EP1593601A1 - Method for controlling a vacuum packaging machine as well as the machine itself. - Google Patents

Abstract

The method for controlling evacuation of treatment chambers (3) in vacuum packing machines comprises: (A) measuring the time between commencing evacuation and reaching a threshold value of pressure; (B) extrapolating from this the time to reach the desired end pressure; and (C) ending evacuation when this time is reached. Independent claims are included for: (A) a similar method for re-filling the treatment chamber with gas; and (B) a vacuum packing machine fitted with a pressure sensor (7) and control unit (6) for carrying out the methods.

Description

The invention relates to a method according to the preamble of claim 1 or 2 and on a vacuum packaging machine according to the preamble Claim 6.

Im einfachsten Fall erfolgt eine Zeitsteuerung, d.h. der Evakuiervorgang wird nach einer vorgegebenen, beispielsweise an der Maschine vorwählbaren Zeitdauer zwangsläufig beendet. Das hierbei erzielte Endresultat ist sehr ungenau. Die Ungenauigkeit dieser reinen Zeitsteuerung resultiert aus einer Vielzahl von Parametern, die den Verlauf des Evakuiervorgangs beeinflussen, insbesondere auch daraus, dass sich das Kammervolumen in Abhängigkeit von der Menge des eingebrachten Verpackungsguts, durch eventuelles Einbringen oder Herausnehmen von Ausgleichsplatten usw. verändert. Soll ein bestimmtes Vakuum mit Sicherheit erreicht werden, so ist es bei dieser Methode notwendig, die Evakuierdauer großzügig einzustellen, allerdings mit dem Nachteil einer erheblichen Reduzierung der Leistung einer Vakuumverpackungsmaschine (Anzahl der verpackten Einheiten je Zeiteinheit).

To control the evacuation process in vacuum packaging machines, the following methods have hitherto been used:

In the simplest case, there is a time control, ie the evacuation is inevitably terminated after a predetermined, for example, on the machine preselectable period of time. The end result achieved here is very inaccurate. The inaccuracy of this pure timing results from a variety of parameters that influence the course of the evacuation process, in particular also from the fact that the chamber volume changes depending on the amount of the introduced packaged goods, by possibly introducing or removing compensating plates and so on. If a certain vacuum is to be achieved with certainty, it is necessary with this method to set the evacuation time generously, but with the disadvantage of a considerable reduction in the performance of a vacuum packaging machine (number of packaged units per unit time).

Another known method is that the evacuation process on reaching a pressure displayed on a pointer gauge (vacuum watch) is ended. Of the The main disadvantage of this method is that the very low pressure on the End of the evacuation process (final pressure) with such measuring instruments only very inaccurate can be detected.

Also known sensor controls in which the in a chamber of Packaging machine prevailing pressure is constantly detected with a sensor and thereby the evacuation process is controlled. Suitable sensors and the associated Evaluation electronics, however, are expensive and, in particular, susceptible to faults.

The object of the invention is to provide a method with which in particular also with simplified means an optimized control of the evacuation process or the Re-fumigation in a vacuum packaging machine is possible. To solve this Task is a method according to claim 1 or 2 formed. A vacuum packaging machine is the subject of claim 6.

In the invention, the control of the evacuation process and / or takes place Re-fumigation taking into account the signal, for example, a single Sensor, which in the manner of a switch from a state in a second state passes as soon as the pressure in the evacuated or rückbegasten space one predetermined threshold or switching pressure has reached. The switching pressure is thereby in the evacuation well above the target final pressure. That's how it is Switching pressure, for example, in the order of 200 mbar, while as End pressure a pressure of 20 mbar or 2 mbar is sought.

From the period between the initiation of the evacuation process or the Backfilling and the time at which the shearing pressure is reached (switching or Response time), is then by a control and evaluation electronics by extrapolation the evacuation time still needed to the desired final pressure or the entire Evacuation time or Rückbegasungszeit determined. At this time, e.g. a in the control or evaluation electronics educated timer set accordingly, so that then after the evacuation time or Rückbegasungszeit the evacuation or Rückbegasungsvorgang is terminated.

Fig. 1

in sehr vereinfachter schematischer Darstellung eine Vakuumverpackungsmaschine;

Fig. 2

zur Erläuterung der Steuerung des Evakuiervorgangs den Zeit-Druck-Verlauf beim Evakuieren der Kammer der Verpackungsmaschine, bei unterschiedlichen Parametern, wie Kammervolumen und/oder Luftfeuchtigkeit und/oder Lufttemperatur und/oder Zustand der Verpackungsmaschine usw.

Development of the invention are the subject of the dependent claims. The invention will be explained in more detail below with reference to the figures in an exemplary embodiment, in which:

Fig. 1

in a very simplified schematic representation of a vacuum packaging machine;

Fig. 2

to explain the control of the evacuation process the time-pressure curve when evacuating the chamber of the packaging machine, with different parameters such as chamber volume and / or humidity and / or air temperature and / or state of the packaging machine, etc.

The very schematically illustrated in the figure 1 vacuum packaging machine 1, the for packaging food in vacuum-tight packaging or containers 2 serves, has a provided in a packaging line vacuum chamber 3, in the introduced to be packaged container 2 and closed after evacuation become. The vacuum chamber 3 is connected via a vacuum line 4 with a source for the Vacuum connected, d. H. with a vacuum pump 5.

The evacuation time is controlled by means of an evaluation and control electronics 6 and the signal of a pressure sensor 7, in the illustrated embodiment the vacuum chamber 3 is provided and on the in the vacuum chamber. 3 responds to prevailing negative pressure. Of course, the sensor 7 also on elsewhere, for example in the vacuum line 4 or in a separate, with be provided in the interior of the chamber 3 in communication measuring line.

The sensor 7 is designed as a simple _S p to a negative pressure or threshold pressure or switching pressure responsive switch which after reaching the pressure p _s of an electrical state to another electrical state is, for example, switches on or off. The sensor 7 consists for example of a mechanical and cooperating with a switch pressure measuring element, such as pressure cell or spring loaded cylinder or curved tube (Bourdon tube), which changes its radius of curvature depending on the internal pressure. Other designs are conceivable.

Shown in Figure 2, three different curves that there with "Evacuation process x, evacuation process y and evacuation process z are designated and respectively the course of the pressure in the chamber 3 as a function of time when Play evacuation. Through various parameters, such as. B. volume of Chamber 3, humidity, air temperature, condition of the packaging machine and In particular, the pump 5, etc., the course of these curves is different.

Irrespective of this, however, all the curves have in common that the decrease in the pressure P in the chamber 3 as a function of the evacuation time is basically exponential. As a result, there is now the possibility of a particularly simple control of the evacuation process, namely the fact that after the initiation of the evacuation at time t _0, the switching time t _{s is} measured, at which the pressure p _{s is} reached and the sensor 7 responds or a sensor signal to the evaluation and control electronics 6 supplies.

The switching times are for the different course of the evacuation in Figure 2 with the additional index x, y or z, ie with t _sx , t _sy and t _sz designated. Taking into account the switching time, within which the sensor 7 responds after the initiation of the evacuation process, ie the difference between the time t _s and the time to, and taking into account the fundamental course of the pressure-time curve of the evacuation process that time can then be determined in which a desired final pressure, for example a pressure of 20 mbar or 2 mbar is reached and in which the evacuation process can be ended. The switching pressure p _s , at which the sensor 7 responds, for example, 200 mbar and is thus well above the target final pressure, which is then, for example, only 10% or less than the switching pressure.

This means that the control of the evacuation process is a pure timing, but not a forced control but a control in which, taking into account the switching time to reach the pressure p _s , and taking into account the fundamental exponential pressure-time curve, the time of termination of Evacuation process is determined. In this type of control not only the fixed by the construction of the packaging machine 1 parameters, namely z. B. volume of the chamber 3 and delivery volume of the vacuum pump 5, etc., but also changing parameters, such as humidity, air temperature, changes in state of the machine, z. B. the vacuum pump 5 is taken into account.

Evakuiervorgang x:

Zeitdauer der Evakuierung von Atmosphärendruck bis auf p_s z.B. 6 Sekunden

Evakuiervorgang y:

Zeitdauer der Evakuierung von Atmosphärendruck bis auf p_s z.B. 8 Sekunden

Evakuiervorgang z:

Zeitdauer der Evakuierung von Atmosphärendruck bis auf p_s z.B. 10 Sekunden

Due to the parameters, for example, the following time values can result until the switching pressure p _{s is reached} :

Evacuation x:

Duration of evacuation from atmospheric pressure to p _s eg 6 seconds

Evacuation process y:

Duration of the evacuation of atmospheric pressure up to p _s eg 8 seconds

Evacuation process z:

Duration of evacuation from atmospheric pressure to p _s eg 10 seconds

Evakuiervorgang x:

Gesamtevakuierzeit z.B. 15 Sekunden

Evakuiervorgang y:

Gesamtevakuierzeit z.B. 20 Sekunden

Evakuiervorgang z:

Gesamtevakuierzeit z.B. 25 Sekunden

If, for example, a vacuum or negative pressure of 20 mbar is desired, then the total evacuation time is:

Evacuation x:

Total evacuation time eg 15 seconds

Evacuation process y:

Total evacuation time eg 20 seconds

Evacuation process z:

Total evacuation time eg 25 seconds

Evakuiervorgang x:

Gesamtevakuierzeit z.B. 30 Sekunden

Evakuiervorgang y:

Gesamtevakuierzeit z.B. 40 Sekunden

Evakuiervorgang z:

Gesamtevakuierzeit z.B. 50 Sekunden

If, for example, a vacuum or negative pressure of 2 mbar is desired, then the total evacuation time is:

Evacuation x:

Total evacuation time eg 30 seconds

Evacuation process y:

Total evacuation time eg 40 seconds

Evacuation process z:

Total evacuation time eg 50 seconds

The period of time over which the evacuation is maintained after reaching the switching pressure p _s until the end of the evacuation process is then, for example, in the control device 6, taking into account the past until reaching the switching pressure p _s switching time t _s and taking into account the end the evacuation process desired pressure (eg., 20 mbar or 2 mbar) determined, taking into account a stored there arithmetic rule or by using in a memory 6.1 of the control device 6 z. B. tabulated data or data sets containing the total evacuation time as a function of switching time.

In detail, the control is carried out, for example, such that the total time T _{tot of} the evacuation process, ie the total time from switching on the vacuum pump to switching off this pump takes place according to a specific function, namely: T ges = K x F xt s . where K is a constant, for example of the value 0.5 or 1.0, and F is a factor which in turn is a function of the time t _s , in the form that at a particular value for the factor F is independent of the filling volume of the vacuum chamber and thus regardless of the volume of air to be evacuated the chamber in each case a certain final pressure is reached when switching off the vacuum pump. For this purpose, the values for the factor F, which have been determined for the respective embodiment of the packaging machine, for example by measurement, are stored in the memory 6.1 of the measuring and control electronics 6 in a table for different times t _s .

In a preferred embodiment, the vacuum achievable at shutdown of the vacuum pump is adjustable for different applications of the packaging machine, such as an adjuster, eg, rotary switches, etc., by incrementally or stepwise changing the factor F such that each setting is independent from the filling level of the vacuum chamber 3, that is, regardless of the volume of air to be evacuated in each case the vacuum corresponding to this setting is achieved. In this embodiment, too, the values for different factors F assigned to a particular vacuum are stored in the measuring and control electronics 6 or in a local memory 6.1 in a table for different times t _s .

The logic of the measuring and control electronics 6 then, for example, is designed so that at a measured time t _s , which does not exactly correspond to a time value stored in the table, the next higher, contained in the table time value t _s and the associated factor F used for the calculation of the total time T _ges .

Furthermore, the logic of the measurement and control electronics, for example, for a Calculation of intermediate values from the values stored in the table be educated.

The invention has been described above by means of an embodiment. It is understood that numerous changes are possible, without thereby the the Invention invention is abandoned.

Thus, for example, it is possible to provide two or more than two such sensors instead of just one single sensor 7, which then switch or respond at a different switching pressure p _s , so that the expected course of the evacuation process is still determined by determining two or more switching times t _s can be calculated or extrapolated more precisely and thus a further optimization of the control of the evacuation process can be achieved.

The measurement of the time t _s starts, for example, still at atmospheric pressure, for example with the closing of the chamber 3 by a corresponding closing this contact or sensor, or after closing and switching on the vacuum pump upon reaching a predetermined first pressure threshold.

Furthermore, it is for example also a measurement of depending on the Pressure changing shell level possible.

In facilities or machines with recirculation the inventive Procedure can also be carried out in the opposite way. The above was the Invention described in connection with a vacuum packaging machine, in which the evacuation process is performed in a chamber 3. Others too Training is possible.

The above assumption continued to assume that the control of the Evacuation process, d. H. the beginning and the end of the evacuation process respectively Control of the vacuum pump 5 done. Basically, of course also the possibility to control the Evakuiervorgangs a valve assembly provide, on the initiation of the Evakuiervorgangs the interior of the chamber 3 with the vacuum source, d. H. z. B. connected to the pump 5 and at the end the evacuation process, the interior of the chamber 3 separated from the vacuum source and connected to the atmosphere.

LIST OF REFERENCE NUMBERS

1

Vacuum packaging machine

2

packaging

3

chamber

4

vacuum line

5

vacuum pump

6

Measuring and control electronics

6.1

Storage

7

to a switching pressure p _s responsive sensor

Claims (10)

Method for controlling the evacuation process in a treatment chamber (3) of a vacuum packaging machine, characterized in that the time duration (switching time) from the initiation of the evacuation until reaching a predetermined threshold or switching pressure (p _s ) determined in the treatment room (3), then off This switching time is extrapolated to the time required to reach a desired final pressure Evakuierdauer and is terminated when this Evakuierdauer the evacuation. Method for controlling the return fumigation in a treatment chamber (3) of a vacuum packaging machine, characterized in that the time period (switching time) from the initiation of the evacuation until reaching a predetermined threshold or switching pressure (p _s ) in the treatment room (3) determined, then off This switching time is extrapolated to the time required to reach a desired final pressure Evakuierdauer and is terminated when this Evakuierdauer the evacuation. A method according to claim 1 or 2, characterized in that after initiation of the evacuation process or the Rückbegasung each switching times are determined until reaching a first and at least a second switching pressure (p _s ), and then from these switching times the evacuation or Rückbegasungsdauer extrapolated,
and or
that the Evakuierdauer or Rückbegasungsdauer using a typical, exponential course of the evacuation or gas flushing considered formula is determined,
and or
that the Evakuierdauer or Rückbegasungsdauer using a measuring and / or control electronics (6) stored data or data sets is determined in a memory (6.1). Method according to one of the preceding claims, characterized in that the total time T _ges , after which the evacuation process is terminated, is determined by the following function: T ges = K x F x ts, where K is a constant, t _{s is} the time until the pressure threshold value is reached, and F is a factor which, in turn, is stored as a function of t _s in a memory (6.1) of a measurement and control electronics (6) controlling a vacuum source, eg a vacuum pump , Method according to one of the preceding claims,
characterized in that with the at least one sensor the pressure in a chamber (3) of the packaging machine is detected,
and or
that during the evacuation the switching pressure (p _s ) is many times, for example at least about a factor of 10, greater than the final pressure,
and or
that during the return fumigation the switching pressure (p _s ) is a multiple, for example at least approximately a factor of 10 smaller than the final pressure. Vacuum packaging machine with at least one with a vacuum or a negative pressure acted upon during an evacuation treatment chamber (3), with at least one on the pressure in the treatment chamber (3) responsive, designed for example as a pressure switch sensor (7) and with an evacuation in response to the signal the sensor (7) controlling the control device (6), characterized in that the sensor (7) has a first and a second electrical state and upon reaching a threshold or switching pressure (p _s ) in the treatment chamber (3) of the first and in passes the second state,
in that the control electronics (6) have means for measuring the switching time between the initiation of the evacuation operation and the response of the at least one sensor (7) upon reaching the switching pressure (p _s ) and further means for deriving from the at least one switching time and taking into account a predetermined or set final pressure to form a time signal for the completion of the evacuation process. Vacuum packaging machine according to claim 6, characterized in that for a controlled backgassing, the control electronics (6) comprises means for measuring the switching time between the initiation of the backgassing and the response of the at least one sensor (7) upon reaching the switching pressure (p _s ) and further means to form from the at least one switching time and taking into account a predetermined or set final pressure, a time signal for the termination of the return fumigation. Vacuum packaging machine according to claim 6 or 7, characterized by at least two sensors (7) which respond at different switching pressures (p _s ) and thus at different switching times ( _t s), and that the control and evaluation electronics taking into account the at least two switching times (t _s ) forms the time signal for the completion of the evacuation process or the return fumigation. Vacuum packaging machine according to one of claims 6 - 8, characterized in that the control and evaluation electronics (6) has at least one memory (6.1) in which typical data for the duration of the evacuation process or the return fumigation in dependence on the at least one switching time ( t _s ) are stored. Vacuum packaging machine according to one of claims 6 - 9, characterized in that the control and evaluation electronics (6) determines the total time T _ges , after which the evacuation is terminated, by the following function: T ges = K x F x ts, where K is a constant, t _{s is} the time until the pressure threshold value is reached, and F is a factor which, in turn, is stored as a function of t _s in a memory (6.1) of a measurement and control electronics (6) controlling a vacuum source, eg a vacuum pump ,

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