to be located outside the zipper  20  in the vicinity thereof, as shown in  FIG. 1 . Then, the pouch  1  is filled with the powdery or granular contents through the non-sealed opening portion  8 A as shown in  FIG. 8(   b ). Then, the heat-sealing step is applied to the non-sealed opening portion  8 A to close it to complete the manufacture of the self-standable pouch  1  filled with the contents as shown in  FIG. 8(   c ). 
     Completion of the above-described steps forms the self-standable pouch  1  serving as the zippered bag as shown in  FIGS. 1 and 2 . The present invention is applied to the self-standable pouch  1  as described above, but applicable to a flat bag with a zipper. 
     The zippered bag as described above is a standard type, which is provided at the mouth portion of the bag with no other specific member than the zipper  20 . Providing the bag in the sealed zone, which is placed on the outer side of the zipper  20 , with opening guide portions  51 ,  51 ,  52 ,  52  as shown in  FIGS. 9 and 10 , makes it possible to improve the bag in its convenience. 
     As shown in  FIG. 9 , there are formed in the sealed zone, which is placed on the outer side of the zipper  20 , the opening guide portions  51 ,  51 ,  52 ,  52  which facilitate an tearing operation of the bag in parallel with the zipper  20 . The opening guide portions are composed of a pair of trapezoidal sections  51 ,  51 , which are placed in the above-mentioned sealed zone on the outer side of the zipper  20  and have the prescribed height, and a pair of triangular sections  52 ,  52 , which are place outside the trapezoidal sections  51 ,  51 . The trapezoidal sections  51 ,  51  and the triangular sections  52 ,  52  have a larger thickness than that of the film forming the opposing face members of the zippered bag  50 . The trapezoidal sections  51 ,  51  are symmetric with respect to a line “L” connecting the corner “P” of the bag to the center “Q” of the zipper  20  in its longitudinal direction, and the triangular sections  52 ,  52  are also symmetric with respect to the same line “L”. The trapezoidal sections  51 ,  51  and the triangular sections  52 ,  52  are spaced apart from each other by a prescribed distance. 
     A top edge  58  and a left-hand side edge  55  of the zippered bag  50  are provided with notches  61 ,  61 , respectively, which are formed along the straight line passing through the gap between the trapezoidal section  51  and the triangular section  52 . The notches  61 ,  61  serve as the opening facilitation member. More specifically, the sealed zone of the zippered bag  50  can easily be torn open along the gap between the trapezoidal sections  51 ,  51  and the triangular sections  52 ,  52 , while being guided by means of these sections, so as to form the mouth portion  60 . 
     After the triangular sections  52 ,  52  are torn off and the mouth portion  60  is expanded to open, the trapezoidal sections  51 ,  51  serve as a reinforcement member for the mouth portion  60  of the zippered bag  50  as shown in  FIG. 10 . More specifically, the gap between the trapezoidal sections  51 ,  51  is formed so as to correspond to the center “Q” of the zipper  20 , with the result that the central portion of the mouth portion  60  in the longitudinal direction has a relatively smaller rigidity. The mouth portion  60  can therefore be deformed easily at the central portion thereof. On the contrary, the other portions of the mouth portion  60  than the central portion thereof have larger rigidity than the central portion of the mouth portion  60 , due to the trapezoidal sections  51 ,  51 , so as to prevent easy deformation of the above-mentioned other portions of the mouth portion  60 . The trapezoidal sections  51 ,  51  serve as a stretching member for the mouth portion  60 . Pushing the opposite ends of the opened zipper  20  toward the center “Q” thereof to open the mouth portion  60  causes the mouth portion  60  to bend at the center “Q” of the zipper  20 , with the result that the thus bent portions are expanded outward in the thickness direction of the zippered bag  50 , while being guided by means of the trapezoidal sections  51 ,  51 . 
     The existence of the trapezoidal sections  51 ,  51  makes it possible to form the mouth portion  60  as opened having a parallelogram or rectangular shape, four corners of which correspond to the opposite edges  60   a ,  60   a  of the mouth portion  60  and the central portions “Q” of the zipper  20 . Any one of the above-mentioned four corners of the mouth portion  60  may serve as a pouring guide member, when the bag  50  with the zipper  20  opened is inclined and shaken lightly to hit softly the mouth portion  60  of the bag  50  against the rim of a vessel such as a cup, in order to pour out the contents. In case where the bag  50  is filled with the powdery or granular contents, it is possible to pour out successfully such contents into the vessel without splashing or spilling them around the vessel. 
     The above-described trapezoidal sections  51 ,  51  and the triangular sections  52 ,  52 , which serve as the opening guide portions, are formed through the injection molding. When the male track  21  and the female track  24  of the zipper  20  are formed on the first and second folded portions  33 ,  33  through the injection molding as described above, these sections  51 ,  51 ,  52 ,  52  are also formed on the first and second folded portions  33 ,  33  of the strip of film  30  through the similar injection molding. 
     In the above-described embodiment of the present invention, the bag has the zipper in which the male and female tracks are formed through the injection molding. However, the present invention is not limited only to such an embodiment. In the present invention, it may be adopted a manufacturing method in which an elongated linear zipper that has previously been formed through an extrusion molding, is bonded to the strip of film to form the zippered bag, as shown in  FIG. 11 . 
       FIG. 11  shows the other embodiment of the present invention in which a method for manufacturing the zippered bag includes a step of feeding a strip of male track  71  and a strip of female track  72  on the inner surfaces of the first and second strips of film  70 ,  70 , respectively to bond these tracks  71 ,  72  thereon, while traveling the first and second strips of film  70 ,  70  in their longitudinal direction. As shown in  FIG. 11 , the first and second strips of film  70 ,  70  are fed in the longitudinal direction so as to be in parallel with each other in a feeding zone, and the strip of male track  71  and the strip of the female track  72  are fed between the first and second strips of film  70 ,  70  so that these tracks  71 ,  72  are placed in prescribed positions of the inner surfaces of the first and second strips of film  70 ,  70 , respectively. The strips of the male and female tracks  71 ,  72  are wound on reels  80 ,  80 , respectively. These strips of male and female tracks  71 ,  72 , which are supplied from the reels  80 ,  80 , respectively, are bonded on the opposing inner surfaces of the first and second strips of film  70 ,  70  in the respective positions, so as to be in parallel with the respective one side edges  70   a ,  70   a  of the first and second strips of film  70 ,  70  in the vicinity thereof. 
     After completion of the step of bonding the strips of male and female tracks  71 ,  72  on the first and second strips of film  70 ,  70  to prepare the first film-material strip with the strip of male track  71  and the second film-material strip with the strip of female track  72 , the first film-material strip  70  with the strip of male track  71  is placed on the second film-material strip  70  with the strip of female track  72  as shown in  FIG. 11  in arrows with dotted lines. Prior to such a placing step, a precise positional adjustment of these strips  70 ,  70  is made so that the male track  71  of the former strip  70  engages with the female track  72  of the latter strip  70 . 
     Then, there is carried out a step for determining areas, each of which has a top, a bottom and opposing sides, of the film-material strips  70 ,  70  to which the subsequent heat-sealing step is to be applied, so that the male and female tracks  71 ,  72  engaging with each other linearly extend from the top  77  of the above-mentioned area to one  76   a  of the opposing sides thereof so as to be oblique relative to the top  77  of the above-mentioned area. More specifically, the above-mentioned step for determining the areas is carried out by inclining the reference line parallel with the opposing sides  76   a  of the above-mentioned area of the film-material strips  70 ,  70  relative to the side edges  70   a ,  70   a  thereof, i.e., the traveling direction thereof by a prescribed angle as shown in  FIG. 11  in two-dot chain lines. Then, the thus determined areas of the film-material strips  70 ,  70  are subjected to the heat-sealing step to heat-seal the opposing sides  76   a ,  76   b , the bottom  78  and a part  77   a  of the top  77  for each of the above-mentioned areas as determined so that the areas thus heat-sealed are arranged obliquely in the traveling direction of the film-material strips  70 ,  70 . Then, the film-material strips  70 ,  70  are cut into a plurality of zippered bags  90 , each of which has a non-sealed opening portion  77   b  formed at the top  77  as shown in  FIG. 12 . The zippered bag  90  is to be filled with the contents through the non-sealed opening portion  77   b . Then, the non-sealed opening portion  77   b  is to be heat-sealed, thus completing manufacture of the zippered bag filled with the contents. 
     In the above-described embodiment, the method of the present invention is applied to manufacture of the flat zippered bag. However, the method of the present invention may be applied to manufacture of the self-standable zippered bag utilizing the linear zipper, which has previously been formed through the extrusion molding. 
     According to the present invention as described in detail, it is possible to manufacture the zippered bag, which permits to pour easily the contents received therein, without splashing or spilling them around the bag. The present invention provides more remarkable effects in case where the bag is filled with the powdery or granular contents. 
     In addition, the full length of the zipper can be decreased in comparison with the conventional bag. It is therefore possible to reduce the probability of occurrence of clogging of the zipper. Even if the clogging of the zipper occurs, the material with which the zipper is clogged can easily be removed therefrom. 
     The entire disclosure of Japanese Patent Application No. 2001-221935 filed on Jul. 23, 2001 including the specification, claims, drawings and summary is incorporated herein by reference in its entirety.