JP2009126553A - Plastic sheet molded container, and method of and device for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet molding technology for thinning a sheet while maintaining necessary rigidity. <P>SOLUTION: This plastic sheet molded container body or plastic sheet molded cover whose opening peripheral edge is formed with a rib such as a flange or a partition is provided with a Z-shaped superimposed part with a flat cross section comprising the combination of a protrusively folded part and a valley-folded part formed by folding and superimposing a plastic sheet in the width direction of the flange. In manufacturing the same, after a part of the plastic sheet is formed in a chevron shape protruding diagonally relative to the suction direction during vacuum suction for forming the protrusively folded part, the folded part is folded down by a press process for forming the superimposed part. The production device includes a fixed die, a movable die with a molding face demoldable from the protrusively folded part after a part of the plastic sheet is formed in a chevron shape protruding diagonally relative to the suction direction during vacuum suction for forming the protrusively folded part and a press die able to fold down the protrusively folded part for forming the superimposed part. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a plastic container and lid for packaging molded from a thin plastic sheet, by partially reinforcing the flange and the like to increase the overall rigidity, and the container and lid can be molded with a thinner plastic sheet. It is about the technology that can be done.

  Conventionally, a thin plastic sheet formed as a plastic container by vacuum forming, pressure forming, hot plate pressure forming, press forming, or vacuum / pressure forming has been used in various fields, such as fruits and mushrooms. Sheet packaging containers are also used as packaging packs for agriculture, trays for industrial parts such as electronic parts, and egg packs in the animal husbandry field. One of the most widely distributed fields is for food. This food sheet forming container includes bento boxes and prepared food wrap trays and food packs sold at convenience stores, etc., as well as pillow packaging trays for frozen foods and confectionery, tofu, etc. There are also containers for film packs. In addition, a sheet-molded lid is widely used. Conventionally, the plastic sheet thickness to be used is determined according to the rigidity required for the container.

  On the other hand, in addition to the adjustment of the sheet thickness, it is also well known that a reinforcing rib is provided at the time of molding as a means for increasing rigidity, and as another means, the flange edge formed by protruding from the opening periphery of the container is used. Curled or bent plastic containers are also known (see, for example, Patent Documents 1 to 3).

JP-A-3-261536 JP 2005-29180 A JP 2007-106441 A

  As described above, at present, the circulation amount of sheet-molded containers is extremely large, and most of them are disposable, so the environmental burden related to disposal processing has become a major social problem. In order to reduce or avoid this, it is necessary to make the sheet thickness as thin as possible. However, if the thickness is reduced, the rigidity of the container is sacrificed. Regarding the rigidity required for the container, for example, in the above-mentioned lunch box and side dish container, there are many consumers who serve meals as they are without having to bother transferring the contents to tableware, so that the rigidity can always be maintained Required. In addition, the above-described pillow packaging tray and film pack container do not require rigidity as much as a lunch box container, but when the tray is transferred to a pillow packaging bag or in a film pack container, Rigidity that does not deform the container body due to tension or the like is required. Under such circumstances, in the current technology, the thickness of the sheet according to the container is regarded as the limit of thickness reduction.

  On the other hand, in the means for increasing the rigidity by the reinforcing rib, the surface area of the container is increased by the amount of the reinforcing rib, and as a result, the usage amount of the plastic sheet is increased. It's hard to say. In addition to sacrificing the internal capacity by the amount of the reinforcing rib, it may not be preferable to provide the reinforcing rib depending on the contents such as tofu. At the same time, a container using a lot of ribs is difficult to squeeze when discarded, which is also contrary to dust reduction.

  On the other hand, the means for curling or bending the flange is effective for increasing the rigidity of the entire container while suppressing an increase in the amount of plastic sheet used. Conventionally, the flange is bent in the same direction, that is, a mountain. Since either one of the folding and the valley folding is repeatedly processed, in order to realize this, there are manufacturing disadvantages such as an increase in the number of molding steps by the number of folding. In addition, the flange bent in the same direction has a problem that it can be easily restored to its original shape by the elasticity of plastic.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a sheet forming technique capable of reducing the thickness of the sheet while maintaining necessary rigidity.

  In order to achieve the above-described object, in the present invention, the plastic sheet molding container main body or the flange or rib of the plastic sheet molding lid is formed by overlapping the plastic sheet of the part several times to form an overlapping part with an increased thickness. The means for increasing the strength is used. In particular, in the present invention, the bulging portion formed during sheet molding is crushed to form an overlapping portion in which the plastic sheet of the portion is folded. In other words, in the present invention, the overlapping portion is formed by so-called step folding in which mountain folds and valley folds are combined, instead of being bent in one direction as in the prior art. And since a superimposition part becomes substantially the same as the thickness of three sheets, the intensity | strength of a flange or a rib increases. And since the rigidity of the whole container (in the present invention, both the container main body and the lid are shown) is also increased by the reinforcing flange and the reinforcing rib, the sheet thickness is made thinner when obtaining the same rigidity as before. be able to. In particular, by providing overlapping portions on both the flange and the rib, the rigidity of the entire container can be further increased.

  The overlapping portion is formed in a Z-shaped cross section by crushing the bulging portion formed with one outer angle being substantially acute, and can have the simplest three-sheet thickness configuration. By squeezing the bulging portion formed with a substantially acute outer angle, a cross-sectional dovetail shape is formed. In this case as well, the sheet thickness is three sheets.

  Further, when the flange and the overlapping portion have the same width, a thin flange edge does not protrude from the overlapping portion, and a cut accident can be prevented.

  On the other hand, as a method for producing a plastic sheet molding container having the above-described overlapping portion, the method of the present invention is based on any one of the sheet molding methods of vacuum forming, pressure forming, hot plate pressure forming, press forming, or vacuum pressure forming. A method of providing an overlapped portion obtained by folding a plastic sheet of a portion of a container body or a lid formed from a plastic sheet, and simultaneously forming a soft plastic sheet into a desired overall shape, A sheet molding process of forming a bulging portion having a substantially acute angle at least one outer angle by bulging a part of the plastic sheet obliquely with a movable mold, and crushing the bulging portion toward the outer angle side And a pressing step for forming the overlapping portion. The overlapping portion is preferably formed at a flange or / and a rib. It should be noted that the formation of the flanges and ribs accompanying the molding of the overall shape can be realized by the same fixed mold as in the prior art.

  In the formation of the overlapping portion, it is simplest to form the bulging portion in a substantially triangular shape in which one outer angle is a substantially acute angle in the sheet forming process. It is preferable to form a bifurcated shape having an acute angle. This is because the outer angle is somewhat undercut and is effective in forming a relatively wide overlapping portion from the viewpoint of facilitating mold release from the bulging portion.

  Furthermore, in order to make the widths of the flange and the overlapping portion uniform as described above, it is preferable to cut the excess edge of the flange in accordance with the width of the overlapping portion.

  On the other hand, regarding an apparatus for manufacturing a plastic sheet molding container in which a plastic sheet as described above is folded and used as an overlapping portion, in the present invention, among vacuum forming, pressure forming, hot plate pressure forming, press forming, or vacuum pressure forming An apparatus for providing an overlapped portion obtained by folding a plastic sheet of a portion of a container body or a lid formed from a plastic sheet by any one of the sheet forming methods. A fixed mold moldable into a shape, and a molding surface capable of forming a bulging portion having a substantially acute outer angle at least one of its outer angles by bulging a part of the plastic sheet in an oblique direction; Plastic sheet molding from a movable mold that can be released from the mold and a press mold that can fold the bulge and form the overlapping section Using means that constitute a vessel of the manufacturing apparatus. With this means, the movable mold moves in the mold release direction from the bulging portion. Further, the movable mold is provided corresponding to the top surface of the flange or / and the rib such as the partition. In addition, it is simplest to form the movable mold with a substantially triangular cross section that can form a bulging portion whose one outer angle is a substantially acute angle. It is preferable that the cross section capable of forming the part is bifurcated. This is because even a relatively wide overlapping portion can be easily molded and released.

  As described above, in the present invention, with respect to the container main body and the lid, a portion to be strengthened, for example, a rib such as a flange or a partition, is formed with a cross-sectional Z-shaped or cross-sectional dovetail-shaped overlapping portion. Since the rigidity of the entire container can be increased, the same rigidity as before can be ensured with a thinner plastic sheet. Accordingly, it is possible to reduce the material cost and reduce the product cost, and at the same time, it is possible to simultaneously save resources and reduce the environmental burden associated with the disposal process. In particular, since the overlapping portion in the present invention is formed by a combination of mountain folds and valley folds, the plastic is less likely to be elastically restored and the shape is stable than the plastic sheet is folded in the same direction to form the overlapping portion. Part. Furthermore, for products with the same width of the flange and the overlapping portion, the appearance of the product is good, and a safe container that is not cut at the flange edge can be obtained.

  On the other hand, according to the manufacturing method and manufacturing apparatus of the present invention, the bulging portion is formed at the time of sheet forming, and then the movable mold is released, and at the same time, the bulging portion is crushed and the three sheets are used. Since the overlapping portion having a thickness can be formed, the overlapping portion can be formed by a simpler process and equipment than the conventional method of repeating the bending process, and the rib that could not be formed by the above conventional bending method can be formed. Can also form an overlapping portion.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows an embodiment of a container of the present invention, which has a structure in which a flange 2 is formed on the opening periphery of a container body 1 and the inside is partitioned by rib-shaped partitions 3 and is, for example, pillow-wrapped. It is suitable for internal trays and frozen trays for frozen foods. On the horizontal surface of the flange 2 and the top surface of the partition 3, superposed portions 4 and 5 are provided by folding a plastic sheet. In this embodiment, two types of overlapping portions having different cross-sectional shapes are illustrated for the overlapping portion 4 of the flange 2 and the overlapping portion 5 of the partition 3.

  FIG. 2 is an enlarged cross-sectional view of the overlapping portion 4 provided on the horizontal surface of the flange 2, and is a configuration in which the plastic sheet forming the flange 2 is folded so that the cross section is a flat Z-shape. That is, in the case of the overlapping portion 4 in FIG. 2, the bulging portion formed during sheet forming is crushed. In other words, the overlapping portion 4 is formed by continuously forming a mountain fold 4a obtained by folding a plastic sheet in the width direction of the flange and a valley fold 4b obtained by similarly folding the plastic sheet in the width direction. Further, in the case of this embodiment, the width of the overlapping portion 4 and the flange 2 are the same, and an accident such as cutting the fingertip at the edge so that the edge of the flange 2 does not protrude from the overlapping portion 4 occurs. I am trying not to. In addition, the edge of the flange 2 may be aligned with the overlapping portion 4 in plan view by bending a portion extending from the overlapping portion 4 downward.

  On the other hand, as shown in FIG. 3, the overlapping portion 5 provided on the top surface of the partition 3 has a configuration in which a plastic sheet forming the top surface of the partition 3 is folded so as to have a dovetail shape with a flat cross section. That is, in the case of the superposition part 5 in FIG. 3, the superposition part 4 in FIG. 2 described above is provided symmetrically.

  Each of the superimposing portions 4 and 5 described above has a sheet thickness obtained by stacking three plastic sheets, and the strength of the flange 2 and the partition 3 can be increased. Along with this, the overall rigidity of the container body 1 is also increased by the reinforcing flange and the reinforcing partition. Therefore, when the rigidity is equal to that of the conventional case, the container can be formed with a thinner plastic sheet. For example, the above-described pillow packaging tray for frozen food requires a sheet thickness of 0.25 mm. As a result, the sheet thickness can be reduced to a sheet thickness of 0.2 mm. Thus, according to the present invention, the thickness of the plastic sheet can be reduced by about 30 to 50% as compared with the prior art.

  4 shows a modified example of the superimposing unit 4 in FIG. 2, and FIG. 5 shows a modified example of the superimposing unit 5 in FIG. 3. The superposing unit is configured in a reverse relationship to FIGS. It is.

  In the above embodiment, the overlapping portions 4 and 5 having different cross-sectional shapes are provided between the flange 2 and the partition 3, but either one of the overlapping portions may be provided in common. Moreover, it is not necessary to provide a superimposition part in both the flange 2 and the partition 3, and providing a superimposition part only in any one is also contained in this invention. Furthermore, the partition 3 is a kind of rib, and may be provided with a superimposing portion on the top surface of another rib that is not intended for partitioning. Furthermore, although it is preferable to provide the overlapping portions in the entire circumference of the flange 2 and in all directions of the ribs because the strength is highest, the overlapping portions may be provided in a part of each.

  Next, FIG. 6 shows a method of forming the overlapping portion 4 of FIG. 2 described above together with the manufacturing apparatus of the present invention. In FIG. 6, 10 is provided corresponding to the fixed mold, and 11 is provided corresponding to the flange portion. The movable mold 12 is a press mold. The fixed mold 10 determines the overall shape of the container body and the lid, and has the same concept as a mold conventionally used in vacuum forming, pressure forming, hot plate pressure forming, press forming, and vacuum pressure forming. The movable die 11 is incorporated in a portion corresponding to the flange of the fixed die 10 so as to be movable up and down, and a push-up portion 11a having a substantially triangular cross section extending obliquely with respect to the vacuum suction direction is provided on the molding surface. Is.

  In order to form the overlapping portion 4 of FIG. 2 by the apparatus, first, the movable die 11 is set so that the push-up portion 11a protrudes from the molding surface of the fixed die 10, and the softened state is set according to a common method. After the plastic sheet is supplied, the plastic sheet is brought into close contact with the molding surfaces of the fixed mold 10 and the movable mold 11 by using vacuum suction, compressed air, or both (see FIG. 6A). At the time of the sheet forming process, a bulging portion 13 having one outer angle formed as an acute angle is bulged in an oblique direction by a push-up portion 11a of the movable mold 11 in a portion corresponding to the flange. Next, the movable mold 11 is processed to release the push-up portion 11a from the bulging portion 13 (see FIG. 6B). At this time, since the one outer angle of the bulging portion 13 is an acute angle, it becomes a so-called undercut, but since the plastic sheet is in a softened state and the sheet itself has elasticity, the length of the protruding portion 11a As long as the inclination angle is appropriate, the push-up portion 11a can be released from the bulging portion 13 by simply lowering the movable mold 11 directly below. Then, after the mold release, the press die 12 is lowered and the bulging portion 13 is crushed (folded down) to the outer angle side, thereby forming the flat Z-shaped overlapping portion 4 shown in FIG. (See FIG. 6C).

  In addition, by setting the press surface of the press die 12 and / or the fixed die 10 to have a concavo-convex configuration, it is possible to perform embossing or corrugated concavo-convex processing on the surface of the overlapping portion 4 during press processing.

  On the other hand, FIG. 7 shows an apparatus and a method for forming the overlapping portion 5 shown in FIG. 3 on the flange, and the change from FIG. That is, the push-up portion of the movable mold 21 in this embodiment has a molding surface with a bifurcated cross section (a pigtail shape). In addition, the movable mold 21 is arranged in a portion corresponding to the flange, is incorporated in the fixed mold 10 so as to be movable up and down, and the press mold 12 is the same as the embodiment of FIG. And also in this embodiment, the protruding part of the movable mold 21 is protruded from the molding surface of the fixed mold 10, and sheet molding is carried out according to a conventional method, so that the mold corresponding to the flange is molded into the flange-corresponding portion. According to the surface, a substantially dovetail-shaped bulging portion 14 having both outer angles being substantially acute is formed (see FIG. 7A). Thereafter, the movable mold 21 is lowered to release the movable mold 21 from the bulging portion 14 (see FIG. 7B), and finally the press mold 12 is lowered to bulge. The portion 14 is crushed and the overlapping portion 5 shown in FIG. 3 can be formed on the flange (see FIG. 7C).

  By the way, in embodiment of FIG.6 * 7, the excessive edge which protruded from the overlapping part to the flange may exist intentionally or unavoidably for the reason on shaping | molding. Of course, it is possible to leave the surplus edge as it is, but it is also possible to match the widths of both in a plan view by bending it downward when forming the sheet. In addition, it is possible to cut the excess edge completely by conventional punching methods and cutters, and when the width of the flange and the overlapped part is aligned in this way, the appearance of the product is better than when no treatment is added. It can also prevent cut accidents.

  The above-described embodiment can be variously modified and can be widely applied to conventional sheet molded products. First, by changing the shape and arrangement of the movable mold, the shape and formation location of the overlapping portion can be changed. Furthermore, the molding object is not limited to the internal tray and the wrapping tray used for pillow packaging, but includes other sheet molding containers, and a lid on which a sheet is molded can also be the object of the present invention. Examples of the material for the plastic sheet include polypropylene, polystyrene, and PET, but the material is not particularly limited as long as the sheet can be molded.

  The present invention saves resources and reduces the burden on manufacturing and disposal of plastic sheet molded containers. Even in the background of the recent rise in oil prices, the cost of plastic sheet molded containers can be reduced, and only container manufacturers can It also contributes greatly to general consumers.

Schematic sectional view of a plastic sheet molding container according to an embodiment of the present invention An enlarged cross-sectional view showing an example of the overlapping portion Expanded cross-sectional view showing other overlapping parts FIG. 2 is an enlarged sectional view showing a modification of FIG. Enlarged sectional view showing a modification of FIG. Schematic explanatory drawing showing a manufacturing apparatus and a manufacturing method for forming the overlapping portion of FIG. Schematic explanatory drawing showing a manufacturing apparatus and a manufacturing method for forming the overlapping portion of FIG.

Explanation of symbols

2 Flange 3 Partition 4/5 Overlapping part

Claims (14)

A container body or lid molded from a plastic sheet by any one of vacuum forming, pressure forming, hot plate pressure forming, press forming, or vacuum / pressure forming, and a swelling formed during the sheet forming. A plastic sheet-molding container comprising an overlapping portion obtained by crushing a protruding portion and folding the plastic sheet of the portion. The plastic sheet molding container according to claim 1, wherein the overlapping portion is formed by folding the plastic sheet of the portion in the width direction on the top surface of a flange or / and a rib such as a partition. The plastic sheet molding container according to claim 1 or 2, wherein the overlapping portion is formed by crushing a bulging portion having one outer angle formed at a substantially acute angle. The plastic sheet molding container according to claim 1 or 2, wherein the overlapping portion is formed by crushing a bulging portion in which both outer angles are formed to be substantially acute angles. The plastic sheet molding container according to any one of claims 1 to 4, wherein the flange is provided with an overlapping portion, and the widths of both are made uniform. The plastic sheet is folded on a part of the container body or lid formed from the plastic sheet by any one of vacuum forming, pressure forming, hot plate pressure forming, press forming, or vacuum pressure forming. A plastic sheet in a softened state is formed into a desired overall shape, and at the same time, a part of the plastic sheet is swelled in an oblique direction by a movable mold, and at least one outer angle is provided. Manufacturing a plastic sheet forming container comprising: a sheet forming step for forming a bulging portion having a substantially acute angle; and a pressing step for crushing the bulging portion toward the outer corner to form the overlapping portion. Method. The method of manufacturing a plastic sheet molded container according to claim 6, wherein the overlapping portion is formed by folding the plastic sheet of the portion in the width direction on the top surface of a flange or / and a rib such as a partition. The method for producing a plastic sheet molded container according to claim 6 or 7, wherein in the sheet forming step, the bulging portion is formed in a substantially triangular shape with one outer angle being a substantially acute angle. The method for producing a plastic sheet-molded container according to claim 6 or 7, wherein in the sheet molding step, the bulging portion is formed in a bifurcated shape with both outer angles being substantially acute. The method for manufacturing a plastic sheet molded container according to any one of claims 6 to 9, further comprising a cutting step of cutting an excess edge of the flange in accordance with the width of the overlapping portion. The plastic sheet is folded on a part of the container body or lid formed from the plastic sheet by any one of vacuum forming, pressure forming, hot plate pressure forming, press forming, or vacuum pressure forming. A device for providing a superposed portion, wherein a fixed mold capable of forming a soft plastic sheet into a desired overall shape and a part of the plastic sheet bulge in an oblique direction so that at least one outer angle is A movable die that has a molding surface capable of forming a bulging portion having a substantially acute angle, and that moves releasably from the bulging portion, and a press die that can fold the bulging portion to form the overlapping portion. An apparatus for manufacturing a plastic sheet molding container, characterized by comprising a mold. 12. The apparatus for producing a plastic sheet-molded container according to claim 11, wherein the movable mold is provided corresponding to the top surface of a rib or / and a rib such as a partition. The manufacturing apparatus of a plastic sheet molding container according to claim 11 or 12, wherein the movable mold has a push-up portion having a molding surface having a substantially triangular cross section capable of forming a bulging portion whose one outer angle is a substantially acute angle. 13. The apparatus for producing a plastic sheet-molded container according to claim 11 or 12, wherein the movable mold has a push-up portion formed of a molding surface having a bifurcated section capable of forming a bulging portion whose outer angles are substantially acute.

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