JP2014028485A - Blow molding device and method for producing container made of synthetic resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a blow molding method capable of preventing suitably spill of a content fluid in a step after blow molding until capping of a container mouth part, concerning a blow molding method for performing blow molding of a preform with the content fluid.SOLUTION: A bottom mold 1B for molding a container bottom is provided on a center part with a locking part whose side face forms a tapered surface 1B_1 having a thickened end, and after blow molding, the bottom mold 1B is driven downward in the extraction direction in the state where shell molds 1SL, 1SR are closed to invert a swelled shape of the container bottom to the container outside (41B→41B'), and simultaneously an electromagnetic valve Vb is opened, to thereby introduce gas into the container 41.

Description

  TECHNICAL FIELD The present invention relates to a synthetic resin preform blow molding apparatus, and a container manufacturing method using the apparatus.

Blow-molded casings (so-called PET bottles) made of polyethylene terephthalate (PET) resin exhibit many excellent characteristics, and are therefore used in various fields as casing containers.
This type of container is generally molded by expanding and deforming a preform that has been injection-molded into a bottomed cylindrical shape in an expanded state in a state where the preform is heated to a temperature at which a stretching effect can be exhibited. .
That is, as shown in 108 (corresponding to FIG. 12 of Patent Document 1), the preform 31 heated to a temperature at which the stretching effect is exerted is protruded upward from the mouth tube portion 32, and the mouth of the preform 31. The neck ring 33 integrally provided at the lower end of the outer peripheral surface of the cylindrical portion 32 is attached to the blow mold 101 in a state where the neck ring 33 is locked to the neck support collar 103, and the guide cylindrical portion 110 which is the tip of the blow nozzle 105 is pushed. While being loosely fitted into the mouth tube portion 32 of the reform 31, it is stretched in the axial direction by the stretching rod 116 inserted through the insertion hole 111 formed through the center of the blow nozzle 105, and pressurized fluid is passed through the insertion hole 111. Stretching in the radial direction by a certain blow air to achieve the molding into the casing 41.

Patent Document 2 describes an invention relating to a method of blow molding a preform using a liquid instead of blow air as a pressurized fluid.
In such a molding method, if the content liquid finally filled in the product is used as the liquid, the filling step can be omitted and the production line can be simplified.

JP 2003-251685 A JP 2000-43129 A

Here, when using a pressurized liquid in blow molding as described in Patent Document 2, when the container is filled with liquid after molding and the blow nozzle is inserted and removed from the mouth tube portion, the liquid However, it is difficult to control the head space of the content liquid to a certain amount, and the head space varies from product to product, resulting in problems relating to merchantability.
Therefore, the present invention is a blow molding apparatus that uses a liquid that is finally filled in a product, such as beverages, cosmetics, and medicines, as a pressurized fluid. A technical problem is to suitably prevent spillage of the content liquid in the process from forming a large amount of head space to capping the container mouth after blow molding.

Among the present invention for solving the above technical problem, the means of the invention according to claim 1 is a blow molding method in which a preform is stretched and blown with a content liquid in a mold, and a container is molded.
After completion of the blow, with the barrel mold closed, the head is operated in the direction of pulling out the bottom mold of the container, and the bulge shape of the bottom of the container is reversed. It is characterized by forming a space.

  The container after completion of the blow is in a state in which the inner solution is filled therein, and is in a state in which the internal pressure of the content liquid that attempts to expand the container to the outside is loaded. In the above-mentioned configuration according to claim 1, in a state where the body mold is closed, the container is operated in a direction in which the bottom mold of the container is pulled out to reversely deform the bulge shape of the bottom of the container, and at the same time, gas is introduced into the container. By introducing into the container, it acts to form a head space in the container mouth corresponding to the volume change associated with the reverse deformation.

  According to a second aspect of the present invention, the bottom mold is provided with a portion that is hooked to the center of the bottom of the container that comes into contact with the bottom mold, and is operated in a direction in which the bottom mold is pulled out from the bottom of the container. At the same time that the bulge shape is reversed to the outside of the container, gas is introduced into the container to form a head space.

  In the said structure of Claim 2, when a bottom part mold | die is equipped with the site | part which hooks in the center part of the bottom part of a container, when the bottom part mold | die is pulled out from a container, the part to be hooked is caught in a container bottom part, and the swelling shape of a container bottom part is a container It acts so as to preferably reverse from the inside to the outside.

  According to a third aspect of the present invention, the bottom mold is provided with a thick convex portion having a tapered side surface as the catching portion, and the bottom die is pulled out from the bottom of the container. At the same time that the bulge shape of the bottom of the container is reversed to the outside of the container by operating, a gas is introduced into the container to form a head space.

  In the said structure of Claim 3, when a bottom part mold | die is equipped with the taper convex part where the side surface forms a taper surface, when the bottom part mold is pulled out from the container, the taper convex part is a container. It acts on the bottom so that the bulging shape of the bottom of the container is preferably reversed from the inside to the outside of the container.

  According to a fourth aspect of the present invention, the bottom mold includes a rod-shaped first mold that forms a central portion and a ring-shaped second mold that surrounds the central portion, and the tip of the first mold. The portion forms a convex portion with a tapered surface on the side, and is operated in the direction of pulling out the bottom mold from the bottom of the container, and at the same time the bulge shape of the bottom of the container is reversed to the outside of the container, A gas is introduced into the container to form a head space.

  In the above-described configuration of the fourth aspect, the bottom mold is pulled out in two stages to cause reverse deformation of the container bottom, and thereby the bulge shape of the container bottom is suitably reversed from the inside to the outside of the container.

  According to a fifth aspect of the present invention, the bottom mold is composed of a rod-shaped first mold that forms a central portion and a ring-shaped second mold that surrounds the central portion, and the first mold after the blow is completed. At the same time as projecting the mold against the second mold, inverting the bulge shape of the container bottom to the inside of the container, operating in the direction to pull out the first mold, inverting the bulge shape of the container bottom, A gas is introduced into the container to form a head space.

  In the above-described configuration according to the fifth aspect, unlike the means of the invention according to the first to fourth aspects, the first mold is protruded so that the bulging shape of the bottom of the container is inverted and deformed toward the inside of the container. At the same time, the gas is introduced into the container, so that a head space corresponding to the volume change associated with the reverse deformation is formed in the container mouth.

According to a sixth aspect of the present invention, there is provided a blow molding apparatus that stretches and blows a preform with a content liquid in a mold and molds the container, wherein the body mold is closed after the blow is completed. A head space is formed by introducing gas into the container at the same time as the bottom mold is operated to reverse the bulge shape of the container bottom.

  According to the above configuration of the sixth aspect, the invention of the first aspect can be suitably implemented.

  According to a seventh aspect of the present invention, the bottom mold is provided with a portion that is hooked on the bottom center of the container that comes into contact with the bottom mold, and is operated in a direction in which the bottom mold is pulled out from the bottom of the container. At the same time that the bulge shape is reversed to the outside of the container, gas is introduced into the container to form a head space.

  In the above-mentioned configuration according to the seventh aspect, the invention according to the second aspect can be suitably implemented.

  The means of the invention according to claim 8 is characterized in that the bottom mold has a thick convex portion having a tapered side surface as the catching portion, and the bottom mold is pulled out from the bottom of the container. At the same time that the bulge shape of the bottom of the container is reversed to the outside of the container by operating, a gas is introduced into the container to form a head space.

  In the above-described configuration according to the eighth aspect, the invention according to the third aspect can be suitably implemented.

  According to a ninth aspect of the present invention, the bottom mold includes a rod-shaped first mold that forms a central portion and a ring-shaped second mold that surrounds the central portion, and the tip of the first mold. The portion forms a convex portion with a tapered surface on the side, and is operated in the direction of pulling out the bottom mold from the bottom of the container, and at the same time the bulge shape of the bottom of the container is reversed to the outside of the container, A gas is introduced into the container to form a head space.

  According to the above configuration of the ninth aspect, the invention of the fourth aspect can be suitably implemented.

  According to a tenth aspect of the present invention, the bottom mold is composed of a rod-shaped first mold that forms a central portion and a ring-shaped second mold that surrounds the central portion, and the first mold after the blow is completed. At the same time as projecting the mold against the second mold, inverting the bulge shape of the container bottom to the inside of the container, operating in the direction to pull out the first mold, inverting the bulge shape of the container bottom, A gas is introduced into the container to form a head space.

  In the configuration described in claim 10, the invention described in claim 5 can be suitably implemented.

  According to the blow molding apparatus and the blow molding method using the same of the present invention, a desired amount of head space can be formed in a container obtained by blowing a preform with a content liquid in a mold. It becomes like this. This makes it possible to suitably prevent spillage of the content liquid in the process from blow molding to capping the container mouth. In addition, since the bottom shape of the container swells to the outside of the container, when the inside of the container is decompressed after capping, the bottom shape is restored, and unauthorized deformation due to decompression is suitably prevented.

It is a schematic explanatory drawing which shows an example of the whole structure of the blow molding apparatus of this invention. It is principal part sectional drawing which shows the state which mounted the preform in the metal mold | die among the shaping | molding processes by the apparatus of FIG. It is principal part sectional drawing which shows the state which made the blow nozzle communicate with the nozzle part of a preform among the shaping | molding processes by the apparatus of FIG. It is principal part sectional drawing which shows the state which extended the preform by the pressurized liquid in the expanded state among the shaping | molding processes by the apparatus of FIG. 1, and shape | molded the container. It is principal part sectional drawing which shows the state in which a head space is formed in a container opening part after extracting the bottom part metal mold | die which concerns on this invention among the shaping | molding processes by the apparatus of FIG. It is explanatory drawing which shows the blow molding method which uses the bottom part metal mold | die which concerns on the modification 1 of this invention. It is explanatory drawing which shows the blow molding method which uses the bottom part metal mold | die which concerns on the modification 2 of this invention. It is a schematic explanatory drawing which shows the other example of the whole structure of the blow molding apparatus of this invention. FIG. 9 is a cross-sectional view of an essential part showing a state in which a head space is formed in a container mouth portion after the bottom mold and the rod according to the present invention are pulled out in the molding process by the apparatus of FIG. 8. It is sectional drawing which shows the principal part of an example of the conventional blow molding apparatus.

  Hereinafter, the present invention will be described in more detail with reference to embodiments shown in the drawings.

  FIG. 1 is a schematic explanatory view showing an example of the overall configuration of an embodiment of a blow molding apparatus according to the present invention. A preform 31 mounted on a mold 1 is molded from this preform 31 by a dotted line. A solid container 41 is indicated by a solid line.

  The shape of the preform 31 to be used is a bottomed cylindrical test tube as a whole, and a mouth tube portion 32 is erected at the upper end portion, and a neck ring 33 is disposed at the lower end portion of the mouth tube portion 32, The mouth tube part 32 is mounted in the mold 1 in a state of protruding outward (upward in FIG. 1).

  The main part of this apparatus includes a mold 1, a partition member 11, and a blow nozzle 4, and includes a pressurizing device 21, a pressurized liquid supply unit 22, and a pressurized gas supply unit 23 as accessory equipment.

  The mold 1 includes a body mold 1SR, 1SL that molds the body of the container 41, and a bottom mold 1B that molds the bottom of the container 41. In particular, the bottom mold 1B is formed with a thick convex portion having a tapered surface 1B_1 having a thick side surface at the center so that the bottom mold 1B is suitably hooked to the bottom of the container 41.

  Looking at other main parts, the partition wall member 11 is arranged above the mold 1 so as to surround the outer peripheral surface of the mouth tube part 32 of the preform 31 protruding above the mold 1 through the space S. It is installed. Further, the support rod 12 provided around the lower end of the partition wall member 11 is brought into close contact with the neck ring 33 of the preform 31 from above to maintain the mounting posture of the preform 31.

The blow nozzle 4 includes an insertion cylinder piece 5 and an introduction cylinder portion 6 that are closely connected by a seal member 7b.
The fitting cylinder piece 5 is generally cylindrical, has a cylindrical hollow portion inside, and is provided with a circumferential step portion 5a whose diameter decreases toward the tip on the outer peripheral wall. The blow nozzle 4 and the mouth tube portion 32 are tightly fitted by fitting into the mouth tube portion 32 of the preform 31 and abutting the peripheral step portion 5a and the upper end surface of the mouth tube portion 32 via the seal member (O-ring) 7a. They are connected in a continuous manner.

The introduction cylinder portion 6 is formed and disposed with a through flow path 6a serving as a supply path for the pressurized liquid L so as to cross the peripheral wall at a predetermined height so as to penetrate the peripheral wall, and is pressurized by the electromagnetic valve Va. The liquid L can be supplied and stopped.
Further, a through passage 6b for communicating the outside and the inside of the introduction cylinder portion 6 is formed and disposed at a position opposite to the through passage 6a so that the communication state can be opened and closed by the electromagnetic valve Vb. Yes. In addition, a check valve (not shown) is provided in the vicinity of the fitting cylinder piece 5 of the through passage 6b so that the pressurized liquid L does not flow into the through 6b.
In the present embodiment, the electromagnetic valve Va is disposed in the through passage 6a, and the electromagnetic valve Vb is disposed in the vent hole 6b. However, other types of valves may be disposed as a matter of course.

Next, looking at the attached equipment,
The pressurizing device 21 is conventionally an essential facility in blow molding, and is a large facility such as a pressurizing pump or a compressor.
The pressurized gas supply unit 22 for supplying the pressurized gas A from the pressurizing device 21 to the pressurized liquid supply unit 22 for supplying the pressurized liquid L used for blow molding through the piping P1 or the piping P3. The pressurized fluid (driving fluid) is supplied to 23. The pressurized liquid supply unit 22 and the pressurized gas supply unit 23 are plunger pump types, and the power source uses the pressurized fluid from the above-described pressurizing device 21. Of course, in consideration of the overall layout of the device, ease of control, etc., for example, a pressurizing device for the pressurized gas supply unit 23 can be separately provided. The pressurized liquid supply unit 22 and the pressurized gas supply unit 23 may be a cylinder type with a built-in piston having two chambers in addition to the pump type such as the illustrated plunger.

  And the pressurized liquid L supplied from the pressurized liquid supply part 22 is supplied to the inside of the preform 31 through the piping P2 and the electromagnetic valve Va through the through flow path 6a of the introduction cylinder part 6.

  In the apparatus shown in FIG. 1, the pressurized gas supply unit 23 for supplying the pressurized gas A is disposed. When the pressurized liquid L is supplied to the preform 31, the pressure tube L 32 is caused by the pressure. When the gas diameter is deformed, the pressurized gas A is introduced into the partition wall member 11 via the pipe P4, and the space S surrounding the outer peripheral surface of the mouth tube portion 32 of the preform 31 is pressurized. As a result, such a diameter expansion deformation can be effectively suppressed.

Next, FIGS. 2 to 5 sequentially show molding steps for an example of the method for producing a synthetic resin container of the present invention using the apparatus shown in FIG. 1, and the present invention is described with reference to FIGS. A method for producing a synthetic resin container, that is, a blow molding method will be described.
In blow molding, the steps described in the following (1) to (5) are sequentially performed.
(1) As shown in FIG. 2, a mold 31 for blow molding is performed with a preform 31 heated to a temperature suitable for stretch blow molding except for the mouth tube portion 32 with the mouth tube portion 32 protruding upward. Attach to 1 and clamp.
(2) As shown in FIG. 3, the assembled and fixed partition wall member 11 and the blow nozzle 4 are lowered from above the mouth tube portion 32, and the tip end portion of the fitting tube piece 5 is fitted into the mouth tube portion 32.

Next, (3) as shown in FIG. 4, the pressurized liquid L is supplied into the preform 31 from the pressurized liquid supply part 22 of FIG. The reform 31 is stretched and the container 41 is shaped along the cavity 2 of the mold 1.
(4) After the container 41 is shaped as described above, the supply of the pressurized liquid L is stopped by closing the electromagnetic valve Va.
(5) As shown in FIG. 5, with the body molds 1SL and 1SR closed, the bottom mold 1B is operated in the direction of pulling out, and at the same time, the electromagnetic valve Vb is opened and gas is supplied from the outside to the container 41. The thick convex portion forming the tapered surface 1B_1 is completely pulled out from the bottom of the container. At this time, it can be seen that the swelling direction of the container bottom 41B is reversed from the inside of the container to the outside of the container. A change in volume surrounded by the bottom shape 41B before the bottom mold 1B is pulled out and the bottom shape 41B ′ after the pull-out is formed in the container mouth as the head space HS.
(6) Then, the assembled and fixed partition member 11 and the blow nozzle 4 are raised to the position shown in FIG. 2 above the mouth tube part 32, and the body molds 1SL and 1SR are further opened to open the liquid L Is taken out and the head space HS is formed, and the mouth tube part 32 is sealed with a cap (not shown) to obtain a product.

Modification 1

FIG. 6 is an explanatory view showing a blow molding method using the bottom mold 1B ′ according to the first modification of the present invention.
As shown in FIG. 6 (a), the bottom mold 1B ′ includes a rod-shaped mold 1BC in which a thick convex portion having a tapered surface 1B_1 having a thick side surface is formed at the center, and It is comprised from the ring-shaped metal mold | die 1BR which surrounds. The bottom mold 1B ′ is pulled out in two stages, unlike the bottom mold 1B.
That is, first, as shown in FIG. 6 (b), with the side molds 1SL, 1SR closed, the bottom molds 1BC, 1BR are operated in the direction of pulling out, so that the bottom shape 41B becomes the bottom shape 41B ′. Invert.

Next, as shown in FIG.6 (c), the center metal mold | die 1BC is further lowered | hung and the catching part (The thick convex part which the side surface forms the taper surface 1B_1 with a thick side) is extracted.
Then, as in the above (6), the assembled and fixed partition wall member 11 and the blow nozzle 4 are raised to the position shown in FIG. 2 above the mouth tube part 32, and the body molds 1SL and 1SR are further molded. The container 41 opened and filled with the liquid L and having the head space HS is taken out, and the mouth tube portion 32 is sealed with a cap (not shown) to obtain a product.

Modification 2

FIG. 7 is an explanatory view showing a blow molding method using the bottom mold 1B ″ according to the second modification of the present invention.
As shown in FIG. 7 (a), this bottom mold 1B '' is composed of a rod-shaped mold 1BC 'and a ring-shaped mold 1BR' surrounding it at the center.

  In the blow molding method using the bottom molds 1B and 1B ′ described above, the bottom molds 1B and 1B ′ are operated in the direction of pulling out, and the container bottom and the bottom molds 1B and 1B ′ are caught. By inverting the bulging shape to the outside of the container (41B → 41B ′) and simultaneously introducing gas into the container, it is surrounded by the bottom shape 41B before pulling out the bottom mold and the bottom shape 41B ′ after pulling out. In other words, the volume change was formed as a head space HS in the container mouth. On the other hand, in the blow molding method using the bottom mold 1B ″, as shown in FIG. 7B, the shape of the bottom of the container is reversed to the inside of the container by pushing up the central bar-shaped mold 1BC ′. Then, as shown in FIG. 7C, the bottom shape 41B before the mold 1BC ′ is pushed up by operating the mold 1BC ′ in the direction of pulling out and introducing gas into the container. And a change in volume surrounded by the bottom shape 41B ′ after the mold 1BC ′ is pushed up is formed as a head space HS in the container mouth.

  Thereafter, the assembled partition member 11 and the blow nozzle 4 are raised to the position shown in FIG. 2 above the mouth tube portion 32, and the body molds 1SL and 1SR are opened to be filled with the liquid L. The container 41 in which the head space HS is formed is taken out, and the mouth tube portion 32 is sealed with a cap (not shown) to obtain a product.

FIG. 8 is a schematic explanatory view showing another example of the overall configuration of the blow molding apparatus of the present invention.
A difference in configuration from the blow molding apparatus of FIG. 1 is that a cylindrical hollow portion is formed inside the introduction cylinder portion 6, and the blow nozzle 4 composed of the insertion cylinder piece 5 and the introduction cylinder portion 6 is included in the blow nozzle 4. A cylindrical rod 8 for demonstrating the function of forming the head space HS is inserted and arranged coaxially, and a cylindrical introduction passage Fi is formed in the blow nozzle 4 by the blow nozzle 4 and the rod 8. ing. In addition, a servo mechanism (not shown) for driving the rod 8 is disposed, and other configurations are almost the same as those of the blow molding apparatus of FIG. Therefore, hereinafter, a blow molding method using the bottom mold 1B and the rod 8 in combination will be described, focusing on the above differences.

After the step (2) described in [0039] above,
(2 ′) The tip of the rod 8 is inserted into the preform 31 with a predetermined length D (length D from the tip of the mouth tube portion 32 of the preform 31).
(3 ′) The pressurized liquid L is supplied into the preform 31 through the through channel 6 a of the introducing cylinder portion 6 through the introducing channel Fi, the preform 31 is expanded in an expanded state, and the cavity of the mold 1 is expanded. The container 41 is shaped along 2.
(4 ′) After the container 41 is shaped, the pressurized liquid L is supplied to the bottom with the electromagnetic valve Va closed and the body molds 1SL and 1SR closed as shown in FIG. While pulling out the mold 1B, the tip of the rod 8 is removed from the container 41 and pulled up to the tip of the mouth tube part 32. At the same time that the bottom mold 1B is pulled out, the electromagnetic valve Vb is opened and gas is introduced from the outside into the container 41, and the thick convex portion forming the tapered surface 1B_1 is completely removed from the container bottom. Pull out. At this time, the volume change at the bottom of the container caused by pulling out the bottom mold 1B (the portion surrounded by the bottom shape 41B and the bottom shape 41B ′) and the internal volume change portion (the rod 8 of the rod 8) generated by pulling up the rod 8 A portion corresponding to the length D) is formed in the container mouth as the head space HS.

  As described above, in the blow molding method using the bottom mold 1B and the rod 8 in combination, the volume change at the bottom of the container caused by pulling out the bottom mold 1B and the internal volume change produced by pulling up the rod 8 are included. It can be used as the head space HS. In addition, the head space HS can be controlled to a desired amount by adjusting the insertion length D into the preform 31. The bottom molds 1B 'and 1B' 'can be used in place of the bottom mold 1B.

  As described above, according to the blow molding apparatus of the present invention and the blow molding method using the same, a desired amount of head space HS is provided to the container obtained by blowing the preform with the content liquid in the mold. It becomes possible to form. As a result, in the process from blow molding to capping the container mouth, it is possible to suitably prevent spillage of the content liquid. In addition, since the bottom shape of the container swells to the outside of the container, when the inside of the container is decompressed after capping, the bottom shape is restored, and unauthorized deformation due to decompression is suitably prevented.

  The blow molding apparatus using a pressurized liquid according to the present invention easily reproduces the headspace of liquid finally filled in a product such as beverages, cosmetics, and medicines at the same time as shaping of the container with a predetermined amount. In addition, it can be adjusted reliably and is expected to be widely used in the field of blow molding.

1 Mold 1SR Right body mold 1SL Left body mold 1B, 1B ′, 1B ″ Bottom mold 1B ′ Bottom mold 1BC, 1BC ′ Rod mold 1BR, 1BR ′ Ring mold 2 Cavity 4 Blow nozzle 5 Insertion cylinder piece 5a Circumferential step part 6 Introduction cylinder part 6a Through flow path 6b Vent hole 8 Rod 7a, 7b Seal member 11 Partition member 12 Supporting flange piece 21 Pressurizing device 22 Pressurized liquid supply part 23 Pressurized gas Supply part A Pressurized gas Fi Introduction path HS Head space L (Pressurization) Liquids P1 to P4 Piping S Space Va, Vb Electromagnetic valve 31 Preform 32 Mouth tube part 33 Neck ring 41 Container 101 Mold 103 Neck support collar 104 Assembly recess 105 Blow nozzle 110 Guide tube part 111 Insertion hole 116 Rod

Claims (10)

A blow molding method in which a preform is stretched and blown with a content liquid in a mold to mold a container,
After completion of the blow, with the barrel mold closed, the head is operated in the direction of pulling out the bottom mold of the container, and the bulge shape of the bottom of the container is reversed. A blow molding method characterized by forming a space.   The bottom mold is provided with a portion that is hooked on the bottom center of the container that comes into contact with the bottom mold, and is operated in a direction in which the bottom mold is pulled out from the bottom of the container to reverse the bulge shape of the container bottom to the outside of the container. 2. The blow molding method according to claim 1, wherein a head space is formed by simultaneously introducing a gas into the container.   The bottom mold is provided with a thick convex portion having a tapered side surface as the catching portion, and is operated in a direction of pulling out the bottom mold from the bottom of the container, so that the bulging shape of the bottom of the container The blow molding method according to claim 1 or 2, wherein a head space is formed by introducing a gas into the container simultaneously with reversing the outside of the container.   The bottom mold is composed of a rod-shaped first mold that forms a central part and a ring-shaped second mold that surrounds the central part, and the tip of the first mold has a tapered surface with a thick side surface. A convex portion is formed, the head is operated in the direction of pulling out the bottom mold from the bottom of the container, and the bulge shape of the bottom of the container is reversed to the outside of the container. The blow molding method according to claim 3, wherein a space is formed.   The bottom mold is composed of a rod-shaped first mold that forms a central part and a ring-shaped second mold that surrounds the central part, and the first mold protrudes from the second mold after the blow is completed. The bulge shape at the bottom of the container is reversed to the inside of the container, and the first mold is pulled out to reverse the bulge shape at the bottom of the container. The blow molding method according to claim 1, wherein a space is formed. A blow molding device that stretches and blows a preform in a mold with the content liquid and molds the container. After the blow is completed, the body mold is closed, and the bottom mold of the container is operated in a pulling direction. A blow molding apparatus characterized in that a head space is formed by introducing a gas into the container simultaneously with reversing the bulging shape of the container bottom.   The bottom mold is provided with a portion that is hooked on the bottom center of the container that comes into contact with the bottom mold, and is operated in a direction in which the bottom mold is pulled out from the bottom of the container to reverse the bulge shape of the container bottom to the outside of the container. The blow molding apparatus according to claim 6, wherein a head space is formed by simultaneously introducing a gas into the container.   The bottom mold is provided with a thick convex portion having a tapered side surface as the catching portion, and is operated in a direction of pulling out the bottom mold from the bottom of the container, so that the bulging shape of the bottom of the container The blow molding apparatus according to claim 6 or 7, wherein a head space is formed by introducing a gas into the container simultaneously with reversing the outside of the container.   The bottom mold is composed of a rod-shaped first mold that forms a central part and a ring-shaped second mold that surrounds the central part, and the tip of the first mold has a tapered surface with a thick side surface. A convex portion is formed, the head is operated in the direction of pulling out the bottom mold from the bottom of the container, and the bulge shape of the bottom of the container is reversed to the outside of the container. The blow molding apparatus according to claim 8, which forms a space.   The bottom mold is composed of a rod-shaped first mold that forms a central part and a ring-shaped second mold that surrounds the central part, and the first mold protrudes from the second mold after the blow is completed. The bulge shape at the bottom of the container is reversed to the inside of the container, and the first mold is pulled out to reverse the bulge shape at the bottom of the container. The blow molding apparatus according to claim 6, wherein a space is formed.

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