Manufacturing method for freestanding container

Abstract

The present invention provides a method for manufacturing a free-standing container that can reduce the possibility of a molding defect in which the skirt portion is pinched between split molds. [Solution] The method for manufacturing a free-standing container 60 is a method for manufacturing a free-standing container 60 by blow molding a preform 50 in a blow molding mold 30. The preform 50 has a mouth portion 52 having an open end 51, a substantially cylindrical body portion 55, a bottom portion 56 closing the end of the body portion 55, and a tubular skirt portion 57 protruding from the bottom portion 56. The skirt portion 57 is provided so as to surround a central region 560 of the bottom portion 56. In the blow molding, before closing a pair of split molds 31, 32, a tip 330 of a rod 33 is brought into contact with the central region 560, and a bottom mold 34 is brought into contact with an inner peripheral surface 570 and the central region 560 to sandwich and fix the portion where the tip 330 is in contact between the tip 330 and the bottom mold 34, and the pair of split molds 31, 32 are further closed to blow compressed air through the mouth portion 52.

Description

[Technical field]

[0001] The present invention relates to a method for making a freestanding container. [Background technology]

[0002] Conventionally, as a container for containing liquids such as liquid reagents and blood, a container with a convex bottom such as a round bottom or a cone bottom so that it can be directly put into a centrifuge or the like is known. As such a container, a self-supporting container is known in which a skirt part (skirt part) for self-supporting is integrally formed at the lower end of the container body so as to surround the convex bottom so that it can be stored and housed in a self-supporting state. Patent Document 1 proposes a self-supporting specimen container with a cylindrical skirt part that surrounds a cone bottom and a screwed mouth. Patent Document 2 (FIG. 2) also proposes a self-supporting reagent container with a cylindrical skirt part that surrounds a cone bottom and a mouth part that can be plugged. In addition, various types of self-supporting centrifuge tubes made of resin (PP) are commercially available.

[0003] Meanwhile, the inventors of the present application have developed and proposed in Patent Document 3 a free-standing container in which a skirt portion for supporting the container is integrally formed surrounding a convex bottom portion that has not been seen in the prior art, and a molding method thereof. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 53-74985 [Patent Document 2] JP 2000-46624 A [Patent Document 3] Patent No. 7430019 Summary of the Invention [Problem to be solved by the invention]

[0005] However, even with the molding method of Patent Document 3, there remains a problem of slight shrinkage deformation of the preform due to heating. That is, when the mold is closed, the skirt portion molded integrally with the preform may be pushed up against the bottom mold due to the shrinkage deformation and may be pinched between the split molds.

[0006] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide a method for manufacturing a self-supporting container that can significantly reduce the possibility of molding defects such as the skirt portion being pinched between split molds. [Means for solving the problem]

[0007] The present invention has been made to solve at least some of the above-mentioned problems, and can be realized in the following aspects or application examples.

[0008] [1] One aspect of the method for producing a freestanding container according to the present invention comprises: 1. A method for blowing a preform in a blow mold to produce a free standing container, comprising the steps of: The preform includes a mouth portion having an open end, a substantially cylindrical body portion, a bottom portion closing an end of the body portion, and a tubular skirt portion protruding from the bottom portion, The skirt portion is provided to surround a central region of the bottom portion, The blow molding mold includes a pair of split molds having a cavity for forming a container body of the self-supporting container, a bottom mold that fits the inner peripheral surface of the skirt portion and the central region, and a rod that is inserted into the body portion from the mouth portion; The blow molding process is performed by connecting the tip of the rod to the central region before closing the pair of split molds. The method is characterized in that the tip is brought into contact with the bottom mold, the bottom mold is brought into contact with the inner peripheral surface and the central region, the portion where the tip is in contact is sandwiched and fixed between the tip and the bottom mold, and further the set of split molds is closed and compressed air is blown in from the opening.

[0009] [2] In one embodiment of the method for producing a self-supporting container, The blow mold further includes a pair of holding dies for holding a portion of the body portion adjacent to the mouth portion and / or the mouth portion, The set of retention dies may contact the portion and / or the mouth to hold the preform in place before the tip contacts the central region.

[0010] [3] In any one of the embodiments of the method for producing a self-supporting container, The tip may have the same shape as the inner surface of the central region.

[0011] [4] In any one of the embodiments of the method for producing a self-supporting container, The self-supporting container has a lowest portion on the inner surface of the bottom portion that is the lowest position when the container is self-supporting, and an open end of the skirt portion that contacts the ground when the container is self-supporting, The vertical height from the free end to the lowest part may be constant from when the tip contacts the central region until the blow molding is completed. Effect of the Invention

[0012] According to the present invention, it is possible to provide a method for manufacturing a free-standing container that can significantly reduce the possibility of molding defects such as the skirt portion being pinched between split molds. [Brief description of the drawings]

[0013] [Figure 1] 1 is a schematic plan view of a blow molding device used in a method for manufacturing a free-standing container according to the present embodiment. FIG. [Diagram 2] 1 is an example of a flowchart of a method for manufacturing a free-standing container. [Diagram 3] 10A to 10C are vertical cross-sectional views of the blow molding part illustrating a rod insertion process. [Figure 4] 11 is a vertical cross-sectional view of the blow molding part illustrating a fixing step. FIG. [Diagram 5] 5 is a vertical cross-sectional view of the blow molding section illustrating a mold closing step. FIG. [Figure 6] 4 is a vertical cross-sectional view of a blow molding section illustrating a blowing process. FIG. [Figure 7] 5 is a vertical cross-sectional view of the blow molding part illustrating a mold opening step. FIG. [Figure 8] FIG. 11 is a partial cross-sectional view of the ejection portion illustrating the ejection step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. Note that the embodiments described below do not unduly limit the contents of the present invention described in the claims. In addition, not all of the configurations described below are necessarily essential components of the present invention.

[0015] 1. Blow molding equipment A blow molding apparatus 1 used in this embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic plan view of the blow molding apparatus 1 used in the method for producing a free-standing container 60 according to this embodiment.

[0016] As shown in FIG. 1, the blow molding apparatus 1 includes, for example, a heating section 4 and a blow molding section 6 arranged on a base 2. The blow molding apparatus 1 includes, for example, a turntable 10 that rotates continuously or intermittently on the base 2, and a plurality of nozzles 36 attached at predetermined intervals along the outer periphery of the turntable 10. Note that in this embodiment, a blow molding apparatus 1 in which the turntable 10 rotates intermittently will be described. A plurality of heating sections 4 are arranged at the stop positions of the nozzles 36 that move with the rotation of the turntable 10. The blow molding section 6 includes a set of blow molding nozzles arranged on the outer periphery of the turntable 10. The blow molding apparatus 1 includes a pair of blow molding dies 30 and an opening / closing mechanism (not shown) for opening and closing the pair of blow molding dies 30. The blow molding apparatus 1 may further include a supply section 3 and a discharge section 8.

[0017] The base 2 is, for example, in the form of a case or a frame. The base 2 is installed on the floor of a manufacturing plant for the free-standing container 60. On the base 2, components of each unit including the heating unit 4 and the blow molding unit 6 are arranged.

[0018] The supply unit 3 supplies the preforms 50 to the nozzle 36 on the rotating plate 10. The supply unit 3 is disposed at a stop position of the nozzle 36 adjacent to the first heating unit 4. The supply unit 3 includes a known preform supply mechanism, for example, a handling machine. The preform 50 includes, for example, an opening mouth, a substantially cylindrical body connected to the mouth, and a bottom that closes the body (details of the preform 50 will be described later). The preform 50 is made of synthetic resin and is generally manufactured by injection molding, but preforms manufactured by extrusion molding or compression molding may also be used. The supply unit 3 further includes, for example, a hopper, an inclined conveyor, an aligner, and a chute (not shown) disposed on the side of the base 2. The supply unit 3 sequentially inverts the preforms 50 aligned in a state of being supported and hung near the mouth to an inverted state and supplies them to the nozzle 36 with the mouth facing down. The blow molding apparatus 1 may include a supply wheel that transfers the preforms 50 from the supply unit 3 to the heating unit 4. The supply wheel may use the mechanism disclosed in, for example, Japanese Patent Application Laid-Open No. 2012-229114.

[0019] The heating section 4 includes a plurality of heaters arranged along the outer periphery of the rotating platen 10 that transports the preforms 50. The heating section 4 may employ a known mechanism. The preforms 50 supported by the nozzles 36 are heated by the heaters in the heating sections 4, so that the preforms 50 reach a temperature suitable for blow molding. The rotating platen 10 is, for example, substantially disk-shaped in plan view (FIG. 1) and substantially flat in side view. The rotating platen 10 rotates intermittently at a predetermined speed, for example, clockwise. The heating section 4 may include, for example, an elliptical circulating transport path separate from the blow molding section 6. In this case, the heating section 4 may include a known transport means that receives the heated preforms 50 from the transport path of the heating section 4 and delivers them to the blow molding section 6 in sequence.

[0020] The blow molding section 6 is provided with an opening / closing mechanism (not shown) at the stop position of the nozzle 36 on the rotating plate 10. The blow molding section 6 is disposed between the last heating section 4 and the discharge section 8. A set of blow molding dies 30 is attached to the opening / closing mechanism. The blow molding die 30 is opened by the opening / closing mechanism and closed on the preform 50 stopped in the blow molding section 6. The preform 50 is blow molded in the blow molding die 30 to be molded into a free-standing container 60 of a predetermined shape. In the blow molding section 6, the free-standing container 60 is molded in an inverted state with the mouth part facing down. In this embodiment, an example in which the free-standing container 60 is in an inverted state will be described, but the blow molding die 30 may be turned upside down and molded in an upright state with the mouth part facing up.

[0021] The discharge unit 8 removes the free-standing container 60 from the nozzle 36 and moves the free-standing container 60 outside the blow molding apparatus 1. The discharge unit 8 is disposed between the supply unit 3 and the blow molding unit 6, adjacent to the blow molding unit 6. A known mechanism can be employed for the discharge unit 8, and for example, the discharge unit 8 sequentially places the free-standing containers 60 with their mouths facing up on a belt conveyor adjacent to the base 2. The free-standing containers 60 sent out of the blow molding apparatus 1 from the discharge unit 8 are transferred to the next process (not shown), such as a packaging process or a filling process.

[0022] 2. Manufacturing method of free-standing container A method for manufacturing a free-standing container 60 according to this embodiment will be described with reference to Figs. 1 to 8. Fig. 2 is an example of a flow chart of the method for manufacturing a free-standing container 60, Fig. 3 is a vertical cross-sectional view of the blow molding unit 6 illustrating the rod insertion step (S31), Fig. 4 is a vertical cross-sectional view of the blow molding unit 6 illustrating the fixing step (S32), and Fig. 5 is a vertical cross-sectional view of the blow molding unit 6 illustrating the mold closing step (S33). FIG. 6 is a vertical cross-sectional view of the blow molding section 6 explaining the blowing process (S34), FIG. 7 is a vertical cross-sectional view of the blow molding section 6 explaining the mold opening process (S35), and FIG. 8 is a partial cross-sectional view of the discharge section 8 explaining the discharge process (S40).

[0023] The method for producing a free-standing container 60 according to this embodiment is a method for producing a free-standing container 60 (hereinafter simply referred to as a "container 60") by blow molding a preform 50 in a blow molding die 30.

[0024] 2, the method for manufacturing the container 60 according to this embodiment includes, for example, a supplying step (S10), a heating step (S20), a blow molding step (S30), and a discharging step (S40). The blow molding step (S30) includes, for example, a rod inserting step (S31), a fixing step (S32), a mold closing step (S33), a blowing step (S34), and a mold opening step (S35).

[0025] The supply step (S10) is a step in which preforms 50 are sequentially supplied to the nozzle 36 stopped in the supply section 3 shown in Fig. 1 by a preform supply device (not shown). The nozzle 36 supports the preforms 50 in an inverted state with the mouth portion 52 facing downward. The mouth portion 52 of the preform 50 is inserted into the annular groove of the nozzle 36, and the inner peripheral surface of the mouth portion 52 and the thread portion 53 are held by the nozzle 36. In this embodiment, the so-called two-step method (cold parison method) is used in which the injection-molded preforms 50 are supplied to the blow molding device 1.

[0026] The heating step (S20) is a step of heating the preform 50 to a predetermined temperature in the heating section 4. The preform 50 stopped in each heating section 4 rotates around the central axis O (see FIG. 3) by rotating the nozzle 36. A known mechanism arranged in each heating section can be used as the rotation mechanism for the nozzle 36. The heating section 4 heats the body section 55 of the preform 50 to be blow molded with a known heating mechanism (not shown). It is desirable not to heat the bottom section 56 and the skirt section 57 since they are not to be deformed.

[0027] The blow molding step (S30) is a step in which a preform 50 at a predetermined temperature is blow molded in a blow molding die 30 to obtain a container 60, as shown in, for example, FIGS.

[0028] 3 shows an example of a preform 50 arranged in the blow molding section 6 and a blow molding die 30. A known mechanism can be used for opening and closing the blow molding die 30.

[0029] The blow molding mold 30 includes a set of split molds 31, 32 having cavities 310, 320 for forming the container body 65 (FIGS. 6 and 7) of the container 60, a bottom mold 34 that fits the inner circumferential surface 570 and the central region 560 of the skirt portion 57, and a rod 33 that is inserted into the body 55 from the mouth portion 52. The blow molding mold 30 may further include a set of holding molds 35, 35 for holding the mouth portion 52 of the preform 50. The set of holding molds 35, 35 contact a part of the body 55 and the mouth portion 52 to hold the preform 50 in a predetermined position, for example, before the tip 330 of the rod 33 contacts the central region 560 of the bottom 56. The holding mold 35 includes an opening / closing mechanism different from the opening / closing mechanism of the split molds 31, 32. When the preform 50 is transported to the blow molding section 6 and stops, the set of holding molds 35, 35 advances toward the preform 50. The holding mold 35 holds the preform 50 on both sides on the support ring 54, restricting the upward movement of the preform 50. The holding mold 35 is generally plate-shaped and has a recess for receiving the preform 50. The holding mold 35 desirably has a cavity that forms part of the container body 65 immediately above the mouth 52. By the holding mold 35 holding the preform 50 ahead of the split molds 31 and 32, the preform 50 can be centered and the preform 50 can be aligned in the height direction. The opening and closing mechanism of the holding mold 35 may be independent of the opening and closing mechanism of the blow mold 30, or a biasing member (such as a spring) may be provided between the holding mold 35 and the split molds 31 and 32 so that the holding mold 35 is advanced by the opening and closing mechanism of the blow mold 30 and moves the preform 50 ahead of the split molds 31 and 32. The reform 50 may also be sandwiched in place.

[0030] The preform 50 includes a mouth portion 52 having an open end 51, a substantially cylindrical body portion 55, a bottom portion 56 closing the end of the body portion 55, and a tubular skirt portion 57 protruding from the bottom portion 56. The preform 50 includes the mouth portion 52, the body portion 55, and the bottom portion 56 in this order from the bottom along a central axis O which is an imaginary line extending in the vertical direction passing through the center of the circular open end 51 in a plan view. Examples of resins for molding the preform 50 include olefin-based resins such as polyethylene resin and polypropylene resin. The preform 50 is molded integrally, for example, by injection molding.

[0031] The mouth 52 is substantially cylindrical, with one end being an open end 51 and the other end being connected to the lower end of the body 55. A screw portion 53 for attaching a cap and a support ring 54 protruding in an annular shape below the screw portion 53 may be provided on the outer peripheral surface of the mouth 52. In addition, unless otherwise specified, "upper", "lower", "left" and "right" in the description of this embodiment simply refer to upper, lower, left and right in the blow molding unit 6 shown in the drawings. Therefore, if the blow molding device is upside down (container 60 is upright), the upside down in the description of this embodiment will be reversed. In addition, the container 60 containing the contents is used in an upright position on the skirt portion 57 with the bottom 56 facing down.

[0032] The bottom 56 protrudes upward from the end of the body 55. The bottom 56 has a central region 560 surrounded by the skirt 57. The central region 560 is inside the portion where the skirt 57 connects to the bottom 56, and may be the entire bottom 56 if the connecting portion between the skirt 57 and the bottom 56 is the same as or larger than the body diameter, or may be a part of the bottom 56 if the skirt 57 is smaller than the body diameter. The bottom 56 has a shape in which the center protrudes most downward so that residual liquid tends to gather toward the center of the bottom 56 when the container 60 is in an upright state. The bottom 56 has a lowest part 562 that is the lowest position on the inner surface of the bottom 56 when the bottom 56 is freestanding. At least the central region 560 of the bottom 56 is, for example, an approximately truncated cone shape with the center of the bottom 56 as the apex. The approximately truncated cone shape may be a combination of multiple inclined surfaces and arc-shaped surfaces as shown in FIG. 3. The base 56 and the central region 560 may also have a dome-like cross section that is a circular arc.

[0033] The skirt portion 57 is provided so as to surround the central region 560 of the bottom portion 56. The lower end of the skirt portion 57 is integrally formed with the bottom portion 56 so as to coaxially surround the central region 560. The skirt portion 57 is cylindrical and expands from the connection portion with the bottom portion 56 toward the open end portion 572. The open end portion 572 of the skirt portion 57 is a portion that is grounded when the container 60 is in a self-supporting state. The connection portion between the skirt portion 57 and the bottom portion 56 has the same diameter as the upper end of the body portion 55 or a slightly smaller diameter than the upper end. The skirt portion 57 has a truncated cone shape in a side view. It is preferable that the diameter of the open end portion 572 is larger than the diameter of the body portion 55 from the viewpoint of stability when the skirt portion 57 is in a self-supporting state. The skirt portion 57 may adopt other shapes as long as it can stand upright in the container 60 state. For example, the skirt portion 57 may have a plurality of slits so that the inner peripheral surface 570 is not continuous, or may be substantially cylindrical with the same diameter at the top and bottom. The inner peripheral surface 570 and the outer surface of the bottom portion 56 are spaced apart from each other, except for the connection portion between the skirt portion 57 and the body portion 55. The inner peripheral surface 570 is an annular wall surface extending in the vertical direction. The inner peripheral surface 570 may be a wall surface that slopes inwardly downward. The upper end of the skirt portion 57 is an open end, and is located above the center, which is the uppermost end of the bottom portion 56, when the container 60 is in an upright state. When the container 60 is in an upright state, the lower end of the skirt portion 57 is preferably located on the same plane perpendicular to the central axis O in order to make the container 60 self-supporting. It is desirable that the container 60 is molded so that the vertical height H from the open end 572 to the lowest portion 562 has a predetermined dimension.

[0034] The blow molding step (S30) first includes a rod insertion step (S31).

[0035] As shown in FIG. 3, the rod insertion step (S31) is performed by inserting a rod into a predetermined position in the blow molding die 30. The rod 33 is inserted into the preform 50 from the open end 51 along the central axis O. Prior to or simultaneously with the rod insertion step (S31), the holding mold 35 is advanced so that the holding mold 35 contacts the trunk portion 55. The set of holding molds 35, 35 is advanced in advance toward the preform 50 side so as to protrude from the set of split molds 31, 32, for example, by a biasing member, and the holding molds 35, 35 contact the trunk portion 55 as the split molds 31, 32 advance. The advancement of the split molds 31, 32 may be stopped in a state where the holding mold 35 contacts the trunk portion 55, and the rod insertion step (S31) and the fixing step (S32) may be performed. In the rod insertion step (S31), the tip 330 of the rod 33 is brought into contact with the central region 560 before the set of split molds 31, 32 are closed. The tip 330 contacts the central region 560 to fix the bottom 56 in a predetermined position, so that the movement of the bottom 56 is restricted. Even if the body 55 is shortened or bent sideways due to shrinkage deformation caused by heating, the tip 330 can guide the central region 560 to a predetermined position. This reduces the possibility of molding defects caused by the split molds 31 and 32 pinching the skirt portion 57. The tip 330 preferably has the same shape as the inner surface of the central region 560. Since the bottom 56 has a shape in which the center protrudes downward, the tip 330 can guide the central region 560 to a predetermined position. In particular, if the tip 330 and the central region 560 have a surface that is approximately truncated cone in part, positioning becomes more accurate.

[0036] The blow molding process (S30) includes a rod insertion process (S31) followed by a fixing process (S32).

[0037] As shown in FIG. 4, in the fixing step (S32), the bottom mold 34 is brought into contact with the inner peripheral surface 570 of the skirt portion 57 and the outer surface of the central region 560, and the tip 330 is sandwiched between the bottom mold 34 and the inner peripheral surface 570 to fix the portion with which the tip 330 comes into contact. The bottom mold 34 has a recess for receiving the central region 560 and an outer peripheral surface that contacts the inner peripheral surface 570. The recess is preferably formed in substantially the same shape as the outer surface of the central region 560. The outer peripheral surface is preferably formed in substantially the same shape as the inner peripheral surface 570. The bottom mold 34 comes into contact with the inner peripheral surface 570 to fix the skirt portion 57 in a predetermined position. By sandwiching and fixing the central region 560 between the bottom mold 34 and the tip 330, the movement of the bottom portion 56 during blow molding can be more reliably restricted. This can further reduce the possibility of molding defects caused by the split molds 31 and 32 sandwiching the skirt portion 57.

[0038] In the blow molding process (S30), the fixing process (S32) is followed by the mold closing process (S33). In this embodiment, the fixing process (S32) is performed after the rod insertion process (S31), but it is sufficient that the central region 560 is sandwiched between the tip 330 and the bottom mold 34 and fixed at a predetermined position before the mold closing process (S33). Therefore, for example, the bottom mold 34 may be lowered to a predetermined mold closing position, and then the tip 330 of the rod 33 may be brought into contact with the central region 560, and then the mold closing process (S33) may be performed. In this case, it is preferable that the bottom mold 34 has an inclined outer peripheral surface that becomes thinner toward the bottom. While the bottom mold 34 is lowering, the inner peripheral surface 570 can be guided to a predetermined position by the inclined outer peripheral surface. Also, the bottom mold 34 and the tip 330 may be simultaneously brought into contact with the central region 560, and then the mold closing process (S33) may be performed.

[0039] As shown in FIG. 5, in the mold closing step (S33), a pair of split molds 31, 32 are closed around the preform 50 arranged at a predetermined position in the blow mold 30 by the tip 330 and the bottom mold 34. The split molds 31, 32 have cavities 310, 320 extending from the upper end of the holding mold 35 to the bottom 56. The cavities 310, 320 have shapes corresponding to the outer shape of the container body 65 (FIG. 6) of the container 60. The split molds 31, 32 move so as to sandwich the preform 50 from the left and right in the figure, and close the mold. The upper ends of the split molds 31, 32 have shapes corresponding to the outer peripheral surface of the skirt portion 57, and can receive the skirt portion 57 in the mold closed state. Here, the details of the mold opening and closing mechanism of the blow mold 30 will not be described, but a known mechanism used in blow molding equipment can be adopted.

[0040] In the blow molding process (S30), the mold closing process (S33) is followed by the blow process (S34). The blow molding in the blow process (S34) is performed after the tip 330 of the rod 33 is brought into contact with the central region 560 and the bottom mold 34 is brought into contact with the inner circumferential surface 570 and the central region 560, and the part of the tip 330 that is in contact is sandwiched and fixed between the tip 330 and the bottom mold 34, as described above, before closing the pair of split molds 31 and 32.

[0041] As shown in FIG. 6, in the blowing step (S34), compressed air is blown from the mouth 52. More specifically, compressed air is blown into the inside of the preform 50 from the nozzle 36 in contact with the open end 51 of the mouth 52. The body 55 (FIG. 5) of the preform 50 is heated to a predetermined temperature, so it expands laterally until it comes into contact with the cavities 310, 320 by the compressed air. The container body 65 of the container 60 is molded by maintaining the state of contact with the cavities 310, 320 by the compressed air for a predetermined time. During blow molding with compressed air, the central region 560 remains fixed by the tip 330 and the bottom mold 34. The central region 560 fixed by the tip 330 and the bottom mold 34 can maintain the same shape as the preform 50 without being affected by the compressed air. In particular, the vertical height H from the open end 572 to the lowest part 562 is constant from the time the tip 330 comes into contact with the central region 560 until the end of blow molding. This is because height H may be required as a dimension in product standards.

[0042] The blow molding step (S30) includes a blowing step (S34) followed by a mold opening step (S35).

[0043] 7, in the mold opening step (S35), the rod 33 is pulled downward from the molded container 60, the bottom mold 34 is raised, and the holding mold 35 and the split molds 31, 32 are opened to the left and right. To prevent the height H from changing due to slight shrinkage after molding of the container 60, the central region 560 may be maintained fixed by the tip 330 and the bottom mold 34 for a predetermined period of time even after the holding mold 35 and the split molds 31, 32 are opened, and then the rod 33 may be lowered and the bottom mold 34 may be raised.

[0044] 8, in the discharging step (S40), the container 60 transported to the discharging section 8 is removed from the nozzle 36 by, for example, a handling machine (not shown), and is then inverted to an upright position and placed, for example, on a belt conveyer. The molded container 60 can stand on its own in an upright position with a skirt portion 57 extending to a position lower than the lower end of the bottom portion 56.

[0045] According to the method for manufacturing the container 60 according to this embodiment, the possibility of defective molding, such as the skirt portion 57 being pinched between the split molds 31, 32, can be significantly reduced.

[0046] The present invention is not limited to the above-described embodiments, and various modifications are possible, including configurations that are substantially the same as those described in the embodiments (configurations with the same functions, methods, and results, or configurations with the same purpose and effect). The present invention also includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. The present invention also includes configurations that achieve the same effects as the configurations described in the embodiments, or configurations that can achieve the same purpose. The present invention also includes configurations in which publicly known technology is added to the configurations described in the embodiments. [Explanation of symbols]

[0047] Reference Signs List 1...blow molding apparatus, 2...base, 3...supply section, 4...heating section, 5...first transfer section, 6...blow molding section, 7...second transfer section, 8...discharge section, 20...opening / closing mechanism, 30...blow molding mold, 31, 32...split mold, 310, 320...cavity, 33...rod, 330...tip, 34...bottom mold, 36...nozzle, 50...preform, 51...open end, 52...mouth, 53...threaded section, 54...support ring, 55...body, 56...bottom, 560...center region, 562...lowest part, 57...skirt, 570...inner circumferential surface, 572...open end, 60...(self-supporting) container, 65...container body, H...height, O...center axis

Claims

1. 1. A method for blowing a preform in a blow mold to produce a free standing container, comprising the steps of: The preform includes a mouth portion having an open end, a substantially cylindrical body portion, a bottom portion closing an end of the body portion, and a tubular skirt portion protruding from the bottom portion, The skirt portion is provided to surround a central region of the bottom portion, The blow molding mold includes a pair of split molds having a cavity for forming a container body of the self-supporting container, a bottom mold that fits the inner peripheral surface of the skirt portion and the central region, and a rod that is inserted into the body portion from the mouth portion; The blow molding method for a self-supporting container is characterized in that before closing the set of split molds, the tip of the rod is brought into contact with the central region, and the bottom mold is brought into contact with the inner surface and the central region, so that the part where the tip is in contact is sandwiched and fixed between the tip and the bottom mold, and then the set of split molds is closed and compressed air is blown in from the mouth portion.

2. 2. The method for producing a free-standing container according to claim 1, The blow mold further includes a pair of holding dies for holding a portion of the body portion adjacent to the mouth portion and / or the mouth portion, a set of retaining dies contacting the portion and / or the mouth to hold the preform in place before the tip contacts the central region.

3. The method for producing a free-standing container according to claim 1 or 2, The method of claim 1, wherein the tip has the same shape as the inner surface of the central region.

4. The method for producing a free-standing container according to claim 1 or 2, The self-supporting container has a lowest portion on the inner surface of the bottom portion that is the lowest position when the container is self-supporting, and an open end of the skirt portion that contacts the ground when the container is self-supporting, A method for manufacturing a self-supporting container, characterized in that the vertical height from the open end to the lowest part is constant from the time the tip contacts the central region to the time the blow molding is completed.

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