METHOD OF MAKING BLOW-MOLDED BAG

Abstract: A method of making a blow-molded bag of thermoplastic resin for containing medicines, foods, and cosmetics, whereby a thermoplastic resin is blow-molded into a bag having a barrel part (1) provided with flat side walls facing each other as well as a mouth part (2) continuous from said barrel part (1); the flat surface of the barrel part (1) of said bag is supported by a pushing surface (8) of pushing jig (6) smaller in area than said flat surface so that opposing side walls of the barrel part (1) may come into close contact with each other; and items required are printed on the upper wall surfaces of opposing side walls of the barrel part (1).

Description: TECHNICAL FIELD The present invention relates to a manufacturing method for a blowbag (flexible container) comprising a thermoplastic material and used for containing pharmaceuticals, foodstuffs, cosmetics and the like. BACKGROUND ART Flexible blowbottles comprising a thermoplastic material and used for containing pharmaceuticals, foodstuffs, cosmetics and the like have been widely known conventionally to the extent that no further description here is necessary. In general, the body portion of such blowbottles deforms when a plate for printing is pressed onto their surfaces due to their flexibility; hence, it is extremely difficult to use direct printing to indicate the contents of the bottle and the like. Therefore, a conventional method has been to apply a positive pressure to the inside of the bottle and to achieve a balance between the positive pressure and the printing pressure so that the shape of the bottle is maintained when direct printing is performed thereon. However, as shown in FIG. 9, in the case of a blowbag, when the sectional shape of the body portion is flat, and when it is comprised of a thermoplastic material having a ratio of bending elasticity of between 500 - 10000 kg/cm 2 , the application of a positive pressure to the inside of the blowbag flexibly deforms the body portion 1 of the blowbag when printing is performed to that surface using a transfer roller 7, and it is difficult to maintain the required shape of the blowbag. As a result, because it is extremely difficult to balance the printing pressure and the positive pressure, slippage occurs when there is printing and it is extremely difficult to have suitable printing. In the light of these problems, the present invention has as an object the provision of a blowbag manufacturing method which supports a blowbag body portion by a pressing surface of a pressing jig so as to bring an upper wall of the blowbag body portion in close contact with an opposing lower wall of the blowbag body portion so that slippage during printing of the upper surface of the body portion in this status of close contact is completely prevented, and so that even in the case of a flexible blowbag comprising a thermoplastic material having a ratio of bending elasticity of between 500 to 10000 kg/cm 2 , it is possible for the body portion to have highly accurate printing by a transfer roller. In this connection GB-A-0 679 491 discloses already a blowbag manufacturing method according to the preambles of the claims 1 and 3 as well as an apparatus according to the preambles of the claims 8 and 9. In this known method and apparatus a collapsing plate is moved downward against a flexible bottle, which thereby collapses and is clamped between the collapsing plate and a supporting plate. This operation flattens an upper wall portion of the bottle against a lower wall portion of the bottle on the supporting plate. The collapsing plate is cut out at the center thereof so that an upper surface of the collapsed bottle is exposed to a printing die as it is brought down against the exposed surface. However, proper printing by using a transfer roller is extremely difficult or even impossible as the brought down collapsing plate is positioned above the level of the flattened wall portion of the bottle. This makes it difficult to perform any type of printing operation. DISCLOSURE OF THE INVENTION The present invention is directed to a blowbag manufacturing method as defined in claim 1 and to an apparatus used in a blowbag manufacturing method as defined in claim 7. Particular embodiments of the invention are claimed in dependent claims. A blowbag manufacturing method according to a particular embodiment of the present invention blowmolds a blowbag having a body portion with opposing walls which are flat in section and an opening portion connected to the body portion, and comprising a thermoplastic material having a ratio of bending elasticity of between 500 - 10000 kg/cm 2 , and flat surfaces of the blowmolded blowbag body portion are supported by a pressing surface of a pressing jig having an area smaller than the flat surfaces and so that the flat surfaces are in close contact, and required items are printed to an upper side wall surface of opposing walls of the body portion and which are in close contact with the pressing jig. In addition, in the process of pressing the pressing jig, a frame member is provided from above, and so as to correspond to a side surface of a pressing surface, and the required items are then printed to the surface of the blowbag. According to a particular embodiment of the blowbag manufacturing method of the present invention, a body portion of a blowbag comprising a thermoplastic material is supported and pressed by a pressing surface of a pressing jig having an area smaller than the flat surface, and in the process of pressing the pressing jig, a periphery of a body portion is pressed by a member corresponding to a side surface of a pressing surface from above and so opposing walls of a body portion are in a status of close contact. Then, when the blowbag is in such as status, required printing is performed to a body portion which is being held flat on a pressing surface of a pressing jig. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevation view of a pharmaceutical liquid container which is one example of a blowbag relating to the present invention; FIG. 2 is a sectional view of the above; FIG. 3 is a perspective view of one example of an apparatus used in the blowbag manufacturing method of a first embodiment of the present invention; FIG. 4 and FIG. 5 are partial cutaway side views for describing a blowbag printing process according to the first embodiment of the present invention; FIG. 6 is a perspective view of one example of an apparatus used in the blowbag manufacturing method of a second embodiment of the present invention; FIG. 7 and FIG. 8 are partial cutaway side views of the apparatus, for describing a blowbag printing process according to the second embodiment; and FIG. 9 is a side elevational view describing a conventional printing method. BEST MODE FOR CARRYING OUT THE INVENTION The following is a description of the first embodiment of the blowbag manufacturing method of the present invention, and with reference to FIGS. 1 through 5. FIGS. 1 and 2 show examples of pharmaceutical liquid containers which are examples of blowbags manufactured by the blowbag manufacturing method of one embodiment of the present invention. These pharmaceutical containers are configured with a sectional shape having a body portion (See FIG. 2) formed from flat opposing walls formed with relatively large radii of curvatures R 1 , R 2 , an opening 2, a suspension hole 4 and a suspension fitting 3. This pharmaceutical liquid container is blowmolded from a thermoplastic material. More specifically, it is molded from a thermoplastic material such as linear low-density polyethylene, low-density polyethylene, high-density polyethylene, polypropylene, ethylene-polypropylene copolymer, polyvinyl chloride, ethylene vinyl acetate copolymer, thermoplastic elastomers (olefins, polyesters, polyamides, polyurethanes, styrenes) and the like and which have a ratio of bending elasticity of between 500 - 10000 kg/cm 2 . The surface of the body portion 1 of the pharmaceutical liquid container is printed with a display portion 5 that indicates the contents and the like therein. The blowbag manufacturing method according to the present invention includes a process for the blow molding of the pharmaceutical liquid container as described above, and a process for printing the display 5 for the contents and the like, to the surface of the body portion 1 of the pharmaceutical liquid container which has been blowmolded. FIG. 3 shows one example of an apparatus used in the blowbag manufacturing method of the first embodiment of the present invention. This apparatus comprises a pressing jig 6 and a transfer roller 7 for printing. The area of the pressing surface 8 of the pressing jig 6 is smaller than the surface of projection of the body portion 1 and is a flat surface narrower than the body portion 1, but is formed larger than the portion to be printed (display 5). In addition, the edge 9 of the pressing surface 8 is an inclined surface. As shown in FIG. 4, a pharmaceutical liquid container from the blow molding process has the surfaces of the body portion 1 on the pressing surface 8 of the pressing jig 6 made to correspond with each other and the suspension fitting 3 is fixed to the suspension fitting fixing portion 10 and the opening portion 2 is fixed to the opening fixing portion 11. As shown in FIG. 5, if the pressing jig 6 is pressed in the direction of pressing (the direction perpendicular to the surface of the body portion 1) when there is this status, the body portion 1 of the container becomes a status where the opposing surfaces are in close contact with each other and are fixed on the pressing surface 8 of the pressing jig 6. Then, if the transfer roller 7 for printing is pressed and rolled in the direction shown by the arrow, to one of the surfaces of the body portion 1, the contents of printing on the outer peripheral surface of the transfer roller 7 for printing are printed to the print display (See FIG. 1) on the body portion 1. After printing, ultraviolet light (UV) is irradiated to the print surface of the container and the printing is dried. Moreover, in this printing process described above, the opening fixing portion 11 is made a suction cup 12 such as that shown in the figure, and if the air inside the container is forcedly evacuated, the container quickly becomes a negative pressure and so it is possible for the opposing walls of the body portion 1 to be brought into close contact quickly and for there to be complete airtightness. As a result, the accuracy of printing is improved and it is possible to perform the printing of fine and complex printing to the surface of the container. In addition, according to the first embodiment, the printing which is printing performed by a transfer roller can be performed by some other transfer member such as a pad which is hemispherical in section, or by silk screening or offset printing or the like. Moreover, the flat surfaces of the body portion of the blowbag of the present invention are shown as being formed with comparatively large radii of curvatures R 1 ,R 2 but the surfaces can be surfaces which are generally flat. As has been described above, a blowbag according to the present invention is formed of a thermoplastic material which has for example a ratio of bending elasticity of between 500 - 10000 kg/cm 2 and which has a unified opening and a body portion which is flat. Because of this, one body portion can be changed to the shape of another wall of the body portion and it is possible for the opposing walls to be effectively brought into close contact and the contents liquid efficiently evacuated. Accordingly, a blowbag according to the present invention is a new type of container which has the function of combining the advantages of a sheet bag obtained by overlapping two films and adhering their edges, into close contact, and of a blowbottle obtained by blowing a plastic into a bottle shape. The following is a description of the second embodiment of the present invention, with reference to FIGS. 6 through 8. FIG. 6 shows one example of an apparatus used in the blowbag manufacturing method of a second embodiment of the present invention. This apparatus comprises a pressing jig 6 and a transfer roller 7 for printing. In the same manner as for the first embodiment, the area of the pressing surface 8 of the pressing jig 6 has a smaller area than the surface of projection of the body portion 1 of the container and is formed flat and to be narrower than the body portion 1. The edge 9 of the pressing surface 8 is an inclined surface. There is also a frame member 13 which is arranged so that it corresponds to the side surface of the pressing surface 8 from above in the process where the pressing jig 6 is pressed. The frame member 13 can be any member which has the action described above, and need not be of the same shape. As shown in FIG. 7, a pharmaceutical liquid container manufactured by the blow-molding process has one of the surfaces of the body portion 1 in contact with the top of the pressing jig 6 and the suspension fitting 3 of the body portion 1 fixed to the suspension fitting fixing portion 10 and the opening portion 2 fixed to the opening fixing portion 11. And the frame member 13 is situated above the body portion. As shown in FIG. 8, when there is this status, the pressing jig 6 is pressed to the body portion 1 and when the frame member 13 is pressed at the same time in this process, the body portion 1 of the pharmaceutical liquid container becomes the status where its opposing walls are brought into close contact and are sandwiched between the frame member 13 and the top of the pressing surface 8 of the pressing jig 6 and are securely fixed. Then, if the transfer roller 7 for printing is pressed and rolled against the surface of the body portion 1, the contents of printing on the outer peripheral surface of the transfer roller 7 for printing are transferred and printed to the body portion 1. In this printing process, the body portion 1 is securely fixed, and it is possible to have highly accurate printing since there is no slippage. After printing, ultraviolet light (UV) is irradiated to the print surface of the container and the printing is dried. The blowbag manufacturing method according to the present invention blowmolds a blowbag having a body portion with opposing walls which are flat in section and an opening portion connected to the body portion, and for example, made of a thermoplastic material having a ratio of bending elasticity of between 500 - 10000 kg/cm 2 , and supports flat surfaces of the blowmolded blowbag body portion by a pressing surface of a pressing jig having an area smaller than the flat surfaces or the flat surfaces of its opposing walls are brought into close contact, in the process of pressing the pressing jig, by a member corresponding to a side surface of the pressing surface pressed from above and required items are printed to a surface of the body portion in close contact. Because of this, it is possible for opposing walls of a body portion to be completely brought into close contact and for slippage between opposing walls of a body portion in this status of close contact to be completely prevented, and for it to be possible to implement high-accuracy printing to the body portion even if there is a blowbag (flexible container) made of a thermoplastic material. INDUSTRIAL APPLICABILITY As has been described above, the blowbag manufacturing method of the present invention is suitable for printing information relating to the contents and the like to a blowbag (flexible container) made of a thermoplastic material and which is used to contain pharmaceuticals, foodstuffs, cosmetics and the like.

Claims: A blowbag manufacturing method, comprising the steps of blow molding a thermoplastic material into a blowbag having a body portion (1) with opposing walls which are flat in section and an opening portion (2) connected to said body portion (1), supporting opposing flat surfaces of said body portion (1) by a pressing surface (8) of a pressing jig (6) having an area smaller than said flat surfaces in such a manner that said flat surfaces are in close contact with each other, and printing (7) required items to one of said flat surfaces of said body portion (1) while said flat surfaces are held in close contact with each other, characterized in that said step of supporting is performed by a means (10, 11; 13) for spanning said opposing flat surfaces of said body portion (1) over said pressing surface (8) of said pressing jig (6) in such a manner that during the step of printing said means (10, 11; 13) for spanning is positioned below the upper level of said pressing surface (8) of said pressing jig(6). The method of claim 1 wherein said means for spanning comprises a frame member (13) having a shape corresponding to a side surface (9) of said pressing surface (8) of said pressing jig (6). The method of claim 1 or 2 wherein said means for spanning comprises a fixing member (10) fixed to a suspension fitting (3) of said blowbag and a fixing member (11) fixed to the opening portion (2) of said blowbag. The method of any one of the preceding claims wherein the bringing of said flat surfaces into close contact with each other is supported by evacuating (12) the blowbag through its opening portion (2). The method of any one of the preceding claims wherein a transfer roller (7) is used for printing. The method of any one of the preceding claims wherein a pad which is hemispherical in section is used for printing. An apparatus used in the blowbag manufacturing method according to any one of the preceding claims, said apparatus comprising a pressure jig (6) having a pressure surface (8) and a printing means (7), characterized by a means (10, 11; 13) being displaceable with respect to the pressing jig (6) so as to be relatively movable from above below the pressing surface (8) of said pressing jig (6). The apparatus of claim 7 wherein said means (10,11;13) being displaceable comprises a frame member (13) having a shape corresponding to a side surface (9) of the pressing surface (8) of said pressing jig (6) and being relatively movable from above around the pressing jig (6). The apparatus of claim 7 or 8 wherein said means (10,11; 13) being displaceable comprises a fixing member (10) fixable to a suspension fitting (3) of said blowbag and a fixing member (11) fixable to the opening portion (2) of said blowbag. The apparatus of claim 9 wherein said opening portion fixing member (11) is a suction cup (12).

Inventors: KOIKE YOSHIO, MATSUMOTO KAZUYA, SAITO HISATOSHI, KOIKE, YOSHIO, MATSUMOTO, KAZUYA, SAITO, HISATOSHI
Applicants: KYORAKU CO LTD, Q P CORP, KYORAKU CO., LTD., Q.P. CORPORATION
Application year: 1991
Main classification: B29C49
IPC codes: B41F17, B41M1, B29D22, B29C49