EP1595794B1 - Method and apparatus for evacuating a chamber - Google Patents

Abstract

The method for evacuating a chamber (104) filled with a protective gas, especially the sealing chamber of a packing machine (102), comprises evacuating a buffer volume (115) of gas. The concentration of one or more components of the gas is then measured. Alternatively the chamber is connected to a vacuum source and the concentration of the components is measured in the gas stream flowing to it : Independent claims are included for apparatus for carrying out the two variants of the method.

Description

The invention relates to a method and a device for evacuating a fillable with inert gas chamber, in particular a sealing chamber of a packaging machine, as it is used primarily for packaging meat and sausage products.

Packaged meat and sausage products require modified atmosphere packaging to maximize shelf life. Carbon dioxide (CO ₂ ) is often used in protective gas packaging, as it acts bacteriostatic and fungiostatic, ie inhibiting bacterial and fungal growth. Nitrogen (N ₂ ) is used to displace the atmospheric oxygen and as a supporting gas. Since nitrogen only diffuses very slowly through plastic films, the products are mechanically less stressed. In the meat processing industry, gas mixtures of these two components are often used in different compositions.

The fresh meat packaging under protective atmosphere with oxygen content is another process that compared to the pure vacuum packaging and the above packaging Under inert atmosphere (nitrogen) or nitrogen / carbon dioxide mixtures increasingly important.

While the influence of oxygen on most foods has a negative impact on quality, fresh meat has the potential to consume as much oxygen as possible to preserve its red color. Without oxygen, the protein myoglobin (red dye with high oxygen binding affinity) discolors quickly and usually irrevocably dark. An oxygen-enriched protective atmosphere favors the formation of oxymyoglobin, preserving the natural flesh color throughout its shelf-life.

For the packaging of fresh meat mainly machines are used, which have been developed for the sealing of cardboard, aluminum, or plastic trays under a protective atmosphere with increased oxygen concentration.

An infeed belt feeds the machine into a set of shells. The number of trays per batch depends on the capacity of a sealing chamber in which the trays are evacuated. The product to be packed is inserted manually by personnel next to the inlet section. After loading the product, the batch is transported to the sealing chamber. From a film roll arranged above the sealing chamber, the upper film is guided over the shells. Two chamber halves (upper and lower tool) are closed pneumatically. The sealing chamber is pre-evacuated to a certain pressure. This is followed by back-venting the sealing chamber with inert gas to atmospheric pressure. Even during the gassing process, the top film is sealed on the shell and punched out. After opening a ventilation valve for pressure equalization with the environment, the chamber tool is opened and the shells are transported to the outlet conveyor of the machine. Statistical monitoring of the gas composition is done by sampling (non-destructive).

The disposal of the air in the shells before the fumigation (evacuation) can be done in principle by different process techniques.

For individual disposal, a separate vacuum pump is operated on each packaging machine. To save volume, which must be evacuated at each cycle, and at the same time to minimize power losses, the pump is installed in the immediate vicinity of the sealing chamber, if possible, within the machine.

In combined disposal, the use of an accelerator pump (Roots blower) in the machine in combination with a forevacuum generator center outside the packaging space, combined with a corresponding buffer volume, leads to shorter evacuation times. The disposal of the chamber is initially carried out by a pressure equalization with the buffer volume. The final pressure is reached by the Roots pump. This method is usually used for two to four packaging machines and a required final pressure of less than 10mbar.

For combined disposal, the required end pressures of over 50 mbar allow single-stage disposal of the sealed chambers by means of centralized vacuum pumps. The evacuation takes place only by the pressure equalization with the buffer volume. Any number of machines can be connected to such a system.

When being disposed of by a central vacuum system, the evacuation takes place exclusively by pressure equalization of two buffer volumes. The vacuum generators are connected to the packaging machines via two piping systems which simultaneously form the required buffer. They permanently evacuate the vacuum systems rough vacuum and fine vacuum, whose dynamic equilibrium pressure is at different levels. The sealing chambers are connected to the vacuum control unit via suitable actuators. Such a vacuum central system is for example in the EP 0 622 301 B1 shown. The use of a vacuum control unit is recommended when pre-pressures of less than 10 mbar are required and more than about four packaging machines are to be connected to a vacuum system.

In conventional packaging machines, disturbances to the protective gas and / or chamber valves (for example, leakage or faulty activation) can lead to undesired protective gas flows into the vacuum system and thus into the vacuum pumps. Conventional oil-sealed vacuum pumps operated with mineral oil are not suitable for pumping oxygen-enriched gas because of the possibility of ignition of the lubricant in the compression phase. This can only be avoided by the use of oxygen-resistant vacuum pumps, but the preventive use of oxygen-resistant vacuum pumps represents a very cost-intensive solution. The use of sensors for determining the concentration of inert gas, which is promoted in the event of a defect in the direction of the vacuum pump, is not possible in the known machines, since these types of sensors are highly sensitive to pressure fluctuation and need some time after a large pressure fluctuation again to deliver reliable values.

The U.S. Pat. No. 5,822,951 discloses an oxygen sensor for detecting the oxygen concentration in the atmosphere of a vacuum chamber. Here, the vacuum chamber is evacuated and then filled with inert gas. After filling with inert gas, generating an overpressure, a gas sample is withdrawn from the chamber and fed to the oxygen sensor to determine if the oxygen concentration in the protective gas filled package is low enough to meet the shelf life requirements of the product to meet.

The object of the present invention is to propose a method and a device for evacuating a chamber which can be filled with protective gas, in particular a sealing chamber of a packaging machine, wherein the concentration of the protective gas or a gas component of the protective gas flowing to the vacuum source can be reliably determined.

• Evakuieren eines Puffervolumens mittels einer Vakuumquelle,
• Verbinden des Puffervolumens mit der Kammer zur Erzielung eines Druckausgleichs zwischen dem Puffervolumen und der Kammer,
• Trennen des Puffervolumens von der Kammer,
• Ermitteln der Konzentration mindestens einer Gaskomponente des Schutzgases in der Atmosphäre des Puffervolumens oder
• Verbinden der Kammer mit der Vakuumquelle zum weiteren Evakuieren der Kammer und Ermitteln der Konzentration mindestens einer Gaskomponente des Schutzgases in der Atmosphäre des in dem während des Evakuierens aus der Kammer strömenden Gases,

gelöst.According to the invention, the object is achieved by a method for evacuating a chamber which can be filled with protective gas, in particular a sealing chamber of a packaging machine, with the following method steps:

• Evacuating a buffer volume by means of a vacuum source,
• Connecting the buffer volume to the chamber to equalize the pressure between the buffer volume and the chamber,
• Separating the buffer volume from the chamber,
• Determining the concentration of at least one gas component of the protective gas in the atmosphere of the buffer volume or
• Connecting the chamber to the vacuum source to further evacuate the chamber and determining the concentration of at least one gas component of the shielding gas in the atmosphere of the gas flowing out of the chamber during evacuation,

solved.

In determining the concentration of at least one gas component of the protective gas in the atmosphere of the buffer volume, a reliable determination of the at least one gas component is possible. Since conventional sensors, in particular if the sensors has a measuring device for determining the oxygen concentration in gases, are highly pressure-dependent, the sensor must comprise a pressure measuring device, by means of which the signal of the measuring device for determining the oxygen concentration is adjusted. With strong fluctuations in pressure, it can take a few seconds before you can determine a reliable value. The buffer volume ensures that the pressure fluctuation in the buffer volume during the pressure equalization between the buffer volume and the chamber is relatively low, so that a reliable value can be determined quickly in the analysis of the gas in the buffer volume.

By connecting the chamber to the vacuum source to evacuate the chamber and to determine the concentration of at least one gas component of the shielding gas in the atmosphere of the gas flowing out of the chamber during evacuation, the method is also suitable for individual disposal in which each machine has a own vacuum pump as a vacuum source. The pressure curve when evacuating a volume by means of a vacuum pump behaves exponentially over time. This means that initially a very large pressure drop is achieved, whereas the pressure after initial pressure drop is reduced only very slowly. The initial pressure equalization of the chamber with the buffer volume initially ensures a rapid pressure drop. Then, the residual pressure drop is achieved by means of a vacuum pump, which is much slower, so that the pressure-sensitive sensor is only slightly affected by pressure fluctuations and immediately delivers reliable values. The buffer volume temporarily stores the gas that was initially evacuated from the chamber.

After complete evacuation of the chamber, it is filled with inert gas.

Advantageously, while determining the concentration of at least one gas component of the shielding gas in the atmosphere of the buffer volume, the chamber is temporarily connected to a vacuum source for evacuation. Thus, it is possible to wait during the time required to evacuate the chamber until a reliable signal is detected by the sensor without reducing the cycle time of the process. The process does not have to rest to wait for the reliable signal. In particular, when using vacuum central systems can thus achieve a high clock frequency of the individual machines and recognize on which machine a defect has occurred.

The vacuum source may comprise a vacuum reservoir, wherein continuously the concentration of at least one gas component of the protective gas in the atmosphere of the vacuum reservoir is determined. The vacuum reservoir here is advantageously much larger than the volume of the chamber, as in conventional central vacuum systems, so that only very small pressure fluctuations in the vacuum reservoir occur with a pressure equalization between the chamber and the vacuum reservoir, so that the sensor continuously reproduces reliable values in the vacuum reservoir. Thus, in addition to monitoring the individual machines, monitoring of the vacuum central system is ensured.

Preferably, the protective gas used is gas having an oxygen concentration above the oxygen concentration of air, and when determining the concentration of at least one gas component of the protective gas, the oxygen concentration is determined.

In order to prevent the penetration of gas with too high an oxygen concentration in non-oxygen-resistant vacuum pumps, the process is stopped when a predetermined oxygen concentration is exceeded. Here, the predetermined oxygen concentration is above the oxygen concentration of air.

Determining the concentration of at least one gas component of the shielding gas in the atmosphere of the gas flowing out of the chamber during evacuation, after evacuating the chamber, the buffer volume can be evacuated by means of the vacuum pump, the concentration of at least one gas component of the shielding gas during the pre-evacuation the buffer volume of flowing gas is determined. Thus, first of all, the gas flowing out of the chamber is reliably analyzed, whereupon the gas buffered in the buffer volume is reliably analyzed, since the pressure in the buffer volume corresponds to the pressure in the chamber after pressure equalization and thus, when the buffer volume is evacuated, a slow pressure drop also takes place, affecting the sensor only negligibly influenced.

The object is further encompassed by a device for evacuating a chamber which can be filled with protective gas, in particular a sealing chamber of a packaging machine
a buffer volume connectable to the chamber and controlled such that the buffer volume is evacuated prior to connection to the chamber and then temporarily connected to the chamber for pre-evacuation thereof;
a vacuum source connectable to evacuate the chamber and controlled so as to be temporarily connected thereto after pre-evacuating the chamber;
a sensor for determining the concentration of at least one gas component of the protective gas in the atmosphere of the buffer volume or a supply line to the vacuum source, solved.

Further, a protective gas source is provided, which is connectable to the chamber and is controlled so that it is temporarily connected after evacuation of the chamber with this.

According to one embodiment, the sensor is arranged in the buffer volume and a separate from the buffer volume vacuum source is provided, wherein the vacuum source may have a vacuum reservoir. This embodiment is suitable for a Vacuum central system, wherein the vacuum source comprises a vacuum reservoir whose volume is many times greater than the chamber volume and is evacuated by means of one or more central vacuum pumps.

In the vacuum reservoir further sensor for determining the concentration of at least one gas component of the protective gas may be arranged in the atmosphere of the vacuum reservoir.

The device may be provided such that a vacuum supply line for connecting the chamber to the vacuum source is provided, that a vacuum valve in the vacuum supply line for shutting off the same is provided, that a test chamber is provided which represents the buffer volume and connectable via a test line with the vacuum supply line is, wherein the test line between the vacuum valve and the chamber valve opens into the vacuum supply line, that a sensor for determining the concentration of at least one gas component of the protective gas in the atmosphere of the test chamber is provided that a test chamber valve is provided in the test line for shutting off the same and that Shielding gas valve in the protective gas supply line for shutting off the same and a controller for controlling the valve is provided.

Between the vacuum valve and the chamber, a chamber valve in the vacuum supply line to shut off the same is provided. Furthermore, the protective gas source can be connected to the chamber via a protective gas supply line.

The test chamber can additionally be connected via a Prüfkammerzuleitung with the vacuum supply line, the Prüfkammerzuleitung opens between the vacuum valve and the vacuum source in the vacuum supply line. In the Prüfkammerzuleitung a second test chamber valve for shutting off the Prüfkammerzuleitung is provided.

According to a further embodiment, the sensor is provided in a supply line to the vacuum source, which is shown in the form of a vacuum pump. Thus suitable This embodiment is for a single disposal, in which each machine is provided its own vacuum pump.

The object is further encompassed by a device for evacuating a chamber which can be filled with protective gas, in particular a sealing chamber of a packaging machine
a buffer volume that is part of a vacuum source and that is connectable to evacuate the chamber and that is controlled such that the buffer volume is pre-evacuated prior to connection to the chamber and then temporarily connected to the chamber,
a sensor for determining the concentration of at least one gas component of the protective gas in the atmosphere of the buffer volume of the vacuum source which is arranged in the buffer volume, dissolved.

Preferably, a protective gas source is provided, which is connectable to the chamber and is controlled so that it is temporarily connected after evacuation of the chamber with this.

The sensor preferably has an oxygen probe for determining the concentration of at least one gas component of the protective gas in the atmosphere.

Figur 1

eine Skizze einer Vakuumzentralanlage, in der zweie Verpackungsmaschinen angeschlossen sind, mit einer in-situ Sauerstoffzentralüberwachung in ein Puffervolumen der Vakuumzentraleanlage;

Figur 2

eine Skizze einer Vakuumzentralanlage, der eine Verpackungsmaschine an geschlossen ist, mit einer Sauerstoffzentralüberwachung in einem Puffervolumen der Vakuumzentralanlage und einer extraktive Sauerststoffüberwachung an der Verpackungsmaschine und

Figur 3

eine Skizze einer Verpackungsmaschine mit Einzelentsorgung und einer extraktiven Sauerstoffüberwachung an der Verpackungsmaschine.

Preferred embodiments are explained in more detail below with reference to the drawings. Herein shows

FIG. 1

a sketch of a central vacuum plant in which two packaging machines are connected, with an in-situ oxygen central monitoring in a buffer volume of the vacuum central plant;

FIG. 2

a sketch of a central vacuum plant, which is closed to a packaging machine, with an oxygen central monitoring in a buffer volume the vacuum central plant and an extractive oxygen monitoring on the packaging machine and

FIG. 3

a sketch of a packaging machine with individual disposal and an extractive oxygen monitoring on the packaging machine.

FIG. 1 shows a vacuum central system 1, a first packaging machine 2 and a second packaging machine 3. As will be explained later, the central vacuum unit 1 is a two-stage vacuum central plant, the first packaging machine 2 disposed of one stage and the second packaging machine 3 is disposed of in two stages.

The first packaging machine 2 comprises a sealing chamber 4 for creating protective gas packaging. The sealing chamber 4 usually comprises two mold halves, which can be hermetically sealed against each other and form a space that can be evacuated. For packaging, a lower film or a tray is arranged in the sealing chamber 4, in which the product to be packaged lies. Over the lower film or the shell, an upper film is arranged, which is welded to the lower film or the shell after evacuation and, if appropriate, after gasification with protective gas.

The sealing chamber 4 is connected via a vacuum feed line 5 to the central vacuum system 1. In the vacuum supply line 5, a chamber valve 6 is provided for blocking the vacuum supply line 5. In the sealing chamber 4, a pressure transducer 7 is provided in order to determine the internal pressure of the sealing chamber 4 can.

The sealing chamber 4 is further connected via a protective gas supply line 8 with a protective gas source 9. Starting from the protective gas source 9, a pressure limiting valve 10, a pressure regulating valve 11 and a protective gas valve 12 in the form of a switching valve are provided in the protective gas supply line 8.

The sealing chamber 4 is connected to a venting / venting valve 13 for venting and venting the sealing chamber 4.

The central vacuum unit 1 comprises a rough vacuum reservoir 14 and a fine vacuum reservoir 15. The vacuum reservoirs 14, 15 each have a volume which corresponds to a multiple of the volume of the sealing chamber 4. In the rough vacuum reservoir 14 there is generally a pressure of 30 mbar to 40 mbar. In the fine vacuum reservoir 15 there is usually a pressure of 1 mbar to 10 mbar.

For evacuating the rough vacuum reservoir 14, two vacuum pumps 16, 17 are provided, which are connected via switching valves 18, 19 with the rough vacuum reservoir 14. For evacuating the fine vacuum reservoir 15, this is connected to the rough vacuum reservoir 14 via a connecting line 20, wherein two vacuum pumps 21, 22 are provided within the connecting line 20, which can be connected via a switching valve 23 with the fine vacuum reservoir 15. For re-venting the vacuum reservoirs 14, 15, these each have a ventilation valve 24, 25. Further, in the rough vacuum reservoir 14, a first sensor 26 is provided which comprises a first oxygen probe 27 and a first pressure transducer 28. In the fine vacuum reservoir 15, a second sensor 29 is provided, which has a second oxygen probe 30 and a second pressure transducer 31.

When inert gas packaging, a lower film or a tray with the material to be packaged and a top film is first introduced into the opened sealing chamber 4. Then, the sealing chamber 4 is hermetically sealed, wherein the vacuum valve 6, the protective gas valve 12 and the vent valve 13 are initially closed. Then, the chamber valve 6 is opened, so that a pressure equalization between the sealing chamber 4 and the rough vacuum reservoir 14 (with which the sealing chamber 4 is connected) is produced, wherein the rough vacuum reservoir 14 serves as a buffer volume. The rough vacuum reservoir 14 was previously evacuated by the vacuum pumps 16, 17 to a predetermined pressure level. Since that Volume of the rough vacuum reservoir 14 is many times greater than that of the sealing chamber 4, takes place in the pressure compensation only a negligible pressure fluctuation in the rough vacuum reservoir 14, so that the first sensor 26 can continuously provide reliable values. With larger pressure fluctuations, an overshoot of the measurement signal would result, so that a certain time would have to wait to obtain a reliable signal.

Thereafter, the chamber valve 6 is closed again, wherein the chamber valve 6 can be time-controlled or pressure-controlled. That is, either the pressure in the sealing chamber 4 is measured by means of the pressure transducer 7 and upon reaching a predetermined pressure level, the chamber valve 6 is closed or it is waited for a predetermined period of time.

In the following, the protective gas valve 12 is opened, so that the protective gas source 9 is connected to the sealing chamber 4. In this case, the final pressure in the sealing chamber 4 can be regulated by means of the pressure regulating valve 11. Then the protective gas valve 12 is closed again, wherein the protective gas valve 12 may be pressure-controlled. Subsequently, the vent valve 13 is opened, so that a pressure equalization of the sealing chamber 4 takes place with the ambient pressure and the sealing chamber 4 can be opened to remove the packaging.

For the packaging of fresh meat and sausages, often a protective gas with an oxygen concentration above that of air is used. So that no oxygen can reach the vacuum pumps 16, 17 during a leakage at the chamber valve 6 or at the protective gas valve 12, which could cause a fire at the vacuum pumps 16, 17, the oxygen concentration in the rough vacuum reservoir 14 is continuously measured. Should the oxygen concentration exceed a predetermined value, the valves 18, 19 of the vacuum pumps 16, 17 are immediately closed and the vent valves 24, 25 of the vacuum reservoirs 14, 15 are opened in order to prevent further penetration of the oxygen.

The second packaging machine 3 is constructed according to the first packaging machine 2, wherein matching components are provided with the same reference numerals. The difference is that the second packaging machine 3 is disposed of in two stages. The vacuum supply line 5 splits in the direction of the central vacuum system 1 in a first arm 32 and a second arm 33, which can be separated by a first vacuum valve 34 and a second vacuum valve 35, respectively. Thus, first a rough vacuum in the sealing chamber 4 can be achieved by opening the first vacuum valve 34, so that the sealing chamber 4 is connected to the rough vacuum reservoir 14. After closing the first vacuum valve 34, the second vacuum valve 35 is opened, so that the sealing chamber 4 is connected to the fine vacuum reservoir 15. The further sequence corresponds to the sequence of the first packaging machine 2.

With this arrangement, a leak in the supply lines to the protective gas sources 9, 9 'can be detected. However, it can not be determined on which packaging machine the defect has occurred, so that all packaging machines on the central vacuum system 1 must be stopped.

FIG. 2 shows a vacuum central system 101, to which a first packaging machine 102 is connected. The vacuum central plant 101 is like the vacuum central plant according to the embodiment of the FIG. 1 built up. Further, the first packaging machine 102 is similar to the first packaging machine according to the embodiment of FIG FIG. 1 built up. In addition to the first packaging machine 102, further packaging machines can also be connected to the vacuum central system 101. Components associated with components of the embodiments according to FIG. 1 match, are provided with reference numerals, which are increased by 100. It is in this regard to the comments FIG. 1 directed.

The first packaging machine 102 differs from that according to FIG FIG. 1 in that between the chamber valve 106 and the vacuum central system 101, a test chamber 136 is connected in parallel as a puller volume to the vacuum supply line 105. The test chamber 136 is connected via a test line 137 with the vacuum supply line 105 is connected and opens between the chamber valve 106 and the junction with the vacuum central system 101 in the vacuum supply line 105. Further, the test chamber 136 is connected via a Prüfkammerzuleitung 138 with the vacuum supply line 105, wherein the Prüfkammerzuleitung 138 between the junction of the test line 137 and the connection point to the vacuum central system 101st opens into the vacuum supply line 105. In the test line 137, a first test chamber valve 139 is provided for shutting off the test line 137. Furthermore, a second test chamber valve 140 for shutting off the test chamber line 138 is provided in the test chamber feed line 138. In addition, a vacuum valve 141 is arranged between the two junctions of the test line 137 and the Prüfkammerzuleitung 138.

For determining at least one gas component of a protective gas in the atmosphere of the test chamber 136, a third sensor 142 is provided therein, which comprises a third oxygen probe 143 and a third pressure transducer 144, the third sensor 142 having the same function as the first sensor 126 and the second sensor 129. Basically, in the FIG. 2 In the embodiment shown, either the vacuum reservoirs 114, 115 of the vacuum central system 101 or, alternatively, only the test chamber 136 are monitored by sensors. Furthermore, it is possible to provide both cumulatively.

When inert gas packaging, a lower film or a tray with the material to be packaged and a top film is first introduced into the opened sealing chamber 104. Then, the sealing chamber 104 is hermetically sealed, wherein the chamber valve 106, the shielding gas valve 112 and the venting / venting valve 113 are initially closed. Thereafter, the chamber valve 106 and the first test chamber valve 139 is opened, wherein the second test chamber valve 140 and the vacuum valve 141 remain closed. Since the packaging machine 102 is operated in a clocked manner, the test chamber 136 is evacuated from a previous working cycle, so that a pressure equalization takes place between the buffer volume in the form of the test chamber 136 and the sealing chamber 104. As a result, an atmosphere sample of the gas is taken from the sealing chamber 104.

Subsequently, the first test chamber valve 139 is closed, so that the test chamber 136 is sealed airtight. Furthermore, the vacuum valve 141 is opened, so that the sealing chamber 104 is connected to the vacuum central system 101 or to the rough vacuum reservoir 14, so that pressure equalization takes place between the rough vacuum reservoir 114 and the sealing chamber 104. Since, as already described for the previous embodiment, the volume of the large vacuum reservoir 114 is many times greater than the volume of the sealing chamber 104, only a negligible pressure fluctuation takes place in the rough vacuum reservoir 114.

In the further course of the process, the chamber valve 106 is closed by pressure either time-controlled or pressure-controlled by the pressure transducer 107. Then, the shielding gas valve 112 is opened, so that the shielding gas source 109 is connected to the seal chamber 104. In this case, the final pressure in the sealing chamber 104 can be regulated by means of the pressure regulating valve 111. Then the shielding gas valve 112 is closed again, wherein the shielding gas valve 112 may be time or pressure controlled. Subsequently, the venting / venting valve 113 is opened, so that a pressure equalization of the sealing chamber 104 takes place with the ambient pressure and the sealing chamber 104 can be opened again to remove the packaging.

During the time required to evacuate the sealing chamber 104 by means of the vacuum central system 101 and to fill the sealing chamber 104 with inert gas, the gas in the test chamber 136 is analyzed and the concentration of at least one gas component, usually oxygen, of the protective gas in the gas sample of the test chamber 136 determined. Since a high pressure fluctuation has occurred in the test chamber 136 due to the rapid pressure equalization between the test chamber 136 and the seal chamber 104, the third sensor 142 requires a certain amount of time to provide a reliable value. Since the test chamber 136 is disconnected from the system during the evacuation of the seal chamber 104 by means of the vacuum central equipment 101, the time for the determination of a reliable value is used to evacuate the seal chamber 104.

If an excessively high oxygen concentration is determined in the test chamber 136, the process is aborted immediately. In this case, the vacuum valve 141, the first test chamber valve 129 and the second test chamber valve 140 can be closed. Furthermore, the valves 118, 119 of the vacuum pumps 116, 117 are immediately closed and the vent valves 124, 125 of the vacuum reservoirs 114, 115 are opened in order to prevent further penetration of the oxygen.

The remaining gas volume that has passed after the pressure equalization between the test chamber 136 and the sealing chamber 104 during evacuation of the sealing chamber 104 in the rough vacuum reservoir 114 is negligible compared to the volume of the rough vacuum reservoir 114, so that even with a supply of pure oxygen from the Sealing chamber 104 into the rough vacuum reservoir 114, the concentration of oxygen in the rough vacuum reservoir 114 does not exceed the limit. Therefore, the limit of the oxygen concentration at which the process is stopped may be higher in the test chamber than for the vacuum reservoirs 114, 115.

There may be provided sensors 126, 129 in both the rough vacuum reservoir 114 and the fine vacuum reservoir 115.

After the sealing chamber 104 has been filled with protective gas or during which the sealing chamber 104 is filled with protective gas, the second test chamber valve 140 is opened, the first test chamber valve 139 and the vacuum valve 141 remain closed, so that the test chamber 136 is connected to the rough vacuum reservoir 114 and a pressure equalization takes place, so that the test chamber 136 is again pre-evacuated.

During the pre-evacuation of the test chamber 136, the pressure in the test line 137 can be checked by means of a fourth pressure transducer 145 when the first test chamber valve 139, the closed vacuum valve 141 and the closed chamber valve 106 are closed. Occurs then during the filling of the chamber 104 with inert gas, a pressure increase, this is due to a defective chamber valve 106, so that an alarm can be displayed or the procedure aborted.

If no pressure measurement is to take place in the test line 137, the pressure transducer 145, the test chamber inlet 138 and the second test chamber valve 140 may be omitted. In this case, the test chamber 136 is pre-evacuated in that, when the chamber valve 106 is closed, the first test chamber valve 139 and the vacuum valve 141 are opened.

In the same way, a further packaging machine according to the second packaging machine according to FIG. 1 be operated and disposed of in two stages.

Schritt 1:

erstes Prüfkammerventil 139 wird geöffnet
Kammerventil 106 wird geöffnet
Gas aus Siegelkammer 104 strömt in Prüfkammer 136 (zeitgesteuert)

Schritt 2:

erstes Prüfkammerventil 139 wird geschlossen
Verzögerungszeit läuft ab
Sauerstoffkonzentration in der Prüfkammer 136 wird gemessen

Schritt 3:

Vakuumventil 141 wird geöffnet
Restgas aus Siegelkammer 104 wird durch Grobvakuumreservoir 114 entsorgt (druck- oder zeitgesteuert)

Schritt 4:

Vakuumventil 141 wird geschlossen
Kammerventil 106 wird geschlossen
Verzögerungszeit läuft ab

Schritt 5:

erstes Prüfkammerventil 139 wird geöffnet,
Schutzgasventil 112 wird geöffnet
Ende Sauerstoffkonzentrationsmessung
Schutzgas strömt in Siegelkammer 104 (druckgesteuert)
Druckanstieg nach erfolgtem Druckausgleich in Prüfkammer 136 bis zu den geschlossenen Ventilen zweites Prüfkammerventil 140, Vakuumventil 141 und Kammerventil 106 wird überwacht

Schritt 6:

Schutzgasventil 112 wird geschlossen
Verzögerungszeit läuft ab

Schritt 7:

erstes Prüfkammerventil 139 wird geschlossen
zweites Prüfkammerventil 140 wird geöffnet
Be-/Entlüftungsventil 113 wird geöffnet
Ende Druckanstiegsmessung
Prüfgas aus Prüfkammer 136 wird durch Grobvakuumreservoir 114 entsorgt
Druckausgleich der Siegelkammer 104 mit der Umgebung

Schritt 8:

zweites Prüfkammerventil 140 wird geschlossen
Be-/Entlüftungsventil 113 wird geschlossen
Verzögerungszeit läuft ab

A procedure can, for example, proceed as follows:

Step 1:

first test chamber valve 139 is opened
Chamber valve 106 is opened
Gas from seal chamber 104 flows into test chamber 136 (timed)

Step 2:

first test chamber valve 139 is closed
Delay time expires
Oxygen concentration in the test chamber 136 is measured

Step 3:

Vacuum valve 141 is opened
Residual gas from seal chamber 104 is disposed of by rough vacuum reservoir 114 (pressure or time-controlled)

Step 4:

Vacuum valve 141 is closed
Chamber valve 106 is closed
Delay time expires

Step 5:

first test chamber valve 139 is opened,
Inert gas valve 112 is opened
End oxygen concentration measurement
Shielding gas flows into sealing chamber 104 (pressure-controlled)
Pressure increase after pressure equalization in test chamber 136 to the closed valves second test chamber valve 140, vacuum valve 141 and chamber valve 106 is monitored

Step 6:

Inert gas valve 112 is closed
Delay time expires

Step 7:

first test chamber valve 139 is closed
second test chamber valve 140 is opened
Breather valve 113 is opened
End of pressure increase measurement
Test gas from test chamber 136 is disposed of through rough vacuum reservoir 114
Pressure equalization of the sealing chamber 104 with the environment

Step 8:

second test chamber valve 140 is closed
Ventilation valve 113 is closed
Delay time expires

FIG. 3 shows a packaging machine 202 with individual disposal and largely corresponds to the first packaging machine according to the embodiment according to FIG. 1 , Corresponding components are provided with reference numerals which are increased by the value 200. In this regard, the description is based on FIG. 1 directed.

The embodiment according to FIG. 3 is different from that of FIG. 1 in that no vacuum central system 205 but a decentralized vacuum pump 245 is provided directly on the packaging machine 202. The vacuum pump 245 is connected to the sealing chamber 204 via the vacuum feed line, wherein a vacuum valve 241 is provided between the vacuum pump 245 and the chamber valve 206. Further, between vacuum valve 241 and vacuum pump 245, a sensor 246 is provided which includes an oxygen probe 247 and a pressure transducer 248. The sensor 246 corresponds to the sensors according to the FIGS. 1 and 2 ,

Further, a buffer volume 249 is provided in the form of a buffer chamber, which is connected via a buffer volume supply line 251 to the vacuum supply line 205 and opens between the chamber valve 206 and the vacuum valve 241 in the vacuum line 205. In the buffer volume supply line 251, a buffer valve 250 for shutting off the buffer volume supply line 251 is provided.

In vacuum packaging, as in the other embodiment, first a lower foil or a shell with the material to be packaged and a top foil are introduced into the opened sealing chamber 204. Then, the sealing chamber 204 is hermetically sealed, wherein the chamber valve 206, the shielding gas valve 212 and the venting / venting valve 213 are initially closed. Thereafter, the chamber valve 206 and the buffer valve 250 is opened, wherein the buffer volume 249 is still pre-evacuated by a previous process cycle. There is thus a pressure equalization between the sealing chamber 204 and the buffer volume 249 instead. Thereafter, the buffer valve 250 is closed and the vacuum valve 241 is opened while the vacuum pump 245 is running, so that the sealing chamber 204 is further evacuated by means of the vacuum pump 245. Here, the gas flowing out of the seal chamber 204 is continuously analyzed with the sensor 246 to immediately detect an increase in the oxygen concentration.

Basically, the pressure over time runs in the form of an exponential function, ie, in an initial phase of evacuation, the pressure drops rapidly and further Evacuation progressively slower. The initial pressure equalization between the buffer volume 249 and the sealing chamber 204 thus initially ensured a rapid pressure drop, wherein the buffer volume 249 temporarily stores gas emerging from the sealing chamber 204 without conveying it to the vacuum pump 245. Thus, there is no danger that at an initial high pressure swing the sensor 246 will not respond quickly enough and will not provide reliable enough values to turn on the machine early enough in the event of an excessive oxygen concentration before it reaches the vacuum pump. The further evacuation by means of the vacuum pump 245 already starts at a low pressure, so that no more large pressure fluctuations occur and a slow evacuation takes place. The pressure variations are significantly less than initially so that the sensor 246 can continuously provide reliable values to shut off the vacuum pump 245 or close the vacuum valve 241 early enough.

After evacuating the seal chamber 204, the chamber valve 206 is closed, whereupon the seal chamber 204 is filled with inert gas as in the aforementioned embodiments and then aerated. Meanwhile, the check valve 250 is opened so that the buffer volume 249 is also evacuated by the vacuum pump 245 with the vacuum valve 241 open. Since the pressure in the buffer volume 249 is also lower and corresponds to the pressure in the sealing chamber 204 after pressure equalization between the buffer volume 249 and the sealing chamber 204, no large pressure fluctuations occur when evacuating the buffer volume 249 with the vacuum pump 245, so that the sensor 246 continuously provides reliable values to shut down the vacuum pump 245 early enough or close the vacuum valve 241 early enough before the excessively high oxygen concentration gas reaches the vacuum pump 245. Thus, the buffer volume 249 is again sufficiently pre-evacuated to be able to be connected again after closing the vacuum valve 241 with the sealing chamber 204 in the next process cycle for a pressure equalization.

Schritt 1:

Vakuumventil 241 wird geöffnet
Gas aus Siegelkammer 204 strömt in Puffervolumen 249 (zeitgesteuert)

Schritt 2:

Pufferventil 240 wird geschlossen
Verzögerungszeit läuft ab

Schritt 3:

Vakuumventil 241 wird geöffnet
Restgas aus Siegelkammer 204 wird durch Vakuumpumpe 245 entsorgt (druck- oder zeitgesteuert)
Sauerstoffkonzentration wird gemessen

Schritt 4:

Vakuumventil 241 wird geschlossen
Verzögerungszeit läuft ab

Schritt 5:

Pufferventil 240 wird geöffnet
Schutzgasventil 212 wird geöffnet
Schutzgas strömt in Siegelkammer 204 (druckgesteuert)

Schritt 6:

Schutzgasventil 212 wird geschlossen
Verzögerungszeit läuft ab

Schritt 7:

Be-/Entlüftungsventil 213 wird geöffnet
Druckausgleich der Siegelkammer 204 mit der Umgebung

Schritt 8:

Be-/Entlüftungsventil 213 wird geschlossen
Verzögerungszeit läuft ab
Ende Sauerstoffkonzentrationsmessung

A procedure can, for example, proceed as follows:

Step 1:

Vacuum valve 241 is opened
Gas from seal chamber 204 flows into buffer volume 249 (timed)

Step 2:

Buffer valve 240 is closed
Delay time expires

Step 3:

Vacuum valve 241 is opened
Residual gas from seal chamber 204 is disposed of by vacuum pump 245 (pressure or time-controlled)
Oxygen concentration is measured

Step 4:

Vacuum valve 241 is closed
Delay time expires

Step 5:

Buffer valve 240 is opened
Inert gas valve 212 is opened
Shielding gas flows into sealing chamber 204 (pressure-controlled)

Step 6:

Inert gas valve 212 is closed
Delay time expires

Step 7:

Breather valve 213 opens
Pressure equalization of the sealing chamber 204 with the environment

Step 8:

Breather valve 213 is closed
Delay time expires
End oxygen concentration measurement

LIST OF REFERENCE NUMBERS

1, 101

Central vacuum system

2, 102, 202

first packaging machine

3

second packaging machine

4, 104, 204

seal chamber

5, 105, 205

vacuum supply

6, 106, 206

chamber valve

7, 107, 207

Pressure Transmitter

8, 108, 208

Protective gas supply

9, 109, 209

Protective gas source

10, 110, 210

Pressure relief valve

11, 111, 211

Pressure control valve

12, 112,212

Shielding gas valve

13, 113,213

Ventilation / venting valve

14, 114

Rough vacuum reservoir

15, 115

Fine vacuum reservoir

16, 116

vacuum pump

17, 117

vacuum pump

18, 118

switching valve

19, 119

switching valve

20, 120

connecting line

21, 121

vacuum pump

22, 122

vacuum pump

23, 123

switching valve

24, 124

vent valve

25, 125

vent valve

26, 126

first sensor

27, 127

first oxygen probe

28, 128

first pressure transmitter

29, 129

second sensor

30, 130

second oxygen probe

31, 131

second pressure transmitter

32

first arm

33

second arm

34

first vacuum valve

35

second vacuum valve

136

test chamber

137

Test lead

138

Prüfkammerzuleitung

139

first test chamber valve

140

second test chamber valve

141.241

vacuum valve

142

third sensor

143

third oxygen probe

144

third pressure transmitter

145

fourth pressure transmitter

245

vacuum pump

246

sensor

247

oxygen probe

248

Pressure transmitters

249

buffer volume

250

buffer valve

251

Buffer volume supply

Claims (21)

1. A method for evacuating a chamber (4, 104, 204), in particular a sealing chamber of a packaging machine (2, 102, 202, 3, 103, 203), suitable for being filled with a protective gas, comprising the following method steps:

   - evacuating of a buffer volume (14, 15, 114, 115, 136, 249) by means of a vacuum source (1, 101, 245),

   - connecting the buffer volume (14, 15, 114, 115, 136, 249) to chamber (4, 104, 204) for achieving a pressure compensation between the buffer volume (14, 15, 114, 115, 136, 249) and chamber (4, 104, 204),

   - separating of the buffer volume (14, 15, 114, 115, 136, 249) from chamber (4, 104, 204),

   - determining of the concentration of at least one gas component of the protective gas in the atmosphere of the buffer volume (14, 15, 114, 115, 136) or

   - connecting chamber (204) and vacuum source (245) for the further evacuation of chamber (204) and determining of the concentration of at least one gas component of the protective gas in the atmosphere of the gas flowing out of chamber (204) during evacuation.
2. The method according to Claim 1,
   characterized in
   that after the complete evacuation of chamber (4, 104, 204) the latter is filled with protective gas.
3. The method according to one of the Claims 1 or 2,
   characterized in
   that chamber (104) is temporarily connected to vacuum source (101) for evacuation during the determination of the concentration of at least one gas component of the protective gas in the atmosphere of the buffer volume (136).
4. The method according to one of the Claims 1 to 3,
   characterized in
   that the vacuum source comprises a vacuum reservoir (114, 115) and
   that the concentration of at least one gas component of the protective gas in
   the atmosphere of the vacuum reservoir (114, 115) is continuously determined.
5. The method according to one of the Claims 1 to 4,
   characterized in
   that a gas is used as protective gas which has an oxygen concentration higher than the oxygen concentration of air, and
   that the determination of the concentration of at least one gas component of the protective gas comprises the determination of the oxygen concentration.
6. The method according to Claim 5,
   characterized in
   that the process will be aborted, if a predetermined oxygen concentration is exceeded.
7. The method according to Claim 6,
   characterized in
   that the predetermined oxygen concentration is higher than the oxygen concentration of air.
8. The method according to one of the Claims 1 or 2,
   characterized in
   that after the evacuation of chamber (204) the latter is disconnected from the vacuum source (245) and the buffer volume (249) is connected to the vacuum source (245) for evacuation, and
   that the concentration of at least one gas component of the protective gas is determined in the gas flowing out of the buffer volume (249) during evacuation.
9. An apparatus for evacuating a chamber (104, 204), in particular a sealing chamber of a packaging machine (102, 202), suitable for being filled with a protective gas, comprising
   a buffer volume (136, 249) suitable for being connected to chamber (104, 204) and controlled such that the buffer volume (136, 249) is evacuated before being connected to chamber (104, 204) and thereupon is temporarily connected to chamber (104, 204) for pre-evacuation of the latter,
   a vacuum source (101, 245) suitable for being connected to chamber (104, 204) for evacuation of the latter and controlled such that it is temporarily connected to chamber (104, 204) after the pre-evacuation of the latter, and
   a sensor (142, 246) for determining the concentration of at least one gas component of the protective gas in the atmosphere of the buffer volume (136) or in a supply line (205) leading to the vacuum source (245).
10. The apparatus according to Claim 9,
    characterized in
    that a protective gas source (109, 209) is provided suitable for being connected to chamber (104, 204) and controlled such that it is temporarily connected to chamber (104, 204) after the evacuation of the latter.
11. The apparatus according to one of the Claims 9 or 10,
    characterized in
    that the sensor (142) is disposed in the buffer volume (136) and
    that a vacuum source (101) separate from the buffer volume (136) is provided.
12. The apparatus according to Claim 11,
    characterized in
    that the vacuum source (101) comprises at least one vacuum reservoir (114, 115).
13. The apparatus according to Claim 12,
    characterized in
    that a further sensor (126, 129) is arranged in the vacuum reservoir (114, 115) for determination of the concentration of at least one gas component of the protective gas in the atmosphere of the vacuum reservoir (114, 115).
14. The apparatus according to one of the Claims 9 to 13,
    characterized in
    that a vacuum lead-in (105) is provided for connecting the chamber (104) to the vacuum source (101),
    that a vacuum valve (141) is provided in the vacuum lead-in (105) for shutting off the latter,
    that a test chamber (136) is provided which constitutes the buffer volume suitable for being connected to the vacuum lead-in (105) via a test line (137), wherein the test line (137) flows into the vacuum lead-in (105) between the vacuum valve (141) and the chamber valve (106),
    that a sensor (142) is provided for determining the concentration of at least one gas component of the protective gas in the atmosphere of the test chamber (136),
    that a test chamber valve (139) is provided in the test line (137) for shutting off the latter,
    that a protective gas valve (112) is provided in the protective gas supply line (108) for shutting off the latter as well as a control system for controlling the valves.
15. The apparatus according to Claim 14,
    characterized in
    that the chamber valve (106) in the vacuum lead-in (105) is disposed between the vacuum valve (141) and the chamber (104) for shutting off the vacuum lead-in (105).
16. The apparatus according to one of the Claims 14 or 15,
    characterized in
    that the protective gas source (109) is suitable for being connected to the chamber (104) via a protective gas supply line (108).
17. The apparatus according to one of the Claims 14 to 16,
    characterized in
    that the test chamber (136) is suitable for being connected to the vacuum lead-in (105) via a test chamber feed line (138), wherein the test chamber feed line (138) flows into the vacuum lead-in (105) between the vacuum valve (141) and the vacuum source(101), and
    that a second test chamber valve (140) is provided in the test chamber feed line (138) for shutting off the test chamber feed line (138).
18. The apparatus according to one of the Claims 9 or 10,
    characterized in
    that the sensor (246) is provided in a supply line (205) leading to the vacuum source which is represented in the form of a vacuum pump (245).
19. An apparatus for evacuating a chamber (104, 204) suitable for being filled with a protective gas, in particular a sealing chamber of a packaging machine (102, 202), comprising
    a buffer volume (14, 15) being a component part of a vacuum source (1) and suitable for being connected to chamber (4) for evacuating the latter and being controlled such that the buffer volume (14, 15) is pre-evacuated before being connected to chamber (4) and is thereupon connected temporarily to chamber (4),
    a sensor (26, 29), arranged in the buffer volume (14, 15), for determining the concentration of at least one gas component of the protective gas in the atmosphere of the buffer volume (14, 15) of the vacuum source (1).
20. The apparatus according to Claim 19,
    characterized in
    that a protective gas source (9) is provided suitable for being connected to chamber (4) and controlled such that it is temporarily connected to chamber (4) after evacuation of the latter.
21. The apparatus according to one of the Claims 9 to 20,
    characterized in
    that the sensor (26, 29, 126, 129, 142, 246) for determining the concentration of at least one gas component of the protective gas in the atmosphere comprises an oxygen sensor (27, 30, 127, 130, 143, 247).

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