WO2023232386A1

WO2023232386A1 - Blow molding system and method for operating same

Info

Publication number: WO2023232386A1
Application number: PCT/EP2023/061835
Authority: WO
Inventors: Rolf Baumgarte; Dieter Klatt
Original assignee: Khs Gmbh
Priority date: 2022-05-30
Filing date: 2023-05-04
Publication date: 2023-12-07
Also published as: DE102022113491A1

Abstract

The invention relates to a blow molding system for molding preforms made of plastic in order to form containers, comprising at least one blow mold (1) and a blowing device which is paired with the blow mold (1). The blow mold (1) has at least one first and second blow mold half (2, 3) which can be moved relative to each other via a drive device (4) in order to open and/or close the blow mold (1), and the drive device (4) is an electric drive. According to the invention, the drive device (4) acts at least on the first blow mold half (2) via a toggle lever assembly (7), wherein the closed state of the blow mold (1) is achieved before the dead center of the toggle lever assembly (7) is reached.

Description

Blow molding systems and methods of operation

The present invention relates to a blow molding unit for a blow molding system for forming plastic preforms into containers with at least one blow mold and a blowing device assigned to the blow mold, the blow mold being formed at least from a first and a second blow mold half and at least one of the blow mold halves being openable and/or closing the blow mold is coupled via a drive device designed as an electric drive.

Such blow molding systems are basically known from practice, with the invention particularly referring to blow molding systems for the beverage industry. Accordingly, the containers are preferably beverage containers, for example. B. Drinks bottles. Such beverage containers are usually made from preforms made of polyethylene terephthalate (PET), whereby the preforms are already arranged in the blow mold with a predefined shape and are plastically deformed by applying an internal pressure. The blow mold is designed in such a way that it forms a cavity for receiving the preforms, the cavity having a contour which already corresponds to the contour of the container to be formed.

Particularly in the beverage industry, several blow molds are usually arranged one behind the other on a transport gyro, so that the manufacturing process of the containers takes place essentially continuously, while the blow molds are transported via the transport gyro along a transport direction. For this purpose, the preforms are individually fed to an assigned blow mold and arranged within it by closing the blow mold. The blow mold is closed by a closing movement of the blow mold halves, which are designed to be movable relative to one another. After closing the blow mold, the actual blowing process then takes place by applying compressed air to the preforms via the blowing device. After forming, the blow mold is opened by moving the blow mold halves and the resulting container is removed.

So that the individual movements of the blow mold halves can be synchronized with one another and of the transport gyro, the individual movements are usually positively coupled to one another. This is made possible by a drive device for the blow mold halves, which is designed to be cam-controlled. With a curve control, the movement is effected via a guide roller that rolls along a guide track, which ensures that the individual movements are carried out exactly on the predefined circumferential sections, e.g. B. a transport roundabout. Accordingly, the curve control alone ensures that the blow mold opens at the predetermined position and closes at another predetermined position.

In practice, however, there is an increasing requirement to replace the individual drive devices with electric drives, since this means that drives with significantly lower performance data can be used. In addition, it is now also possible to control and operate several electric drives together in such a way that sufficient synchronization can be achieved between the individual components of an assembly.

Such an embodiment is known, for example, from EP 2 199 061 A1, in which a large number of drive units are to be replaced by an electric drive. Among other things, it is also explained in this context that it is fundamentally possible to realize the closing movement or opening movement of the blow mold using an electric drive. After closing the blow mold, it is then locked to prevent unintentional opening during the blowing process. Such a locking is carried out in particular by a separate pin, which can also be introduced using a separate electric drive.

Before the actual blowing process, in addition to closing the blow mold, it is also necessary that the open gap between the individual blow mold halves is closed by applying pressure in one is reduced to sufficient extent so that the material of the preforms cannot penetrate between the blow mold halves. This is usually achieved via a separate locking device, for which purpose cavity-forming format parts are arranged within the blow mold halves, which can be adjusted relative to sections of the blow mold halves. This is done, for example, by a pneumatic or hydraulic device, which generates a corresponding pressure between the format parts and the other sections of the blow mold halves, so that the format parts of the two blow mold halves are pressed together to a sufficient extent.

EP 2 199061 A1 also provides for such a locking device in which the format parts can be pressed together using a mechanical device. A separate electric drive is also provided for operating the locking device, so that a closing movement of the blow mold is effected using a first electric drive and a locking of the blow mold is effected using a second electric drive.

The solutions known from the prior art have fundamentally proven themselves. However, it has been shown that, especially when integrating electric drives, a large number of drive devices have to be synchronized with one another in order to enable the blow molding system to operate properly.

Against this background, the present invention is based on the object of specifying a blowing system which is characterized by a simplified structure and a simpler operation compared to the solutions known from the prior art.

The object and solution to this problem is a blow molding unit according to claim 1. Accordingly, it is provided that the drive device for opening and / or closing the blow mold acts at least on the first blow mold half via a toggle lever arrangement, with a closed state of the blow mold being before a dead center of the toggle lever arrangement or a closed state of the blow mold is reached before a dead center of the toggle lever arrangement has been reached.

A toggle lever is an arrangement of at least two lever arms that are articulated to each other, with the length of the Lever arms or the ratio of the lengths of the two lever arms to each other, a large stroke with low pressure force can be converted into a small stroke with high pressure force or vice versa. The special feature is also that this gear ratio shifts continuously during the movement, so that, for example, initially a large stroke with low pressure force and then a small stroke with high pressure force can be achieved within one movement.

Especially when integrating electric drives, the torques to be applied are often not sufficient to ensure adequate locking of the blow mold. In contrast to the prior art, a separate locking device can be dispensed with by incorporating a corresponding toggle lever arrangement, so that both a closing or opening as well as a locking of the blow mold can be effected via the one drive device. Accordingly, the toggle lever arrangement acts from the outside on the at least first blow mold half.

A toggle lever arrangement is referred to as a dead center when the two lever arms are arranged along a common line or the individual axes of rotation of the articulated connection points are arranged on a line. The pressure force acting at least on the first blow mold half is greatest when, starting from an opening state, the two lever arms are arranged in front of the dead center in relation to one another. In any case, exceeding this dead center must be avoided, as sufficient pressure cannot then be applied to effect locking. In addition, opening the blow mold halves is made more difficult, as this would require first passing through the dead center, which is associated with the application of a high force.

Although the invention is not limited to a specific embodiment, a preferred embodiment provides that the blow mold halves can be pivoted relative to one another between the closed state and an open state. Within the scope of the invention, these movements exclusively mean a relative movement to one another, and it is irrelevant whether both blow mold halves are designed to be pivotable or not. Basically, it is within the scope of the invention that both the first and the second blow mold halves are designed to be pivotable, in which case the toggle lever arrangement can be applied to both the first and the second Blow mold half acts. Alternatively, it is also conceivable to provide a first toggle lever arrangement for the first blow mold half and a second toggle lever arrangement for the second blow mold half, each of the lever arrangements being driven with a separate electric drive as a drive device. The toggle lever arrangements can then be designed identically to one another.

However, a particularly preferred embodiment provides that the second blow mold half is designed to be immovable. In this context, an immovable design means that when the two blow mold halves pivot relative to one another, only a movement of the first blow mold half is provided. Accordingly, the second blow mold half is firmly mounted on a support, so that the opening and / or closing movement is caused by moving or giving away the first blow mold half. Of course, it is within the scope of the invention that the blow mold halves themselves are attached to a movable support, for example. B. are arranged on a transport gyro, so that the second blow mold half is also designed to be movable with respect to an absolute movement. However, due to the fixed mounting on the carrier, movement on the carrier is excluded. Such a configuration is particularly advantageous in that only one drive device and one toggle lever arrangement are required, so that the number of components to be synchronized with one another can be kept low. However, according to such a configuration, a larger pivoting movement must be made possible with respect to the first blow mold half. In addition, a larger torque of the drive device is also required, since the required pressure force for the tumbler must now be brought about exclusively by a drive device or an electric drive.

A particularly preferred embodiment provides that the electric drive is a servo motor. A servo motor is a special electric motor that allows you to control the angular position of your motor shaft as well as the rotational speed and acceleration. They consist of an electric motor that is also equipped with a sensor for position determination. The possibilities of precise control and regulation make it possible to enable precise pivoting of the blow mold halves over a predefined angular range. A particularly preferred embodiment of the invention provides that the blow mold halves each have a blow mold carrier and a mold part assigned to the blow mold carrier, the mold parts forming a cavity for receiving a preform in a closed state. Such molded parts are basically known from the prior art and enable a predefined design of the container to be formed. By integrating separate molded parts, it is possible to simply replace the molded part when changing formats for the production of differently designed containers, so that, for example, the drive devices or the toggle lever arrangement do not have to be separated from the blow mold halves. Depending on the containers to be formed, format parts with contours of different sizes or contours of different shapes can then be used in the blow mold halves. In such a configuration, the toggle lever arrangement preferably acts on the blow mold carrier or on the blow mold carriers.

The molded parts are preferably arranged immovably within the blow mold halves. According to such an embodiment, it is clear that no additional locking devices are provided between the format parts and the blow mold carriers or between the format parts and the toggle lever arrangement, which require a relative movement of the format parts within the blow mold halves. The structure is therefore fundamentally much simpler than is the case with the solutions known from the prior art. Even when replacing the format parts, it is not necessary to ensure that there is a faultless connection to a locking device. Rather, the molded parts can be arranged in a simple manner on the remaining sections of the blow mold halves and fixed with them. The exchange can therefore take place much faster and more effectively.

A particularly preferred development of the invention provides that the toggle lever arrangement has a first lever arm that is pivotably connected to the blow mold and a second lever arm that is connected to the drive device, the first and the second lever arm also being pivotally connected to one another. In contrast to the first lever arm, the second lever arm is firmly mounted on the drive device, with rotation of the second lever arm occurring due to a rotation of the drive shaft of the electric drive. The connection of the first lever arm to the blow mold takes place at a first articulated connection. And the connection between the two Lever arms are connected to each other at a second articulated connection point, the axes of rotation of the connection points being arranged parallel to the axis of rotation of the drive shaft. According to such an embodiment, the lever arms enclose an angle between 150° and 179°, preferably between 160° and 170°, in the closed state. In the open state, the angle is between 10° and 70°, preferably between 20° and 50°. The dead center of the toggle lever arrangement, on the other hand, is reached at an angle of 180°, with the previously specified angular ranges ensuring that a maximum compressive force can be exerted on the blow mold halves relative to one another, so that the torque created by the drive action can cause a maximum locking of the blow mold.

In such a closed state, the force acting on the blow mold by the toggle lever arrangement is preferably between 30,000N and 100,000N, particularly preferably between 40,000N and 80,000N.

A preferred development further provides that the blow mold halves can be pivoted between the open state and the closed state over an angle between 20° and 90°, particularly preferably between 40° and 70°. The angle is dimensioned such that, on the one hand, the preforms can be inserted particularly well and the finished containers can be removed. In addition, the angle is deliberately kept as small as possible in order to keep the time required for the opening and closing process short.

A further development of the invention further provides that the blow mold has a base part which can be moved, in particular pivoted, relative to the blow mold halves via a base drive device. Accordingly, only the lateral outer contour of the container is determined via the blow mold halves, whereas the base is designed via a separate base part. According to such an embodiment, the cavity for receiving the preforms is determined at least via the two blow mold halves and the base part. The base part is given away via a separate base drive device, which can also be designed as an electric drive analogous to the drive devices for the blow mold halves.

However, a particularly preferred embodiment provides that the ground drive device is cam-controlled. Accordingly, no need to separate synchronization between the other drive devices takes place. Alternatively, it is also conceivable to provide a pneumatic or hydraulic ground drive device. Starting from a pivotable base part, it is particularly preferably provided that the pivot axis is arranged obliquely, in particular perpendicular to the pivot axis of the blow mold halves.

The invention also relates to a blow molding system, wherein a plurality of blow molding units according to the invention are arranged in the circumferential direction on a transport gyro. Such a configuration corresponds to a usual blow molding system in the beverage industry, which has already been explained in detail in the introduction.

Accordingly, several identically designed blow molding units are arranged in the circumferential direction, which can be opened and/or closed independently of one another, the opening and closing process being based on the angular position of the blow molding unit on the transport circuit. All blow molds preferably have an identical design, so that a corresponding drive device designed as an electric drive and a toggle lever arrangement are then provided for each of the blow molds.

The invention furthermore relates to a method for forming a preform made of plastic into a container in a blow molding system according to the invention according to claim 15. Accordingly, a preform is first arranged at least in sections within the blow molding unit. Typically, a head area of the preforms protrudes from the blow mold. This head area already has an external thread for receiving a closure cap and does not require any plastic forming. In a subsequent closing step, the blow mold is then closed by moving, in particular pivoting, the blow mold halves relative to one another and then, in a deformation step, the interior of the preform is subjected to pressure by the blowing device.

In this context, it is particularly preferred if the closing step and the deformation step directly follow one another. This makes it clear that no additional locking step is required, which involves compression between the closing step and the deformation step Blow mold halves or the format parts within the blow mold halves relative to each other regardless of the closing movement.

It is also preferred if, in the closing step, the base part is moved relative to the blow mold halves, in particular pivoted, so that in the closing step the blow mold is closed by pivoting the blow mold halves relative to one another and the base part.

After the deformation step, the blow mold is then opened in an opening step by moving, in particular pivoting, the blow mold halves towards one another and the resulting container is then removed.

Starting from an embodiment in which the blow molds are arranged on a transport gyroscope, the preforms are moved along a transport direction during the closing step, the deformation step and / or the opening step, the transport direction preferably being arranged along a curved path, in particular a curved path designed as a circular segment.

The invention is explained in more detail below using an exemplary embodiment. Show it:

Fig. 1 shows a blow molding system according to the invention

Fig. 2 is a perspective view of a section of the blowing system according to the invention in an open state

Fig. 3 shows the detail according to Fig. 1 in a closed state

4A, 4B schematic representations of the section according to FIGS. 1, 2 in a top view.

Fig. 1 shows a schematic representation of a blowing system according to the invention. Here, containers 18 are first fed to a separating star 18 via a feed 13 and then transferred to a heating device 15. In the heating device 15, the containers 18 are heated to a temperature which enables plastic deformation. The containers 18 are then transferred into a blow molding unit 1 via a gripper arrangement 16 introduced, with a plurality of blow molding units 1 being arranged on a rotatably driven carrier 17 in the circumferential direction.

Fig. 2 shows a section of the blow molding unit 1 according to the invention in a perspective view. Accordingly, the blow mold is formed from a first and a second blow mold half 2, 3, which can be pivoted relative to one another to open and/or close the blow mold. The pivoting takes place according to the embodiment of FIG. 2 by pivoting along the pivot axis S, with only the first blow mold half 2 being designed to be pivotable, while the second blow mold half 3 is arranged immovably within the device shown in FIG. Accordingly, opening and/or closing is effected solely by pivoting the first blow mold half 2.

To pivot the first blow mold half 2, a drive device 4 is provided, which is designed as an electric drive. In particular, the example shown in FIG. 2 is an electric drive designed as a servo motor. This electric drive has an axis of rotation D, via which the blow mold can be opened and/or closed.

During the blowing process, a preform is arranged within the blow mold and then the blow mold is closed via the drive device 4 by pivoting the first blow mold half 2. During the actual blowing process, which leads to plastic deformation of the preform, it is necessary that the gap between the blow mold halves 2,

3 is reduced to a minimum.

2, the blow mold halves 2, 3 each have blow mold carriers 11, 12 as well as format parts 5, 6 arranged within the blow mold carriers 11, 12, which rest against one another in a closed state. This becomes clear in particular with reference to FIG. 3, which shows the blow molding unit 1 in a closed state.

In order to enable sufficient compressive forces for a tumbler, which presses the two molded parts 5, 6 together with a sufficient compressive force, a toggle lever arrangement 7 is provided, which is controlled by the drive device

4 generated torque amplified, so that from the outside in a sufficient A compressive force is exerted on the blow mold carriers 11, 12 and thus on the blow mold halves 2, 3, which is transferred accordingly to the mold parts 5, 6 and leads to a small gap between the format parts and 5, 6. A separate locking device is therefore not required, so that the format parts 5, 6 can be fixed within the blow mold halves 2, 3. A relative adjustment within the blow mold halves 2, 3 is not necessary.

2 and 3 it can also be seen that the blow mold 1 also has a so-called base part 8, which is arranged to be pivotable relative to the first and second blow mold halves 2, 3 and the blow mold also requires the base part 8 to be pivoted. This base part 8 is pivotally driven via a base drive device, not shown, this base drive device being designed to be cam-controlled separately from the drive devices of the blow mold halves.

The function of the toggle lever arrangement 7 is particularly clear from FIGS. 4A and 4B, with FIG. 4A showing a schematic representation of the blow molding system in an open state and FIG. 4B in a closed state. The toggle lever arrangement 7 has a first pivotable lever arm 9, 10 connected to the first blow mold half 2 and a second lever arm 9, 10 connected to the drive devices 4, the first lever arm 9 being connected to the first blow mold half 2 via a first axis of rotation R1 and with a second axis of rotation R2 the second lever arm 10 is articulated. Accordingly, the first and second lever arms 9, 10 are also pivotally connected to one another. The second lever arm 10 connects directly to the drive shaft of the drive device 4 in a rotation axis D, so that rotation of the drive shaft causes the second lever arm 10 to pivot.

To close the blow molding unit 1, the second lever arm 10 rotates along the arrow direction shown in FIG. 4A until the two format parts 5, 6 abut each other according to FIG. 4B. In the closed position, the two lever arms 9, 10 form an angle between 150 and 179°, which lies in front of the dead center of the toggle lever arrangement 7. This dead center is shown in Fig. 3B by the direct connecting line between the rotation axis R1 and the rotation axis D. Accordingly, at the dead center, all three axes R1, R2 and D would lie on a line or the first and second lever arms 9, 10 would lie on one Include an angle of 180°. Through a design in which the When the blow molding unit 1 is in the closed state before the dead center of the toggle lever arrangement 7, particularly high compressive forces can act on the first blow mold half, so that the two mold parts 5, 6 are pressed together with as little gap as possible.

The first lever arm 9 is preferably longer than the second lever arm 10. The force acting on the blow mold 1 by the toggle lever arrangement 7 is preferably between 30,000N and 100,000N in the closed state. 4A shows that the blow mold halves 2, 3 can be pivoted between the open state and the closed state over an angle between 0° and 90°.

Claims

Patent claims

1. Blow molding unit (1) for a blow molding system for forming plastic preforms into containers with at least one blow mold and a blowing device assigned to the blow mold, the blow mold being formed at least from a first and a second blow mold half (2, 3) and at least one the blow mold halves (2, 3) for opening and/or closing the blow mold is coupled via a drive device (4) designed as an electric drive, characterized in that the drive device (4) is applied via a toggle lever arrangement (7) at least to the first blow mold half (2 ) acts, with a closed state of the blow mold (1) being before a dead center of the toggle lever arrangement (7).

2. Blow molding unit (1) according to claim 1, characterized in that the blow mold halves (2, 3) can be pivoted relative to one another between the closed state and an open state.

3. Blow molding unit (1) according to claim 2, characterized in that the first and second blow mold halves (2, 3) are designed to be pivotable.

4. Blow molding unit (1) according to claim 1 or 2, characterized in that the second blow mold half (3) is designed to be immovable.

5. Blow molding unit (1) according to claim 1 or 2, characterized in that the electric drive is a servo motor.

6. Blow molding unit (1) according to one of claims 1 to 5, characterized in that the blow mold halves (2, 3) each have a blow mold carrier (11, 12) and a molded part (5, 6) assigned to the blow mold carrier (11, 12). , wherein the molded parts (2, 3) in a closed state form a cavity for receiving a preform.

7. Blow molding unit (1) according to claim 6, characterized in that the mold parts (5, 6) are arranged immovably within the blow mold carrier (11, 12).

8. Blow molding unit (1) according to one of claims 1 to 7, characterized in that the toggle lever arrangement (7) has a first lever arm (9, 10) which is pivotally movable to the blow mold and a second lever arm (9, 10) connected to the drive device (4), the first and the second lever arm (9, 10) are pivotally connected to one another and wherein the lever arms (9, 10) enclose an angle between 150 and 179 ° in the closed state.

9. Blow molding unit (1) according to claim 8, characterized in that the ratio between the length of the first and second lever arms (9, 10) is between 1 and 4.

10. Blow molding unit (1) according to one of claims 1 to 9, characterized in that the force acting on the blow mold by the toggle lever arrangement (7) is between 30,000N and 100,000N in the closed state.

11. Blow molding unit (1) according to one of claims 2 to 10, characterized in that the blow mold halves (2, 3) can be pivoted between the opening state and the closed state over an angle between 0° and 90°.

12. Blow molding unit (1) according to one of claims 1 to 11, characterized in that the blow mold has a base part (8) which is movable relative to the blow mold halves (2, 3) via a base drive device.

13. Blow molding unit (1) according to claim 12, characterized in that the ground drive device is cam-controlled.

14. Blow molding system with a plurality of blow molding units (1) according to one of claims 1 to 13, wherein the blow molding units (1) are arranged in the circumferential direction on a transport gyro.

15. A method for forming a plastic preform into a container in a blow molding system according to one of claims 1 to 14,

- wherein a preform is arranged at least in sections within the blow molding unit (1),

- The blow molding unit (1) passes through in a closing step

Moving the blow mold halves (2, 3) towards each other are closed,

- The blowing device then applies pressure to an interior of the preform in a deformation step.

16. The method according to claim 15, wherein the closing step and the deformation step immediately follow one another.

17. The method according to claim 14 or 15, wherein in the closing step the base part (8) is moved relative to the blow mold halves (2, 3).