Patent Publication Number: US-6663552-B1

Title: Packaging container production method, packaging container production apparatus, and packaging material

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a packaging container production method, a packaging container production apparatus, and a packaging material, employed to form a packaging container for containing liquid, such as a beverage. 
     2. Description of the Related Art 
     Conventionally, when a packaging container for containing liquid, such as a beverage, is to be formed from a packaging material, which, in turn, is formed from a paper substrate, rectangular blanks are blanked from the paper substrate and are then formed into packaging containers by use of a packaging container production apparatus. Specifically, a blank is folded so as to form four panels to thereby form a tubular body of a rectangular cross section, which will become a trunk portion of a packaging container. Next, a filling machine processes one end of the tubular body so as to form the tubular body into a closed-bottomed tubular body. Subsequently, the filling machine fills the closed-bottomed tubular body with liquid and then processes the other end of the tubular body so as to close the other end, thereby yielding a container filled with liquid. 
     As mentioned above, a blank is folded so as to form four panels to thereby form a tubular body having a rectangular cross section. The blank has a seal allowance formed along one edge thereof. After the blank is folded to form four panels, the seal allowance and the other edge of the blank are superposed on each other, and the resultant overlap portion is sealed longitudinally to thereby form a longitudinal seal portion. Since one of the edges is located within the completed packaging container, the end face thereof is exposed to contained liquid, and thus the paper substrate comes into contact with the liquid. As a result, a certain kind of liquid may penetrate into the paper substrate through the end face, potentially causing leakage of liquid from the container. 
     To prevent such leakage, a folding allowance is formed along one edge of the blank, and the folding allowance is folded by 180° so as to form a seal allowance. The seal allowance and the other edge of the blank are superposed on each other such that the folding allowance is sandwiched between the seal allowance and the other edge. The resultant overlap portion is sealed longitudinally, thereby yielding a packaging container. 
     FIG. 1 shows a folding step in a conventional packaging container production method. 
     As shown in FIG. 1, in the folding step, a folding allowance  102  is formed along one edge of a blank  101 . The folding allowance  102  is folded so as to form a seal allowance. 
     The folding step employs a metallic die  106  having a curved groove  105  formed therein. Passing through the groove  105 , the folding allowance  102  is folded by 180° so as to form the seal allowance. Subsequently, the seal allowance and another edge  103  of the blank  101  are superposed on each other. The resultant overlap portion is sealed longitudinally so as to form a longitudinal seal portion, thereby yielding a tubular body  108  having a rectangular cross section. Thus, the end face of the other edge  103  is prevented from coming into contact with liquid, even when a packaging container is formed from the tubular body  108 . 
     Meanwhile, when the thickness, water content, hardness, and other properties of a paper substrate vary among the blanks  101 , the folded state of the folding allowance  102  varies among the blanks  101 , resulting in quality deterioration of packaging containers. In order to avoid such quality deterioration, the folded state of the folding allowance  102  must be adjusted among the blanks  101 . However, since the die  106  is stationary, adjusting the position thereof or modifying the shape of the groove  105  is difficult to perform. 
     In the folding step, the folding allowance  102  is brought into contact with the die  106  while passing through the groove  105  at a speed of 300-600 m/min. Accordingly, a large amount of paper dust is generated and contaminates the environment around the packaging container production apparatus. Also, adhering to the blank  101 , paper dust may be taken into the packaging container. 
     Since heat is generated through contact of the die  106  with the folding allowance  102  moving at high speed, the blank  101  must be cooled. Thus, a water (or air) cooling apparatus must be employed, resulting in an increase in cost of the packaging container production apparatus. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to solve the above-mentioned problems in the conventional packaging container production apparatus and to provide a packaging container production method and apparatus which do not require a die and therefore can reduce cost and which can suppress generation of paper dust to thereby improve the quality of packaging containers. Another object of the present invention is to provide a packaging material which can be used in the packaging container production method and apparatus. 
     To achieve the above object, the present invention provides a packaging container production method comprising the steps of: providing a blank formed from a paper substrate and having a predetermined shape; folding a folding allowance formed along one edge of the blank to thereby form a seal allowance; and superposing the seal allowance and another edge of the blank on each other and longitudinally sealing the resultant overlap portion to thereby form a tubular body. 
     In the folding step, the folding allowance is pressed against a running folding belt to thereby fold the folding allowance. 
     Since the folding belt is used instead of a die in order to fold the folding allowance, even when the thickness, water content, hardness, and other properties of a paper substrate vary among the blanks, the folded state of the folding allowance can be stabilized through adjustment of the position of a pulley. Thus, the quality of packaging containers can be improved. 
     In the folding step, one side of the folding allowance is in contact with the folding belt, but friction generated therebetween is very weak because of a small difference in traveling speed between blanks and the folding belt. Further, the movement of one side of the folding allowance is restricted by the folding belt, whereas the other side of the folding allowance is not in contact with the folding belt and is thus free. Thus, the resistance of the folding belt to the travel of blanks is low, whereby the generation of paper dust is suppressed to thereby improve environmental conditions around the packaging container production apparatus. Also, entry of paper dust into a packaging container, which would otherwise result from adhesion of paper dust to a blank, can be prevented. 
     Since the contact between blanks and the folding belt does not involve heat generation, an apparatus for cooling the blanks is not required, thereby reducing the cost of the packaging container production apparatus. 
     Preferably, the seal allowance and the other edge of the blank are superposed on each other such that the folding allowance abuts the other edge. 
     The present invention further provides a packaging container production apparatus comprising: conveying means for conveying a blank formed from a paper substrate and having a predetermined shape while holding the blank except at one edge; folding means for folding a folding allowance formed along the one edge of the blank being conveyed to thereby form a seal allowance; and sealing means for superposing the seal allowance and another edge of the blank on each other and longitudinally sealing the resultant overlap portion. 
     The folding means comprises a folding belt traveling in parallel with the conveying means and disposed such that the angle of inclination thereof increases with the movement of the blank. 
     Preferably, the seal allowance and the other edge of the blank are superposed on each other such that the folding allowance abuts the other edge, whereby the end face of the other edge does not come into contact with liquid contained in a completed packaging container. 
     The present invention still further provides a packaging material comprising a paper substrate. A blank having a predetermined shape is formed from the paper substrate. A folding allowance formed along one edge of the blank is folded through pressing to thereby form a seal allowance. The seal allowance and another edge of the blank are superposed on each other, and the resultant overlap portion is sealed longitudinally to thereby form the blank into a tubular body. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The structure and features of the packaging container production method, packaging container production apparatus, and packaging material according to the present invention will be readily appreciated as the same becomes better understood by referring to the drawings, in which: 
     FIG. 1 is a view showing a folding step in a conventional packaging container production method; 
     FIG. 2 is a perspective view of a packaging container according to a first embodiment of the present invention; 
     FIG. 3 is a sectional view of an essential portion of the packaging container of FIG. 2; 
     FIG. 4 is a development view showing a blank to be folded into the packaging container of FIG. 2; 
     FIG. 5 is a sectional view showing a first example of the structure of the blank of FIG. 4; 
     FIG. 6 is a sectional view showing a second example of the structure of the blank of FIG. 4; 
     FIG. 7 is a view showing the steps of forming a tubular body of the packaging container of FIG. 2; 
     FIG. 8 is a view showing a packaging container production apparatus according to the first embodiment; 
     FIG. 9 is a first view showing a folding step in the first embodiment; 
     FIG. 10 is a second view showing the folding step in the first embodiment; and 
     FIG. 11 is a view showing a step of folding a folding allowance in a second embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention will next be described in detail with reference to the drawings. 
     FIG. 2 is a perspective view of a packaging container according to a first embodiment of the present invention; FIG. 3 is a sectional view of an essential portion of the packaging container of FIG. 2; FIG. 4 is a development view showing a blank to be folded into the packaging container of FIG. 2; FIG. 5 is a sectional view showing a first example of the structure of the blank of FIG. 4; FIG. 6 is a sectional view showing a second example of the structure of the blank of FIG. 4; and FIG. 7 is a view showing the steps of forming a tubular body of the packaging container of FIG.  2 . 
     In FIGS. 2 to  7 , reference numeral  21  denotes a packaging container for containing liquid, such as drink. The packaging container  21  is formed from a blank  22 , which is treated to prevent liquid leakage and is mainly formed from a paper substrate. As shown in FIG. 5 or  6 , the blank  22  has a laminated structure. The blank  22  shown in FIG. 5 includes an outer layer  61 , a paper substrate  62 , and an inner layer  66 . The blank  22  shown in FIG. 6 includes an outer layer  61 , a paper substrate  62 , an adhesive layer  63 , a barrier layer  64 , an adhesive layer  65 , and an inner layer  66 . 
     In general, the outer layer  61 , the adhesive layers  63  and  65 , and the inner layer  66  are formed from resin, such as polyethylene or ethylene copolymer. The outer layer  61  and the inner layer  66  is preferably formed from low-density polyethylene. The barrier layer  64  is formed from, for example, aluminum foil. The outer surface of the outer layer  61  or that of the paper substrate  62  is subjected to printing as needed. 
     A method of producing the packaging container  21  will next be described. 
     As shown in FIG. 4, the blank  22  is blanked from a paper substrate into a rectangular plate-like shape, and has creases L 1  to L 4  formed vertically to thereby define a first panel Pa 1 , a second panel Pa 2 , a third panel Pa 3 , a fourth panel Pa 4 , and a fifth panel Pa 5 . The blank  22  also has creases L 6  to L 8  formed horizontally in FIG. 4 to thereby define a top seal portion T 11 , an upper panel portion T 12 , a middle panel portion T 13 , and a lower panel portion T 14 . As shown in FIG. 7, one edge of the blank  22 ; i.e., the edge of the fifth panel Pa 5  is scraped so as to form a folding allowance Pb, which is thinner than the remaining portion of the fifth panel Pa 5 . The folding allowance Pb is folded by 180° to thereby form a seal allowance S 1 . 
     The seal allowance S 1  is superposed on another edge of the blank  22 ; i.e., on the edge of the first panel Pa 1  such that the folding allowance Pb abuts the first panel Pa 1 . The resultant overlap portion is sealed longitudinally through thermo-compression, thereby forming a longitudinal seal portion S 2 . Thus, a tubular body  23  having a rectangular cross section is formed. When the tubular body  23  is formed into the packaging container  21 , the end face of the fifth panel Pa 5  is not in contact with contained liquid. 
     In a filling machine, the tubular body  23  undergoes folding and sealing along the crease L 8 , whereby a bottom portion  25  is formed by means of the lower panel portion T 14 , thereby forming a closed-bottomed tubular body. Subsequently, the closed-bottomed tubular body is filled with liquid and then undergoes folding and sealing along the creases L 6  and L 7 , whereby a top portion  26  is formed by means of the top seal portion T 11  and the upper panel portion T 12 , thereby completing the packaging container  21 . 
     Next, the step of folding the folding allowance Pb so as to form the seal allowance S 1  will be described. 
     FIG. 8 is a view showing a packaging container production apparatus according to the first embodiment; FIG. 9 is a first view showing a folding step in the first embodiment; and FIG. 10 is a second view showing the folding step in the first embodiment. 
     As shown in FIGS. 8-10, an endless folding belt  31  serving as the folding means is extended between and wound around pulleys P 1  to P 5 . Rotation effected through operation of unillustrated driving means is transmitted to the driving pulley P 1  to thereby run the folding belt  31 . Traveling between the pulley P 2  and P 3 , the folding belt  31  is twisted by 180° while being guided by an unillustrated plurality of pulleys. Then, traveling between the pulleys P 4  and P 5 , the folding belt  31  is twisted by 180° while being guided by an unillustrated plurality of pulleys, in the reverse direction of travel between the pulleys P 2  and P 3 . Through this twisted travel, the folding belt  31  can travel without self interference. Material for the folding belt  31  is not particularly limited. The folding belt  31  may be made of any material, such as rubber or chemical fiber. The cross section of the folding belt  31  has a flat rectangular shape, but may be modified as needed. 
     An endless, upper press belt  32  is extended between and wound around pulleys Pu 1  to Pu 3 . Rotation effected through operation of the above-mentioned driving means is transmitted to the driving pulley Pu 1  to thereby run the upper press belt  32 . An endless, lower guide belt  33  is extended between and wound around pulleys Pu 4  and Pu 5 . Rotation effected through operation of the above-mentioned driving means is transmitted to the driving pulley Pu 4  to thereby run the lower guide belt  33 . The folding belt  31 , the upper press belt  32 , and the lower guide belt  33  constitute a folding apparatus. 
     When the folding allowance Pb is to be folded, the blank  22  is conveyed in such a manner that a portion of the blank  22  excluding the fifth panel Pa 5  is held between the upper press belt  32  and the lower guide belt  33 . The folding belt  31  travels in parallel with and synchronously with the upper press belt  32  and the lower guide belt  33 . Accordingly, the step of folding the folding allowance Pb can be performed stably. The upper press belt  32  and the lower guide belt  33  constitute the conveying means. 
     While the folding belt  31  travels from the pulley P 4  to the pulleys P 5 , the inclination angle of the surface of the folding belt  31  abutting the folding allowance Pb varies from 0° to 180°. Accordingly, the folding angle of the folding allowance Pb is initially 0° at position A, and increases to 45° at position B, 120° at position C, and 180° at position D. The folding allowance Pb is stably folded along a folding edge  34  of a folding base  35  to thereby become the seal allowance S 1  (FIG.  7 ). FIG. 9 shows the state of the folding allowance Pb as viewed at position B, and FIG. 10 shows the state of the folding allowance Pb as viewed at position C. 
     Since a pair of upper and lower press rollers serves as the pulleys P 5 , the folding allowance Pb is reliably pressed at position D, thereby preventing springback of the folded folding allowance Pb. 
     In a sealing step subsequent to the above-described folding step, the seal allowance S 1  and the first panel Pa 1  (FIG. 3) are superposed on each other in such a manner that the folding allowance Pb abuts the first panel Pa 1 . The resultant overlap portion is sealed longitudinally through thermo-compression. An unillustrated sealing apparatus serving as the sealing means is disposed downstream of the folding apparatus with respect to the conveying direction of the blank  22 . The sealing apparatus may employ, for example, resistance heating, induction heating, or ultrasonic sealing, in order to perform sealing. 
     As described above, the step of folding the folding allowance Pb employs the folding belt  31  instead of a die. Therefore, even when the thickness, water content, hardness, and other properties of the paper substrate  62  (FIGS. 5 and 6) vary among the blanks  22 , the folded state of the folding allowance Pb can be stabilized through adjustment of the position of the pulleys P 1  to P 5 . Thus, the quality of the packaging containers  21  (FIG. 2) can be improved. 
     In the folding step, one side of the folding allowance Pb is in contact with the folding belt  31 , but friction generated therebetween is very weak, since the folding belt  31  travels synchronously with the upper press belt  32  and the lower guide belt  33  with a resultant small difference in traveling speed between the blanks  22  and the folding belt  31 . Further, the movement of one side of the folding allowance Pb is restricted by the folding belt  31 , whereas the other side of the folding allowance Pb is not in contact with the folding belt  31  and is thus free. Thus, the resistance of the folding belt  31  to the travel of the blanks  22  is low, whereby the generation of paper dust is suppressed to thereby improve environmental conditions around the packaging container production apparatus for producing the packaging containers  21 . Also, entry of paper dust into the packaging container  21 , which would otherwise result from adhesion of paper dust to the blank  22 , can be prevented. 
     Since the contact between blanks  22  and the folding belt  31  does not involve heat generation, an apparatus for cooling the blanks  22  is not required, thereby reducing the cost of the packaging container production apparatus for producing the packaging containers  21 . 
     Next, a second embodiment of the present invention will be described. The same features as those of the first embodiment are denoted by common reference numerals, and their description is omitted. 
     FIG. 11 is a view showing a step of folding a folding allowance in a second embodiment of the present invention. 
     As shown in FIG. 11, the folding allowance Pb of the fifth panel Pa 5  is not scraped, but has the same thickness as that of the rest of the blank  22 . Even when this type of the blank  22  (FIG. 4) is used, the folding allowance Pb can be folded reliably in the folding step. 
     The present invention is not limited to the above-described embodiments. Numerous modifications and variations of the present invention are possible in light of the spirit of the present invention, and they are not excluded from the scope of the present invention.