Method for Molding Container Using Injection Stretch Blow Molding Machine

Abstract

The present invention enables injection by an injection device to be carried out in an early stage while obviating nozzle touch, and shortens the molding cycle of an injection stretch blow molding machine. In the present invention, an injection device 20, which is designed to perform injection when a value counted up by a timer reaches a set count value, is linked and fixed to a hot runner device 19 of an injection stretch blow molding machine 1. The count start point of the timer is set to: a stage in which a rotating plate rotates; a stage in which the rotating plate is made to stop rotating and is non-rotatably fixed; or a stage in which mold clamping of an upper mold and a lower mold begins.

Claims

1. A method for molding a container using an injection stretch blow molding machine, the injection stretch blow molding machine including: a clamping plate that is guided by a tie bar erected on a lower base plate so as to be movable upward and downward in a vertical direction of the molding machine above the lower base plate; an intermediate base plate that is guided by the tie bar so as to be movable upward and downward in the vertical direction of the molding machine under the clamping plate; a rotating plate that is attached under the intermediate base plate in a freely rotatable manner, the rotating plate having a rotation axis direction coinciding with the vertical direction of the molding machine, the rotating plate having a lip mold for forming a mouth portion of the container in each of three directions on a bottom surface thereof; and a rotary drive motor that is disposed at a center of a top of the intermediate base plate and is caused to intermittently rotate the rotating plate every 120 degrees so as to stop the lip molds at three stop positions, wherein when a container is molded by the injection stretch blow molding machine in which the lip molds stop at an injection molding unit, a stretch blow molding unit, and an ejection unit as the stop positions, the injection molding unit of the injection stretch blow molding machine includes: a lower mold that is a cavity mold disposed on a side of an injection device, a hot runner nozzle of a hot runner device installed in the molding machine being disposed so as to face a bottom of the lower mold; an upper mold that is movable upward and downward in the vertical direction of the molding machine, the upper mold being a core mold that descends through the lip mold situated in the injection molding unit and forms an injection mold having a preform forming space therein with the lower mold on which the lip mold is overlaid; and a clamping device that clamps the upper mold and the lower mold on which the lip mold that passes the upper mold is overlaid, the method comprising: injecting a molten resin into the injection mold constituted of the upper mold, the lip mold situated in a position corresponding to the injection molding unit by a turn of the rotating plate, and the lower mold, to mold a preform; transferring the preform that is molded in the injection molding unit and held by the lip mold to the stretch blow molding unit by the turn of the rotating plate, and molding a container in the stretch blow molding unit by stretching and blowing the preform; and transferring the container that is molded in the stretch blow molding unit and held by the lip mold to the ejection unit by the turn of the rotating plate, and releasing the container from the lip mold in the ejection unit, wherein the injection device is connected and fixed to the hot runner device of the injection stretch blow molding machine, the injection device performing an injection operation when a count-up value of a timer has reached a set count value, and the timer sets a count start point in any of a stage of turning the rotating plate, a stage of stopping the rotating plate and fixing the rotating plate in a non-rotatable manner, and a stage of starting clamping the upper mold and the lower mold.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0066] FIGS. 1A-1C show an injection stretch blow molding machine that embodies the present invention, in which FIG. 1A is an explanatory view of an injection molding unit viewed from the front, FIG. 1B is an explanatory view of the injection molding unit viewed from the side, and FIG. 1C is an explanatory view showing the disposition of the injection molding unit, a stretch blow molding unit, and an ejection unit.

[0067] FIG. 2 is an explanatory view showing a connected hot runner device and injection device.

[0068] FIG. 3 is an explanatory view of the connection fixation between a main nozzle of the hot runner device and a nozzle of the injection device.

[0069] FIG. 4 is an explanatory view showing the connection fixation between the main nozzle and the nozzle in cross section.

[0070] FIGS. 5A-5B show fixation of a rotating plate, in which FIG. 5A is an explanatory view showing a state before a descent of a lock pin, and FIG. 5B is an explanatory view showing a state after the descent of the lock pin.

[0071] FIGS. 6A-6B show clamping between an upper mold and a lower mold, in which FIG. 6A is an explanatory view showing a point in time when the upper mold descends, and FIG. 6B is an explanatory view showing a state after the descent of the upper mold.

[0072] FIG. 7 is an explanatory view showing a state of overlapping between a molten resin feeding step and other steps.

[0073] FIGS. 8A-8B show opening of the upper mold and the lower mold, in which FIG. 8A is an explanatory view showing a point in time when the upper mold ascends, and FIG. 8B is an explanatory view showing a state after the ascent of the upper mold.

[0074] FIGS. 9A-9B show a blow mold clamping step, in which FIG. 9A is an explanatory view showing a state of moving blow molds in a clamping direction, and FIG. 9B is an explanatory view showing a state of the clamped blow molds.

[0075] FIGS. 10A-10B show a stretch blow step, in which FIG. 10A is an explanatory view during a stretch blow, and FIG. 10B is an explanatory view of blow discharge.

[0076] FIGS. 11A-11B show a blow mold opening step, in which FIG. 11A is an explanatory view showing a state before the blow molds start opening, and FIG. 11B is an explanatory view showing a state of opening the blow molds.

[0077] FIG. 12 is an explanatory view of the hot runner device and the injection device in a state of performing a nozzle touch.

[0078] FIG. 13 is an explanatory view of a nozzle touch portion between the main nozzle of the hot runner device and the nozzle of the injection device.

[0079] FIG. 14 is an explanatory view showing the nozzle touch between the main nozzle and the nozzle in cross section.

[0080] FIG. 15 is an explanatory view of an injection mold shown in cross section.

DESCRIPTION OF EMBODIMENT

[0081] The present invention will be described in detail on the basis of an embodiment shown in FIGS. 1A-1C to 11A-11B. FIGS. 1A-1C show an injection stretch blow molding machine 1. The injection stretch blow molding machine 1 includes an intermediate base plate 4 that is movable upward and downward above a lower base plate 2 by being guided by tie bars 3 erected on the lower base plate 2, a rotating plate 6 that is attached on a bottom surface of the intermediate base plate 4 in a rotatable manner and has lip molds 5 each of which constitutes one of a pair of split molds to form a mouth portion of a container in three directions of the bottom surface, and a rotary drive motor 7 that is disposed at the center of the top of the intermediate base plate 4 and intermittently rotates and stops the rotating plate 6 having the three lip molds every 120 degrees.

[0082] The lip molds 5 circularly move about the center of the rotating plate, as the center of a rotation axis, by the rotation of the rotating plate 6, and, as shown in FIG. 1C, stop at the positions of an injection molding unit 8, a stretch blow unit 9, and an ejection unit 10. These three stations are disposed in positions at rotation angles of 120 degrees apart. FIG. 1C schematically shows the disposition of the three stations, for ease of explanation.

[0083] (Injection Molding Unit)

[0084] The aforementioned injection molding unit 8 of the injection stretch blow molding machine 1 has a lower mold 11, i.e., a cavity mold disposed on the lower base plate 2, an upper mold 12 that is movable downward and upward above the lower mold 11 and descends through the lip mold 5 stopped in the position corresponding to the injection molding unit 8, and a clamping device 13 that clamps the upper mold 12 and the lower mold 11 through the lip mold 5. The lip mold 5 that is situated in the position corresponding to the injection molding unit 8 descends together with the rotating plate 6 in a state of being situated in a descent line of the upper mold 12, so as to be overlaid on the lower mold 11.

[0085] An injection device, which will be described later, is disposed so as to correspond to the injection molding unit 8 shown in FIG. 1C, and the aforementioned lower mold 11 is situated on the side of the injection device. Note that, being situated on the side of the injection device does not mean that being attached to the injection device, but represents the positional relationship between the movable upper mold disposed on the side of a clamping device, which will be described later, and the lower mold disposed on the side of the injection device. When viewing the disposition of the three stations from above, since the injection molding unit 8 is disposed so as to correspond to the injection device and the injection molding unit 8 is provided with the lower mold 11, the lower mold 11 is situated on the side of the injection device.

[0086] The upper mold 12 descends through the descending lip mold 5, while receiving a clamping force from a clamping plate 14 that is descending by the operation of the clamping device 13. Furthermore, a core portion (a projection portion protruding downward) of the upper mold 12 is fitted into the cavity portion (a recessed portion) of the lower mold 11 through the lip mold 5 that is overlaid on the lower mold 11. The upper mold 12 is overlaid on the lip mold 5 in this manner, and the upper mold 12, the lip mold 5, and the lower mold 11 form an injection mold 15 in a state that the clamping force is applied from the clamping device 13 through the clamping plate 14 (see FIG. 15).

[0087] The aforementioned clamping device 13 pushes the upper mold 12 downward by applying the clamping force from above to the upper mold 12 through the clamping plate 14, as described above. When the descended upper mold 12 and lip mold 5 form the aforementioned injection mold 15 with the lower mold 11, the clamping force is changed to a high-pressure clamping force, thereby applying the high-pressure clamping force to the injection mold 15 constituted of the three molds.

[0088] (Stretch Blow Molding Unit)

[0089] The stretch blow molding unit 9 includes a pair of openable blow molds 16, a blow mold clamping cylinder 17 that performs closing and opening the blow molds 16 and changes the clamping force to the blow molds to the high-pressure clamping force and applies the high-pressure clamping force to the clamped blow molds 16, and a stretch blow mechanism that supplies stretch blow air into a stretch rod and the inside of the closed blow molds (see FIGS. 9A-9B and 10A-10B).

[0090] The lip mold 5 that is situated in a position corresponding to the stretch blow molding unit 9 by a stop of the rotating plate 6 is fitted from above into the blow molds 16 in a clamped state by descent of the rotating plate 6, so that the lip mold 5 is interposed between top edges of the pair of blow molds 16. After the lip mold 5 has been interposed between the blow molds 16, the clamping force is changed to the high-pressure clamping force, as described above, and thereafter the operation of the stretch blow device is performed.

[0091] (Ejection Unit)

[0092] The aforementioned ejection unit 10 is a portion to open the lip mold 5 that stops in a position corresponding to the ejection unit 10. By opening the lip mold 5, a mouth portion of a molded container is released from the mold, which will be described later, to send the container out of the molding machine. Note that, the lip mold 5 is clamped after releasing the mouth portion of the molded container.

[0093] (Hot Runner Device and Injection Device)

[0094] FIG. 2 shows a hot runner device 19 and an injection device 20 that are installed below the lower mold of the injection molding unit of the injection stretch blow molding machine. FIG. 3 shows a connection portion between the hot runner device 19 and the injection device 20.

[0095] As the installation of the injection device 20, the injection device 20 is disposed on a table through a guide rail 21, and a hydraulic cylinder 22 one end of which is fixed is connected to the injection device 20, just as with the above-described conventional one.

[0096] Note that, this embodiment executes an injection without performing a nozzle touch, as described later. The reason why this installation is adopted is that, when performing maintenance, the injection device 20 is required to be isolated from the hot runner device 19 and moved backward by the operation of the hydraulic cylinder 22.

[0097] As shown in FIGS. 2 and 3, the hot runner device 19 and the injection device 20 are connected therebetween and fixed. FIG. 4 shows a state of connection fixation between the hot runner device 19 and a nozzle 23 of the injection device 20 in cross section. As shown in the drawing, the nozzle 23 and a connection flange 26, which is engaged with a main nozzle 25 of the hot runner device 19, are fixed with bolts.

[0098] Since a discharge port of the nozzle 23 and an injection port of the main nozzle 25 are opposed and tightly connected without making a gap therebetween, a resin channel through which a molten resin fed from the nozzle 23 enters the main nozzle 25, passes through branched runners of the hot runner device 19, and reaches the bottom of the aforementioned lower mold 11 from the plurality of erected hot runner nozzles 27 is always formed.

[0099] The operation of the rotary injection stretch blow molding machine will be described below.

[0100] (Rotating Plate Turning Step: FIGS. 1A-1C)

[0101] As shown in FIGS. 2A-1C, the rotating plate 6 turns at 120 degrees in a state that the clamping plate 14, the upper mold 12, and the intermediate base plate 4 are situated in an upper position of a standby height. A rotating plate turning step refers to the time from when the rotating plate 6 starts turning to when the rotating plate 6 stops after a turn of 120 degrees. In the rotating plate turning step, for example, the lip mold 5 that holds a preform molded by the injection molding unit 8 is transferred to the stretch blow molding unit 9, the lip mold 5 that holds a blow-molded container molded by the stretch blow molding unit 9 is transferred to the ejection unit 10, and the lip mold 5 that is situated in the ejection unit 10 is transferred to the injection molding unit 8.

[0102] (Rotating Plate Fixing Step: FIG. 5A-5B)

[0103] Upon stopping the turn of the rotating plate 6, the operation shifts from the rotating plate turning step to a rotating plate fixing step.

[0104] In the rotating plate fixing step, the rotating plate 6 is fixed to prevent an unintended turn, such that the aforementioned lip molds 5 are correctly situated in predetermined positions corresponding to the injection molding unit 8, the stretch blow molding unit 9, and the ejection unit 10. In the injection molding unit 8, the lip mold 5 is fixed so as not to deviate in a circular movement direction in a state of being situated in a position corresponding to a descent line of the upper mold 12.

[0105] To be more specific, as a stopper of the rotating plate 6 when the lip mold 5 is situated in a position corresponding to the injection molding unit 8, a lock pin 29 descends by the operation of a rotating plate lock cylinder 28 provided in the intermediate base plate 4. The lock pin 29 is engaged in a lock pin bush 30 provided in a required portion of the rotating plate 6, in order to fix the rotating plate 6 without rotation.

[0106] (Upper Mold and Lower Mold Clamping Step: FIGS. 6A-6B)

[0107] After the fixation of the rotating plate 6 by the aforementioned lock pin 29, the operation shifts from the rotating plate fixing step to an upper mold and lower mold clamping step. In the clamping step, after the fixation of the rotating plate 6 is completed in the fixing step, the rotating plate 6 descends by descent of the intermediate base plate 4. The upper mold 12 disposed above the rotating plate 6 descents so as to pass the inside of a container mouth portion molding portion of the lip mold 5, while being pushed downward by descent of the clamping plate 14, in other words, while receiving a clamping force of the clamping device 13 through the clamping plate 14.

[0108] The core portion of the upper mold 12 is overlaid on the lip mold 5 in such a manner as to be fitted into the inside of the lower mold 11 through the lip mold 5, as well as overlaying the lip mold 5 on the lower mold 11, so that a combination of the upper mold 12, the lip mold 5, and the lower mold 11 constitutes the injection mold 15 in a state of receiving the clamping force from the clamping device 13. When the injection mold 15 is obtained, the clamping device 13 changes the clamping force to a high-pressure clamping force and applies the high-pressure clamping force to the injection mold 15. The upper mold and lower mold clamping step is completed, when the change of the pressure of the clamping force to the high-pressure clamping force is completed.

[0109] (Molten Resin Feeding Step)

[0110] The injection operation of the aforementioned injection device 20 is controlled using a timer provided in a not-shown control device. When the timer counts up and the count-up value reaches (coincides with) a set count value having been set in advance, the injection device performs an injection.

[0111] The timer provided in the aforementioned control unit can set the count start point in any of the stage of turning the rotating plate 6, the stage of stopping the rotating plate 6 and fixing the rotating plate 6 in a non-rotatable manner, and the stage of starting clamping the upper mold and the lower mold.

[0112] Since a count start point 31 at which the timer starts counting up is set in any of the stage of turning the rotating plate 6, the stage of stopping the rotating plate 6 and fixing the rotating plate 6 in a non-rotatable manner, and the stage of starting clamping the upper mold and the lower mold, a beginning part of a molten resin feeding step C, which is constituted of a count-up time A starting from the count start point 31 and an injection time B, may be overlapped with an upper mold and lower mold clamping step D, or may also be overlapped even with a rotating plate fixing step E, i.e., a preceding step of the upper mold and lower mold clamping step D, or may also be overlapped even with a rotating plate turning step F, i.e., the preceding step of the rotating plate fixing step E. Thus, it is possible to significantly shorten a waiting time for the injection, and hence shorten a time to complete the injection in the injection molding unit 8 more than before.

[0113] In this embodiment, as shown in FIG. 7, the count start point 31 is set at the stage of starting clamping the upper mold and the lower mold (the beginning of the upper mold and lower mold clamping step D). The set count value is set at 0.30 seconds, and thus the injection device starts an injection after counting up 0.30 seconds, as the set count value. Note that, the injection time itself is not shortened but the same as before, and the injection device continues the injection even after the high-pressure clamping force for the injection mold is achieved.

[0114] (Cooling Step)

[0115] After the completion of the aforementioned molten resin feeding step, the operation shifts to a cooling step. In the cooling step, the molten resin that is injected into the injection mold clamped with the high pressure is forcefully cooled for a preset period of time, to obtain a preform the temperature of which is reduced to a predetermined temperature.

[0116] (Upper Mold and Lower Mold Opening Step: FIGS. 8A-8B)

[0117] After the completion of the cooling step, the operation shifts to an upper mold and lower mold opening step. In the upper mold and lower mold opening step, as shown in FIGS. 8A-8B, an ascent of the clamping plate 14 releases the application of the high-pressure clamping force from the clamping device 13. The upper mold 12 ascends, and at the same time the rotating plate 6 and the lip mold 5 ascend to open the mold. The preform is released from the lower mold 11. The rotating plate 6 that holds the mouth portion of the preform at the lip mold 5 ascends to a predetermined position in which the rotating plate 6 can turn, and stop.

[0118] (Operation of Stretch Blow Unit)

[0119] (Blow Mold Clamping Step: FIGS. 9A-9B)

[0120] When the aforementioned upper mold and lower mold opening step is completed in the injection molding unit 8, the rotating plate 6 itself starts the rotating plate turning step and turns at 120 degrees, so that the lip mold 5 that holds the mouth portion of the preform circularly moves to the stretch blow molding unit. During the rotating plate turning step, as shown in FIGS. 9A-9B, the stretch blow molding unit 9 starts the operation of clamping the pair of blow molds 16 with application of a clamping force from the blow mold clamping cylinder, to fit the pair of blow molds 16 on a bottom mold 32. Forward movement and fit of the pair of blow molds 16 on the bottom mold 32 are completed during the rotating plate turning operation. The blow mold clamping cylinder continues applying the clamping force, even after the fit of the molds.

[0121] As described above, even when stretch blow molding unit 9 completes assembling the blow molds 16 and the bottom mold 32, the rotating plate 6 is in the middle of a 120-degree turn. Even when, in the injection molding unit 8, the next lip mold 5 is situated in a position corresponding to the injection molding unit 8 and the rotating plate 6 is stopped and fixed in the position, the preform held by the lip mold 5 is on standby above the blow molds 16 in the stretch blow molding unit 9, because the rotating plate itself is situated in an upper position. By a descent of the rotating plate to clamp the upper mold, the lip mold, and the lower mold in the injection molding unit 8, the lip mold 5 that is situated in a position corresponding to the stretch blow molding unit 9 is assembled to the blow molds 16 from above.

[0122] When the lip mold 5 is assembled to the blow molds 16 so as to insert the preform into the blow molds, the clamping force applied to the blow molds 16 is changed to a high-pressure clamping force by the operation of the blow mold clamping cylinder 17. The change of the clamping force to the high-pressure clamping force is performed concurrently with the change of the clamping force to the high-pressure clamping force in the injection molding unit 8.

[0123] (Stretch Blow Step: FIGS. 10A-10B)

[0124] The aforementioned blow mold clamping step is completed when the clamping force applied to the blow molds 16 is changed to the high-pressure clamping force, and the operation shifts to a stretch blow step in which stretching and blowing are performed on the preform. In the stretch blow step, as shown in FIGS. 10A-10B, a stretch blow mechanism 33 descends from above the lip mold and is overlaid on the lip mold 5. A stretch rod 34 of the stretch blow mechanism 33 is inserted into the blow molds and stretches a preform 35 inside the blow molds, while a blow air supply 36 is performed, to form a container as a product having a stretched and blown shape inside the blow molds. The supply of stretch blow air is stopped after a required time has elapsed. The stretch rod 34 is retracted, and the stretch blow mechanism 33 ascends to an upper standby position. A blow air discharge 37 in which the blow air is discharged from the container inside the blow molds is performed for a predetermined period of time, and thus the stretch blow step is completed.

[0125] (Blow Mold Opening Step: FIGS. 11A-11B)

[0126] After the completion of the stretch blow step, the operation shifts to a blow mold opening step. In the blow mold opening step, the application of the clamping force is released by the operation of the aforementioned blow mold clamping cylinder 17, to release the container from the opened blow molds 16. The blow molds are opened before an injection is completed in the aforementioned injection molding unit 8. By an ascent of the rotating plate 6, the container formed by stretch blow molding ascends in a state of being held by the lip mold 5, and the container is released from the blow molds 16. The ascent of the rotating plate 6 at this time is the same as the ascent of the rotating plate 6 when opening the upper mold and the lower mold in the injection molding unit 8.

[0127] The rotating plate 6 that has moved the container upward by the lip mold and has released the container from the molds in the stretch blow molding unit turns again at 120 degrees, upon completing the upper mold and lower mold opening step in the aforementioned injection molding unit 8. Since a process of the injection molding unit takes long time, the lip mold is transferred from the stretch blow molding unit to the ejection unit after the completion of the upper mold and lower mold opening step in the injection molding unit 8. As a matter of course, the 120-degree turn also serves as an operation to circularly move the lip mold that has corresponded to the ejection unit 10 to the injection molding unit 8, and an operation to circularly move the lip mold that has corresponded to the injection molding unit 8 to the stretch blow molding unit 9 while holding a preform. Note that, for the sake of ease of explanation, the drawings that show the movement of the blow molds in the stretch blow step omit the lip molds.

[0128] (Ejection Step in Ejection Unit)

[0129] When the rotating plate 6 turns at 120 degrees and stops, the lip mold 5 that holds the container formed by stretch blow molding is shifted to a position corresponding to the ejection unit 10. The lip mold 5 is opened in the ejection unit 10 at the time when, taking the operation of the injection molding unit 8 as an example, the clamping force is changed to a high-pressure clamping force after the completion of clamping the upper mold and the lower mold and the like, so as to release the mouth portion of the held bottle-shaped container from the molds and eject the container (send the container out of the molding machine).

[0130] In the above-described embodiment, the count start point 31 is set in the stage of starting clamping the upper mold and the lower mold, and the set count value is 0.30 seconds. After counting up the set count value, i.e., 0.30 seconds, the injection device performs an injection, but the present invention is not limited to this embodiment.

REFERENCE SIGNS LIST

[0131] 1 injection stretch blow molding machine

[0132] 4 intermediate base plate

[0133] 5 lip mold

[0134] 6 rotating plate

[0135] 8 injection molding unit

[0136] 9 stretch blow molding unit

[0137] 10 ejection unit

[0138] 11 lower mold

[0139] 12 upper mold

[0140] 13 clamping device

[0141] 14 clamping plate

[0142] 15 injection mold

[0143] 16 blow mold

[0144] 19 hot runner device

[0145] 20 injection device

[0146] 23 nozzle

[0147] 25 main nozzle

[0148] 26 connection flange

[0149] 27 hot runner nozzle

[0150] 28 rotating plate lock cylinder

[0151] 29 lock pin

[0152] 31 count start point

[0153] 32 bottom mold

[0154] 34 stretch rod

[0155] 35 preform

[0156] 36 blow air supply

[0157] 37 blow air discharge

[0158] A count-up time

[0159] B injection

[0160] C molten resin feeding step

[0161] D upper mold and lower mold clamping step

[0162] E rotating plate fixing step

[0163] F rotating plate turning step