EP3581505B1 - Gassing independent from fill-level - Google Patents

Description

The invention relates to a method for producing packs with pack optics that are at least substantially similar to one another according to claim 1.

The following is related to the present invention Figure 1 problem described.

Figure 1 shows a sealing station 3 'designed for gassing evacuated packaging, which is present, for example, as part of a deep-drawing packaging machine. When gassing the packs positioned within the sealing station, if there are different product fill levels within the respective packs, individual packs that are produced in an optically unequal manner occur.

According to Figure 1 in the case of multi-lane and / or multi-row formats, a total packaging volume P '(hereinafter also: pack volume P') is gassed, which is the sum of a partial volume V1 'formed by the respective packaging trays 14' minus the product contents 22 'present, as well as of a partial volume V2 ', which is present above the respective packaging trays 14' and is enclosed by the upper film 10 '.

The total packaging volume P 'is designed to be overall larger than the totality of the respective individual volumes enclosed by the packaging ultimately produced. This in Figure 1 The total packaging volume P 'shown is used for gas distribution between the packaging. This results in a certain gap S 'between the lower and upper film material, via which the supplied gas can be distributed in all the packs positioned within the sealing station. When the total packaging volume is re-compressed, that is to say when the upper film 10 'is pressed downwards for the sealing process, the following reasons, however, result in optically unevenly produced packaging.

According to Figure 1 the packs positioned within the sealing station 3 'are conventionally gassed to a target gas pressure. For a sealing process for airtight closing of the respective packaging, the upper film material is pressed in the direction of the lower film material after the gassing process. This has the consequence that the amount of gas contained in the partial volume V2 'with the gassing target pressure is pressed into the partial volume V1', so that the pressure rises above the gassing target pressure in the partial volume V1 '.

In addition, it can happen that, due to a rapid downward movement of the upper film material, no more gas equalization can take place between the individual packs positioned within the sealing station.

Different pressure levels that exceed the target gassing pressure then arise within the individual packages, so that the packaging appearance of the respective packages is not uniform.

In the event that a packaging has a high fill level (hereinafter also: filling level), a pressure is established in the packaging that is significantly above the target gas pressure. After the sealing tool has been ventilated to atmospheric pressure, such a pack then acts inflated when the target gas pressure generated initially in the total packaging volume corresponds approximately to atmospheric pressure.

In the event that a packaging has a low degree of filling or is available as empty packaging, the pressure before sealing hardly differs from the pressure that is set in the packaging during sealing, since the pressure increase in partial volume V1 'due to the depression of the Upper film material is relatively low. The consequence of this is that the packaging appears rather depressed after venting if it was initially gassed to a target gassing pressure well below atmospheric pressure, so that the packaging looks normal when the packaging is present with a desired product content.

So far, attempts have been made to counteract the problem described above with a preset gas injection offset pressure.

The use of a gas injection offset printing, however, requires knowledge of the filling level of the respective packaging to be closed, it being assumed that the product line has a constant filling level across the respective packaging. Accordingly, it always becomes problematic when the respective packaging does not have a uniform degree of filling. Despite the use of a gas injection offset printing, finished packaging with a different appearance is then produced due to varying fill levels.

With this approach, the gassing offset pressure previously had to be calculated manually and entered as a calculation parameter on the packaging machine, so that its use is reserved for specially trained operating personnel.

WO 2014/056 806 A1 discloses a sealing station which can be used on a packaging machine for producing sealed packages with a modified atmosphere (MAP).

The object of the invention is to produce a method for producing packs with pack optics that are at least substantially similar to one another. This should be possible even if the respective packs have varying degrees of filling, i.e. are filled unevenly in terms of volume.

This object is achieved by means of a method according to claim 1.

Improved developments of the invention are the subject of the respective subclaims.

• Befüllen eines zwischen einem unteren und einem oberen Verpackungsmaterial eingeschlossenen Packungsvolumens mindestens einer innerhalb der Siegelstation positionierten Verpackung mit einem zur Schaffung einer gewünschten Atmosphäre bestimmten Gas auf einen für eine fertige Verpackung vorbestimmten Begasungssolldruck,
• Ablassen einer Teilmenge des in das Packungsvolumen eingeführten Gases aus dem Packungsvolumen über eine daran angeschlossene Leitung in ein damit verbundenes Auffangvolumen unter Beibehaltung des durch das vorangehende Befüllen erzeugten Packungsvolumens, sodass sich innerhalb des Packungsvolumens für die verbleibende Restmenge des eingefüllten Gases ein relativ zum Begasungssolldruck reduzierter Druck einstellt,

wobei die abgelassene Teilmenge des Gases im Wesentlichen der Masse des innerhalb eines imaginären Teilvolumens des Packungsvolumens aufgenommenen Gases entspricht, welches imaginäre Teilvolumen von einer imaginären, das Packungsvolumen druckquerenden, mindestens einen Teil eines Randes des unteren Verpackungsmaterials einnehmenden Ebene und dem oberen Verpackungsmaterial eingeschlossen wird, und

• Reduzieren des bis dahin aufrechterhaltenen Packungsvolumens um das imaginäre Teilvolumen, indem das obere Verpackungsmaterial in eine im Wesentlichen auf die
• imaginäre Ebene fallende Endlage versetzt wird, sodass der Druck innerhalb der Verpackung wieder auf den Begasungssolldruck ansteigt.

The invention relates to a method for operating a sealing station of a packaging machine, in particular a deep-drawing packaging machine. The method is configured to produce packagings with a pack optics that are at least essentially similar to one another with possibly varying degrees of filling. The method according to the invention comprises the following steps:

• Filling a package volume enclosed between a lower and an upper packaging material of at least one package positioned within the sealing station with a gas intended to create a desired atmosphere to a target gas pressure predetermined for a finished package,
• Discharge of a portion of the gas introduced into the packing volume from the packing volume via a line connected to it into an associated collecting volume while maintaining the packing volume generated by the previous filling, so that within the packing volume for the remaining amount of the filled gas there is a reduced pressure relative to the gassing target pressure adjusts

wherein the released partial amount of the gas corresponds essentially to the mass of the gas taken up within an imaginary partial volume of the packing volume, which imaginary partial volume is enclosed by an imaginary plane which crosses the packing volume, occupies at least a part of an edge of the lower packing material and the upper packing material, and

• Reducing the up to then maintained packing volume by the imaginary partial volume by placing the upper packing material in a substantially on top of the
• imaginary plane falling end position is offset, so that the pressure inside the packaging rises again to the gassing target pressure.

The target gas pressure generated in a respective work cycle in the packaging volume of the packaging (s) left free from products is reduced to a lower pressure level by releasing a detectable portion of the previously supplied gas while maintaining the packaging volume, so that when the subsequent, preferably slow, depression of the Upper film material a re-increase to the gassing target pressure is possible when the upper film material reaches the end position provided for completing the packaging, that is, the package volume is reduced by the imaginary partial volume.

The filling of the package volume to the target gassing pressure and the targeted release of the partial amount of gas to create a reduced pressure level within the package volume can be detected using a pressure sensor connected to the package volume.

The essence of the invention is, for each work cycle, the free, i.e. minus the respective product volumes, available pack volume of one or more packs positioned in the sealing station to initially be gassed to the target gas pressure and then a subset of the initially supplied gas from the imaginary subvolume, which can be predetermined according to physical principles in order to drain the pack volume later when the upper film material is pressed down.

As a result, in the invention, contrary to operation with a fixed, preset gassing offset pressure per work cycle, pressure-regulated gassing to the target gassing pressure, which is adapted to the actual free package volume, and a subsequent releasing of a partial amount of the supplied gas can take place, so that the packaging optics of finished packs, even with possibly varying fill levels and / or also possibly present empty packs, are almost identical to one another.

Accordingly, in the invention, the amount of gas of the partial volume is discharged into the collecting container, which would otherwise be in accordance with Figure 1 closed present packing volume would be compressed.

In the invention, the imaginary plane simultaneously forms an imaginary system limit as a reference for the fact that the amount of gas contained after filling above the system limit, within the imaginary and calculable partial volume, is to be released, whereby the pressure within the packing volume falls as an intermediate step. The subsequent volume reduction by lowering the upper film material to the system limit then leads to the restoration of a gas atmosphere to the target gas pressure level, so that sealing can then take place.

In other words, according to the invention, a filling of the respective packaging adapted to the respective degree of filling to the target gas pressure is automatically simulated by the fact that, in particular when the degree of filling varies per working cycle, the amount of gas within the imaginary partial volume, which is still used at the beginning of the method as an aid for gas distribution is required between the respective packaging, is discharged to the collection volume after the fumigation process.

On the basis of physical principles according to Boyle-Mariott , the amount of gas that is contained within the imaginary, calculable partial volume at the target gassing pressure can be discharged in a controlled manner into the known collection volume, which in turn has a definable initial pressure.

The partial amount of the gas filled into the packing volume, which is discharged via the line, is preferably directed into a collection volume enclosed at least partially by an upper tool part of the sealing station and / or the upper packaging material. According to this variant, the collection volume is provided directly in the upper tool part of the sealing station, that is to say integrated therein, which leads to an advantageous, compact construction of the sealing station for the method according to the invention. In addition, the collection volume and the imaginary partial volume can easily be calculated using known geometries of the structure of the upper part of the tool, which means that the partial amount of gas can be released into the collection volume without any technical problems.

An alternative variant of the invention provides that the partial amount of the gas filled into the packing volume which is let off via the line is passed into a separate collecting container forming the collecting volume. The collecting container thus serves as a separate reference volume, so that a format change and any associated tool change can be carried out particularly easily without influencing the machine program.

It is advantageous if a target pressure for the collection volume is determined on the basis of the partial amount of gas that has been discharged, until the line remains open until it is reached. Preferably, regardless of the embodiment of the collecting volume, the pressure prevailing in the collecting volume is detected by means of a pressure sensor connected to it. This would allow the draining process to be precisely controlled and better timed to be integrated into further process steps. A preset time fixation, possibly resulting in "dead times", for releasing the partial amount of gas is then not necessary. Process control of the discharge process based on the target pressure on the collection volume can be carried out very precisely by means of simple control and regulation technology that may already be present on the machine and leads to an optimization of the entire manufacturing process because of the associated dead time minimization.

The pressure generated within the collection volume by the gas fed into it remains lower during the entire discharge process than the pressure applied within the packing volume to the remaining amount of gas there, so that the packing volume remains stable even after the discharge process. This ensures a high process stability, in particular a high process manufacturing quality.

An advantageous embodiment provides that the upper packaging material is moved into the end position by means of a ventilation process and / or by means of at least one device executing a lifting movement. Ideally, such a process is controlled in such a way that the upper packaging material is moved so slowly into the end position that the residual amount of the filled gas remaining within the packaging volume after the discharge process can be distributed over all the packaging positioned within the sealing station. In this way, the respective packagings can be manufactured to be optically identical to one another.

In the end position, the upper packaging material is preferably sealed with the lower packaging material along an edge region, so that the finished packaging encloses a desired atmosphere in an airtight manner.

An advantageous variant provides that the packing volume is evacuated before filling with gas. As a result, a desired atmosphere can be created very precisely within the respective packaging through the subsequent process steps.

It is possible, according to the inventive principle, to determine the imaginary partial volume and / or the collection volume, in particular their relationship to one another, on the basis of a test run. For this purpose, for example, the lower packaging material could be planar, ie not formed, fed to the sealing station and clamped together with the upper packaging material. When gassing, only a space corresponding to the imaginary partial volume would then be filled with an amount of gas to the target gassing pressure. If the line is then opened until the pressure between the partial volume clamped in the sealing station and the collecting volume is equalized, the volume ratio can be determined from the recorded balanced pressure with prior knowledge of the total volume (consisting of the collecting volume and the partial volume). Consequently, their respective volumes also result.

The method according to the invention can be used in the production of visually comparable packagings with a predetermined, approximately constant filling level for the precise and simple automated determination of an offset pressure, the offset pressure being a difference between the gas injection pressure and that after the partial amount of gas has been released the imaginary partial volume is determined within the packing volume, so that with subsequent machine cycles, the packing volume is only filled with gas until the pressure is reached, which results from the gassing target pressure minus the determined offset pressure. If the packaging to be produced has the same degree of filling as a criterion for the offset function, the method according to the invention could advantageously be used at least at the beginning of the production process to determine the offset pressure, while the draining process is then dispensed with for this product batch.

This process could also be repeated at intervals during production for the purpose of an offset printing update, which may further improve the production quality.

A sealing station of a packaging machine, which is in particular in the form of a thermoforming packaging machine, is suitable for carrying out the invention, the sealing station having a line which connects a packaging volume enclosed between a lower and an upper packaging material at least one packaging positioned within the sealing station with a collection volume, whereby the line is intended to discharge a predetermined portion of a gas previously filled into the packing volume into the collecting volume.

In the invention, the entire package volume is initially filled with a filling gas provided for a desired atmosphere to a target pressure, which is also later used in the ready-made, but with respect to the total package volume reduced packaging should be included. The initially filled packaging volume consists of a first partial volume, which is formed by the spaces left free by the inserted products in the lower preformed packaging material, and a second partial volume, enclosed above the first partial volume and enclosed by the upper packaging material for the purpose of uniform gas distribution. According to the invention, the amount of gas contained in the second partial volume is discharged via the line to the collection volume, so that the pressure prevailing in the maintained packing volume decreases in the meantime, but then by reducing the packing volume by the second partial volume designed for gas distribution to the desired packaging dimension back to the originally generated Target pressure increases.

By means of such a sealing station, packagings with a pack optics that are at least substantially similar to one another can be produced with possibly varying degrees of filling. Furthermore, the sealing station is suitable for carrying out a test run of the type described above.

The pressure level currently prevailing in the packing volume can be recorded for the purpose of gas supply and / or gas discharge control in the collecting volume by means of a pressure sensor connected to the packing volume.

The line is preferably provided with a valve, in particular a 2/2 valve, which can be closed in order to limit the predetermined partial amount of gas to be released into the collecting volume. The valve can be switched process-controlled on the basis of a pressure value detection in the collecting volume, so that the partial amount of gas is precisely discharged. For this purpose, a pressure sensor can be connected to a section of the line leading to the collecting volume.

One variant provides that a volume flow can be controlled by means of the valve. This makes it possible, in particular, to control the discharge process of the partial amount of gas with a high level of process stability.

At least one section of the line is preferably also provided for evacuating and / or gassing the packing volume. The line fulfills a multiple function and can be integrated in a compact manner at the sealing station, if necessary using existing line systems.

A particularly compact design is given when the collecting volume is formed within an upper tool part of the sealing station. Alternatively, the collecting volume is formed by a separate collecting container of the sealing station.

Fig. 1

eine schematische Bauweise einer bekannten Siegelstation ohne Gasablassfunktion,

Fig. 2

eine Verpackungsmaschine, die in Form einer Tiefziehverpackungsmaschine ausgebildet ist und eine Siegelstation mit Gasablassfunktion gemäß der Erfindung aufweist,

Fig. 3

eine schematische Darstellung einer für die Erfindung einsetzbaren Siegelstation mit einem im Werkzeugoberteil integriert ausgebildeten Auffangvolumen,

Fig. 4

eine schematische Darstellung der Siegelstation mit einem durch einen separaten Auffangbehälter ausgebildeten Auffangvolumen und

Fig. 5

das erfindungsgemäße Prinzip in schematischer Darstellung.

The prior art and embodiments of the invention are explained in more detail with reference to the following figures. Show it:

Fig. 1

a schematic construction of a known sealing station without gas discharge function,

Fig. 2

a packaging machine which is designed in the form of a thermoforming packaging machine and has a sealing station with a gas discharge function according to the invention,

Fig. 3

a schematic representation of a sealing station that can be used for the invention with a collecting volume integrated in the upper part of the tool,

Fig. 4

a schematic representation of the sealing station with a collecting volume formed by a separate collecting container and

Fig. 5

the principle according to the invention in a schematic representation.

Figure 1 shows a schematic representation of a sealing station 3 'according to the prior art.

The sealing station 3 'has an upper tool part 20' as well as a lower tool part 21 'which can be brought up to the upper tool part 20' by means of a lifting movement and is designed to receive preformed packaging trays 14 '. In the in Figure 1 shown packaging trays 14 'are products 16' with different degrees of filling 22 'added.

Within the sealing station 3 ', the packaging trays 14', together with an upper film 10 ', enclose an airtight packaging volume P', which consists of a partial volume V1 'and a partial volume V2'. The partial volume V1 'is composed of the sum of the respective packaging tray volumes created by the packaging trays 14' and released by the products 16 '. The partial volume V2 'forms an imaginary partial volume which is enclosed between the upper film 10' and an imaginary plane E 'shown in dashed lines. On the basis of the partial volume V2 ', a connecting gap S' is formed above the two packaging trays 14 ', which allows a distribution of the gas within the packaging volume V' in particular during the filling process. According to Figure 1 is inside the upper part of the tool 20 ', a sealing unit 25' is positioned for a sealing process, which is designed to move the upper film 10 'for a sealing process in the direction of the packaging trays 14' positioned below by means of a lifting movement H '.

At the in Figure 1 embodiment shown, first, the packing volume P ', consisting of the sum of the respective sub-volumes V1' and V2 ', p a Begasungssolldruck _should filled with a gas to provide a desired atmosphere. As a result of the subsequent stroke movement H 'of the sealing unit 25', the amount of gas contained in the partial volume V2 'is pressed into the partial volume V1' released by the products 16 'within the packaging trays 14'. Since the respective degrees of filling 22 'of the packaging trays 14' are different, there is also a different final pressure within the finished packaging V '. This means that the packs V 'cannot be produced with pack optics that are at least essentially similar to one another.

Figure 2 shows a schematic view of a packaging machine 1, which is designed in the form of a thermoforming packaging machine T. The packaging machine 1 has a forming station 2, a sealing station 3, a cross-cutting device 4 and a longitudinal cutting device 5. These are arranged in this order in a working direction R on a machine frame 6.

On the input side of the machine frame 6 of the packaging machine 1, a feed roller 7 is arranged, from which a lower film U is pulled off as the lower packaging material 8. The lower film U is transported into the forming station 2 by means of a feed device (not shown). By means of a deep-drawing process taking place there, packaging trays 14 are formed in the lower film U by means of the forming station 2. The packaging trays 14 are then transported on to an insertion section 15, where they can be filled with a product 16 manually or automatically. Following the insertion section 15, the packaging trays 14 filled with the products 16 are transported on to the sealing station 3. By means of the sealing station 3, the packaging trays 14 can be sealed with an upper film O, which forms an upper packaging material 10, so that by sealing the upper film O onto the packaging trays 14, closed packs V are produced, which are separated with the cross-cutting device 4 and the longitudinal cutting device 5 and can be transported away by means of a discharge device 13.

Figure 3 shows schematically a sealing station 3 as it is at the in Figure 2 packaging machine 1 shown can be used.

The sealing station 3 comprises an upper tool part 20 and a lower tool part 21, which enclose a sealing chamber 23. Figure 3 further shows that two packaging trays 14 with respective products 16 are received in the lower tool part 21, the respective filling levels 22 of the packaging trays 14 differing.

The packaging trays 14 received within the sealing station 3, together with the upper film O arranged above, enclose a packaging volume V. The packing volume V is traversed by means of an imaginary plane E shown in dashed lines, as a result of which it is divided into a partial volume V1 and a partial volume V2. The packaging tray 14, which is present on the right with a lower degree of filling 22 when viewed in the image plane, forms a larger proportion of the packaging volume P than the other packaging tray 14 filled with a higher degree of filling 22 Figure 3 the partial volume V2 enclosed by the upper film O and the imaginary plane E is connected via a line 26 to a collecting volume V3 integrated in the upper tool part 20, which is enclosed between the upper tool part 20 and the upper film O.

According to Figure 3 the packing volume P _is filled via a section 26a of the line 26 with a gas G to create a desired atmosphere to a set gas pressure p setpoint. For the filling process, the section 26a has an inlet valve 37a that can be controlled using a pressure sensor 38a. The pressure sensor 38a is designed to detect the pressure level within the package volume P.

Subsequently, a subset TM contained within the subvolume V2 (see Figure 5 ) of the gas G brought to the set gas pressure p setpoint _is withdrawn from the packing volume P via line 26. The gas G is fed into the collecting volume V3 via sections 26a, 26b, 26c of the line 26. The partial amount TM of the discharged gas G corresponds to the mass of the gas which is contained in the partial volume V2. For the discharge process, the section 26b has a (discharge) valve 27 that can be controlled using a further pressure sensor 48a. The pressure sensor 48a is designed to detect the pressure level within the collecting volume V3.

Section 26c is also present as a ventilation line which has a ventilation valve 47a.

By releasing the partial amount TM, the amount of gas originally admitted during the preceding filling process is reduced to a later amount in connection with Figure 5 residual quantity shown, remains in the packing volume of the gas G P RM, wherein the initially dominant Begasungssolldruck p _set at a lower pressure level decreases _red p.

After the discharged partial amount TM of the gas G has been absorbed by the collection volume V3, the package volume P, i.e. the valve 27 of the discharge line 26, is closed and the upper film O is pressed in the direction of the packaging trays 14 positioned below by means of the sealing unit 25. The upper film O is brought into an end position L positioned in accordance with the imaginary plane E, in which the upper film O is sealed onto the packaging trays 14.

By lowering the upper film O, the gas G contained in the partial volume V2 is pressed into the partial volume V1. Thereby, the set itself during the discharge operation within the package volume reduced pressure P rises p _red back to the Begasungssolldruck p _set at.

The lowering of the upper film O can be controlled so slowly by means of the sealing unit 25, in particular a plate-shaped device 28 that can be lowered thereon, and / or by means of a ventilation process that the residual amount RM contained within the package volume P is slowly distributed over the respective packages V. The device 28 is designed as a product protection plate and is configured to prevent an undesired introduction of heat onto the products 16 received within the packaging trays 14 during the sealing process.

Figure 4 shows the sealing station 3 according to Figure 3 , a separate collecting container 30 being used as collecting volume V3. In addition, a separate ventilation line 26d, which has a ventilation valve 47b, is connected to the sealing chamber 23.

In the Figures 3 and 4th the line 26 includes the valve 27 in its section 26b, which is opened for the discharge process so that the partial amount TM of the gas G can flow from the packing volume P into the collecting volume V3. If the packing volume P is filled by means of the section 26a or the sealing chamber 23 is vented by means of the section 26c, the valve 27 remains closed. In addition, the valve 27 remains closed if the filling process is preceded by an evacuation process of the package volume P. The draining process via the valve 27 can according to FIG Figure 4 can be controlled by means of a pressure sensor 48b connected to the collecting volume V3. The filling process takes place via an inlet valve 37b, which is pressure-controlled by means of a pressure sensor 38b connected to the packing volume P.

For the further transport of sealed packagings V out of the sealing station 3, the upper tool part 20 is moved over the section 26c of Figure 3 or via the separate ventilation line 26d of the Figure 4 ventilated (ie creating a pressure equalization to the atmospheric pressure of the environment). Figure 5 shows the principle of the process according to the invention.

In a first process step, the packing volume P _is filled with the desired gas G to the target gas pressure p setpoint. There is then a predetermined, _to the p Begasungssolldruck corresponding amount of gas in the packing volume GM P.

In the second and third process step, the amount of gas contained within the imaginary partial volume V2 (partial amount TM), which is present above the imaginary plane E drawn in as the system boundary, is transferred to the Figures 3 and 4th line 26 shown drained.

Accordingly, according to the fourth method step, the residual amount RM of the gas G still remaining within the packing volume P is distributed over the entire packing volume P so that a reduced pressure level p _{red is present} within the packing volume P maintained.

Finally, in the fifth method step, the packaging volume P is reduced by the imaginary partial volume V2 in that the upper packaging material is pressed down into the end position L falling on the imaginary plane E. It is now again the Begasungssolldruck p _set within the laid down for finished packaging V partial volume V1 before. According to this process, packaging can be produced with packaging optics that are at least essentially similar to one another, regardless of the degree of filling.

As a basis for the method according to the invention, it is assumed that the sum of the imaginary partial volume V2 with the collection volume V3 is known geometrically.

The ratio of the partial volume V2 and the collection volume V3 can be determined by means of a test run that can be carried out using the sealing station 3. The test run could, for example, be carried out in such a way that the lower film U used for the packaging trays 14 is not introduced into the sealing station 3 in a molded form and is inserted therein together with the Upper film O is fixed. When gassing, only the partial volume V2 _is gassed to the gassing set pressure p _soll . If the line 26 is then opened and left open until the pressure equals the partial volume V2 and the collecting volume V3, the ratio of the partial volume V2 to the collecting volume V3 can be calculated from the pressure that is established. The respective volumes of the partial volume V2 and the collection volume V3 can then be calculated directly from the total volume, consisting of the partial volume V2 and the collection volume V3.

As an alternative to this, the partial volume V2 could also be estimated approximately via a stroke carried out by the sealing unit 25. As a further alternative, the respective volumes V2 and V3 could also be calculated using clearly known reference volumes when the machine is started up. The volumes used in connection with the principle according to the invention, i.e. the partial volume V2 and the collection volume V3, can expediently be stored in a tool database of the packaging machine 1 and are used as calculation variables during the packaging process.

If the same degree of filling of the packaging V to be closed is expected, for example because the same intersection of a selected product 16, for example sliced sausage or sliced cheese, is always present in the respective packaging trays 14, the principle according to the invention can be used for the automated generation of an offset print.

In order to check the correctness of the offset print, it could be provided that it is calculated repeatedly during a product batch using the principle according to the invention.

The invention could just as well be carried out at a sealing station which is part of a packaging machine which is not designed as a thermoforming packaging machine, for example a tray closing machine with a supply of already prefabricated packaging trays.

Claims (10)

1. Method for operating a sealing station (3) of a packaging machine (1) for producing packages (V) with packaging optics being at least essentially similar to one another at possibly varying filling degrees (22), the method comprising the following steps:

   • filling a packaging volume (P), enclosed between a lower and an upper packaging material (8, 10), of at least one package (V) positioned inside the sealing station (3), with a gas (G) intended for creating a desired atmosphere, to a preset gassing target pressure (p_soll) for a finished package (V),

   • discharging a partial quantity (TM) of the gas (G) introduced into the packaging volume (P) from the packaging volume (P) via a line (26) connected thereto into a collection volume (V3) linked thereto while retaining the packaging volume (P) generated by the preceding filling so that inside the packaging volume (P), a pressure reduced (p_red) relative to the gassing target pressure occurs for the remaining residual quantity (RM) of the filled gas (G),

   wherein the discharged partial quantity (TM) of the gas (G) substantially corresponds to the mass of the gas received within an imaginary partial volume (V2) of the packaging volume (P), which imaginary partial volume (V2) is enclosed by an imaginary plane (E), which crosses the packaging volume (P) and which occupies at least a part of an edge (40) of the lower packaging material (8) and the upper packaging material (10), and

   • reducing the packaging volume (P) maintained until then by the imaginary partial volume (V2) while moving the upper packaging material (10) to an end position (L) essentially falling to the imaginary plane (E) so that the pressure (p_red) inside the package increases again to the gassing target pressure (p_soll).
2. Method according to claim 1, characterized in that the partial quantity (TM) of the gas (G) filled into the packaging volume (P) discharged via the line (26) is conducted into a collection volume (V3) at least partially enclosed by a tool upper part (20) of the sealing station (3) and/or the upper packaging material (10).
3. Method according to claim 1, characterized in that the partial quantity (TM) of the gas (G) filled into the packaging volume (P) discharged via the line (26) is conducted into a separate collection container (30) which determines the collection volume (V3).
4. Method according to one of the preceding claims, characterized in that a target pressure for the collection volume (V3) is determined by means of the discharged partial quantity (TM) of the gas (G), up to which point the line (26) remains open.
5. Method according to one of the preceding claims, characterized in that the pressure generated within the collection volume (V3) by the gas (G) introduced therein remains lower than the pressure applied within the packaging volume (P) to the residual quantity (RM) of the gas (G) remaining therein during the entire discharge process in order to maintain the packaging volume (P) during the discharge process.
6. Method according to one of the preceding claims, characterized in that the upper packaging material (10) is moved into the end position (L) by means of an aeration process and/or by means of at least one device (28) executing a lifting movement.
7. Method according to one of the preceding claims, characterized in that the upper packaging material (10) is sealed in the end position (L) with the lower packaging material (8).
8. Method according to one of the preceding claims, characterized in that the packaging volume (P) is evacuated before filling with gas (G).
9. Method according to one of the preceding claims, characterized in that the imaginary partial volume (V2) and/or the collection volume (V3) are determined by means of a test run.
10. Method according to one of the preceding claims, characterized in that the method is used in the production of packages (V) having a predetermined filling degree (22) which remains approximately the same for determining an offset pressure, which is determined from a difference between the gassing target pressure (p_soll) and the pressure (p_red) which is still present within the packaging volume (P) after the partial quantity (TM) of the gas (G) has been discharged from the imaginary partial volume (V2) so that in subsequent machine cycles the packaging volume (P) is only filled with gas (G) until the pressure (p_red) which results from the gassing target pressure (p_soll) less the determined offset pressure is reached.

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