METHOD AND APPARATUS FOR FORMING SEAL PORTION OF LAMINATED ALUMINUM TUBE

Abstract: A synthetic resin material of an end portion (5) which protrudes from a clamp jig (9) is heated and melted, and this protruding end portion is pressed and molded to a seal portion (8) inside a press molding space defining a gap into which the synthetic resin material intrudes between an aluminum foil layer (3c) and a mold surface, thereby setting the appearance of the seal portion (8) to a desired shape and completely covering the aluminum foil layer (3c). Further, the seal strength is increased by attaining a higher density by pressing.

Description: This invention relates to a forming method for a seal portion of laminated aluminum tubes according to the preamble of claim 1. This invention also relates to an apparatus for forming a seal portion of laminated aluminum tubes according to the preamble of claim 3. In the past, a seal portion of synthetic resin made tube-type containers, the main body thereof is made of a laminated aluminum tube, is generally formed in such way that, first, an end portion, which comprises a cave and naturally opens to the air, is clamped and flattened by a clamp device. Then a projecting end portion, which is a portion protruded from the clamp device, is heated and melted by a heater. At last, the melted projecting end portion is simply pressed by a pair of sealing metal into a closed flat shape. According to the prior art described above, the sealing metal is such that it is capable of just pressing the melted projecting end portion, so that it cannot control the melted synthetic resin to flow to certain directions. Therefore, the sealing metal according to the prior art cannot form the seal portion into a desired certain shape. That is, according to the prior art, the sealing metal only presses the melted synthetic resin at the projecting end portion, so that, as shown in Fig. 8, the melted synthetic resin partly protrudes toward the side directions and produces sharp shaped barrs. Users are often bothered by such containers as the barrs scratch his/her fingers or the like and hurt them. Further, since the seal portion is formed into a final shape by being simply clamped by the sealing metal, the final shape thereof is limited to such shape as shown in Fig. 8 or the like. And, the seal portion cannot be formed into any other desired unique shape or any other useful shape which, for example, enables it to comprise a portion such as a hook for placing it on an hunger. The container according to the prior art is not satisfactory because the final shape thereof is limited. Further, according to the seal portion of a tube of the prior art, as the projecting end portion is heated to melt, an aluminum foil layer thereat partly exposes in the air. Since the projecting end portion is simply pressed and formed into a final shape, the aluminum foil layer 3c is not fully covered with the shynthetic resin. It continues to expose partially in the air as shown in Fig. 8. The exposed aluminum foil layer corrodes, and an outlook of the seal portion deteriorates, depreciating the seal resistance of the seal portion. Therefore, the object of the present invention is to resolve such problems and to form a seal portion of laminated aluminum tubes into a desired shape, to form an outlook of the seal portion into a handsome shape, and to cover the aluminum foil layer completely with the synthetic resein. This objects is solved by the characterising features by claims 1 and 3. Description of the invention In order to achieve this object, a forming method of a seal portion of laminated aluminum tubes according to the present invention comprises the following steps. First, clamp an end portion of a laminated aluminum tube into a flat shape by a pair of clamps. Second, heat and melt synthetic resin material at a projecting end portion which is a portion projected from the clamp device. Finally, press the melted projecting end portion and mold it into a desired shape of a seal portion in a press mold space. The press mold space creates an opening between an aluminum foil at the projecting end portion and the mold wall, where melted synthetic resin at the projecting end portion flows into. Prior to press and mold the projecting end portion into the seal portion, it is desired that both egde corners of the edge of the projecting end portion should be removed by either folding them inside or cutting. A forming apparatus for seal portions of laminated aluminum tubes accoring to the invention comprises a pair of clamps (clamp device), a heater and a press molding device. The clamp device clamps and flattens the end portion of a laminated aluminum tube. The heater heats and melts the synthetic resin material at the projecting end portion of the end portion. The projecting end portion is a portion being projected from the clamp device. The press molding device presses the projecting end portion while the synthetic resin material thereat is being melted and molds it into a desired shape. The press molding device may be provided with a concave jig and a convex jig. The concave jig is capable of sliding over one of the clamps of the clamp device in the directions the press molding device moves to press the end portion. The concave jig has a concave shaped molding wall, and the width thereof is similar to or a little wider than that of the projecting end portion. The convex jig is capable of sliding over the other clamp of the clamp device in the same direction as the concave jig moves. It has a convex shaped molding wall. The convex wall is inserted into the concave molding wall of the concave jig so tightly that no barrs are produced between them. The function of the invention will be described below. According to the method invention, the end portion of a tube is clamped from its front and back by a pair of clamps (a clamp device), each of which comprises a flat pressing surface, and is formed into a flat shape. Then the projecting end portion being projected out of the clamp device is heated by a heater. As the projecting end portion is heated by the heater, the synthetic resin at the projecting end portion melts but an aluminum foil layer at the same projecting end portion does not melt. Thus, the melted synthetic resin deformes and sticks around the straightned aluminum foil layer. After completion of the heating process of the projecting end portion by the heater and while the synthetic resin material at the projecting end portion is still in a melted condition, the projecting end portion is positioned into a molding space formed by a combination of a concave jig and a convex jig. By being pressed by the jigs, the projecting end portion is molded into a desired shape, and it is cooled and completed to the seal portion. Regarding the press molding of the projecting end portion into the seal portion, a desired shape of the molding space formed by a combination of the concave jig and the convex jig is arranged such that it comprises required size and shape to allow the melted synthetic resin at the projecting end portion to flow and fill an opening created between the mold wall of the jigs and the aluminum foil layer. Therefore, by simply pressing the projecting end portion by the jigs, the synthetic resin material at the projecting end portion is able to flow around the aluminum foil layer in the molding space, filling the space between the molding wall and the aluminum foil layer. As a result, the outlook shape of the seal portion is decided according to the shape of the molding space formed by the jigs, and the aluminum foil layer is totally covered by the synthetic resin. Further, the projecting end portion is pressed and molded into the seal portion in the molding space, which is a closed space, without carrying out a so-called short mold, so that the seal portion is formed as the the projecting end portion is pressed hard enough, and that the synthetic resin material at the seal portion highly improves in its density. (The short mold in this case means that synthetic resin is not provided in an adequate amount to fill a molding space, so that an aluminum foil cannot be fully covered with synthetic resin.) Therefore, the mechanical strength of the seal portion improves, and so does the adherence strength of the synthetic resin material at the seal portion. By removing both edge corners of the projecting end portion by folding or cutting them prior to seal molding the projecting end portion into the seal portion, the projecting degree of the aluminum foil layer at the edge corners are widely reduced, so that the press molding space formed by the mold jigs can be shaped more freely, and that the corners of the projecting end portion are prevented from being pressed by the molding device, which improves the safety of the forming process. Brief description of the drawings Fig. 1 shows an end portion of a laminated aluminum tube, wherein Fig. 1(a) shows a top view thereof, and Fig. 1(b) shows an elevational view thereof. Fig. 2 shows an enlarged sectional view of an example of plural layers of the tube shown in Fig. 1. Fig. 3 shows a clamping process of an end portion of a tube of a preferred embodiment according to the invention, wherein Fig. 3(a) shows a top view thereof, and Fig. 3(b) shows an elevational view thereof. Fig. 4 shows an elevational view of a heating process of a preferred embodiment according to the invention. Fig. 5 shows an elevational view of a projecting end portion right after its completion of the heating process of a preferred embodiment according to the invention. Fig. 6 shows a press mold process of a preferred embodiment according to the invention, wherein Fig. 6(a) shows a top view thereof, and Fig. 6(b) shows an elevational view thereof. Fig. 7 shows an elevational view of an outlook of a seal portion of a preferred embodiment according to the invention. Fig. 8 shows an elevational view of an outlook of a prior art seal portion. Preferred embodiment of the invention A preferred embodiment according to the invention will be described below referring to Fig. 1 to Fig. 7. Fig. 1(a) shows a top view of an aluminum lamination tube 1, and Fig. 1(b) shows an end area of the tube 1 including an end portion 4. This tube 1, as shown in Fig. 2, is composed of plural layers, which are an outer film 2 which is thicker and located outside and a laminated aluminum film 3 located inside. The laminated aluminum film 3 is composed of: (from its outer surface) a nonrigid polyethylene made outer layer 3a which is white, a nonrigid polyethylene made extrusion laminated layer 3b which has its natural color and is adhesive, an aluminum foil layer 3c of Japanese Industrial Standard product, a polyurethane made first dry laminated layer 3d, a polyethylene terephthalate made aggregate layer 3e which mechanically strengthen the laminated aluminum film 3, a polyurethane system made second dry laminated layer 3f, and a nonrigid polyethylene made inner layer 3g which structures the inner surface of the laminated aluminum film 3. By clamping the end portion 4 of the tube 1 into a flat shape by a pair of clamps (a clamp device) 9, as shown in Fig. 3, as the projecting end portion 5 projects from the clamp device 9, the projecting end portion 5 slightely opens its edge portion as shown in Fig. 3(a), and it is flattened as such that its width is almost as wide as the flattened end portion 4 as shown in Fig. 3(b). Then, the projecting end portion 5 of the tube 1 is heated mainly by heat radiation of a heater 10 from its right ahead while the projecting end portion 5 is still being clamped by the clamp device 9 until the synthetic resin material of the tube 1 melts. By this heating process by the heater 10, the synthetic resin at the projecting end portion 5 is half melted, so that it tends to draw downward and deform by an effect of the gravity. However, since the aluminum foil layer 3c still keeps its own shape, the synthetic resin at the projecting end portion 5 does not fully draw down as it tends to cohere to the foil layer 3c. Thus, as shown in Fig. 5, it only draws down a little. The heating process of the projecting end portion 5 by the heater 10 should be decided as such that time and temperature of heating the synthetic resin of the tube 1 are decided based on the nature and the structure of the resin. In general, the top edge portion of the projecting end portion 5 is heated for 8 to 10 seconds until the temperature thereof raises to 180°C to 250 °C. After completion of the heating process of the projecting end portion 5 by the heater 10, as shown in Fig. 6, the projecting end portion 5 being clamped by the clamp device 9 is secured into a press molding device 11, and it is promptely pressed and molded by the press molding device 11 into a desired shape of a seal portion 8. The press molding device 11 comprises a concave jig 13 and convex jig 12. The concave jig 13 is capable of sliding in the direction that the press molding device 11 moves to press the projecting end portion 5 above one of the clamps 9. The concave jig 13 is provided with a concave shaped molding wall facing to the projecting end portion 5. The molding wall is as wide as or slightly wider than the projecting end portion 5. The convex jig 12 is capable of sliding over the other one of the clamps 9 in the direction that the press molding device 11 moves to press the projecting end portion 5. The convex jig 12 is provided with a convex shaped molding wall which airtightly secures into the concave shaped molding wall of the concave jig 13 as such that no barrs are produced around the seal portion 8 while it is molded. In case of the preferred embodiment shown in the drawings, the molding space formed by a combination of the convex jig 12 and the concave jig 13 is arranged as wide as the flattend end portion 4, and the top surface of the molding space is arranged flat, and both corners thereof are shaped in circular arc 7. The molding space formed by the concave jig 13 is as such that its size and shape is arranged so that when the projecting end portion 5 is positioned into the molding space, there is provided an opening between the molding wall and the edge portion of the aluminum foil layer 3c of the projecting end portion 5, in which melted synthetic resin flows and remains. The aluminum foil layer 3 at the projecting end portion 5 neither flows nor deforms, so that the substantial molding space provided thereat is an opening formed between the molding wall of the press molding device 11 and the aluminum foil layer 3c. When the projecting end portion 5 is pressed, cooled and molded into the seal portion 8, the projecting end portion 5 is stressed with a force of about 30 kgf. By this, a cubic volume of the seal portion 8 becomes about 0.65∼ 0.80 times as large as that of the projecting end portion 5. To succesfully achieve this, the press molding device 11 comprises a function that the pressing stroke thereof is changeable. Time required for press molding the projecting end portion 5 into the seal portion 8 by the press molding device 11 is about 0.5 seconds. The synthetic resin at the seal portion 8 is cooled down to the temperature of 60 °C∼80°C while it is pressed and molded into the seal portion 8. After released from the press molding device 11, the seal portion 8 is further cooled down to the normal temperature by air-cooling in which it is blown with air. Fig. 7 shows a front view of an outlook of the seal portion 8 formed by the press molding device 11 which is shown in Fig. 6. The seal portion 8 does not protrude either side of the end portion 4: the edge line smoothly continues; both corners are cut so that each of them is shaped in circular arc form; and the top edge is shaped straight forward and flat. Since the substantial molding space is created between the molding wall of the press molding device 11 and the aluminum foil layer 3c at the projecting end portion 5, the aluminum foil layer 3c at the seal portion 8 is fully and completely covered by the synthetic resin. The preferred embodiment shown in Fig. 7 is formed such that prior to seal molding the projecting end portion 5 into the seal portion 8, both edge corners of the end portion 5 are shaped in edge cut 7 forms for the purpose of removing the aluminum foil layer at the same corners by folding or simply cutting them. By doing so, the edge corners of the seal portion 8 can be shaped in circular arc forms with a rather long radius. Since the edge corners of the seal portion 8 are formed in circular arc forms, the molding space can be minimized and a so-called short mold can be prevented while the seal portion 8 is formed. Although, in the preferred embodiment, the edge cutting process of the corners 6 of the projecting end portion 5 by folding or cutting them is completed prior to press molding the projecting end portion 5 into the seal portion 8, it should not be limited so. In case the cut edge 7 is formed by folding the corners 6, it should be completed when the synthetic resin at the projecting end portion 5 has lost its rigidity, that is the time right after the projecting end portion 5 is heated. While press molding the projecting end portion 5 into the seal portion 8, the synthetic resin material flows and covers the aluminum foil layer 3c. The synthetic resin forms an outlook of the seal portion 8. This synthetic resin is mainly composed of an outer film 2, an outer layer 3a made of laminated aluminum film and a laminated film 3b. The total thickness of the synthetic resin material is 75∼77% of that of the tube 1. Since the tube 1 is composed of a higher percent of synthetic resin material, the short mold will hardly occurs when press molding the projecting end portion 5 into the seal portion 8. However, in case the edge cut 7 is not formed, or the molding space created between the aluminum foil layer 3a at the projecting end portion 5 and the molding wall of the press molding device 11 is arranged larger to form a desired shape of the seal portion 8, the outer film 2 should be thickened. (It is preferred that the thickness of the outer film 2 should be limited below about 500 µ to not to diminish the sense of touch of the tube 1.) Industrial utilization The invention is structured as described above, so that it possesses the following industrial utilization. The press molding space, in which a projecting end portion is formed into a seal portion, is a desired shape of space, so that an outlook of the seal portion can be formed into a desired shape accordingly, and that a tube, which is the final product of the invention, can be shaped into a desired shape. This stablizes a product liability of the tube. The press molding space can be arranged into a desired shape, so that an outlook of the seal portion can be shaped as such that it is so smooth that it does not hitch such as users' fingers, and that a desired type of tube such as easy and safe to use can be provided. The press molding space, which forms the projecting end portion into the seal portion, can be desiredly shaped, so that an outlook of the seal portion can be formed into any desired unique shapes, and that good looking and unique shaped tubes with high product liability can be produced. The seal portion is such that an aluminum foil layer thereat is fully and assuredly covered with synthetic resin material, so that the edge of the aluminum foil layer is also rigidly covered with the synthetic resin material, and that the aluminum foil layer at the seal portion does not corrode. This provides such tube that the seal portion thereof stably keeps its rigid sealing function for a longer period of time. The seal portion is formed in the press molding space, which is a closed space, by being pressed with strong force, so that the synthetic resin at the seal portion is also pressed hard increasing its density, and that the sealing strength of the seal portion improves. This can provide such tube that the sealing quality thereof is excellent.

Claims: Method for forming seal portions (8) of laminated aluminum tubes comprising the steps of: clamping and flattening an end portion (4) of a laminated aluminum tube (1) by a clamping device (9); heating and melting an end portion (5) being projected outwardly from said clamping device (9); and pressing said outwardly projecting portion, characterized by the step of molding said projecing end portion (5) into a desired shape of the seal portion (8) in a press molding space, said press molding space being created between an aluminum foil layer (3c) at said projecting end portion (5) and a molding wall of said press molding space, wherein said press molding space comprises a free space into which melted synthetic resin at said projecting end portion (5) flows. Method for forming seal portions of laminated aluminum tubes as claimed in claim 1, wherein prior to press molding said projecting end portion (5) into said seal portion (8), each edge corner (6) of said projecting end portion (5) into a cut edge (7) is formed by either folding them inside or cutting them. Apparatus for forming seal portions of laminated aluminum tubes comprising: a clamp device (9) for clamping an end portion (4) of a laminated aluminum tube (1) and flattening said end portion (4), said clamp device (9) being composed of a pair of clamps; a heater (10) for heating a projecting end portion (5) being projected outwardly from said clamping device (9) and melting synthetic resin material at said projecting end portion (5); and a press molding device (11) for pressing and molding said projecting end portion (5), characterized in that a press molding space is provided in the press molding device between an aluminum foil layer (3c) at said projecting end portion (5) and a molding wall of said press molding space comprising a free space into which melted synthetic resin at said projecting end portion flows. Apparatus for forming seal portion of laminated aluminum tube as claimed in claim 3, wherein said press molding device (11) comprises: a concave jig (13) capable of sliding in the direction said pross molding device (11) moves to press said tube (1), and comprising its front surface against said projecting end portion (5) a concave shaped molding wall, said concave shaped molding wall is as wide as or a little wider than said projecting end portion (5); a convex jig (12) capable of sliding in the direction said pross molding device (11) moves to press said tube (1), and comprising its front surface against said projecting end portion (5) a convex shaped wall, said convex shaped molding wall so tightly secures into said concave shaped molding wall of said concave jig (13) that no barrs are produced.

Inventors: FUJITA MAMORU, FUJITA, MAMORU, FUJITA, Mamoru-Yoshino Kogyosho Co., Ltd.
Applicants: YOSHINO KOGYOSHO CO LTD, YOSHINO KOGYOSHO CO., LTD.
Application year: 1996
Main classification: B65B7
IPC codes: B29C65, B65B7, B29L23, B29L9, B29C53, B29C57