The invention relates to a packaging machine according to the preamble of claim 1.
Various embodiments of packaging machines for packaging contents in packs are known. Machines which are commonly used in the foodstuffs-packaging sector are ones in which the atmospheric air is extracted from the filled pack and then one or more gases are supplied to the packs prior to sealing. These evacuating and subsequent gas-supply steps are important, inter alia, in terms of how long the packaged products can be kept.
In conventional machines, the packs are evacuated in a vacuum chamber. The supply of gas takes place via gas lines which are laid in the region of the packs which are to be treated with gas. Since the packs, during the gas treatment, are not yet sealed, the gas supplied can pass into the negative-pressure chamber or into the suction system of the machine along the same path as the atmospheric air remaining has previously been evacuated. Controlled metered gas treatment of the packs is thus not possible.
The object of the invention is thus to propose a packaging machine in which the controlled supply of gas into the packs is possible.
Taking a packaging machine of the type outlined in the introduction as the departure point, this object is achieved by the defining features of claim 1.
Advantageous embodiments and developments of the invention are made possible by the measures mentioned in the subclaims.
Accordingly, the invention is distinguished in that means are provided for closing the packs in relation to the suction means prior to the gas being supplied.
This prevents the gas supplied from escaping from the pack into the machine flow path used for extraction purposes. The gas which is to be supplied can thus be supplied to the packs in a controlled manner. This allows overall better metering of the gas which is to be supplied and thus better coordination with the contents which are packaged in the pack.
In a packaging machine according to the invention, it is also possible for a plurality of interconnected packs to be simultaneously evacuated and treated with gas. There is no need here for each individual pack to be assigned a suction opening or a gas-inlet opening. Rather, it is also possible for a plurality of interconnected packs, prior to the sealing operation, to be evacuated via one or more common suction openings and treated with gas via one or more common gas-supply lines.
The invention is advantageously used in packs which are produced from at least two sheets, e.g. a top sheet and a bottom sheet. Such packaging machines are known as thermoforming or roll-fed machines and as traysealers.
In the case of the first type of machine, a plurality of interconnected packaging troughs are formed from a bottom sheet and then filled with contents and closed by a top sheet. In a sealing station, the extraction, gas-treatment and pack-sealing steps are carried out usually in one operation. It is only once the pack has been sealed that it is cut into individual packs in a downstream cutting unit.
In so-called traysealers, individual prefabricated trays are filled with contents and then closed by a top sheet in a sealing station, it also being possible here for extraction and gas treatment to take place prior to sealing. The packaging tray is usually likewise prefabricated from a sheet.
Individual trays have a peripheral crosspiece all the way round, while the interconnected packs made in a thermoforming or roll-fed machine may also comprise, in addition to the external peripheral crosspieces, intermediate crosspieces between the individual packs. The top sheet is fixed, e.g. welded, to these crosspieces during sealing of the packs.
Prior to the atmospheric air being extracted from the packs, the latter are preferably moved into a negative-pressure chamber. This is closed, in known embodiments, by two parts of the chamber being moved against one another, e.g. by a bottom part being raised against a top part. The side crosspieces of the packs here are located between the top and bottom parts of the negative-pressure chamber. When these two components are pressed together, the top and bottom sheets are thus pressed together, in which case correspondingly tight sealing can take place at least in the transverse direction, as seen in relation to the advancement direction.
It is possible for both extraction and the supply of gas to take place between the top and bottom sheets. Different procedures are possible here depending on the embodiment of the packaging machine. If use is made of a top sheet which is so narrow that it cannot be pressed together with the bottom sheet laterally between the parts of the negative-pressure chamber, the pack can be evacuated by a negative pressure in the negative-pressure chamber, the air which flows out of the packs passing out along the periphery between the bottom sheet and top sheet. In the case of a wider top sheet, the latter can be pressed together with the bottom sheet all the way round between the parts of the negative-pressure chamber as the latter is closed. In this case, the air in the packs can be extracted through one or more openings in one or both sheets, e.g. in a peripheral crosspiece of the bottom sheet. These openings are preferably located in the peripheral region of the packs or of the arrangement of packs, in the case of a plurality of interconnected packs.
In the case of such packs comprising top and bottom sheets, the flow path out of the packs for the air which is to be extracted can thus be closed by use being made of pressing elements which press the two sheets together. This prevents gas from escaping along the periphery beneath the top sheet, or through any extraction openings in one or both sheets, e.g. the bottom sheet, since these extraction openings can be closed, as can the entire peripheral region, by pressing the sheets together. It is immaterial here as to whether such an opening is closed by the respectively other sheet or by the pressing element directly.
A pressing element for sealing the peripheral region of the packs can be realized, in the region of the transversely running crosspieces (as seen in relation to the advancement direction of the packs in the packaging machine), by a transversely running sealing bar, which is advantageously formed, as a functional unit, by a wall of part of the negative-pressure chamber.
Usually one or more gas-supply lines are located in the longitudinal direction, as seen in relation to the advancement direction of the packs. These gas-supply lines are preferably arranged such that they open out between the sheets, e.g. between a top sheet and a bottom sheet. Since these gas-supply lines are located in the interior of the negative-pressure chamber, it is possible, in the case of the negative-pressure chamber being closed without sealing means according to the invention, for gas supplied into the packs to pass into the negative-pressure chamber and thus into the suction system of the machine.
In order to avoid this it is sought, as has already been indicated a number of times, to seal the interior of the pack. In a preferred embodiment of the invention, then, this is carried out in the longitudinal direction preferably using an additional pressing element which presses the sheets, e.g. the top and bottom sheets, together. For this purpose, use can be made, for example, of one or more sealing bars extending in the longitudinal direction of the packs or of the arrangements or groups of packs.
In order to operate these pressing elements, the invention proposes the use of a lifting unit, which can raise and/or lower the longitudinally and/or transversely running sealing bars.
If use is made of gas-supply lines which are arranged in the interspace between the sheets, the peripheral sealing means, in particular in the form of sealing bars, are preferably developed such that they enclose the gas-supply lines in a form-fitting manner. The sheets or one of the sheets, e.g. the top sheet, mold themselves or molds itself here, between the sealing bars and the gas line, to the shape of the gas line. For this purpose, the sheet is advantageously of elastic design.
Sealing elements which are formed in this way make it possible to seal the interior, of the packs in a manner which is sufficient for the gas to be supplied in a considerably more controlled manner than has been the case up until now.
In a particular embodiment of the invention, a deformable material, for example an elastomer, is used for a sealing bar at least in the region of the gas-supply lines. It is thus possible for sealing bars to consist entirely of an elastomer, for example, in the region with which they press the sheets together. This material deforms, during the pressing operation, such that it molds itself against the gas-supply lines in a form-fitting manner and these gas-supply lines are accommodated, to a certain extent, in the sealing bar.
In the case of packaging machines according to the invention, the packs can be sealed in a conventional manner by the top and bottom sheets being connected, for example by welding. For this purpose, preferably a sealing tool, such as a sealing plate or the like, is arranged within the sealing bars. This sealing tool is then capable, within the sealing bars, of connecting, e.g. welding, the top and bottom sheets along the peripheral crosspieces. In the case of individual packs here, the periphery all the way round, which directly adjoins the sealing bar on the inside, the sealing bar pressing the top and bottom sheets together, is welded. In the case of an arrangement of a plurality of interconnected packs, for example made in a thermoforming or roll-fed machine, the central intermediate and longitudinal crosspieces are also sealed in a conventional manner. The longitudinal and/or transverse crosspieces which are to be sealed in the region of the sealing bars, e.g. the peripheral longitudinal crosspieces, are sealed, as in the case of individual packs, in the region which directly adjoins the corresponding sealing bar on the inside.
Such a packaging machine can operate as follows. A control means for cyclically advancing individual packs or an arrangement of a plurality of interconnected packs causes a corresponding transporting unit to advance the filled packs, in time with the machine, into the bottom part of the sealing station. The bottom part of the sealing station is lowered for this purpose. This bottom part is then raised, in which case the negative-pressure chamber is closed in order for the atmospheric air to be extracted. It is then possible to use a suction pump to extract the atmospheric air located in the packs along with the rest of the air located in the negative-pressure chamber. For this purpose, the air can escape from the packs in the transverse direction between the top and bottom sheets if the top sheet is correspondingly narrow. In the case of a wide top sheet, which also extends along the longitudinal side, as seen in relation to the advancement direction of the machine, into the region between the top and bottom parts of the negative-pressure chamber, and which is thus also pressed together with the bottom sheet in this region, use can be made, in a conventional manner, of suction openings, e.g. in the bottom sheet, and of a downstream arrangement of extraction lines in order to extract the atmospheric air remaining in the packs.
The sealing bars provided for sealing in the longitudinal direction and/or transverse direction are then lowered laterally. This results in sealing between the top and bottom sheets in this region as well. In particular if use is made of elastomers, any gas-supply lines projecting in between the sheets are accommodated in a form-fitting manner.
It is then possible to supply a correspondingly provided gas or a gas mixture. This can be done with the aid of the vacuum present or with the aid of an external positive pressure. Since the interior of the pack is largely sealed toward the outside, there is no connection between the interior of the packs and the extraction system at the point in time when gas is supplied. Precise metering of the gas supplied, inter alia, is thus possible.
An exemplary embodiment of the invention is illustrated in the drawing and will be explained in more detail hereinbelow with reference to the figures, in which, specifically:
FIG. 1 shows a schematic longitudinal section through a sealing station of a first exemplary embodiment of the invention,
FIG. 2 shows a schematic cross section through a sealing station according to FIG. 1,
FIG. 3 shows an enlarged detail of a cross section through a sealing station according to FIGS. 1 and 2, with the sealing bar raised,
FIG. 4 shows an illustration according to
FIG. 3, with the sealing bar lowered,
FIG. 5 shows a further enlarged detail of the cross section according to FIGS. 1 and 2, in the gas-supply region,
FIG. 6 shows a schematic longitudinal section through a further embodiment of the invention,
FIG. 7 shows a schematic cross section through a sealing station according to FIG. 6,
FIG. 8 shows an enlarged detail of a cross section according to FIG. 7, with the sealing bar raised,
FIG. 9 shows an enlarged detail according to FIG. 8, with the sealing bar lowered, and
FIG. 10 shows an enlarged detail of a schematic longitudinal section according to FIG. 6.
The sealing station 1 according to FIG. 1 has a negative-pressure chamber 2 which is formed from a box-like top part 3 and a likewise box-like bottom part 4. In the present embodiment, a seal 5 is provided along the top periphery of the bottom part 4 in order to seal the negative-pressure chamber 2 in the closed position.
A tray formed from a bottom sheet 6 is inserted into the bottom part 4 of the negative-pressure chamber 2. The peripheral crosspiece 7 of the bottom sheet here extends, between the top part 3 and bottom part 4, beyond the negative-pressure chamber 2 since, in the case of a thermoforming or a roll-fed machine, the bottom sheet is drawn off continuously from a supply roll. Accordingly, the sheet with the trays formed therefrom extends longitudinally through the entire machine in one piece from the supply roll to a cutting station (not illustrated) downstream of the sealing station.
A top sheet 8, which is provided as a cover, closes the top side of the bottom sheet 6 and likewise has its periphery 9 extending into the region of the peripheral crosspiece 7, since it is likewise drawn off in one piece from a supply roll.
A sealing bar 10, which extends in the longitudinal direction L as seen in relation to the advancement direction of the sheets in the packaging machine, is arranged in the negative-pressure chamber 2 and provided with a bottom recess 11. Suction lines 12 and gas-supply lines 13 are indicated in FIG. 1 in order to demonstrate the position thereof in the longitudinal direction 11. The lines 12, 13 are actually located in the rear longitudinal wall of the negative-pressure chamber 2, as seen in relation to the illustration in FIG. 1, and are thus not in fact visible in section according to FIG. 1.
It can be gathered from this indication of the position of the lines 12, 13 in FIG. 1, however, that the suction lines 12 are arranged longitudinally beneath the sealing bar 10, while the gas-supply lines 13 are arranged in the region of the recess 11.
In the schematic cross-sectional illustration according to FIG. 2, a section through a gas-supply line 13 is illustrated on the right-hand side. It can be seen in this illustration that the gas-supply line 13 is arranged in a side wall 14 of the bottom part 4. An enlarged detail of the central region, in which the sealing bar 10 is arranged according to the invention, is illustrated in FIG. 4 and will be explained at a later stage in the text.
A section through a suction line 12 is illustrated on the left-hand side of FIG. 2. Correspondingly, the sealing bar 10 here is illustrated in section in a region located outside the recess 11 and above a suction line 12. FIG. 2 also shows a sealing plate 15, which serves as a sealing tool for sealing the pack 16 formed from bottom sheet 6 and top sheet 8.
The detail from FIG. 2 which comprises the sealing bar 10 is shown on an enlarged scale in FIG. 3. In contrast to FIG. 2, however, the sealing bar 10 is illustrated in its raised position, in which the pack 16 is evacuated. As can easily be seen in FIG. 3, the bottom sheet 6 and the top sheet 8 are pressed together along the periphery by the bottom part 4 and the top part 3 of the negative-pressure chamber 2. The pack 16 is thus sealed along the periphery. Air can then be extracted from the pack 16 in suction direction S through the suction opening 12 a of the suction line 12 using suitable negative pressure, for example by way of a suction pump. The flow path between the bottom sheet 6 and top sheet 8 to the suction line 12 is open in this position.
FIG. 4 illustrates the same detail, although in this case the sealing bar 10, which is movable in the direction of the double arrow H, has been lowered. The top sheet 8 is thus pressed onto the bottom sheet 6 in the region of the suction opening 12 a of the suction line 12, as a result of which the suction opening 12 a is closed. That position of the sealing bar 10 which is illustrated in FIG. 4 is established if a gas or gas mixture is to be supplied to the pack 16.
FIG. 5, which shows a cross section through a section plane in the region of the gas-supply line 13, likewise illustrates the sealing bar 10 located in lowered position. However, the supply of gas between bottom sheet 6 and top sheet 8 is possible on account of the recess 11 in the region of the gas-supply line 13. One or more inlet openings 13 a are provided in the peripheral crosspiece 7 for gas-supply purposes. An incoming gas can be directed into the pack 16 via the gas-supply line 13 in this position, as is indicated by the arrow Z. Since, in the same position of the sealing bar 10, the suction openings 12 a are closed, there is no connection, at this point in time, between the interior of the pack 16 and the suction or negative-pressure system of the machine. The controlled supply of gas into the interior of the pack 16 is thus possible.
FIG. 6 shows another variant of the invention, which can be used, for example, when the top sheet 8 is narrower than the negative-pressure chamber 2. This can be seen, for example, in the cross-sectional illustration according to FIG. 7. It can be seen here that the peripheries 17 of the top sheet 8 terminate in the interior of the negative-pressure chamber 2, beneath the in this case somewhat modified sealing bar 18. In this embodiment, the extraction and gas-supply steps take place in the manner described hereinbelow.
As can already be seen in FIG. 6, lateral gas-supply lines 19, which project in between the top sheet 8 and bottom sheet 6 and open out into the interior of the pack 16 beneath the sealing bar 18, are provided. The sealing bar 18, in this case, is provided along its bottom periphery with an elastic material 20, for example an elastomer. As can already be seen in FIG. 6, this elastomer 20 encloses the gas-supply lines 19 in the lowered position of the sealing bar 18.
FIG. 7 shows how the gas-supply lines 19 project along the periphery, beneath the sealing bar 18, into the interior of the pack 16.
The enlarged detail according to FIG. 8 shows the sealing bar 18 in the raised position, which is assumed during evacuation. In this case, the air can escape between the top and the bottom sheets 6, 8 and pass laterally, alongside the gas-supply line 19, into the top region 21 of the negative-pressure chamber 2 (cf. arrows S). By virtue of the negative-pressure chamber 2 being evacuated, the air located in the pack 16 is thus also extracted.
FIG. 9 shows the bottom position of the sealing bar 18, which is movable in the direction of the double arrow H, this position being provided for the supply of gas. It can be seen here that the top sheet 8, in the region of the gas-supply line 19, is pressed onto the latter from above. Also longitudinally in relation to this, the elastomer, 20, which is fitted along the periphery, nevertheless presses the top sheet 8 directly onto the bottom sheet 6, as is illustrated in FIG. 10 in the region of the gas-supply line 19. The elastomer 20 molds itself against the gas-supply line 19 in a form-fitting manner, in which case the top sheet 8 is subjected to pressure throughout and, interacting with the bottom sheet 6, can thus seal the pack 16 along the periphery. In this position, the interior of the pack 16 can be filled with a desired gas or gas mixture through the gas-supply line 19 without any gas flowing into the region of the suction system, in particular of the negative-pressure chamber 2. Improved control of the supply of gas or metering of gas is thus also possible in this embodiment.
As can be gathered from the two embodiments illustrated, the packs 16 can be sealed tight by the sealing plate 15 in the peripheral region of the pack 16, within the sealing bars 10, 18, following filling with the desired gas.
In order to simplify matters, the exemplary embodiments illustrated have been shown just with one pack 16. However, the invention can also readily be used in sealing stations in which a plurality of packs 16 are arranged in a number of rows and/or columns. Provided that these packs 16 are produced in an interconnected manner from a bottom sheet 6 and are closed in an interconnected manner by a top sheet 8, then the same procedures may be selected. It is also possible in this case for extraction to take place via peripheral suction openings and peripheral gas-supply lines.
Furthermore, in such an embodiment, it is additionally possible for one or more sealing bars 10, 18 to be provided in the region of the intermediate crosspieces between individual packs, although there is no need for this in principle. The critical point of the invention is to close the interior of the pack 16 in relation to the suction system of the machine.
- LIST OF DESIGNATIONS
It is also the case that the invention is not restricted in respect of the arrangement of the top and bottom parts 3, 4 of the sealing station 1 illustrated. Obviously, the converse arrangement of supplying the gas from above through corresponding openings in the top sheet can likewise be realized and provides the advantages according to the invention. Similarly, it is immaterial for the invention as to whether the top part and bottom part of the negative-pressure chamber are movable. It is also possible, in principle, for the process to be realized according to the invention with a suction arrangement which is configured in some other way, as long as there is separation between the suction system and the interior of the packs.
- 1 Sealing station
- 2 Negative-pressure chamber
- 3 Top part
- 4 Bottom part
- 5 Seal
- 6 Bottom sheet
- 7 Peripheral crosspiece
- 8 top sheet
- 9 Periphery
- 10 Sealing bar
- 11 Recess
- 12 Suction line
- 12 a Suction opening
- 13 Gas-supply line
- 13 a Inlet opening
- 14 Side wall
- 15 Sealing plate
- 16 Pack
- 17 Periphery
- 18 Sealing bar
- 19 Gas-supply line
- 20 Elastomer