Method for producing resin container, resin container production device, resin container, and mold

Abstract

This method for producing a resin container comprises: an injection molding step for producing a preform; and a blow molding step for producing a resin container by blow molding the preform. In the injection molding step, a predetermined shape is formed on the inner circumferential surface of the preform along the axial direction of the preform. The blow molding step includes: a first step for interposing the bottom part of the preform between a stretching rod and a bottom mold; a second step for rotating the bottom mold and the stretching rod around the axis of the preform with the bottom part of the preform interposed by the first step; and a third step for blow molding the preform twisted by the second step.

Description

Method for manufacturing a resin container, manufacturing apparatus for a resin container, resin container, and mold

[0001] The present disclosure relates to a method for manufacturing a resin container, a manufacturing apparatus for a resin container, a resin container, and a mold. This application claims priority based on Japanese Patent Application No. 2024-198266 filed in Japan on November 13, 2024, the content of which is incorporated herein by reference.

[0002] Patent Documents 1 to 6 disclose a method for manufacturing a container by an extrusion blow molding method. Thus, containers of various shapes can be manufactured by the extrusion blow molding method. For example, Patent Document 1 discloses that it is possible to form a predetermined shape on the inner peripheral surface of a container body by the extrusion blow molding method.

[0003] Japanese Patent No. 5947987, Japanese Patent No. 6533428, JP-A-2021-017283, Japanese Patent No. 7378348, Japanese Patent No. 7378349, JP-A-52-133376

[0004] However, the extrusion blow molding method has the following problems. 1) Since the extrusion molding of the hollow parison and the blow molding and cooling of the container are performed at the same place, the molding cycle is slow. 2) Since the hollow parison suspended from the extruder is immediately blown into a container, the wall thickness unevenness of the container is large. 3) Since the shaping of the entire container is performed only by air, the neck portion and the like cannot be molded with high dimensional accuracy. 4) After blow molding, a step of removing burrs remaining on the container is required, and there is also a large amount of waste material (loss material). 5) It is difficult to reduce the weight of the container (when the weight is reduced, cracking easily occurs at the pinch-off portion at the bottom of the container). In order to solve such problems, it is expected to form a predetermined shape on the inner peripheral surface of the container body by another method.

[0005] An object of the present disclosure is to provide a method for manufacturing a resin container in which a predetermined shape is formed on the inner peripheral surface of the container using a stretch blow molding method, a manufacturing apparatus for a resin container, a resin container, and a mold.

[0006] A method for manufacturing a resin container according to one aspect of the present disclosure comprises: an injection molding step for manufacturing a preform; and a blow molding step for manufacturing a resin container by blow molding the preform, wherein in the injection molding step, a predetermined shape is formed on the inner circumferential surface of the preform along the axial direction of the preform; and the blow molding step includes: a first step of sandwiching the bottom of the preform between a stretching rod and a bottom mold; a second step of rotating the bottom mold and the stretching rod around the axis of the preform while the bottom is sandwiched by the first step; and a third step of blow molding the preform in the twisted state by the second step.

[0007] Furthermore, a resin container manufacturing apparatus according to one aspect of the present disclosure comprises: an injection molding section for manufacturing a preform; and a blow molding section for manufacturing a resin container by blow molding the preform, wherein the injection molding section is configured to form a predetermined shape on the inner circumferential surface of the preform along the axial direction of the preform; the blow molding section includes a cavity mold and a bottom mold that define the outer surface of the resin container; the bottom mold has a holding portion that holds the bottom of the preform by being sandwiched with a stretching rod; and the blow molding section includes a rotation mechanism that rotates the bottom mold around the axis of the preform while the bottom is held by the holding portion.

[0008] Furthermore, a resin container according to one aspect of the present disclosure comprises a neck portion having an opening for the contents to be put in and taken out, a side portion connected to the neck portion, and a bottom portion located on the opposite side of the neck portion and connected to the side portion, wherein spiral ribs are formed on the inner circumferential surface of the side portion.

[0009] Furthermore, a mold for manufacturing a resin container according to one aspect of the present disclosure comprises a first mold for injection molding and a second mold for blow molding, wherein the first mold has a core mold with vertical grooves formed on its surface, and the second mold has a bottom mold with a holding portion formed for holding at least a portion of the bottom of the preform manufactured by the first mold.

[0010] According to this disclosure, it is possible to provide a method for manufacturing a resin container that can form a predetermined shape on the inner circumferential surface of the container body using a stretch blow molding method, a manufacturing apparatus for a resin container, a resin container, and a mold for manufacturing a resin container.

[0011] Figure 1 is a front view of a resin container according to one embodiment. Figure 2 is a front view of a resin container according to one embodiment. Figure 3 illustrates a preform in one embodiment. Figure 4 is a cross-sectional view of a preform in one embodiment. Figure 5 is a functional block diagram of a blow molding apparatus. Figure 6 illustrates a method for manufacturing a resin container according to one embodiment. Figure 7 illustrates an injection molding section. Figure 8 is a horizontal cross-sectional view of an injection core mold. Figure 9 illustrates a blow molding section. Figure 10 is a front view of a blow mold unit in one embodiment. Figure 11 is a top view of a bottom mold. Figure 12 is a perspective view of a preform viewed from above. Figure 13 is a perspective view of a resin container viewed from above. Figure 14 is a perspective view of a preform viewed from below. Figure 15 is a perspective view of a resin container viewed from below.

[0012] The embodiments of this disclosure will be described below with reference to the drawings. Note that the dimensions of the components shown in these drawings may differ from the actual dimensions of the components for the sake of explanation.

[0013] Furthermore, in the description of this embodiment, for the sake of explanation, the terms "left-right direction," "front-back direction," and "up-down direction" will be referred to as appropriate. These directions are commonly set in each figure. These directions are shown for the sake of explanation and are not intended to limit the representation to the illustrated directions. Here, the "up-down direction" includes the "upward direction" and the "downward direction." The "front-back direction" includes the "forward direction" and the "backward direction." The "left-right direction" includes the "left direction" and the "right direction." However, the definition of direction is not limited to these. Also, the front-back direction in Figure 5 corresponds to the longitudinal direction of the blow molding apparatus 100.

[0014] Figures 1 and 2 are front views of a resin container 1010 according to one embodiment. The synthetic resin used as the material for the resin container 1010 is a thermoplastic resin and can be appropriately selected depending on the application. Examples of synthetic resins include PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PCTA (polycyclohexanedimethylene terephthalate), Tritan (Tritan®: a polyester copolymer using cyclobutanediol monomers, a copolyester manufactured by Eastman Chemical Corporation), PP (polypropylene), PE (polyethylene), PC (polycarbonate), PES (polyethersulfone), PPSU (polyphenylsulfone), PS (polystyrene), COP / COC (cyclic olefin polymer), PMMA (polymethyl methacrylate: acrylic), PLA (polylactic acid), and the like.

[0015] As illustrated in Figures 1 and 2, the resin container 1010 is a resin container composed of a neck portion 1012 having an entrance / exit portion (opening) 1011 located at the uppermost end, a body portion (side portion) 1013 formed to connect with the neck portion 1012 and defining the side wall portion of the resin container 1010, and a bottom portion 1014 located at the lowermost end and formed to connect with the body portion 1013. The body portion 1013 forms the side portion of the resin container 1010. The entrance / exit portion 1011 has an opening surface (top surface). The bottom portion 1014 is positioned on the opposite side from the neck portion 1012 in the vertical direction.

[0016] On the inner circumferential surface of the body portion 1013, convex ribs 1015 are formed toward the central axis of the resin container 1010. In this embodiment, the ribs 1015 are mainly formed from the body portion 1013 to the bottom portion 1014. The ribs 1015 are also formed on the shoulder portion 1016 formed between the neck portion 1012 and the body portion 1013. For example, 10 to 20 ribs 1015 may be formed. In this embodiment, 16 ribs 1015 are formed. The number of ribs can be appropriately changed depending on the design of the container. Similarly, the location where the ribs are formed can be appropriately changed depending on the design of the container.

[0017] The rib 1015 is formed in a spiral shape from the shoulder portion 1016 to the bottom portion 1014. The rotation angle of the spiral of the rib 1015 is, for example, 5° to 720°, and preferably 45° to 180°. The rotation angle of the spiral can be appropriately changed depending on the design of the container.

[0018] Figure 3 illustrates a preform 1020 in one embodiment. Specifically, Figure 3 includes a front view, a cross-sectional view, and a line-of-sight view of the preform 1020. F10A illustrates a front view of the preform 1020. F10B is a cross-sectional view along the line 10B-10B in F10A. F10C is a line-of-sight view from the direction of 10C in F10A. Figure 4 is a cross-sectional view of the preform 1020 in one embodiment. Specifically, Figure 4 is a cross-sectional view showing a cross section perpendicular to F10C in Figure 3. As illustrated in Figures 3 and 4, the preform 1020 comprises a neck portion 1022, a body portion 1023, and a bottom portion 1024.

[0019] Ribs 1025 are formed on the inner circumferential surfaces of the body portion 1023 and the bottom portion 1024. The ribs 1025 formed on the preform 1020 are formed to extend linearly in the vertical direction. The bottom portion 1024 has a protruding portion 1026 that protrudes downward from other parts. The protruding portion 1026 is formed in a polygonal or elliptical shape when viewed from below, for example, in a rectangular shape. In addition, the gate portion 1027, which is close to the resin injection gate during preform molding, is formed to extend downward from the protruding portion 1026.

[0020] Next, a blow molding apparatus 100 for manufacturing containers will be described with reference to Figure 5. Figure 5 is a block diagram of the blow molding apparatus 100.

[0021] As illustrated in Figure 5, the blow molding apparatus 100 includes an injection molding section 110 for manufacturing a preform 1020 and a temperature control section 120 for adjusting the temperature of the manufactured preform 1020. An injection device 112 is connected to the injection molding section 110 for melting and supplying the resin material, which is the raw material. The blow molding apparatus 100 also includes a blow molding section 130 for blowing the preform 1020 to manufacture a resin container 1010 and a removal section 140 for removing the manufactured resin container 1010.

[0022] The injection molding section 110, the temperature control section 120, the blow molding section 130, and the removal section 140 are positioned at predetermined angles (90 degrees in this embodiment) around the transport means 150. The transport means 150 is composed of a rotating plate or the like, and the preform 1020 or resin container 1010, in which the neck portions 1012 and 1022 are supported by a neck type attached to a rotating plate (not shown), is transported to each section as the rotating plate rotates.

[0023] The injection molding unit 110 shown in Figure 5 includes an injection cavity mold, an injection core mold, a neck mold, etc., which are not shown. A bottomed preform 1020 is manufactured by pouring resin material from the injection device 112 into the preform-shaped space formed by clamping these molds together.

[0024] The temperature control unit 120 is configured to adjust the temperature of the preform 1020 manufactured in the injection molding unit 110 to a suitable temperature for final blow molding. The blow molding unit 130 is configured to blow mold the preform 1020 whose temperature has been adjusted in the temperature control unit 120 to manufacture a resin container 1010. The blow molding unit 130 includes a blow molding die (see Figure 9) and a stretching mechanism (not shown). The stretching mechanism includes a stretching rod 1313 (see Figure 9) and a blow nozzle (blow core, not shown).

[0025] The removal section 140 is configured to remove the resin container 1010 manufactured in the blow molding section 130 by opening the neck portion 1012 of the resin container 1010 from the neck mold 152 (see Figure 7).

[0026] Figure 6 illustrates a method for manufacturing a resin container 1010 according to this embodiment. The method for manufacturing the resin container 1010 includes an injection molding step S11, a temperature control step S12, a blow molding step S13, and a removal step S14. The blow molding step S13 includes a first step S131, a second step S132, and a third step S133. The injection molding step S11, the temperature control step S12, the blow molding step S13, and the removal step S14 are performed in the injection molding unit 110, the temperature control unit 120, the blow molding unit 130, and the removal unit 140, respectively, as illustrated in Figure 5.

[0027] The injection molding process S11 is a process for manufacturing the preform 1020. In the injection molding process S11, a predetermined shape is formed on the inner circumferential surface of the preform 1020 along the axial direction of the preform 1020. In this embodiment, the predetermined shape is a rib 1025, but it may also be a groove or a protrusion. Thus, the predetermined shape can be appropriately changed depending on the design of the container.

[0028] The temperature control step S12 is a step in which the preform 1020 manufactured in the injection molding step S11 is adjusted to a temperature suitable for blow molding. Note that the temperature control step S12 is not necessarily required.

[0029] The blow molding process S13 is a process for manufacturing a resin container 1010 by blow molding a preform 1020. The blow molding process S13 can be subdivided into three steps: the first step S131, the second step S132, and the third step S133. Details of the first step S131, the second step S132, and the third step S133 will be described later.

[0030] The removal process S14 is the process of removing the manufactured resin container 1010 from the blow molding apparatus 100.

[0031] Figure 7 illustrates an injection molding section 110. The injection molding section 110 includes a mold opening / closing mechanism for the injection molding section and an injection molding die. The injection molding die comprises one or more injection cavity molds 113 and one or more injection core molds 114. The injection cavity molds 113 and injection core molds 114, together with the neck mold 152, form an injection cavity. The injection cavity molds 113 and injection core molds 114 are examples of first molds for injection molding. The molten resin injected from the injection device 112 is poured into the injection cavity and cooled to form one or more preforms 1020.

[0032] Figure 8 is a horizontal cross-sectional view of the injection core mold 114. The horizontal cross-section of the injection core mold 114 has a shape in which grooves GR are formed on a substantially circular outer surface portion 1141. When molten resin flows into the grooves GR and cools, ribs 1025 are formed on the inner circumferential surface of the preform 1020. In this example, the grooves GR are substantially semicircular in shape on the horizontal cross-section, but this is not the only example. They can be appropriately modified considering molding factors such as the design of the container and the ease with which the molten resin flows.

[0033] Figure 9 illustrates a blow molding section 130. The blow molding section 130 includes a mold opening / closing mechanism for the blow molding section and a blow molding die. The blow molding die includes at least one blow cavity die 1311, one or more bottom dies 1312, one or more stretching rods 1313, and a rotating mechanism 1314. The blow cavity die 1311 and the bottom die 1312 form the blow cavity. The blow cavity die 1311 is a split die and is an example of a second die for blow molding.

[0034] The rotating mechanism 1314 is provided on the bottom mold 1312 and has a drive unit such as a motor for rotating the bottom mold 1312. The blow molding die may further include a pair (two) of blow cavity mold fixing plates (not shown) and a bottom mold support plate (not shown). In this case, one or more of the split molds constituting the blow cavity mold 1311 are fixed to the blow cavity mold fixing plate. The bottom mold support plate rotatably supports one or more bottom molds 1312.

[0035] The stretching rod 1313 is displaceable downward in order to stretch the preform 1020. The blow molding section 130 is provided with the stretching rod 1313, a lifting mechanism 1322, a stretching rod fixing plate 1319, and a bearing 1320. The lifting mechanism 1322 consists of a drive mechanism such as an air cylinder or an electric motor, and a transmission mechanism (lifting member, movable member) such as a cylinder rod or a rack and pinion mechanism. The lifting mechanism 1322 is configured to displace the stretching rod 1313 up and down by operating the transmission mechanism (cylinder rod, etc.) 1321. The stretching rod fixing plate 1319 is connected to the transmission mechanism 1321 and displaces up and down. The stretching rod fixing plate 1319 holds the bearing 1320, and the bearing 1320 supports the stretching rod 1313, thereby allowing the stretching rod 1313 to rotate relative to the stretching rod fixing plate 1319.

[0036] Figure 10 is a front view of a blow mold unit 1310 in one embodiment, viewed from the opening and closing direction of the blow cavity mold 1311. The blow mold unit 1310 comprises at least a blow cavity mold 1311, one or more bottom molds 1312 (or bottom mold members 1330), and a rotation mechanism 1314 for rotating the bottom molds 1312. The blow mold unit 1310 is positioned and fixed to the upper surface of the lower base 1301 of the blow molding section 130 (or blow molding apparatus 100).

[0037] The blow cavity mold 1311 consists of a pair of split molds 1311A that open and close perpendicular to the plane of the paper in Figure 10. Figure 10 shows one of the pair of split molds 1311A, but does not show the other split mold 1311A. In Figure 10, the inner surface of one split mold 1311A that faces the other split mold 1311A is shown. Each of the pair of split molds 1311A is fixed to a pair of blow mold fixing plates 1311B located on the back of each. Each of the pair of blow mold fixing plates 1311B is connected to a mold opening and closing mechanism for the blow molding section, which consists of a hydraulic cylinder, an electric mechanism, etc.

[0038] A bottom mold member 1330 is positioned between a pair of split molds 1311A. The bottom mold member 1330 comprises at least one bottom mold 1312, a bottom mold support plate (bottom mold fixing plate) 1315 that supports the bottom mold 1312 so that it can rotate on its first surface side (top surface side), a bottom mold moving member (bottom mold lifting plate) 1315A that moves the bottom mold 1312 forward and backward (lifts and lowers) relative to the blow cavity mold 1311, and a rotation mechanism 1314 that rotates the bottom mold 1312 relative to the bottom mold support plate 1315. The bottom mold support plate 1315 and the bottom mold moving member 1315A are connected by a rod member 1315B. The bottom mold moving member 1315A is connected to a bottom mold drive (lifting and lowering) mechanism 1315D, which consists of a hydraulic cylinder or electric motor, etc., that can move (lift and lower) the bottom mold 1312. The bottom member 1330 may further include a second bottom support plate (second bottom fixing plate) 1315C.

[0039] The rotating mechanism 1314 comprises at least a drive mechanism 1341 consisting of an electric motor or the like, a transmission member 1342 that transmits the force of the drive mechanism 1341 to the bottom mold 1312, and a bearing 1316. In this example, the drive mechanism 1341 is configured as follows. The rotating shaft of the drive mechanism 1341 has a first bevel gear 1342A at one end. The first support member (shaft) 1342B has a second bevel gear 1342C at one end that engages with the first bevel gear 1342A. The second support member (shaft) 1342D is fixed to the bottom mold 1312 and hangs down from the bottom mold 1312. The third support member (shaft) 1342E is positioned between the first support member 1342B and the second support member 1342D, or between the two second support members 1342D.

[0040] A spur gear 1342F is fixed to the outer circumferential surface of each of the aforementioned support members. The spur gear 1342F fixed to the outer circumferential surface of the first support member 1342B is the first spur gear. The spur gear 1342F fixed to the outer circumferential surface of the second support member 1342D is the second spur gear. The spur gear 1342F fixed to the outer circumferential surface of the third support member 1342E is the third spur gear. The bottom support plate 1315 has a plurality of through holes that penetrate vertically through the bottom support plate 1315, and each through hole is provided with a bearing 1316 on its inner circumferential surface. The first support member 1342B, the second support member 1342D, and the third support member 1342E are each supported by the bottom support plate 1315 via the bearing 1316. In this state, the first spur gear, the second spur gear, and the third spur gear are engaged with each other.

[0041] The second bottom support plate 1315C is provided below the first spur gear, the second spur gear, and the third spur gear. The second bottom support plate 1315C has a plurality of through holes that penetrate vertically through it, and supports the first shaft support member 1342B, the second shaft support member 1342D, and the third shaft support member 1342E via bearings 1316 provided on the inner circumferential surface of each through hole. The bevel gear, shaft support member, and spur gear described above are examples of the transmission member 1342. With this structure, the bottom 1312 is mounted to the bottom support plate 1315 so as to be able to rotate. The drive mechanism 1341 is fixed to the bottom moving member 1315A, or to the blow-type fixing plate 1311B located below the bottom support plate 1315.

[0042] The blow core 1317 is fixed to the blow core fixing plate 1318. The blow core 1317 contacts the neck portion 1022 of the preform 1020 and introduces a pressurized medium such as air into the preform 1020 (blows it). The upper base 1302 of the blow molding section 130 (or blow molding apparatus 100) supports the rotating plate 1303. The blow core fixing plate 1318 is positioned above the upper base 1302 and is connected to a lifting mechanism 1318A such as an air cylinder or electric motor that moves (lifts and lowers) the blow core fixing plate 1318.

[0043] The extension rod 1313 is fixed by an extension rod fixing plate 1319. Specifically, the extension rod 1313 includes a first member 1313A having a cylinder shape extending vertically, and a second member 1313B having a cylindrical shape extending in the vertical direction inside the first member 1313A. The second member 1313B includes a pressing member 1313C at the lower end, which presses the preform 1020 from the inner surface and stretches it in the direction of the bottom die 1312. The extension rod fixing plate 1319 fixes the first member 1313A. The second member 1313B is rotatable relative to the first member 1313A by a bearing 1320. The extension rod fixing plate 1319 is also disposed above the upper base 1302 and is connected to a lifting mechanism 1322 such as an air cylinder or an electric motor that moves (lifts and lowers) the extension rod fixing plate 1319.

[0044] Note that the blow mold unit 1310 may also include a blow core 1317 (blow core fixing plate 1318) and an extension rod 1313 (extension rod fixing plate 1319).

[0045] A pair of guide rails 1351 extending in the opening and closing direction of the blow cavity mold 1311 are provided below the rotating plate 1303. The neck mold 152 is composed of a pair of neck split molds, and each neck split mold is fixed to a pair of plate-like members constituting the neck mold fixing plate 1352. The pair of guide rails 1351 support the pair of plate-like members of the neck mold fixing plate 1352 so as to be movable along the guide rails 1351. That is, the guide rails 1351 support the neck mold fixing plate 1352 or the neck mold 152 so that it can be opened and closed.

[0046] The operation of rotating the preform 1020 will now be described. With the preform 1020 supported by the neck mold 152, it is transported to the blow molding section 130 by the rotating plate 1303 and set in the open blow cavity mold 1311 (between the pair of split molds 1311A). After setting the preform 1020, the blow cavity mold 1311 (the pair of split molds 1311A) is closed. Next, the stretching rod 1313 and the blow core 1317 are displaced downward. The pressing member 1313C at the tip of the stretching rod 1313 contacts the inner circumferential surface of the bottom portion 1024 of the preform 1020, and the body portion 1023 of the preform 1020 is stretched downward. The preform 1020 is stretched and comes into contact with the bottom mold 1312. At this time, the bottom portion 1024 of the preform 1020 is sandwiched between the pressing member 1313C at the tip of the stretching rod 1313 (second member 1313B) and the upper surface of the bottom mold 1312. Furthermore, the lower end of the blow core 1317 is in airtight contact with the neck portion 1022 of the preform 1020.

[0047] Next, the base mold 1312 is made to rotate by rotating the drive mechanism 1341 of the rotating mechanism 1314. Specifically, the rotational force of the drive mechanism 1341 is transmitted to the second bevel gear 1342C and the first pivot member 1342B via the first bevel gear 1342A. At this time, the direction of power transmission of the drive mechanism 1341 is changed by 90°. Next, the rotational force of the first pivot member 1342B is transmitted to the third spur gear and the third pivot member 1342E via the first spur gear. The rotational force of the third pivot member 1342E is transmitted to the second spur gear and the second pivot member 1342D. Since the second pivot member 1342D is held by the base mold support plate 1315 via the bearing 1316, the base mold 1312 fixed to the second pivot member 1342D rotates. The third support member 1342E and the third spur gear cause the second support member 1342D and the base mold 1312 to rotate in the same direction. At this time, the second member 1313B of the extension rod 1313 also rotates in conjunction with the rotation of the base mold 1312, driven by the bearing 1320.

[0048] As a result, the bottom 1024 of the preform 1020 rotates (spins) with respect to the neck 1022, and the body 1023 of the preform 1020 is twisted. Thereby, the vertical ribs 1025 formed on the inner peripheral surface of the preform 1020 are deformed into a spiral shape. Thereafter, a pressurizing medium (e.g., compressed air) is introduced by the blow core 1317, and the preform 1020 is blown and shaped into the shape defined by the blow cavity mold 1311.

[0049] FIG. 11 is a top view of the bottom mold 1312. For example, a concave holding portion 1312a is formed in the bottom mold 1312. In FIG. 11, the holding portion 1312a is illustrated by oblique lines. The holding portion 1312a can accommodate the protruding portion 1026 of the preform 1020. Since the protruding portion 1026 accommodated in the holding portion 1312a is held so as not to rotate with respect to the holding portion 1312a, the preform 1020 is positioned with respect to the bottom mold 1312. The specific shapes of the holding portion 1312a and the protruding portion 1026 can be appropriately changed as long as the condition that the preform 1020 is positioned with respect to the bottom mold 1312 in the direction around the rotation axis of the preform 1020 is satisfied.

[0050] The blow molding step S13 and the first step S131 to the third step S133 will be described using FIGS. 9 and 11. The first step S131 is a step of sandwiching the bottom surface of the bottom 1024 of the preform 1020 between the stretching rod 1313 and the bottom mold 1312. When the preform 1020 is set in the blow molding section 130, the stretching rod 1313 is displaced downward to stretch the preform 1020 downward. When the preform 1020 is stretched and contacts the bottom mold 1312, the protruding portion 1026 is accommodated in the holding portion 1312a. As a result, the bottom surface of the preform 1020 is sandwiched between the stretching rod 1313 and the bottom mold 1312.

[0051] The second step S132 is a step in which the bottom mold 1312 and the stretching rod 1313 rotate around the axis of the preform 1020 while the bottom surface of the preform 1020 is sandwiched by the first step S131. When the rotating mechanism 1314 rotates the bottom mold 1312, the bottom portion 1024 of the preform 1020 rotates relative to the neck portion 1022, and the preform 1020 is twisted. As a result, the vertical ribs 1025 formed on the inner circumferential surface of the preform 1020 are deformed into a spiral shape. At this time, a downward force is applied to the stretching rod 1313, so the stretching rod 1313 rotates in conjunction with the bottom mold 1312.

[0052] The third step, S133, is a blow molding process of the preform 1020, which has been twisted in the second step. In the third step, S133, low-pressure primary air and high-pressure secondary air are introduced into the preform 1020. Through blow molding, the preform 1020 is shaped into the form defined by the blow cavity. As a result, spiral ribs 1015 are formed on the inner circumferential surface of the resin container 1010.

[0053] Note that the first step S131 and the second step S132 may be performed with the blow cavity mold 1311 open. In this case, the blow cavity mold 1311 is closed before the third step S133 is performed.

[0054] According to the blow molding apparatus 100 and manufacturing method of this embodiment, a resin container 1010 can be manufactured in which ribs 1015 of a predetermined shape are formed on the inner circumferential surface of the resin container 1010 using the stretch blow molding method.

[0055] Furthermore, in this embodiment, in the first step, the protruding portion 1026, which is part of the bottom surface of the preform 1020, is held in a state where it is fitted into the holding portion 1312a. Therefore, the second step of twisting the preform 1020 can be performed with high precision.

[0056] Figure 12 is a perspective view of the preform 1020 from above. Figure 13 is a perspective view of the resin container 1010 from above. Figure 14 is a perspective view of the preform 1020 from below. Figure 15 is a perspective view of the resin container 1010 from below. As shown in Figure 13, it can be observed that spiral ribs are formed from the shoulder to the side of the container. From Figure 14, it can be observed that the ribs are formed all the way to the bottom of the preform. From Figure 15, it can be observed that the ribs are formed all the way to the bottom of the container, forming a concentric spiral-like design at the bottom.

[0057] Although this disclosure has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of this disclosure. Furthermore, the number, position, shape, etc. of the components described above are not limited to the embodiments described above and can be changed to a number, position, shape, etc. that is suitable for carrying out this disclosure.

[0058] This disclosure is not limited to the embodiments described above, and can be freely modified, improved, etc. as appropriate. Furthermore, the material, shape, dimensions, numerical values, form, number, placement, etc. of each component in the embodiments described above are arbitrary and not limited, as long as they can achieve the purpose of this disclosure.

[0059] In the above embodiment, air was given as an example of the pressurizing medium for blowing the preform 1020, but a gaseous medium other than air may be used, or a liquid medium such as water may be used to pressurize it.

[0060] In the above embodiment, the blow molding apparatus 100 is a so-called four-station type apparatus, in which a temperature control unit 120 is provided between the injection molding unit 110 and the blow molding unit 130, but it is not limited to this. The blow molding apparatus 100 may be a so-called two-station or three-station type apparatus, for example, in which the temperature control unit 120 is not provided.

[0061] Furthermore, in the blow molding process S13 according to the above embodiment, a pre-blow may be performed before the third process S133, during and around the second process S132 in which the preform 1020 is twisted. By performing a pre-blow, the shape of the preform 1020 may be adjusted so that the twisting of the preform 1020 prevents the body portion 1023 from coming into contact with the stretching rod 1313, or so that the bottom surface including the protrusion 1026 is in close contact with the bottom mold 1312.

[0062] The rotating mechanism 1314 is positioned below the bottom mold support plate 1315, which has ample empty space, and is positioned so as not to interfere with the lifting mechanism of the bottom mold 1312, by changing the power transmission direction of the drive mechanism 1341 by 90°. Furthermore, the rotating mechanism 1314 is directly provided on the blow mold unit 1310 (second mold, bottom mold member 1330). For this reason, the blow mold unit 1310 of the present invention is space-saving despite having an additional component (rotating mechanism 1314), and it is possible to manufacture a resin container 1010 having a predetermined shape (spiral rib 1015) on its inner circumferential surface simply by mounting the blow mold unit 1310 of the present invention, without particularly changing the structure of the conventional blow molding apparatus.

[0063] Furthermore, in the above-described embodiment, the structure for rotating the base mold 1312 may be, for example, the structure shown below. For example, the rotation mechanism 1314 may be configured such that a pinion gear is fixed to each of the support members (shafts), a rack connected to a drive mechanism such as an electric motor is made movable, and the base mold 1312 is rotated by engaging the pinion gear and the rack. Alternatively, the rotation mechanism 1314 may be configured such that a driven pulley is connected to the lower end of the first support member 1342B, and a drive pulley is connected to the rotating shaft of a drive mechanism such as an electric motor, and each pulley is connected by a timing belt to rotate the base mold 1312.

[0064] Furthermore, in the above-described embodiment, the base mold 1312 may be rotated. For example, a gripping mechanism may be provided on the base mold 1312 instead of the concave holding portion 1312a. In this case, after the gripping mechanism grasps the bottom portion 1024 (such as the protruding portion 1026) of the preform 1020, the rotation mechanism 1314 rotates the base mold 1312 to twist the preform 1020. The operation of clamping the bottom portion 1024 of the preform 1020 between the stretching rod 1313 and the base mold 1312 is not necessarily required.

Claims

1. A method for manufacturing a resin container, comprising: an injection molding step for manufacturing a preform; and a blow molding step for manufacturing a resin container by blow molding the preform, wherein in the injection molding step, a predetermined shape is formed on the inner circumferential surface of the preform along the axial direction of the preform; and the blow molding step comprises: a first step of sandwiching the bottom of the preform between a stretching rod and a bottom mold; a second step of rotating the bottom mold and the stretching rod around the axis of the preform while the bottom is sandwiched in the first step; and a third step of blow molding the preform in the twisted state resulting from the second step.

2. The method for manufacturing a resin container according to claim 1, wherein the predetermined shape is a vertical rib.

3. The method for manufacturing a resin container according to claim 1, wherein a concave retaining portion is formed in the bottom mold, and in the first step, at least a portion of the bottom of the preform is held in a state where it is fitted into the retaining portion.

4. A resin container manufacturing apparatus comprising: an injection molding section for manufacturing a preform; and a blow molding section for manufacturing a resin container by blow molding the preform, wherein the injection molding section is configured to form a predetermined shape on the inner circumferential surface of the preform along the axial direction of the preform; the blow molding section includes a cavity mold and a bottom mold that define the outer surface of the resin container; the bottom mold has a holding portion that holds the bottom of the preform by being sandwiched with a stretching rod; and the blow molding section includes a rotation mechanism that rotates the bottom mold around the axis of the preform while the bottom is held by the holding portion.

5. A resin container comprising: a neck portion having an opening for the contents to be dispensed; a side portion connected to the neck portion; and a bottom portion located on the opposite side of the neck portion and connected to the side portion, wherein spiral ribs are formed on the inner circumferential surface of the side portion.

6. A mold for manufacturing a resin container, comprising a first mold for injection molding and a second mold for blow molding, wherein the first mold has a core mold with vertical grooves formed on its surface, and the second mold has a bottom mold with a holding portion formed for holding a portion of the bottom of the preform manufactured by the first mold.

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