Injection blow molding mold and method

Abstract

An injection blow molding die includes: a punch (1) having a blow port (3) connected to a first conduit (5) and an exhaust port (4) connected to a second conduit (7); the first conduit (5) being in communication with a first pressurized gas supply source (6) configured to supply pressurized gas through the blow port (3) at an overpressure (OP) higher than a blow molding pressure (BP) suitable for blowing a preform (30a) into a container (30b); the exhaust port (4) being in communication with a pressure limiting device set at the blow molding pressure (BP); a blow molding cavity (2) configured to receive the punch (1) therein on which a hot and soft preform (30a) is disposed; and a cooling device connected to the blow molding cavity (2). Gas inside the container (30b) exceeding the blow molding pressure (BP) is allowed to escape through the exhaust port (4), thereby generating a cooling airflow from the blow port (3) to the exhaust port (4).

Description

Technical Field

[0001] This invention relates to an injection blow molding die and method. More specifically, this invention relates to a plastic preform for injection molding and a die and method for blow molding the preform into a container. The injection blow molding die and method are suitable for container forming machines. Background Technology

[0002] A known container forming machine includes: a preform forming unit for forming a preform by injecting molten plastic material into a preform mold; and a container forming unit for forming a container by blowing the preform in a blow mold.

[0003] In such known container molding machines, the preform mold includes a preform molding cavity that mates with a punch. This preform molding cavity has an inner surface defining an outer surface of the preform, and the punch has an outer surface defining the inner surface of the preform. An injection blow molding mold includes a blow molding cavity having an inner surface defining an outer surface of the container obtained by blow molding the preform, the blow molding cavity accommodating a punch carrying a hot, soft preform.

[0004] An injection blow molding mold includes a blow molding device and a cooling device. When a punch carrying a preform is located inside the blow molding cavity, the blow molding device delivers pressurized gas through one or more air ports located in the punch to the hot and soft preform to expand the preform until the expanded preform adheres tightly to the inner surface of the blow molding cavity to form a container. The cooling device is connected to the blow molding cavity and cools the outer surface of the container that is in contact with the inner surface of the blow molding cavity.

[0005] Different types of transfer devices are known for transferring punches carrying hot and soft preforms from the preform molding cavity to the blow molding cavity.

[0006] Document WO2017093578A1 discloses an injection blow molding die comprising one or more rows of molding cavities arranged on a substrate. Each row of molding cavities includes an integer n injection cavity and n+1 blow molding cavities. The injection and blow molding cavities alternate and are aligned with each other, with the blow molding cavities located at both ends of the row. One or more rows of punches are arranged on a movable plate, each row including 2n aligned punches. The movable plate is driven to perform alternating movements, transferring the punches from the injection cavity to the blow mold cavity and vice versa.

[0007] The mold described in document WO2017093578A1 also includes multiple injection nozzles and a blow molding device: the injection nozzles inject molten plastic material into the injection mold cavity to mold a preform on a punch located in the injection mold cavity; the blow molding device supplies compressed gas through air vents located on the punch to the interior of the preform arranged in the blow molding cavity, causing the preform to expand into a container. The injection mold cavity and the blow molding cavity are formed in separate injection blocks and blow blocks. The blow blocks are cooled by cooling fluid circulating through cooling conduits arranged inside the blow blocks to cool the outer surface of the container that is in contact with the inner surface of the blow molding cavity.

[0008] In any case, once the container is formed, it must reach a temperature lower than that required for the blow mold to achieve sufficient consistency, so that it can be removed from the injection blow mold without deformation. This temperature reduction takes time, reducing the productivity of the container forming machine.

[0009] For example, when using an injection blow mold with a cooling device consisting of cooling fluid circulating through cooling conduits in the blow mold cavity, the cooling device only cools the outer surface of the container that is in contact with the inner surface of the blow mold cavity, and does not cool the inner surface of the container. Therefore, a longer cooling time is required for the container to be removed from the injection blow mold without deformation.

[0010] DE2605967A1 relates to a blow molded part internally cooled by circulating mist supplied and extracted through internal channels in a blow molding mandrel, and discloses an injection blow mold comprising the combination of features included in the preamble of claim 1 of this patent application.

[0011] US3944141 also disclosed a similar mold, although it used a pressure bag instead.

[0012] However, there is a need for an injection blow molding die equipped with means for cooling the outer and inner surfaces of the container once it has expanded in the blow molding cavity, in order to reduce the necessary cooling time before the finished container can be removed from the injection blow molding die. Summary of the Invention

[0013] According to a first aspect, the present invention satisfies the above-mentioned needs by providing an injection blow molding die. The injection blow molding die includes a punch, an injection cavity, and a blow molding cavity. The outer surface of the punch defines an inner surface of a preform made of plastic; the interior of the injection cavity accommodates the punch, and its inner surface defines the outer surface of the preform; the blow molding cavity has an inner surface defining the outer surface of a container obtained by blow molding the preform.

[0014] The injection mold cavity can accommodate a punch. When the punch is inside the injection mold cavity, the injection device injects molten plastic material into the injection mold cavity through one or more injection nozzles, thereby forming a preform.

[0015] The blow molding cavity can accommodate a punch carrying a hot, soft preform. The blow molding apparatus is configured such that, when the punch carrying the preform is located inside the blow molding cavity, pressurized gas is delivered into the hot, soft preform through one or more air ports located in the punch. The preform thus expands and is blow-molded into the shape of a container defined by the inner surface of the blow molding cavity.

[0016] Optionally, a conveying device is used to convey the punch from the injection mold cavity to the blow mold cavity and vice versa.

[0017] In order to cool the outer surface of the molded container that is in contact with the inner surface of the blow molding cavity, the injection blow molding die is provided with a cooling device for cooling the inner surface of the blow molding cavity.

[0018] One or more air inlets are connected to a first conduit in communication with a first pressurized gas supply source. The first pressurized gas supply source is configured to provide pressurized gas through one or more air inlets at an overpressure above the blow molding pressure, which is a pressure suitable or sufficient to inflate a preform into the shape of a container by blow molding.

[0019] The blow molding apparatus also includes one or more vents located in the punch, spaced apart from the one or more blow ports, and connected to a second conduit that communicates with a pressure limiting device set at the blow molding pressure. When the gas inside the container exceeds the blow molding pressure, the pressure limiting device allows the gas to escape through the one or more vents.

[0020] Therefore, when the preform fully expands into the container, the gas inside the container exceeds the blow molding pressure and generates an airflow from one or more of the blow nozzles to one or more of the exhaust nozzles, which cools the inner surface of the container. This increases the cooling effect of the cooling device on the outer surface of the container, helping to shorten the cooling time required for the finished container to be removed from the blow molding cavity without deformation, thereby improving productivity.

[0021] When using the injection blow molding die of the present invention, the improvement achieved by simultaneously cooling the inner and outer sides of the container wall helps to create a robust surface layer on both sides of the plastic wall of the container, thereby providing a stable structure for the container and preventing subsequent deformation.

[0022] According to a first variant of the blow molding apparatus, the pressure limiting device includes a pressure limiting valve located in a second conduit and configured to allow pressurized gas to escape from the interior of the container through one or more vents when the pressure inside the container is higher than the blow molding pressure.

[0023] For example, all the above-mentioned features disclosed in the referenced DE2605967A and shown in Figures 1 to 3B are prior art.

[0024] According to a second variation of the blow molding apparatus that forms the core of the present invention, the pressure limiting device includes a second pressurized gas supply source in communication with a second conduit. The second pressurized gas supply source is configured to supply pressurized gas through one or more vents when the internal pressure of the preform is lower than or equal to the blow molding pressure, and to recover pressurized gas flowing out of the container through one or more vents when the internal pressure of the preform is higher than the blow molding pressure.

[0025] In a third variation of the blow molding apparatus, the pressure limiting device further includes a second pressurized gas supply source and a pressure limiting valve. The second pressurized gas supply source is connected to a second conduit and configured to supply pressurized gas at the blow molding pressure through one or more vents. The pressure limiting valve, located in the second conduit, is configured to allow pressurized gas to flow from the second pressurized gas supply source into the interior of the preform through one or more vents when the pressure inside the container is lower than or equal to the blow molding pressure, and to allow pressurized gas to escape from the interior of the container through the vents when the pressure inside the container is higher than the blow molding pressure.

[0026] The injection blow molding die also includes an opening device and a closing device configured to open and close one or more air inlets and one or more vents when the punch carrying the preform is located inside the blow molding cavity.

[0027] For this purpose, the punch includes a base and a forming body. The forming body can move relative to the base in an axial direction coaxial with the longitudinal axis of the punch between an open position and a closed position: in the open position, a gap is formed between the base and the forming body, which provides a proximal gas passage; in the closed position, there is no gap or gas passage between the base and the forming body.

[0028] The punch also includes a valve body that is movable relative to the forming body in an axial direction between an open position and a closed position: in the open position, a gap is formed between the forming body and the valve body, which provides a distal gas passage; in the closed position, there is no gap or gas passage between the forming body and the valve body.

[0029] In a first embodiment, a proximal gas passage is connected to a second conduit such that the proximal gas passage forms one or more exhaust ports, and a distal gas passage is connected to a first conduit such that the distal gas passage forms one or more air inlets. A coupling actuator moves the molding body between an open position and a closed position to open and close one or more exhaust ports. An elastic element is configured to bias the valve body to the closed position and to allow the valve body to move to the open position under overpressure in the first conduit to open and close one or more air inlets.

[0030] In this first embodiment, one or more air inlets provided by the distal gas channel are preferably formed as a single hole around the longitudinal axis of the punch and optionally located in the distal region of the punch, which defines an area for forming a preform for the bottom of the container. One or more exhaust outlets provided by the proximal gas channel are preferably formed as a single opening around the longitudinal axis of the punch and optionally located in the proximal region of the punch, which defines an area for forming a preform for the shoulder of the container.

[0031] In the second embodiment, a proximal gas passage is connected to a first conduit, such that the proximal gas passage forms one or more air inlets, and a distal gas passage is connected to a second conduit, such that the distal gas passage forms one or more exhaust outlets. A first actuator is connected to move the molded body between an open position and a closed position to open and close one or more air inlets, and a second actuator is connected to move the valve body between an open position and a closed position to open and close one or more exhaust outlets.

[0032] In this second embodiment, one or more air inlets provided by the proximal gas channel are preferably formed as a single opening around the longitudinal axis of the punch and optionally located in the proximal region of the punch, which defines a region for forming a preform for the shoulder of the container. One or more exhaust outlets provided by the distal gas channel are preferably formed as a single opening around the longitudinal axis of the punch and optionally located in the distal region of the punch, which defines a region for forming a preform for the bottom of the container.

[0033] In the specification, the term "proximal end" is used to refer to the position of the substrate near the punch, and the term "distal end" is used to refer to the position of the substrate away from the punch.

[0034] Any of the first, second, and third variations of the blow molding apparatus can be combined with any of the first and second embodiments of the injection blow molding die without departing from the scope of the invention.

[0035] According to a second aspect, the present invention provides an injection blow molding method comprising the following conventional steps:

[0036] First, the method includes receiving a punch in an injection mold cavity, the punch defining an inner surface of a preform, while the injection mold cavity defines an outer surface of the preform.

[0037] The method then includes injecting molten plastic material into the injection mold cavity through at least one injection nozzle in the injection device to form a preform while the punch is located within the injection mold cavity.

[0038] In a subsequent step, the method includes receiving a punch carrying a preform in a hot and soft state inside a blow molding cavity, the blow molding cavity defining the outer surface of the container to be obtained.

[0039] The method then includes delivering pressurized gas into the interior of the preform through one or more air ports located in the punch while the punch carrying the preform is inside the blow molding cavity, to inflate the preform into the container by blowing or blow molding the preform. As a final routine step, the method includes cooling the outer surface of the container in contact with the blow molding cavity by a cooling device associated with the blow molding cavity before removing the container from the mold.

[0040] As an additional distinguishing step, the injection blow molding method of the present invention further includes supplying pressurized gas through one or more blow ports at an overpressure above the blow molding pressure via a first pressurized gas supply source connected to a first conduit connected to one or more blow ports. This blow molding pressure is suitable or sufficient to expand a hot and soft preform into a container by blow molding. Then, when the pressure inside the container exceeds the blow molding pressure, the pressurized gas escapes from the interior of the container through one or more vents located in the punch spaced apart from the one or more blow ports and connected to a second conduit connected to a pressure limiting device set at the blow molding pressure.

[0041] Therefore, when the preform fully expands into the shape of the container, the gas inside the container exceeds the blow molding pressure and generates an airflow from one or more blow ports to one or more exhaust ports, which cools the inner surface of the container. Attached Figure Description

[0042] The foregoing features and advantages will be more fully understood from the following detailed description of several illustrative, non-limiting embodiments, with reference to the accompanying drawings, in which:

[0043] Figure 1 is a cross-sectional view of the punch, injection cavity, and blow molding cavity of an injection blow mold in the open position, referencing prior art (see DE2605967A).

[0044] Figure 2 is a cross-sectional view of the punch and blow molding cavity in Figure 1 in the closed position.

[0045] Figures 3A and 3B are schematic diagrams showing the interaction of the punch and blow molding cavity of Figures 1 and 2 with the blow molding device in two different operating stages.

[0046] Figure 4A and 4B This is a schematic diagram of the punch and blow molding cavity in Figures 1 and 2 cooperating with the blow molding device in two different operating stages, according to the principle of the present invention.

[0047] Figure 5A and5B This is a schematic diagram of the punch and blow molding cavity of Figures 1 and 2 engaging with a third variant of the blow molding apparatus of an additional embodiment that forms part of the present invention at two different operational stages.

[0048] Figure 6 This is a cross-sectional view of the punch and blow molding cavity of the injection blow molding die in the closed position in the second embodiment. Detailed Implementation

[0049] The following description is merely exemplary in nature and is not intended to limit this disclosure, application, or use.

[0050] Referring first to Figures 1 and 2, reference numerals 1, 22, and 2 respectively denote the punch, injection cavity, and blow molding cavity of the injection blow molding die according to the first embodiment of the present invention. In Figures 1 and 2, some components of the blow molding apparatus are omitted, as they will be shown in Figures 3A, 3B, 4A, and 4B; and Figure 5A , 5B A detailed explanation will be provided later.

[0051] The punch 1 has a longitudinal axis A, and the injection mold cavity 22 and the blow mold cavity 2 each have their own longitudinal axis, for example, parallel to the longitudinal axis A of the punch 1. A transfer device (not shown) is configured to transfer the punch from the interior of the injection mold cavity 22 to the interior of the blow mold cavity 2 and vice versa.

[0052] The punch 1 has an outer surface that defines the inner surface of the preform 30a, while the injection cavity 22 formed by the injection molding block 23 defines the outer surface of the preform 30a. As is the case in conventional art, the injection cavity 22 is configured to receive the punch 1 in a closed position (not shown), and the injection molding block 23 has an injection nozzle 24 through which an injection device injects molten plastic material into the injection cavity 22 to form the preform 30a by injection molding.

[0053] As shown in Figures 1 and 2, when the punch 1 and the blow molding cavity 2 are aligned, the punch 1 can move between the open position (Figure 1) and the closed position (Figure 2). In the open position, the punch 1 and the blow molding cavity 2 are separated from each other; in the closed position, the punch 1 is in the closed state and coupled to the blow molding cavity 2, together forming an injection blow mold.

[0054] The blow molding cavity 2 has an inner surface that defines the outer surface of the container 30b, which is obtained by blow molding or blow molding a preform 30a. When the punch 1 is received in the blow molding cavity 2 to form a blow mold, the punch 1 carries a preform 30a in a hot and soft state.

[0055] In the illustrated embodiment, the preform 30a has a neck 31 formed in conjunction with two neck half molds 17a, 17b, which move together with the punch 1 and are connected to the blow molding cavity 2 in the mold closed position.

[0056] The punch 1 includes a base 10, a forming body 11, and a valve body 13. The forming body 11 is movable relative to the base 10 in an axial direction coaxial with the longitudinal axis A of the punch 1 between a closed position (FIG. 1) and an open position (FIG. 2). In the closed position, there is no gap between the base 10 and the forming body 11; in the open position, a gap is formed between the base 10 and the forming body 11 to provide a proximal gas passage 12. The valve body 13 is axially movable relative to the forming body 11 between the closed position (FIG. 1) and the open position (FIG. 2). In the closed position, there is no gap between the forming body 11 and the valve body 13; in the open position, a gap is formed between the forming body 11 and the valve body 13 to provide a distal gas passage 14.

[0057] A proximal gas channel 12 is formed around the longitudinal axis A of the punch 1 and is located in the proximal region of the punch 1, which defines the area of ​​the preform 30a for forming the shoulder of the container 30b. A distal gas channel 14 is formed around the longitudinal axis A of the punch 1 and is located in the distal region of the punch 1, which defines the area of ​​the preform 30a for forming the bottom of the container 30b. In the first embodiment shown in Figures 1 and 2, the distal gas channel 14 constitutes an air inlet 3 connected to the first conduit 5, and the proximal gas channel 12 constitutes an exhaust port 4 connected to the second conduit 7.

[0058] In a first embodiment of the prior art, a connecting actuator 15 (shown in Figures 1 and 2) moves the molded body 11 between an open position and a closed position, and an elastic element 20 is configured to bias the valve body 13 to the closed position. For example, the elastic element 20 is a helical spring, which is configured to allow the valve body 13 to move to the open position under the action of a specific pressure in the first conduit 5.

[0059] The blow molding apparatus described above is configured to deliver pressurized gas through the air inlet 3 into the interior of a hot and soft preform 30a, causing the preform 30a to expand to the inner surface of the blow molding cavity 2, thereby forming a container 21. Furthermore, the blow molding apparatus allows gas inside the expanded container 30b to escape through the exhaust port 4 under specific conditions (explained below).

[0060] Therefore, as shown by the thick arrow in Figure 2, once the container 30b is formed and before it is removed from the blow mold, an airflow is generated inside the container 30b from the air inlet 3 near the bottom of the container 30b to the exhaust outlet 4 near the top of the container 30b. This airflow cools the inner surface of the container 30b. For this reason, the air inlet 3 and the exhaust outlet 4 located on the punch 1 should be positioned as far apart from each other as possible.

[0061] A blow molding cavity 2 is formed in a blow molding block 18, and a cooling conduit 19 is arranged inside the blow molding block 18. Through the cooling conduit 19, a cooling device is configured to circulate cooling fluid to cool the inner surface of the blow molding cavity 2 and the outer surface of the container 30b that is in contact with the cooling device. Therefore, before the container 30b is removed from the blow molding mold, both the inner and outer surfaces of the container 30b are cooled, which shortens the cycle time and improves productivity. Now, with reference to the elements of the first embodiment and with reference to FIG3A, 3B, 4A, 4B, 5A, and 5B, a first variant (according to the prior art), a second variant, and a third variant of the blow molding apparatus and their operation will be explained.

[0062] The common feature of the first, second and third variations of the blow molding apparatus is that the first conduit 5 connected to the blow port 3 is connected to the first pressurized gas supply source 6, which is configured to supply pressurized gas through the blow port 3 at an overpressure OP (e.g. 12 bar) higher than the blow molding pressure BP (e.g. 9 bar), wherein the blow molding pressure BP is the pressure suitable for fully inflating the preform 30a until it adheres tightly to the inner surface of the blow molding cavity 2 and obtains the shape of the container 30b.

[0063] However, in the first, second, and third variations of the blow molding apparatus, the second conduit 7 connected to the exhaust port 4 is connected to a pressure limiting device set at the blow molding pressure BP. The pressure limiting device is different in each variation; when the gas in the container 30b exceeds the blow molding pressure BP, the pressure limiting device allows the gas in the container 30b to escape through the exhaust port 4.

[0064] As shown in Figures 3A and 3B, in the first variant of the blow molding device, the pressure limiting device only includes a pressure limiting valve 9 set at the blow molding pressure (see Figures 3A and 3B), which is connected to a second conduit 7 connected to the exhaust pipe 4.

[0065] As shown in Figure 3A, when the blow molding operation is performed using the second variant of the blow molding device, the pressurized gas from the first pressurized gas supply source 6 is supplied to the interior of the preform 30a through the blow port 3 under overpressure OP, so that the preform 30a begins to expand and the pressure inside the preform 30a increases from below the blow molding pressure BP to the blow molding pressure BP, while the pressure relief valve 9 remains closed.

[0066] Then, as shown in Figure 3B, when the preform 30a has fully expanded and abutted against the inner surface of the blow molding cavity 2 to form the container 30b, the first pressurized gas supply source 6 continues to supply pressurized gas at overpressure OP through the air inlet 3. The internal pressure of the container 30b rises to a level exceeding the blow molding pressure BP, which causes the pressure relief valve 9 to open, thereby allowing the gas inside the container 30b to escape through the exhaust port 4, thereby generating a cooling airflow from the air inlet 3 to the exhaust port 4 inside the container 30b.

[0067] like Figure 4A and 4B As shown, in the second variant blow molding apparatus of the first embodiment of the present invention, the pressure limiting device includes a second pressurized gas supply source 8 connected to a second conduit 7 and a pressure limiting valve 9. The pressure limiting valve 9 is located in the second conduit 7 between the exhaust port 4 and the second pressurized gas supply source 8, and the second conduit 7 is connected to the exhaust port 4. The second pressurized gas supply source 8 is configured to supply pressurized gas at the blow molding pressure BP through the exhaust port 4. The pressure limiting valve 9 is configured to allow pressurized gas at the blow molding pressure BP to flow from the second pressurized gas supply source 8 through the exhaust port 4 into the interior of the preform 30a when the pressure inside the preform 30a is lower than or equal to the blow molding pressure BP, and to allow pressurized gas to escape from the interior of the container 30b through the exhaust port 4 when the pressure inside the container 30b is higher than the blow molding pressure BP.

[0068] like Figure 4A As shown, when the blow molding operation is performed using the second modified blow molding device according to the principle of the present invention, pressurized gas from the first pressurized gas source 6 at overpressure OP is first supplied to the interior of the preform 30a through the blow air 3. At the same time, pressurized gas from the second pressurized gas source 8 at the blow molding pressure is supplied to the interior of the preform 30a through the pressure relief valve 9 and the exhaust port 4, thereby the preform 30a begins to expand, and the pressure inside the preform 30a increases from the pressure below the blow molding pressure to the blow molding pressure.

[0069] Then, as Figure 4B As shown, when the preform 30a has fully expanded and abutted against the inner surface of the blow molding cavity 2 to form the container 30b, the first pressurized gas supply source 6 continues to supply overpressured gas through the blow opening 3. This causes the pressure inside the container 30b to exceed the blow molding pressure BP, resulting in the gas inside the container 30b escaping through the exhaust port 4 and the pressure relief valve 9. This allows the closed gas passage to return to the second pressurized gas supply source 8 and allows the gas to escape from the pressure relief valve 9, thereby generating a cooling airflow from the blow opening 3 to the exhaust port 4 inside the container 30b.

[0070] like Figure 5A and 5B As shown, in the third variant blow molding apparatus according to the present invention, the pressure limiting device connected to the second conduit 7 connected to the exhaust port 4 includes a second pressurized gas supply source 8, which is configured to supply pressurized gas through the exhaust port 4 at the blow molding pressure BP, and to recover the pressurized gas flowing out of the container 30b through the exhaust port 4 when the pressure inside the container 30b is higher than the blow molding pressure BP.

[0071] like Figure 5AAs shown, when the blow molding operation is performed using the third modified blow molding device, the pressurized gas from the first pressurized gas source 6 is supplied to the interior of the preform 30a through the blow port 3 under overpressure OP. At the same time, the pressurized gas from the second pressurized gas source 8 is supplied to the interior of the preform 30a through the exhaust port 4 under the blow molding pressure BP. As a result, the preform 30a begins to expand, and the pressure inside it increases from below the blow molding pressure BP to the blow molding pressure BP.

[0072] Then, as Figure 5B As shown, when the preform 30a has fully expanded and abutted against the inner surface of the blow molding cavity 2 to form the container 30b, the first pressurized gas supply source 6 continues to supply pressurized gas with overpressure OP through the blow molding opening 3. This causes the pressure inside the container 30b to exceed the blow molding pressure BP, and causes the gas inside the container 30b to escape through the exhaust port 4 and return to the second pressurized gas source 8, thereby generating a cooling airflow from the blow port 3 to the exhaust port 4 inside the container 30b.

[0073] The blow molding apparatus of any of the first, second or third variations may include other valve elements and / or accessories (not shown) commonly used in pneumatic circuits, without changing the operation of the blow molding apparatus as described above.

[0074] When using the first variant shown in Figures 3A and 3B or Figure 4A and 4B In the second variant of the blowing device shown, the output of compressed gas generated by pressure exceeding the blow molding pressure BP through the exhaust port 4 and the pressure relief valve 9 can be advantageously directed to a suitably sized tank (not shown) or a network pressurized gas line (not shown), so that the pressurized gas close to the blow molding pressure BP can be used for other purposes, such as driving pneumatic pistons or other auxiliary components or devices of the same injection blow molding die or other machines.

[0075] Therefore, by using the discharged pressurized gas to drive other pneumatic mechanisms, the increased consumption of pressurized gas due to the generation of cooling airflow inside container 30b is reduced.

[0076] as Figure 4A The second variant shown in 4b or Figure 5A and 5B The principle of the invention is achieved in the same way as the third variant of the blow molding apparatus shown, except that a second pressurized gas supply source 8 is used in addition to the first pressurized gas supply source 6, so that the blow molding pressure BP inside the container 30b is reached more quickly, thereby helping to reduce cycle time and increase system productivity.

[0077] When using, such as Figure 5A and 5BWhen using the third variant of the blow molding apparatus shown, it must be considered that the pressurized gas exiting from the exhaust port 4 and returning to the second pressurized gas supply source 8 is relatively hot after cooling the inner surface of the container 30b. Preferably, the pressurized gas must be cooled before being supplied to the interior of the container 30b again in a subsequent blow molding cycle.

[0078] When any of the blow molding devices in the second or third variant is applied to the first embodiment shown in Figures 1 and 2, under the action of overpressure OP of the first conduit 5 provided by the first pressurized gas supply source 6, the elastic element 20 is configured to allow the valve body 13 to move to the open position.

[0079] Figure 6 The injection blow molding die of a second embodiment of the present invention is shown. Its main difference from the first embodiment described above with reference to FIG1 and 2 is that the proximal gas channel 12 is connected to the first conduit 5, thereby forming the blow-in port 3, and the distal gas channel 14 is connected to the second conduit 7, thereby forming the exhaust port 4. The second embodiment also differs from the first embodiment in that, instead of the elastic element, a second actuator 16 (such as...) is connected... Figure 6 (As shown) the movable valve body 13 is moved between the open and closed positions.

[0080] The air inlets 3 are all formed around the longitudinal axis A of the punch 1 and are located in the proximal region of the punch 1, which defines the area for forming the preform 30a of the shoulder of the container 30b; the exhaust outlets 4 are all formed around the longitudinal axis A of the punch 1 and are located in the distal region of the punch 1, which defines the area for forming the preform 30a of the bottom of the container 30b. Therefore, in the second embodiment, the cooling airflow generated within the container 30b (such as...) Figure 6 (As indicated by the arrow) flows in the opposite direction to the first embodiment and has the same result.

[0081] As shown in Figures 3A, 3B, 4A, 4B and Figure 5A , 5B Either of the second and third variant blow molding apparatuses shown is suitable for use as follows: Figure 6 The second embodiment shown

[0082] As shown in Figures 1, 2, and 6, in the first and second embodiments of the injection blow molding die, the blow molding cavity 2 has a cylindrical inner surface for forming the cylindrical body portion of the container 30b, while two neck halves 17a, 17b are used to form the neck and shoulder portions of the container 30b. This allows the die to open and the container 30b to be removed axially from the blow molding cavity 2. However, alternatively, a pair of radially open half-blow molding cavities can be provided to form containers with more complex body shapes, without departing from the scope of the invention.

[0083] The present invention also provides an injection blow molding method, which can be implemented by any of the second and third variant blow molding devices in the first and second embodiments of the injection blow molding die, the method comprising the steps known in the art:

[0084] First, the injection mold cavity 22 defining the outer surface of the preform 30a receives the punch 1 defining the inner surface of the preform 30a. Then, when the punch 1 is located in the injection mold cavity 22, molten plastic material is injected into the injection mold cavity 22 through at least one injection nozzle 24 in the injection device to form a preform 30a.

[0085] Subsequently, a punch 1 is received in the blow molding cavity 2, on which a preform 30a is distributed in a hot and soft state. The blow molding cavity 2 defines the outer surface of the container 30b obtained by blow molding the preform 30a.

[0086] Then, when the punch 1 carrying the preform 30a is located inside the blow molding cavity 2, pressurized gas under overpressure OP is delivered to the interior of the preform 30a through at least one air inlet 3 located in the punch 1. The pressurized gas under overpressure OP is supplied by a first pressurized gas supply source 6. The pressure of overpressure OP is higher than the blow molding pressure BP that is suitable or sufficient to expand the preform 30a into the container 30b by blow molding.

[0087] Finally, when the pressure inside container 30b is higher than the blow molding pressure BP, the pressurized gas escapes from the inside of container 30b through the exhaust port 4, which is located in the punch 1 and spaced apart from the blow port 3. The exhaust port 4 is connected to the second conduit 7, which is connected to the pressure limiting device set at the blow molding pressure BP.

[0088] Therefore, when the gas inside container 30b exceeds the blow molding pressure BP, an airflow is generated from the blow port 3 to the exhaust port 4, and this airflow cools the inner surface of container 30b, while the outer surface of container 30b in contact with the blow molding cavity 2 is cooled by a cooling device associated with the blow molding cavity 2.

[0089] As a principle of the present invention, the method further includes:

[0090] By means of a second pressurized gas supply source 8 connected to the second conduit 7, pressurized gas is supplied through at least one of the exhaust ports 4 at a blow molding pressure BP. When the pressure inside the container 30b is higher than the blow molding pressure BP, the pressurized gas flowing out of the container 30b is recovered through at least one exhaust port 4.

[0091] The scope of this invention is defined by the appended claims.

Claims

1. An injection blow mold, comprising: A non-expandable punch that defines the inner surface of the preform; A blow molding cavity that defines the outer surface of a container obtained by blow molding injection of a preform, the blow molding cavity being configured to receive a punch therein, wherein one of the preforms is disposed on the punch in a hot and soft state; A blow molding apparatus, the blow molding apparatus being configured to deliver pressurized gas into the interior of the preform through at least one of the air inlets located in the punch when the punch carrying the preform is located inside the blow molding cavity; and At least one of the air inlets is connected to a first conduit, which is in communication with a first pressurized gas supply source. The first pressurized gas supply source is configured to supply pressurized gas through at least one of the air inlets at an overpressure higher than the blow molding pressure. The blow molding pressure is a pressure suitable for blowing the preform into the container. The blow molding device further includes at least one exhaust port, which is located in the punch at a position spaced apart from at least one of the blow ports and is connected to a second conduit. The second conduit is connected to a pressure limiting device set at the blow molding pressure, which allows gas in the container to escape through at least one of the exhaust ports when the blow molding pressure is exceeded. Thus, an airflow is formed inside the container, which comes into direct contact with the inner surface of the container, from at least one air inlet to at least one air outlet, thereby cooling the inner surface of the container; Its features are, The pressure limiting device includes a second pressurized gas supply source connected to the second conduit. The second pressurized gas supply source is configured to supply pressurized gas through at least one of the exhaust ports under blow molding pressure, and to recover the pressurized gas flowing out of the container through at least one of the exhaust ports when the internal pressure of the container is higher than the blow molding pressure.

2. The injection blow mold according to claim 1, characterized in that, The pressure limiting device includes a pressure limiting valve located in the second conduit and configured to allow pressurized gas to escape from the interior of the container through at least one of the exhaust ports when the internal pressure of the container is higher than the blow molding pressure.

3. The injection blow mold according to claim 1, characterized in that, The injection blow molding die also includes a cooling device configured to cool the inner surface of the blow molding cavity and the outer surface of the container in contact with the cooling device.

4. The injection blow mold according to claim 2, characterized in that, The injection blow molding die also includes a cooling device configured to cool the inner surface of the blow molding cavity and the outer surface of the container in contact with the cooling device.

5. The injection blow mold according to claim 1, 2, 3 or 4, characterized in that, The pressure limiting device includes a second pressurized gas supply source and a pressure limiting valve: the second pressurized gas supply source is connected to the second conduit and configured to supply pressurized gas through at least one of the exhaust ports under blow molding pressure; the pressure limiting valve is located in the second conduit and configured to allow pressurized gas to flow from the second pressurized gas supply source into the interior of the preform through at least one of the exhaust ports when the pressure inside the preform is lower than or equal to the blow molding pressure, and to allow pressurized gas to escape from the interior of the container through at least one of the exhaust ports when the pressure inside the container is higher than the blow molding pressure.

6. The injection blow mold according to claim 1, characterized in that, It also includes an opening device and a closing device configured to open and close at least one of the air inlets and at least one of the exhaust outlets when the punch carrying the preform is located inside the blow molding cavity.

7. The injection blow mold according to claim 6, characterized in that, The punch includes a base and a forming body, and the forming body is movable relative to the base in an axial direction coaxial with the longitudinal axis of the punch between an open position and a closed position: in the open position, a gap between the base and the forming body provides a proximal gas passage; in the closed position, there is no gap between the base and the forming body or a gas passage is formed.

8. The injection blow mold according to claim 7, characterized in that, The punch also includes a valve body that is movable relative to the forming body in an axial direction between an open position and a closed position: in the open position, a gap between the forming body and the valve body provides a distal gas passage; in the closed position, there is no gap between the forming body and the valve body or a gas passage is formed.

9. The injection blow mold according to claim 8, characterized in that, The proximal gas passage is connected to the second conduit and forms at least one of the exhaust ports; the distal gas passage is connected to the first conduit and forms at least one of the blowing ports.

10. The injection blow mold according to claim 8, characterized in that, The proximal gas channel is connected to the first conduit and forms at least one of the air inlets; the distal gas channel is connected to the second conduit and forms at least one of the exhaust outlets.

11. The injection blow mold according to claim 9, characterized in that, Also includes: An actuator operatively connected to move the molded body between an open position and a closed position; or an elastic element configured to bias the valve body into a closed position and to allow the valve body to move to an open position under overpressure in the first conduit.

12. The injection blow mold according to claim 10, characterized in that, Also includes: A second actuator, operably connected to move the valve body between an open position and a closed position, or an actuator operably connected to move the molded body between an open position and a closed position.

13. The injection blow mold according to claim 8, characterized in that, The proximal gas channel and the distal gas channel are formed around the longitudinal axis of the punch.

14. The injection blow mold according to any one of claims 1 to 4, characterized in that, At least one of the air inlets is provided by a distal gas channel formed entirely around the longitudinal axis of the punch and located in the distal region of the punch, the distal region of the punch defining the area for forming the preform for the bottom of the container. Furthermore, at least one of the exhaust ports is provided by a proximal gas channel formed entirely around the longitudinal axis of the punch and located in the proximal region of the punch, the proximal region of the punch defining a region for forming the preform at the top of the container, or located in the distal region of the punch defining a region for forming the preform at the bottom of the container.

15. The injection blow mold according to claim 5, characterized in that, At least one of the air inlets is provided by a proximal gas channel formed around the longitudinal axis of the punch and located in the proximal region of the punch, the proximal region of the punch defining the area of ​​the preform for forming the shoulder of the container; At least one of the vents is provided by a distal gas channel formed around the longitudinal axis of the punch and: located in the proximal region of the punch, the proximal region of the punch defining the area of ​​the preform for forming the shoulder of the container; or located in the distal region of the punch, the distal region of the punch defining the area of ​​the preform for forming the bottom of the container.

16. An injection blow molding method, comprising: A non-expandable punch is received within a blow molding cavity, wherein the blow-molded preform is arranged on the punch in a hot and soft state, and the blow molding cavity defines the outer surface of a container obtained by the blow-molded preform. When the punch carrying the preform is located in the blow molding cavity, pressurized gas is delivered into the interior of the preform through at least one of the air inlets located in the punch; By means of a first pressurized gas supply source connected to a first conduit, pressurized gas is supplied at an overpressure higher than the blow molding pressure through at least one of the blow nozzles, the blow molding pressure being suitable for blowing the preform into the container; and When the pressure inside the container is higher than the blow molding pressure, pressurized gas is allowed to escape from the inside of the container through at least one of the exhaust ports by connecting at least one of the exhaust ports to a second conduit that is connected to a pressure limiting device set at the blow molding pressure. The exhaust port is located in the punch and at a position spaced apart from at least one of the blow ports. When the gas inside the container exceeds the blow molding pressure, an airflow is formed between at least one blow port and at least one exhaust port located at opposite ends of the punch. This airflow comes into direct contact with the inner surface of the container, thereby cooling the inner surface of the container. The method is characterized by further comprising: By means of a second pressurized gas supply source connected to a second conduit, pressurized gas is supplied at blow molding pressure through at least one of the exhaust ports. When the pressure inside the container is higher than the blow molding pressure, the pressurized gas flowing out of the container is recovered through at least one of the exhaust ports.

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