Injection blowing forming method

Abstract

The present invention provides an injection blow molding method that allows the preform temperature to be set to a temperature at which it can be demolded and at which it expands when air is blown into it. [Solution] An injection blow molding method comprising: an injection step of molding a preform on the inner surfaces of a male mold part, a female mold part, and a gripping mold part; a demolding step of separating the preform from the female mold part and the male mold part while the gripping mold part is gripping the preform; and a blowing step of blowing air into the preform while the gripping mold part is gripping it, wherein in the demolding step, the male mold part is separated from the preform before the preform separates from the female mold part.

Description

Technical Field

[0001] The present invention relates to an injection blow molding method.

Background Art

[0002] For example, the apparatus described in Patent Document 1 is provided on a machine table with, roughly speaking, a preform molding station, a blow molding station, and a transfer station located between the preform molding station and the blow molding station. The preform molding station has injection core molds at two locations separated by a rotation angle of 180°, and has a turntable that intermittently circulates and conveys the injection core molds along a rotary conveyance path. And at each stop position of the injection core mold, an injection molding part is provided at a position facing an injection device, and a take-out part is provided facing this injection molding part. The injection molding part has an injection cavity mold that is driven to clamp relative to the injection core mold, and simultaneously injects and molds, for example, four preforms. The neck part of the preform is molded by a neck cavity mold, and the preform is held by this neck cavity mold and the injection core mold and conveyed to the take-out part by the turntable. And at the take-out part, after partial mold release from the injection core mold, the preform is taken out by releasing the preform from the neck cavity mold. Further, the apparatus described in Patent Document 1 is provided with a receiving part that receives a preform from the transfer station, a heating part that heats the preform received by the receiving part to a temperature not lower than the suitable temperature for blow molding, a blow molding part that performs stretch blow molding on the preform heated by the heating part to obtain a container, and a container take-out part that takes out the container blow molded by the blow molding part to the outside of the apparatus.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the apparatus described in Patent Document 1, multiple preforms are simultaneously injection molded, the preforms are cooled by an injection core mold, and after the preforms have cooled to a temperature at which they can be removed, they are removed from the injection core mold in the removal section. Furthermore, before blow molding in the blow molding section, the preforms are heated to a temperature above the suitable temperature for blow molding in the heating section. On the other hand, in devices that do not have a heating section for heating the preform, it is desirable to set the temperature of the molded preform to a temperature that allows for demolding and also allows for expansion when air is blown into it. The present invention aims to provide an injection blow molding method that allows the temperature of the preform to be set to a temperature at which it can be demolded and at which it expands when air is blown into it. [Means for solving the problem]

[0005] The present invention, completed with this objective in mind, is an injection blow molding method comprising: an injection step of molding a preform on the inner surfaces of a male mold, a female mold, and a gripping mold; a demolding step of separating the preform from the female mold and the male mold while the gripping mold is gripping the preform; and a blowing step of blowing air into the preform while it is being gripped by the gripping mold, wherein in the demolding step, the male mold is separated from the preform before the preform separates from the female mold. Here, the temperature of the body of the preform after the demolding step and before the blowing step may be higher than the temperature of the tip of the preform. Alternatively, the temperature of the body of the preform may be set to 90°C or higher and less than 120°C, and the temperature of the tip of the preform may be set to 70°C or higher and less than 100°C. Alternatively, the temperature of the body of the preform may be set to 100°C or higher and less than 110°C, and the temperature of the tip of the preform may be set to 80°C or higher and less than 90°C. Furthermore, in the injection molding process, the thickness of the tip portion of the preform may be increased compared to the thickness of the body portion of the preform. [Effects of the Invention]

[0006] According to the present invention, the temperature of the preform can be set to a temperature at which it can be demolded and at which it expands when air is blown into it. [Brief explanation of the drawing]

[0007] [Figure 1] This is a view in the vertical direction of an example of a cross-section of an injection molding machine according to an embodiment. [Figure 2] This is a view in a second direction showing an example of a cross-section of an injection molding machine according to the embodiment. [Figure 3] (a) is a diagram showing an example of a cross-section of the preform before molding. (b) is a diagram showing an example of a cross-section of the preform after molding. [Figure 4] (a) is a diagram showing an example of a cross-section of the final molded product before molding. (b) is a diagram showing an example of a cross-section of the final molded product after molding. [Figure 5] This figure shows an example of an injection molding method. [Figure 6] This figure shows an example of a mold release process according to the embodiment. [Figure 7] This figure shows an example of a mold release process related to a comparative example. [Figure 8] This figure shows an example of the relationship between the temperature of the body and tip of the preform after the transition process and the quality of the final molded product. [Modes for carrying out the invention]

[0008] Embodiments of the present invention will be described in detail below with reference to the attached drawings. Figure 1 is a view in the vertical direction of an example of a cross-section of an injection blow molding machine 1 according to an embodiment. Figure 2 is a view of an example of a cross-section of the injection blow molding machine 1 according to the embodiment, as seen in a second direction. Figure 3(a) shows an example of a cross-section of the preform 610 before molding. Figure 3(b) shows an example of a cross-section of the preform 610 after molding. Figure 4(a) shows an example of a cross-section of the final molded product 600 before molding. Figure 4(b) shows an example of a cross-section of the final molded product 600 after molding. Figures 1 and 2 show the mold after it has been opened.

[0009] The injection and blow molding machine 1 is a device that performs injection molding (in other words, injection molding) and blow molding (in other words, blow molding). The injection and blow molding machine 1 forms an intermediate molded product, such as a test tube-shaped preform 610, by injection molding, and then forms a final molded product 600, such as a container, by blow molding, which involves blowing air at a pressure sufficient to expand the preform into the interior of the preform 610 and causing it to expand.

[0010] The injection molding machine 1 comprises a fixed mold 10, a movable mold 20 that is movable relative to the fixed mold 10, and an intermediate mold 30 positioned between the fixed mold 10 and the movable mold 20. The injection molding machine 1 performs injection molding at the injection station between the fixed mold 10 and the intermediate mold 30 by closing the molds of the fixed mold 10 and the intermediate mold 30. The injection molding machine 1 also performs blow molding at the blow station between the intermediate mold 30 and the movable mold 20 by closing the molds of the intermediate mold 30 and the movable mold 20. Hereafter, the direction of movement of the movable mold 20 relative to the fixed mold 10 (in other words, the left and right directions in Figures 1 and 2) may be referred to as the "first direction." In the first direction, the side on which the fixed mold 10 is positioned may be referred to as the "first side," and the side on which the movable mold 20 is positioned may be referred to as the "second side." The injection molding machine 1 is positioned such that the up and down direction in Figure 2 is the top and bottom direction. In the following, the vertical direction in Figure 2 may be simply referred to as the "vertical direction." Furthermore, the direction perpendicular to the first direction and the vertical direction (in other words, the vertical direction in Figure 1) may be referred to as the "second direction."

[0011] The injection blow molding machine 1 includes a fixed platen 11 fixed to a frame 500 fixed to the floor and holding a fixed mold 10, and a movable platen 21 slidably attached to a guide member 510 on the frame 500 and holding a movable mold 20. Further, the injection blow molding machine 1 includes an intermediate mold support frame 31 slidably attached to the guide member 510 between the fixed platen 11 and the movable platen 21 and supporting an intermediate mold 30.

[0012] Also, the injection blow molding machine 1 includes an injection device (not shown) that injects resin into a cavity 17 formed between the fixed mold 10 and the intermediate mold 30 on the side opposite to the fixed mold 10 with respect to the fixed platen 11. Also, the injection blow molding machine 1 includes a mold clamping device (not shown) on the side opposite to the movable mold 20 with respect to the movable platen 21. The mold clamping device has a mold clamping cylinder device (not shown) for driving the movable platen 21 and a support plate (not shown) to which the mold clamping cylinder device is attached. The support plate and the fixed platen 11 are connected by a plurality (for example, four) of tie bars 520. The fixed platen 11 is fixed to the frame 500 by bolts or the like. The movable platen 21 and the intermediate mold support frame 31 are mainly supported from below by the guide member 510 and move in the first direction along the tie bars 520.

[0013] Also, the injection blow molding machine 1 includes a plurality of female mold parts 12 and a cavity plate 13 holding the plurality of female mold parts 12. In the present embodiment, a total of 12 female mold parts 12 are provided so as to form two columns of six arranged in the vertical direction, and a cavity plate 13 holding the 12 female mold parts on the fixed mold 10.

[0014] The movable mold 20 has a movable blow split mold 22, a first bottom mold 23, a second bottom mold 24, and a suction device 25 for sucking the final molded product 600. The movable injection split mold 22 has a driving-side movable part 22a and a driven-side movable part 22b that are arranged opposite to each other. The driving-side movable part 22a and the driven-side movable part 22b are moved in the second direction by a split mold driving cylinder device 26 to come into close contact with or move away from each other. And when the driving-side movable part 22a and the driven-side movable part 22b come into close contact with each other, a female mold 27 for injection molding is formed. In the present embodiment, six female molds 27 for injection molding arranged vertically in a set of the driving-side movable part 22a and the driven-side movable part 22b are formed, and two sets of the driving-side movable part 22a and the driven-side movable part 22b are arranged side by side in the second direction. The driving-side movable part 22a is connected to a piston rod 26a of the split mold driving cylinder device 26 and is directly moved by the split mold driving cylinder device 26. The driven-side movable part 22b is connected to the driving-side movable part 22a of the other set and is moved in the second direction so as to come into contact with or move away from the driving-side movable part 22a of its own set. The split mold driving cylinder device 26 can be exemplified as, for example, a pneumatic cylinder device.

[0015] The first bottom mold 23 is attached to the movable platen 21. A through hole 23a penetrating in the first direction is formed in the first bottom mold 23. The through hole 23a is arranged on the extension line of the center line of the final molded product 600 in a state where the driving-side movable part 22a and the driven-side movable part 22b are mold-closed, and forms a space where the second bottom mold 24 can be arranged. Around the through hole 23a in the first bottom mold 23, a recess 23b recessed from the contact surface with the movable injection split mold 22 is formed. Note that the recess 23b does not have to be formed around the through hole 23a.

[0016] The second bottom mold 24 is a columnar member and is arranged in the through hole 23a of the first bottom mold 23. The second bottom mold 24 is arranged so as to slightly protrude to the first side in the first direction from the recess 23b of the first bottom mold 23. The diameter of the second bottom mold 24 is slightly smaller than the diameter of the through hole 23a of the first bottom mold 23. For this reason, a gap is formed between the first bottom mold 23 and the second bottom mold 24 in a state where the second bottom mold 24 is arranged in the through hole 23a.

[0017] The suction device 25 consists of a vacuum pump and the like, and sucks up the final molded product 600. Specifically, the suction device 25 sucks up the final molded product 600 using the gap formed between the first bottom mold 23 and the second bottom mold 24 as an air passage during suction.

[0018] The intermediate mold 30 includes a rotating frame 35 that is rotatably attached to the intermediate mold support frame 31, and a core mold frame 50 that is not rotatably attached to the intermediate mold support frame 31. Here, the intermediate support frame 31 comprises rectangular parallelepiped-shaped legs 32, which are positioned at both ends in the second direction and are shaped such that the vertical direction is the longitudinal direction and the first direction is the short direction; a top plate 33u connecting the upper parts of both legs 32; and a bottom part 33b connecting the lower parts of both legs 32. A cylindrical support column 34 is fixed to the vertical center of each leg 32, and is attached so as to penetrate the leg 32 in the second direction. Furthermore, through holes (not shown) in the first direction for passing tie bars 520 are formed in the upper and lower parts of each leg 32.

[0019] The rotating frame 35 is attached to the outer circumference of the support column 34 via bearing members 36 such as ball bearings, and is rotatable relative to the intermediate support frame 31 with the centerline of the support column 34 as the center of rotation. In this embodiment, an annular driven gear 37 is attached to the side surface of the rotating frame 35, and a drive gear 38b attached to the rotating shaft 38a of the electric motor 38 meshes with the driven gear 37. As a result, the rotating frame 35 rotates around the support column 34 when the electric motor 38 is operated.

[0020] The intermediate mold 30 includes a plurality of guide bars 39 attached to the rotating frame 35 so as to extend in a first direction, a gripping frame 40 slidably attached to the guide bars 39 in the first direction, and a limiting portion 45 that restricts the movement of the gripping frame 40 relative to the guide bars 39. In this embodiment, in the open state shown in Figures 1 and 2, the intermediate mold 30 has one guide bar 39 at the first end of the rotating frame 35, and one at the upper and lower ends of each end in the second direction. In addition, the rotating frame 35 has one guide bar 39 at the second end, and one at the upper and lower ends of each end in the second direction. In other words, the intermediate mold 30 according to this embodiment has a total of eight guide bars 39. However, the intermediate mold 30 may also have guide bars extending to both the fixed mold 10 side and the movable mold 20 side at the upper and lower ends of each end in the second direction, for a total of four guide bars.

[0021] In the state shown in Figures 1 and 2, one gripping frame 40 is provided at each end of the first direction of the rotating frame 35. The gripping frame 40 is slidably attached to four guide bars 39, which are located on the same side with respect to the centerline of the support column 34, and is also lockable and unlockable to the tips 39a of the guide bars 39. In the state shown in Figures 1 and 2, the gripping frame 40 is locked to the tips 39a of the guide bars 39 by a limiting portion 45, preventing it from sliding relative to the guide bars 39. When the engagement between the limiting portion 45 and the tips 39a of the guide bars 39 is released, the gripping frame 40 becomes slidable relative to the guide bars 39.

[0022] The gripping frame 40 has a gripping device 41 for forming and gripping the mouth portion 620 of the final molded product 600. The gripping device 41 includes a screw split mold 42 for forming and gripping the mouth portion 620, a slide plate 43 to which the screw split mold 42 is attached, and a gripping release member 44 for releasing the grip of the mouth portion 620. The gripping release member 44 is driven by a gripping release drive device (not shown). The screw split mold 42 forms the mouth portion 620 in a closed state during injection molding and grips the mouth portion 620 in a closed state during blow molding. The screw split mold 42 also releases the mouth portion 620 by opening the mold after the completion of blow molding.

[0023] More specifically, the screw mold 42 is configured to be separable in a second direction, with each half of the screw mold 42 attached to the half of the slide plate 43. The half of the slide plate 43 is also attached to the gripping frame 40 so as to be slidable in the second direction. The gripping release member 44 is configured to be separable in a second direction, with each half of the gripping release member 44 attached to the half of the slide plate 43. When the gripping release member 44 is pushed open in the second direction, the half of each slide plate 43 and the half of each screw mold 42 are also pushed open and separated in the second direction. This releases the grip on the mouth 620 of the final molded product 600 after the blow molding is completed at the blow station. In this embodiment, the screw split mold 42 is provided at positions corresponding to the female mold portion 12 attached to the fixed mold 10 and the female mold 27 for blow molding of the movable blow split mold 22. In other words, in the state shown in Figures 1 and 2, the screw split mold 42 forms two rows of six pieces arranged vertically.

[0024] The limiting section 45 is also releasably connected to the tip (not shown) of an injection-side member (not shown) attached to the fixed platen 11, and is operated by the tip of the injection-side member to lock or unlock the tip 39a of the guide bar 39. Furthermore, the limiting section 45 is also releasably connected to the tip (not shown) of a blowing-side member (not shown) attached to the movable platen 21 or the first bottom mold 23, and is operated by the tip of the blowing-side member to lock or unlock the tip 39a of the guide bar 39.

[0025] The core formwork 50 is fixed to the support column 34, thereby being non-rotatably attached to the intermediate support frame 31. An injection core mold 51 is attached to the side of the core mold 50 facing the fixed platen 11, and a blowing guide 52 is attached to the side of the core mold 50 facing the movable platen 21. The injection core mold 51 has a base portion 51a and a male mold portion 51b, and in the closed state, it forms a cavity 17 between itself and the female mold portion 12 that has the shape of the preform 610. The blowing guide 52 has a base portion 52a and, when in a closed state, is in close contact with the entrance of the female mold 27 for blow molding, which is formed by the close contact of the drive-side movable portion 22a and the driven-side movable portion 22b, and forms a space for blow molding that has the shape of the final molded product 600.

[0026] The intermediate mold 30 also includes an extension rod 53 that can protrude from the base 52a of the blowing guide 52, a connecting plate 54 to which the base portions of the multiple extension rods 53 are attached, and an extension rod drive device 55 for extending the extension rods 53. The extension rod drive device 55 can be exemplified as, for example, a pneumatic cylinder device. The extension rod drive device 55 can be exemplified as being attached to the upper and lower outer surfaces of the core mold 50. The connecting plate 54 is connected to the piston rod of the extension rod drive device 55. When the extension rod drive device 55 is operated, the connecting plate 54 connected to the piston rod moves, and the extension rods 53 protrude into the preform 610. In this embodiment, the final molded product 600 is formed from the preform 610 by stretch blow molding, in which a stretch rod 53 is made to protrude into the preform 610, and air is blown in at a pressure sufficient to expand the preform while stretching the stretch rod 53.

[0027] Furthermore, the injection molding machine 1 includes an intermediate mold drive cylinder device 15 that moves the intermediate mold support frame 31 in a first direction relative to the fixed platen 11, and a connecting rod 16 connected to the piston rod of the intermediate mold drive cylinder device 15. The intermediate mold drive cylinder device 15 is fixed to the fixed platen 11, and the connecting rod 16 is attached to the intermediate mold support frame 31. By operating the intermediate mold drive cylinder device 15, the intermediate mold support frame 31 can be moved relative to the fixed platen 11. As a result, the injection molding machine 1 can perform injection molding and blow molding by closing, clamping, and opening the mold at separate timings in the injection station and the blowing station.

[0028] Furthermore, the injection molding machine 1 has a control device 70 that controls the injection molding machine 1. The control device 70 has a CPU (Central Processing Unit) (not shown), a ROM (Read Only Memory) (not shown) which is a memory area for storing programs, and a RAM (Random Access Memory) (not shown) which is a program execution area. The control device 70 realizes various functions by having the CPU execute programs stored in the ROM or a storage device such as an HDD (Hard Disk Drive) or semiconductor memory. The control device 70 also receives detection results from various sensors. Based on the detection results from the various sensors, the control device 70 controls the operation of the injection device (not shown), the clamping device (not shown), the intermediate mold drive cylinder device 15, the electric motor 38, the grip release drive device (not shown), the stretch rod drive device 55, etc. The operation of the injection molding machine 1, which is performed based on the control by the control device 70, will be described below.

[0029] (operation) In this embodiment, the injection blow molding machine 1, in one molding cycle, forms 12 preforms 610 equal to the number of female molds 12 by injection molding at the injection station. In addition, at the blow station, the injection blow molding machine 1 uses the same number of preforms 610 formed at the injection station in the previous molding cycle to perform blow molding and form 12 final molded products 600.

[0030] First, as shown in Figures 1 and 2, the mold opens at the injection station and blowing station, and a mold clamping device (not shown) activates to begin closing the mold. This causes the movable platen 21 to move from the open state to the closed state, that is, closer to the fixed platen 11. While the movable platen 21 is moving from the open state to the closed state, the intermediate mold drive cylinder device 15 activates, causing the intermediate mold support frame 31 to move from the open state to the closed state, that is, closer to the fixed platen 11.

[0031] Furthermore, as the intermediate support frame 31 approaches the fixed platen 11, the limiting portion 45 of the gripping frame 40, which is engaged with the tip 39a of the guide bar 39 attached to the side of the rotating frame 35 on the fixed platen 11 side, comes into contact with the tip (not shown) of the injection-side member (not shown) attached to the fixed platen 11. As a result, the engagement between the limiting portion 45 and the tip 39a of the guide bar 39 is released, and the lock between the gripping frame 40 and the guide bar 39 is released.

[0032] Similarly, as the movable platen 21 moves from the open mold state to the closed mold state, the movable platen 21 approaches the intermediate mold support frame 31. Then, the limiting portion 45 of the gripping frame 40, which is fitted with the tip 39a of the guide bar 39 attached to the side of the rotating frame 35 on the movable platen 21 side, comes into contact with the tip (not shown) of the blowing side member (not shown) attached to the movable platen 21 or the first bottom mold 23. As a result, the fitting between the limiting portion 45 and the tip 39a of the guide bar 39 is released, and the lock between the gripping frame 40 and the guide bar 39 is released. Before the movable platen 21 moves from the open state to the closed state, the split mold drive cylinder device 26 is activated, causing the drive-side movable part 22a and the driven-side movable part 22b to move in the second direction and close, forming the female mold 27 for blow molding.

[0033] Then, when the movable platen 21 is in the closed position, the mold closing is completed at the injection station and the blowing station. In this case, the gripping frame 40 at the injection station and the blowing station is released from its lock with the guide bar 39, and is pushed by the injection-side member (not shown) or the blowing-side member (not shown) to slide relative to the guide bar 39 and come into contact with the core mold 50.

[0034] In this case, as shown in Figure 3(a), in the injection station, each male mold part 51b is inserted into each female mold part 12 attached to the fixed mold 10. A cavity 17 is formed between the inner surface of the female mold part 12 and the screw split mold 42 and the outer surface of the male mold part 51b. Then, as shown in Figure 3(b), the resin injected by the injection device fills the cavity 17. After the resin filling is complete, the mold remains closed to cool the resin inside the cavity.

[0035] In the blowing station, as shown in Figure 4(a), the screw split die 42, which is gripping the mouth 620 of the preform 610, is pressed against the opening of the blow-molding female mold 27, which is formed by the drive-side movable part 22a and the driven-side movable part 22b. As a result, the flange of the preform 610 is pressed against the outer surface of the opening of the blow-molding female mold 27, and the part beyond the flange enters the inside of the blow-molding female mold 27. Also, the tip 52b of the base 52a of the blowing guide 52 enters the mouth 620 of the preform 610. Then, the stretch rod drive device 55 is activated, and the stretch rod 53 protrudes toward the back of the blow-molding female mold 27. At the same time, air with a pressure sufficient to inflate the preform is blown into the inside of the preform 610, thereby inflating the preform 610 and pressing it against the inner surface of the blow-molding female mold 27. As a result, as shown in Figure 4(b), a bottle-shaped or bottle-shaped bottomed container having the shape of the inner surface of the female mold 27 for blow molding is formed as the final molded product 600. When the stretching is complete, the stretching rod 53 is returned to its original position from its protruding state. Then, when the blow molding is complete, the clamping force applied to the movable platen 21 by the mold clamping device is released.

[0036] Subsequently, while maintaining the positional relationship between the drive-side movable part 22a and the driven-side movable part 22b and the gripping device 41, the movable platen 21 moves away from the core mold 50. Then, when a predetermined gap is formed between the screw split mold 42 and the blowing guide 52, the drive-side movable part 22a and the driven-side movable part 22b move in a second direction. The screw split mold 42 is also pushed open in the second direction, opening the mouth 620. Then, when the distance between the drive-side movable part 22a and the driven-side movable part 22b becomes at least greater than the outer diameter of the final molded product 600, the final molded product 600 falls downward from between the drive-side movable part 22a and the driven-side movable part 22b. The final molded product 600 is discharged below the injection blowing molding machine 1 and stored in a storage device (not shown).

[0037] Subsequently, the intermediate mold drive cylinder device 15 operates, causing the intermediate mold support frame 31 to move from the mold closed state to the mold open state, that is, away from the fixed platen 11. Since the limiting portion 45 of the gripping frame 40 in the injection station is fitted with the tip portion (not shown) of the injection side member (not shown), the gripping frame 40 slides in the axial direction of the guide bar 39 even when the intermediate mold support frame 31 moves toward the mold open state. Therefore, the screw split mold 42 remains fitted in the vicinity of the entrance of the female mold portion 12. As a result, the core mold frame 50 moves together with the intermediate mold support frame 31, and the male mold portion 51b is pulled out from the female mold portion 12 attached to the fixed mold 10.

[0038] Subsequently, when the gripping frame 40 reaches the tip 39a of the guide bar 39, the limiting portion 45 disengages from the tip of the injection-side member and engages with the tip 39a of the guide bar 39, thus locking the gripping frame 40 and the guide bar 39 together. Therefore, as the intermediate support frame 31 moves further away from the fixed platen 11, the gripping frame 40 also moves with it, and the screw split mold 42 is pulled out from the female mold portion 12. In this case, the split portion of the screw split mold 42 is biased toward the center by the biasing member and is coupled to each other, so it grips the mouth 620 of the preform 610. As a result, the gripping frame 40 in the injection station reaches a position away from the fixed mold 10 with the screw split mold 42 gripping all 12 preforms 610.

[0039] Next, the electric motor 38 is activated, causing the rotating frame 35 to rotate around the centerline of the support column 34. As a result, the gripping frame 40 in which the screw mold 42 grips the preform 610 moves from the injection station to the blowing station, and the other gripping frame 40 moves from the blowing station to the injection station. Then, when the rotation of the rotating frame 35 is complete, the mold opens at the injection station and the blowing station. This completes one molding cycle. Thereafter, the above operation is repeated, and a predetermined number of molding cycles are repeated.

[0040] Figure 5 shows an example of an injection molding method. Figure 6 shows an example of the mold release process according to the embodiment. As described above, the injection blow molding method for molding the final molded product 600 includes an injection step in which the preform 610 is molded on the inner surfaces of the male mold portion 51b, the female mold portion 12, and the screw split mold 42 (an example of a gripping mold portion), as shown in Figure 5(a). The injection blow molding method also includes a demolding step in which the preform 610 is separated from the female mold portion 12 and the male mold portion 51b while the screw split mold 42 is gripping the preform 610, as shown in Figure 5(b). The injection blow molding method also includes a transfer step in which the preform 610 is moved from the injection station to the blowing station, and a blowing step in which air is blown into the preform 610 while it is being gripped by the screw split mold 42, as shown in Figures 5(c) and (d). Furthermore, in the demolding process according to this embodiment, as shown in Figures 6(a) and (b), the male mold portion 51b is separated from the preform 610 before the female mold portion 12 is separated from the preform 610.

[0041] This is for the following reasons. The temperature of the preform 610 after the transition process is preferably as follows: The temperature of the body 611 of the preform 610 should be between 90°C and 120°C, and the temperature of the tip 612 of the preform 610 should be between 70°C and 100°C. As shown in Figure 6(b), the body 611 is the cylindrical part, and the tip 612 is the part whose outer diameter, when cut along a plane perpendicular to the centerline of the body 611, gradually decreases from the body 611 side to the tip side.

[0042] If the temperature of the body portion 611 is below 90°C and the temperature of the tip portion 612 is below 70°C, even if air with sufficient pressure to expand the preform 610 is blown into the preform 610 during the blowing process, the preform 610 will solidify without fully expanding. If the preform 610 solidifies without fully expanding, the stretching rod 53 may pierce the preform 610, or the final molded product 600 may not take its shape. On the other hand, if the temperature of the body portion 611 exceeds 120°C and the temperature of the tip portion 612 exceeds 100°C, the preform 610 stretches when it separates from the female mold portion 12, causing a recess (in other words, sink mark) to occur in the inner part of the final molded product 600 at the bottom side of the mouth portion 620. Also, even if the temperature of the preform 610 is high, the stretching rod 53 may pierce the preform 610.

[0043] Figure 7 shows an example of the mold release process related to the comparative example. Here, as a demolding step in a comparative example, we consider the case where the timing of the preform 610 separating from the female mold part 12 and the timing of the male mold part 51b separating from the preform 610 are the same, as shown in Figure 7. In the demolding process of the comparative example, the male mold portion 51b remains inside the preform 610 until the temperature of the tip portion 612 reaches a temperature suitable for separation from the female mold portion 12 (hereinafter sometimes referred to as the "temperature suitable for demolding," for example, 100°C). Therefore, while the temperature of the tip portion 612 is being released, heat from the preform 610 is dissipated through the male mold portion 51b and the female mold portion 12. As a result, the temperature of the body portion 611 of the preform 610 after the transition process may fall below 90°C.

[0044] On the other hand, in the demolding process according to this embodiment, as shown in Figures 6(a) and (b), the male mold portion 51b is separated from the preform 610 before the preform 610 separates from the female mold portion 12, so that the heat of the preform 610 is less likely to be dissipated through the male mold portion 51b. Therefore, the temperature of the body portion 611 of the preform 610 after the transition process is higher than that of the demolding process according to the comparative example. As a result, the temperature of the preform 610 can be set to a temperature at which demolding can be reliably achieved, and at a temperature at which it can expand when air with sufficient pressure is blown in to expand the preform.

[0045] As described above, it is desirable that the temperature of the preform 610 after the transition process be such that the temperature of the body 611 is 90°C or higher and less than 120°C, and the temperature of the tip 612 is 70°C or higher and less than 100°C. Therefore, the higher the temperature of the body 611 is than the temperature of the tip 612, the easier it is for both the body 611 and the tip 612 to fall within the above temperature range. In the demolding process according to this embodiment, the temperature drop of the body 611 after the injection process can be suppressed more effectively than in the demolding process according to the comparative example, so that the temperature of the body 611 after the transition process can be made higher than the temperature of the tip 612 with greater certainty. Note that in both the preform 610 molded using the demolding process according to this embodiment and the preform 610 molded using the demolding process according to the comparative example, the tip 612 cools more than the body 611 during the transition process. Therefore, if the temperature of the body 611 and the temperature of the tip 612 are the same before the transition process, then after the transition process, the temperature of the body 611 will be higher than the temperature of the tip 612.

[0046] Figure 8 shows an example of the relationship between the temperature of the body 611 and tip 612 of the preform 610 after the transition process and the quality of the final molded product 600. The temperatures shown in Figure 8 are the temperatures of the preform 610 after the transition process, with the temperature of the body 611 being the maximum temperature at the end on the mouth side 620, and the temperature of the tip 612 being the maximum temperature at the tip 612. The final molded product 600 is a 110 ml beverage bottle container molded using PET (Polyethylene Terephthalate). It is believed that the same results as shown in Figure 8 would be obtained even if the final molded product 600 were a bottle container between 65 ml and 200 ml.

[0047] As shown in Figure 8, when the temperature of the body portion 611 was 100°C or higher but less than 110°C and the temperature of the tip portion 612 was 80°C or higher but less than 90°C, the quality of the final molded product 600 was good. On the other hand, when the temperature of the body 611 was between 90°C and 100°C and the temperature of the tip 612 was between 70°C and 80°C, the quality of the majority of the final molded products 600 was good, but some preforms 610 did not expand completely and did not take on the shape of the final molded product 600. Therefore, when the temperature of the body 611 is between 90°C and 100°C and the temperature of the tip 612 is between 70°C and 80°C, there is a concern that expansion will be insufficient (in other words, insufficient blowing).

[0048] Furthermore, when the temperature of the body portion 611 was between 110°C and 120°C and the temperature of the tip portion 612 was between 90°C and 100°C, the quality of the majority of the final molded products 600 was good, but some of the final molded products 600 had depressions (in other words, sink marks). Therefore, when the temperature of the body portion 611 is between 110°C and 120°C and the temperature of the tip portion 612 is between 90°C and 100°C, there is a concern that depressions may occur in the final molded product 600.

[0049] Therefore, it is desirable that the temperature of the body portion 611 of the preform 610 after the transition process be between 100°C and 110°C, and the temperature of the tip portion 612 be between 80°C and 90°C. This ensures that the quality of the final molded product 600 is reliably good.

[0050] Furthermore, through diligent research by the inventors, it has been found that the quality of the final molded product 600 is good when the temperature balance is such that the temperature difference between the end of the body portion 611 on the mouth portion 620 side and the temperature of the tip portion 612 of the preform 610 is 20°C. For example, if the temperature of the body portion 611 is 110°C or higher but less than 120°C, and the temperature of the tip portion 612 is 70°C or higher but less than 80°C, the tip portion 612 is less likely to expand than when the temperature of the tip portion 612 is 80°C or higher but less than 90°C, so the body portion 611 is more likely to stretch. As a result, the shape of the shoulder portion, which is the area near the mouth portion 620 of the final molded product 600, becomes less likely to conform to the shape of the female mold 27 for blow molding.

[0051] Furthermore, if the temperature of the body portion 611 is between 90°C and 100°C, and the temperature of the tip portion 612 is between 90°C and 100°C, the temperature of the tip portion 612 will be higher than or equal to the temperature of the body portion 611. As a result, the tip portion 612 will stretch more easily than the body portion 611, or the stretching of the body portion 611 and the tip portion 612 will be equal. Therefore, for example, when the preform 610 separates from the female mold portion 12, the stretching of the tip portion 612 may cause a recess (in other words, a sink mark) to occur in the tip portion 612, increasing the risk of a defect in appearance.

[0052] Furthermore, the inventors have found that, in addition to using the demolding process according to this embodiment, by making the thickness of the tip portion 612 greater than the thickness of the body portion 611, it is possible to achieve a temperature balance in the preform 610 that results in good quality of the final molded product 600. Therefore, in the injection process of the injection blow molding method described above, it is preferable to mold the preform 610 so that the thickness of the tip portion 612 is greater than the thickness of the body portion 611 of the preform 610. This makes it possible to reliably achieve good quality in the final molded product 600.

[0053] For example, the thickness of the tip portion 612 of the preform 610 can be exemplified as being between 1.1 and 1.3 times the thickness of the body portion 611. For instance, the thickness of the tip portion 612 at the tip side may be 1.2 to 1.3 times the thickness of the mouth portion 620 side of the body portion 611, and the thickness of the tip portion 612 at the body portion 611 side may be 1.1 to 1.2 times the thickness of the mouth portion 620 side of the body portion 611. It is also preferable to gradually increase the thickness of the tip portion 612 from the body portion 611 side to the tip side. [Explanation of Symbols]

[0054] 1…Injection blow molding machine, 10…Fixed mold, 11…Fixed platen, 12…Female mold section, 13…Cavity plate, 20…Movable mold, 21…Movable platen, 31…Intermediate mold support frame, 35…Rotating frame, 39…Guide bar, 39a…Tip section, 40…Gripping frame, 41…Gripping device, 42…Screw split mold (example of gripping mold section), 45…Restriction section, 50…Core mold frame, 51b…Male mold section, 600…Final molded product, 610…Preform, 611…Body section, 612…Tip section

Claims

1. An injection process in which a preform is formed on the inner surfaces of the male mold, female mold, and gripping mold, A release step is performed to separate the preform from the female mold part and the male mold part while the gripping mold part is gripping the preform, A blowing step in which air is blown into the preform while it is being held by the gripping mold, Equipped with, In the demolding step, the male mold is separated from the preform before the female mold is separated from the preform. Injection blow molding method.

2. The temperature of the body of the preform after the demolding step and before the blowing step is made higher than the temperature of the tip of the preform. The injection molding method according to claim 1.

3. The temperature of the body of the preform is set to 90°C or higher and less than 120°C, and the temperature of the tip of the preform is set to 70°C or higher and less than 100°C. The injection molding method according to claim 2.

4. The temperature of the body of the preform is set to 100°C or higher and less than 110°C, and the temperature of the tip of the preform is set to 80°C or higher and less than 90°C. The injection molding method according to claim 3.

5. In the injection molding process, the thickness of the tip portion of the preform is molded to be greater than the thickness of the body portion of the preform. The injection molding method according to any one of claims 1 to 4.

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