Liquid blow molding method

Abstract

To provide liquid blow molding equipment that can easily perform air venting operations while reducing the amount of liquid discharged.SOLUTION: A liquid blow molding method for forming a liquid-filled container C from a preform 2, comprises: a nozzle engagement process for engaging a blow nozzle 23 to the mouth 2a of the preform 2; a molding process for supplying pressurized liquid L from a pressurized liquid supply 30 to the interior of the preform 2 to form the preform 2 into a predetermined container shape; a nozzle closing process for closing the blow nozzle 23 with a seal body 27 after the molding process; and a discharge process for discharging a predetermined amount of liquid L inside a supply channel 24 from the discharge port 26 to the outside of the supply channel 24 after the nozzle closing process, in a state in which the discharge port 26 is opened and a tank 31 holding the liquid L is connected to the pressurized liquid supply section 30, by supplying the pressurized liquid L from the tank 31 without operating the pressurized liquid supply section 30.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a liquid blow molding method for molding a liquid-containing container containing a content liquid from a bottomed cylindrical preform.

Background Art

[0002] Containers made of synthetic resins, such as bottles made of polypropylene (PP) or polyethylene terephthalate (PET), are used for various applications that contain various liquids, such as beverages, cosmetics, pharmaceuticals, detergents, and toiletries such as shampoo, as content liquids. Such containers are generally manufactured by blow molding a preform formed into a bottomed cylindrical shape from a synthetic resin material having the above-described thermoplasticity.

[0003] As blow molding for forming a preform into a container, liquid blow molding is known in which a pressurized liquid is used instead of pressurized air as a pressurizing medium supplied to the inside of the preform.

[0004] For example, Patent Document 1 describes a liquid blow molding method in which a preform heated in advance to a temperature at which stretchability is exhibited is set in a blow molding die, a blow nozzle is engaged with the mouth portion of the preform, and a liquid pressurized to a predetermined pressure is supplied from a pressurized liquid supply portion through the blow nozzle, thereby forming the preform into a container having a predetermined shape along the cavity of the die. According to such a liquid blow molding method, by using the content liquid that is finally contained in the container as a product, such as a beverage, as the liquid supplied to the preform, the molding of the container and the filling of the content liquid into the container can be performed simultaneously, and a liquid-containing container containing the content liquid can be easily molded. Therefore, the filling step of the content liquid into the molded container can be omitted, and the production process and the configuration of the production line (apparatus) can be simplified.

Prior Art Documents

Patent Documents

[0005] Patent Document 1 Japanese Patent Application Laid-Open No. 2017-196872 Summary of the Invention Problems to be Solved by the Invention

[0006] In liquid blow molding, since a pressurized liquid is filled into a preform for molding, if a gas such as air enters the supply path of the nozzle unit connected to the blow nozzle, the pressure of the liquid will not increase sufficiently, resulting in a decrease in moldability and problems such as instability in the amount of liquid to be filled. In particular, when the liquid is replaced, gas such as air is likely to enter the supply path. Also, when a suck-back process is performed to form a head space inside the container after molding, the liquid that has entrained air during liquid blow molding will be sucked back into the supply path during suck-back, so air will gradually accumulate in the supply path.

[0007] In contrast, before starting liquid blow molding or at a predetermined frequency, it is conceivable to perform an air bleeding operation by closing the seal body that closes the blow nozzle and operating the pressurized liquid supply unit with the discharge pipe connected to the supply path of the nozzle unit open, so that the liquid mixed with air inside the supply path is discharged to the outside through the discharge pipe.

[0008] However, in the above conventional method, since air easily accumulates in the pipes connecting the nozzle unit and the pressurized liquid supply unit, and the discharge pipes connected to the supply path, etc., it is necessary to apply a large pressure to the liquid inside the supply path by the pressurized liquid supply unit during the air bleeding operation, which makes the air bleeding operation complicated and results in a problem that a large amount of liquid is wasted and discharged to the outside.

[0009] The present invention has been made in view of such problems, and an object thereof is to provide a liquid blow molding method capable of easily performing an air bleeding operation while reducing the amount of liquid to be discharged. Means for Solving the Problems

[0010] The liquid blow molding method of the present invention is a liquid blow molding method for molding a liquid-containing container containing a content liquid from a bottomed cylindrical preform, comprising: a nozzle engagement step of engaging a blow nozzle connected to a pressurized liquid supply unit via a supply path with a mouth portion of the preform; a molding step of supplying a pressurized liquid from the pressurized liquid supply unit through the supply path and the blow nozzle into the preform to mold the preform into a container having a predetermined shape; a nozzle closing step of closing the blow nozzle with a seal body after the molding step; and a discharging step of opening a discharge port connected to the supply path and communicating a tank for storing a liquid with the pressurized liquid supply unit after the nozzle closing step, and supplying a pressurized liquid from the tank to discharge a predetermined amount of the liquid inside the supply path to the outside of the supply path without operating the pressurized liquid supply unit.

[0011] In the liquid blow molding method of the present invention, in the above configuration, it is preferable that the tank stores a pressurized liquid.

[0012] In the liquid blow molding method of the present invention, in the above configuration, it is preferable to supply pressurized air into the tank to pressurize the liquid stored in the tank.

[0013] In the liquid blow molding method of the present invention, in the above configuration, after the nozzle closing step and before the discharging step, it is preferable to perform a filling step of communicating the tank with the pressurized liquid supply unit and filling the pressurized liquid supply unit with a liquid to be used in the next molding step.

[0014] In the liquid blow molding method of the present invention, in the above configuration, after the molding step and before the nozzle closing step, it is preferable to perform a suck-back step of operating the pressurized liquid supply unit in the reverse direction to suck back a predetermined amount of the liquid from inside the container molded into a predetermined shape in the molding step into the supply path.

[0015] In the liquid blow molding method of the present invention, in the above configuration, in the molding step, the preform is axially stretched by a stretching rod, and after the nozzle closing step, it is preferable to pull out the stretching rod from the container molded into a predetermined shape in the molding step.

[0016] In the liquid blow molding method of the present invention, in the above configuration, it is preferable to supply the liquid stored in the sub-tank to the tank.

Effect of the Invention

[0017] According to the present invention, it is possible to provide a liquid blow molding apparatus capable of easily performing the air venting operation while reducing the amount of liquid discharged.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0019] Hereinafter, the present invention will be more specifically illustrated with reference to the drawings.

[0020] The liquid blow molding method of the present invention is a liquid blow molding method for molding a liquid-containing container containing a content liquid from a bottomed cylindrical preform, comprising a nozzle engagement step of engaging a blow nozzle connected to a pressurized liquid supply section via a supply path with the mouth portion of the preform, a molding step of supplying a pressurized liquid from the pressurized liquid supply section through the supply path and the blow nozzle into the preform to mold the preform into a container having a predetermined shape, a nozzle closing step of closing the blow nozzle with a seal body after the molding step, and a discharging step of opening a discharge port connected to the supply path and discharging a predetermined amount of the liquid inside the supply path to the outside of the supply path with a tank for storing the liquid in a pressurized state communicated with the pressurized liquid supply section without operating the pressurized liquid supply section. For example, it can be implemented using a liquid blow molding apparatus 1 having the configuration shown in FIG. 1.

[0021] The liquid blow molding apparatus 1 shown in FIG. 1 molds a preform 2 into a liquid-containing container containing a content liquid inside by liquid blow molding. Note that liquid blow molding is blow molding performed using a pressurized liquid instead of the pressurized air used in air blow molding as a pressurized medium (pressurized fluid) supplied to the preform 2.

[0022] As the liquid L supplied to the preform 2, that is, the content liquid L accommodated in the liquid-containing container after molding, various liquids such as beverages, cosmetics, pharmaceuticals, detergents, and toiletries such as shampoo can be used.

[0023] As the preform 2, for example, a bottomed cylindrical one formed of a synthetic resin material having thermoplasticity such as polypropylene (PP) or polyethylene terephthalate (PET), having a cylindrical mouth portion 2a serving as an open end and a cylindrical body portion 2b connected to the mouth portion 2a and having a closed lower end, is used.

[0024] Note that the preform 2 is not limited to the above shape, and any shape can be used as long as it is a bottomed cylindrical shape, depending on the shape of the container after molding and the like.

[0025] Although not shown in detail, an engaging projection is provided on the outer wall surface of the mouth portion 2a for attaching a closing cap (not shown) to the mouth portion 2a of the liquid-filled container after molding by undercut engagement. Note that instead of the engaging projection, a male thread may be provided on the outer wall surface of the mouth portion 2a so that the closing cap can be attached to the mouth portion 2a by screw connection.

[0026] The liquid blow molding apparatus 1 has a mold 10 for blow molding. The mold 10 has a cavity 11 having a shape corresponding to the final shape of a container such as a bottle shape. The cavity 11 opens upward on the upper surface of the mold 10. The preform 2 is mounted on the mold 10 in a state where the body portion 2b is disposed inside the cavity 11 of the mold 10 and the mouth portion 2a protrudes upward from the mold 10.

[0027] The mold 10 can be opened and closed left and right, and after molding the preform 2 into a liquid-filled container, the mold 10 is opened left and right to remove the liquid-filled container from the mold 10.

[0028] Above the mold 10, a nozzle unit 20 for supplying the liquid L into the preform 2 is provided. The nozzle unit 20 has a main body block 21, and the main body block 21 is movable relative to the mold 10 in the vertical direction. A support block 22 is provided at the lower end of the main body block 21, and a blow nozzle 23 is mounted at the lower end of the main body block 21 supported by the support block 22. The blow nozzle 23 is formed in a substantially cylindrical shape and engages with the mouth portion 2a of the preform 2 mounted on the mold 10 from above when the main body block 21 descends to the lower stroke end.

[0029] Inside the main body block 21, a supply path 24 extending in the vertical direction is provided. The supply path 24 is a flow path for supplying the liquid L to the blow nozzle 23, and communicates with the blow nozzle 23 at its lower end. Further, the main body block 21 is provided with a supply port 25 communicating with the central portion in the vertical direction of the supply path 24 and a discharge port 26 communicating with the upper end portion of the supply path 24.

[0030] Inside the supply path 24, a seal body 27 for opening and closing the blow nozzle 23 is arranged. The seal body 27 is fixed to the lower end of a shaft body 28 movably provided in the vertical direction on the nozzle unit 20, and is movable in the vertical direction inside the supply path 24. The seal body 27 is formed in a cylindrical shape, and when it moves to the closed position which is the lower stroke end position, it abuts against the upper surface of the blow nozzle 23 at the lower end surface to close the blow nozzle 23. On the other hand, when the seal body 27 moves upward from the closed position, the blow nozzle 23 is opened and communicated with the supply path 24.

[0031] As shown in the figure, the liquid blow molding apparatus 1 can also be configured to include a stretching rod 29. The stretching rod 29 is inserted into the axial center of the shaft body 28 so as to be relatively movable in the vertical direction with respect to the shaft body 28, and is provided so as to penetrate the axial center of the seal body 27 and be able to protrude and retract from the lower end of the seal body 27. The stretching rod 29 is driven by a drive source (not shown) to move downward, whereby the preform 2 can be stretched in the axial direction. Thus, when configured to include the stretching rod 29, the liquid blow molding apparatus 1 can perform biaxial stretch blow molding in which the preform 2 is stretched in the axial direction by the stretching rod 29 and in the radial direction by the pressurized liquid L supplied from the mouth portion 2a. Note that the liquid blow molding apparatus 1 can also be configured not to include the stretching rod 29.

[0032] A pressurized liquid supply unit 30 is connected to the supply port 25 by a pipe P1. The pressurized liquid supply unit 30 can be configured by, for example, a plunger pump including a cylinder 30a and a plunger 30b. When the pressurized liquid supply unit 30 operates, the pressurized liquid L is supplied to the blow nozzle 23 through the pipe P1 and the supply passage 24. A pressure gauge PG1 for measuring the pressure of the liquid L inside the pipe P1 is provided in the pipe P1.

[0033] A tank 31 is connected to the pressurized liquid supply unit 30 by a pipe P2. The tank 31 stores the liquid L to be supplied to the pressurized liquid supply unit 30 and supplies the liquid L to the pressurized liquid supply unit 30 in a pressurized state. In the present embodiment, the tank 31 is a sealed container, and pressurized air is supplied into the tank 31 from a pressurized air supply unit 32 as a pressurizing means, so that the liquid L stored inside is pressurized. The inside of the tank 31 only needs to be in a pressurized state necessary for performing the discharge process during the discharge process described later, and may be in a non-pressurized state or in a lower pressurized state other than during the discharge process. Further, the inside of the tank 31 may always be in a constant pressurized state. In this case, a pressure gauge PG2 for measuring the pressure inside the tank 31 is provided in the tank 31, and the operation of the pressurized air supply unit 32 is controlled so that the pressure measured by the pressure gauge PG2 falls within a predetermined range set according to the viscosity of the liquid L or the like. Note that a pressurizing means having a configuration different from that of the pressurized air supply unit 32 may be used to pressurize the liquid L inside the tank 31 and supply the liquid L to the pressurized liquid supply unit 30 in a pressurized state. The tank 31 may be arranged at a position higher than the discharge port 26, and the liquid L may be supplied to the pressurized liquid supply unit 30 in a pressurized state by the weight of the liquid L. A pump may be provided in the pipe P2 between the tank 31 and the pressurized liquid supply unit 30, and the liquid L may be pumped from the tank 31 to the pressurized liquid supply unit 30 by the pump to supply the liquid L to the pressurized liquid supply unit 30 in a pressurized state.

[0034] The pipe P2 is provided with an on-off valve V1. When the on-off valve V1 is opened, the liquid L inside the tank 31 is supplied to the pressurized liquid supply unit 30 in a pressurized state through the pipe P2. Note that the tank 31 can also be configured to heat the liquid L to a predetermined temperature and maintain it at that temperature.

[0035] The discharge port 26 has a discharge pipe P3 connected thereto. The pipe P3 is provided with an on-off valve V2, and the on-off valve V2 can open and close the pipe P3 and the discharge port 26.

[0036] When the seal body 27 moves upward to open the blow nozzle 23 and the on-off valves V1 and V2 are closed, the pressurized liquid supply unit 30 operates in the forward direction (pressurizing direction) to supply the liquid L pressurized to a predetermined pressure to the inside of the preform 2 through the pipe P1, the supply port 25, the supply path 24, and the blow nozzle 23. Further, when the blow nozzle 23 is blocked by the seal body 27, the on-off valve V2 is closed, and the on-off valve V1 is opened, the pressurized liquid supply unit 30 operates in the reverse direction (suction direction) to suck the liquid L accommodated in the tank 31 into the inside of the cylinder 30a.

[0037] On the other hand, when the on-off valves V1 and V2 are opened without operating the pressurized liquid supply unit 30 while the blow nozzle 23 is closed by the seal body 27, the liquid L stored in the tank 31 is supplied to the supply path 24 in a pressurized state through the pressurized liquid supply unit 30, the pipe P1, and the supply port 25, so that the liquid L inside the supply path 24 is discharged to the outside through the discharge port 26 and the pipe P3.

[0038] The operations of the nozzle unit 20, the seal body 27, the extension rod 29, the pressurized liquid supply unit 30, the on-off valve V1, the on-off valve V2, the pressurized air supply unit 32, etc. are integrally controlled by a control device (not shown). This control can be performed by referring to the value of the pressure gauge PG1. Note that the on-off valves V1 and V2 are preferably configured as solenoid valves that can be controlled by the control device.

[0039] Next, a method of forming a liquid-containing container C in which a content liquid is contained inside a container having a predetermined shape from a bottomed cylindrical preform 2 using the liquid blow molding apparatus 1 having such a configuration (the liquid blow molding method of the present invention) will be described.

[0040] First, as shown in FIG. 1, the preform 2 that has been previously heated to a predetermined temperature (for example, 80°C to 150°C) to exhibit stretchability using a heating means (not shown) such as a heater is attached to the blow molding die 10 and clamped.

[0041] When the preform 2 is attached to the die 10, next, the nozzle engagement step is performed. In the nozzle engagement step, the nozzle unit 20 is lowered toward the die 10, and the blow nozzle 23 connected to the pressurized liquid supply unit 30 via the supply path 24 is engaged with the mouth portion 2a of the preform 2. FIG. 2 shows a state in which the nozzle engagement step is completed. In the state where the nozzle engagement step is completed, the seal body 27, the on-off valve V1, and the on-off valve V2 are all closed, and the extension rod 29 is held in the original position where it does not protrude downward from the blow nozzle 23.

[0042] When the nozzle engagement step is completed, next, the molding step is performed. In the molding step, as shown in FIG. 3, with the on-off valve V1 and the on-off valve V2 closed, the seal body 27 is opened, and in this state, the pressurized liquid supply unit 30 is operated in the forward direction (pressurizing direction). As a result, the liquid L pressurized to a predetermined pressure is supplied from the pressurized liquid supply unit 30 into the preform 2 through the pipe P1, the supply path 24, and the blow nozzle 23, and the preform 2 is liquid blow molded by the pressure of the liquid L. In this molding step, as shown in FIG. 3, the preform 2 is molded until it becomes a liquid-containing container C having a predetermined shape along the cavity 11. When the preform 2 is molded into the liquid-containing container C shown in FIG. 3, the molding step is completed.

[0043] When a stretching rod 29 is provided in the liquid blow molding apparatus 1, in the molding process, the stretching rod 29 can be advanced downward, and the preform 2 can be stretched in the axial direction (vertical direction) by the stretching rod 29. Thereby, biaxial stretch blow molding can be performed in which the preform 2 is formed in two axial directions by the pressure of the liquid L and the stretching rod 29. According to the biaxial stretch blow molding, the preform 2 can be more accurately formed into a liquid-containing container C having a predetermined shape.

[0044] After the molding process is completed, a suck-back process may be performed. In the suck-back process, the on-off valves V1 and V2 are closed, and the pressurized liquid supply unit 30 is operated in the reverse direction with the seal body 27 open, so that a predetermined amount of the liquid L is sucked back (suck-back) from the inside of the liquid-containing container C formed into a predetermined shape in the molding process to the supply path 24. The amount of the liquid L sucked back into the supply path 24 in the suck-back process is appropriately set so that the head space HS provided inside the liquid-containing container C after completion becomes a predetermined amount. When the suck-back process is performed, the liquid-containing container C is in a volume-reduced deformed state in which its internal volume is reduced by the amount of the liquid L sucked back to the supply path 24 in the suck-back process, and a gap is generated between the cavity 11.

[0045] When a predetermined amount of the liquid L is sucked back from the liquid-containing container C to the supply path 24 in the suck-back process, next, a nozzle closing process is performed. In the nozzle closing process, as shown in FIG. 4, with a predetermined amount of the liquid L sucked back from the inside of the liquid-containing container C formed into a predetermined shape in the suck-back process to the supply path 24, the blow nozzle 23 is closed by the seal body 27. After the nozzle closing process, the nozzle unit 20 is raised to separate the blow nozzle 23 from the mouth portion of the molded liquid-containing container C, so that air flows into the liquid-containing container C from the mouth portion, and a head space HS is formed inside the liquid-containing container C as shown in FIGS. 5 and 6.

[0046] When a stretching rod 29 is provided in the liquid blow molding apparatus 1, after the nozzle closing step, it is preferable to pull out the stretching rod 29 from the liquid-containing container C formed in the molding step. Thereby, the internal volume of the liquid-containing container C can be decreased by the volume of the stretching rod 29, and a head space HS can be provided inside the liquid-containing container C. In this case, the amount of the liquid L sucked back from the inside of the liquid-containing container C into the supply path 24 in the suck-back step is set in consideration of the decrease in the internal volume caused by pulling out the stretching rod 29 from the liquid-containing container C.

[0047] Note that, as a configuration not performing the suck-back step, a head space HS may be provided inside the liquid-containing container C only by pulling out the stretching rod 29, or a head space HS may be provided inside the liquid-containing container C only by the suck-back step without providing the stretching rod 29.

[0048] After the nozzle closing step is completed, a filling step may be performed. In this case, as shown in FIG. 5, with the seal body 27 and the on-off valve V2 closed, the on-off valve V1 is opened to communicate the tank 31 with the pressurized liquid supply unit 30, and in this state, the pressurized liquid supply unit 30 is operated in the reverse direction (suction direction) to suck the liquid L stored in the tank 31 into the inside of the pressurized liquid supply unit 30 as the liquid L to be used in the next molding step. The amount of the liquid L sucked by the pressurized liquid supply unit 30 is appropriately set according to the capacity of the liquid-containing container C after molding. Note that the filling step may be performed after the discharge step described later.

[0049] When the nozzle closing step and the filling step are completed, a discharge step is then performed. In the discharge step, as shown in FIG. 6, with the seal body 27 closed, the on-off valve V1 and the on-off valve V2 are opened to communicate the tank 31 storing the liquid L with the pressurized liquid supply unit 30 and to open the discharge port 26 connected to the supply path 24. Thereby, without operating the pressurized liquid supply unit 30, the liquid L inside the supply path 24 is pressurized by the liquid L supplied from the tank 31 in a pressurized state and discharged outside the supply path 24 from the discharge port 26 by a predetermined amount.

[0050] Here, in the molding step of supplying the pressurized liquid L into the preform 2 to mold the liquid-containing container C having a predetermined shape, since the liquid L is supplied into the preform 2 while entraining the gas (air) present inside the preform 2, there is a possibility that the liquid L containing bubbles enters the inside of the supply path 24. Further, when the liquid is replaced, gas such as air is likely to be mixed into the supply path. Furthermore, when the suck-back step is performed, the liquid L containing bubbles is taken into the inside of the supply path 24. Since liquid blow molding is performed by filling the preform 2 with the pressurized liquid L, if gas such as air enters the supply path 24 of the nozzle unit 20 connected to the blow nozzle 23, problems such as the pressure of the liquid L not increasing sufficiently and the moldability decreasing, and the amount of the liquid to be filled becoming unstable will occur.

[0051] On the other hand, in the liquid blow molding method of the present embodiment, since the discharge step is performed after the molding step is completed and the nozzle closing step is performed, the liquid L containing gas such as air accumulated inside the supply path 24 can be discharged from the discharge port 26 to the outside of the supply path 24. That is, so-called air bleeding for discharging the gas such as air inside the supply path 24 to the outside can be performed by the discharge step. Thereby, it is possible to prevent the liquid L containing a large amount of bubbles from being supplied into the preform 2 in the next molding step, stabilize the filling amount and filling pressure of the liquid L into the molded liquid-containing container C, and accurately mold the liquid-containing container C.

[0052] In the discharge step, the amount of the liquid L discharged from the discharge port 26 to the outside of the supply path 24 can be appropriately set. However, in the case of a configuration in which the suck-back step is performed, it is preferable to discharge the same amount of the liquid L as the liquid L sucked back into the supply path 24 in the suck-back step from the discharge port 26 to the outside of the supply path 24. Thereby, it is possible to surely discharge the liquid L containing bubbles sucked back into the inside of the supply path 24 in the suck-back step to the outside of the supply path 24, and it becomes possible to more accurately mold the liquid-containing container C.

[0053] In the case of illustration, since the discharge port 26 is provided on the upper end side of the supply path 24, the liquid L containing bubbles can be effectively discharged from the discharge port 26 to the outside of the supply path 24. Note that, for example, when the liquid L has a relatively high viscosity such as shampoo or liquid detergent, and the bubbles mixed in the liquid L slowly float upward inside the supply path 24, the position where the discharge port 26 is provided can be variously changed, such as providing the discharge port 26 at the vertical center of the supply path 24.

[0054] Also, in the present embodiment, since the liquid is stored in the tank 31 in a pressurized state so that the pressurized liquid L is supplied from the tank 31 to the pressurized liquid supply unit 30, the pressurized state of the liquid L can be easily set to a pressure suitable for performing the discharge process.

[0055] Furthermore, in the present embodiment, since pressurized air is supplied into the tank 31 to put the liquid L stored in the tank 31 in a pressurized state, the pressurized state of the liquid L can be set more easily to a pressure suitable for performing the discharge process.

[0056] In the present embodiment, as shown in FIGS. 5 and 6, the filling process and the discharge process are performed by moving the nozzle unit 20 upward and pulling out the blow nozzle 23 from the mouth portion 2a of the liquid-containing container C after molding (since the mouth portion 2a of the preform 2 has the same shape, the same reference numeral is given). However, as long as it is after the nozzle blocking process, the filling process and the discharge process may be performed while the blow nozzle 23 is engaged with the mouth portion 2a of the liquid-containing container C.

[0057] Note that the discharging process is not performed in all cycles when sequentially forming a plurality of liquid-containing containers C. Instead, in the forming process of the repeatedly performed cycles, the filling pressure of the liquid L into the preform 2 is measured by the pressure gauge PG1. When the measured filling pressure drops below a predetermined ratio, it is determined that a gas such as air in a predetermined amount or more has accumulated in the supply path 24, and the discharging process can be configured to be performed in that cycle. With such a configuration, it is possible to prevent a wasteful discharging process from being performed, and to efficiently and accurately manufacture a plurality of liquid-containing containers C.

[0058] Also, the inside of the tank 31 is preferably kept under pressure not only during the discharging process but also constantly. Thereby, the liquid L in the supply path 24 can be pressurized by the pressure of the liquid L inside the tank 31 during the discharging process and discharged from the discharge port 26, and the operation of the pressurized air supply unit 32 can be stopped after the completion of the discharging process and started during the next discharging process, eliminating the need for a process, and improving the operation efficiency and yield rate of the equipment.

[0059] When the forming of the liquid-containing container C is completed by the above process, a cap is attached to the mouth portion 2a of the liquid-containing container C by a capping device (not shown). Then, the mold 10 is opened and the completed liquid-containing container C is taken out of the mold 10. Note that the cap may be attached after taking out the liquid-containing container C from the mold. Then, the next preform 2 is placed in the mold 10, and hereinafter, the same processes as above are repeatedly performed to sequentially form the liquid-containing containers C.

[0060] As described above, according to the liquid blow molding method of the present invention, since the gas such as air accumulated in the supply path 24 can be discharged outside the supply path 24 from the discharge port 26, it is possible to prevent the liquid L containing a large amount of bubbles from being supplied into the preform 2 in the next forming process, and to accurately mold the liquid-containing container C.

[0061] In particular, when the sack-back process is performed, many bubbles will enter the supply path 24. However, even in such a case, the liquid L with bubbles sucked back into the supply path 24 can be reliably discharged from the discharge port 26 to the outside of the supply path 24, and the liquid-containing container C can be accurately molded.

[0062] Furthermore, when a configuration is adopted in which, after the nozzle clogging process and before the discharging process, the tank 31 is communicated with the pressurized liquid supply unit 30 to perform a filling process of filling the pressurized liquid supply unit 30 with the liquid L to be used in the next molding process, the liquid such as air mixed in the liquid L in the filling process can be discharged to the outside in the discharging process. Therefore, the liquid-containing container C can be molded with higher accuracy.

[0063] By adopting a configuration in which pressurized air is supplied into the tank 31 to put the liquid L stored in the tank 31 in a pressurized state, the liquid L in the tank 31 can be put in a pressurized state to such an extent that the discharging process can be performed with a simple configuration. Therefore, the cost of the equipment can be reduced.

[0064] As illustrated as a modification example in FIG. 7, the liquid blow molding method of the present embodiment may also adopt a configuration in which the liquid L stored in the sub-tank 40 is supplied to the tank 31 by a pump 41 or the like. In this case, the sub-tank 40 is connected to the tank 31 by a pipe P4, the pump 41 is arranged in the pipe P4, and the liquid L stored in the sub-tank 40 is always supplied to the tank 31 by the pump 41. Note that, without using the pump 41, the sub-tank 40 may be arranged above the tank 31, and the liquid L inside the sub-tank 40 may be supplied to the tank 31 by its own weight.

[0065] Even with such a configuration, in the discharging process, the liquid L in the supply path 24 can be discharged from the discharge port 26 to the outside of the supply path 24 by the pressure of the liquid L stored in the tank 31 in a pressurized state.

[0066] In addition, in order to change the type of the liquid L, i.e., the content liquid L, stored in the liquid-containing container C, the sub-tank 40 may be configured to be detachable from the production line by disconnecting it from the pipe P4. However, in the configuration of the above-described modification, since it is not necessary to provide a pressurizing means such as the pressurized air supply unit 32 in the sub-tank 40, the operation of changing the type of the liquid L can be easily performed in terms of control (such as circuit connection).

[0067] Needless to say, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the invention.

[0068] For example, in the above-described embodiment, the case where the liquid blow molding method of the present invention is performed using the liquid blow molding apparatus 1 having the configuration shown in FIG. 1 is shown. However, the liquid blow molding method of the present invention can also be performed using a liquid blow molding apparatus or the like having another configuration.

[0069] Further, in the above-described embodiment, in the molding step, biaxial stretch blow molding is performed using the stretch rod 29, and after the nozzle closing step, the stretch rod 29 is pulled out from the liquid-containing container C to form the head space HS. However, a configuration may be adopted in which stretching by the stretch rod 29 or pulling out for forming the head space HS is not performed.

[0070] Furthermore, in the above-described embodiment, the pressurized liquid supply unit 30 is a plunger pump. However, the present invention is not limited to this, and various configurations can be used as long as the liquid L can be pressurized to a predetermined pressure and supplied to the preform 2.

Explanation of Reference Numerals

[0071] 1 Liquid blow molding apparatus 2 Preform 2a Mouth part 2b Body part 10 Mold 11 Cavity 20 Nozzle unit 21 Main body block 22 Support Block 23 Nozzle 24 Supply Path 25 Supply Port 26 Discharge Port 27 Sealing Body 28 Shaft Body 29 Extension Rod 30 Pressurized Liquid Supply Section 30a Cylinder 30b Plunger 31 Tank 32 Pressurized Air Supply Section 40 Sub - Tank 41 Pump L Liquid (Content Liquid) P1 Pipe PG1 Pressure Gauge P2 Pipe PG2 Pressure Gauge V1 On - Off Valve P3 Pipe V2 On - Off Valve C Container with Liquid P4 Pipe

Claims

1. A liquid blow molding method for molding a liquid-filled container containing a content liquid from a bottomed cylindrical preform, comprising: a nozzle engagement step of engaging a blow nozzle connected to a pressurized liquid supply unit via a supply path with a mouth portion of the preform; a molding step of supplying a pressurized liquid from the pressurized liquid supply unit into the preform through the supply path and the blow nozzle to mold the preform into a container having a predetermined shape; a nozzle closing step of closing the blow nozzle with a sealing body after the molding step; a discharging step of opening a discharge port connected to the supply path after the nozzle closing step, and supplying a pressurized liquid from a tank for storing the liquid while communicating the tank with the pressurized liquid supply unit, and discharging a predetermined amount of the liquid inside the supply path from the discharge port to the outside of the supply path without operating the pressurized liquid supply unit. The liquid blow molding method is characterized by comprising the above steps.

2. The liquid blow molding method according to claim 1, wherein the tank stores a pressurized liquid.

3. The liquid blow molding method according to claim 2, wherein pressurized air is supplied into the tank to pressurize the liquid stored in the tank.

4. The liquid blow molding method according to any one of claims 1 to 3, wherein after the nozzle closing step and before the discharging step, a filling step is performed in which the tank is communicated with the pressurized liquid supply unit to fill the pressurized liquid supply unit with the liquid to be used in the next molding step.

5. The liquid blow molding method according to any one of claims 1 to 4, wherein after the molding step and before the nozzle closing step, a suck-back step is performed in which the pressurized liquid supply unit is operated in the reverse direction to suck back a predetermined amount of the liquid from the inside of the container molded into a predetermined shape in the molding step into the supply path.

6. In the molding step, the preform is axially stretched by a stretching rod, and after the nozzle closing step, the stretching rod is pulled out from the container molded into a predetermined shape in the molding step. The liquid blow molding method according to any one of claims 1 to 5.

7. The liquid blow molding method according to any one of claims 1 to 6, wherein the liquid stored in the sub-tank is supplied to the tank.

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