AU2006277421B2

AU2006277421B2 - Sealed container

Info

Publication number: AU2006277421B2
Application number: AU2006277421A
Authority: AU
Inventors: Masaki Nakaya
Original assignee: Kirin Brewery Co Ltd
Current assignee: Kirin Brewery Co Ltd
Priority date: 2005-08-05
Filing date: 2006-07-28
Publication date: 2011-07-14
Anticipated expiration: 2026-07-28
Also published as: RU2381160C2; CN100594164C; WO2007018054A1; KR101248725B1; RU2008108522A; CN101238041A; AU2006277421A1; JP2007039115A; JP4833608B2; KR20080034911A

Abstract

A sealed container such as beverage and food containers having lids sealed by laser beam welding and thermal fusing to impart high applicability to impurities, increase sealability, and increase a joining strength between a container body and a lid. The sealed container comprises the container body (1) having a mouth part (9) and the lid (3) causing a deformation therein when it closes the mouth part (9), producing a fitted portion (4) forming a seam in a pressurized state on the container body (1) by a strain stress, and formed of a plastic material. The fitted portion (4) is thermally fused.

Description

DESCRIPTION TITLE OF THE INVENTION SEALED CONTAINER TECHNICAL FIELD (0001] The present invention is related to a sealed container in which a lid fitted to a mouth portion of a container body is sealed by thermal fusion, and is related in particular to the structure of the mouth portion and the lid. PRIOR ART TECHNOLOGY [0002] As for sealed containers, such as beverage containers for example, various containers such as bottles, cans, plastic containers and the like are known. In recent years, cans and plastic containers have been widely used from the viewpoint of convenience such as the quality of the handling performance thereof and the like. [0003] With regard to plastic containers, it is difficult to carry out a seaming process, and plastic containers which are sealed by carrying out seaming like that for beverage metal can containers are not distributed. In plastic containers, the most distributed containers are PET 1 (polyethylene terephthalate) bottles. In PET bottles, a method in which a cap is screwed on a bottle mouth portion is used as a sealing method. However, this cap forms a main cause of large cost increases in the whole container. 5 Furthermore, because the cap is mainly made of PP (polypropylene), it becomes a hindrance to recycling. [0004] In recent years, can containers made of metal, which have a bottle shape using a method in which a cap is 10 screwed on the bottle mouth portion in the same way as for PET bottles, have also been distributed. [0005] Incidentally, with metal cans as a subject, sealing technologies in which the sealing of cans is carried out by 15 laser welding have been disclosed (e.g., see Patent Documents 1 - 3). [0006] Patent Document 1: International Publication No. W002/42196 A2 20 Patent Document 2: Japanese Laid-Open Patent Publication No. SHO 63-194885 Patent Document 3: Japanese Laid-Open Patent Publication No. SHO 61-289932 [0007] 25 In the case where the sealing of a sealed container such as a beverage/food container or the like is tried by thermal fusion, such as laser welding, there are many cases 2 where fusion needs to be carried out in a state where a liquid (e.g., splash water on the apparatus) from the surrounding environment or contents get between the surfaces to be fused at the time of sealing. At this time, 5 the fusion conditions change. After this kind of change to the fusion conditions occurs, the property that the suitable condition range is wide is expressed as the foreign material adaptability is high. Then, in the case where sealing is tried by laser welding, the fusion 10 conditions that obtained the foreign material adaptability up to this point are not known. Further, there is no knowledge at all about what the structure of the container, and in particular what the structure of the mouth portion and the lid should be in order to raise the foreign 15 material adaptability. [0008] The present inventor discovered that in the case where, for example, a PET bottle is sealed by laser welding, when a general laser spot is irradiated and 20 heating and fusing at the fusion starting point is started, the foreign materials of the fusion surface move in directions away from the fusion starting point on the fusion surface. As a result, when fusion is completed after one cycle of laser irradiation, a noticeable 25 polarization occurs on the fusion surface area, and this produces a bad effect on the sealability and the bond strength between the container body and the lid. Further, 3 foreign materials move by also being pushed out from the fusion surface area by the pressure generated by heating and fusing. As a result, it becomes possible to essentially achieve a completely elimination of foreign 5 materials from the fusion surface, but under these circumstances because a certain amount of heat is taken away from the fusion surface by the foreign materials, output adjustment of the laser becomes necessary. [0009] 10 Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the 15 present invention as it existed before the priority date of each claim of this application. [0009A] Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be 20 understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. 25 Summary of the Invention [0010] From a diligent examination of the problem described 4 above, the present inventor ascertained that (1) fixing the part to be fused so that foreign materials do not move to another fusion part during fusing, (2) forming the structure of the place where fusion is carried out in a way 5 that makes it possible for foreign materials to move outside the fusion part during fusing, and (3) carrying out laser irradiation that takes into account the quantity of heat taken away by the foreign materials are important in the sealing of the container, discovered a container having 10 a mouth portion and lid structure that reflects these, and discovered a suitable laser irradiation method. According to a first aspect of the invention, there is provided a sealed container including a container body having a mouth portion, and a lid formed from a plastic 15 material which creates a strain in itself when said mouth portion is closed, which creates a closely attached part in an applied pressure state against said container body by stress that relieves said strain, and wherein said closely attached part forms a sealed site, and is characterized by 20 the fact that said closely attached part is thermally fused. An annular rib is provided on the outer wall of said mouth portion parallel to an edge of said mouth portion, an annular ring which forms a closely attached part with said rib is provided on an edge of said lid, an 25 annular protrusion or concavity is provided on the outer wall of said mouth portion closer to the edge side of said mouth portion than said rib, and an annular concavity or 5 protrusion is provided on the inner wall of said lid at a position where the space with the ring provided on the edge of said lid forms a space that is slightly longer than the space between said annular protrusion or concavity and said 5 rib provided on said mouth portion, and wherein said closely attached part of said rib and said ring is thermally fused. [0011] When the lid is fitted to the container body, because 10 the closely attached part makes contact in an applied pressure state, foreign materials do not enter the closely attached part. In an embodiment of the invention,, because the closely attached part can be seen from above the container without obstruction, by moving the laser down 15 from above and carrying out irradiation, it is possible to carry out fusion. Accordingly, the laser irradiation apparatus can be simplified. [0012] According to a second aspect of the invention, there 20 is provided a sealed container comprising: a container body having a mouth portion; and a lid formed from a plastic material which creates a strain in itself when said mouth portion is closed, which creates a closely attached part in an applied pressure state against said container 25 body by stress that acts to relieve said strain, wherein said closely attached part forms a sealed site, and wherein 6 said closely attached part is thermally fused, wherein a contact surface of the inner wall surface of said lid and an edge of said mouth portion is provided, an annular protrusion or concavity is provided on the outer wall of 5 said mouth portion parallel to the edge of said mouth portion, and an annular concavity or protrusion is provided on the inner wall of said lid at a position where the space with said contact surface forms a space that is slightly shorter than the space between the edge of said mouth 10 portion and the annular protrusion or concavity provided on said mouth portion, and wherein said closely attached part of the annular protrusion or concavity provided on the outer wall of said mouth portion and the annular concavity or protrusion provided on the inner wall of said lid is 15 thermally fused. [0013] According to a third aspect of the present invention, there is provided a sealed container comprising: a container body having a mouth portion; and a lid formed 20 from a plastic material which creates a strain in itself when said mouth portion is closed, which creates a closely attached part in an applied pressure state against said container body by stress that acts to relieve said strain, wherein said closely attached part forms a sealed site, and 25 wherein said closely attached part is thermally fused, wherein said lid has a bent portion which sandwiches the 7 inside and outside surfaces of the edge of said mouth portion, and the closely attached part of said bent part and said container body is thermally fused. [0014] 5 Preferably a contact surface of the inner wall surface of said lid and an edge of said mouth portion is provided, and said contact surface is thermally fused. This makes it possible to improve the fusion strength of the lid. [0015] 10 After unsealing, when said lid is fitted again on the mouth portion of said container body, preferably said container body and said lid are bonded together at said closely attached part to the extent that the contents do not spill. Resealability of the container is obtained. 15 [0016] Preferably the distance between the thermally fused said closely attached part and the edge of said lid is 10 mm or less, and the inner wall surface adjacent to the edge of said lid and the outer wall surface of said container 20 body are separated. This makes it possible to eliminate liquid that wets the periphery of the closely attached part during fusing. [0017] Preferably said lid and said container body are formed 25 from a plastic resin. [0018] 8 Preferably said closely attached part is thermally fused by a laser welding method. The boundary between the fusion part and the non-fusion part is distinct, and highly precise fusion can be carried out. 5 [0019] Preferably said closely attached part is formed from a material that absorbs laser light, or said closely attached part is coated with a paint that absorbs laser light, or a body formed from a material that absorbs laser light is 10 arranged at said closely attached part. This makes it possible to carry out fusion with laser light having a small energy density. [0020] When thermal fusion is carried out by a laser welding 15 method, preferably said lid and said container body are formed from polyethylene terephthalate. [0021] By devising a structure of a mouth portion and a lid, the sealed container according to embodiments of the 20 present invention has high foreign material adaptability. In this way, by thermal fusion of a laser welding method or the like, it is possible to raise the sealability, and form a state in which the bond strength between the container body and the 9 lid is high. BRIEF DESCRIPTION OF THE DRAWINGS [0022] Fig. 1 is a schematic drawing of a sealed container 5 according to a first embodiment, wherein (a) is a vertical cross-sectional schematic drawing of the vicinity of a mouth portion in a container body when the lid is fitted, (b) is an external schematic drawing viewed from the A direction, and (c) is a perspective 10 schematic drawing of a lid viewed from the B direction. Fig. 2 is a schematic drawing of a sealed container according to a second embodiment. Fig. 3 is a schematic drawing of a sealed container according to a third embodiment. 15 Fig. 4 is a schematic drawing of a sealed container according to a fourth embodiment. Fig. 5 is a process drawing showing one embodiment of a method of manufacturing a sealed container according to the present embodiments. 20 DESCRIPTION OF SYMBOLS [0023] 100, 200, 300, 400, sealed container 1, 61, container body 2, 16, 18, annular protrusion 25 3, 62, lid 10 4, closely attached part 5, 7, edge 6, rib 8, annular ring 9, mouth portion 10, second annular protrusion 11, 15, 17, annular concavity 12, second annular concavity 13, inner wall part of lid 14, hooking part 19, contact surface 20, bent part 21, separation part 23, force pressing rib 24, force of the inner wall surface of the lid pressing the edge 25, force of the bent part sandwiching the inside and outside surfaces of the edge 26, tab 63a, lid conveying means 63b, lid supplying means 64, lid placing means 65, laser generating means 66, closely attached part 70, defective container removing means 11 DETAILED DESCRIPTION OF THE INVENTION [0024] The present invention is described in detail below with reference to preferred embodiments, but it should not be interpreted that the present invention is limited to these descriptions. First, a sealed container according to the present embodiments will be described with reference to Fig. 1 ~ Fig. 4. Further, the same symbols are applied to the same members or same parts. [0025) The sealed container according to the present embodiment has a container body which includes a mouth portion, and a lid formed from a plastic material which creates a strain in itself when said mouth portion is closed, which creates a closely attached part in an applied pressure state against said container body by stress that relieves said strain, and wherein said closely attached part forms a sealed site, and is characterized by the fact that said closely attached part is thermally fused. For example, the lid is given a cylindrical shape which includes a top surface, the mouth portion of the container body is given a cylindrical shape, and the lid is fitted so that the mouth portion is covered from the outside. At this time, the lid may be an insertion type lid or a screw on type lid. The closely attached part of the container 12 body and the lid constantly makes contact in an applied pressure state. Further, this closely attached part is made to form a sealed site. By means of the structure described above, the contents do not spill of course, and it is possible to eliminate foreign materials such as contents and splash water from the bonding surface which is the closely attached part. Accordingly, when the closely attached part is thermally fused, because there are no foreign materials on the bonding surface, phenomena which have a bad effect on thermal fusion such as the vaporization of foreign materials and the taking away of heat produced by the laser and the like are hard to occur. Incidentally, in order for the closely attached part to constantly make contact in an applied pressure state, in the sealed container according to the present embodiment, the lid is formed from a plastic material, and when the mouth portion is closed by the lid, a strain is created in the lid itself, and the stress that relieves said strain is used as a force that applies pressure. Several embodiments of a sealed container which achieve this effect are illustrated and described below. Of course, the present invention is not to be interpreted as being limited to only these embodiments. [00261 (FIRST EMBODIMENT) 13 A schematic drawing of a sealed container according to a first embodiment is shown in Fig. 1. (a) is a vertical cross-sectional schematic drawing of the vicinity of a mouth portion in a container body when the 5 lid is fitted, (b) is an external schematic drawing viewed from the A direction, and (c) is a perspective schematic drawing of a lid viewed from the B direction. In a sealed container 100 according to the first embodiment, an annular rib 6 is provided on the outer 10 wall of a mouth portion 9 of a container body 1 parallel to an edge 5 of the mouth portion 9, an annular ring 8 which forms a closely attached part 4 with the rib 6 is provided on an edge 7 of a lid 3, an annular protrusion 2 is provided on the outer wall of the mouth portion 9 15 closer to the edge 5 side of the mouth portion than the rib 6, and an annular concavity 11 is provided in the inner wall of the lid 3 at a position where the space with the ring 8 provided on the edge 7 of the lid 3 forms a space that is slightly longer than the space between 20 the annular protrusion 2 and the rib 6 provided on the mouth portion 9. Further, the closely attached part 4 of the rib 6 and the ring 8 is thermally fused. [0027] In the sealed container 100, the lid 3 has an inner 25 diameter which is designed so that it is slightly tightened around the side wall of the mouth portion 9 at the time of 14 fitting. In this regard, it is formed so that the space between the annular concavity 11 and the ring 8 forms a space that is slightly longer than the space between the annular protrusion 2 and the rib 6 provided on the mouth portion 9. Accordingly, at the part of the lid 3 held between the annular concavity 11 and the ring 8, a strain is created and a compression stress is produced in the vertical direction when viewed in Fig. 1(a) by the tightening force of the lid 3. Because the lid 3 is formed from a plastic material, a force which pushes the ring 8 down in order to relieve this compression strain, namely, a force 23 which pushes against the rib 6 is produced. In this way, the closely attached part 4 is placed in an applied pressure state. [0028] The lid 3 is formed from a plastic material, but concretely speaking, it is formed from a plastic resin, metal or composite material of these. The metal is aluminum, steel or an alloy containing these as the main components, for example. The plastic resin is polyethylene terephthalate (PET) resin, glycol modified polyethylene terephthalate (PETG) resin, polybutylene terephthalate resin, polyethylene naphthalate resin, polyethylene resin, polypropylene (PP) resin, cycloolefin copolymer resin (COC, ring olefin copolymer), ionomer resin, poly-4 15 methylpentene-1 resin, polymethyl methacrylate resin, polystyrene resin, ethylene-vinyl alcohol copolymer resin, acrylonitrile resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyamide resin, polyamide imide resin, polyacetal resin, polycarbonate resin, polysulfone resin, or ethylene tetrafluoride, acrylonitrile-styrene resin or acrylonitrile-butadiene styrene resin, for example. Of these, PET is especially preferred. PET has actual results as a material for beverage/food containers, and in the case where fusion is carried out by a laser welding method, because there is no absorptivity for the laser, by applying a color that has absorptivity for the laser on the bonding surface of the closely attached part, it is possible to directly heat the bonding surface periphery. [0029] The container body 1 is formed from a plastic resin, a glass, a ceramic, a metal or a composite material of these. The shape thereof is preferably a bottle shape. Further, because the sealing of the container is carried out by thermal fusion, there is no need for the lid to be made thick in comparison with the container body. By forming the container body 1 and the lid 3 from a plastic resin, it is possible to bond these with a little energy. [0030] 16 Further, in the sealed container 100, a second annular protrusion 10 is provided on the outer wall of the mouth portion 9 above the protrusion 2, and a second concavity 12 is provided in the inner wall of the lid 3. In this regard, the lid 3 is formed so that the space between the second concavity 12 and the inner wall part 13 of the lid 3 that makes contact with the edge 5 becomes slightly shorter than the space between the edge 5 and the second protrusion 10. In this way, a contact surface of the edge 5 and the inner wall part 13 is formed, and a constantly applied pressure state is formed at this contact surface. Accordingly, foreign materials are also eliminated from this contact surface, the bad effects due to foreign materials disappear, and thermal fusion becomes easy. Further, the bonding strength of the container body 1 and the lid 3 is improved. [00311 Furthermore, in the sealed container 100, a tab 26 is provided in order to improve the unsealability of the lid 3. Further, a hooking part 14 is provided for the rib 6 so that the lid 3 will not fly off when internal pressure is applied in the container. If by any chance, the lid 3 is opened carelessly, the lid 3 is prevented from flying off by the hooking part 14. [0032] 17 (SECOND EMBODIMENT) A schematic drawing of a sealed container according to a second embodiment is shown in Fig. 2. A vertical cross-sectional schematic drawing of the vicinity of a 5 mouth portion in a container body when the lid is fitted is shown. In a sealed container 200 according to the second embodiment, an annular rib 6 is provided on the outer wall of a mouth portion 9 of a container body 1 parallel to an edge 5 of the mouth portion, an annular 10 ring 8 which forms a closely attached part 4 with the rib 6 is provided on an edge 7 of a lid 3, an annular concavity 15 is provided in the outer wall of the mouth portion 9 closer to edge 5 side of the mouth portion than the rib 6, and an annular protrusion 16 is provided on 15 the inner wall of the lid 3 at a position where the space with the ring 8 provided on the edge 7 of the lid 3 forms a space that is slightly longer than the space between the annular concavity 15 and the rib 6 provided on the mouth portion 9. Further, the closely attached part 4 of 20 the rib 6 and the ring 8 is thermally fused. The first embodiment and the second embodiment are different in the point that the relationship between the protrusion and the concavity is reversed. [0033] 25 In the sealed container 200, the lid 3 has an inner 18 diameter which is designed so that it is slightly tightened around the side wall of the mouth portion 9 at the time of fitting. In this regard, the lid 3 is formed so that the space between the annular protrusion 16 and the ring 8 forms a space that is slightly longer than the space between the annular concavity 15 and the rib 6. Accordingly, at the part of the lid 3 held between the annular protrusion 16 and the ring 8, a strain is created and a compression stress is produced in the vertical direction when viewed in Fig. 2 by the tightening force of the lid 3. Because the lid 3 is formed from a plastic material, a force which pushes the ring 8 down in order to relieve this compression strain, namely, a force 23 which pushes against the rib 6 is produced. In this way, the closely attached part 4 is placed in an applied pressure state. [0034] The materials of the lid 3 and the container body are the same as the case of the first embodiment. In the sealed container of the second embodiment as well, a contact surface of the inner wall surface of the lid 3 and the edge 5 of the mouth portion 9 is provided (not shown in the drawing), and the contact surface may be thermally fused. Further, a tab (not shown in the drawing) and a hooking part (not shown in the drawing) may be provided. 19 [0035] (THIRD EMBODIMENT) A schematic drawing of a sealed container according to a third embodiment is shown in Fig. 3. A vertical 5 cross-sectional schematic drawing of the vicinity of a mouth portion in a container body when the lid is fitted is shown. In a sealed container 300 according to the third embodiment, a contact surface 19 of the inner wall surface of a lid 3 and an edge 5 of a mouth portion 9 is 10 provided, and an annular concavity 17 is provided on the outer wall of the mouth portion 9 parallel to the edge 5 of the mouth portion 9. Further, an annular protrusion 18 is provided on the inner wall surface of the lid 3. Furthermore, the annular protrusion 18 is provided on the 15 inner wall of the lid 3 at a position where the space with the contact surface 19 forms a space that is slightly shorter than the space between the edge 5 of the mouth portion 9 and the annular concavity 17 provided in the mouth portion 9. Further, the closely attached part 20 4 of the annular concavity 17 provided in the outer wall of the container body 1 and the annular protrusion 18 provided on the inner wall of the lid 3 is thermally fused. [0036] 25 In the third embodiment, the relationship between the protrusion and the concavity may be reversed to form an 20 embodiment (not shown in the drawings) which is a similar embodiment of the third embodiment in the same way as the relationship between the second embodiment and the first embodiment. [0037] In the sealed container 300, the lid 3 has an inner diameter which is designed so that it is slightly tightened around the side wall of the mouth portion 9 at the time of fitting. In this regard, the lid 3 is formed so that the space between the contact surface 19 and the annular protrusion 18 provided in the lid 3 forms a space that is slightly shorter than the space between the edge 5 of the mouth portion 9 and the annular concavity 17 provided in the mouth portion 9. Accordingly, at the part of the lid 3 held between the contact surface 19 and the annular protrusion 18, a strain is created and a tensile stress is produced in the vertical direction when viewed in Fig. 3 by the tightening force of the lid 3. Because the lid 3 is formed from a plastic material, a force which pushes the inner wall surface of the lid 3 against the edge 5 is produced in order to relieve this tensile strain, and the edge 5 makes contact with the inner wall surface of the lid 3. On the other hand, the annular protrusion 18 of the lid 3 and the annular concavity 17 of the container body 1 are bonded together, and the closely attached part 4 is placed 21 in an applied pressure state. [0038] The materials of the lid 3 and the container body 1 are the same as the case of the first embodiment. In the 5 sealed container of the third embodiment as well, the contact surface 19 may be thermally fused. Further, a tab (not shown in the drawing) and a hooking part (not shown in the drawing) may be provided. [0039] 10 (FOURTH EMBODIMENT) A schematic drawing of a sealed container according to a fourth embodiment is shown in Fig. 4. A vertical cross-sectional schematic drawing of the vicinity of a mouth portion in a container body when the lid is fitted 15 is shown. In a sealed container 400 according to the fourth embodiment, the lid 3 has a bent part 20 which sandwiches the inside and outside surfaces of the edge 5 of the mouth portion 9 of the container body 1, and the closely attached part 4 of the bent part 20 and the 20 container body 1 is thermally fused. [0040] In the sealed container 400, a strain is created by the bent part 20 sandwiching the inside and outside surfaces of the edge 5, and the closely attached part 4 25 of the bent part 20 and the container body 1 is placed in an 22 applied pressure state to relieve this strain. The symbol 25 of Fig. 4 shows the force of the bent part 20 sandwiching the inside and outside surfaces of the edge 5. [0041] The materials of the lid 3 and the container body 1 are the same as the case of the first embodiment. In the sealed container of the fourth embodiment as well, a tab (not shown in the drawing) and a hooking part (not shown in the drawing) may be provided. [0042] In the sealed container of the first ~ fourth embodiments, after unsealing, when the lid 3 is fitted again on the mouth portion 9 of the container body 1, preferably the container body 1 and the lid 3 are bonded together at the closely attached part 4 to the extent that the contents do not spill. Resealability of the container is obtained. In the embodiments described above, the closely attached part 4 forms an applied pressure state. By adjusting the thickness of the lid 3 and the size relationship between the inner diameter of the lid 3 and the external shape of the mouth portion 9 so that the applied pressure state forms a reasonable pressure, it is possible for the contents to not spill. [0043] In the sealed container of the first ~ fourth 23 embodiments, the distance between the fused closely attached part 4 and the edge 7 of the lid 3 is 10 mm or less, and preferably the inner wall surface adjacent to the edge 7 of the lid 3 and the outer wall surface of the container body 1 are separated. For example, a description will be given for the partially enlarged view C shown in Fig. 2. The distance X between the closely attached part 4 and the edge 7 of the lid 3 is set at 10 mm or less, and a separation part 21 is provided between the inner wall surface of the lid 3 and the outer wall surface of the container body 1. In the other embodiments as well, the distance X and the separation part 21 may be provided in the same way. By means of this structure, it is possible to eliminate liquid that wets the periphery of the closely attached part 4 during fusing. [0044] In the sealed container of the first - fourth embodiments, preferably the closely attached part 4 is thermally fused by a laser welding method. Compared to the case where thermal fusion is carried out with a heater as a heat source, the boundary between the fusion part and the non-fusion part is distinct, and highly precise fusion can be carried out. [0045] In the sealed container of the first - fourth 24 embodiments, the closely attached part 4 may be formed from a material that absorbs laser light, or a paint that absorbs laser light may be coated on the closely attached part 4, or a body formed from a material that absorbs laser light may be arranged at the closely attached part 4. In the case where fusion is carried out by a laser welding method, even in the case where the object being fused does not absorb laser light, by applying a color that has absorptivity for the laser light on the bonding surface of the closely attached part, it is possible to directly heat the bonding surface periphery. In order to form the closely attached part from a material that absorbs laser light, for example, a dye or a pigment is included in the plastic resin to form the container body or the lid or both of these. In order to coat the closely attached part 4 with a paint that absorbs the laser light, for example, the paint can be printed by various printing methods. As for the material that absorbs laser light arranged at the closely attached part 4, for example, the same material as either the container body or the lid is coated with a paint, or includes a dye or a pigment. By providing an absorbing part for the laser light in this way, the absorptance of the laser becomes high, and it becomes possible to carry out laser welding with a little energy. The dye or the pigment, for example, is a metal material, a 25 ceramic or an organic pigment that absorbs laser light. Preferably, the wavelength of the laser light, the laser power and the laser scanning speed are adjusted in accordance with the absorption level of the absorbing part for the laser light. [0046] Next, a method of manufacturing a sealed container according to the present embodiments will be described with reference to Fig. 5. Fig. 5 is a process drawing showing one embodiment of a method of manufacturing a sealed container according to the present embodiments. First, in step Sl, a container 61 that was filled with contents is introduced to a laser welding machine by conveying means (not shown in the drawing) such as a conveyor or the like. At this time, in the case where the contents are foaming, foam breaking is carried out, and carbon dioxide gas purging or nitrogen gas purging is carried out. [0047] Next, in step S2, a lid 62 is conveyed by lid conveying means 63a to lid supplying means 63b. The lid supplying means 63b supplies one lid 62 to the mouth of one container body 61. [0048] Next, in step S3, lid placing means 64 fits the lid 62 in the mouth portion of the container body 61. In this 26 way, the bonding surface is placed in an applied pressure state at the closely attached part of the lid and the container body. [0049] Next, in step S4, the closely attached part 66 of the container body 61 and the lid 62 is irradiated with a laser by laser generating means 65. In this regard, irradiation with the laser can be carried out in a spot shape or a linear shape, and it is possible to fuse the entire closely attached part 66 while the container 61 is rotated once around its central axis (rotation means for the container 61 are not shown in the drawing). [0050] At the time of laser irradiation, the laser intensity is preferably monitored by monitoring the laser output. Further, the irradiation position of the laser is preferably monitored by monitoring light generation or heat generation by a photosensitive sensor or a temperature sensor such as an infrared sensor or the like. The welding of plastic is preferably monitored by monitoring light generation or heat generation by a photosensitive sensor or a temperature sensor. An image sensor such as a CCD or the like may be used at the same time. [0051] The laser oscillating element installed in the laser 27 generating means 65 can be a semiconductor laser, a gas laser such as a carbon dioxide laser or the like, or a YAG laser, and the material of the container body and the lid which undergo laser welding is suitably selected in accordance with various parameters such as the laser irradiation moving speed, the irradiation spot shape and the like. The wavelength of the laser is 800 - 1000 nm, for example. In the case where a plastic container or a bottle-shaped can container is laser welded, a semiconductor laser is preferred. The energy density of the laser light irradiating the closely attached part can be 150 J per 1 cm 2 of fusion surface area. This makes it possible to complete fusion without producing thermal deformation. [0052] In this regard, in order to raise the absorptance of the laser light, a process which provides a laser light absorbing part at the closely attached part is preferably provided. Even if there are contours or undulations along the absorbing part which make mechanical contact complicated, laser welding can be carried out with good precision. This is because the laser light can constrict the irradiation spot, and the place provided with the absorbing part is mainly welded. This process may be carried out at any time before laser irradiation, and may 28 be provided before step Sl, or anywhere between step Sl, step S2 or step S3. Further, because this process is effective in the case where a material that does not have an absorption band for the laser light is welded, it is not an essential process. Namely, in the case where the bonding part absorbs laser light as in a partially colored bottle, laser welding can be carried out just by irradiation with the laser. [0053] Next, in step S5, containers having sealing defects are removed by defective container rejecting means 70. The judgment of sealing defects is preferably carried out based on the monitoring results described above and visual inspection results of an image inspecting device (not shown in the drawings). [0054] In the prior art seaming process for metal cans, it is difficult to judge whether or not a container is properly sealed at the point in time when the seaming process is actually carried out. For this reason, regardless of there being good inspection results before the start of manufacturing, in the case where sealing defects occur in the seaming process, defect is discovered only some time after the time of the actual defect occurrence. In this case, the number of containers that need to be discarded 29 and the stopping time of the industrial apparatus become very large. On the other hand, in accordance with the method of manufacturing a sealed container according to the present embodiments, because it is possible to detect in a very short time whether or not the sealing process was carried out properly, the disadvantages described above in the seaming process for metal cans do not occur. (0055] In the present invention, it is possible to apply the following welding methods in place of the laser welding method. Namely, there are cases where sealed containers are manufactured in which the closely attached part is fused by an impulse sealing method, a high frequency welding method, a vibration welding method, a spin welding method, an ultrasonic welding method, a hot gas welding method or a heat sealing method. [0056] The impulse sealing method is a method in which a strong electric current quickly flows to a ribbon heater to carry out heat welding of the closely attached part. The high frequency welding method is a welding method that depends on internal heating by the absorption of a high frequency electric current in a closely attached part having a large dielectric constant and a large dielectric dissipation factor. A film having a large dielectric 30 constant and a large dielectric dissipation factor is used. The vibration welding method is a welding method in which fusion bonding is carried out by rubbing the closely attached part in place of spin to generate heat. The spin welding method is a method in which fusion welding is carried out by frictional heat from rotating and rubbing the closely attached part. The ultrasonic welding method is a method in which the closely attached part is fusion bonded by applying ultrasonic vibration energy. The hot gas welding method is a method in which air or a gas is sent to a heated heater and then blown on the closely attached part to carry out welding. The heat sealing method is a method in which welding is carried out by pressurized heating in the state where the closely attached part is held between heating plates. Each welding method can be suitably selected and applied to fit the shape of the container. 31

Claims

1. A sealed container, comprising: a container body having a mouth portion; and a lid formed from a plastic material which creates a 5 strain in itself when said mouth portion is closed, which creates a closely attached part in an applied pressure state against said container body by stress that acts to relieve said strain, wherein said closely attached part forms a sealed site, and wherein said closely attached 10 part is thermally fused, wherein an annular rib is provided on the outer wall of said mouth portion parallel to an edge of said mouth portion, an annular ring which forms a closely attached part 15 with said rib is provided on an edge of said lid, an annular protrusion or concavity is provided on the outer wall of said mouth portion closer to the edge side of said mouth portion than said rib, and an annular concavity or protrusion is provided on 20 the inner wall of said lid at a position where the space with the ring provided on the edge of said lid forms a space that is slightly longer than the space between said annular protrusion or concavity and said rib provided on said mouth portion, and 25 wherein said closely attached part of said rib and said ring is thermally fused. 32

2. A sealed container, comprising: a container body having a mouth portion; and a lid formed from a plastic material which creates a strain in itself when said mouth portion is closed, which 5 creates a closely attached part in an applied pressure state against said container body by stress that acts to relieve said strain, wherein said closely attached part forms a sealed site, and wherein said closely attached part is thermally fused, 10 wherein a contact surface of the inner wall surface of said lid and an edge of said mouth portion is provided, an annular protrusion or concavity is provided on the outer wall of said mouth portion parallel to the edge 15 of said mouth portion, and an annular concavity or protrusion is provided on the inner wall of said lid at a position where the space with said contact surface forms a space that is slightly shorter than the space between the edge of said mouth 20 portion and the annular protrusion or concavity provided on said mouth portion, and wherein said closely attached part of the annular protrusion or concavity provided on the outer wall of said mouth portion and the annular concavity or 25 protrusion provided on the inner wall of said lid is thermally fused. 33

3. A sealed container, comprising: a container body having a mouth portion; and a lid formed from a plastic material which creates a 5 strain in itself when said mouth portion is closed, which creates a closely attached part in an applied pressure state against said container body by stress that acts to relieve said strain, wherein said closely attached part forms a sealed site, and wherein said closely attached 10 part is thermally fused, wherein said lid has a bent part which sandwiches the inside and outside surfaces of the edge of said mouth portion, and the closely attached part of said bent part and said container body is thermally fused. 15

4. The sealed container according to any one of claims 1 to 3, wherein a contact surface of the inner wall surface of said lid and an edge of said mouth portion is provided, and wherein said contact surface is thermally fused. 20

5. The sealed container according to any one of claims 1 to 4, wherein after unsealing, when said lid is fitted again on the mouth portion of said container body, said container body and said lid are bonded together at said closely attached part to the extent that the contents do 25 not spill. 34

6. The sealed container according to any one of claims 1 to 5, wherein the distance between the thermally fused said closely attached part and the edge of said lid is 10 mm or less, and the inner wall surface adjacent to the 5 edge of said lid and the outer wall surface of said container body are separated.

7. The sealed container according to any one of claims 1 to 6, wherein said lid and said container body are formed from a plastic resin. 10

8. The sealed container according to any one of claims 1 to 7, wherein said closely attached part is thermally fused by a laser welding method.

9. The sealed container according to any one of claims 1 to 8, wherein said closely attached part is formed from a 15 material that absorbs laser light, or said closely attached part is coated with a paint that absorbs laser light, or a body formed from a material that absorbs laser light is arranged at said closely attached part.

10. The sealed container according to claim 8 or claim 20 9, wherein said lid and said container body are formed from polyethylene terephthalate.

11. A sealed container substantially as hereinbefore described with reference to the accompanying drawings. 35