CN1231340C - Method and apparatus for cooling preform after molding - Google Patents

Abstract

The present invention relates to a method and apparatus for injection molding and cooling molded articles, such as preforms, to prevent crystallization. The apparatus and method utilize a removable plate for removing a molded article (48) from a mold, the plate including heat exchange means for cooling the outer surface of the molded article or preform (48) and a system (74) for controlling the inner surface of the molded article or preform (48).

Description

Method and apparatus for cooling preform after molding

The present invention relates to a method and apparatus for the molding and cooling of plastic molded articles, such as preforms made of one or more materials, such as plastic resins. The present invention particularly relates to a rapid injection molding method in which the molded article, such as a PET preform, is ejected from the mold before the cooling step is completed. The present invention employs a new post-mold cooling method and apparatus for internally cooling the preform by means of convective heat transfer after it is removed from the mold and placed outside the mold. The invention also relates to external cooling by means of conductive or convective heat exchange, which can be performed at least partially simultaneously with internal cooling.

Proper cooling of the molded article represents a very important aspect of the injection molding process, since it affects the quality of the molded article and the length of the overall injection cycle. This is even more important where semi-crystalline resins are used, such as injection molding of PET preforms. After injection, the PET resin remains in the cavity gap, cooling for a time long enough to prevent the formation of crystallized parts and solidify the preform before it is ejected.

In order to reduce the cycle time of the injection process, if a preform is ejected from a mold quickly, two things usually happen. The first thing is that the preform is not being cooled evenly. In most cases, crystallization occurs at the bottom opposite the model nozzle. The heat accumulated in the wall of the preform during injection is still high enough to cause post-molding crystallization in the preform, especially in the region of the nozzle of the preform. The nozzle area is a very important area because the cooling of the mold in this part is not sufficient and the resin in the cavity gap is still in contact with the hot stem of the hot cast injection nozzle. state. If this region of a preform remains crystalline above a certain size and depth, this will reduce the quality of a blown article. The second thing is that the preform will be too soft, so deformation may occur during the subsequent handling steps. Another important area of a preform is the neck finish portion, which in many cases has thicker walls and retains more heat than other portions. The root portion requires effective post-mold cooling to prevent it from crystallizing. In addition, efficient cooling allows the neck to solidify sufficiently to withstand further handling.

In the past, various attempts have been made to improve the cooling effect of PET injection molding systems, but have not been able to significantly improve the quality of molded preforms or shorten the cycle time. U.S. Patent No. 4,382,905 by Valyi (hereby incorporated by reference) discloses a method of injection molding in which the molded preform is transferred to a first tempering mold for a first cooling step and then transferred to a Temper the model a second time for the final cooling step. These two tempering molds are similar to injection molds and have internal means for cooling the walls of the mold which are in contact with the preform during cooling. US 4,382,905 by Valyi does not provide cooling means on the means for transferring the preforms from the molding area or provide additional cooling means enabling a fluid coolant to circulate in the molded preforms.

U.S. Patent 4,592,719 by Bellehache discloses an injection molding method for producing PET preforms, wherein the molded preform is removed from the injection core by a first movable device, said first movable device Including vacuum suction for securing said preform, the method further includes air suction (convective) cooling of the outer surface of the preform. A second cooling device used in US 4,592,719 by Bellehache in combination with a second movable device also utilizes air absorption to further cool the interior of the preform. See Figure 22 here. U.S. Patent No. 4,592,719 by Bellehache does not disclose that blowing cold air into the interior of a preform has a better cooling effect than drawing or absorbing outside air, and does not disclose the use of Cooling means for cooling by conduction heat exchange and in close contact with the walls of the preform, and air blowing means towards the dome portion of said preform. This technical solution proposed by Bellehache has many disadvantages, including low cooling efficiency, poor cooling uniformity, long cooling time, and high possibility of deformation of the preform.

US patents US 5,176,871 and US 5,232,715 disclose a preform cooling method and device. The molded preform is held by an injection molding core outside the molding area. The mold core is cooled with a coolant that does not come into contact with the molded preform. A cooling tube larger than the preform is placed around the preform to blow cool air around the preform. The main problem with the apparatus and methods disclosed in these patents is that the preform is clamped in the mandrel and this increases the cycle time considerably. In addition, direct contact between the coolant and the preform is not utilized for internal cooling purposes.

US Patents US 5,114,327, US 5,232,641, US 5,338,172 and US 5,514,309 (herein incorporated by reference) propose a preform internal cooling method using a liquid coolant. The preforms ejected from a mold are transferred to a preform carrier having vacuum means to position the preforms without contacting the outer walls of the preforms. However, this preform carrier does not have any cooling means. A cooling core is also introduced into the interior of the preform held by the carrier and a cooling fluid is blown into the interior of the preform to cool the preform. The coolant is also evacuated from the chamber surrounding the preform by the same vacuum device used to hold the preform. These patents do not disclose that cold air is blown into the interior of a preform where the air is free to leave the preform after cooling the preform. These patents also do not disclose the simultaneous cooling of the preforms from the inside and the outside or a preform carrier with cooling means. See Figure 21 here.

Japanese Patent Laid-Open No. 7-171888 (herein incorporated by reference) discloses a preform cooling apparatus and method. A molded preform automated carrier is used to transfer the preforms to a cooling station. The automatic device is capable of externally cooling the preform wall by means of conduction heat exchange using a cooling water. The cooling table includes a first movable automatic transfer device, the first movable automatic transfer device has a rotating manipulator part, and the rotating manipulator part includes components for fixing the preform and can also conduct heat exchange to Vacuum device for external cooling of preform walls. The molded preforms are transferred from the automated carrier to the robotic section. The manipulator section moves from position A to position B where it turns through a 90 degree angle to transfer the preforms (currently only cooled externally) to a cooling tool. The cooling tool has means for fixing the preform, means for cooling the inside of the preform by blowing air, and means for cooling the outside of the preform by blowing air or water cooling. Here, the internal cooling employed is shown in FIGS. 19 and 20 . This patent does not disclose a method of internal and external cooling immediately upon ejection of the preform from the mold and into a carrier plate. There is also no disclosure of simultaneously cooling the interior and exterior of the preform while the preform is held by the movable robotic carrier. Therefore, this cooling method is not fast enough and does not prevent crystallization outside the model.

Figures 19 and 20 show a known method of cooling a preform from the inside, where a cooling device is located on the outside of the preform and is used to blow cold air into the inside of the preform. Since the air nozzles are located on the outside of the preform, the incoming cold air flow must at least partially affect and mix with the outgoing warm air. This will greatly reduce cooling efficiency. If the cooling device is on the same axis as the preform, then the method shown in Figure 19 is ineffective because there is no air circulation through the preform. If the cooling device were moved laterally as shown in Figure 20, it would be possible to achieve air circulation, but this would still be ineffective because one side of the preform is cooler than the other. Works well and cools down faster. The coolant has a quasi-diffusive flow and an asymmetric profile. This profile is very ineffective and does not allow the cooling fluid/gas to converge towards the nozzle section or dome section.

A main object of the present invention is to provide a method and an apparatus for producing preforms which enable improved cooling efficiency.

Another object of the present invention is to provide a method and a device for producing preforms of good quality.

Another object of the present invention is to provide a method and a device for producing preforms which can shorten the overall production cycle time.

The above objects are achieved by the device and method of the present invention.

In one embodiment, the novel molding and cooling method to which the present invention relates includes removing the preform from the mold before the preform in the mold has sufficiently cooled, i.e. A certain amount of heat to crystallize the root portion or the entire preform; securing the preform outside the molding zone; and cooling the preform from the inside by means of convective heat transfer so that no crystallization occurs in any of the aforementioned zones.

In another embodiment of the invention, the novel molding and cooling method to which the invention relates includes removing the preform from the mold before the preform in the mold has cooled sufficiently, i.e. the preform remains A certain amount of heat to crystallize the nozzle part, the neck root part or the whole preform; fix the preform outside the molding area; In the absence of crystallization, the cooling step includes placing a coolant in direct contact with the preform; and externally cooling the preform by means of convective heat transfer so that crystallization does not occur in any of the aforementioned regions. Said external cooling step may be performed simultaneously, at least partially simultaneously or sequentially, with respect to said internal cooling step.

In another embodiment of the invention, the novel molding and cooling method to which the invention relates includes removing the preform from the mold before the preform in the mold has cooled sufficiently, i.e. the preform remains A certain amount of heat to crystallize the nozzle part, the neck root part or the whole preform; fix the preform outside the molding area; In the absence of crystallization, the cooling step includes disposing a coolant in direct contact with the preform; and externally cooling the preform by conduction heat exchange so that crystallization does not occur in any of the aforementioned regions. Said external cooling step may be performed simultaneously, at least partially simultaneously or sequentially, with respect to said internal cooling step.

In each of the embodiments described above, the preforms are ejected from the mold and secured outside the mold by means independent of the mold, such as a movable and removable plate. Such individual fixtures may hold a group of said molded preforms or several groups of preforms simultaneously. When several groups of preforms are held by said independent means, the temperatures of these groups of preforms are different from each other because they are molded at different times. According to the invention, the molded preforms can be cooled from the inside and from the outside in different sequences by means of the cooling method according to the invention. In each of the embodiments described above, the internal cooling is performed by means, such as cooling pins, capable of at least partially entering the interior of said preform and enabling circulation of a coolant inside the preform. Cooling is preferably performed in such a way that the quasi-symmetrical flow of coolant delivered to the interior of the preform is directed towards those parts of the preform that require more cooling than other parts, such as the nozzle and neck sections. In a preferred embodiment of the invention, coolant is directed towards the bottom or dome portion of said preform to form a circulation of coolant.

In some embodiments of the invention, the new internal cooling of the preform can be supplemented with external cooling which can be performed in several ways. For example, external cooling can be done on a removable plate (one or more locations) with a cooling device that can utilize heat transfer by conduction (cooling water) or convection (air/gas) Work. It is also possible to perform external cooling on a removable plate (one or more locations) without cooling means, so that the preforms are only partially in contact with their holding means. In this way, a separate cooling device can be used to deliver cooling air/gas so that the cooling air/gas is in direct contact with the outer surface of the preform.

In another embodiment, the preform is fixed in a removable plate without any cooling means and the preform is only internally cooled by means of the novel cooling pins to which the invention relates.

The novel cooling method to which the present invention relates can be achieved in one embodiment by taking the preform or molded article out of the mold and fixing said preform or molded article in a removable In a panel having a system for cooling the outer surface of the preform or molding, cooling means are then engaged inside the preform or molding to cool both the outer and inner surfaces. According to the invention, an additional cooling step is introduced in order to reduce the temperature of the preform by means of convective heat exchange, for example by means of a cooling gas circulated inside the preform.

As mentioned above, the method and apparatus according to the present invention facilitate the prevention of crystallization in the most critical areas in the preform, namely the bottom or dome portion where the nozzle portion is located and the neck. In addition, the cooling method and apparatus according to the present invention can be incorporated into an injection-blow molding equipment, in which the cooled preforms without crystallization can be further temperature-regulated and processed Blown into bottles.

According to one aspect of the present invention, a method of preventing crystallization in an injection molded preform utilizing improved off-mold cooling comprises injecting a molten material into a mold formed from two mold halves or plates, The two mold halves or plates are separated from each other at a mold open position to define a molding area; the molten material is allowed to cool to a temperature very close to the crystallization-glass transition temperature of the molten material so that the molded article can be mechanically moved out of the mold without undergoing geometric deformation; maintaining a distance between the molds sufficient to allow a molded article carrier to move between said two mold halves; ejecting said molded articles from said mold and transferring them to said movable carrier; cooling of the molded article while in the movable carrier to reduce crystallization by conduction heat transfer, where the coolant used is a blown air; and internal cooling by convective heat transfer The molded articles were cooled until each molded article was substantially free of any crystallized portion. This method can also be supplemented by a mobile vehicle with convective heat exchange for external cooling.

According to one aspect of the present invention, the apparatus for forming crystallization-free injection molded articles comprises a mold having two mold halves movable between a mold closed position and a mold open position; means for injecting molten material into said mold when said mold half is in said mold closed position; for cooling said molten material in a cavity gap formed by said mold half to a very Means at a temperature close to the crystallization-glass transition temperature of such molten material so that the molded article can be mechanically moved out of the mold without undergoing geometric deformation; means for opening the mold so that maintaining a distance between said mold halves sufficient to allow a molded article carrier to move between said mold halves; means for ejecting said molded article from said mold; means for transferring molded articles to said movable carrier; said carrier having means for securing said molded articles and cooling said molded articles by conduction heat transfer to reduce crystallization; and also capable of utilizing convection Heat exchange means for cooling the molded articles from the inside until each molded article (preferably the whole molded article) is substantially free of any crystallized parts (especially in the nozzle part of the mold). This method can also be supplemented by a mobile vehicle with convective heat exchange for external cooling.

As used herein, the terms "removable plate", "removable plate" and "end-of-arm tool" are interchangeable and represent the same structure.

Further details, as well as other objects and advantages of the method and apparatus to which the invention relates, can be derived from the following detailed description with reference to the accompanying drawings, in which like elements are indicated by like reference numerals.

Figure 1 shows the temperature of the preform versus time during the injection process and after the injection is complete;

Figure 2 schematically shows a preform in a model;

Figures 3(a) and 3(b) show the temperature gradient across a molded preform wall during cooling;

Figure 3c shows the temperature distribution along the preform wall;

Fig. 4 is a sectional view representing a kind of injection mold involved in the prior art;

Figure 5 is a cross-sectional view showing a movable robot including an "end-of-arm tool" (EOAT) device placed between a fixed template and a movable template In the molding area between;

Figures 6(a) and 6(b) are side views showing an embodiment of the invention comprising an automated and removable plate (or end-of-arm tool, EOAT) and a fixed cooling pin frame;

Fig. 6 (c) and Fig. 6 (d) are the front views of the embodiment shown in Fig. 6 (a) and Fig. 6 (b);

Figure 7(a)-Figure 7(d) shows the frame and cooling pins involved in the first embodiment of the present invention;

Fig. 8 (a)-Fig. 8 (g) have shown the design forms of several cooling pins involved in the present invention;

Figure 9(a) and Figure 9(b) show the cooling pins involved in two embodiments of the present invention in more detail;

Figure 10(a) shows a preform having crystalline regions as produced in prior art methods;

Figure 10(b) shows a preform without crystallized regions produced after utilizing the method of the present invention;

Figure 11(a)-Figure 11(1) shows another embodiment of the frame and cooling pins involved in the present invention;

Figure 12 is a cross-sectional view of a system in which air cooling channels are incorporated into the mold half;

Fig. 13 (a) and Fig. 13 (b) are the side views of another embodiment of cooling system of the present invention;

Figure 14 is a top view of an injection molding system having another embodiment of the cooling system of the present invention;

15 is a cross-sectional view of another embodiment of the cooling system of the present invention, showing the mechanism connected to the removable plate for cooling the interior of the molded article;

Figure 16 shows an embodiment of the invention in which a removable plate without cooling means is used to remove the molded preform from the molding area;

Fig. 17 shows another structural form of the cooling pin involved in the present invention;

Fig. 18 (a) and Fig. 18 (b) have shown another structural form of the cooling pin involved in the present invention;

Figures 19 and 20 illustrate prior art methods for cooling the interior of a preform;

Figure 21 shows another method for cooling the inside and outside of a preform involved in the prior art;

Figure 22 shows a prior art system for cooling a preform by drawing in ambient air; and

Figure 23 shows a frame structure with cooling pins on various faces of the frame.

Referring now to the drawings, Figure 1 is a graph showing the temperature of the preform versus time during injection and after injection is complete. Figure 2 schematically shows a preform in a model. As can be seen from this figure, cooling within the mold is generally accomplished by means of cooling tubes 12 and 14 located within the cavity 16 and core portion 18, respectively. In this way, cooling is performed from both sides of the preform 11 . Additionally, as shown in FIG. 2 , the cavity plate 16 generally has a nozzle region 20 formed at the bottom or dome portion 22 of the preform 11 . The preform has a neck root portion 13 which sometimes has thicker walls which are difficult to cool to such an extent that crystallization is prevented.

Figures 3(a) and 3(b) show the temperature gradient across a molded preform wall during cooling. Figure 3(a) shows the temperature gradient inside the model, while Figure 3(b) shows the temperature gradient outside the model. Figure 3c shows the temperature distribution along the preform wall. The temperature peak indicates the temperature in the dome portion or nozzle portion of the preform.

Referring now to Fig. 4, there is provided an injection mold comprising a fixed mold half or template 32 having an array of cavities 34 and a movable mold half or template 36. The movable mold half or plate 36 has an array of cores 38 . The cavity plate 32 is in communication with a manifold plate (not shown) capable of receiving molten material from an injection assembly (not shown) of an injection molding apparatus. The cavity 34 receives molten material through a cavity nozzle 40 from a hot runner nozzle (not shown), such as a valve nozzle nozzle (not shown). When the plates 32 and 36 are in a mold closed position, the cavity is surrounded by cooling means 42 for cooling molten material in the cavity gap formed by the core 38 and cavity 34 . Said cooling means 42 are preferably formed by cooling channels embedded in the formwork 32 for conducting a cooling fluid. As mentioned above, the mold core 38 and the mold cavity 34 form a plurality of mold cavity gaps (not shown) at the closed position of the mold, and during the injection step, molten material is filled into the mold through the mold nozzle 40. in the cavity space. The core 38 also includes means 44 for cooling the molten material in the cavity gap. The cooling means 44 preferably comprise a cooling tube in each core. The core plate 36 also includes an ejector plate 46 for removing the molded preform 48 from the core 38 . The operation of the ejector plate 46 is well known in the art and is not covered by the present invention. Indeed, the ejector plate 46 may comprise any suitable ejector plate 46 known in the art.

According to the present invention, any molten plastic, metal or ceramic material can be injected into the cavity gap and cooled into a desired article using the molding system shown in FIG. 4 . In a preferred embodiment of the invention, said molten material is PET and the molded article is a preform. According to the invention, however, the molding can also be a preform made of more than one material, eg virgin PET, recycled PET and a suitable barrier material (eg EVOH).

It is known in the art that a method of molding a preform comprises the steps of closing the mold, injecting molten material into the cavity gap, starting to cool the cavity gap, filling the cavity gap with the molten material, and The molten material is held under pressure, subjected to final in-mold cooling, the mold is opened, the solidified article or preform is ejected from the core and transferred to a removable plate. According to the invention, in order to shorten the cycle time, the residence time of the preforms in the mold must be minimized so that the mold can produce groups of preforms as fast as possible. The problem with shortening the residence time in the mold is that the cooling time must be shortened and the degree of solidification of the molding or preform sufficient to withstand all subsequent handling steps without deformation. Shortening the cooling time is a problematic option, since a sufficient and uniform cooling of the moldings or preforms cannot be achieved with the cooling devices 42 and 44 . When the molded article or preform is cooled in the mold for a short period of time immediately after opening the mold, the heat retained in the molded article or preform is very large and depends on the thickness. Such internal heat may form a crystallized portion at the nozzle portion or the dome portion of the molded article or preform, at the neck root portion of the molded article or preform, or in the entire preform. In order to prevent crystallization of the molding or preform, an effective cooling method must be employed. During the cooling process, the shrinkage of the molded product must be controlled as much as possible, which may adversely affect the final dimensions of the molded product.

Figure 5 shows an embodiment of an automatic and removable plate 60 that may be used in the cooling method of the present invention. The removed plate 60 includes a plurality of hollow fixtures or containers 62 which may be water cooled tubes. Conventional removable plates that can be used as the removed plate 60 are shown in U.S. Pat. The literature is hereby incorporated by reference. In operation, the openings of the plurality of fixtures 62 are centered with the core 38 of the formwork 36 . Operation of the ejector plate 46 transfers the moldings 48 into the fixture 62 . According to the invention, said removable plate 60 can be provided with a plurality of fixing means 62, the number of fixing means 62 can be the same as the number of mold cores 38 or a multiple of the number of mold cores, for example three times the number of mold cores or quadruple. Where there are more fixtures 62 than cores 38, some of the molded articles can be held for a period longer than one molding cycle, thereby enabling increased cooling time while maintaining a high molded article throughput. The method according to the invention can be carried out regardless of the number of moldings held by said holding device 62 . However, in the preferred embodiment of the invention, the automatic and removable plate 60 has three times as many fixing devices 62 as the number of cores 38 . This means that the automatic and removable plate 60 does not always carry the same number of preforms or moldings as the fixtures 62 . This also means that a group of preforms can be returned to the mold core more than once as it is cooled by the intimate contact between the hollow tubes 64 in the removable plate and the outer walls of the preforms. The other sets of moldings are picked up in the molding area between the plate and the cavity plate, said pipe 64 carrying a cooling liquid such as water, which is shown in detail in the aforementioned US Pat. No. 5,447,426. The heat exchange between the tube 64 and the hot molded product discharged from the mold is conducted by conduction. In particular, any solid material that can be made into a lubricating cooling device and brought into close contact with the outer wall of the molded product to cool the molded product may be used. Since a cooling system that works in a conduction heat exchange mode cools the molded product or preform through close contact between the molded product or preform and the cooling device, it can Maintains the shape of the molded article or preform in the event of deformation or abrasion.

The conduction cooling means 64 used in the removable plate may be replaced by a convective heat exchange means if desired. Any suitable convective heat exchange device known in the art can be used in conjunction with the removable plate 60 to cool the outer surface of the molded article or preform carried by the removable plate 60 .

Referring now to Figures 6(a) and 6(b), an additional cooling device 70 is used in conjunction with the automatic and removable plate 60 to cool the interior of the molded article or preform by utilizing convective heat transfer. The surface and exterior surfaces are cooled simultaneously, enabling improved post-mold cooling, shorter cycle times, and improved preform quality. Said additional cooling means 70 comprise an array of elongated cooling pins 74 whose function is to deliver a cooling fluid to the interior of the molding held by said removable plate 60 . In a preferred embodiment of the invention, the cooling fluid is mainly directed towards the dome portion (nozzle portion) 22 of the molded article or preform and is delivered directly therein, since the cooling time in the mold is shortened Instead, the dome portion (nozzle portion) 22 is most likely to be crystallized. The cooling fluid is introduced in a circular flow. According to the invention, the cooling fluid may be any suitable coolant, such as a liquid or a gas. In a preferred embodiment of the invention, the cooling fluid is compressed air delivered through a channel 90 located in the cooling pin 74 . This aspect of the invention is shown in more detail in Figure 9(a).

Figure 9(a) shows a cooling pin 74 in accordance with the present invention, which is located within a preform or molded article 48 to be cooled. In order to allow the coolant to flow in an optimal manner, the cooling pins 74 are introduced deeply into the preform 48 to enable the coolant to reach the dome portion or nozzle portion 22 . In addition, the cooling pin 74 can also be used as an additional cooling core. The cooling pins 74 also facilitate the formation of a circulating flow with a cooling effect superior to other flow modes. Utilizing this new cooling pin 74 also allows the incoming blown cool air and outgoing warm air to be completely separated, preventing them from mixing.

As shown in Figure 9(a), the cooling pin 74 is centrally located within the preform or molded article, preferably with the central axis 220 of the cooling pin 74 aligned with the central axis 222 of the preform. It can be seen from this figure that the outer wall 224 of the cooling pin 74 is at a distance D from the inner wall 226 of the preform in an upper region UP. In addition, a distance d is maintained between the outlet nozzle 92 of the cooling pin 74 and the inner wall 228 of the dome portion 22 . In order to achieve the desired circulation pattern of the cooling fluid, it is preferred that the ratio between d and D is in the range of 1:1 to 10:1. More preferably, the outlet nozzle 92 of the cooling pin is a divergent nozzle structure. The outlet nozzle 92 may also be a straight wall nozzle, although it is preferred to use a diverging nozzle for the outlet 92.

Since the cooling pins 74 penetrate deeply into the preform and also act as a cooling core, the free flow of warm air from the preform is also a form of circulation.

Although a preferred configuration of the cooling pin is shown in FIG. 9(a), as shown in FIGS. 8(a)-8(g), FIG. 17 and FIG. and shapes to achieve various cooling effects. For example, as shown in FIG. 8( a ), the lower portion LP of the cooling pin 74 may have a different diameter D2 than the diameter D1 of the upper portion UP of the cooling pin. As shown in Figures 8(a) to 8(c), the upper portion UP of the cooling pin may have different shapes. Referring to Figure 8(d), the cooling pin 74 may have lateral outlets 82 for discharging a cooling fluid onto the side walls of the molded article where crystallization may occur. As shown in FIG. 8( e ), the cooling pin 74 may have a helical groove 84 to achieve a specific cooling effect. Similar in Figures 8(f) and (g), the cooling pin 74 may have a plurality of ribs 86 or a plurality of contact elements 88 around its perimeter.

Figures 18a and 18b show a cooling pin 74 having a plurality of radial conduits 230 to deliver coolant to areas of the preform other than the domed portion 22, such as the neck root portion or main body). The radial ducts 230 may be spaced along the length of the cooling pins to direct coolant to specific regions of a preform 48 .

Cooling pins 74 may be made of any suitable thermally conductive or insulating material. If desired, as shown in FIG. 17, cooling pins 74 may be made of a porous material 232 to diffuse additional coolant into a preform in a very uniform manner except for the dome portion or nozzle portion. 22 other areas.

In a preferred embodiment of the present invention, the cooling pin 74 is designed so that maximum cooling is concentrated at the nozzle portion or dome portion 22 of the molded article 48 so that the cooling fluid is effectively converged so that this area is cool down. In this way, a molded article (such as a preform) having no crystallized region in the nozzle portion or the dome portion 22 can be formed.

Another pin configuration with a cold air blowing system that can be used in the device of the present invention is shown in Figure 19(b). As shown in this figure, the pin 74 has a cool air blowing channel 90 with a cool air blowing channel 90 for directing the cool air to the inner surface of the molding 48 (preferably the domed top of the molding). points or nozzle part 22) of the outlet 92. The channel 90 communicates through an inlet 94 to a source of cool air (not shown). The cooling pin 74 is also provided with a vacuum channel 96 for evacuating cooling air from the interior of the molding 48 . The vacuum channel 86 can be connected to any desired vacuum source (not shown). As can be seen in Figure 19(b), the cooling pin 74 is mounted on a portion of a frame 98 using sliding pads 100 for automatic adjustment of the pin and a fastening device such as a nut 102 . The nut 102 may be secured to an element 104 (not shown) having an externally threaded portion.

Referring now to Figures 6 and 7, cooling pin array 74 is mounted on a cooling frame 98, which may be made of a lightweight material such as aluminum. According to the invention, the cooling frame 98 can be operated in a vertical position or a horizontal position. In both cases, the frame 98 moves towards the removable panel 60 when the molded position of the removable panel 60 reaches its final position. The frame 98 may be moved at high speed using any suitable means known in the art so that the cooling pins 74 are immediately introduced into the molded article. In a preferred embodiment of the invention, hydraulic cylinders 110 are used to move the frame 98 . According to the invention, the number of cooling pins 74 may be the same as or less than the number of containers 62 in said removable plate 60 . According to the invention, said removable plate 60 is provided with means (not shown) for securing said molded article or preform 48 in container 62, such as suction means (not shown), and is also provided with means for ejecting said preforms from said removable plates. The securing means and ejection means may be of the type disclosed in the aforementioned US Pat. No. 5,447,426, which is hereby incorporated by reference. As shown in FIG. 6( c ) and FIG. 6( d ), the cooling frame 98 is provided with a plurality of gaps 112 . Said gap 112 enables the finally cooled moldings or preforms discharged from said removable plate 60 to fall onto a conveyor 114 for sending the resulting products out of the system. In a preferred embodiment of the invention, the cooling pins 74 are moved laterally relative to the receptacle 62 for holding the preforms that must be ejected from the removable plate 60 so that the fully cooled preforms 48 falls onto the conveyor 114. This is the case when the cooling frame is in a horizontal position. When the cooling frame is in a vertical position, it does not interfere with the preforms falling from the removable plates.

Referring now to Figures 7(a) and 7(b), a first column of cooling pins 74 is shown. As can be seen in FIG. 7( b ), each cooling pin 74 has a cooling channel 90 that communicates via channel 122 with a source of cooling air (not shown). A plurality of air valves 124 are provided in the passage 122, and the air valves 124 can be used to adjust the flow of cooling air. In this way, cooling air with a variable flow rate can be supplied to the cooling pin 74 .

Referring now to FIG. 7( c ), each cooling pin 74 can also be provided directly with air from a cooling air source (not shown) via a simple channel 126 . Additionally, as shown in FIG. 7(d), the channel 126 is connected by a flexible conduit 128 to the fluid conduit 120 in each cooling pin, if desired.

According to one embodiment of the invention, said cooling pins 74 enter into the preform secured to said removable plate 60 in very few steps, and in each step, said molded The preforms have different temperatures. In order to optimize the overall cooling step and avoid wastage of coolant, in the first cooling step the preform is very hot so that the cooling pins deliver the maximum amount of cooling air. In the second and subsequent steps, the amount of cooling air directed by the cooling pins engaged with the first molded preform is substantially less than the amount of cooling air directed to the new and hotter molded preform. To further optimize the cooling process, any suitable known temperature sensor, such as a thermocouple, can be used to sense the pre-cooling and post-cooling temperatures of the preform so that cooling can be performed if the molding cycle is interrupted flow regulation. In a preferred embodiment, thermocouples (not shown) are connected to some control means (not shown) located in said removable plate 60 adjacent each preform. By sensing the temperature of each preform, some adjustments can be made to the amount of cooling air delivered to all or some of the cooling pins 74 . This also compensates for cooling inefficiencies or inhomogeneities of the conduction cooling means located in the removable plate.

Referring now to Figures 10(a) and 10(b), Figure 10(a) shows in cross-section a preform 48 molded using a prior art system. It can be seen from this figure that the preform 48 may have crystallized portions in four different regions including the domed portion 22 and the neck 13 . Figure 10(b), on the other hand, shows in cross-section a preform 48 molded using the system of the present invention. As can be seen from this figure, there are no crystallized regions in the preform.

Another embodiment of the invention is shown in Figures 11(a) to 11(1), wherein the removable plate 60' remains in a vertical position throughout the molding cycle. This eliminates a complex motor and makes the plate lighter for faster movement into and out of the cavity gap formed between the mold halves or platens 32 and 36 . The cooling frame 98' used in this system has an additional function and is capable of additional movement. Firstly, the cooling pins 74' cool the moldings or preforms with blowing air and eject the moldings and preforms from the removable plate 60' with suction air. The preforms are held by vacuum on the cooling pins 74' and can be ejected from the tubes 62' in the removable plate 60' during a return process. Said cooling frame 98' can be moved to and back from said removable plate 60', said cooling frame 98' can also be rotated from a vertical position to a conveyor 114' to utilize Stopping the vacuum allows the preform to be ejected from the cooling pins 74'. Any suitable means known in the art may be used to rotate the cooling frame 98' and cooling pins 74' in accordance with the present invention. According to a preferred embodiment of the invention shown in Fig. 11(a) to Fig. 11(1), a fixed cam 130 is used as a very simple means capable of converting translation of the frame into rotation so that the The preforms held by the cooling frame can fall onto a conveyor 114'. As shown in FIG. 11(h), the cooling pins 74' may utilize a vacuum to engage the preform and eject the preform from the removable plate 60'. Next, the preforms are dropped from the cooling pins 74' into a conveyor.

The operation of the new cooling device involved in the present invention can be seen from Fig. 6(a) to Fig. 6(d). After cooling in the mould, the in-mold cooling process is shortened to the point where the moldings or preforms reach a solid state that prevents their deformation, the mold is opened and the removable plate 60 moves into the molding area between core plate 36 and cavity plate 32 . Relative movement between the core plate and cavity plate may be effected in any suitable manner known in the art by any suitable means (not shown) known in the art. After the removable plate reaches the molding position, the cooling pins 74 engage the moldings to cool the moldings, particularly at the domed portion 22 of each molding or preform. .

Although the removable plate 60 described above has water cooling means for conduction cooling of the outer surface of the preform in the fixture 62, in many cases when the preform is first placed in the removable plate when you don't want to start cooling the outer surface. To this end, means for controlling the cooling may be provided in said removable plate so that the external cooling does not start until the internal cooling of the preforms has started and/or has been completed. For example, suitable valves (not shown) are provided in the removable plate to prevent the flow of cooling fluid until a desired moment. In this way, the internal cooling and the external cooling of the preform can be performed simultaneously, at least partially simultaneously or sequentially.

FIG. 16 shows another embodiment of a removable plate 60″ without cooling means for ejecting molded preforms from the molding area. The removable plate 60″ may have A number of preform fixtures 62'' sufficient to accommodate a group of preforms or groups of preforms. The preform is held in place by vacuum means (not shown) which draws on the nozzle or dome portion 22 of the preform 48 through the opening 240 . The preform is also held by a fixture 62", which may have any desired configuration, and which is capable of direct cooling of the preform by means of a cooling device/air. The holding The means 62"is preferably rigid enough to hold the preform and has holes or other openings 242 and 244 in which the holding means cannot make direct contact with the preform. With these fixtures which only partly cover the outer surfaces of the preforms, the preforms can be cooled on their outer surfaces while they are also cooled internally by means of the cooling pins 74 . In this case, the cooling step consists of transferring the preform from the mold to said removable plate 60", which is moved outside the molding area and into a Adjacent cooling area. In the cooling zone, the preform 48 is internally cooled by means of the frame 98 and the cooling pins 74 which penetrate at least partially into the interior of the preform. At the same time, the preform 48 held by the removable plate 60" has an outer surface which is convectively cooled by an additional cooling station 250 which blows a coolant fluid against the preform. Billet Fixture. As shown in FIG. 16, an additional cooling station 250 is shown having a plurality of nozzles 252, 254 and 256 through windows 258 to blow coolant toward the outer surface of the preform. Cooling fluid is blown into the removable plate 60" and through windows or openings 242 and 244 in the preform fixture onto the outer surface of the preform. The nozzles 252, 254 and 256 blow cooling fluid through the openings 242 and 244 into the preform fixture 62″ and onto the outer surface of the preforms. There are no nozzles for cooling the preforms, but it should be understood that the cooling station 250 may be implemented with as many nozzles as desired to cool the outer surfaces of any desired number of preforms.

The additional cooling station 250 enables simultaneous cooling of the preform 48 from the inside and the outside using a separate cooling device from the removable plate 60″. This solution makes the removable plate 60″ very light and very fast and easy maintenance. If necessary, the preform fixing device 62" can clamp the preform only at the neck, thus leaving more windows for blowing cooling fluid to cool the outside of the preform.

According to another embodiment of the invention, said removable plate may comprise external cooling means using blown air or may not comprise cooling means. In both cases, internal cooling is performed using the novel cooling method and apparatus to which the present invention relates.

The novel cooling method and apparatus to which the present invention relates is very advantageous for cooling preforms molded in high cavity molds. It is well known that the temperature of molten resin flowing through a mold can vary widely for a number of reasons, including: (a) uneven heating of the hot runner manifold; (b) formation of Boundary layer; (c) non-uniform cavity cooling; (d) ineffective cooling at the nozzle part of the model. One consequence of the temperature variation across the mold is that the cooling time must be adjusted at local heights to cool the hottest preforms before crystallization occurs in the final preforms. In order to prevent the formation of crystallized regions, the cooling system involved in the present invention can provide a different cooling method, which can be changed according to the temperature characteristics of each model. Sensors may be provided in the removable plate 60 to adjust the amount of cooling for each cooling pin 74 . Another consequence of the uneven temperature distribution within the mold is that the nozzle located on the domed portion 22 of the preform is in most cases the hottest part of the molded preform. Because the nozzle section cools more slowly in the mold closed position, if the cooling time in the mold is too long or additional cooling is not provided outside the mold, then this section will likely crystallize. According to the present invention, blowing cold air into the preform by means of cooling pins 74 and in the vicinity of the nozzle area is a novel operation which is very effective in preventing the formation of crystallized regions in the preform.

The innovative cooling method and apparatus of the present invention also has the advantage of compensating for cooling inefficiencies of the removable plates. Due to incomplete contact between the hot molding and the cooling tubes, the temperature of the molding maintained by the removable plate may vary through the plate. According to the invention, temperature sensors located within the removable plate and cooling frame can be used to provide information to a cooling control unit that varies the cooling flow to each preform.

So far, the above-mentioned adapted cooling method is also beneficial, because it is considered that the temperature of the mold in which the preform is molded can vary within a day, due to the function of the special resin, the function of the mechanical equipment, or due to inappropriate conditions caused by the hot nozzle. Stem action or localized changes in preform thickness due to the core rod in the mold cavity. These conditions can neither be predicted nor easily determined; however, the present invention provides a mechanism to adjust the cooling step after each cavity molding according to the temperature of each molded article or preform.

Significant cycle cycle reduction for increased mold cooling time margins can be achieved by simple design and movement of removable plates and cooling frames. This also allows for very stringent assembly, maintenance and operation constraints on the rigidity, movement accuracy, positioning etc. between the cooling pins on the removable plate and vibrating table and the molding and preform. The location of the cooling frame with dowels is also determined in such a way as to reduce the "footprint" of the overall machine.

This point is also described with reference to Figures 13(a) and 13(b), which show another embodiment of the invention where during the additional air cooling step, The removable plate 60 remains in a vertical position, that is, parallel to the templates 32,36. The cooling frame 98 is conveyed to the removable plate 60 and the cooling pins 74 enter the molding or preform 48 . After all the preforms have cooled, the cooling frame 98 is retracted, the removable plate 60 is turned through 90° parallel to the conveyor 114 , and the cooled preforms are removed from the plate 60 . This method simplifies the design of the cooling frame, which does not require turning means and means to avoid interference of the cooling frame with the preforms ejected from the plate.

Reference is also made to Fig. 14 which shows another embodiment of the invention in which said automatic and removable plate 60 comprises additional translation means 150 to move the preforms along an axis parallel to the axis of rotation of the preforms. This additional movement of the preform simplifies the cooling frame 98 which remains stationary during the cooling process. As shown in FIG. 14 , said removable plate 60 or other means for securing said preforms is moved along axis X towards a stationary cooling frame 98 . After the cooling step, the removable plate 60 is turned through an angle of 90 degrees so that it faces the conveyor 114 to eject the cooled preforms.

Reference is now made to FIG. 15 which shows the new air cooling arrangement associated with said removable plate 60 . The solution shown in the figure does not require a separate frame for holding the cooling pins, thereby reducing the size of the cooling system and the injection molding equipment. This new cooling pin 174 is U-shaped and can simultaneously move all the preforms parallel to each other so that they can be introduced into said preforms and can be driven by a piston BB or any other known means. Thin strips move them out of the preform. The pins 174 are also rotatable about an axis "A" parallel to the preform so that they can be brought into or moved out of the axis in alignment with the preform. This simultaneous rotation of all pins 174 may be accomplished by any suitable means known in the art. According to the present invention, the U-shaped cooling pin 174 has an arm "A" capable of entering the preform, an arm "C" parallel to the arm "A" for moving the arm "A" and a to arm "B" connecting the arms "A" and "C". The rotation of the pin about the axis A of the arm "C" can be done in different ways. As shown in Figure 15, this is accomplished using an elongated rack 178 operated by piston AA which is centered with a piston 180 connected to arm "C" of each cooling pin. The same rotation as above can be accomplished using friction means, one translating and the other rotating. During the movement of the preform 48 from the core 38 to the cooling tubes 62 of the removable plate 60, the U-shaped cooling pins 174 may "stay" in a specific position adjacent to each cooling tube 62. positioned so that they do not interfere with the moving preforms and require less space to open the mold. Immediately after securing the preform 98 in the removable plate 60, the cooling pins 174 connected to the plate 60 are advanced using the piston BB and belt 176 and when they reach a point where the arm "A" is in the position of the preform. At the height above the top of , they are turned in a manner centered on the preform and finally they are introduced into the preform by means of the return of the piston BB. The fixed contact between the strap 176 and each arm "C" may be accomplished by a coil spring 182 pressing against a shoulder 181 or by any other suitable means. Blow air is provided to each cooling pin by means of a hose 184 through arm "C". Such cooling pins connected to the removable plate have the following advantages: simplification and reduction in size of the cooling system, increased cooling efficiency, since the internal Cooling, internal cooling is possible during the movement of the removable plates and in particular the cooling of the preforms by means of the removable plates can be carried out continuously for a long time. During ejection of the cooled preforms, the cooling pins have to be turned again to their original position so that they are no longer centered on the preforms.

Referring now to Figure 12, there is shown an air cooling device 210 comprising cooling channels 210 in the mold halves 32, 36 to allow the removable The preform, held by the mandrel, is allowed to cool before the plate enters the molding area. This additional cooling step will further solidify the preform before the removable plate is brought into the molding area and before being transferred to the removable plate.

According to another embodiment of the invention, as can be easily understood from the other figures in this application, said automatic and removable plate retains only one set of preforms. After the injection step, the removable plate stays outside the molding area and cool air or cold air is blown into each preform from the cooling pins. Said cooled preforms ejected from the removable plate will be brought back into the preform-free molding area.

FIG. 23 shows another configuration of the frame 98 for securing the cooling pin 74 . As shown in this figure, the frame 98 may have cooling pins 74 on two opposing surfaces. Additionally, the frame is rotatable about a first axis 300 and a second axis 302 perpendicular to said first axis 300 . Any suitable means (not shown) known in the art may be used to rotate the frame 98 about the axes 300 and 302 .

With this configuration, it is possible to engage the first set of cooling pins 74 with the preform 48 in one of the removable plates 60 and initiate internal cooling of the preform. The preform 48 can then be moved from the holding device 62 of the removable plate 60 onto the cooling pin 74 . Space 98 may then be rotated about one or more of axes 300 and 302 while internal cooling of preform 48 occurs with cooling pins 74 . The second set of cooling pins 74 may engage the second set of preforms 48 secured in the removable plate 60 when the first set of preforms reaches the left hand position shown in FIG. 23 . If desired, the left hand preform 48 may be externally cooled by conduction with a cooling station 304 having a plurality of nozzles (not shown) to blow cool air onto the outer surface. The frame 98 may have a preform holding plate 308 attached thereto, if desired.

Claims (15)

1. A method of cooling a molded article (48) comprising a first region (22) of relatively high heat and an adjacent region of relatively low heat, said method comprising: The molded article (48) is removed from the mold comprising mold halves (16, 18, 32, 36), said molded article (48) is moved into the fixture (62) of the end-of-arm tool (60), and the The molded article maintains a certain heat, the end-of-arm tool is operated between a first position and a second position, the first position is a fixture (62) for receiving the mold half (16, 18, 32, 36), said second position being outside the mold halves (16, 18, 32, 36); Retrieving the end-of-arm tool from between the mold halves (16, 18, 32, 36) to the second position; One time after the end-of-arm tooling (60) is retrieved from between the mold halves (16, 18, 32, 36) to the second position, the cooling pins (74, 174) are inserted into the molding (48), while securing the molded article within said fixture; The method is characterized by: An open system is formed with respect to the cooling pin and the molded article, the open system having channels which allow the ventilation of the gaseous cooling fluid from the interior of the molded article (48) to the surrounding environment, the open system being formed by placing the cooling pin relative to The open end of the molding (48) is positioned to define a space between the outer surface area of the cooling pin and the open end of the molding (48) adjacent the outer surface area, wherein the space defines the channel; and A gaseous cooling fluid is forced to flow along the internal channel (90) of the cooling pin, which terminates in a tip (92) which, when inserted into the molded article (48), contacts said first region (22 ), the gaseous cooling fluid is discharged from the tip (92) mainly in the direction of the first region to begin to enhance cooling in at least the first region (22), thereby allowing the gaseous cooling fluid to flow from the interior of the molded article and through The channel vents to the surrounding environment and, when located within the molded article, the inner channel and tip together focus the cooling fluid on the first area. 2. A method of cooling a molded article (48) as claimed in claim 1, wherein the gaseous cooling fluid is cooled compressed air blown along the internal channel (90). 3. A method of cooling a molded article (48) as claimed in claim 1 or 2, further comprising applying cooling to an outer portion of the molded article (48) while the molded article is secured in a fixture, wherein said giving the molded article ( The application of cooling to the outer portion of 48) and the forced flow of the cooling fluid along the inner passages occur either simultaneously, not completely simultaneously, or sequentially. 4. The method of cooling a molded article (48) as claimed in claim 1 or 2, further comprising varying the amount of cooling fluid delivered by the cooling pin over time. 5. A method of cooling a molded article (48) as claimed in claim 1 or 2, wherein the tip is adapted to generate a diffuse cooling fluid flow therefrom. 6. A method of cooling a molded article (48) as claimed in claim 1 or 2, wherein the tip of the cooling pin is introduced into the preform to a depth to allow the coolant to reach and cool the inner domed portion of the preform. 7. A method of cooling a molded article (48) as claimed in claim 1 or 2, further comprising: spacing the tip (92) a first distance d from the first region of the molded article (48); and spacing the sidewall (224) of the cooling pin (74, 174) from the inner sidewall (228) of the molding (48) by a second distance D; Wherein, the ratio d:D of the first distance to the second distance is in the range of about 1:1 to about 10:1. 8. A device for cooling a molded article (48) produced in an injection mold formed by half-moulds (16, 18, 32, 36), the molded article having a relatively high heat The first zone (22) and the adjacent zone in relatively low heat, said device comprises: An end-of-arm tool (60) having at least one fixation device (62), in use, the end-of-arm tool (60) is operated between a first position and a second position, the first position is to place a molded article (48) Received into a position between the mold halves (16, 18, 32, 36) of a corresponding one of said at least one fixture (62), said second position being outside the mold halves (16, 18, 32, 36) ; in use, placing the molded article (48) into a corresponding one of said at least one fixture (62) while the molded article retains a certain amount of heat; Cooling pins (74, 174) on the frame (98) adjacent to the second position, the cooling pins having pointed ends (92), and the frame (98) being adapted to move relative to the end-of-arm tooling (60) in use to Inserting the cooling pins (74, 174) into the molding after the end-of-arm tool (60) reaches the second position; characterized by: The cooling pins (74, 174) have internal passages (90) that terminate in a tip (92) when inserted into the molding (48) by relative movement of the frame (98) and end-of-arm tooling (60) Located within the molding but spaced from the first region (22), wherein the cooling pins (74, 174) are in use connectable to a cooling fluid delivery system for forcing a gaseous cooling fluid along the internal passage (90) to expel gaseous cooling fluid from the tip (92) primarily in the direction of the first region to enhance cooling in at least the first region; During expulsion of the gaseous cooling fluid from the tip (92), the frame (98) is positioned relative to the end-of-arm tool to define, in use, an open system with channels that allow the ventilation of the gaseous cooling fluid from the interior of the molding (48) into the surrounding environment; and The device is operable to isolate the frame from the end-of-arm tooling (60) during expulsion of the gaseous gaseous cooling fluid from the tip (92), the open system of channels passing through holes in the outer surface of the cooling pins (74, 174). A space is created between a region and the open end of the molding, which in use is located within its corresponding fixture. 9. Apparatus as claimed in claim 8, wherein the apparatus is arranged to introduce the tips of the cooling pins into the preform to a depth to allow the coolant to reach and cool the inner domed portion of the preform. 10. Apparatus as claimed in claim 8 or 9, wherein the frame positions cooling pins within the molding (48) so as to: i) the tip (92) is spaced a first distance d from the first region of the molded article (48); ii) a second distance D from the side wall (224) of the cooling pin (74, 174) to the inner side wall (228) of the molding (48); And a ratio d:D of the first distance to the second distance is in the range of about 1:1 to about 10:1. 11. Apparatus as claimed in claim 8 or 9, wherein the gaseous cooling fluid is cooled compressed air blown along the internal channel (90). 12. Apparatus as claimed in claim 8 or 9, further comprising a valve for supplying a quantity of gaseous cooling fluid to the cooling pins (74, 174). 13. Apparatus as claimed in claim 8 or 9, wherein the tip has one of a diffuse nozzle configuration and a straight wall nozzle configuration, the internal passage and the tip focusing the gaseous cooling fluid primarily around the first The area of the area (22). 14. The apparatus of claim 8 or 9, wherein the cooling pin is one of: i) a diameter that varies along its length; ii) Transverse fluid outlets (82) or radial conduits (320) at the sides of the cooling pins, which are joined to the internal passages (90) and used to direct cooling fluid to the die one of the neck (13) and body portion of the article; iii) grooves along the outer surface of the cooling pins (74, 174); iv) ribs spaced around the periphery of the cooling pin (74, 174), which protrude from the cooling pin to reduce the outer surface of the cooling pin to the molding (226, 228) over the length of each rib in use ) dimensional separation of the inner walls; and v) A plurality of contact elements (88) along the outer surface of the cooling pin (74, 174). 15. The apparatus of claim 8 or 9, wherein; The end of the arm tool (60) supports a plurality of fixtures; and The frame includes fewer cooling pins (74, 174) than fixtures on the end-of-arm tool; Thus, in use, only selected ones of the moldings in each fixture are cooled by the aligned insertion of the tips of the cooling pins into each selected molding.

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