STRETCH BLOW MOLDING APPARATUS AND BLOW MOLDING METHOD

Abstract

When an injection stretch blow molding machine in which the molding cycle is tried to be shortened manufactures hollow molded bodies, blow molding in which shaping and cooling are simultaneously performed by blowing compressed air from a single compressed air supply source while discharging compressed air is performed to achieve energy saving for manufacturing hollow molded bodies.

A blowing apparatus 10 of a stretch blow molding apparatus 11 includes a compressed air supply source 32 configured to send out compressed air adjusted to have an air pressure at which an object to be shaped e is inflated to be shaped into a hollow molded body, an inflow passage 33 through which the compressed air from the compressed air supply source 32 flows to the internal space of the object to be shaped e disposed in a blow mold 8, and a non-closed outflow passage 34 through which the compressed air flows out from the internal space of the object to be shaped e to a discharging space outside the blow mold. In the entire process of the blowing operation by the blowing apparatus 10, a compressed air flow passage 36 is formed through which the compressed air from the compressed air supply source 32 flows through the inflow passage 33 and the internal space of the object to be shaped e and through the outflow passage 34 into the discharging space. Shaping and cooling are simultaneously performed by blowing the compressed air adjusted to have an air pressure at which the object to be shaped e being in the form of a preform is inflated to be shaped into the hollow molded body throughout the entire process of the blowing operation.

Claims

1. A stretch blow molding apparatus comprising: a blow mold in which an object to be shaped, which is in a form of a preform that can be shaped at a high temperature, can be disposed and which has a hollow molded body shape-forming surface on an inner surface thereof; a stretching apparatus configured to cause a rod to enter the object to be shaped, which is disposed in the blow mold and is in the form of the preform, inward; and a blowing apparatus configured to blow compressed air inward of the object to be shaped being in the form of the preform, where the stretch blow molding apparatus performs: a stretching operation of stretching the object to be shaped being in the form of the preform in a rod axial direction by causing the rod to enter the object; and a blowing operation including shaping by which the object to be shaped that is stretched by the rod is inflated to shape the object to be shaped into a hollow molded body and cooling by ventilating an internal space of the object to be shaped the blowing apparatus includes: a compressed air supply source configured to send out compressed air adjusted to have an air pressure at which the object to be shaped being in the form of the preform is inflated to be shaped into the hollow molded body; an inflow passage through which the compressed air from the compressed air supply source flows to an internal space of the object to be shaped disposed in the blow mold; and a non-closed outflow passage through which the compressed air flows out from the internal space of the object to be shaped to a discharging space outside the blow mold in an entire process of the blowing operation, a compressed air flow passage is formed through which the compressed air from the compressed air supply source flows through the inflow passage and the internal space of the object to be shaped and through the outflow passage into the discharging space; and the compressed air flow passage is a flow passage in which the shaping of blowing the compressed air adjusted to have an air pressure, at which the object to be shaped being in the form of the preform is inflated to be shaped into the hollow molded body, to inflate the object to be shaped in the form of the preform to be shaped into the hollow molded body and the cooling by ventilating the internal space of the object to be shaped are simultaneously performed throughout the entire process of the blowing operation.

2. A stretch blow molding method comprising producing, from an object to be shaped being in a form of a preform, an object to be shaped in a form of a hollow molded body by a stretch blow molding apparatus, the stretch blow molding apparatus including: a blow mold in which an object to be shaped, which is in a form of a preform that can be shaped at a high temperature, can be disposed and which has a hollow molded body shape-forming surface on an inner surface thereof; and a stretching apparatus configured to cause a rod to enter the object to be shaped, which is disposed in the blow mold and is in the form of the preform, inward, and a blowing apparatus configured to blow compressed air inward of the object to be shaped being in the form of the preform, wherein the stretch blow molding apparatus performs: a stretching operation of stretching the object to be shaped being in the form of the preform in a rod axial direction by causing the rod to enter the object; and a blowing operation including shaping by which the object to be shaped that is stretched by the rod is inflated to shape the object to be shaped into the hollow molded body and cooling by ventilating an internal space of the object to be shaped the blowing apparatus includes: a compressed air supply source configured to send out compressed air adjusted to have an air pressure at which the object to be shaped being in the form of the preform is inflated to be shaped into the hollow molded body; an inflow passage through which the compressed air from the compressed air supply source flows to an internal space of the object to be shaped disposed in the blow mold; and a non-closed outflow passage through which the compressed air flows out from the internal space of the object to be shaped to a discharging space outside the blow mold in an entire process of the blowing operation by the blowing apparatus, a compressed air flow passage is formed through which the compressed air from the compressed air supply source flows through the inflow passage and the internal space of the object to be shaped and through the outflow passage into the discharging space; and the shaping of blowing the compressed air adjusted to have an air pressure, at which the object to be shaped in the form of the preform is inflated to be shaped into the hollow molded body, to inflate the object to be shaped in the form of the preform to be shaped into the hollow molded body and the cooling by ventilating the internal space of the object to be shaped are simultaneously performed throughout the entire process of the blowing operation.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0069] FIG. 1 is an explanatory diagram showing an injection stretch blow molding machine.

[0070] FIG. 2 is an explanatory diagram schematically showing the arrangement of an injection molding section, a stretch blow molding section, and a takeout section.

[0071] FIG. 3 is an explanatory diagram showing an example of a conventional stretch blow molding apparatus.

[0072] FIG. 4 is an explanatory diagram schematically showing a main part of a conventional stretch blow molding apparatus of a non-air-discharging type during blowing.

[0073] FIG. 5 is an explanatory diagram schematically showing the flow of compressed air during low-pressure blowing by the conventional stretch blow molding apparatus of a non-air-discharging type during blowing.

[0074] FIG. 6 is an explanatory diagram schematically showing the flow of compressed air during high-pressure blowing by the conventional stretch blow molding apparatus of a non-air-discharging type during blowing.

[0075] FIG. 7 is an explanatory diagram schematically showing a main part of a conventional stretch blow molding apparatus of an air-discharging type outside a core mold during cooling.

[0076] FIG. 8 is an explanatory diagram schematically showing the flow of compressed air in a shaping stage of the conventional stretch blow molding apparatus of an air-discharging type outside a core mold during cooling.

[0077] FIG. 9 is an explanatory diagram schematically showing the flow of compressed air in a cooling stage of the conventional stretch blow molding apparatus of an air-discharging type outside a core mold during cooling.

[0078] FIG. 10 is an explanatory diagram schematically showing an example of a stretch blow molding apparatus according to the present invention when viewed from the front side of the stretch blow molding section.

[0079] FIG. 11 is an explanatory diagram schematically showing a main part of the stretch blow molding apparatus according to the present invention.

[0080] FIG. 12 is an explanatory diagram schematically showing the flow of compressed air in a stretch blow molding method according to the present invention.

[0081] FIG. 13 is an explanatory diagram schematically showing another exemplary flow of compressed air in the stretch blow molding method according to the present invention.

DESCRIPTION OF EMBODIMENTS

[0082] The present invention will next be described in detail on the basis of an embodiment illustrated in FIGS. 10 to 13. Note that the portions having the same configurations as those of the conventional example illustrated in FIGS. 1 to 9 will be denoted by the same reference numerals, and descriptions thereof will be omitted. A stretch blow molding apparatus 11 of the present invention is an apparatus configured in the stretch blow molding section 4 of an injection stretch blow molding machine 1 as described above, and includes a blow mold 8, a stretching apparatus 9, and a blowing apparatus 10.

[0083] Then, the stretch blow molding apparatus 11 is configured such that the stretching apparatus 9 performs a stretching operation. In the stretching operation, the blow core 15 is fitted into a lip mold 6 positioned corresponding to the blow mold 8, and a rod 12 is moved downward (downward in the rod axial direction) so as to pass through an in-core passage 14 of the blow core 15, and enter an object to be shaped e (in the form of a preform that can be shaped at a high temperature), which is disposed inside the blow mold 8 while being supported by the lip mold 6, inward, so that the object to be shaped e is stretched in the rod axial direction. See FIGS. 10 and 11.

[0084] Further, the stretch blow molding apparatus 11 is configured such that the blowing apparatus 10 performs a blowing operation. Here, the blowing operation includes shaping by which the object to be shaped which is to be stretched by the rod 12 in the above-described stretching operation is inflated to be shaped into a hollow molded body, and cooling by ventilating an internal space of the object to be shaped (cooling by evacuating blown compressed air). Unlike the conventional example described above, the present invention is provided with the stretch blow molding apparatus 11 to perform shaping and cooling simultaneously.

Blowing Apparatus:

[0085] The blowing apparatus 10 of the stretch blow molding apparatus 11 of the present invention includes a compressed air supply source 32 configured to take out compressed air from an air tank 19, an inflow passage 33, and an outflow passage 34.

Compressed Air Supply Source:

[0086] The above-described compressed air supply source 32 sends out compressed air adjusted to have an air pressure at which an object to be shaped e in the form of a preform that can be shaped at a high temperature is inflated to be shaped into the form of a hollow molded body d. The compressed air supply source 32 may be any source as long as it sends out the compressed air a that inflates the object to be shaped e into the object to be shaped e in the form of the hollow molded body d. Therefore, as the compression machine 18, it is possible to use a compression machine such as a compressor having the capability of supplying compressed air taken out by the first compressed air supply source 21 in the conventional example into the air tank. The air pressure of the compressed air a sent out from the compressed air supply source 32 is 1 MPa.

Inflow Passage:

[0087] The above-described inflow passage 33 is a flow passage through which the above-described compressed air a flows from the compressed air supply source 32 to the internal space c of the object to be shaped e in the blow mold 8. Specifically, an air supply pipe (not shown) having one end connected to the compressed air supply source 32 is connected to a portion of the blow core mounting body 16 which communicates with the above-described in-core passage 14, so that the compressed air a adjusted to have an air pressure of 1 MPa from the compressed air supply source 32 is allowed to pass through the air supply pipe and the in-core passage 14. The inflow passage 33 is a flow passage through which the compressed air a can be blown into the object to be shaped e when the lower end of the blow core 15 fits into the lip mold 6 and the rod 12 of the stretching apparatus 9 enters the inside of the object to be shaped e to allow for blow molding.

[0088] As illustrated in FIG. 10, the portion of the air supply pipe for introducing the compressed air a into the in-core passage 14 is branched so as to correspond to the blow core, and each of the air supply pipes is constituted by a flexible tube 37 so as to be able to respond to the ascending and descending movement.

[0089] In the above-described inflow passage 33, a solenoid valve 23 is disposed in the middle of the flow passage in a portion serving as the air supply pipe as illustrated in FIG. 12, so that the inflow passage 33 is opened when the blowing apparatus 10 performs the blowing operation.

Outflow Passage:

[0090] The above-described outflow passage 34 is a flow passage which serves as a non-closed flow passage through which the compressed air a flows out from the internal space c of the object to be shaped e to the discharging space outside the blow mold. Specifically, an air supply pipe (not shown) is connected to a portion of the rod mounting body 13 which communicates with the above-described in-rod passage 17, so that the above-described compressed air a adjusted to have an air pressure of 1 MPa from the internal space c of the object to be shaped e is allowed to flow out (be discharged) toward the discharge space outside the blow mold. The outflow passage 34 is a flow passage for discharging the compressed air a throughout the entire blowing process when the lower end of the blowing core 15 fits into the lip mold 6 and the rod 12 of the stretching apparatus 9 enters the inside of the object to be shaped e to allow for blow molding.

[0091] The portion of the air supply pipe connected to the in-rod passage 17 is also constituted by a flexible tube 37 so that the air supply pipe can respond to the ascending and descending movement.

[0092] As illustrated in FIG. 12, a throttle valve 35 is disposed in the above-described outflow passage 34 at a portion serving as the air supply pipe, and a silencer 25 is disposed at the end portion thereof. Thus, the outflow passage 34 is a flow passage that is always open regardless of whether the blowing apparatus 10 is blowing or stopping.

Compressed Air Flow Passage:

[0093] In the blowing apparatus 10 with such a configuration, the compressed air flow passage 36 is formed in which the compressed air a from the compressed air supply source 32 flows through the inflow passage 33 and the internal space c of the object to be shaped e (the object to be shaped from the state in which the object is in the form of a preform to the state in which the object is in the form of a hollow molded body) and through the outflow passage 34 to the discharging space in the entire process of the blowing operation.

[0094] In the compressed air flow passage 36 as illustrated in FIG. 12, compressed air adjusted to have an air pressure of 1 MPa at which the object to be shaped e is inflated to be shaped into the form of a hollow molded body is caused to pass throughout the entire process of the blowing operation. At the same time, the compressed air a is caused to be discharged from the outflow passage 34 downstream in the supplying direction of the compressed air a. Therefore, the compressed air flow passage 36 is provided so that the stretch blow molding apparatus 11 is configured to blow the compressed air a into the object to be shaped e, so that shaping of inflating the object to be shaped e into the shape of the hollow molded body and cooling by ventilating the internal space c of the object to be shaped e are simultaneously achieved throughout the entire process of the blowing operation.

[0095] By disposing the throttle valve 35 in the outflow passage 34 as described above, it is ensured that a pressure is generated for molding the object to be shaped in the form of a preform that can be shaped at a high temperature into the object to be shaped in the form of a hollow molded body.

[0096] In the inflow passage 33 of the above-described example illustrated in FIGS. 11 and 12, the compressed air supply source 32 is configured as a portion from which the compressed air regulated in pressure by the pressure reducing valve 20 can be taken out. As a matter of course, in the case where a desired air pressure can be taken out from the air tank 19, the compressed air supply source 32 may be a portion configured to take out the compressed air a directly from the air tank 19 as illustrated in FIG. 13.

[0097] As the means for supplying the compressed air a having the air pressure of 1 MPa from the compressed air supply source 32 and for reliably obtaining a pressure for performing shaping to obtain the form of the hollow molded body while ventilating the internal space of the object to be shaped e under the condition that the outflow passage 34 is opened, it is not limited to the use of the throttle valve 35.

[0098] In addition, in order to inflate the object to be shaped e in the form of the preform b into the object to be shaped e in the form of the hollow molded body d, the air pressure of the compressed air a taken out from the compressed air supply source 32 is 1 MPa in the above-described example. However, the air pressure of the compressed air is not limited to 1 MPa as long as the object to be shaped in the form of the hollow molded body can be obtained by inflating the object to be shaped in the form of the preform b. For example, the compressed air sent out from the compressed air supply source 32 may have an air pressure selected from the range of 0.1 MPa to 3.5 MPa.

Comparison of Molded Articles:

[0099] A hollow molded body was manufactured by incorporating a conventional stretch blow molding apparatus into an injection stretch blow molding machine. Further, a hollow molded body was manufactured by incorporating the stretch blow molding apparatus as an example into an injection stretch blow molding machine, and implementing the above-described invention. The manufactured hollow molded bodies by both machines were compared with each other.

[0100] The blowing operation of each of the conventional stretch blow molding apparatus and the stretch blow molding apparatus implementing the present invention was as follows. The hollow molded body was a milk bottle made of PET (for a content of 250 mL).

Conventional Stretch Blow Molding Apparatus for Comparison:

[0101] As the blowing operation, shaping (in a non-air-discharging state) was performed in 1.9 seconds by supplying compressed air having the air pressure of 1 MPa, and then, cooling by ventilation (air-discharging) was performed in 2.3 seconds by supplying compressed air having the air pressure of 3 MPa. The molding cycle with the injection stretch blow molding machine was 9.94 seconds.

Exemplary Stretch Blow Molding Apparatus for Comparison:

[0102] As the blowing operation, compressed air having the air pressure of 1 MPa was supplied such that air was constantly discharged from the end portion of the above-described compressed air flow passage (from the silencer portion), and the above-described shaping and the above-described cooling were simultaneously performed in 4.2 seconds, thereby obtaining a hollow molded body. The molding cycle with the injection stretch blow molding machine was 9.96 seconds.

[0103] Comparison of the hollow molded body manufactured by incorporating the above-described conventional stretch blow molding apparatus with the hollow molded body manufactured by incorporating the stretch blow molding apparatus of the example and implementing the above-described invention showed that both hollow molded bodies had the same molding dimensions and that both hollow molded bodies were molded well.

Comparison Regarding Flow Rate of Compressed Air:

[0104] When the flow rate of air by blowing the compressed air having the air pressure of 3 MPa performed by the blow molding is compared with the flow rate of air by blowing the compressed air having the air pressure of 1 MPa,

[0105] the maximum flow rate for blowing the compressed air having the air pressure of 3 MPa was about 10,000 L/min,

[0106] the maximum flow rate for blowing the compressed air having the air pressure of 1 MPa was about 2,000 L/min, and

[0107] the maximum flow rate at the air pressure of 1 MPa was about ⅕ of the maximum flow rate at the air pressure of 3 MPa.

[0108] The minimum flow rate for blowing the compressed air having the air pressure of 3 MPa was about 4,000 L/min,

[0109] the minimum flow rate for blowing the compressed air having the air pressure of 1 MPa was about 1,000 L/min, and

[0110] the minimum flow rate at the air pressure of 1 MPa was about ¼ of the minimum flow rate at the air pressure of 3 MPa.

[0111] Comparison of the maximum flow rate at the air pressure of 3 MPa with the minimum flow rate at the air pressure of 1 MPa showed that the minimum flow rate at the air pressure of 1 MPa was about 1/10 of the maximum flow rate at the air pressure of 3 MPa. Since the flow rate in the case of the air pressure of 1 MPa is overwhelmingly small as described above, it is understood that the amount of air used is smaller in the case where the hollow molded body is molded by implementing the present invention when a case of incorporating the conventional stretch blow molding apparatus into the injection stretch blow molding machine to manufacture the hollow molded body and a case of incorporating the stretch blow molding apparatus as the example and implementing the above-mentioned invention to manufacture the hollow molded body are compared with each other.

Clamping Unit in Stretch Blow Molding Apparatus:

[0112] In the example of the present embodiment in which the compressed air having the air pressure of 1 MPa is blown to simultaneously perform the shaping and the cooling, the compressed air flows out from the compressed air flow passage into the discharging space even when the preform is transformed into the shape of the hollow molded body. The pressure by which the blow mold is caused to be opened at this time is smaller than the pressure by which the blow mold is caused to be opened at the time of shaping by a conventional non-air-discharging method.

[0113] In particular, in the conventional example, the compressed air having the air pressure of 1 MPa is blown when shaping is performed without discharging air, and the pressure for blowing that causes the blow mold to open at this time is low. However, in the case of the present example, even if compressed air having the same air pressure is blown, the pressure that causes the blow mold to open is further small. Therefore, as the mold clamping unit in the stretch blow molding apparatus, one adopting a smaller mold clamping force can be employed.

[0114] Further, in the case of a blow mold having a bottom mold, not only can the above-described mold clamping force be reduced, but a pressure circuit of applying a smaller pressure can be adopted for the pressure of pushing up the bottom mold. In addition, the force given against the pressure that pushes the blow core upward during the blowing process can be reduced. As described, it can be understood that the mold clamping force, the bottom mold pushing-up force, and the blow core pushing-down force can be reduced in this manner.

[0115] Further, since the mold clamping force, the bottom mold pushing-up force, the blow core pushing-down force, and the like applied to the blow mold can be reduced, the mold strength of the blow mold can also be reduced.

[0116] In addition, it can be understood that a control electric circuit for opening and closing the first inflow passage and the second inflow passage in the above-described conventional apparatus is not necessary, and thus the number of elements that may be damaged can be reduced. Further, in the present embodiment, the configuration is simplified, and the number of parts of the valves for controlling the flow of the compressed air can be greatly reduced.

REFERENCE SIGNS LIST

[0117] 1 . . . Injection stretch blow molding machine [0118] 4 . . . Stretch blow molding section [0119] 6 . . . Lip mold [0120] 8 . . . Blow mold [0121] 9 . . . Stretching apparatus [0122] 10 . . . Blowing apparatus [0123] 11 . . . Stretch blow molding apparatus [0124] 12 . . . Rod [0125] 14 . . . In-core passage [0126] 15 . . . Blow core [0127] 17 . . . In-rod passage [0128] 32 . . . Compressed air supply source [0129] 33 . . . Inflow passage [0130] 34 . . . Outflow passage [0131] 35 . . . Throttle valve [0132] 36 . . . Compressed air passage [0133] a . . . Compressed air [0134] b . . . Preform [0135] c . . . Internal space [0136] d . . . Hollow molded body [0137] e . . . Object to be shaped