NL1003525C2 - Method and device for manufacturing plastic containers, in particular suitable for polycarbonate bottles. - Google Patents

Description

Title: Method and device for manufacturing plastic containers, in particular suitable for polycarbonate bottles.

The invention relates to a method for manufacturing bottle-shaped plastic containers, in particular suitable for the production of poy carbonate bottles, wherein an elongated preform is first formed in an injection molding station in an injection molding cavity in which an elongated core is provided along the longitudinal axis of the core extending through the core, then the preform extends, is removed from the injection mold cavity and, after possibly passing through a conditioning station in a blowing station, is inflated into a container with the final desired shape and the container finally in an ejection station will be removed.

The invention also relates to an apparatus for applying the method.

Such a method and device are known from practice. The prior art uses an injection molding device with a horizontal machine bed, a stationary or up and down movable frame plate mounted above the machine bed and a carousel plate mounted below the frame plate, which can rotate about a central axis. The machine bed carries half of an injection mold with one or more mold cavities, a blow mold and an ejection station. Opposite said half of the injection mold, the frame plate is provided with openings via which one or more cores can be introduced into the mold cavity (s). The frame plate further carries means at the location of the blowing station to stretch (stretch) the preforms and on the bladders. Usually, between the injection molding station and the blowing station there is a further conditioning station, where the preforms to be inflated are thermally brought into a suitable condition for stretching and inflation.

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The carousel plate is provided at the bottom, corresponding positions with each station, with one or more neck rings which can hold the preforms formed in the injection molding station after the cores have been pulled out of the mold cavities 5. When the cores have been moved up relative to the frame plate and, if necessary, the frame plate has also been moved up relative to the machine bed, the preforms produced therefore hang in the neck rings. Then, when the carousel plate is rotated, the preforms are brought through the conditioning station to the blowing station, and then, still hanging from the neck rings, the resulting containers are conveyed to the ejection station, where the neck rings are opened.

The technique described above has been called the one-step method because the containers are manufactured in a single pass. This technique has hitherto been used for PET bottles. A drawback of PET bottles is that they cannot be cleaned at a sufficiently high temperature to be used, for example, as a refillable bottle for milk. At temperatures of 70 ° C and higher, there is a risk of a PET bottle shrinking. This drawback does not exist when using other material, such as polycarbonate. Polycarbonate bottles can be cleaned at a high temperature and are therefore suitable for use as, for example, a refillable milk bottle.

The fact that polycabronate containers can be cleaned at a higher temperature than, for example, PET bottles, also means that the injection molding of the preforms for polycarbonate bottles and the inflation thereof must also take place at a higher temperature (180 to 190 ° C). In the known technique, however, this leads to problems, because after the injection molding the preforms are moved freely hanging from the neck rings to the following stations. The preforms can deform during the rotary movement of the carousel plate, which is of course very undesirable. This problem can be somewhat reduced by inflating the preforms at a lower temperature (+ 160 ºC). In that case, however, tensions occur in the final product which make the final product vulnerable. This can again be compensated by a greater wall thickness, but this makes the holder heavier and more expensive.

The object of the invention is to overcome the outlined problems and in general to provide a method and apparatus suitable for manufacturing containers suitable for high-temperature cleaning, such as, for example, polycarbonate bottles. For this purpose, according to the invention, a method of the above-described type is characterized in that each preform is removed from the injection molding cavity in the at least partly lateral direction after removal therein, from the injection molding station to the blowing station, the preform hanging in a neck ring and is internally supported by the core on which the preform is formed, which core extends into the preform from above and is heated, and that the core is then moved with the container blown in the blow station to the ejection station and then again to an injection molding station brought.

According to the invention, a device of the type described above is characterized in that the core moves with the carousel plate and the associated neck ring to support the preform during the movement from the injection molding station 25 to the blowing station.

It is to be noted that French patent no. 1406520 discloses a method according to which a conically shaped preform is formed on a core provided with a drawing pin, wherein the preform is very strong (300% -600%) after opening the mold cavity. extended. However, a sideways transport of hanging preforms, where damage could occur, has not been described.

In the following, the invention will be further described with reference to the accompanying drawing of an exemplary embodiment.

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Fig. 1 and Fig. 2 schematically show in top view and in side view an example of a known device for manufacturing plastic containers; Fig. 3 and Fig. 4 similarly illustrate an example of a method and device according to the invention; and figure 5 schematically shows an example of a blowing station of a device according to the invention.

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Figure 1 and Figure 2 schematically illustrate the operation of a known device for manufacturing plastic containers according to the blow-molding principle. The known device is designed for producing PET bottles 5 and is of a type manufactured, for example, by Nissei ASB Machine Co. Ltd. is put on the market. The known machine comprises a stationary machine bed 1 and a frame plate 2 mounted above the machine bed, which is fixedly mounted or movable up and down depending on the type of molds used. The machine bed carries an injection mold part 3 with one or more mold cavities, a conditioning device 4, and a blowing mold part 5, which form part of an injection station 6, a conditioning station 7 and a blowing station 8. distributed along the periphery. 5 each consisting of two parts which have a vertical interface or are movable up and down relative to the machine bed, as is usually the case with the injection mold part and the conditioning device, the frame plate need not be movable up and down. If the parts 3, 4 and 5 are not divisible, however, the frame plate 2 and / or the parts 3 and / or 4 and / or 5 must be movable up and down in order to be able to transport the holders from one station to another . In this example, these stations are each positioned at an angle of 90 ° from each other, as can be seen in figure 2. Another ejection station 9 is positioned at 90 ° past the blowing station 8.

A rotating carousel plate 10 is mounted under the frame plate 2, which carries one or more neck rings 11, 12, 13 at positions corresponding to the stations. Furthermore, one or more cores 14, which can be lowered by the corresponding neck rings 11 into the injection mold part 3 to accommodate one or more preforms during the injection phase, are located above the frame plate at the injection station 6. - to shape. After a preform is obtained in this way, the mold formed by the mold part 3 and the core 14 opens by either the mold part 3 opening or moving downwards or the frame plate 2 and the core 14 moving upwards. In any case, the core 14 moves upwards relative to the frame plate, so that the newly formed preform hangs freely on the neck ring 11 and the carousel plate is free to rotate 90 ° in the direction of the arrow 15. The newly formed preform is thus brought to the conditioning station 10 to be prepared for the blowing operation in the blowing station. At the same time, at least one new preform is formed in the injection station. The carousel plate then rotates through 90 ° again, so that the conditioned preform reaches the blowing station 8. In the blow station 15, the preform is received in a blow mold and inflated to the desired shape. After opening the blow mold, the carousel plate rotates again through 90 ° so that the finished container reaches the ejection station 9. Simultaneously, a newly conditioned preform reaches the blowing station 8 and a newly formed preform reaches the conditioning station 7. During all transport phases, the preform hangs from a neck ring 11.

In the blowing station, in preparation for inflation of the preform, the preform is first stretched with the aid of a draw pin, which is inserted into the preform through the neck ring and pushes the bottom of the preform away in a direction away from the neck ring.

The method and device according to the invention schematically illustrated in Figures 3 and 4 deviate from the known method and device described above in that each neck ring 11, 12, 13 is now provided with a core 20, 21, 22, which rotates with the carousel plate. The warm preforms are thereby supported and held during transport between the injection station and the conditioning station and between the conditioning station and the blowing station and also during the stay in those stations by a neck ring and a core. This technique makes it possible to move the preforms in a weaker state. The preforms can therefore be 5 warmer than is the case with the known technique. This in turn makes it possible to process, for example, polycarbonate preforms at a suitable high temperature and / or to transport the preforms more quickly after the injection phase.

The stabilizing effect of the moving cores 10 can be further enhanced by making the cores and thus the preforms longer than usual. In this connection, it is noted that when using PET as a raw material it is necessary to stretch a preform in the longitudinal direction before blowing up the preform, because stretching only results in the desired molecular structure with the associated mechanical strength. However, it has been found that this effect does not occur with polycarbonate and that a polycarbonate preform does not need to be stretched lengthwise or only slightly. In PET preforms, the stretching operation results in an increase in length of the order of 50%. According to the invention, however, in the processing of polycarbonate preforms, cores are preferably used which have a length which deviates only a few centimeters from the length of the final product. By inflation, a length increase in the order of, for example, ± 15% takes place. In principle, the core, and thus also the preform, could even have a length almost corresponding to that of the final product.

According to the invention, cores are used which have a heated jacket and an air duct closed by a central pin during the injection phase and the conditioning phase. The air duct is opened in the blowing station so that the preform can be inflated to its final shape, as will be described in more detail later.

Figure 5 schematically shows an example of a core 20 according to the invention, which is located in the blowing station 8. The core has a heated jacket 30, which in this example is heated by warm oil circulating through a channel 31,32. The preform to be inflated is indicated at 33. In the center of the core, in a longitudinal bore 34, is a pin 35, which is provided at the free end of the core with a closing member 36, which in this example is a conical plug. The bore is slightly wider than the pin, so that an annular air channel 37 is present around the pin, which is closed by the plug 36 during the injection phase. Alternatively, the pin can also have an internal air channel.

In the blowing station, depending on the material of the container, the pin 35 is pushed into the blowing cavity 38 a little or a greater distance beyond the end of the core. In the case of a PET preform, the pin is moved to the bottom of the bladder cavity so that the desired stretching operation takes place. Air is also blown into the preform via the air-20 channel. This is possible because the conical plug 36 no longer closes once the pin has shifted slightly.

In the case of a polycarbonate preform, the procedure is preferably as follows. First, the pin is pushed out of the core over a short distance, for example 0.5 S 1 mm. The closing member 36 opens thereby, so that air can be blown into the preform. The air supply is continued, whereby the wall of the preform is first inflated around the free end of the core into a kind of balloon. When the balloon is against the bottom of the bladder, the pin 35 is pushed further down to fix the balloon in the bladder. The preform is then further inflated until the final product in the form of the blow cavity is obtained. The blow mold then opens and the carousel plate rotates 90 ° further, so that the final product can be removed in the core ejection station and from the neck ring.

The operation of the pin 35 takes place by means of a push pin 40, which is located in a frame 41 mounted above the blowing station, and which can be operated by a cylinder 42. The push pin 40 can be temporarily coupled in one of the known ways to the central pin located in the core. In the example shown, a click connection is used, as is also the case with interchangeable hand tools. Near the lower end, the push pin has a constriction 43, which can cooperate with balls 44 or the like around a receiving cavity 45 and a coupling member 46 of the central pin 35. Other coupling methods, for instance with the aid of a bayonet closure or the like, are possible.

The cores, as already noted, are heated by hot oil. Since the cores rotate with the carousel plate 20, the oil must be supplied via a tube or hose with a central rotary coupling, as shown in figure 3 at 50 and rotating pipes 51 to 54. The drive of the carousel plate can then be used from a hollow shaft or, as shown in Figure 3, from a sprocket 55, 25 driven by a motor drive wheel 56 or by an eccentric drive.

It is noted that after the foregoing various modifications are obvious to the skilled person. For example, if desired, the cores can also be electrically heatable. Such modifications are considered to fall within the scope of the invention.

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Claims (12)

9 1. A method of manufacturing bottle-shaped plastic containers, wherein an elongated preform is first formed in an injection molding cavity in an injection molding cavity in which an elongated core provided with a stretching extending through the core along the longitudinal axis of the core, then extends the preform is removed from the injection mold cavity and, after any passing through a conditioning station in a blowing station, is inflated into a container with the final desired shape and the container 10 is finally removed in an ejection station, characterized in that each preform is removed therefrom the injection mold cavity is transported in at least partly lateral direction, from the injection molding station to the blowing station, the preform hanging in a neck ring and supported internally by the core on which the preform is formed, which core extends and heats from above in the preform and that the core is subsequently inflated with the h older is moved along to the ejection station and then returned to an injection molding station. 2. Method according to claim 1, wherein cores are used, which are provided with a stretching pin, which closes an air channel in the core in the injection-molding position and which is temporarily coupled in the blowing station to a pusher, with which the central pin relative to the core is pushed further into the bladder cavity of the blowing station to release the air channel, characterized in that in the manufacture of polycarbonate containers and similar containers the draw pin is pushed into the bladder cavity only to a very small extent, which is then preformed inflated until the preform rests at least partly against the bottom of the bladder cavity and that the pen is then moved further into the bladder cavity until the pen fixes the part of the preform lying against the bottom and that the preform is subsequently further inflated. 1003525 10 Method according to claim 2, characterized in that cores are used which reach relatively far into the bladder cavity. Method according to claim 3, characterized in that cores of such length are used that the preforms of the order of 25% or less, more in particular 15% or less, are elongated in the blowing station. 5. Apparatus for manufacturing bottle-shaped plastic containers comprising a carousel plate provided with neck rings, which is driven in rotation for operation in order to lead the neck rings from an injection molding station, if necessary, past a conditioning station to a blowing station and then again via an ejection station, wherein in the injection molding station 15 at least one preform is formed on a core reaching into a mold cavity, the preform being inflated into a container in the blowing station, characterized in that the core moves along with the carousel plate and the associated neck ring around the preform support movement from the injection molding station to the blowing station. 6. Device as claimed in claim 5, wherein the cores are provided with a central pin arranged in the cores, which closes an air channel formed in the cores in the injection molding position, and wherein operating means are provided in the blowing station which can temporarily cooperate with the central pin for causing it to move into the blowing cavity of the blowing station and to release the air channel, characterized in that the operating means comprise an up and downwardly movable push pin 30 mounted above the blowing station, the push pin and the central pin being provided with each other interlocking coupling members. 7. Device according to any one of claims 4 to 6, particularly suitable for the manufacture of polycarbonate containers or similar containers, characterized in that the cores are relatively long relative to the depth of the bladder cavity. 1003525 11 Device according to 7, characterized in that the cores have a length of the order of 75% or more, in particular of the order of 85% or more, of the depth of the bladder cavity. Device according to any one of claims 4 to 8, characterized in that the cores have a heatable jacket. 10. Device according to claim 9, characterized in that the cores are each coupled to an oil pipe for the supply of hot oil. 11. Device according to claim 10, characterized by a central oil supply line which is connected via a rotary coupling to the individual oil lines which lead to the cores. Device according to any one of claims 4 to 11, characterized by an eccentric drive device for the carousel plate. 1003525