Apparatus and method for forming plastic containers from plastic parisons using a regulated pressurized air circulation

Abstract

Apparatus and method for forming a plastic container from a plastic parison using a regulated pressurized air cycle. In the method for forming a plastic container from a plastic parison, the plastic parison is inflated into a plastic container by applying a flowable medium, wherein the flowable medium is stored in a first pressure accumulator at a first pressure and in a second pressure accumulator at a second pressure which is higher than the first pressure, and wherein a first blow-molding pressure is applied to the plastic parison by a fluid connection between the first pressure accumulator and the plastic parison, and a second blow-molding pressure is applied to the plastic parison by a fluid connection between the second pressure accumulator and the plastic parison, and wherein the flowable medium is at least temporarily returned to the first pressure accumulator, wherein a first characteristic value is set for the operation of applying the flowable medium to the plastic parison, characterized in that a second value is determined in consideration of the first value, which is a characteristic value of the point in time or the period of time at which the flowable medium is returned to the first pressure accumulator.

Description

Technical Field

[0001] This invention relates to an apparatus and a method for forming plastic preforms into plastic containers. Background Technology

[0002] In the beverage manufacturing industry, it is well known that heated plastic preforms are shaped and, in particular, expanded into plastic containers. For this purpose, within a blow molding die, a flowable medium, typically pressurized air (but sometimes liquid), is used to expand the plastic preform into a container. A typical machine for performing these processes is a stretch blow molding machine.

[0003] In the prior art, for stretch blow molding machines used for container forming, different pressure levels are used, and a fluid connection with the container is established by means of valve configurations and, in particular, valve assemblies. Processes with two or three pressurization stages have been disclosed in the prior art. In the applicant's internal prior art, configurations with four pressure stages have also been validated. Air is typically used as the pressurized medium, but other gaseous fluids and liquids, such as beverages to be filled, can also be used.

[0004] The pressurization stage sometimes has four pressure levels. In the prior art, each pressure level is set by the machine operator. These (e.g., four) pressure levels are then sequentially connected to the container via valves located on valve units such as valve assemblies.

[0005] After maintaining the highest pressure for a certain period of time, the process is followed by a recycling phase. In the following text, the recycling phase refers to the phase in which the flowable medium (particularly from the container to be expanded) is returned to the accumulators (e.g., an annular channel).

[0006] During the recycling phase, valves for each pressure level are opened sequentially in descending order. The pressure in the container decreases to the corresponding pressure level for each level (and particularly in the corresponding accumulator), during which air mass flows from the container into the accumulator.

[0007] The valve opening time during the recycling phase determines the quality of air recycled. This assumes a pressure differential exists between the container and the accumulators at each stage. If the valve opening time is long enough to achieve complete pressure balance between the container and the corresponding accumulator, then extending the valve opening time will not increase the recycled quality. In the prior art, valve opening time is adjusted to achieve the pressure set by the operator in the accumulator as closely as possible.

[0008] In the existing technology, the starting time of each recycling cycle is set based on the characteristic container exhaust time of the corresponding machine and the valve opening time calculated by the regulating device.

[0009] The adjustment deviation detected by the regulating device is the difference between the nominal pressure and the actual pressure of the accumulator at the corresponding pressure level. In the applicant's prior art, some parameters of the blow molding profile are set by the operator, while others are determined by the machine itself.

[0010] For the pressurized air consumption of the corresponding equipment, the pressure in the container at the exhaust time is particularly important, because the pressure consumption of each container is calculated based on the exhaust pressure, container volume, and dead zone of the workstation.

[0011] One drawback of the current operating method is that the intermediate blow molding pressure is input by the user, meaning the cycle control unit can only find one optimal value for this input at most. This implies that although the corresponding accumulator pressure is reached, the exhaust pressure is much higher than the possible minimum exhaust pressure. This possible minimum exhaust pressure corresponds to the pressure of the lowest pressure stage in the booster.

[0012] Another drawback is that the cycle initiation time depends on the valve opening time. If the accumulator is fed back at an unfavorable time, such as when the accumulator pressure is at its highest value, the recycling potential is reduced. Another drawback of the current operating method is that the characteristic of extracting air from the accumulator during the boosting phase is not taken into account in the recycling process, thus leaving untapped recycling potential. Summary of the Invention

[0013] In view of this, the object of the present invention is to improve the energy efficiency of such devices and methods. In particular, the object is to improve the efficiency gains that can be achieved through pressurized air circulation.

[0014] In the method of molding a plastic preform into a plastic container according to the present invention, a plastic preform (preferably several plastic preforms) is expanded into a plastic container by applying a flowable, particularly gaseous, medium, and especially air. The flowable medium is stored in a first accumulator at a first pressure and in a second accumulator at a second pressure higher than the first pressure. A first blow molding pressure is applied to the plastic preform via a fluid connection between the first accumulator and the plastic preform, and a second blow molding pressure is applied to the plastic preform via a fluid connection between the second accumulator and the plastic preform. Preferably, the second blow molding pressure is applied after the first blow molding pressure is applied.

[0015] In addition, at least temporarily, a flowable medium (particularly pressurized air) (particularly from the plastic container) is fed back to the first accumulator, wherein a first characteristic value is preferably set for the operation of applying the flowable medium to the plastic preform.

[0016] In a first embodiment of the invention, a second value is determined taking into account the first characteristic value, which is a characteristic value of the time point or time period (and particularly the starting time point) at which the flowable medium is fed back to the first accumulator.

[0017] In the second method according to the invention, the time point and / or time period (and particularly the starting time point) for returning the flowable medium to the accumulator is selected and / or determined based on the time point and / or time period for applying the flowable medium to the plastic preform. In another method according to the invention, at least one time point and / or time period (and particularly the starting time point) for returning the medium to the first accumulator is determined based on the characteristic time point and / or time period (and particularly the starting time point) of the operation of applying pressure originating from the accumulator to the plastic preform.

[0018] The methods of the invention described herein can also be combined. Different methods can also be used for different pressure levels and / or accumulators, for example, the first of the above methods can be used for intermediate pressure Pi, and the second method can be used for intermediate pressure Pi+.

[0019] Preferably, at least two of the stated start time points are determined. Particularly preferably, the start time point is determined for the operation of returning the flowable medium to at least one accumulator for containing intermediate blow molding pressure.

[0020] Particularly preferably, the first characteristic value is set by the user, at least partially and preferably entirely. However, the first characteristic value can also be calculated by a machine controller. These values ​​can be determined, for example, based on the container to be manufactured. These values ​​can also be determined and / or measured based on the plastic preform to be expanded.

[0021] Particularly preferably, the plastic preform is transported along a predetermined transport path, during which the flowable medium is applied to the plastic preform. Particularly preferably, the flowable medium is applied to several plastic preforms at least partially simultaneously (or in at least partially overlapping time periods), thereby expanding these plastic preforms.

[0022] Through these two operating methods according to the invention, efficiency in blow molding air can be improved. In particular, it is possible to determine the (starting) point of air recirculation (hereinafter referred to as recycling).

[0023] In a preferred method, the first characteristic value is selected from the group consisting of: the magnitude of a first pressure (particularly a pre-blow pressure P1), the magnitude of a second pressure (particularly a first intermediate blow molding pressure Pi, preferably higher than the pre-blow pressure), the magnitude of a third pressure (particularly a second intermediate blow molding pressure Pi+, preferably higher than the first intermediate blow molding pressure Pi), the magnitude of a fourth pressure (particularly a final blow molding pressure P2), the start time of applying the first pressure, the start time of applying the second pressure, the start time of applying the third pressure, the start time of applying the fourth pressure, the duration of applying the first pressure, the duration of applying the second pressure, the duration of applying the third pressure, the duration of applying the fourth pressure, the end time of applying the first pressure, the end time of applying the second pressure, the end time of applying the third pressure, the end time of applying the fourth pressure, the start time of releasing (residual) pressure into the surrounding environment (exhaust), and the like.

[0024] Particularly preferably, these time points are controlled by the on / off time points of valves arranged on and preferably on each of several molding stations. Each duration or time point can be controlled by means of a corresponding valve or its on / off time point. An offset may also be added to take into account the valve response time.

[0025] Furthermore, values ​​can be controlled, such as the pressure level within the accumulator. Particularly preferably, at least one accumulator, and more preferably several accumulators, are implemented as an annular channel. Preferably, the accumulator is arranged on a movable carrier, and the forming station is also preferably arranged on this carrier.

[0026] In another preferred method, the plastic preform is transported along a predetermined (particularly circular) transport path, and preferably expands during this transport. Preferably, the plastic preform is fed into a blow molding die, and then the flowable medium is applied to it. The blow molding die can be opened, the plastic preform embedded into it, and then the blow molding die closed again. Particularly preferably, the plastic preform is elongated longitudinally. Particularly preferably, a tension rod is inserted into the interior of the plastic preform to achieve the above operation. Particularly preferably, the plastic preform is elongated in its stretching direction or longitudinally in a manner that is at least partially simultaneous with the application of different pressures.

[0027] Particularly preferably, the movement of the tension rod is controlled, taking into account at least one point in time when the plastic preform is first pressurized. This further optimizes the molding process.

[0028] Particularly preferably, at least three, preferably at least four different pressures or pressure levels are applied to the (preferably multiple) plastic preforms to expand them. Particularly preferably, the gaseous medium is circulated or fed back to at least two, preferably at least three, accumulators.

[0029] Particularly preferably, the expansion pressure is measured before and / or during pressurization of the plastic preform, and / or the circulation pressure is measured during the return of the flowable medium to the accumulator. Particularly preferably, the pressure of the gaseous medium within the container is measured at least temporarily and preferably continuously.

[0030] Particularly preferably, the pressure of the flowable medium is determined, at least temporarily and preferably continuously, within at least one accumulator, preferably several accumulators, and preferably all accumulators. Particularly preferably, these pressures are also used to control the corresponding points or periods of time for applying the flowable medium to the plastic preform and / or for returning the flowable medium to one or more accumulators (i.e., particularly for recycling).

[0031] Preferably, the first pressure or first pressure level is less than 12 bar, more preferably less than 10 bar, more preferably less than 8 bar, and particularly preferably less than 6 bar.

[0032] Preferably, the first pressure or first pressure level is greater than 2 bar, more preferably greater than 3 bar, and particularly preferably greater than 4 bar.

[0033] The invention or method described herein is based on different schemes for optimizing pressurized air consumption.

[0034] In terms of methodology, the starting time of the corresponding recycling branch, i.e., the time point for resupply to each accumulator, is calculated based on the starting time point of the corresponding pressure level in the pressurization phase. Accordingly, the starting time points of pressurization and recycling can be determined, for example, based on each other, and in particular, synchronized. This allows for simultaneous release from and delivery to the accumulator. Preferably, the following relationship applies to the starting time of resupply or recycling at a specific pressure level:

[0035] Cycle start time Px = boost start time Px + nx A.

[0036] Coefficient A is calculated as follows: 3600 / station efficiency [b / h / c] (bottles per hour per cavity) / number of stations. Variable n depends on different quality parameters of the container, such as the holding time for the highest pressure level, and thus also on the customer. It is preferable to calculate variable n based on operator input. Variable n is an integer multiple (1, 2, 3, and so on).

[0037] In another method, the pressure level difference between the pressure stages during pressurization and recycling is adjusted, particularly to a minimum. For this purpose, the pressure during pressurization and recycling, or during these stages, is measured. Preferably, the valve opening time of each intermediate blow molding pressure stage, especially during the pressurization stage, is used as the adjustment variable.

[0038] The initial pressure level can be set, for example by the machine operator, but it can also be set by the machine controller, or calculated or adjusted using artificial intelligence.

[0039] In a preferred method, this initial pressure level is preset or set using a (preferably automated) calculation method. Subsequently, it is preferable to stop supplying fresh air. The accumulator can be filled with only recirculated air. The pressure level in the accumulator is preferably achieved based on the conditions of the physical system.

[0040] Preferably, fresh air supply is prohibited for at least one accumulator, at least temporarily, especially during normal operation of the device.

[0041] The above operations are preferably performed individually for each single pressure level, and particularly preferably in a manner that proceeds from the highest intermediate blow molding pressure level to the lowest intermediate blow molding pressure level. These operations are then preferably iterated until, after a certain number of iterations, the pressure in the accumulator no longer changes significantly.

[0042] Preferably, the flowable medium is returned between several molding stations and their corresponding accumulators, and more preferably between all molding stations and their corresponding accumulators (preferably several accumulators).

[0043] Among these, the return feeds are preferably staggered in time between each workstation.

[0044] Particularly preferably, a value is determined taking into account the expansion pressure (i.e., the pressure applied when the plastic preform is pressurized) and the circulation pressure (i.e., the pressure present at the start of the recirculation time). More particularly, a comparative value is determined taking into account both the expansion pressure and the circulation pressure. And more particularly preferably, a second value (particularly the start time of the recycling or recirculation of the flowable medium) is determined taking into account this comparative value. This comparative value can be measured, particularly by means of two or more sensor devices, but it can also be determined based on the blow molding curve. This comparative value can be used as an adjustment variable for a regulator that adjusts the start time of the recirculation of the flowable medium.

[0045] In a preferred method, the comparison value is the difference and / or quotient of the expansion pressure and the circulation pressure, and the second value is adjusted in a manner that preferably minimizes this comparison value. Accordingly, for example, the difference between the expansion pressure and the circulation pressure can be measured, and (particularly by modifying the start time of recycling) this difference can be adjusted to a minimum.

[0046] A quotient can also be used. Specific coefficients, for example, determined by the user, can be set in the calculation. This allows the adjustment system to consider whether the comparison value is below a specific limit and make adjustments accordingly.

[0047] In a preferred method, for adjustment, the opening time of at least one valve is changed, and more preferably, the opening times of several valves are changed. Particularly preferred is the changing of the valve opening time of the valves controlling the intermediate blow molding pressure stages (Pi and / or Pi+). Particularly preferred is the changing of the opening times of several valves, especially those responsible for delivering different intermediate blow molding pressure stages. In another preferred method, the adjustment is iteratively adjusted or set to a specific minimum differential pressure.

[0048] Particularly preferably, the method is implemented for several pressure stages and / or several accumulators, and even more preferably, the method is implemented first for the higher pressure stages and then for the lower pressure stages.

[0049] In another advantageous method, at least one time point and / or time period for feeding back to the first accumulator is determined based on the characteristic time point and / or time period of the operation of applying pressure originating from the first accumulator to the plastic preform.

[0050] Similarly, at least one time point and / or time period for feeding back to the second accumulator can be determined based on the characteristic time point and / or time period of the operation of applying pressure from the second accumulator to the plastic preform.

[0051] In another preferred method, in order to determine the timing and / or time period for feeding back to the first accumulator, at least one parameter is taken into account, which is a characteristic parameter of the container to be expanded and / or a characteristic parameter of the duration for which another pressure level is applied.

[0052] Specifically, the starting time point for feeding back to the first and / or second accumulators is determined in the manner described above. Alternatively, the time point can be determined indirectly, for example, by the position of the molding station along its transport path. As mentioned above, the molding station is preferably transported on a rotatable carrier such as a blow molding wheel. Accordingly, the feeding back of the flowable medium to the corresponding accumulator can begin at a predetermined position along the transport path of the molding station.

[0053] Accordingly, for example, when the molding station is at a set angular position, such as 40°, pressurization can begin through the first accumulator, and when the molding station reaches another angular position, such as 150°, refeeding can begin accordingly.

[0054] In a preferred method, the time point, particularly the starting time point and / or time period, for feeding back to the first accumulator is determined, taking into account at least the characteristic parameters of the container to be expanded and / or the characteristic parameters of the duration of applying another pressure level. This allows the time and / or pressure duration of other pressure levels to be taken into account when determining the corresponding starting time point.

[0055] In addition, the duration of the first pressure (P1 pressure), intermediate pressure (PI), or final blow molding pressure (P2) can also be considered.

[0056] In another preferred method, at least one time point and / or time period for resupplying to the second accumulator is also determined based on the characteristic time point or time period (especially the starting time point) of the operation of applying pressure originating from the second accumulator to the plastic preform. In particular, the starting time point for resupplying the flowable medium is determined based on the starting time point of applying this pressure to the plastic preform.

[0057] In another preferred method, at least three, and preferably at least four, different pressure levels are applied to the plastic preform to achieve expansion. Particularly preferably, the highest pressure level is applied for the longest period of time.

[0058] In another preferred method, in order to determine the timing and / or time period for feeding back to the first accumulator, at least one parameter is taken into account, which is selected from a group of characteristic parameters of the number of molding stations or the efficiency of the molding stations.

[0059] In another preferred method, when setting the valve opening time for applying a flowable medium originating from at least one accumulator to the plastic preform, the valve opening time for returning the flowable medium to this accumulator (and / or related to it), and particularly corresponding to it, is determined. Particularly preferably, these valve opening times are matched to each other, or their deviation from each other is less than 20%, preferably less than 15%, preferably less than 10%, and preferably less than 5%. In a preferred method, the corresponding durations are controlled and, in particular, adjusted. However, these durations can also be set.

[0060] In another preferred method, in order to adjust the device, the opening time of at least one valve and / or the application duration is modified.

[0061] The present invention also relates to an apparatus for molding a plastic preform into a plastic container, having at least one molding station having an application device adapted and used to expand the plastic preform into a plastic container by applying a flowable medium. The apparatus further includes a first accumulator for storing the flowable medium at a first pressure, and a second accumulator for storing the flowable medium at a second pressure higher than the first pressure, and a first fluid connection is provided (and / or can be established) between the accumulators and the plastic preform to apply a first blow molding pressure to the plastic preform through this fluid connection between the first accumulator and the plastic preform.

[0062] Furthermore, a second fluid connection is provided (and / or can be established) between the second accumulator and the plastic preform to apply a second blow molding pressure to the plastic preform via this second fluid connection between the second accumulator and the plastic preform. Additionally, the flowable medium (particularly pressurized air) can be at least temporarily returned from the plastic container to the first accumulator, and preferably a control device is provided that sets a first characteristic value for the operation of applying the flowable medium to the plastic preform.

[0063] In the first technical solution of the present invention, the processor device determines a second value in consideration of the first characteristic value, the second value being a characteristic value of the time point or time period at which the flowable medium is fed back to the first accumulator, and particularly the starting time point.

[0064] In the second technical solution of the present invention, at least one time point and / or time period (and particularly the starting time point) for feeding back the flowable medium to the first accumulator can be determined based on the characteristic time point and / or time period of the operation of applying pressure from the accumulator to the plastic preform.

[0065] Therefore, both technical solutions propose that the parameters used for pressure return, and in particular the starting time points, are settable. In both cases, these times or time periods, and in particular one or more starting time points, are determined based on at least one characteristic value of the pressurization of the plastic preform.

[0066] Particularly preferably, the first characteristic value is selected from the group consisting of: a first pressure level (P1), a second pressure level, particularly a first intermediate blow molding pressure level (Pi), a third pressure level, particularly a second intermediate blow molding pressure level (Pi+), a fourth pressure level, particularly a final blow molding pressure level (P2), the time point and / or time period for applying the first pressure level, the time point or time period for applying the second pressure level, the time point or time period for applying the third pressure level, and the time point or time period for applying the fourth pressure level (final blow molding pressure). It should be noted that within the scope of this application, the concepts of "pressure" and "pressure level" have the same meaning.

[0067] Particularly preferably, the apparatus has several forming stations for shaping plastic preforms into plastic containers. Particularly preferably, each forming station has a blow nozzle that abuts against the plastic preform to apply blow molding pressure. Therefore, these nozzles preferably form part of the aforementioned application device. In another preferred embodiment, each forming station has a tension rod that can be inserted into the plastic preform to elongate it longitudinally.

[0068] In another advantageous embodiment, each of the molding stations has a control device that controls the application of different pressures or pressure levels to the plastic preform. Accordingly, valve configurations, such as valve assemblies, can be provided to control the application of different pressure levels to the plastic preform. Particularly preferably, at least one of these valve configurations, and preferably all valve configurations, have at least one valve, particularly a controllable valve, especially a proportional valve.

[0069] In another advantageous embodiment, the device has at least one sensor device adapted for and used to detect the pressure of the flowable medium in at least one accumulator and / or in the plastic container. Particularly preferably, at least one such sensor device is assigned to each of two accumulators, or possibly more than two accumulators. In addition, at least one sensor device adapted for and used to detect the pressure in the container to be expanded is also assigned to at least one, and preferably several, molding stations.

[0070] In another advantageous embodiment, the molding station has a valve configuration that enables the application of at least three, and preferably at least four, different pressure levels to the plastic preform. This control device or valve configuration may also be adapted and used to control the return flow of the flowable medium from the plastic preform to at least one, and preferably several, accumulators. Preferably, the valve used to apply a specific pressure level to the container is also adapted and used to cause the return flow of the flowable medium from the container to the corresponding accumulator.

[0071] In another advantageous embodiment, the device has a comparison device that compares the expansion pressure and / or the pressure applied to the plastic preform with the circulating pressure (particularly the pressure used to return the flowable medium to the accumulator), and particularly preferably outputs at least one characteristic value of this comparison. In a preferred method, the pressure return can be controlled and / or regulated with reference to this comparison value, and particularly the aforementioned starting time point can be controlled and / or regulated. This enables a very resource-efficient device.

[0072] In another advantageous embodiment, the molding station has a valve configuration that controls the application of a flowable medium to the plastic preform and / or the return of the flowable medium to at least one accumulator, wherein control is preferably performed with at least part of taking into account characteristic values ​​of the comparison between expansion pressure and circulation pressure. Particularly preferably, this mode of operation can be used for several molding stations, and even more preferably for all molding stations.

[0073] Preferably, the flowable medium can also be fed back from the plastic container to be expanded to the second accumulator. Particularly preferably, the flowable medium is capable of being fed back from the plastic container to be expanded to all accumulators, especially except for the accumulator that maintains the highest pressure (i.e., particularly the final blow molding pressure).

[0074] In another advantageous embodiment, the device has a processor adapted and configured to determine the start time for feeding the flowable medium back to the Xth accumulator, preferably taking into account the pressurization start time of the plastic preform and / or the total number of molding stations.

[0075] These measures minimize the pressurized air consumption of the device. The applicant unexpectedly discovered that air consumption largely depends on the pre-blow pressure level, bottle volume, and dead zone. The final blow molding pressure (when using at least four pressure levels) is only a secondary factor.

[0076] In another preferred embodiment, the device has a control mechanism and, in particular, an adjustment mechanism, which controls and, in particular, adjusts the operation to apply different pressure levels to each accumulator. Here, for example, a so-called dome pressure regulator can be used.

[0077] At least the accumulator that accommodates the highest pressure (especially the final blow molding pressure) has such a control device.

[0078] Preferably, the device has a distribution device and, in particular, a rotary distributor that distributes a flowable medium (in particular pressurized air) from a pressure source such as a compressor (in particular, a stationary arrangement) to the accumulator.

[0079] Preferably, the control or regulating device is arranged between the distribution device and at least one accumulator, and is particularly fluidly connected to both the accumulator and the distribution device.

[0080] In addition, it can reduce the complexity of the equipment for machine operators because the number of parameters to be set is reduced.

[0081] In addition, the size of the pressurized air source, such as the high-pressure compressor used to pressurize the equipment, can be reduced, and costs can also be lowered. Attached Figure Description

[0082] For more advantages and implementation methods, please refer to the accompanying drawings. Wherein:

[0083] Figure 1 This is a schematic diagram of the device of the present invention;

[0084] Figure 2 The pressure characteristic curves during the expansion process of the plastic preform are shown.

[0085] Figure 3 A diagram used to illustrate the starting time points;

[0086] Figure 4 for Figure 3 A magnified view of a portion of the illustration; and

[0087] Figure 5 The adjustments for each pressure level are shown. Detailed Implementation

[0088] Figure 1 An apparatus 1 for molding a plastic preform 10 into a plastic container 15 is shown. This apparatus has a rotatable carrier 12 on which several molding stations 20 are arranged. Each of these individual molding stations has a blow molding die 82 and an application device 84 for applying a flowable medium to the plastic preform 10, the medium being pressurized air for expanding the plastic preform.

[0089] Reference numeral 88 indicates a stretching rod for elongating the plastic preform along its longitudinal direction. Preferably, all molding stations have such a blow mold 82, application device, and stretching rod 88. Preferably, the number of these molding stations is between 2 and 100, more preferably between 4 and 60, and even more preferably between 6 and 40.

[0090] The plastic preform 10 is transported to the device via a first transport device 32 (particularly a conveyor star wheel, but not limited thereto). The plastic container 15 is transported out via a second transport device 34.

[0091] Reference numeral 7 indicates a pressure supply device, such as a compressor or pressurized air connector. Pressurized air is supplied to a rotary distributor 74 via a connecting line 72, and from this rotary distributor is supplied to an accumulator via another line 76, which in this context refers to an annular channel.

[0092] In addition to the annular channel 2a shown, it is preferable to also provide another annular channel, but it is in Figure 1 The view shown is obscured by the annular channel 2a, for example, positioned below. In addition, it is preferable to provide other connecting lines for pressurizing these additional accumulators.

[0093] Reference numeral 98 in the attached figure indicates a connecting line that releases pressurized air to molding station 20. Preferably, each of the annular channels is connected to all molding stations via a corresponding connecting line.

[0094] Reference numeral 14 indicates a sensor device for (preferably continuously) detecting the pressure within the accumulator. The additional (not shown) accumulator preferably also has such a sensor device or pressure measuring device.

[0095] Reference numeral 18 indicates a pressure measuring device adapted for and used to detect the pressure of the flowable medium within the container to be expanded.

[0096] Reference numeral 40 indicates a valve configuration, such as a valve assembly, for applying a flowable medium to the plastic preform and preferably also controlling its recycling in each accumulator. This valve configuration may have a processor (not shown) that controls the corresponding start time point for the return of the flowable medium. However, this processor may also be part of a (higher-level) machine controller.

[0097] Figure 2 The blow molding curve K is shown, reflecting the pressure characteristics over time during the expansion of the plastic preform. Section I represents the pressurization stage, and section III represents the recycling stage (i.e., specifically the stage where pressure is returned from the container to the accumulators). During the pressurization stage, several pressure levels are successively applied to the plastic preform, specifically four pressure levels. Stage II represents the final blow molding stage, during which the plastic preform has been formed but is maintained in this state by applying the final blow molding pressure.

[0098] Section IV represents the exhaust stage, in which the remaining pressurized air is expelled from the formed container into the surrounding environment.

[0099] Within section I, rising pressure is applied to the plastic preform by opening and closing the valves accordingly, thereby achieving molding. After final blow molding, the pressure is gradually released back from the container that underwent blow molding during this period.

[0100] Figure 3 The corresponding starting time points (solid points) for applying different pressure levels or pressures to the plastic preform are shown. Also shown are the corresponding starting time points (hollow circles) for returning the gaseous medium to the corresponding accumulator.

[0101] In the existing internal technology, these solid dots or their starting time points and the last starting time point (Exh_start) are set by the user, while the hollow circles or their corresponding starting time points are determined or calculated by the device itself.

[0102] The horizontal axis represents time in milliseconds (ms), and the vertical axis represents pressure in bars.

[0103] The vertical dashed lines indicate the respective starting time points t1 for applying the corresponding pressure level, or the respective starting time points t2 for transmitting the corresponding pressure level back. Within the scope of this invention, it is particularly proposed to determine the starting time point (t2) for transmission back.

[0104] Figure 4 For example Figure 3 The diagram shows an enlarged view of the blow molding curves, with particular emphasis on the points at pressure levels P+ and Pi. This reveals the blow molding curves with characteristic time points.

[0105] The measured pressure is also indicated by a horizontal line. The start time of the recycling phase is adjusted to minimize the pressure difference between the pressure during the application process and the pressure during the exhaust process. As mentioned above, the adjustment variable is preferably the valve opening time of each intermediate blow molding pressure stage (Pi and P+).

[0106] Therefore, the following relationships are taken into account in the adjustment:

[0107] Pi_cycle – Pi_pressure = min

[0108] and

[0109] P+_cycle – P+_pressure = min

[0110] Where min represents the minimum.

[0111] Figure 5 This is a diagram used to illustrate regulation.

[0112] For regulation, a reference variable w(t) is set, such as the desired minimum pressure differential, for example, a pressure differential less than 0.1 bar. The start time of pressurization and / or the start time of return of the flowable medium are used as regulation variables.

[0113] Within the scope of the controlled object, other interfering variables can be taken into account, such as leakage, container rupture, container rejection (especially before the blow molding process), the measured value or characteristics of the dome pressure regulator, possible station shutdown, the properties of the pre-blown bottle, or blow molding termination due to exceeding the limit.

[0114] The regulating system measures the current or actual deviation between the aforementioned pressures and provides this actual value back to the regulator. This allows (particularly in an iterative manner) the determination and / or adjustment of the starting point for the return of the flowable medium.

[0115] The applicant reserves the right to claim all features essential to the invention disclosed in the application documents, provided that these features, individually or in combination, are novel compared to the prior art. Furthermore, it should be noted that features that may be advantageous in themselves are also described in individual figures. It will be immediately apparent to a person skilled in the art that a particular feature described in a figure may be advantageous, even without employing other features in that figure. Additionally, a person skilled in the art will recognize that advantages can also be derived by combining several features shown in a single figure or different figures.

Claims

1. A method for molding a plastic preform (10) into a plastic container (15), wherein, A plastic preform (10) is expanded into the plastic container by applying a flowable medium, wherein the flowable medium is stored in a first accumulator at a first pressure and in a second accumulator at a second pressure higher than the first pressure, wherein a first blow molding pressure is applied to the plastic preform through a fluid connection between the first accumulator and the plastic preform, and a second blow molding pressure is applied to the plastic preform through a fluid connection between the second accumulator and the plastic preform, wherein the flowable medium is at least temporarily fed back to the first accumulator, wherein a first characteristic value (P1, Pi, P2, t1P1, tPi, tP2) is set for the operation of applying the flowable medium to the plastic preform (10). Furthermore, taking into account the first characteristic value, a second value (t2Pi, t2P+) is determined, which is a characteristic value of the time point or time period at which the flowable medium is returned to the first accumulator. Its features are, The expansion pressure (Pexp) is measured before and / or during pressurization of the plastic preform, and / or the circulation pressure is measured during the return of the flowable medium to the plastic container, and the second value is measured taking into account the expansion pressure and the circulation pressure, and a comparison value is measured taking into account the expansion pressure and the circulation pressure, and the second value is measured taking into account the comparison value, wherein the comparison value is the difference and / or quotient of the expansion pressure and the circulation pressure, and / or the second value is adjusted to minimize the comparison value.

2. The method according to claim 1, Its features are, The first characteristic value is selected from the group containing the following values: the magnitude of the pressure, the start time of applying the pressure to the plastic preform, and the end time of applying the pressure to the plastic preform.

3. The method according to claim 1, Its features are, The plastic preform is transported along a predetermined transport path and expands during transport along the transport path.

4. The method according to claim 1, Its features are, At least three different pressures are applied to the plastic preform to expand it.

5. The method according to claim 1, Its features are, To make adjustments, the opening time of at least one valve needs to be modified.

6. The method according to claim 1, Its features are, The method may be implemented for several pressure stages and / or accumulators, and the method may be implemented first for at least one higher pressure stage, followed by the implementation of the method for a lower pressure stage.

7. An apparatus (1) for molding a plastic preform (10) into a plastic container (15), comprising at least one molding station (20) having an application device adapted and used to expand the plastic preform (10) into the plastic container (15) by applying a flowable medium, comprising a first accumulator (2a) for storing the flowable medium at a first pressure and a second accumulator for storing the flowable medium at a second pressure higher than the first pressure, and comprising a first fluid connection (98) between the first accumulator and the plastic preform for applying a first blow molding pressure to the plastic preform through the fluid connection between the first accumulator and the plastic preform, and comprising a second fluid connection between the second accumulator and the plastic preform for applying a second blow molding pressure to the plastic preform through the fluid connection between the second accumulator and the plastic preform, wherein, It also at least temporarily returns the flowable medium from the plastic container to the first accumulator and includes a control device that sets a first characteristic value (P1, Pi, P2, t1P1, tPi, tP2) for applying the flowable medium to the plastic preform (10). Furthermore, the processor device determines a second value, taking into account the first characteristic value, which is a characteristic value of the time point or time period at which the flowable medium is returned to the first accumulator. Its features are, The device (1) has a comparison device that compares the expansion pressure with the circulating pressure and outputs at least one characteristic value of the comparison, and the molding station has a valve configuration that controls the operation of applying a flowable medium to the plastic preform and returning the flowable medium to at least one accumulator, wherein the control is performed with at least part of taking into account the characteristic value of the comparison between the expansion pressure and the circulating pressure.

8. The apparatus (1) according to claim 7. Its features are, The device has at least one sensor device adapted for and used to detect the pressure of the flowable medium in at least one accumulator or in the plastic container.

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