Injection blow molding machine and method for detecting molding defects

Abstract

To provide an injection blow molding machine and a method for detecting molding defects, which are capable of detecting the occurrence of a molding defect when a molding defect occurs during blow molding. [Solution] The injection blow molding machine of the present invention is equipped with a fixed mold, an intermediate mold, and a movable mold, the movable mold having a movable concave mold portion that forms a cavity space, the movable concave mold portion having a communication hole that connects the outside of the movable concave mold portion with the inside of the cavity space, the injection blow molding machine is equipped with a fluid supply mechanism that supplies fluid to the communication hole, and a detection mechanism that detects the pressure of the fluid when the fluid is supplied into the communication hole. Also, the method of the present invention is a method for detecting molding defects in a molded product molded using the above injection blow molding machine, and includes a step of detecting the pressure of the fluid supplied to the communication hole by the fluid supply mechanism after blow-molding the molded product.

Description

[Technical Field]

[0001] The present invention relates to an injection blow molding machine and a method for detecting molding defects. [Background technology]

[0002] Injection blow molding machines have been used for molding containers for holding beverages, food, and other contents, as well as other molded products. Injection blow molding machines can simultaneously perform injection molding of a preform, which is an intermediate molded body, and blow molding to expand the preform to obtain a molded product, all in the same molding machine, allowing for efficient mass production of molded products. Summary of the Invention [Problem to be solved by the invention]

[0003] When blow molding preforms using an injection blow molding machine, defective products can occur due to insufficient blowing. If defective products are mixed in with good products and transported to a subsequent process, it becomes necessary to remove only the defective products from the mixed state in the subsequent process. Therefore, there is a need to detect when defective products occur due to insufficient blowing or other reasons during blow molding.

[0004] Therefore, an object of the present invention is to provide an injection blow molding machine and a method for detecting molding defects that can detect the occurrence of a defective molded product when a molding defect occurs during blow molding. [Means for solving the problem]

[0005] One injection blow molding machine that can solve the above-mentioned problems is an injection blow molding machine to which a fixed mold, an intermediate mold, and a movable mold are attached, the movable mold has a movable-side concave mold portion that forms a cavity space, the movable-side concave portion has a communication hole that communicates the outside of the movable-side concave portion with the inside of the cavity space, The injection blow molding machine includes a fluid supply mechanism that supplies fluid to the communication hole, and a detection mechanism that detects the pressure of the fluid when the fluid is supplied into the communication hole.

[0006] Furthermore, one method for detecting molding defects that can solve the above-mentioned problems is a method for detecting molding defects in a molded product molded using the above-mentioned injection blow molding machine, comprising the steps of: The method includes a step of detecting, with the detection mechanism, the pressure of the fluid supplied to the communication hole by the fluid supply mechanism after blow-molding a molded product in the cavity space within the movable concave mold portion. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an injection blow molding machine and a method for detecting molding defects that are capable of detecting the occurrence of a defective molded product when a molding defect occurs during blow molding. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing an example of an injection blow molding machine according to an embodiment of the present invention and a mold device attached to the injection blow molding machine. [Figure 2] 2 is a view showing the mold assembly shown in FIG. 1 in a state where mold opening is completed. FIG. [Figure 3] FIG. 3 is a cross-sectional view taken along line II in FIG. 2. [Figure 4] FIG. 2 is a view showing the mold apparatus shown in FIG. 1 in a mold clamping state. [Figure 5] FIG. 5 is a cross-sectional view taken along line II-II in FIG. [Figure 6] 6 is an enlarged cross-sectional view showing a part of a fixed mold and an intermediate mold of the mold device shown in FIG. 5. [Figure 7] 6 is an enlarged cross-sectional view showing a part of a movable mold and an intermediate mold of the mold device shown in FIG. 5. [Figure 8] 2 is a flowchart illustrating a molding method using the injection blow molding machine shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail, but the present invention is not limited to the present embodiment.

[0010] [Injection blow molding machine] The injection blow molding machine of this embodiment is an injection blow molding machine as shown in Fig. 1, which is equipped with a mold assembly including a fixed mold, an intermediate mold that has multiple core molds arranged on both sides and is capable of rotating and sliding, and a movable mold. Molded products that can be molded by the injection blow molding machine of this embodiment are not particularly limited, but examples include containers for containing contents such as beverages and food. The production of molded products using an injection blow molding machine involves the steps of injecting molding material into an injection molding cavity to form a preform, and then supplying a fluid such as gas to the preform in the blow molding cavity to expand the preform and produce the molded product.

[0011] [Molding equipment] As shown in Figures 1 to 7, the mold device 101 attached to the injection blow molding machine of this embodiment includes a fixed mold 102, a movable mold 103, and an intermediate mold 104 having multiple core molds 104a arranged on both sides, with the core molds 104a being capable of being clamped to the fixed mold 102 and the movable mold 103. Fig. 2 is a side view of the mold apparatus 101 shown in Fig. 1 attached to an injection blow molding machine at the completion of mold opening. Fig. 3 is a cross-sectional view taken along line II in Fig. 2. Fig. 4 is a side view of the mold apparatus 101 attached to an injection blow molding machine at the time of mold clamping. Fig. 5 is a cross-sectional view taken along line II-II in Fig. 4. Figs. 6 and 7 are enlarged cross-sectional views of the cross-sectional view of Fig. 5.

[0012] In the mold device 101, the fixed mold 102 is attached to the fixed platen 32a side, and the movable mold 103 is attached to the movable platen 32b side. An intermediate mold 104 of the mold device 101 is attached to a rotary shaft portion 41 provided on the intermediate mold support frame 32c, and is rotated by the rotary shaft portion 41. Details of the mold clamping device 31 having the fixed platen 32a, the movable platen 32b, and the intermediate mold support frame 32c will be described later.

[0013] As shown in Figures 5 and 6, the fixed mold 102 has a fixed-side concave mold portion 102a that cooperates with a core mold 104a of the intermediate mold 104 to form a cavity space for injection molding when the mold device 101 is in a clamped state. The cavity space has a shape corresponding to the desired shape of the preform PF, which is an intermediate molded body before blow molding, and the preform PF is molded by injecting a molten molding material into the cavity space. In the example shown in Figure 6, the preform PF is formed in the cavity space.

[0014] As shown in Figure 6, the fixed side concave portion 102a has a gate 102c at the bottom, which is on the opposite side of the opening 102b of the fixed side concave portion 102a in the direction along the axis A (hereinafter also referred to as the axial direction), and the molten molding material from the injection device 21 flows into the cavity space through the gate 102c. In addition, the shape of the surface forming the cavity space and the shape of the outer surface of the mold can be cylindrical in the fixed-side concave mold portion 102a of the fixed mold 102, as well as in the movable-side concave mold portion 103a of the movable mold 103 described below, and the core mold 104a of the intermediate mold 104. Also, it is assumed that an imaginary axis A exists at the center of the fixed-side concave mold portion 102a, the movable-side concave mold portion 103a, and the core mold 104a. In the illustrated example, six fixed-side concave mold portions 102a are lined up in the height direction of the mold apparatus 101 to form a row, and two rows are provided with an interval in the width direction of the mold apparatus 101. Note that the number of fixed-side concave mold portions 102a for injection molding is not particularly limited.

[0015] Furthermore, the fixed mold 102, the movable mold 103 described below, and the intermediate mold 104 need to be adjusted to appropriate temperatures in each step of injection blow molding. For this reason, the fixed mold 102, the movable mold 103, and the intermediate mold 104 may have internal flow paths (not shown) that allow the flow of a liquid such as oil or water or other heat transfer medium for heating. Furthermore, the fixed mold 102, the movable mold 103, and the intermediate mold 104 may be provided with a temperature detection element (not shown) such as a thermocouple.

[0016] 5 and 7, the movable mold 103 has a movable-side concave mold portion 103a that cooperates with a core mold 104a of the intermediate mold 104 to form a cavity space for blow molding when the mold device 101 is in a clamped state. Specifically, the movable-side concave mold portion 103a can have a bottom mold portion 103c located on the opposite axial side of the opening 103d of the movable-side concave mold portion 103a (more inward than the opening 103d), and multiple split mold portions 103b (two split mold portions in the illustrated example) adjacent to the bottom mold portion 103c on the axial opening side and separable in a radial direction (mold width direction) perpendicular to the axial direction. The bottom mold portion 103c and the split mold portion 103b of the movable-side concave mold portion 103a are combined, and a cavity space is formed inside the movable-side concave mold portion 103a by inserting the core mold 104a of the intermediate mold 104. Furthermore, the surface of the movable-side concave mold portion 103a that forms the cavity space has a shape that corresponds to the shape of the outer surface of the molded product MP. In other words, the surface of the movable-side concave mold portion 103a regulates the expansion of the preform PF that expands during blow molding, and as a result, the shape of the surface of the movable-side concave mold portion 103a is transferred to the molded product MP as the shape of the outer surface of the molded product MP, thereby forming the desired shape of the molded product MP. In the example shown in Figure 7, the preform PF is present on the surface of the core mold 104a, which is the state before blow molding. By performing blow molding, the molded product MP will be molded at the position indicated by the dashed line in the figure.

[0017] In the illustrated example, the movable-side concave mold portion 103a for blow molding is formed of a bottom mold portion 103c and two split mold portions 103b. Six of the movable-side concave mold portions 103a are lined up in the height direction of the mold device 101 to form a row, and two such rows are provided with an interval in the width direction of the mold device 101. The number of movable-side concave mold portions 103a is not particularly limited. The split mold parts 103b can be opened and closed by a split mold opening / closing mechanism 62, which will be described later. The split mold parts 103b of the movable mold 103 that are moved in the same direction in the mold width direction by the split mold opening / closing mechanism 62 can be connected to each other by split mold connecting members 63a, 63b, so that the respective split mold parts 103b can be operated simultaneously.

[0018] In the illustrated example, the movable concave portion 103a has a bottom portion 103c and a plurality of split portions 103b, but it may have only a plurality of split portions 103b without having the bottom portion 103c.

[0019] In this embodiment, as shown in FIG. 7, the movable-side concave mold portion 103a has a communication hole 103f that connects the outside of the movable-side concave mold portion 103a (the outside of the movable mold 103 in the illustrated example) with the cavity space. Because the movable mold 103 has the communication hole 103f, for example, when a preform PF is blow-molded in the cavity space of the movable-side concave mold portion 103a, it is possible to detect whether the resulting molded product MP is properly molded by supplying a fluid such as air using a fluid supply mechanism (described later). Specifically, in the case of a molded product MP that has been properly blow-molded, the preform PF expands to the position indicated by the dashed line in FIG. 7 to form the molded product MP. After the molded product MP is molded, when a fluid is supplied by the fluid supply mechanism, the opening of the communication hole 103f is blocked by the molded product MP, preventing the fluid from flowing into the cavity space. However, if the preform PF does not expand properly in the cavity due to insufficient blowing or if the molded product MP also has a molding defect due to a molding defect (poor injection) of the preform PF, when the fluid is supplied by the fluid supply mechanism in this state, at least a portion of the fluid that has flowed through the communication hole 103f will flow into the cavity. In other words, when a molding defect occurs, the pressure of the fluid supplied by the fluid supply mechanism in the communication hole 103f will behave differently from when the fluid is blown properly. Therefore, since the movable mold 103 has the communication hole 103f, if a molding defect occurs during blow molding, it is possible to detect that a molding defect has occurred.

[0020] It is believed that molding defects such as insufficient blowing can occur due to, but are not limited to, the following factors: The factors include blockage of the blowing slit, which is used to blow gas during blow molding, by the molding material, which can occur when the preform is injection molded, or insufficient filling of the preform. If these factors occur, it is believed that insufficient blowing will occur during subsequent blow molding, making it difficult for the preform to expand sufficiently to every corner of the blow molding mold. Furthermore, if a factor that could cause such a molding defect occurs before blow molding, it tends to be difficult to detect the factor that could cause the molding defect before blow molding, because injection molding and blow molding are performed simultaneously in an injection blow molding machine.

[0021] In this embodiment, the position of the communication hole 103f is not particularly limited and can be positioned arbitrarily according to the shape of the molded product MP. In this embodiment, as shown in FIG. 7, the communication hole 103f preferably opens to a portion inward of the opening 103d of the movable-side concave mold portion 103a (toward the bottom mold portion 103c in the axial direction). More specifically, when the surface corresponding to the portion inward of the opening 103d of the movable-side concave mold portion 103a is defined as the first surface 103e, the communication hole 103f opens to the first surface 103e. Even if the preform PF does not properly expand in the cavity due to insufficient blowing or other reasons, resulting in a molding defect and a molded product MP not being molded at the position indicated by the dashed line in FIG. 7, it is possible to determine whether the obtained molded product MP was properly molded by supplying a fluid such as air to the communication hole using a fluid supply mechanism (described later).

[0022] Furthermore, in this embodiment, it is preferable that the opening of the communication hole 103f is located inside the opening 103d of the movable-side concave mold portion 103a, and that the radial position of the opening of the communication hole 103f in the movable-side concave mold portion 103a is located radially outward from the radially inner end of the opening 103d of the movable-side concave mold portion 103a. Specifically, insufficient blowing in defective molded products tends to occur in parts that expand near the end of expansion of the preform PF, specifically, in parts of the molded product MP that have a large outer diameter or corners. Furthermore, the position of such parts of the molded product MP that corresponds to the movable-side concave mold portion 103a tends to be located radially outward from the radially inner end of the opening 103d of the movable-side concave mold portion 103a. Therefore, it is preferable to position the opening of the communication hole 103f in such a position. Furthermore, the position of the opening of the communication hole 103f on the first surface 103e is more preferably a position corresponding to the part of the preform PF that expands last when the preform PF is expanded. In this embodiment, the opening of the communicating hole 103f can also be located at the opening 103d of the movable side concave portion 103a, so that even if the molded product MP is also defectively molded due to a molding defect (poor injection) of the preform PF, the injection blow molding machine of this embodiment can detect that a defective molded product has occurred.

[0023] Note that the opening 103d of the movable-side concave mold portion 103a here refers to the portion corresponding to the mouth (in the illustrated example, the mouth has a flange) and neck of the preform PF and molded product MP, as shown in Fig. 7. In blow molding, the preform PF is usually expanded as a whole, but the mouth and neck of the preform PF are prevented from expanding significantly during blow molding. The opening 103d of the movable-side concave mold portion 103a can be used to prevent such large expansion of the mouth and neck of the preform PF.

[0024] Furthermore, as in the illustrated example, when the movable-side concave portion 103a of the movable mold 103 has a bottom mold portion 103c and a split mold portion 103b, it is preferable that the opening of the communication hole 103f (the opening of the communication hole 103f to the first surface 103e) be disposed in the bottom mold portion 103c. Although it is possible to provide the communication hole 103f in the split mold portion 103b, it is easier to provide it in the bottom mold portion 103c than in the split mold portion 103b, which is opened and closed by the split mold opening / closing mechanism 62. Also, this is because the bottom mold portion 103c tends to have a portion that will become a corner of the molded product MP, which is prone to insufficient blowing (for example, a corner between a side wall and the bottom of the molded product MP).

[0025] Furthermore, the inner diameter of the opening of the communication hole 103f is preferably set to a size that makes it easy to detect the occurrence of a defective molded product, while reducing the risk of the molded product MP being affected by an excessively large diameter.

[0026] In this embodiment, the fluid flowing through the communication hole 103f is not particularly limited to a liquid or a gas, but for example, a gas such as air can be used. Furthermore, as long as the communication hole 103f opens to the first surface 103e, the flow paths inside the movable mold 103 other than the opening can be arranged arbitrarily, and the shape and size of the flow paths can also be arbitrarily determined. In the illustrated example, the communication hole 103f has a shape that narrows on the side of the opening to the first surface 103e.

[0027] 2 to 5, the intermediate mold 104 has a plate-shaped portion 104b formed in a plate shape, a core mold 104a (referred to as the one-side core mold 104a) provided on one main surface of the plate-shaped portion 104b, and a core mold 104a (referred to as the other-side core mold 104a) provided on the other main surface of the plate-shaped portion 104b. The one-side core mold 104a and the other-side core mold 104a are disposed symmetrically with the plate-shaped portion 104b in between. The one-side core molds 104a and the other-side core molds 104a are provided in the same number as the fixed-side concave mold portions 102a for injection molding and the movable-side concave mold portions 103a for blow molding.

[0028] 6 and 7, the core mold 104a of the intermediate mold 104 is substantially cylindrical. A blowing slit 104d is formed in its base portion 104c in order to blow-mold the preform PF into a cavity space formed when the core mold 104a is inserted into the movable-side concave mold portion 103a. The blowing slit 104d opens in the surface of the base portion 104c and communicates with the outside of the intermediate mold 104, allowing a fluid (particularly gas) to be blown in from the outside to expand the preform PF.

[0029] [Fluid supply mechanism, detection mechanism] In this embodiment, the injection blow molding machine 1 is equipped with a fluid supply mechanism (not shown) that supplies fluid to the communication hole 103f, and a detection mechanism (not shown) that detects the pressure of the fluid when the fluid is supplied into the communication hole 103f. In this embodiment, the injection blow molding machine 1 is equipped with the fluid supply mechanism and the detection mechanism, so that defective molded products can be detected during blow molding using the above-mentioned communication hole 103f.

[0030] The fluid supply mechanism is not particularly limited, but may be, for example, a pump capable of discharging liquid or gas. The fluid supply mechanism may be disposed in the injection blow molding machine 1 as desired. For example, during blow molding, the fluid supply mechanism starts supplying fluid after a predetermined pressure of gas has been blown into the preform PF for a predetermined time, and then stops supplying the fluid after maintaining the supply state (pressurized state) for a predetermined time (e.g., the time from the end of blowing to the start of mold opening of the split mold portion 103b of the movable-side concave mold portion 103a). Specifically, the fluid supply mechanism can be started when blowing into the preform PF during blow molding is completed by receiving a signal transmitted from a control unit that controls injection blow molding in the injection blow molding machine 1, specifically a signal to operate the fluid supply mechanism and supply fluid to the communication hole 103f. Furthermore, the fluid supply mechanism can be stopped, for example, by operating for a predetermined time, or by receiving a signal to stop operation that may be transmitted by a detection mechanism, as described below.

[0031] The upper limit of the fluid supply pressure by the fluid supply mechanism can be set to a level that does not affect the molded product MP in the movable mold 103 if the molded product MP is a good product (for example, a pressure that does not deform the blow-molded molded product MP).The lower limit of the fluid supply pressure can be set to a level that allows at least a portion of the fluid to flow into the cavity space through the communication hole 103f if the molded product MP in the movable mold 103 is defective.

[0032] The detection mechanism can detect the pressure of the fluid when the fluid is caused to flow through the communication hole 103f, and can include, but is not limited to, a pressure sensor, for example. The pressure sensor can be provided between the fluid supply mechanism and the opening of the communication hole 103f to the first surface 103e. The detection mechanism can be set to always detect the fluid pressure, but can also start detecting the pressure when the fluid supply mechanism operates (when the supply of fluid starts) and stop detecting the pressure when the fluid supply mechanism stops (when the supply of fluid stops). In addition, if the injection blow molding machine 1 is equipped with a display unit capable of displaying the fluid pressure, the detection mechanism can output the detection result to the display unit.

[0033] The detection mechanism can instruct the control unit to stop injection blow molding when the detected pressure remains below a predetermined threshold for a predetermined period of time or when the peak pressure of the detected pressure falls below a predetermined threshold. Specifically, if a molded product MP is properly molded during blow molding, the fluid supply mechanism can prevent the molded product MP from flowing into the cavity through the opening of the communicating hole 103f, resulting in a relatively high pressure detected by the detection mechanism. On the other hand, if a defective molded product is molded during blow molding, the fluid supply mechanism cannot or only slightly prevents the fluid from flowing into the cavity through the opening of the communicating hole 103f. Therefore, the pressure detected by the detection mechanism is relatively low for most of the time the fluid supply mechanism is operating. Therefore, if the pressure does not increase for a predetermined time after the fluid supply mechanism has supplied fluid, that is, if the pressure becomes low and falls below a predetermined threshold, or if the peak pressure falls below a predetermined threshold, the molded product MP can be determined to be defective.The detection mechanism then instructs the control unit to stop injection blow molding, thereby preventing defective molded products from being mixed with properly molded non-defective molded products and preventing further defective molded products from being produced.

[0034] The predetermined threshold value to be compared with the pressure detected by the detection mechanism can be set based on the pressure detected by the detection mechanism when a properly molded molded product MP is present in the movable mold 103 during blow molding. The phrase "for a predetermined period of time" in the determination condition under which the detection mechanism instructs the control unit to stop injection blow molding is intended to prevent the molded product MP from being judged as defective if a temporary low pressure state occurs. For example, the detected pressure may be low immediately after the fluid supply mechanism starts operating, and may fall below the threshold. The "predetermined period of time" can be set arbitrarily, taking into consideration the mold device, molded product, molding conditions, etc. used.

[0035] In the above description, the detection mechanism instructs the control unit to stop blow molding when the detected pressure remains below a predetermined threshold for a predetermined period of time. However, the instruction to the control unit can be changed as follows. For example, if the injection blow molding machine 1 is equipped with a recovery mechanism for preventing defective molded articles MP from being discharged from the injection blow molding machine 1 and recovering them, the detection mechanism can instruct the control unit to use the recovery mechanism to recover the defective molded articles MP when the detected pressure remains below the predetermined threshold for a predetermined period of time. Alternatively, if the injection blow molding machine 1 is equipped with a downstream device, such as a discharger for discharging the molded articles MP to the outside, the detection mechanism can instruct the control unit to stop the discharger from discharging the molded articles MP when the detected pressure remains below the predetermined threshold for a predetermined period of time. This prevents defective molded articles from being discharged without stopping injection blow molding.

[0036] [Injection device] The injection device 21 mainly includes a cylindrical or other shaped cylinder 22 extending toward the mold device 101, a screw 23 disposed inside the cylinder 22 with its central axis parallel to the cylinder 22 and with flights spiraling around its periphery, a band-like or other shaped heater 24 disposed around the outer periphery of the cylinder 22, and a motor box 25 disposed behind the cylinder 22 and the screw 23. Although not shown, the motor box 25 contains a metering motor that rotates the screw 23 about its central axis to accumulate a predetermined amount of molding material at the tip of the cylinder 22, an injection motor that moves the screw 23 forward and backward in both directions toward and away from the mold device 101, a pressure detection sensor that detects the pressure that the screw 23 receives from the molding material, and other components.

[0037] In this case, the direction approaching the fixed platen 32a of the mold clamping unit 31 to which the fixed mold 102 of the mold device 101 is attached is defined as the front side, and the direction moving away from the fixed platen 32a is defined as the rear side. Therefore, in Fig. 1, when looking at the injection unit 21 located to the right of the fixed platen 32a, the left direction approaching the fixed platen 32a is the front side, and the right direction moving away from the fixed platen 32a is the rear side.

[0038] The cylinder 22 is provided with a supply port 22a on the rear side, in front of the motor box 25, to which a hopper can be attached for feeding molding material into the cylinder 22. A nozzle 22b, whose cross-sectional area decreases on the front side, is provided at the tip of the cylinder 22 close to the mold device 101. A water-cooled cylinder 22c, such as a water-cooled cylinder, can be provided near the supply port 22a.

[0039] The heater 24, which is disposed around the cylinder 22 including the nozzle 22b, can be divided into a plurality of sections in the axial direction of the cylinder as shown in the figure, so that the inside of the cylinder 22 inside each heater section can be heated to a different temperature. Each heater section can be provided with a temperature detector.

[0040] A backflow prevention ring (not shown) may be disposed around a constricted portion formed by partially reducing the outer diameter of the tip of the screw 23. The backflow prevention ring prevents the molding material sent forward as it moves forward and backward together with the screw 23 from flowing backward. This backflow prevention ring moves back and forth relative to the screw 23 in response to the pressure it receives from molding material located forward or backward, thereby allowing only the flow of molding material from the rear to the front.

[0041] In the injection device 21 having such a configuration, the molding material introduced into the cylinder 22 from the supply port 22a is heated by the heater 24 on the outer periphery of the cylinder 22 and melted by the rotation of the screw 23 driven by the metering motor, and is sent forward inside the cylinder 22 and accumulated at the tip of the cylinder 22. At this time, the screw 23 is displaced backward by the injection motor, forming a space at the tip of the cylinder 22 where the molding material can be accumulated.

[0042] Thereafter, by displacing the screw 23 forward, the molding material at the tip of the cylinder 22 is injected through the nozzle 22b toward the mold device 101. Further thereafter, pressure is applied to the molding material filled in the cavity of the mold device 101 through the molding material remaining at the tip of the cylinder 22, thereby performing a dwelling process. At this time, it is possible to replenish the molding material that has become deficient in the injection molding cavity of the mold device 101 due to the cooling contraction of the molding material.

[0043] Although this injection blow molding machine 1 is an inline screw type, it can also be a pre-plasticization type injection blow molding machine in which the plasticizing cylinder and plasticizing screw are structurally and functionally separated from the injection cylinder and injection plunger.

[0044] [Mobile device] The moving device 26 is provided, for example, below the motor box 25 of the injection device 21, and is an advance / retract drive mechanism for displacing the injection device 21 forward and backward relative to the fixed platen 32a. Various mechanisms can be used as the forward / backward drive mechanism that constitutes the moving device 26, but the moving device 26 shown in the figure is configured to include a hydraulic or other hydraulic pump 27, an electric or other pump operating motor 28 that operates the hydraulic pump 27, and a double-acting hydraulic cylinder 29 that receives hydraulic fluid from the hydraulic pump 27 and causes a piston rod 61b, the tip of which is fixed to the fixed platen 32a, to perform an extending and retracting motion.

[0045] The moving device 26 further includes a slide base 26a to which the above-mentioned hydraulic pump 27, pump actuation motor 28, and hydraulic cylinder 29 are attached, and a guide 26b that is laid on the base frame 2 and guides the linear movement of the slide base 26a. This allows the injection device 21 placed on the slide base 26a to move forward and backward.

[0046] The moving device 26 makes it possible to move the injection device 21 away from the mold device 101, or to move the injection device 21 closer to the mold device 101 and press the nozzle 22b of the cylinder 22 of the injection device 21 against the mold device 101 with a predetermined pressure, thereby performing a so-called nozzle touch.

[0047] [Mold clamping device] The mold clamping device 31 has a mold holding mechanism 32 having a fixed platen 32a, a movable platen 32b, and an intermediate mold support frame 32c, as well as an intermediate mold moving mechanism 61 that moves the intermediate mold support frame 32c relative to the fixed platen 32a, a platen moving mechanism 33 that moves the movable platen 32b relative to the fixed platen 32a, and a split mold opening / closing mechanism 62 that opens and closes the split mold of the movable mold 103. The intermediate mold moving mechanism 61 and the split mold opening / closing mechanism 62 will be described later with reference to FIGS. 2 to 5.

[0048] The mold holding mechanism 32 includes a fixed platen 32a located between the injection unit 21 and the mold unit 101, a movable platen 32b located between the fixed platen 32a and the mold unit 101, which is movable toward and away from the fixed platen 32a, and an intermediate mold support frame 32c located between the fixed platen 32a and the movable platen 32b, which is movable toward and away from the fixed platen 32a. The mold clamping unit 31 is also provided with one or more tie bars 32d extending from the fixed platen 32a toward a rear platen 34 (described later) to connect the fixed platen 32a and the rear platen 34. In this example, the movable platen 32b and the intermediate mold support frame 32c are guided by the tie bars 32d in their movement toward and away from the fixed platen 32a, but there are also cases where they are not guided by the tie bars 32d.

[0049] Of the mold holding mechanism 32, the fixed platen 32a is fixedly attached to the base frame 2. On the other hand, the movable platen 32b and the intermediate mold support frame 32c are each placed on a guide member 32e laid on the base frame 2, and can slide independently of each other in directions toward and away from the fixed platen 32a.

[0050] At a position where the movable platen 32b and the intermediate mold support frame 32c are separated from the stationary platen 32a, the movable mold 103 and the intermediate mold 104 of the mold device 101 are in a mold open state where they are open from the stationary mold 102. By moving the movable platen 32b and the intermediate mold support frame 32c toward the stationary platen 32a from this separated position, the movable mold 103 and the intermediate mold 104 are in a mold closed state where they are closed against the stationary mold 102, and by further moving the movable platen 32b and the intermediate mold support frame 32c toward the stationary platen 32a, the movable mold 103 and the intermediate mold 104 are in a mold clamped state where they are pressed against the stationary mold 102. Here, the direction in which the stationary mold 102 of the mold device 101 approaches the stationary platen 32a to which it is attached is referred to as the front side, and the direction in which the stationary mold 102 moves away from the stationary platen 32a is referred to as the rear side. In most parts of the mold clamping unit 31 except for the fixed platen 32a, in FIG. 1, the right side approaching the fixed platen 32a is the front side, and the left side away from the fixed platen 32a is the rear side.

[0051] The illustrated intermediate mold support frame 32c has a frame shape, such as a rectangle, when viewed from the front, and is provided with a rotation shaft 41 that is rotatably mounted and extends in the mold width direction (the front-to-back direction in FIG. 1) that is perpendicular to the front-to-back direction within a plane parallel to the horizontal plane. In this example, the axial direction of the rotation shaft 41 is parallel to the horizontal direction, but the axial direction of the rotation shaft 41 is not limited to this, and it may also be parallel to the vertical direction, for example.

[0052] Further, the intermediate mold support frame 32c is provided with an intermediate mold rotation mechanism that rotates the rotary shaft portion 41 and thereby rotates the intermediate mold 104. Although not shown, this intermediate mold rotation mechanism can be provided, for example, at the end of the rotary shaft portion 41, and in this example, it can be provided on one end portion 42a side.

[0053] The intermediate mold moving mechanism 61 that moves the intermediate mold support frame 32c relative to the fixed platen 32a can be configured, for example, as shown in Figures 2 to 5, by hydraulic cylinders 61a and piston rods 61b attached to the fixed platen 32a and the intermediate mold support frame 32c, respectively, and operated by a hydraulic pump driven by a motor. In this example, two pairs of hydraulic cylinders 61a and piston rods 61b are provided, positioned outside the fixed mold 102 and the intermediate mold 104 in the mold width direction, but one pair or three or more pairs may be provided. In the illustrated example, the intermediate mold moving mechanism 61 is attached to both the fixed platen 32a and the intermediate mold support frame 32c, but it may also be attached to both the movable platen 32b and the intermediate mold support frame 32c.

[0054] As shown in FIG. 1, the platen movement mechanism 33 of the mold clamping unit 31 includes a rear platen 34 arranged on the base frame 2, a mold clamping motor 35 provided on the rear platen 34, a motion conversion mechanism 36 that converts the rotational motion of the mold clamping motor 35 into linear motion in the displacement direction of the movable platen 32b, and a toggle mechanism 37 that amplifies the force transmitted to the motion conversion mechanism 36 and transmits it to the movable platen 32b.

[0055] Of these, the motion conversion mechanism 36 can be various mechanisms capable of converting rotational motion into linear motion. In this example, the motion conversion mechanism 36 includes a screw shaft 36a that is rotationally driven by the mold clamping motor 35 and a nut 36b that is threaded onto the screw shaft 36a. The motion conversion mechanism 36 can also be a ball screw. The toggle mechanism 37, which increases the transmission force from the motion conversion mechanism 36, is formed by connecting a plurality of links 37a to 37c that connect the nut 36b of the motion conversion mechanism 36 to the movable platen 32b, and these links 37a to 37c are swingably connected by joints. The number and shapes of the links and joints can be changed as appropriate, but as shown in FIG. 1, a pair of link groups consisting of the links 37a to 37c located above and below the crosshead 37d are swingably connected to the crosshead 37d that is connected to the nut 36b and extends in the vertical direction.

[0056] In addition to the above-described mold clamping motor 35, a mold thickness adjustment motor 38 can also be provided on the rear platen 34. This mold thickness adjustment motor 38 functions to adjust the distance between the fixed platen 32a and the rear platen 34, which is movably mounted on the base frame 2, by applying a rotational driving force to a screw shaft 36a and a nut 36b connected to an extension portion of each tie bar 32d of the above-described mold holding mechanism 32. This makes it possible to adjust the mold thickness so that a desired mold clamping force can be applied to the mold device 101, even when replacing the mold device 101 or when the thickness of the mold device 101 is changed due to temperature changes. Although not shown in the drawings, mold thickness adjustment can also be achieved even if the fixed platen side is made movable on the base frame 2 and the rear platen side is fixed.

[0057] As shown in Figures 2 to 5, the mold clamping device 31 is equipped with a split mold opening / closing mechanism 62 that has a hydraulic cylinder 62b, a piston rod 62a, etc., and drives the split mold of the movable mold 103 back and forth in the mold width direction to open and close it.

[0058] The illustrated mold clamping unit 31 is a horizontal type in which the moving direction of the movable platen 32b is parallel to the horizontal direction, but it may also be a vertical type in which the moving direction is vertical.

[0059] [Operation of injection blow molding machine] The injection blow molding machine 1 described above can be operated to perform the steps shown in the flowchart of FIG. 8, as an example. With the mold device 101 in the mold open state shown in Figures 2 and 3, a mold closing process is performed in which the platen moving mechanism 33 moves the movable platen 32b toward the fixed platen 32a, and the intermediate mold moving mechanism 61 moves the intermediate mold support frame 32c toward the fixed platen 32a (step S10).

[0060] Next, with a predetermined amount of molding material already accumulated and placed inside injection unit 21 by measuring during the previous molding, which will be described later, a clamping process is carried out in which mold unit 101 is clamped using clamping unit 31, as shown in Figures 4 and 5 (step S20). In the clamping process, an injection molding cavity is defined between fixed mold 102 and intermediate mold 104, and a blow molding cavity is defined between movable mold 103 and intermediate mold 104.

[0061] Then, the screw 23 advances to perform an injection process in which the molding material is filled into the injection molding cavity of the mold device 101 (step S30). In the injection process, after the molding material has been filled into the injection molding cavity, the screw 23 is further advanced to perform a pressure hold in which the molding material inside the tip of the injection device 21 is maintained at a predetermined pressure. The molding material filled into the injection molding cavity is then cooled and solidified. This results in a preform PF being molded in the injection molding cavity. At this time, molding material separately charged into the injection device 21 is melted while being sent toward the tip of the injection device 21 by the rotation of the screw 23 under heating by the heater 24, and a predetermined amount of molding material is metered and placed at the tip.

[0062] In parallel with the injection process, a blowing process is carried out in the blow molding cavity. A preform PF that has already been molded in the injection molding cavity before the intermediate mold 104 is inverted is placed in the blow molding cavity. In the blowing process, a fluid such as air or other gas is supplied to the preform PF, causing it to expand in the blow molding cavity and mold a molded product MP.

[0063] In this blowing process, after the molded product MP is molded, a fluid is supplied to the communication hole 103f by the fluid supply mechanism, and a detection process is performed in which the pressure of the fluid is detected by the detection mechanism when the fluid is caused to flow through the communication hole 103f (step S31). Next, the detection mechanism determines whether the detected pressure has been below a predetermined threshold for a predetermined time (step S32). If the detected pressure has been below the predetermined threshold for a predetermined time (step S32-YES), the detection mechanism instructs the control unit to stop injection blow molding (step S33), and the control unit stops injection blow molding. When the control unit receives the instruction to stop injection blow molding from the detection mechanism, if the injection blow molding machine 1 is equipped with a display unit, the control unit can display an alarm on the display unit indicating that a defective product has been produced. On the other hand, if the detected pressure does not fall below the predetermined threshold for a predetermined period of time (step S32-No), the detection mechanism proceeds to the process described below (step S40) without instructing the control unit to stop injection blow molding.

[0064] Next, the platen moving mechanism 33 and the intermediate mold moving mechanism 61 of the mold clamping device 31 are operated to move the movable platen 32b and the intermediate mold support frame 32c away from the fixed platen 32a, respectively, thereby opening the fixed mold 102 and the intermediate mold 104 and performing the mold opening process of opening the intermediate mold 104 and the movable mold 103 (step S40).

[0065] After the mold opening step, the split mold opening / closing mechanism 62 is used to open the split mold of the movable mold 103 and remove the molded product MP, and then a split mold opening / closing step is performed in which the split mold of the movable mold 103 is closed (step S50). Also, here, an intermediate mold rotation step is performed in which the intermediate mold 104 is inverted by the intermediate mold rotation mechanism (step S60). As a result, the core mold 104a of the intermediate mold 104 on the side from which the molded product MP was collected in the split mold opening and closing step faces the fixed-side concave mold portion 102a of the fixed mold 102. On the other hand, the core mold 104a of the intermediate mold 104 on the side from which the preform PF was molded in the injection step faces the movable-side concave mold portion 103a of the movable mold 103 while holding the preform PF. The intermediate mold rotating step can be carried out at approximately the same time as the split mold opening and closing step, or before or after the split mold opening and closing step.

[0066] In injection molding using the injection blow molding machine 1, the mold closing process, mold clamping process, injection process, blowing process, mold opening process, split mold opening / closing process, and intermediate mold rotating process are repeatedly performed. Furthermore, in the method for detecting molding defects of this embodiment, by performing the detection process of step S31 described above, if a molding defect occurs during blow molding, it is possible to detect that a defective molded product has been produced. [Explanation of symbols]

[0067] 1 Injection blow molding machine 2 base frame 21 Injection device 22 cylinders 22a Supply port 22b nozzle 22c water-cooled cylinder 23 screw 24 Heater 25 Motor box 26 Mobile Devices 26a Slide Base 26b Guide 27 Hydraulic Pump 29 Hydraulic Cylinder 31 Mold clamping device 32a Fixed Platen 32b Movable platen 32c Intermediate mold support frame 32d tie bar 32e Guide member 33 Platen movement mechanism 34 Rear platen 35 Mold clamping motor 36 Motion conversion mechanism 36a Screw shaft 36b Nut 37 Toggle mechanism 37a~37c Link 37d Crosshead 38 Mold thickness adjustment motor 41 Rotating shaft 42a One end 61 Intermediate mold movement mechanism 61a Hydraulic cylinder 61b Piston rod 62 Split mold opening and closing mechanism 62a Piston rod 62b Hydraulic cylinder 63a, 63b Split connecting member 101 Mold equipment 102 Fixed mold 102a Fixed side concave part 102b (Fixed side concave part) opening Gate 102c 103 Movable mold 103a Movable side concave part 103b Split part 103c Bottom mold part 103d Opening (of the movable concave part) 103e 1st surface 103f communication hole 104 Intermediate mold 104a Core mold 104b Plate-shaped part 104c Base 104d Blowing slit PF preform MP molded product

Claims

1. An injection blow molding machine to which a fixed mold, an intermediate mold, and a movable mold are attached, the movable mold has a movable-side concave mold portion that forms a cavity space, the movable-side concave portion has a communication hole that communicates the outside of the movable-side concave portion with the inside of the cavity space, The injection blow molding machine includes a fluid supply mechanism that supplies fluid to the communication hole, and a detection mechanism that detects the pressure of the fluid within the communication hole when the fluid is supplied from outside the cavity space through the communication hole toward the inside of the cavity space.

2. the injection blow molding machine is provided with a control unit that controls injection blow molding, 2. The injection blow molding machine according to claim 1, wherein the detection mechanism instructs the control unit to stop injection blow molding when the detected pressure falls below a predetermined threshold for a predetermined period of time.

3. the injection blow molding machine is provided with a control unit that controls injection blow molding, 2. The injection blow molding machine according to claim 1, wherein the detection mechanism instructs the control unit to stop the ejector from ejecting the molded product when the detected pressure falls below a predetermined threshold for a predetermined period of time.

4. 4. The injection blow molding machine according to claim 1, wherein the radial position of the opening of the communicating hole is located radially outward from the radially inner end of the opening of the movable-side concave portion.

5. the movable concave portion has a bottom portion and a plurality of split portions adjacent to the bottom portion, 5. The injection blow molding machine according to claim 1, wherein the opening of the communication hole is disposed in the bottom mold portion.

6. A method for detecting molding defects in a molded product molded using the injection blow molding machine according to any one of claims 1 to 5, comprising: A method for detecting molding defects, comprising a step of blow-molding a molded product in the cavity space within the movable-side concave mold portion, and then detecting the pressure of the fluid supplied to the communicating hole by the fluid supply mechanism with the detection mechanism.

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