DE19958435A1 - Method and device for blow molding containers - Google Patents

Abstract

The inventive method and device serve to blow mold containers made of a thermoplastic material. The containers are produced from a tempered preform inside a blowing mold, which is positioned in the area of a blowing station (33), by the action of a pressurized medium. At least two blowing mold segments are used as a blowing mold. The blowing stations are transported along a closed circulating path. The circulating path of the blowing stations is divided into at least two path segments (63, 64), and an entry for preforms and an exit for blown containers are assigned to each path segment. The preforms are completely shaped into the containers in the area of each path segment.

Description

The invention relates to a method for blow molding of containers made of a thermoplastic material, at that of the container within a blow mold, which in the loading position of a blowing station, by action a pressurized medium from a tempered preform is manufactured and in which as Blow mold used at least two blow mold segments as well as the blowing stations along a closed circulation route are transported.

The invention also relates to a device for blow molding of thermoplastic containers material that has at least one blowing station  has at least one blow mold consisting of at least is formed two blow mold segments and one Has transport device for the blowing stations, which the blowing stations along a closed um transported as well as the preforms tempered in the area of at least one heating device become.

With such a container formation by blowing pressure pre-tempered preforms a thermoplastic material, such as Vor moldings made of PET (polyethylene terephthalate), inside a blow molding machine with different processing states tions fed. Typically, such a Blower a heater and a blower direction in the area of which the previously tempered Preform through biaxial orientation to a container ter is expanded. The expansion takes place with the help of compressed air entering the preform to be expanded is initiated in a controlled manner. The procedural Procedure for such an expansion of the preform is explained in DE-OS 43 40 291.

The basic structure of a blowing station for loading Container formation is described in DE-OS 42 12 583 described. Ways to temper the Preforms are explained in DE-OS 23 52 926.

Within the blow molding device, the Preforms as well as the blown. Container with help different handling devices trans be ported. In particular, the Use of transport mandrels on which the preformlin be plugged on. The preforms can can also be handled with other carrying devices. The use of gripping pliers for handling pre  moldings and the use of expanding mandrels, which are used for Holder in a mouth area of the preform are also available Constructions.

The handling of the preforms already explained follows on the one hand in the so-called two-stage procedure ren, in which the preforms first in one Injection molding process, then between stored and only later with regard to their temperature conditioned and inflated to a container. On the other hand, it is used in the so-called One-step process in which the preforms are telbar after their injection molding manufacture and an adequate hardening suitably tempered and then inflated.

With regard to the blowing stations used are un Different embodiments are known. At Blassta tions arranged on rotating transport wheels is a book-like opening of the form encountered frequently. But it is also possible to rela tiv mutually movable or differently guided Insert mold carrier. For fixed blowing stations, which are particularly suitable for several cavities for container formation, are typically plates arranged parallel to each other as mold carriers used.

In order to achieve favorable production prices, we will offer strives to blow machines with the highest possible throughput rate rate to operate. The throughput rate is disregarded on the mechanical strength of the construction used elements largely determined by the process time that to transform the preforms into the containers is such. In particular, this should be taken into account  conditions that a support of the container required as long until there is sufficient material cooling and Material consolidation has occurred to an unab to avoid visible material deformation leading to Ab lead deviations from the desired container contour could. The blown containers are therefore long Leave it in the blow mold and counteract it with its internal pressure pressed the mold wall until at least the outer dimensions areas have experienced sufficient cooling ben. The blow mold must therefore be sufficiently cool be cured.

When using blowing wheels on which the Blow stations are arranged, the problem occurs that with increasing number of blowing stations also the Diameter and the weight of the blowing wheel increases. The a substantial proportion of the weight is along the circumference Ges of the blowing wheel isolated. Considering the resulting weight distribution and the high peripheral speeds result in considerable kinetic energies, which are especially important for a such rapid braking to considerable mechani problems. They also contribute to normal operation of the device due to the circular orbit significant centrifugal forces on the transport elements as well as the transported ones Preforms and blown bottles. When ver The use of conventional blowing wheels is therefore the product tion performance limited because the diameter of the Blower wheels and the number of on the blow wheels ordered stations also only to a limited extent can be increased.

The object of the present invention is a method to improve ren of the type mentioned in the introduction, that the production output is increased without  large kinetic energies occur.

This object is achieved in that the circulation route of the blowing stations in at least two ways segments is divided so that each path segment one Input for preforms and output for blown ones Container is assigned and that in the area every way segmentes a complete reshaping of the preforms into the container.

Another object of the present invention is to ne device of the type mentioned in the introduction construct an array of a large number of blowing stations on a blowing wheel. This object is achieved in that the transport device for the blowing stations arrange at least two at a distance from each other th coupling points with temperature control devices for the Preforms is connected.

By dividing the blowing wheel into several ways segments it is possible to use the blowing wheel with a small to let their speed rotate than with a conventional one tional construction. For the execution of an op It is only necessary a predetermined time for the container formation put. Which movement path, however, from the Blassta tion during this period is for the Container shaping without meaning. The division of the Circulation route in several route segments thus enables a lower transport speed for the To provide blowing stations and through the assigned se provide input for the preforms and the expenses for the blown containers, however, the respective pre adhere to the given process time.  

This makes it easy to implement mechanically supports that the blowing station essentially ent be moved along a circular orbit.

Optimal use of the available Process time can take place in that along a complete circulation path of the blowing stations of each Blowing station a number of containers is produced multiply the number of cavities per blowing station adorned with the number of path segments.

To increase the production output is suggested that at least two in the area of each blowing station Containers made from preforms at the same time the.

To provide a modular machine concept it is proposed that each path segment has a separate one Heating device is assigned.

This will ensure reliable material transport supports that the connections in the area of coupling are designed as transfer wheels.

A movement of the blowing stations that is not susceptible to interference along its orbit is supported by the fact that the transport device for the blowing station as a Blower wheel is formed.

Effective tempering of the preforms can be there be achieved by that the heater with around ongoing transport elements for the preforms is permitted.

A compact implementation is supported  that the heater with a transport chain out is equipped.

According to another embodiment, it is also possible Lich that the heater with a heating wheel is equipped.

An additional modularization of the production facility tion can be supported by the fact that each of the Path segments from an input device for transfer from preforms to the blowing stations and from one Removal device for removing blown containers tern from the blowing stations is limited.

To facilitate the accessibility of the individual Functional components is proposed that the Heaters outside the orbit of the Blow stations are arranged.

Exemplary embodiments of the invention are shown in the drawing shown schematically. Show it:

Fig. 1 is a perspective view of a blow station for the production of containers from preforms,

Fig. 2 is a longitudinal section through a blow mold in which a parison is stretched and expanded,

Fig. 3 is a sketch to illustrate a basic structure of a device for blow molding containers when using two assigned heating sections and

Fig. 4 is a modified compared to Fig. 3 Vorrich device when using four heating sections.

The basic structure of a device for shaping preforms ( 1 ) in containers ( 13 ) is shown in Fig. 1 and in Fig. 2.

The device for forming the container ( 13 ) consists essentially of a blow molding station ( 33 ) which is provided with a blow mold ( 34 ) into which a preform ( 1 ) can be inserted. The preform ( 1 ) can be an injection molded part made of polyethylene terephthalate. In order to enable the preform ( 1 ) to be inserted into the blow mold ( 34 ) and to enable the finished container to be removed, the blow mold ( 34 ) consists of mold halves ( 35 , 36 ) and a base part ( 37 ) which is lifted by a lifting device ( 38 ) can be positioned. The preform ( 1 ) can be held in the area of the blowing station ( 33 ) by a transport mandrel ( 39 ) which, together with the preform ( 1 ), runs through a plurality of treatment stations within the device. However, it is also possible to insert the preform ( 1 ) directly into the blow mold ( 34 ), for example using pliers or other handling means.

To allow compressed air supply line at half the transport mandrel (39), a connecting piston (40) is arranged which supplies (1) compressed air the preform and simultaneously a seal relative to the transport mandrel (39) carries out. In the case of a modified construction, it is in principle also conceivable to use fixed compressed air supply lines.

The preform ( 1 ) is stretched with the help of a stretching rod ( 41 ), which is positioned by a cylinder ( 42 ). Basically, however, it is also conceivable to carry out a mechanical positioning of the stretching rod ( 41 ) via curve segments which are acted upon by tapping rollers. The use of curve segments is particularly expedient when a plurality of blowing stations ( 33 ) are arranged on a rotating blowing wheel. The use of cylinders ( 42 ) is expedient if stationary blow molding stations ( 33 ) are provided.

In the embodiment shown in Fig. 1, the stretching system is designed such that a tandem arrangement of two cylinders ( 42 ) is provided. From a primary cylinder ( 43 ), the stretching rod ( 41 ) is first ge before the start of the actual stretching process in the area of the bottom ( 7 ) of the preform ( 1 ). During the actual stretching process, the primary cylinder ( 43 ) with extended stretching rod is positioned together with a carriage ( 44 ) carrying the primary cylinder ( 43 ) from a secondary cylinder ( 45 ) or via a cam control. In particular, it is contemplated to use the secondary cylinder ( 45 ) in a cam-controlled manner in such a way that a respective stretching position is specified by a guide roller ( 46 ) which slides along a cam track while the stretching process is being carried out. The guide roller ( 46 ) is pressed against the guideway by the secondary cylinder ( 45 ). The carriage ( 44 ) slides along two guide elements ( 47 ).

After the mold halves in the area of supports (48, 49) arranged in mold halves (35, 36) are closed, the carrier (48, 49) relative to each other by means of a locking device (50).

To adapt to different shapes of the mouth section ( 2 ) according to FIG. 2, the use of separate thread inserts ( 51 ) is provided in the area of the blow mold ( 34 ).

In addition to the blown container ( 13 ), FIG. 2 also shows the preform ( 1 ), drawn in broken lines, and schematically a developing container bladder ( 14 ).

Fig. 3 shows the basic structure of a Blasma machine, which is provided with two heating devices ( 52 ) and a rotating blowing wheel ( 53 ). From a preform input ( 54 ), the preforms ( 1 ) are transported into the area of the heating device ( 52 ). Radiant heaters and blowers are arranged along a transport path of the heating device ( 52 ) in order to temper the preforms ( 1 ). After the preforms ( 1 ) have been adequately tempered, they are transferred from a transfer wheel ( 60 ) to the blowing wheel ( 53 ), in the area of which the blowing stations ( 33 ) are arranged. The finished blown containers ( 13 ) are supplied by transfer wheels ( 55 , 56 ) to an output section ( 59 ).

According to a typical embodiment, the heating device ( 52 ) is provided with a transport chain ( 61 ) which guides holders for the preforms ( 1 ) past the heating box. The transport chain ( 61 ) is moved over order steering wheels ( 62 ) in a closed circuit. The circulation can take place, for example, along the circumference of a rectangular base area.

In the embodiment shown in Fig. 3, the circumference of the blowing wheel ( 53 ) is divided into two path segments ( 63 , 64 ). The path segment ( 63 ) is limited by the transfer wheel ( 60 ) and the transfer wheel ( 55 ). The path segment ( 64 ) is delimited by transfer wheels which are corresponding to the transfer wheels ( 60 , 55 ) and perform handling of the preforms ( 1 ), which are tem perated by the second heating section ( 52 ) and which are blown from these preforms derive containers ( 13 ) from the area of the heating wheel ( 53 ). The two heating sections ( 52 ) are designed to be functionally identical to each other.

Fig. 4 shows an embodiment in which four heating devices ( 52 ) are connected to a common blowing wheel ( 53 ). In this embodiment, too, all four heating devices ( 52 ) are essentially functionally identical to one another. By using four heating sections ( 52 ), the blowing wheel ( 53 ) is divided into four path segments.

The subdivision of the blowing wheel into path segments is to be understood here in such a way that there is no rigid assignment to the geometry of the blowing wheel ( 53 ), but that the path segments in question are only positively positioned relative to the arrangement of the heating sections ( 52 ). Due to the rotation of the blowing wheel ( 53 ), different blowing stations ( 33 ) are thus continuously assigned to the respective path segments. An individual blowing station ( 33 ) thus passes through the individual path segments one after the other.

Basically, it proves expedient to dimension all path segments ( 63 , 64 ) of the same length. This enables constant product quality to be supported. As an alternative to the embodiments shown in the figures with two or four heating sections ( 52 ), it is in principle possible to arrange any number of heating sections along the blowing wheel ( 53 ), as long as there is only sufficient space for feeding the preforms ( 1 ) , The removal of the blown container ( 13 ) and the arrangement of the required heating elements is guaranteed.

When using rotating transport elements for the preforms ( 1 ) or the blown containers ( 13 ), different transport concepts can be implemented. For example, it is possible to first circulate the transport elements in the loading area of one of the heating devices ( 52 ), to transfer the preform ( 1 ) together with the associated support device to the blowing wheel ( 53 ) and to remove the blown container ( 13 ) to remove from the support element and to circulate the support element in the next heating device ( 52 ). As an alternative, it is also possible, for example, to implement a circulation of the transport elements separately in the region of each heating device ( 52 ) and to remove the preforms ( 1 ) from the respective transport elements when the transfers are made accordingly.

An important design principle is that the preforms ( 1 ) are transferred to the blowing wheel ( 63 ) by a transfer wheel ( 60 ) which is assigned to a specific heating device ( 52 ) and that the blown containers ( 13 ) are discharged from the Be rich of the blowing wheel ( 53 ) from a transfer wheel ( 55 ) of another heating device ( 52 ) is performed.

Different thermoplastic materials can be used Plastics are used. Can be used at for example PET, PEN or PP.

The expansion of the preform ( 1 ) during the orientation process is carried out by compressed air supply. The compressed air supply is divided into a pre-blowing phase in which gas, for example compressed air, is supplied at a low pressure level and a subsequent main blowing phase in which gas is supplied at a higher pressure level. Compressed air with a pressure in the interval from 10 bar to 25 bar is typically used during the pre-blowing phase and compressed air with a pressure in the interval from 25 bar to 40 bar is supplied during the main blowing phase.

A typical blowing process is carried out in such a way that blowing air is first introduced into the blowing station ( 33 ) to expand the preform ( 1 ). Preferably, the pressure is initially supplied with a pre-blowing pressure, which is typically between 5 bar and 30 bar. Compressed air is then supplied at a main blowing pressure, which is typically in the range from 5 bar to 40 bar.

A supply and discharge of the pressurized medium into and out of the container ( 13 ) can for example through the stretching rod ( 41 ) through and / or through a distance between the stretching rod ( 41 ) and the mouth area of the preform ( 1 ) or the container ( 13 ).

Claims (13)

1. A method for blow molding containers made of a thermoplastic material, in which the container is made within a blow mold, which is positioned in the region of a blow molding station, by the action of a medium under pressure from a tempered preform, and in which at least two are used as blow molds Blow mold segments are used and in which the blow stations are transported along a closed circulation path, characterized in that the circulation path of the blow stations ( 33 ) is divided into at least two path segments ( 63 , 64 ), that each path segment ( 63 , 64 ) an input for the preforms ( 1 ) and an output for blown containers ( 13 ) is assigned and that in the area of each Wegseg element ( 63 , 64 ) a complete deformation of the preforms ( 1 ) into the container ( 13 ) is carried out. 2. The method according to claim 1, characterized in that the blowing station ( 33 ) is moved substantially along a circular circulation path. 3. The method according to claim 1 or 2, characterized in that along a complete circulation path of the blowing stations ( 33 ) from each blowing station ( 33 ) a number of containers is produced, the number of cavities per blowing station multiplied by the number of Corresponds to path segments ( 63 , 64 ). 4. The method according to any one of claims 1 to 3, characterized in that at least two containers are made simultaneously from preforms ( 1 ) in the region of each blowing station ( 33 ). 5. The method according to any one of claims 1 to 4, characterized in that each path segment ( 63 , 64 ) is assigned a separate heating device ( 52 ). 6. Device for blow molding containers made of a thermoplastic material, which has at least one blow station with at least one blow mold, which is formed from at least two blow mold segments and which has a transport device for the blow station, which transports the blow stations along a closed circulation path ported and at which the preforms are tempered in the area of at least one heating device, characterized in that the transport device for the blowing stations ( 33 ) is connected to heating devices ( 52 ) for the preforms ( 1 ) at at least two coupling points arranged at a distance from one another . 7. The device according to claim 6, characterized in that the connections in the area of coupling coupling points are designed as transfer wheels ( 60 ). 8. The device according to claim 6 or 7, characterized in that the transport device for the blowing station ( 33 ) is designed as a blowing wheel ( 53 ). 9. Device according to one of claims 6 to 8, characterized in that the heating device ( 52 ) with circumferential transport elements for the preforms ( 1 ) is equipped. 10. Device according to one of claims 6 to 9, characterized in that the heating device ( 52 ) is equipped with a transport chain ( 61 ). 11. Device according to one of claims 6 to 9, characterized in that the heating device ( 52 ) is equipped with a heating wheel. 12. The device according to one of claims 6 to 11, characterized in that each of the path segments ( 63 , 64 ) from an input device for transferring preforms ( 1 ) to the blow molding stations ( 33 ) and from a removal device for removing blown containers ( 33 ) is limited from the blowing stations ( 33 ). 13. Device according to one of claims 6 to 12, characterized in that the heating devices ( 52 ) are arranged outside the circulation path of the blowing stations ( 33 ).