Device and method for forming plastic preforms into plastic containers with control of the pressure rise time

Description

[0001] The present invention relates to a device and a method for forming plastic preforms into plastic containers. Such devices and methods have long been known in the prior art. The forming device, and in particular a blow molding machine or stretch blow molding machine, has several forming stations with blow molding devices that form a cavity corresponding to the negative shape of the plastic container to be produced. The plastic preforms are usually stretched longitudinally within the blow molding devices using a stretching rod and then formed into the plastic containers by exposure to a flowable medium. The flowable medium is applied in several different pressure stages with different pressure levels.Such devices and methods are also known, for example, from EP 2 722 153 A1, EP 1 175 990 A1, EP 1 974 892 A2 or WO 2007 / 077241 A2.

[0002] From the applicant's internal prior art, it is known to subject the plastic preforms or plastic containers to three pressure stages (P1, Pi, P2), two of which are preferably supplied fully or partially with recycled air (P1 and Pi). More recently, a further (intermediate blow) pressure stage (Pi2) has been added. This can also be supplied with recycled air. With the introduction of this additional intermediate blow stage, various machine inputs were changed. The applicant's internal prior art provides for a so-called slider which defines the (time) proportion for the intermediate blow molding in the molding phase (intermediate blow molding and final blow molding). Other input options such as input fields or similar would also be conceivable.The shorter the pressure rise time for the intermediate blow molding stage(s), the sooner the plastic preforms can be subjected to the final blow molding pressure, which is particularly advantageous for demanding or complicated container shapes. On the other hand, however, the longer the pressure rise time for the intermediate blow molding stage(s), the higher the amount of compressed air that can be recycled, with a saturation state occurring at a certain, unpredictable point. Depending on the application, it may not be possible to maximize the recycling potential while simultaneously achieving the required container quality.

[0003] In addition, the ideal slider position must be manually determined by the operator. To do this, the operator must visually assess the container quality and, if the compressed air recovery still offers "reserves," can further increase the pressure rise time for the intermediate blowing stage(s) to optimize air consumption. This process is repeated until either saturation is reached or the container quality reaches its lower limit.

[0004] This procedure is very error-prone and time-consuming, and consistent container quality cannot be guaranteed for different batches, as the slider must be reset each time. The respective setting also depends on the currently responsible operator and is therefore not reproducible.

[0005] The present invention is therefore based on the object of providing a device and a method that enables automatic adjustment or control of the pressure rise time. This object is achieved according to the invention by the subject matter of the independent claims. Advantageous embodiments and further developments are the subject matter of the dependent claims.

[0006] The invention is therefore directed to a device for forming plastic preforms into plastic containers, comprising a transport device which transports the plastic preforms to be formed along a predetermined transport path, wherein the transport device has a rotatable transport carrier on which a plurality of forming stations are arranged, each having a blow molding device within which the plastic preforms can be formed into the plastic containers, wherein the forming stations each have an application device which applies a flowable medium and in particular compressed air to the plastic preforms, wherein the application device applies a pre-blow pressure, at least one and preferably two intermediate blow pressures and a final blow pressure to the plastic preforms.Furthermore, the device comprises a control device suitable and intended for controlling the duration of a pressure rise time of at least one intermediate blowing pressure. It is also preferably conceivable for the plastic preforms to be subjected to more than two intermediate blowing pressures, and thus preferably to n intermediate blowing pressures (Pi1, Pi2, Pi3, etc.).

[0007] According to the invention, the device comprises a detection device which is suitable and intended to detect at least one value characteristic of the plastic container, wherein the duration of the pressure rise time of at least one intermediate blow-molding pressure can be regulated depending on this value characteristic of the plastic container. The duration of the pressure rise time is preferably automatically regulated depending on the value characteristic of the plastic container. The pressure rise time of the intermediate blow-molding pressure is the period of time during which the plastic container is subjected to the intermediate blow-molding pressure(s). The shorter this time, the sooner the application of the final blow-molding pressure can begin. However, the higher this time, the more compressed air can be recycled and used for the next forming process.

[0008] It is therefore proposed that an optimal setting for the pressure rise time of the intermediate blowing pressure be determined using a detection device, such as an image recording device, which may already be present in existing systems, and that the control system be controlled (fully) automatically accordingly. This optimal setting enables high-quality plastic containers with the lowest possible compressed air consumption.

[0009] In principle, the system aims for the pressure rise time at which the so-called effectiveness (the calculated value displayed on the operator terminal (HMI) that reports the efficiency of air recovery (compressed air recycling) in both intermediate blowing stages) just reaches 100%. However, once the container quality falls below a critical level, the controller value may no longer increase, meaning the pressure rise time may not be increased further, even if optimal recycling has not yet been achieved. Container quality therefore takes priority over the recycling quantity.

[0010] It is therefore advantageous to find the point or setting between good container quality with the shortest possible pressure rise time and minimal compressed air consumption, preferably automatically.

[0011] For this purpose, as described above, a characteristic value of the plastic container and preferably of a plastic container formed with the device is determined.

[0012] The characteristic value is then transmitted to an evaluation unit, which uses this to determine the quality of the plastic container. If the container quality is good, the control unit is preferably controlled or adjusted in such a way that it reduces the pressure rise time. If the container quality is poor, the control unit is preferably controlled or adjusted in such a way that it increases the pressure rise time. This process can be repeated until sufficient container quality is achieved with the lowest possible compressed air consumption. Advantageously, the control unit settings can be saved in a memory device, along with the relevant values for the pressure rise time and characteristic values for the container quality. These saved values can then be selected the next time this container type is manufactured.

[0013] The control device therefore preferably controls the duration of the pressure rise time, i.e. the time duration for which the plastic container is subjected to the intermediate blowing pressure.

[0014] In a preferred embodiment, the device therefore comprises an evaluation device that is suitable and intended to evaluate and / or assess the at least one characteristic value detected for the plastic container by the detection device in such a way that a conclusion can be drawn about the quality of the plastic containers. Accordingly, a control loop is preferably conceivable in which the detection device and / or the evaluation device evaluates the bottle quality, for example, clouding of the bottle sidewall or bottle bottom, in each case caused by stress whitening.

[0015] In a further preferred embodiment, the evaluation device is suitable and intended to compare the at least one characteristic value for the plastic container detected by the detection device with predetermined and / or stored values. Preferably, an actual value (detected characteristic value) is compared with a target value (stored value). The at least one characteristic value for the plastic container detected by the detection device or the actual value is preferably compared with a predetermined and / or stored range, in particular whether the characteristic value lies within a predetermined range. The characteristic value can be, for example, a surface quality (color, turbidity, roughness) of the plastic container, a diameter or other dimensions of the container, or the like.

[0016] The device therefore preferably has a memory device in which a plurality of predetermined values and / or ranges characteristic of the plastic container are stored. The characteristic value can preferably also be an image or an image characteristic of the plastic container. In this case, the detection device is preferably an image recording device, such as a camera, which detects or records an image of the plastic container. The predetermined values and / or ranges can preferably be parameters predetermined for the finished plastic container, which were selected or entered by the operator at an operating terminal. The pressure rise time can preferably also be determined based on these parameters predetermined for the finished plastic container.

[0017] The storage device is therefore preferably also suitable and intended to store images and the evaluation device is intended to compare the characteristic image recorded by the detection device with images stored in the storage device.

[0018] In a preferred embodiment, the recorded values are compared with target values, which are preferably stored in a cloud (big data). The cloud can be fed with values from different machines of different customers.

[0019] As mentioned above, the control device is then adjusted depending on this characteristic value, which provides information about the quality of the plastic container, and in turn regulates the pressure rise time. In a preferred embodiment, the control device can be continuously adjusted between a minimum and a maximum value for the pressure rise time. The minimum and maximum values for the pressure rise time are fixedly predetermined by the device. The control device preferably comprises a slide control on a graphical user interface, such as an operating terminal of the device. Previously, it was necessary to adjust this or its position manually. The invention now proposes to automatically adjust or regulate the position of the slide control depending on the container quality.

[0020] The evaluation device can preferably also be an AI (artificial intelligence) or a computing unit, which evaluates and assesses the characteristic value and controls or adjusts the control device accordingly. The AI or computing unit can be connected locally to the device. However, the AI or computing unit is preferably connected wirelessly to the device. An artificial neural network is particularly preferably used as the AI, which has been trained using supervised learning in order to teach the system the desired adaptations in the event of process fluctuations. A specific result is specified for the various input options. Based on the constant comparison between the target and actual result, the network learns to link the neurons appropriately. However, it would also be possible to train the artificial neural network using unsupervised learning, reinforcement learning, or stochastic learning.

[0021] The plastic container is subjected to pressure in a pre-blowing phase and a molding phase, wherein the plastic container is subjected to the pre-blowing pressure in the pre-blowing phase and to at least one and preferably two intermediate blowing pressures and the final blowing pressure in the molding phase.

[0022] The plastic containers are subjected to the pre-blowing pressure for at least 100 ms, preferably at least 110 ms, and particularly preferably at least 115 ms. The plastic containers are preferably subjected to the at least one intermediate blowing pressure and the final blowing pressure for at least 250 ms, preferably at least 265 ms, and particularly preferably at least 280 ms. The start of the application of the final blowing pressure preferably depends on the pressure rise time of the intermediate blowing pressures.

[0023] In a preferred embodiment, the device has a valve arrangement which controls the application of the pre-blowing pressure, the at least one and preferably two intermediate blowing pressures and the final blowing pressure to the plastic containers.

[0024] The device for forming plastic preforms into plastic containers is, as mentioned above, preferably a blow molding device or a forming station. The blow molding devices are preferably designed in several parts and comprise two blow mold halves and a base mold. These blow mold halves are preferably detachably arranged on a mold carrier shell or on the blow mold carriers. The blow mold carriers are pivotable relative to one another to open and close the blow molding devices. Furthermore, the blow mold carrier has locking mechanisms to lock the mold halves against one another during the blow molding process.

[0025] The plastic preforms are preferably expanded into the plastic containers by applying compressed air. For this purpose, the device preferably comprises an application device and a blowing nozzle that can be placed against an opening of the plastic preforms in order to apply compressed air to the plastic preforms or to expand them using compressed air.

[0026] Particularly preferably, the application device and in particular the blowing piston and / or the blowing nozzle are movable in a longitudinal direction of the plastic container and / or movable towards the plastic container.

[0027] In an advantageous embodiment, the blow molding devices or the forming stations each have stretching rods that stretch the plastic preforms in their longitudinal direction. Particularly preferably, the blow molding machine or the carrier and the forming stations are arranged within a clean room, which separates the blow molding machine from a non-sterile environment. Drive devices for closing, locking, and / or opening the blow molds are preferably located outside the clean room.

[0028] The blow molding devices are preferably transported within the cleanroom, wherein the cleanroom is preferably defined by several walls. The cleanroom is preferably defined by at least one stationary wall and a wall moving relative to this stationary wall. For example, the transport carrier on which the blow molding devices are arranged can already have or form one of these walls, and in particular the moving wall. The cleanroom thereby separates the blow molding devices, in particular, from a non-sterile environment.

[0029] The present invention is further directed to a method for forming plastic preforms into plastic containers, wherein the plastic preforms to be formed are transported along a predetermined transport path, wherein a plurality of forming stations are arranged on a rotatable transport carrier, wherein the forming stations each have a blow molding device within which the plastic preforms are formed into the plastic containers, wherein the forming stations each have an application device which applies a flowable medium and in particular compressed air to the plastic preforms, wherein the application device applies a pre-blow pressure, at least one and preferably two intermediate blow pressures and a finished blow pressure to the plastic preforms, and a control device controls a temporal duration of a pressure rise time of at least one intermediate blow pressure.

[0030] According to the invention, at least one value characteristic of the plastic container is detected, wherein the duration of the pressure rise time of at least one intermediate blowing pressure is regulated as a function of this value characteristic of the plastic container.

[0031] It is therefore also proposed, on the process side, to determine an optimal setting of the pressure rise time of the intermediate blowing pressure and, in particular, to control the control device accordingly (fully) automatically depending on a value characteristic of the plastic container.

[0032] In a preferred method, the at least one characteristic value for the plastic container is compared with predetermined and / or stored values. The characteristic value can preferably also be an image characteristic of the plastic container or an image of the plastic container, in which case the characteristic image is compared with a stored image. The characteristic value or the characteristic image is preferably characteristic of a quality of the plastic container.

[0033] The device described above is in particular also designed and intended to carry out the described method, ie all features described for the device described above are also disclosed for the method described here and vice versa.

[0034] Further advantages and embodiments are shown in the attached drawings. They show: Fig. 1 shows a schematic representation of a device for forming plastic preforms into plastic containers; Fig. 2 shows a diagram of a blowing curve; and Fig. 3 shows an example of a setting for the forming process.

[0035] Figure 1 shows a device 1 for forming plastic preforms 10 into plastic containers 15. This device 1 has a rotatable support 22 on which a plurality of forming stations 4 are arranged. These individual forming stations 4 each have blow molding devices 82, which form a cavity in their interior for expanding the plastic preforms.

[0036] Reference numeral 84 denotes a pressurizing device used to expand the plastic preforms 10 in order to thereby expand them. Reference numeral 90 denotes a valve arrangement, such as a valve block, which preferably has a plurality of valves that control the application of different pressure levels to the plastic preforms.

[0037] In a preferred method, the plastic preforms are first subjected to a pre-blow pressure P1, then to at least one intermediate blow pressure Pi that is higher than the pre-blow pressure, and finally to a final blow pressure P2 that is higher than the intermediate blow pressure Pi. After the plastic containers have expanded, the pressures or compressed air are preferably returned from the container to the individual pressure reservoirs.

[0038] Reference numeral 88 denotes a stretching rod used to stretch the plastic preforms in their longitudinal direction, and reference numeral 30 denotes a stretching unit that controls the movement of the stretching rod. Preferably, all forming stations have such blow molds 82 and stretching rods 88. The number of these forming stations is preferably between 2 and 100, preferably between 4 and 60, and preferably between 6 and 40.

[0039] The plastic preforms 10 are fed to the device via a feed device 62, such as in particular but not exclusively a transport star, and the formed plastic containers 15 are transported away via a discharge device 64.

[0040] Reference numeral 7 denotes a pressure supply device, such as a compressor or a compressed air connection. The compressed air is conveyed via a first connecting line 72 to a rotary distributor 74 and from there, via a second connecting line 76, to the annular channel 2a.

[0041] In addition to this ring channel 2a shown, further ring channels are preferably provided, which are shown in Fig. 1 However, in the illustration shown, they are concealed by the annular channel 2a, for example, lying underneath. Preferably, several annular channels are arranged one above the other. Reference numeral 98 denotes a third connecting line, which delivers the compressed air to a forming station 4 or its valve arrangement 90. Preferably, each of the annular channels is connected to all forming stations via corresponding connecting lines.

[0042] Reference numeral 8 schematically denotes a clean room, which here is preferably annular and surrounds the transport path of the plastic preforms 10. A (geometric) rotation axis, relative to which the transport carrier is rotatable, is preferably arranged outside the clean room 8. The clean room is preferably sealed from the non-sterile environment by a sealing device, which preferably has at least two water locks.

[0043] Reference numeral 52 denotes a detection device for detecting a characteristic value, such as an image of the plastic container. This detection device can also be arranged at a location on the device 1. The detected characteristic value or the detected characteristic image is transmitted, as indicated by the dashed line, preferably wirelessly to an evaluation device 54, which evaluates the image in the manner described above or compares it with values stored in the storage device 55. Reference numeral 50 denotes a control device, such as a shift register in this case, which is adjusted according to the result of the evaluation.

[0044] The Figure 2shows a diagram of a blow molding curve 110. The reference symbol Vp denotes the pre-blow phase, during which the pre-blow pressure P1 is applied. The molding phase Ap is represented by the dashed lines, whereby the area within the solid line represents the application of the final blow molding pressure P2, and the area to the left of the solid line (between the solid and dashed lines) represents the application of the intermediate blow molding pressures Pi and Pi2. After the final blow molding pressure P2 has been applied, it is maintained for a certain time. The used compressed air is then recycled, and the container is relieved of pressure, which is represented by the falling curve. The reference symbol Rv denotes the course of the stretch rod.

[0045] Figure 3shows an example of a setting for the forming process. This is in particular an exemplary representation of the individual values on an operating terminal 100 of the device. In particular, the Figure 2 shown curve is shown.

[0046] As can be seen from the x-axis of the Figure 2 and the ad 105 of the Figure 3 As can be seen, the pre-blowing phase Vp starts at 230 ms and lasts 115 ms, so that the forming phase Ap starts at 345 ms, which in turn lasts 280 ms and thus ends at 625 ms.

[0047] Reference numeral 50 denotes the control device, such as a slider, which is movable as indicated by arrow A. This is set such that the intermediate blowing pressures Pi, Pi2 are applied for 90 ms, resulting in a process efficiency of 99%. Preferably, the position of this control device is automatically adjusted and adapted by the described method or device, in particular depending on a characteristic value and / or the quality of the plastic containers. List of reference symbols

[0048] 1 Device 2 Transport device 2a Ring channel 4 Forming stations 7 Pressure supply device 8 Clean room 10 Plastic preform 15 Plastic container 22 Transport carrier 30 Stretching unit 50 Control device 52 Detection device 54 Evaluation device 55 Storage device 62 Feed device 64 Discharge device 72 First connecting line 74 Rotary distributor 76 Second connecting line 82 Blow molding device 84 Pressure device 88 Stretching rod 90 Valve arrangement 98 Third connecting line 100 Operating terminal 105 Display 110 Blow curve progression APile ApForming phase VpPre-blow phase P1Pressure P1, pre-blow pressure PiPressure Pi, intermediate blow pressure Pi2Pressure Pi2, intermediate blow pressure P2Pressure P2, final blow pressure RvProgression of the stretch rod

Claims

1. An apparatus (1) for forming plastic preforms (10) into plastic containers (15) with a transport device (2) which transports the plastic preforms (10) to be formed along a predetermined transport path, wherein the transport device (2) has a rotatable transport carrier (22) on which a plurality of forming stations (4) are arranged which each have a blow molding device (82) within which the plastic preforms (10) can be formed into the plastic containers (15), wherein the forming stations (4) each have an application device (84) which applies the plastic preforms (10) with a flowable medium and in particular compressed air, wherein the application device applies the plastic preforms (10) with a pre-blowing pressure (P1), at least one and preferably two intermediate blowing pressures (Pi, Pi2) and a final blowing pressure (P2), and the apparatus has a regulating device (50) which is suitable and intended for regulating a duration of a pressure rise time of at least one intermediate blowing pressure (Pi, Pi2), characterized in that the apparatus (1) has a detection device (52) which is suitable and intended for detecting at least one value characteristic of the plastic container (15), wherein depending on this value characteristic of the plastic container (15), the duration of the pressure rise time of at least one intermediate blowing pressure (Pi, Pi2) can be regulated.

2. The apparatus (1) according to claim 1, characterized in that the apparatus (1) has an evaluation device (54) which is suitable and intended for evaluating and / or assessing the at least one characteristic value detected by the detection device (52) for the plastic container (15) in such a way that a conclusion can be drawn about the quality of the plastic containers (15).

3. The apparatus (1) according to claim 2, characterized in that the evaluation device (54) is suitable and intended to compare the at least one value characteristic of the plastic container (15) detected by the detection device (52) with predetermined and / or saved values.

4. The apparatus (1) according to claim 3, characterized in that the detected values are compared with target values which are preferably saved in a cloud.

5. The apparatus (1) according to claim 1, characterized in that the regulating device (50) is smoothly displaceable between a minimum value and a maximum value of the pressure rise time.

6. The apparatus (1) according to claim 1, characterized in that the detection device (52) is an image recording device such as a camera.

7. The apparatus (1) according to claim 1, characterized in that the apparatus (1) has a valve arrangement (90) which controls the application of the pre-blowing pressure (P1), the at least one and preferably two intermediate blowing pressures (Pi, Pi2), and the final blowing pressure (P2) to the plastic containers (15).

8. A method for forming plastic preforms (10) into plastic containers (15), wherein the plastic preforms (10) to be formed are transported along a predetermined transport path, wherein a plurality of forming stations (4) are arranged on a rotatable transport carrier (22), wherein the forming stations each have a blow molding device (82) within which the plastic preforms (10) are formed into the plastic containers (15), wherein the forming stations (4) each have an application device (84) which apply the plastic preforms (10) with a flowable medium and in particular compressed air, wherein the application device applies the plastic preforms (10) with a pre-blowing pressure (P1), at least one and preferably two intermediate blowing pressures (Pi, Pi2) and a final blowing pressure (P2), and a regulating device regulates a duration of a pressure rise time of at least one intermediate blowing pressure (Pi, Pi2), characterized in that at least one value characteristic of the plastic container (15) is detected, wherein depending on this value characteristic of the plastic container (15), the duration of the pressure rise time of at least one intermediate blowing pressure (Pi, Pi2) is regulated.

9. The method according to claim 8, characterized in that the at least one value characteristic of the plastic container (15) is compared with predetermined and / or saved values.