SYSTEM AND METHOD FOR SEALING CONTAINERS

Abstract

A container has a product in a product-receiving area and has a sealing area surrounding the product-receiving area. A length of film is arranged over the container. A space above the film is evacuated using an evacuating portion of an upper sealing module arranged over the film, so as to cause a portion of the film to conform to the upper sealing module. An area of the film is cut out by moving a cutting tool relative to the upper sealing module from a recessed position to a cutting position. The cut-out area of film includes the portion of the film conformed to the upper sealing module, is brought into contact with the sealing area of the container by moving the upper sealing module relative to the container, and is sealed to the sealing area of the container using a heat sealing portion of the upper sealing module.

Claims

1. A method of sealing a container with a film cover, the method comprising: providing a container having a product in a product-receiving area of the container and having a sealing area of the container surrounding the product-receiving area; arranging a length of film over the container; using an upper sealing module arranged over the film, evacuating a space above the film using an evacuating portion of the upper sealing module so as to cause a portion of the film to conform to the upper sealing module; using a cutting tool, cutting out an area of the film by moving the cutting tool relative to the upper sealing module from a recessed position to a cutting position, wherein the cut-out area of film includes the portion of the film conformed to the upper sealing module, wherein a blade of the cutting tool surrounds the upper sealing module such that the area of film is cut out by relative movement of the cutting tool along a direction substantially perpendicular to the film; bringing the cut-out area of film into contact with the sealing area of the container by moving the upper sealing module relative to the container; and sealing the cut-out area of film to the sealing area of the container using a heat sealing portion of the upper sealing module; characterized in that the movement of the cutting tool and the upper sealing module comprises three distinct phases, wherein in a first movement phase the cutting tool is moved relative to the upper sealing module, in a second movement phase the cutting tool and the sealing module move together towards the container, and in a third movement phase the upper sealing module is moved to bring the cut-out area of film into contact with the sealing area of the container and the cutting tool is slowed or stopped relative to the container so that the blade of the cutting tool does not contact the container.

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23. A system for sealing a container with a film cover, the system comprising: a lower sealing module configured to receive a container to be sealed in a holding portion; a film transport system configured to arrange a length of film over the container received in the lower sealing module; an upper sealing module comprising an evacuating portion and a heat sealing portion, the evacuating portion being configured to evacuate a space above the film so as to cause a portion of the film to conform to the upper sealing module and the heat sealing portion being configured to heat seal the film to a container received in the lower sealing module so that the seal surrounds a product-receiving area of the container; and a cutting tool configured to cut around the upper sealing module so as to cut out an area of the film including the portion conformed to the upper sealing module for sealing to the container, wherein the cutting tool is movable relative to the upper sealing module between a retracted position and a cutting position; wherein the cutting tool and the upper sealing module are each movable relative to the lower sealing module, wherein in a first movement phase the cutting tool is movable relative to the upper sealing module from the retracted position to the cutting position for cutting out the area of film, in a second movement phase the cutting tool and the upper sealing module are movable together towards the lower sealing module, and in a third movement phase the upper sealing module is movable relative to the lower sealing module for sealing the film to the container and the cutting tool is slowed or stopped relative to the lower sealing module so that the blade of the cutting tool does not contact the container.

24. A system according to claim 23, wherein the evacuating portion of the upper sealing module comprises a heater plate for heating the film before and/or during evacuation of the space above the film.

25. A system according to claim 23, wherein the lower sealing module comprises an evacuating portion configured to evacuate a space below the film, said space below the film including the holding portion configured to receive the container, and maintain the vacuum while the cut-out area of film is sealed to the container.

26. A system according to claim 23, wherein the upper sealing module and cutting tool are mounted in an upper sealing tool and the lower sealing module is mounted in a lower sealing tool.

27. A system according to claim 26, wherein the upper sealing tool comprises a plurality of upper sealing modules and corresponding cutting tools, and the lower sealing tool comprises a corresponding plurality of lower sealing modules, such that a plurality of containers may be sealed simultaneously.

28. A system according to claim 26, further comprising a clamping plate configured to clamp the film to the upper sealing tool thereby defining an enclosed space above the film for said evacuating portion to evacuate, wherein preferably the clamping plate has an aperture through which at least the upper sealing module can pass to bring the film into contact with a container in the holding portion of the lower sealing module.

29. A system according to claim 28, wherein either the lower sealing tool is configured to clamp to the clamping plate, thereby defining an enclosed space below the film including the holding portion of the lower sealing module, or the clamping plate is a part of the lower sealing tool such that the film is clamped to the upper sealing tool by the lower sealing tool, thereby defining an enclosed space below the film.

30. A system according to claim 26, wherein in the recessed position the cutting tool is recessed with respect to a lower face of the upper sealing tool and the upper sealing module such that a blade of the cutting tool may be retracted away from the film during evacuation of the space above the film.

31. A system according to claim 23, wherein a blade of the cutting tool is shaped to cut the film along a cutting profile, said cutting profile defining a smaller lateral area than the lateral area of the holding portion of the lower sealing module.

32. A system according to claim 23, wherein a blade of the cutting tool surrounds the upper sealing module such that the area of film is cut out by movement of the cutting tool towards the lower sealing module.

33. A system according to claim 23, wherein the cutting tool and the upper sealing module are configured such that the cutting tool is slowed or stationary relative to the lower sealing module during the second movement phase so as to prevent the blade of the cutting tool from contacting a container being sealed.

34. A system according to claim 23, wherein the heat sealing portion surrounds the evacuating portion such that the heat sealing portion is configured to simultaneously form said seal surrounding a product-receiving area of the container.

35. A system according to claim 23, wherein the upper sealing module and the cutting tool are each movably mounted to a common drive element, wherein movement of the drive element from a first position to a second position, along a single direction from the first position to the second position, causes the cutting tool to move from the retracted position to the cutting position and causes the upper sealing module to move relative to the lower sealing module for sealing the cut out area of film to a container.

36. A system according to claim 35, wherein the upper sealing module and the cutting tool are each movably mounted to the common drive element so that they have different movable ranges, such that movement of the drive element from the first position to the second position causes the relative movement between the upper sealing module and the cutting tool in the first movement phase.

37. A system according to claim 36, wherein the upper sealing module and the cutting tool are each movably mounted relative to the common drive element so that they have different movable ranges, such that movement of the drive element from the first position to the second position causes the first movement phase in which the cutting tool advances in the direction towards the lower sealing module relative to the upper sealing module and then causes the second movement phase in which the upper sealing module advances in the direction towards the lower sealing module relative to the cutting tool.

38. A system according to claim 35, wherein in the first position, the common drive element is spaced from the upper sealing module and/or the upper sealing module is mounted via one or more resiliently deformed resilient couplings which act to urge the upper sealing module away from the lower sealing module during the first movement phase as the common drive element moves from the first position to the second position.

39. A system according to claim 35 wherein during the movement of the common drive element from the first position to the second position, the cutting tool moves relative to one or more stopping elements during the first movement phase, said relative movement causing the cutting tool to engage the one or more stopping elements, which thereby inhibit further relative movement of the cutting tool during the second movement phase as the common drive element moves from the first position to the second position, wherein the one or more stopping elements engage a support member of the cutting tool, which carries the blade of the cutting tool, and wherein the cutting tool is mounted via one or more resilient couplings which resiliently deform as the common drive element moves during the second movement phase and movement of the cutting tool is inhibited by the one or more stopping elements.

40. A system according to claim 35, wherein the upper sealing module and the cutting tool are each movably mounted to the common drive element using resilient couplings.

41. A system according to claim 23, wherein the film transport system comprises a supply spool for supporting and dispensing film from a roll of film and further comprising a take-up spool for collecting film not cut out by the cutting tool.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The invention will now be described with reference to the accompanying drawings of which:

[0043] FIG. 1 shows, in schematic cross-section, a system for performing a skin sealing process at a first stage during the process;

[0044] FIG. 2 shows, in schematic cross-section, the system of FIG. 1 at a second stage during the skin sealing process;

[0045] FIG. 3 shows, in schematic cross-section, the system of FIG. 1 at a third stage during the skin sealing process;

[0046] FIG. 4 shows, in schematic cross-section, the system of FIG. 1 at a fourth stage during the skin sealing process;

[0047] FIG. 5 shows, in schematic cross-section, the system of FIG. 1 at a fifth stage during the skin sealing process;

[0048] FIG. 6 shows, in schematic cross-section, the system of FIG. 1 at a sixth stage during the skin sealing process;

[0049] FIG. 7 shows, in schematic cross-section, the system of FIG. 1 having completed the skin sealing process;

[0050] FIG. 8 shows, in schematic cross-section, the final skin sealed container output from the system of FIG. 1;

[0051] FIG. 9 is a flow diagram illustrating the steps of the skin sealing process performed by the system of FIG. 1; and

[0052] FIG. 10 shows, in schematic cross-section, a system containing multiple sealing modules for performing multiple simultaneous skin sealing processes.

DETAILED DESCRIPTION

[0053] An embodiment of a system for performing a skin sealing process will now be described with reference to FIGS. 1 to 7.

[0054] FIG. 1 shows a system 1 for performing a skin sealing process after having been provided with a container to be sealed. The container 10 in this embodiment is a shallow tray having a rim 11 extending around the periphery of the tray. The tray has been provided with a product 15 substantially in the centre of the tray, so that the tray rim laterally surrounds the product. The product 15 may be, for example, a piece of meat, fish or poultry. In this embodiment the tray's depth is less than the height of the product 15 in order to minimise the height of the final sealed container and readily display the skin sealed product, although in other embodiments the tray could be deeper than the product placed therein, or the container could be a substantially flat sheet.

[0055] The tray 10 has been provided to a lower sealing module 210 of a lower sealing tool 200. The lower sealing tool is the frame in which the lower sealing module 210 is supported. In this embodiment, the lower sealing tool 200 supports only one lower sealing module 210, although an embodiment will be described below that contains multiple sealing modules. In this embodiment, the purpose of the lower sealing module is simply to hold the container in place while the upper sealing module 110 seals the film to the container 15. Accordingly, the lower sealing module 210 in this embodiment comprises a recessed area for receiving the tray. The lower sealing module 210 also comprises a supporting portion 211 for supporting the rim 11 of the tray 10. The supporting portion is formed by a ridge surrounding the recessed area of the lower sealing module that substantially matches the outline of the rim 11. When the tray 10 is located in the lower sealing module 210, the supporting portion contacts the lower side of the rim 11 about the entire circumference of the tray and ensures that the rim 11 does not flex away from the upper sealing module 110 as pressure is applied during sealing.

[0056] The upper sealing module 110 is located in an upper tool 100 positioned above the lower sealing tool 200. The upper tool 100 comprises a supporting frame that holds the upper sealing module 110 as well as a cutting tool 130 within a cavity 101 within the upper tool 100.

[0057] The upper sealing module 110 mounted within the upper tool 100 comprises a movable heater plate 111, which is powered to generate heat serving a number of purposes in the sealing process. The heater plate 111 has a lateral shape and size generally corresponding to the shape and size of a container 10. The lower surface of the heater plate 111, which faces the container to be sealed, has a periphery 112 configured to make contact with the rim 11 of the tray 10 in order to effect a seal of the film to the container. The lower periphery 112 of the heater plate (i.e. the heat sealing portion of the upper sealing module 110) is substantially level with the lower face of the upper tool 100 when the heater plate is in its starting position within the upper tool.

[0058] A central region 113 of the heater plate 111 has a generally concave shape, being raised away from the tray relative to the periphery 112 so as to not contact the product or tray as while the periphery seals the film to the rim 11 of the tray 10. The concave central region 113 of the heater plate 111 is provided with an array of openings 114 through the lower surface of the heater plate which serve to communicate air via a network of channels to a pump (not shown) connected to the system. This array of apertures enables the heater plate to also function to evacuate the space above the film, i.e. to act as an evacuating portion of the upper sealing module. As well as evacuating air, the array of openings 114 also allows the heater plate to blow air at the film below, which air may be heated by the heater plate in order to begin to warm the film in preparation for the sealing process.

[0059] The heater plate 111 is mounted on a pair of spring couplings 115 to a movable carriage 120 (which acts as a movable drive element for driving the motion of the heater plate) within the upper tool 100, which will be discussed further below.

[0060] Also mounted within the cavity 101 within the upper tool 100 is a cutting tool 130. The cutting tool comprises a blade 131 that extends entirely around the periphery of the heater plate 111 of the upper sealing module 110. The blade closely follows the periphery of the heater plate 111 so that the area of film that is cut out during the skin sealing process is only slightly larger than the area of the heater plate periphery 112 which defines the position of the seal, and so the film will be only slightly larger than the area encompassed by the seal. Notably, this means that there may be very little excess film, i.e. that which extends beyond the location of the seal, so that there may be substantially no film extending beyond the edge of the rim 11 of the tray 10.

[0061] The blade 131 of the cutting tool 130 is mounted to a cutting tool carriage 132 within the cavity 101 of the upper tool 100, which is movable between a raised and lowered position in order to move the blade of the cutting tool from a retracted position, at which it is recessed within the upper tool 100, to a cutting position for cutting the film, which will be described in more detail later. In particular, when the cutting tool carriage is in the raised starting position, the lower edge of the blade 131, i.e. the part that cuts the film, is retracted into the gap between the lower face of the upper tool 100 and the heater plate periphery 112 so that the film cannot come into contact with the blade.

[0062] The carriage 120 is responsible for causing the cutting blade 131 and the heater plate 111 to move to effect cutting and sealing of the film. The carriage 120 is mounted to the ceiling of the cavity 101 within the upper tool 100 by a pair of spring couplings 121. These spring couplings comprise a shaft that passes through the carriage 120 and whose upper side fixedly connects to the ceiling of the cavity 101. The flanged base of the shaft of the spring coupling connects to the lower end of a spring and the upper end of the spring connects to the carriage 120. The carriage 120 initially sits in contact with the ceiling of the cavity 101 and movement of the carriage downwards, e.g. generated by pneumatic drive (not shown) causes the spring to be compressed between the carriage and the lower end of the shaft of the spring coupling 121. This provides a restorative force that returns the carriage to its raised position when the carriage is no longer being urged downwards.

[0063] The cutting tool carriage 132 is mounted to the carriage 120 by a pair of spring couplings 133. Each spring coupling 133 again comprises a spring mounted around a shaft. In these couplings, the lower end of the shaft is fixed to the cutting tool carriage 132 and the shaft passes through the carriage 120 with the flanged top of the shaft being fitted within a recess in the upper face of the carriage 120. A spring within the spring coupling 133 extends between the base of the shaft where it fixes to the cutting tool carriage 132 and a recess within the lower face of the carriage 120. The tension of the spring ensures that movement of the carriage 120 downwards from its initial position causes the cutting tool carriage 132 to move downwards as well, and hence causes the blade 131 to move towards its cutting position. Once the cutting blade 131 has reached the cutting position, further movement is arrested by the cutting tool carriage 132 coming into contact with the floor of the cavity 101 within the upper tool. This can be seen in FIG. 5. The floor of the cavity 101 within the upper tool restricts the motion of the cutting blade and prevents the cutting blade from continuing downwards and coming into contact with the container during use. While the cutting tool carriage 132 is arrested by contact with the cavity floor, the carriage 120 is able to continue its downward movement, as it now compresses the spring couplings 133 that connect it to the cutting tool carriage.

[0064] The further movement of the carriage 120, once the movement of the cutting tool has been arrested, causes the heater plate 111 to be moved downwards. As mentioned above, the heater plate 111 is connected to the carriage 120 by its own pair of spring couplings 115. Each spring coupling includes a shaft whose base is fixed to an upper side of the heater plate 111 and which passes through the carriage 120. A flanged upper end of each shaft is connected to an upper end of a respective spring. The lower end of each spring is connected to a collar insert, which is fixed to the carriage 120. When the carriage is in its raised starting position, the spring of the spring couplings 115 is compressed, which urges the heater plate 111 upwards by acting on the flanged upper end of the shaft. As the carriage begins to move downwards from its starting position, the springs in the spring couplings 115 begin to decompress while the heater plate 111 remains in its fully raised position. When the carriage 120 reaches approximately the point the cutting tool is arrested, a lower face of the carriage engages the upper side of the heater plate 111 and begins to push this down, out from the lower face of the upper tool 100 and towards the tray 10. This can be seen in FIG. 5.

[0065] The system further comprises a clamping plate 300 positioned between the upper and lower tools 100, 200, which, in use, will clamp the film 20 to the lower surface of the upper tool 100 in order to define an enclosed space above the film in which the upper sealing module 110 and the cutting tool 130 are located. The clamping plate is formed by a substantially flat plate having an aperture 301 therethrough. The clamping plate may extend beyond the edge of the upper and lower tools in direction perpendicular to the feed direction of the film, where is may be coupled to a lifting device for moving the clamping plate 300 up and down. The shape and size of the aperture 301 is slightly larger than the shape and size of the heater plate 111 and cutting blade 131. In use, the upper face of the clamping plate will be clamped to the lower face of the upper tool 100 with the aperture aligned with the upper sealing module and cutting tool. The aperture thereby enables both the cutting blade 131 and the heater plate to advance out of the upper tool 100 and towards the tray even when the clamping plate is in position, clamped to the upper tool.

[0066] In addition to clamping film 20 to the lower surface of the upper tool 100, the lower 200 tool can be clamped to the lower face of the clamping plate 300. This further defines an enclosed space below the film containing the container 10 and product 15. In order to clamp to the clamping plate, the lower tool 200 may be lifted by a lifting device (not shown) located below the lower tool.

[0067] A method of skin sealing that may be performed using this system will now be described with further reference to FIG. 9.

[0068] In step S100, a container 10 holding a product 15 is provided to the lower sealing module 210 of the lower tool. The container is positioned as described above, with the rim 11 of the tray 10 being supported by the supporting portion 211 of the lower sealing module 210 and with the body of the tray being received in the recessed area of the lower sealing module 210. The tray 10 may be provided to the lower sealing module 210 by any suitable container transport system while the sealing tools 100, 200 are in an open configuration, as shown in FIG. 1, and while the clamping plate is spaced from both the upper and lower tools.

[0069] In step S200, film 20 is arranged over the container. While this step is indicated as taking place after step S100, the film may be arranged over the lower sealing module 210 while the container is being transported to the lower sealing module. In this embodiment, the film is fed between the clamping plate 300 and the upper tool 100 by a film transport system, which comprises an upstream spool that holds a continuous web of film and from which the film is unwound and passed through the system before waste film is rewound on a downstream waste film spool. The film transport system is not shown in this embodiment, but an example can be seen in FIG. 8 in the context of a system comprising multiple sealing modules in each tool. As noted above, the film is arranged between the clamping plate 300 and the upper tool 100. The film covers an area greater than the size of the opening into the upper tool 100 so that there is enough film to completely cover the upper sealing module for producing a complete seal of the container during the skin sealing process.

[0070] In step S300, the clamping plate 300 clamps the film 20 to the upper tool 100. This is shown in FIG. 2. As mentioned above, the opening 301 through the clamping plate 300 is aligned with the cutting blade 131 and the heater plate 111. This clamps the film about the entire periphery of the opening into the cavity 101 in the upper tool 100, in which the upper sealing module 110 and the cutting tool 130 are located. This forms an enclosed space above the film 20, inside the upper tool 100.

[0071] In step S400, the heater plate 111 is heated, which heats the film clamped below the heater plate. In practice, the heater plate may already be hot from a previous skin seal process or may have been preheated before the film is clamped to the upper tool 100. The upper sealing module 110 then evacuates the space above the film by using the array of openings 114 through the heater plate, which are in fluid communication with a vacuum pump (not shown). This evacuation of the space above the film 20 draws the film onto the heater plate 111, as shown in FIG. 3. Notably, during this evacuation process, the blade 131 of the cutting tool is located in its recessed position. That is, the cutting tool carriage 132 is in its raised starting position so that the blade 131 is retracted up in the gap between the edge of the opening in the lower face of the upper tool 100 and the lower periphery 112 of the heater plate 111. Accordingly, even when the film is drawn upwards towards the heater plate 111 and blade 131, it is not pulled onto the blade 131, which would cause damage to the film.

[0072] In step S500, the lower tool 200 is clamped to the lower side of the clamping plate 300 to form an enclosed space below the film 20 in which the container and product to be sealed are located. This clamped position of the lower tool 200 is also shown in FIG. 3. In order to effect the clamped position of the lower tool 200, the lower tool may be raised by a lifting unit (not shown) located below the tool in order to press the lower tool upwards against the lower side of the clamping plate. This forms an enclosed space in the lower sealing module 210, below the film, including the tray 10 and the product 15. Optionally, the enclosing of the space below the film may be facilitated by the provision of a sealing member (not shown), such as a rubber seal surrounding the area of the tray 10, in the lower face of the clamping plate 300 or the upper face of the lower tool 200. Once the space below the film including the container 10 is enclosed, the space may be evacuated so that the container is held in a vacuum. The vacuum may be generated by one or more channels connecting into the lower sealing module 210 that are provided in fluid communication with a vacuum generating pump (not shown). It should be noted that the vacuum pressure applied to the space below the film should not be great enough to overcome the vacuum pressure holding the film against the heater plate 111.

[0073] Next, in step S600, the cutting tool 130 is advanced from the retracted position to the cutting position to cut out an area of film 21. The cutting tool in the cutting position is shown in FIG. 4. As noted above, this movement is provided by moving the carriage 120 downward from its raised starting position, e.g. by operation of a pneumatic drive. This movement of the carriage 120 compresses the spring couplings 121 connecting the carriage to the ceiling of the cavity 101, which provide a restorative force on the carriage, tending to move it back towards its starting position, e.g. if the pneumatic drive fails. This downward movement simultaneously urges the cutting tool carriage 132 downwards via the spring couplings 133, thereby causing the cutting blade 131 to move down from its retracted position. In particular, the cutting blade 131 is moved to a position at which it protrudes below the lower face of the upper tool 100 and below the lower periphery 112 of the heater plate 111 and extends into the opening 301 through the clamping plate. In this position, the cutting blade 131 has been forced through the film 20, which is clamped to the upper tool 100 and which is conformed to the heater plate 111 by the evacuation of the space above the film. Since the cutting blade extends closely around the entire periphery of the heater plate 111, this motion of the cutting blade cuts out an area of film 21 that closely matches the area of the heater plate 111. Here it will be appreciated that the film 20 should extend some distance beyond the sides of the heater plate 111 in a direction perpendicular to the feed direction of the film so the film it not cut across the entire width of the web. This will enable the waste film to be wound on to a waste spool, which in turn provides a mechanism for advancing the film web for a subsequent skin seal process.

[0074] It will be noted that the initial downward movement of the carriage 120 that causes the cutting tool 130 to move to the cutting position does not cause the heater plate 111 to move. In particular, this is because the carriage 120 is initially spaced from the heater plate 111 and the spring couplings 115 are initially compressed so that the heater plate 111 continues to be urged upwards and kept in its fully raised position even as the carriage 120 moves downwards and the spring couplings begin to decompress.

[0075] In step S700, the heater plate is advanced to bring the cut out area of film 21 into contact with the container. This final sealing position of the heater plate is shown in FIG. 5. As the carriage 120 continues to move from its position in FIG. 4, at which the cutting tool has been moved to the cutting position, the cutting tool carriage comes into contact with the floor of the cavity 101 inside the upper tool 100. This prevents further downward movement of the cutting tool 130 and hence the cutting blade 131 and so stops the cutting blade from advancing any further towards the container. Now, rather than moving with the carriage 120, the cutting tool remains stationary and the springs of the spring couplings 133 begin to compress in order to allow the carriage 120 to move relative to the cutting tool. The range of motion of the cutting blade will be configured to ensure that the film has been completely cut by the blade 131 but the blade has not been brought into contact with the rim 11 of the tray 10.

[0076] At substantially the same point that the cutting tool 130 is stopped from further movement by the floor of the cavity 101, the carriage 120 comes into contact with the rear of the heater plate 111. Now that the carriage is engaged with the rear of the heater plate, further downward movement of the carriage 120 also causes the heater plate 111 to move downwards and towards the tray 10. The carriage 120 continues to move until the heater plate 111, carrying the cut out area of film 21, passes through the opening 301 in the clamping plate 300 and is brought into contact with the tray 10. In particular, the downward movement of the heater plate 111 moves the lower periphery 112 of the heater plate so that it presses an edge region of the cut out area of film 21 into contact with the rim 11 of the tray. At this point, the supporting portion 211 of the lower sealing module 210 supports the rim of the tray so that high pressure and temperature are generated where the periphery 112 of the heater plate 111 presses the film 21 into contact with the tray rim 11. The heat and pressure applied to the film 21 and tray rim 11 causes the film 21 to fuse to the tray rim 11 about the entire periphery of the tray 10. At this point, the edge of the film is sealed to the tray, while the centre of the cut out area of film 21 is still held under vacuum pressure in contact with the concave centre area 113 of the heater plate 111. Thus, the product 15 located inside the container 10 is now sealed inside the container under vacuum conditions.

[0077] In step S800, the vacuums in the sealing modules 110, 210 may be vented. The relative absence of air sealed inside the container thus causes the heated film to be pulled down from the heater plate 111 and onto the container where it now conforms to the shape of the product 15 located in the container 10. This is shown in FIG. 6. This provides the final skin seal appearance of the sealed container.

[0078] Now that the skin seal process is completed, as shown in FIG. 7, the tools 100, 200 and clamping plate 300 may be separated from one another and the carriage 120, cutting tool 130 and heater plate 111 of the upper sealing module 110 are returned to their starting position by the action of the spring couplings 115, 121 and 133. The skin sealed container may then be removed from the lower sealing module 210 and transported downstream for further packaging or labelling. The waste film 20 may then be wound on to bring a new area of film into place and a new container 10 provided to the now empty lower sealing module 210 so that the process may be performed again for a subsequent container.

[0079] FIG. 8 show the final skin sealed container 10 in cross-section. As shown in this Figure, by performing this process by cutting and then sealing the film to the tray 10, the cut out area of film 21 may be sized slightly smaller than the lateral size of the tray 10 defined by the edge of the rim 11. Therefore, the film does not extend beyond the rim of the tray, providing a so-called inside cut appearance to the skin sealed container.

[0080] In the above description of the system shown in FIGS. 1 to 7, the cutting and sealing performed by the system has been described by referring to movement of the carriage 120 within a stationary upper tool 100 held over a stationary lower tool 200. However, the same relative motions within the sealing process could also be achieved by moving the entire upper tool 100 and lower tool 200 upwards, while the carriage 120 is held stationary, e.g. by a coupling through the upper tool to the frame of the sealing system.

[0081] FIG. 10 shows another system for performing a skin sealing process, this time fitted with multiple sets of sealing modules for performing multiple simultaneous skin seal processes.

[0082] In this embodiment, one common upper tool 100 and one common lower tool 200 define two separate sealing stations, in this case spaced from one another along the process direction. In other embodiment, the sealing stations could be spaced across the process direction, and typically more than two sealing stations will be provided and these may involve a two dimensional spacing of sealing stations.

[0083] Each sealing station is substantially as described above with respect to FIG. 1 7. That is, the first sealing station comprises an upper sealing module 110a, a carriage 120a, and a cutting tool 130a located in a first cavity 101a inside the upper tool, and a lower sealing module 210a located in the lower tool. The second sealing station, located further along the processing direction, likewise comprises an upper sealing module 110b, a carriage 120b, and a cutting tool 130b located in a second cavity 101b inside the upper tool, and a lower sealing module 210b located in the lower tool. The system is also provided with one clamping plate 300, which comprises a first opening therethrough 301a that aligns with the first upper sealing module 110a and cutting tool 130a, and a second opening 301b spaced along the process direction of the system that aligns with the second upper sealing module 110b and cutting tool 130b.

[0084] In use, each sealing station will perform its own skin seal process on a respective container located in the lower sealing module 210a, 210b. This process will be the same as described above with respect to FIGS. 1 to 8.

[0085] FIG. 10 also shows a film transport system 400 for arranging the film 20 over the containers located in the tools. The transport system 400 comprises a supply spool 401 about which a supply of film 20 is wound. Film is unwound from this supply spool 401 and passed through the system, between the upper tool 100 and the clamping plate 300, where it is coupled to a take-up spool 402. The position and orientation of the film through the system is controlled by a pair of feed rollers 403, which ensure that the film is substantially level as it is passed between the upper tool 100 and the clamping plate 300. In use, the supply spool 401 is unwound and the take-up spool wound to move the film through the system. After a skin sealing process is performed, areas of the film will have been cut out, and so the transport system 400 will advance the film so that a fresh area of film is located at each sealing station, and the waste film will be taken up by the take-up spool.