Inner bag and its manufacturing method

Abstract

To provide an inner bag that can be easily manufactured without the need for jigs or other equipment and without requiring skilled workers, that makes full use of the can's volume for storage, and that is resistant to damage from external impacts. [Solution] The interior bag 7 is characterized by having flexibility throughout, a lower welded portion 4 formed by welding the peripheral portion of a circular bottom plate 3 to a welded piece 2 formed by folding a certain width portion of the lower end of a cylindrical body 1 inward, a straight upper welded portion 6 formed by bringing together a certain width portion of the upper end of the cylindrical body 1 and sealing it, and a cylindrical opening 5 provided near the upper end.

Description

Technical Field

[0001] The present invention relates to a flexible inner bag to be housed inside a sealed rigid can body such as a drum can, and more specifically, relates to a structure of the inner bag that allows a sufficient storage capacity for the contents stored in the inner bag, can absorb shocks applied during storage or transportation, and further reduces manufacturing costs.

Background Art

[0002] For example, synthetic resin bags are used as flexible inner containers that are mounted inside can bodies such as shape-retaining drum cans, store various liquids and powders therein, and store and transport these materials. The use of these inner bags prevents the stored contents from directly contacting the inner wall of the can body. Therefore, after taking out the stored contents, if the inner bag is removed from the can body, the inner wall of the can body is not contaminated by the stored contents, and by mounting another inner bag again without cleaning the inside of the used can body, other types of stored contents can be continuously stored as they are.

[0003] In industries that use these inner bags, multilayer ceramic capacitor manufacturers and adhesive / adhesive processing manufacturers use them as containers for transferring raw materials during manufacturing processes to save the trouble of cleaning containers, and manufacturers of paints, inks and the like use them as containers to save the trouble of cleaning paints, inks and the like when reusing containers during manufacturing processes.

[0004] In addition, when the enclosed substance is, for example, an organic solvent, the container material made of blended polyethylene resin is affected by the organic solvent, so inner bags made of films that contribute to reducing process work by eliminating cleaning work for containers during liquid change operations are used, or anti-static measures are required when handling organic solvents, and inner bags made of films of materials that achieve both organic solvent resistance and anti-static functions are sometimes used.

[0005] As shown in Figure 6, the drums in which the inner bags are stored are mainly made of steel, stainless steel, or resin, and come in several standard sizes. In a typical drum (drum body 20), two rings 22 are provided around a cylindrical body plate 21, the lower end is closed with a disc-shaped base plate (not shown), and the upper end is provided with a top plate 23 of the drum body. This top plate 23 of the drum body is provided with a large plug 24 as an inlet for filling with stored items and a small plug 25 as a ventilation opening.

[0006] As long as the inner bag to be stored in the can body 20 is cylindrical in shape and has the same dimensions as the can body 20, the inner bag will fit snugly inside the can and be tightly pressed against the inner wall of the can. In this way, the contents to be stored in the inner bag can be used to utilize the entire capacity of the can body 20, making efficient use of the can body 20's size.

[0007] On the other hand, if the shape and size of the inner bag do not match the can body 20, for example, if the inner bag is too small compared to the can body, a gap will be created between the can body and the inner bag, resulting in a disadvantage where the capacity of the stored contents is less than that of the can body. In addition, the inner bag will not be stable inside the can and will move around, and during transport of the can, vibrations may cause the inner bag to move, and in the worst case, the inner bag may hit the inner wall of the can and break, causing the stored contents to leak out.

[0008] Furthermore, if the inner bag is too large compared to the can, or if the shape of the inner bag differs from the cylindrical shape of the can, the inner bag will wrinkle inside the can and protrude inward. In this case, too, the storage capacity of the contents will be less than that of the can.

[0009] Therefore, ideally, the inner bag should also be formed in the shape of a cylindrical body of the same size as the can body. Such an inner bag is formed by creating a cylindrical body of appropriate size from a long, cylindrical shape made from a thermoplastic synthetic resin sheet using an insulation method, and then welding the openings at both ends of the cylindrical body to a circular bottom plate and top plate, also made from a thermoplastic synthetic resin sheet, to form a cylindrical inner bag with its upper and lower ends closed (see, for example, Patent Document 1).

[0010] When attaching these inner bags to a drum or other container 20 as shown in Figure 6, first remove the top plate 23 to open the top, then drop the bottom plate of the inner bag into the bottom of the container, and then inflate the inner bag by blowing air into it through the opening of the inner bag or by any other appropriate method so that the inner bag is in close contact with the inner wall of the container. After that, align the large stopper 24 of the top plate 23 with the opening of the inner bag and close the container 20 with the top plate 23.

[0011] Incidentally, one method for creating these top and bottom sealed cylindrical inner bags involves welding disc-shaped bottom plates or top plates to the top and bottom ends of a cylindrical body. In this case, as shown in Figure 2, a circular table-shaped trowel base 10, which is approximately the same shape as the bottom plate 3 (or top plate), is passed through the cylindrical body 1, and a certain width portion of the end of the cylindrical body that extends from the trowel base is folded back onto the trowel base 10 to form a welded piece 2. The bottom plate 3 is then placed on top of the trowel base 10, and the overlapping surfaces of the welded piece 2 and the periphery of the bottom plate 3 are heated with a trowel to melt and bond them together.

[0012] Although not shown in the diagram, the base plate 3 may be placed on the trowel base 10 first, and then the end of the cylindrical body 1 may be folded over onto the base plate 3 with the welding piece 2 facing upwards before welding.

[0013] Various methods and apparatuses have been proposed for easily manufacturing such cylindrical inner bags, making it possible to produce cylindrical inner bags of consistent quality (see, for example, Patent Document 2). [Prior art documents] [Patent Documents]

[0014] [Patent Document 1] Japanese Patent Publication No. 10-310173 (see Figure 1) [Patent Document 2] Patent No. 3817714 [Overview of the project] [Problems that the invention aims to solve]

[0015] However, after sealing one end of the cylindrical body 1 with the bottom plate 3 (or top plate), attaching the top plate or bottom plate to the other end in the same way is difficult because of the support column 11 that supports the trowel base 10. This makes it difficult to position the other end of the cylindrical body 1 protruding above the trowel base 10 through the already attached bottom plate 3, and thus it is difficult to weld the remaining unsealed end of the cylindrical body 1 with the top plate or the like.

[0016] As a solution, one idea has been proposed to seal both open ends of the cylindrical body 1 with circular bottom and top plates using special equipment and jigs. However, this method cannot be manufactured using only conventional trowel bases, and it has the problem of being expensive due to the cost of special equipment and jigs, the labor involved in manufacturing, and the need for skilled workers.

[0017] Furthermore, a wide variety of materials such as nylon and polyethylene are used for the inner bags, and the material is selected according to the intended use of the inner bag. In some cases, it is possible to combine multiple different materials to combine the advantages of each material. In such cases, it is conceivable to create a multi-layered structure by stacking multiple cylindrical bodies for the cylindrical body, or a multi-layered structure by stacking multiple bottom plates or top plates.

[0018] In the case of the multi-layered structure described above, there are multiple welded pieces in the cylindrical body, and depending on whether the bottom plate or top plate is placed on either the top or bottom of the multiple welded pieces when folded, or whether the bottom plate or top plate is sandwiched between the multiple welded pieces, or even in the case of the multi-layered bottom plate or top plate, whether it is placed on the trowel stand in its stacked state or whether welded pieces are sandwiched in between, a wide variety of welded joint structures can be created. This requires skilled work to set up according to the welded structure, making the manufacturing process more difficult.

[0019] Incidentally, while the cylindrical inner bag, which is the same shape as the can body, has the advantage of not causing wrinkles or other damage during storage and allowing the entire internal capacity of the can to be used, as mentioned above, when the can is subjected to impacts such as dropping or strong vibrations during storage or transport, the impact is directly transmitted to the contents through the inner bag. If the inner bag inside the can is full of contents, there is no way for the impact to escape, and the explosive, violent expansion and movement of the contents due to the impact can damage the inner bag from the inside, causing the contents to leak out.

[0020] One solution used was to intentionally create wrinkles in the inner bag and then store it in the outer container, such as a can, while maintaining the wrinkles with adhesive tape. This would cause the inner bag to expand momentarily when the can is dropped or subjected to strong vibrations, rupturing the adhesive tape and stretching out the wrinkled areas, thereby absorbing the impact.

[0021] However, this method was time-consuming, as it involved creating wrinkles in the inner bag when attaching it to the can and then fixing those wrinkles with adhesive tape. Furthermore, the effectiveness of the impact resistance varied depending on the skill level of the worker performing the task.

[0022] This invention solves the above-mentioned problems and provides an inner bag that does not require non-welding materials or jigs during manufacturing, can be easily manufactured without requiring skilled labor, allows for full utilization of the can's volume for storage when storing items, and is resistant to damage caused by external impacts during storage and transport, as well as a method for manufacturing the same. [Means for solving the problem]

[0023] To achieve the above objective, the invention of claim 1 is an interior bag characterized in that the entire bag is flexible, a portion of a certain width at the lower end of a cylindrical body is folded inward to form a welded piece, the periphery of a circular bottom plate is welded to this piece to seal the bag, a portion of a certain width at the upper end of the cylindrical body is brought together and sealed by a straight upper weld, and a cylindrical opening is provided near the upper end.

[0024] Further, the invention of Claim 2 adopts a configuration characterized in that, in the inner bag described in Claim 1 above, the tubular body portion has a multilayer structure formed by stacking a plurality of tubular bodies of the same size.

[0025] Further, the invention of Claim 3 adopts a configuration characterized in that, in the inner bag described in Claim 1 or 2 above, the bottom plate has a multilayer structure using a plurality of circular plates of the same size.

[0026] Further, the invention of Claim 4 is a method for manufacturing an inner bag that is entirely flexible, in which a lower welded portion is formed and sealed by welding the peripheral portion of a circular bottom plate to a welding piece formed by bending a portion of a fixed width at the lower end of the tubular body portion inward, a linear upper welded portion is formed and sealed by opposing portions of a fixed width at the upper end of the tubular body portion, and a tube opening 5 is provided near the upper end portion, the method comprising: (1) a step of overlapping, on an iron stand having the same shape as the bottom plate, a welding piece formed by bending a portion of a fixed width at one end of the tubular body portion arranged to surround the iron stand onto the inner iron stand, and the periphery of the bottom plate, and forming a lower welded portion by heat welding; (2) a step of aligning the other end of the tubular body portion with the bottom plate welded to one end in a straight line, and then forming an upper welded portion by heat welding; The method for manufacturing an inner bag is characterized by consisting of the above steps.

[0027] The invention of Claim 5 adopts a configuration characterized in that, in the method for manufacturing an inner bag described in Claim 4 above, one or both of the tubular body portion and the bottom plate have a multilayer structure using a plurality of sheets, and the welding piece of the tubular body portion and the periphery of the bottom plate are stacked in any order on the iron stand before the lower welded portion is formed. Effects of the Invention

[0028] As described above, with the inner bag of this invention, the lower end of the cylindrical body maintains its cylindrical shape due to the presence of the bottom plate and fits snugly into the cylindrical outer can body from the bottom plate, and the upper end of the cylindrical body has a straight upper welded portion that is pressed into the can body and wrinkled, but the contents are stored sequentially from the bottom where there are fewer wrinkles in the inner bag due to weight, and hardly any contents are stored in the wrinkled straight upper welded portion, so the effect of wrinkles on the reduction of contents is small.

[0029] Furthermore, if the can is subjected to a strong impact, the contents inside will also be affected. However, the wrinkles that form at the top edge of the inner bag will spread out, providing an escape route for the contents to expand violently and move explosively due to the impact, thereby absorbing the impact on the inner bag and preventing damage to the inner bag.

[0030] Furthermore, since the lower end of the inner bag is sealed with a circular bottom plate and the upper end is sealed with a straight upper weld, after welding the cylindrical body and bottom plate using a circular iron base during manufacturing, the inner bag can be obtained simply by welding the upper end of the cylindrical body in a straight line without being restricted by the presence of the bottom plate. Therefore, jigs and other equipment are not required for manufacturing, and it can be manufactured easily without requiring skilled workers, contributing to a reduction in manufacturing costs.

[0031] Furthermore, when welding the bottom plate, it is only necessary to overlap the welding piece formed by bending the end of the cylindrical body on the top surface of the soldering iron stand with the perimeter of the bottom plate and weld them together. This not only makes manufacturing easy, but even when using a multi-layered cylindrical body and bottom plate, the order in which the welding piece and bottom plate are overlapped on the soldering iron stand can be freely selected, making it easy to manufacture multi-layered inner bags using various materials.

[0032] Furthermore, since it becomes easy to manufacture multi-layered inner bags made of various materials, for example, by creating a multi-layered structure of a film with high resistance to organic solvents and a film with antistatic properties, it becomes possible to obtain an inner bag that combines both resistance to organic solvents and antistatic properties, thus enabling the creation of multi-functional inner bags at low cost. [Brief explanation of the drawing]

[0033] [Figure 1] (A), (B), and (C) are perspective views showing the inner bag of this invention in order of manufacture. [Figure 2] (A) and (B) are enlarged perspective views of a part of the process for manufacturing the inner bag of this invention. [Figure 3] (A) and (B) are perspective views showing the procedure for attaching the inner bag of this invention to a can. [Figure 4] This is a perspective view of the inner bag of this invention when it is attached to a can. [Figure 5] (A) and (B) are partially enlarged front cross-sectional views showing examples of the manufacturing of the inner bag of this invention. [Figure 6] This is a perspective view of the drum used in this invention. [Modes for carrying out the invention]

[0034] The embodiments of this invention will be described below with reference to the illustrations. Figure 1 shows the manufacturing process of the inner bag used in the attachment method of this invention. As shown in Figure 1(A), at the lower end of the cylindrical body 1, which is made of synthetic resin and has a predetermined length, a portion of a certain width from the lower end is bent inward at a 90° angle to form a welded piece 2.

[0035] The formation of the welded piece 2 is carried out by a conventionally known method. For example, as shown in Figure 2(A), when the cylindrical body 1 is expanded into a cylindrical shape, the lower end of the cylindrical body 1 is placed on a circular table-shaped trowel base 10 with a diameter approximately the same as the diameter of the cylindrical body 1 through which the inside of the cylindrical body 1 passes, with the lower end of the cylindrical body 1 facing upwards. The upper end of the cylindrical body 1 is made to protrude a certain width above the upper surface of the trowel base 10, and this protruding portion is tilted onto the upper surface of the trowel base 10, thereby forming the welded piece 2 of the cylindrical body 2 along the upper surface of the trowel base 10, as shown in Figure 2(B).

[0036] Next, as also shown in Figure 2(B), the peripheral portion of the disc-shaped bottom plate 3, which is approximately the same shape as the trowel base 10, is placed over the welding piece 2 on the trowel base 10. Then, the overlapping portions of the welding piece 2 and the peripheral portions of the bottom plate 3 are welded together using a known heating method to form the lower welded portion 4, thereby sealing one side of the cylindrical body portion 1 (the side that becomes the lower end of the inner bag) (see Figure 1(B)).

[0037] Next, the cylindrical body 1 is removed from the ironing base 10, a hole is made slightly below the other end of the cylindrical body 1 (the end that will become the upper end of the inner bag), and a through-hole 5 is welded in place by known means to form the opening 5. Furthermore, the end of the cylindrical body 1 with the opening 5 is aligned in a straight line as shown in Figure 1(C), and then welded in place by known means to form the upper welded portion 6. This seals the upper end of the cylindrical body 1 with the straight upper welded portion 6, and closes the lower end with the bottom plate 3 which is bonded around the perimeter by the lower welded portion 4, thus forming a closed inner bag 7.

[0038] It goes without saying that, similar to the joint structure of the bottom plate of conventional inner bags, the bottom plate 3 may be placed on the trowel base 10 first, and then the end of the cylindrical body 1 may be folded over onto the bottom plate 3 with the welding piece 2 facing upwards before welding.

[0039] These cylindrical body sections 1 and bottom plate 3 are made of flexible synthetic resin, but the material and structure are not particularly limited and can be made of known materials such as PP or PE as appropriate. In short, the cylindrical body sections 1 and bottom plate 3 can be made of any material that is flexible, can withstand some bending, and can be bonded by heat welding if necessary, and may also be made of multiple layers of different materials.

[0040] Furthermore, the opening 5 of the cylinder is flexible, but a flange is formed to engage with the large stopper of the drum described later, and it is made of a material that has a certain degree of rigidity compared to the cylindrical body 1 and the bottom plate 3.

[0041] Next, we will explain, based on Figures 3 and 4, the case in which the inner bag 7 is attached to the can body 20 as a closed-type drum body shown in Figure 6.

[0042] First, prepare an inner bag that is approximately the same size as the standardized can body 20 shown in Figure 6. In this case, prepare an inner bag 7 that is approximately the same height as the bottom plate 3 and the bottom plate (top plate 23) of the can body 20, and is approximately the same height as the can body 20.

[0043] Next, the top plate 23 of the can body 20 is opened, and the inner bag 7 is inserted through the opening. Then, the entire bottom plate 3 of the inner bag 7 is brought into contact with the bottom inner wall of the can body 20, and the cylindrical body 1 is also brought to rest against the inner wall of the can body 20.

[0044] Furthermore, at the upper end of the inner bag 7, the length of the straight upper welded portion 6 exceeds the diameter of the can body 20. Therefore, both ends of the upper welded portion 6 are folded downwards and inwards (see Figures 3(A) and 3(B)), and these folded ends of the upper welded portion 6 are pushed into the inside of the can body 20 for storage (see Figure 4).

[0045] The inner bag 7 stored in the can body 20 (drum can) has the above configuration. The lower part of the cylindrical body 1 maintains its cylindrical shape due to the presence of the bottom plate 3 and fits into the outer can body 20. The upper welded part 6 at the upper end of the cylindrical body 1 is pushed into the can body 20 and wrinkled. In this area, there are almost no stored items due to the weight, and the impact of the reduction in the volume of stored items is minimal.

[0046] Furthermore, in the event that the can body 20 is subjected to a strong impact, the wrinkles near the upper welded portion 6 of the inner bag 7 will spread out to absorb the impact on the inner bag 7, preventing damage and providing an escape route for the contents to expand and move violently due to the impact.

[0047] Figures 5(A) and 5(B) are partially enlarged front cross-sectional views showing other configuration examples of the lower welded portion 4 formed by the welded piece 2 of the cylindrical body 1 and the bottom plate 3. In this invention, the welding work of the cylindrical body 1 and the bottom plate 3 can be performed without the use of jigs or other equipment and without requiring any special skills. It can be applied even if either or both of the cylindrical body 1 and the bottom plate 3 have a multi-layered structure, and the order in which multiple cylindrical body parts 1 and bottom plates 3 are stacked on the trowel base 10 can be freely selected.

[0048] Figure 5(A) shows a cylindrical body 1 made from a single piece, with a double-layered bottom plate consisting of an outer bottom plate 3a and an inner bottom plate 3b. The cylindrical body 1 is sandwiched between the two bottom plates 3a and 3b. The manufacturing method involves first placing the bottom plate 3b on the trowel base 10, then folding a certain width of the upper end of the cylindrical body 1 over it to form a welded piece 2, and then placing the bottom plate 3a on top of that before performing the welding process to form the lower welded section 4. The order of layering is not limited to that shown in the figure and can be easily and freely selected.

[0049] Figure 5(B) shows a structure in which the cylindrical body has a double structure consisting of an outer cylindrical body 1a and an inner cylindrical body 1b, and the bottom plate has a double structure consisting of an outer bottom plate 3a and an inner bottom plate 3b, with the welded pieces 2a and 2b of the cylindrical bodies 1a and 1b sandwiched between the two bottom plates 3a and 3b. In terms of manufacturing, the bottom plate 3b is first placed on the iron base 10, then a certain width of the upper ends of the cylindrical bodies 1a and 1b is folded over to form the welded pieces 2a and 2b, and then the bottom plate 3a is placed on top of them before welding is performed to form the lower welded section 4. The order of stacking is not limited to that shown in the figure and can be easily and freely selected.

[0050] Even in the manufacture of multi-layered inner bags, the structure of these lower welded parts 4 can be freely selected and implemented without changing the ironing base 10. Therefore, by selecting the functions of the film materials to be layered, inner bags with multiple functions can be easily obtained. [Explanation of Symbols]

[0051] 1. Cylindrical body 2 welded piece 3 Bottom plate 4 Lower weld area 5 Tube opening 6 Upper weld area 7. Inner bag 10 trowel stand 11 Posts 20 can body 21 Body plate 22 Rings 23 Top plate of the can 24 Large stopper 25 small stoppers

Claims

1. An inner bag characterized by being flexible throughout, having a lower welded section formed by welding a circular bottom plate to a welded piece created by folding a certain width portion of the lower end of the cylindrical body inward, having the periphery of the circular bottom plate welded to the lower end of the cylindrical body, having a linear upper welded section formed by facing a certain width portion of the upper end of the cylindrical body, and having a cylindrical opening near the upper end.

2. The inner bag according to claim 1, characterized in that the cylindrical body has a multi-layered structure in which multiple cylindrical bodies of the same size are stacked on top of each other.

3. The inner bag according to claim 1 or 2, characterized in that the bottom plate has a multi-layered structure using multiple circular pieces of the same size.

4. A method for manufacturing an inner bag, wherein the entire structure is flexible, a lower welded portion is formed by folding a certain width portion of the lower end of a cylindrical body inward to create a welded piece, and the peripheral portion of a circular bottom plate is welded to this piece to seal it, and a straight upper welded portion is formed by bringing together a certain width portion of the upper end of the cylindrical body to seal it, and a cylindrical opening 5 is provided near the upper end, (1) A process in which a welding piece is formed by folding a certain width portion of one end of a cylindrical body, which is positioned to surround the trowel base, onto the inner trowel base, and overlapping the perimeter of the bottom plate on the trowel base and welding by heating, thereby forming the lower welded portion. (2) A step of forming the upper welded part by welding the bottom plate to one end of a cylindrical body, aligning the other end in a straight line, and then welding it by heating. A method for manufacturing an inner bag, characterized by comprising the above.

5. The method for manufacturing an inner bag according to claim 4 above, characterized in that one or both of the cylindrical body and the bottom plate are multi-layered structures using multiple pieces, and the welded pieces of the cylindrical body and the periphery of the bottom plate are stacked in any order on a soldering iron stand before forming the lower welded portion.

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