WO2022013179A1

WO2022013179A1 - Method for controlling a drive of a stretching rod of a device for producing containers

Info

Publication number: WO2022013179A1
Application number: PCT/EP2021/069391
Authority: WO
Inventors: Thorsten Herklotz; Werner Lesinski
Original assignee: Khs Gmbh
Priority date: 2020-07-15
Filing date: 2021-07-13
Publication date: 2022-01-20
Also published as: DE102020118662A1

Abstract

The invention relates to a method (100) for controlling a drive of a stretching rod of a device for producing containers from preforms made of a thermoplastic material, wherein, in an immersion phase, the stretching rod is introduced (102) by means of the drive into the thermally conditioned preform located in a container mould up to and without making contact with the preform tip, and, in a stretching phase, following contact with the preform tip, the stretching rod stretches (104) the preform in its axial direction (104), characterised in that, at least at the end of the immersion phase, the stretching rod has an immersion speed that is greater than the stretching speed at which the preform is stretched when contact is made with the preform tip in the stretching phase. The invention provides a method (100) and a device (10) which have reduced energy consumption and reduced heat loss during the stretching process.

Description

Method for controlling a drive of a stretch rod of a device for manufacturing containers

The invention relates to a method for controlling a drive of a stretch rod of a device for producing containers from preforms made of a thermoplastic material.

In the manufacture of containers from preforms made of thermoplastic material, the preforms are first thermally conditioned and then stretched within a mold to form a container. In the radial direction to the longitudinal axis of the preform, the stretching takes place by means of a pressurized fluid that is filled into the preform. The preform is stretched along the longitudinal axis of the preform by means of a stretching rod, e.g. B. is known from DE 102007008023 A1. For this purpose, after the preform has been placed in a mold, the stretching rod is inserted through the mouth of the preform into the preform and moved to the top of the preform. After hitting the crest, the further movement of the stretching rod along the longitudinal axis stretches the preform in the axial direction. During the stretching of the preform, the stretching rod has a stretching speed which is sufficient to deform the preform along the longitudinal axis by means of the stretching rod.

During the stretching process, the resistance of the stretched material results in a high level of heat loss in the drive of the stretch rod, so that the stretching process has a relatively high energy consumption. The motor must be designed accordingly for a suitable output in order to be able to carry out the movement of the stretching rod along the longitudinal axis when stretching the preform despite the heat loss.

The object of the invention is therefore to provide a method and a device which has reduced energy consumption and reduced heat loss during the stretching process. The object is solved by the features of the independent claims. Advantageous developments are the subject of the dependent claims and the following description.

In a method for controlling a drive of a stretching rod of a device for producing containers from preforms made of a thermoplastic material, the stretching rod being inserted by means of the drive in an immersion phase into the thermally conditioned preform arranged in a container mold up to and without contact with it preform tip is inserted and, after contact with the preform tip in a stretching phase, stretches the preform in its axial direction, the invention provides that the stretching rod, at least at the end of the immersion phase, has an immersion speed that is greater than a stretching speed at which the preform is Contact with the tip of the preform is stretched in the stretching phase.

According to the invention, after a thermally conditioned preform has been placed in a mold, the stretching rod dips into the preform through the mouth of the preform. In this so-called immersion phase, the stretch rod has an immersion speed at which the stretch rod is moved along the longitudinal axis through the preform. The immersion phase ends immediately before the stretch rod inside the preform makes contact with the preform tip. At this point at the latest, the stretching rod will have a plunge speed that is greater than the stretching speed. When the stretching rod comes into contact with the tip of the preform, the stretching phase begins, in which the preform is stretched axially. The transition between the immersion phase and the stretching phase causes the stretch rod to suddenly experience resistance against its direction of movement due to contact with the tip of the preform. When the stretch rod comes into contact with the tip of the preform, the stretch rod is therefore decelerated. Since the immersion speed is greater than the stretching speed, the deceleration of the stretching rod causes a reduction in speed, which at least initially exceeds the stretching speed. speed lies. In order to maintain the stretching speed, less energy has to be expended by the drive for accelerating the stretch rod. In the best case, the stretch rod still has the stretch speed after braking in the stretch phase, so that the drive does not have to accelerate the stretch rod to the stretch speed. The impact of the stretch rod on the preform tip is therefore used to initiate the stretching phase in order to use less or no additional energy for a new acceleration of the stretch rod at the start of the stretching phase. A sudden increase in the load of a drive of the stretch rod during the transition from the immersion phase to the stretching phase is thus avoided. In the best case, the energy required for the transition between the immersion phase and the stretching phase does not have to be made available during the transition. Instead, this energy is already made available in the immersion phase as additional kinetic energy of the stretch rod. This reduces the heat loss in a drive of the stretch rod, since the drive does not experience any sudden short-term increase in load at the beginning of the stretching phase. Furthermore, current peaks in the drive of the stretch rod are avoided.

According to one example, the immersion speed of the stretch rod required at the end of the immersion phase and a loss in speed of the stretch rod striking the preform can be determined or specified. If the required immersion speed is determined, a sensor can be used. A corresponding differential speed of the stretch rod can be determined from the speed loss. The required immersion speed can then be selected at least as the sum of the stretching speed and the differential speed.

In a further example, the immersion speed of the stretch rod can be constant at least temporarily in the immersion phase.

The stretch rod can already be increased at the beginning or in the middle of the immersion phase to the required immersion speed that the stretch rod should have at the end of the immersion phase. The stretching rod can then be moved at a constant speed until the end of the immersion phase.

Furthermore, the immersion speed of the stretch rod in the immersion phase can be increased or reduced at least temporarily, for example.

For example, the stretching rod can already be accelerated at the beginning of the immersion phase and during the remaining immersion phase it can be decelerated to the required immersion speed at the end of the immersion phase, for example by friction or a brake. Alternatively, the stretch rod can be accelerated during the entire immersion phase in order to achieve the required immersion speed at the end of the immersion phase.

In a further example, the immersion speed can be a predefined speed, which is transmitted to the device for producing containers, in particular via a control device supplying the device with control signals, or by a user of the device.

The immersion speed can thus be set flexibly and adapted to the individual properties, e.g. B. the stretching rod, the preforms and/or the device for producing the containers.

Alternatively or additionally, the required immersion speed of the stretch rod at the end of the immersion phase can be determined, for example, by means of a measuring device of the system for manufacturing containers.

In this way, the accuracy of the required immersion speed at the end of the immersion phase can be increased. This avoids the stretch rod drive having to accelerate the stretch rod during the transition to the stretching phase, despite the plunge speed that has been set. Furthermore, if the immersion speed is too high, ness is avoided, so that energy is saved and damage to the preform is avoided.

Furthermore, the immersion speed can, for example, be greater than the stretching speed by at least a predefined differential speed, the differential speed being based on a predefined stretching resistance of the preform arranged in the container mold.

The predefined stretch rate can be calculated from the known stretch resistance of the thermally conditioned material of the preform. Alternatively, the stretch rate can be read from a pre-existing table of stretch resistances of the preform material at specific temperatures.

The invention also relates to a device for controlling a drive of a stretch rod of a device for producing containers from preforms made of a thermoplastic material, the stretch rod being moved by means of the drive in an immersion phase into the thermally conditioned preform arranged in a container mold up to and including Contact is introduced to the preform tip and after contact with the preform tip in a stretching phase, the preform is stretched in its axial direction, with the invention providing that the device is designed to transmit control signals that instruct a stretch rod to be driven, the stretch rod at least at the end of the immersion phase, to an immersion speed that is greater than a stretching speed at which the preform is stretched when it comes into contact with the preform tip in the stretching phase.

Advantages and effects as well as further developments of the device result from the advantages and effects as well as further developments of the method described above. In order to avoid repetition, reference is made to the previous description in this respect. The invention also relates to a system for producing containers from preforms made of a thermoplastic material, comprising a device as described above, a stretching rod with a drive that is connected to the device via a signal connection, and a container mold for receiving and forming of a preform, the stretching rod being able to be inserted into the container mold by means of the drive in order to stretch a preform arranged in the container mould.

Advantages and effects as well as further developments of the system result from the advantages and effects as well as further developments of the device described above. In order to avoid repetition, reference is therefore made to the previous description in this regard.

The invention is described below using an exemplary embodiment with the accompanying drawing. Show it:

Figure 1 is a flow chart of the method for controlling a

driving a stretching rod;

Figure 2 is a schematic representation of a device for

Manufacture of containers; and

FIG. 3a-c shows a schematic cross-sectional view of a container shape with a stretching rod

The method for controlling a drive is shown as a flow chart in FIG.

The method 100 is used to control a drive of a stretch rod of a device for producing containers from preforms made of a thermoplastic material. The stretching rod can be moved into a thermally conditioned preform, which is arranged in a container shape, by means of the drive to be controlled. net is. The container mold serves as a mold for forming the preform into a container.

In a step 102, the stretching rod is inserted through the preform mouth into the preform at a plunge speed. The immersion phase begins as soon as the stretch rod enters the preform. The movement of the stretching rod takes place up to the front of the preform ling peak of the preform, with no contact being made with the preforming peak.

The immersion phase ends when the stretch rod contacts the preform tip. After the stretching rod has come into contact with the tip of the preform, the stretching phase of the preform begins in step 104, in which the preform is stretched in the axial direction by the stretching rod.

In the stretching phase, the stretch rod has a stretching speed. The stretching speed is measured at least in such a way that the resistance which the stretched thermoplastic material opposes to the movement of the stretch rod is overcome.

The immersion speed, which the stretch rod has at the end of the immersion phase just before it comes into contact with the tip of the preform, is greater than the stretching speed. The transition from the immersion speed to the stretching speed takes place when the stretch rod comes into contact with the tip of the preform. At the moment of contact, the stretch rod is slowed down by the sudden resistance of the thermoplastic material. After the deceleration, the stretching rod continues to move in the axial direction of the preform at the stretching speed.

The stretching speed and the immersion speed can be specified for the drive by a target value for the speed of the stretch rod. The drive can be designed to regulate the speed of the stretch rod to the target speed. Before the stretch rod comes into contact with the tip of the preform, the Target value must be set to the plunge speed. At the moment the stretch rod comes into contact with the preform tip, the target value for the speed of the stretch rod can be set from the immersion speed to the stretching speed. The lowering of the desired value from the immersion speed to the stretching speed can also take into account the decelerating effect of the stretching rod hitting the preform tip. When the tip of the stretch rod hits the tip of the preform, the drive will therefore not generate any peak loads. The position of the preform tip can be entered manually or automatically recorded and/or calculated.

The differential speed between the stretching speed and the immersion speed can be a predefined differential speed. The predefined differential speed can be determined from the predefined stretching resistance of the preform placed in the container mold. Another parameter can be the mass of the stretching rod. The more parameters are used, the more precisely the differential speed can be predefined. The higher the accuracy of the predefined differential speed, the less energy is required to accelerate the stretch rod in the immersion phase. A buffer speed can be added to the predefined differential speed. The deceleration when hitting the preform tip then causes a speed reduction that is smaller than the sum of the predefined differential speed and the buffer speed. This ensures that the stretching speed is reached after deceleration without the stretch rod being accelerated by the drive.

However, it is also conceivable that the speed loss is greater than the differential speed and possibly greater than the sum of the differential speed and the buffer speed. In this case, the stretching rod must be accelerated by means of the drive during the transition between the immersion phase and the stretching phase. Al lerdings this acceleration then falls less than in the known Prior art, since the immersion speed according to the invention is greater than the stretching speed.

The immersion speed can be constant at least temporarily. For example, at the beginning of the immersion phase, it can be accelerated to the immersion speed required at the end and, once the required immersion speed has been reached, it can be moved further at a constant speed until the end of the immersion phase. Alternatively or additionally, the immersion speed of the stretch rod can be reduced at least temporarily. The stretching rod can be accelerated to a higher speed than the required immersion speed during the immersion phase. Before making contact with the tip of the preform, the stretch rod can be slowed down to the required immersion speed. Alternatively, the stretching rod can be inserted slowly into the preform and accelerated to the required immersion speed just before contact with the tip of the preform.

Before step 102, in an optional step 106, a predefined speed can be transmitted to the drive as the immersion speed. The immersion speed can be transmitted to the drive by means of a control device via control signals. Alternatively or additionally, the immersion speed can be specified by a user of the device.

The predefined speed can have a constant speed or a dynamic speed profile.

FIG. 2 shows a device for producing containers, which is referenced in its entirety with the reference numeral 30.

The device 30 includes a plurality of container molds 16, which serve as a mold. With the container molds 16, preforms can be formed into containers. Each of the container molds 16 can have a stretching rod 14 which can be inserted into the container mold 16 via a drive 12 . Each drive 12 can have a ne signal connection 32 with a device 10 for controlling the drive to be connected. The device 10 can also be referred to as a control device.

The signal connection 32 can be a cable connection or a wireless connection. Via the signal connection 32, control signals are transmitted from the device 10 to the drives 12 connected to it in signaling terms. An immersion speed can be transmitted as a constant speed or as a speed profile over the entire immersion phase. A stretching speed can also be transmitted.

In FIGS. 3a to 3c, the immersion of a stretching rod 14 into a thermally conditioned preform 18, which is arranged in a container mold 16, is shown in a cross-sectional view. The container shape 16 can be made in several parts and have a base piece 17, for example.

In Figure 3a, the stretch rod 14 is arranged outside of the preform 18 at. The preform 18 can be mounted with a neck ring 23 on the container mold 16 Be. The preform mouth 22 can be arranged outside of the container mold 16 . The preform dome 20 and the area of the preform 18 between the preform dome 20 and the neck ring 23 are net angeord within the container mold 16 .

The length of the preform 18 between the preform mouth 22 and the preform tip 20 is the immersion length 26. When the stretch rod 14 moves within the preform 18 along the immersion length 26, the stretch rod 14 is in the immersion phase.

The distance between the preform tip 20 and the bottom piece 17 is the stretching distance 28. When the stretching rod 14 moves along the stretching distance 28, the stretching rod 14 is in the stretching phase. In FIG. 3b, the stretching rod 14 has dipped through the preform mouth 22 into the preform 18 and is in contact with the preform tip 20 or is about to come into contact with the preform tip 20. The stretching rod 14 has therefore already passed the immersion phase. At this time, the stretch rod 14 has the immersion speed which is greater than the stretching speed. During a further movement in the axial direction, the stretching rod 14 is slowed down by the stretched material of the preform 18 by the immersion speed. The stretch rod 14 can speed up to the Reckge or be further decelerated. If the stretch rod 14 is further decelerated, the drive 12 accelerates the stretch rod 14 again to the stretching speed.

In FIG. 3c, the stretching rod 14 has run through the stretching phase and has stretched the preform 18 down to the base piece 17. The preform tip 20 can be in contact with the base piece 17 . Alternatively, the preform tip 20 can have been arranged just in front of the base piece 17 by the stretching rod 14 .

The drive 12 can also have a brake 24 in order, on the one hand, to reduce an excessive speed of the stretching rod 14 and, on the other hand, to reduce the stretching speed before the stretching rod 14 hits the base piece 17 .

Reference List

10 device for controlling a drive 12 drive 14 stretch rod

16 container shape

17 ground piece

18 preform

20 preform dome

22 preform mouth

23 neck ring

24 brake

26 dipping section 28 stretching section

30 device for manufacturing containers 32 signal connection

Claims

Expectations

1. Method for controlling a drive of a stretch rod of a device for producing containers from preforms made of a thermoplastic material, wherein the stretch rod is moved by means of the drive in an immersion phase into the thermally conditioned preform arranged in a container mold up to and without contact whose preform tip is introduced (102) and, after contact with the preform tip in a stretching phase, stretches the preform in its axial direction (104), characterized in that the stretching rod, at least at the end of the immersion phase, has an immersion speed that is greater than a stretching speed , with which the preform is stretched on contact with the preform tip in the stretching phase.

2. The method according to claim 1, characterized in that the immersion speed of the stretch rod in the immersion phase is at least temporarily constant.

3. The method according to claim 1 or 2, characterized in that the immersion speed of the stretch rod is at least temporarily increased or reduced in the immersion phase.

4. The method according to any one of claims 1 to 3, characterized in that the immersion speed is a predefined speed, which is transmitted (106) to the device for producing containers, in particular via a control device supplying the device with control signals, or by a user of the device.

5. The method according to any one of claims 1 to 4, characterized in that the immersion speed is greater than the stretching speed at least by a predefined differential speed, the predefined differential speed is based on a predefined stretching resistance of the preform placed in the container mold.

6. Device for controlling a drive (12) of a stretching rod (14) of a device (30) for producing containers from preforms (18) made of a thermoplastic material, the stretching rod (14) by means of the drive (12) in an immersion phase into the thermally conditioned preform (18) arranged in a container mold (16) up to and without contact with its preform tip (20) and after contact with the preform tip (20) stretches the preform ling (18) in its axial direction in a stretching phase stretches, characterized in that the device (10) is designed to transmit control signals which instruct the drive (12) of the stretch rod (14) to accelerate the stretch rod (14) to an immersion speed at least at the end of the immersion phase, which is greater than a stretching speed at which the preform (18) is stretched when it comes into contact with the preform tip (20) in the stretching phase.

7. System for producing containers from preforms (18) made of a thermoplastic material comprising a device (10) according to claim 6, a stretching rod (14) with a drive (12) which is connected to the device (10) via a signal connection and a container mold (16) for receiving and shaping a preform (18), the stretching rod (14) being inserted into the container mold (16) by means of the drive (12) for stretching a preform (18) arranged in the container mold (16). is insertable.