Patent Application
20190118981
The invention relates to a method for continuous or intermittent production of tubular-bag packages using a tubular-bag machine according to the preamble of claim 1. Furthermore, the invention relates to a tubular-bag machine for carrying out the method.
In known tubular-bag machines, a plurality of different products is packaged into tubular-bag packages. These products can be powders or granulates. It is often desirable, in particular in the case of grainy or fine-grained products, for the gas contained in the product, such as air or inert gas, to be extracted from the product during processing on the tubular-bag machine so as to compact the product. Compacting of this kind is often very important at the outlet of the metering tube, in particular, in order to prevent undesired trickling of the product, which might otherwise end up in the fusion zone of the tubular bags to be sealed. In principle, the compactor generically provided in the tubular-bag machine for compacting the product by extracting gas can be employed anywhere in the metering tube. The compactor can be disposed ahead of or behind the metering tube. It is also conceivable for the compactor to be disposed within the extension of the metering tube, such as in the middle of the metering tube.
Tubular-bag machines comprising generic compactors are known from DE 39 15 144 A1 and from EP 1 033 332 A2, for example. These compactors comprise a suction bushing permeable to gas through fine pores, the product to be degassed being led past the inside of the suction bushing. The suction bushing itself is surrounded at its outside by a vacuum chamber which can be subjected to a vacuum via a corresponding pressure supply. Once the vacuum chamber has been subjected to the vacuum, the gas is sucked into the vacuum chamber from the outside through the pores, whereby the product led past the suction bushing is degassed. The pores of the suction bushing need to have a pore width that is smaller than the average particle size of the product in order to prevent the product particles from being sucked into the vacuum chamber.
When the known tubular-bag machines are being operated to produce tubular-bag packages, cyclically repeating work cycles are run. During each work cycle, one tubular bag is filled and closed by the sealing jaws.
One problem of the known vacuum compactors of generic tubular-bag machines is that the suction bushings become increasingly blocked after a certain operating time. Said blockage of the suction bushings is caused by product particles depositing within the pores of the suction bushings and closing them entirely or at least partially. With increasing blockage of the suction bushing, the vacuum existing in the vacuum chamber can no longer be transferred through the pores of the suction bushing, causing the degassing of the product to continuously decrease as the blockage of the suction bushing grows. The growing blockage of the suction bushing can in particular also cause the compaction of the product by gas extraction to become more irregular. Said irregularity is undesirable because it leads to greater metering tolerances regarding the amount of product to be metered per package.
In order to still achieve the desired compaction of the product, generic tubular-bag machines require removal and cleaning of the suction bushing by operating personnel at specific maintenance intervals. However, such cleaning of the suction bushing means a significant amount of installation work. Also, the tubular-bag machine cannot be used to produce tubular tabs as long as the suction bushing is removed, which is why the necessary cleaning of the suction bushings causes undesirable downtimes.
Therefore, the object of the present invention is to propose a new method for continuous or intermittent production of tubular-bag packages using a tubular-bag machine by means of which the amount of work for cleaning the blocked compactor is reduced and downtimes are avoided. Furthermore, compaction of the product is to be kept within freely adjustable limits so as to achieve high metering accuracy and process reliability of the metering process, resulting in economic advantages. Furthermore, the object of the invention is to propose a tubular-bag machine for carrying out the method.
These objects are attained by a method and by a tubular-bag machine according to the teaching of the independent main claims.
Advantageous embodiments of the invention are the subject-matter of the dependent claims.
In the method according to the invention, during the tubular-bag production process with its cyclically repeating work cycles for producing one tubular bag each, a suctioning phase is performed during the work cycle in the known manner. During said suctioning phase, a vacuum is established in the vacuum chamber in the known way so as to compact the product by sucking gas out through the pores of the suction bushing. The vacuum in the vacuum chamber can be lifted to ambient pressure between the individual suctioning phases. However, it is also conceivable for the suctioning phases associated with the individual work cycles to seamlessly transition into each other for some time. This means that the vacuum in the vacuum chamber stays the same for multiple work cycles, whereby a permanent compaction during these work cycles is realized.
The gas may usually be air. However, if the tubular-bag machine is operated under inert gas in order to prevent oxidation processes in the product, the gas can of course also be a corresponding inert gas.
The basic idea of the method according to the invention is that the pores of the suction bushing are cleaned during the tubular-bag production process with its cyclically repeating work cycles so as to avoid downtimes as those caused by interruption of the tubular-bag production process. The actual cleaning of the pores of the suction bushing is effected by integration of a blowing phase, during which the vacuum chamber is pressurized, in at least one work cycle. The pressure in the vacuum chamber during the blowing phase causes the gas to flow in the opposite direction from the vacuum chamber through the pores of the suction bushing in the direction of the product, at least some of the product particles stuck in the pores thus being removed. By this way of cleaning the suction bushing by blowing in a blowing phase being part of at least one work cycle of the tubular-bag production process, downtimes are reduced or even avoided entirely because the cleaning required to prevent blockage of the suction bushing is carried out during the actual tubular-bag production process. The length and intensity of the cleaning by blowing the pores of the suction bushing is to be selected in such a way that, on the one hand, a sufficient cleaning effect is achieved and, on the other hand, there remains enough process time for carrying out the compacting in the suctioning phases.
The intervals at which the blowing phases according to the invention for cleaning the suction bushing are executed during the tubular-bag production process are generally optional as long as a sufficient cleaning effect is achieved. In particular, this is because the frequency of the blowing phases depends on the particular product to be packaged since powdery products, in particular, have a stronger tendency to block the pores of the suction bushing. A particularly simple strategy for cleaning the suction bushing intends for the blowing phases to be executed after a regular number of work cycles in each case. For example, it may be intended that after each three, five or ten tubular bags, a short blowing phase is executed in the respective next work cycle in order for the particles that have accumulated in the pores in the previous work cycles and now adhere to the insides of the pores to be blown out again. In the case of products with a strong tendency to cause blockage, it may also be intended for a short blowing phase to be part of each work cycle, a suctioning phase and a blowing phase thus being run during each work cycle in this case.
Alternatively or additionally to the strategy of executing the blowing phases as a function of the work cycles, the suction bushing can also be blown as a function of the process time for which the suction bushing has been used in compacting the product. For example, it is conceivable that the suction bushing is cleaned by blowing at regular intervals of, for example, three, five or ten minutes during the work cycle that follows next in each case.
If the blowing phases are executed as a function of the work cycles and of the process time, the number of work cycles and the duration of the process time before execution of the next blowing phase, respectively, have to be set by operating personnel. Said setting will be made based on operating personnel's experience as to how heavily the suction bushing becomes blocked during processing of a particular product. Naturally, mistakes can happen in this process, which may cause the number of blowing phases to be too small to ensure sufficient cleaning of the suction bushing. Hence, in order to avoid such mistakes, it is particularly advantageous if the effective vacuum during the suctioning phases is measured using a pressure sensor. This is advantageous because the degree of blockage of the suction bushing can be assessed based on these measured vacuum values and the manner of cleaning by blowing the suction bushing can be varied as a function of the measured values.
It is advantageous, in particular, if the process parameters for blowing the suction bushing are changed as a function of the vacuum values measured using the pressure sensor. For instance, the duration of the individual blowing phases can be varied as a function of the measured vacuum values so as to clean the suction bushing more thoroughly by longer blowing phases if the vacuum values deteriorate, for example.
Alternatively or additionally, the pressure level in the blowing phases can be changed as a function of the vacuum values measured using the pressure sensor. By increasing the pressure level during the blowing phases, a stronger cleaning effect is achieved. So if the measured vacuum values indicate growing blockage of the suction bushing, cleaning of the pores in the suction bushing can be intensified by increasing the pressure level.
If the vacuum in the vacuum chamber is measured during the suctioning phases, in particular the time between the individual blowing phases can be varied as a function of the measured vacuum values. For example, if the vacuum values indicate growing blockage of the pores in the suction bushing, the frequency of the blowing phase can be increased. At the beginning of the tubular-bag production process where the pores in the suction bushing are not blocked, the process can start with a blowing phase frequency at which the pores of the suction bushing are cleaned by blowing only every ten work cycles, for example. Then, if blockage of the pores in the suction bushing grows during the continuing tubular-bag production process, the blowing phase frequency can be increased in increments so that a blowing phase may be executed every nine, then every eight, then every seven, then every six, then every five, then every four, then every three, then every two work cycles and, finally, at the end of each work cycle.
Depending on the particular product to be packaged, it can of course happen that at some point the cleaning effect that can be achieved by blowing the suction bushing does no longer suffice to ensure that the pores of the suction bushing remain appropriately unobstructed. So if all options for increasing the cleaning effect, such as increasing the blowing phase frequency or increasing the duration of the individual blowing phases or increasing the pressure level in the blowing phases, have been exhausted and the vacuum during the vacuum phases still does not reach a certain level, the tubular-bag production process should be interrupted because reliable operation of the tubular-bag machine is no longer ensured given the insufficient vacuum level. Hence, it is intended according to a preferred version of the method for a limit value that the measured vacuum must not fall short of is stored in the controller of the tubular-bag machine. If the limit value is no longer reached during the tubular-bag production process in this case, the tubular-bag production process is interrupted or an error is reported.
The limit value for the vacuum during the suctioning phases depends not only on the degree to which the pores in the suction bushing are cleaned but also on the particular product to be packaged, which means that said limit value has to be defined specifically for each product. To facilitate said product-specific definition of the limit value to be observed, a preferred version of the method intends for the effective vacuum during a suctioning phase using a cleaned suction bushing to be measured using the pressure sensor and to be stored as an initial vacuum value. Said initial vacuum value represents the margins cleared when the suction bushing is clean and the maximum vacuum that can be achieved when the particular product is being packaged. The limit value for interruption of the tubular-bag production process or for reporting an error can then be determined as a function of said measured initial vacuum value. For example, it may be defined that the limit value is 10%, 20%, 30%, 40% or 50% below the initial vacuum value. If the measured vacuum falls short of said threshold derived from the initial vacuum value, i.e. if the measured vacuum value is 10%, 20%, 30%, 40% or 50% below the initial vacuum value, the tubular-bag production process is interrupted or an error is reported so as to allow operating personnel to take suitable countermeasures, such as removal and cleaning of the suction bushing or replacing the blocked suction bushing with a new suction bushing.
The tubular-bag machine according to the invention has a conventional structure including a screw-type metering device and, provided thereon, a compactor having a suction bushing. To allow the method according to the invention to be carried out, it is intended for the vacuum chamber of the tubular-bag machine according to the invention to be connectable not only to a vacuum source as is the case in the state of the art but, according to the invention, also to a pressure source. The compactor will be controlled by the controller as a function of the process parameters of the tubular-bag production process in such a manner that, as a function of the process, blowing phases in which the vacuum chamber is subjected to pressure from the pressure source are executed. The pressure during the blowing phases causes the pores of the suction bushing to be cleaned by blowing out product particles that adhere to the insides of the pores. Cleaning of the pores of the suction bushing takes place during the tubular-bag production process, thus avoiding downtimes for this manner of cleaning.
In order to be able to execute the blowing phases to be executed process-dependently during the tubular-bag production as a function of the blockage present in each of the pores of the suction bushing, it is particularly advantageous if a pressure sensor by means of which the effective vacuum in the vacuum chamber and/or in the vacuum lines can be measured is provided on the tubular-bag machine. In this way, the process parameters of the blowing process can be varied as a function of the measured vacuum, which provides information as to the blockage of the pores of the suction bushing.
The architecture of the screw-type metering device of the tubular-bag machine is basically optional. In a particularly preferred case, the screw-type metering device can be a filling metering screw which is disposed immediately above the sealing jaws which are provided for sealing the tubular bags. Compactors working with vacuum are widely used with these filling metering screws because they allow reliable prevention of trickling of the product into the fusion zone of the sealing jaws located below.
Alternatively, the screw-type metering device can also be configured in the manner of a feeding screw which is disposed in front of a storage tank for intermediate storage of the product.
Different embodiments of the invention are schematically illustrated in the drawing and will be explained below by way of example.
The compactor 07 can be selectively connected to a pressure source 11 and to a vacuum source 12. A switching valve 13 controlled by a controller 14 is provided for switching between the pressure source 11 and the vacuum source 12. The controller 14 for controlling the pressure supply at the compactor 07 can of course also be integrated in the main controller of the tubular-bag machine 01.
At the compactor 07, there is a pressure sensor 15 by means of which the vacuum effective at the compactor 07 during operation of the compactor 07 can be measured. The pressure sensor can alternatively also be disposed on one of the pressure lines. The data of the pressure sensor 15 is transmitted to the controller 14 via a data line. Also, the controller 14 is connected to the drive 09 via a data line. In this way, the operating state can be transmitted to the controller 14 as the metering screw 05 is being driven. The pressure from the pressure source 11 and the vacuum from the vacuum source 12 are transferred to the compactor 07 via a pressure line 16 starting from the switching valve 13.
In the compactor 07, a suction bushing 17 for sucking gas from the product to be conveyed by the metering screw 05 is provided. The suction bushing 17 is composed of a perforated support plate 18 on which the fine-pored filter mat 19 rests. At its outside, the suction bushing 17 is surrounded by a vacuum chamber 20 which can be selectively subjected to pressure or to vacuum via the pressure line 16. When the vacuum chamber 20 is subjected to a vacuum, the gas is sucked out of the product conveyed by the screw 05 through the pores of the filter mat 19 into the vacuum chamber 20, whereby the product is compacted in the desired manner. If the vacuum chamber 20 is then subjected to pressure in another work cycle, the gas flows in the opposite direction through the pores of the filter mat 19, the product particles adhering to the inside of the pores thus being blown out. In this way, the desired cleaning effect for cleaning the suction bushing 17 is achieved.
In a time diagram,
In the lower part of
The version of the method illustrated in
In
A limit value 23 which serves to trigger cleaning of the compactor 07 by blowing the pores in the suction bushing 17 is determined based on the measured initial vacuum value 22. The limit value 23 can be double the initial vacuum value 22, for example.
On the right side of
In
In the 40th work cycle, for example, the measured vacuum pressure 31 is just barely below the limit value 23. In the subsequent 41st work cycle, the measured vacuum value 32 is then just above the limit value 23, which causes the controller to trigger a cleaning cycle including a blowing phase 33 so as to clean the pores by blowing out deposited particles. After that, starting with the next work cycle, the vacuum chamber is permanently subjected to a vacuum again so as to compact the product by sucking out gas. Once the measured vacuum value exceeds the limit value 23 again, another cleaning cycle including a blowing phase 33 will be triggered.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2016 207 549.7 | May 2016 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2017/057826 | 4/3/2017 | WO | 00 |
