A problem exists in the food packaging industry of keeping container-packaged foodstuffs free from contaminants particularly after a container has been opened and is resealed after the contents are only partially consumed. To date, there is no satisfactory way to provide a resealable container once the container has been opened, such that it adequately reseals to prevent contamination of the remaining contents. This particular problem is not limited to food and beverage products but equally arises when any product is susceptible to oxidation is exposed to the air and is required to be resealed to prevent contamination or deterioration of the product.

Typically, food produce is stored in containers having a body portion forming the reservoir of the container and a reusable lid adapted to cooperate with the rim of the body portion to allow the container to be opened and resealed. In addition to the reusable lid such containers generally provide an original seal in the form of a thin metal film, hot melted, onto the rim of the body portion. The lid is then placed over the sealed base portion to give added protection to the food product and to provide a reusable seal. In this state, the metal film can provide evidence of tampering if it has been opened or punctured. To access the food product, a user may break the original seal of the film by pulling back the film upon gripping between the fingers a tab protruding from the film. When the user has finished, typically they will fold the film back over the rim of the body portion and replace the lid to fit over the base portion. Alternatively, the film may be completely torn away from the body portion and thrown out, in which case the user replaces the lid portion to fit over the body portion. In either situation, food contamination and degradation is highly likely as the food produce is not sealed completely from air. The metal film does not adhere to the rim of the body portion. Furthermore, the corresponding lids that

have a raised rib on an inner surface thereof, do not adequately seal the contents of the body portion.

The present invention provides a method of sealing a container without the need for an intermediate film between a body portion and lid portion of such a container.

Accordingly, in one aspect the present invention provides a method of sealing a container, having a body portion and a lid portion, said method comprising the steps of : bringing said body portion and said lid portion into co-operative juxtaposition such that said lid portion is positioned to seal an opening of said body portion; joining said body portion and said lid portion to form a seal between said body portion and said lid portion; providing a cut in said body portion such that the cut defines a tear line within said interface from which said lid portion may be detached from said body portion.

The seal is preferably formed at the interface of the rim portion of said body portion and the corresponding portion of said lid.

The step of joining the body portion and the lid portion may occur at respective interfaces and/or at respective rims of said body portion and lid portion. The cut is preferably located adjacent an inner side of said body rim portion. The step of joining of the body portion to the lid portion may be discontinuous around the rim on respective rims of said body portion and lid portion or a combination of a series of joins separated by sections not joined and a continuous join adjacent said cut but between the side of said body rim portion and said cut.

The method may further include the step of providing for re-sealing of the container by attaching the lid portion to the body portion such that an interference fit is created between said lid portion and said body portion. The interference fit may be

on an interior surface of said body portion adjacent said body rim portion and consist of a series of interlocking ribs and grooves between the lid portion and the body portion.

The step of joining may be performed by any means including welding, gluing or thermal bonding but is most preferably ultrasonic welding.

The present invention also provides a container, having a body portion and a lid portion, said body portion and said lid portion being adapted for co-operation and joining so as to form a seal such that the contents of said body portion is sealed, wherein said body portion has a cut formed therein, said cut defining a tear line from which said lid portion is detachable from said body portion to break said seal.

The seal is preferably formed at an interface of the rim portion of said body portion and the corresponding portion of said lid.

The body portion and lid portion may be joined at respective interfaces and/or at respective rims thereof. Said cut is preferably located adjacent an inner side of said body rim portion. The body portion and lid portion may be joined continuously or discontinuously around their respective rims or a combination of continuous and discontinuous joining around their respective rims.

The container may be resealed after the tear line has been broken whereby the lid portion is fitted to the body portion in an interference fit. The interference fit may be formed between an interior surface of said body portion adjacent said body rim portion and an interior surface of the lid portion and comprise a series of interlocking ribs and grooves between the lid portion and body portion.

In another aspect of the invention, there is provided a container having a body portion and a lid portion,

said body portion and said lid portion being joined to form a seal so as to seal contents of said body portion, the body portion having a cut formed therein, said cut defining a tear line from which said lid portion may be partially detached from said body portion to break said seal.

The lid portion may have a fold line, so that on breaking the seal between said lid portion and said body portion, the lid portion may be folded or bent on said fold line to permit access to the contents of said body portion. The container may thereafter be resealed by closing said lid portion such that an interference fit is created between the lid portion and the body portion.

One particularly preferred embodiment of the invention will now be described with reference to the drawings wherein: Figure 1 is an elevation view of a container with a lid portion fitted to a body portion of the container; Figure 2a is an exploded view of the encircled portion of Figure 1 with the lid portion and body portion about to be joined at an interface of their respective rims.

Figure 2b shows the container about to the subjected to a welding process; Figure 2c shows the container lid and body portions being welded to each other; Figures 2d and 2e show alternative joining arrangements from the welding process; Figure 2f shows the container in a sealed form; Figure 2g shows a container that has the lid portion removed from the body portion;

Figure 3 is a plan view of a container having lid portion and body portion joined at particular locations around rim portions of the lid and body portions.

Figure 4 is a plan view of a container having a lid portion, with a fold line, and body portion joined around rim portions of the lid and body portions on one side of the fold line.

Figure 5 (a) shows the container about to be subjected to a welding process wherein the lid portion has a ridge on its rim portion; Figure 5 (b) shows the container lid and body portions of Figure 5 (a) being welded to each other; Figure 5 (c) shows lid and body portions of a container with the body portion having a ridge on its rim portion.

In Figure 1, there is shown a container 1 having a lid portion 2 and body portion 4 fitted prior to sealing. The lid portion 2 and body portion 4 may be manufactured from any known type of plastic or similar material and each can be manufactured by any known method of polymer conversion, for example, injection molding, thermoforming, vacuum forming, blow molding, injection-blow molding, stretch- blow molding etc. The container 1 is shown in a suitably co-operative juxtaposition to allow the lid portion 2 to be joined or sealed to the body portion 4 such that the lid portion 2 seals an opening of body portion 4.

In Figure 2a, there is shown an exploded view of the encircled region of Figure 1 which more clearly shows the features of an interface 5 between the rim of the body portion 4 and the rim of the lid portion 2. In particular, Figure 2a shows a rim 6 of lid portion 2 having a second surface, being an upper surface 10 and a first surface, being a lower surface 12, and also showing a rim 8 of body portion 4

having a first surface, being an upper surface 14, and a second surface, being a lower surface 16. The lower surface 12 is in contact with upper surface 14 and forms the interface 5. The rim 6 also has an outer side 18 and inner side 20, the sides 18 and 20 extending downwardly from surfaces 10 and 12. Similarly, the rim 8 of body portion 4 has an inner side 22 and an outer side 24, both the sides 22 and 24 extending downwardly from surfaces 14 and 16. The outer side 18 and upper surface 10 of lid portion rim 6 form a continuous exterior surface 7 and inner side 20 and lower surface 12 of lid portion rim 6 form a continuous interior surface 9. Similarly, inner side 22 and upper surface 14 of body portion rim 8 form a continuous exterior surface 11 and outer side 24 and lower surface 16 form a continuous interior surface 13. Each of sides 20 and 22 are shown to have an interference fit through mating surfaces. Specifically, rib 26 protrudes or projects from side 20 of rim 6 and fits into a corresponding groove 28 on side 22 of rim 8.

Any number of grooves and corresponding ribs may be used. The grooves and ribs effectively provide a seal for the container so that the contents of body portion 4 are not contaminated or exposed to air. This has particular application after the container has been opened.

In Figure 2b, there is shown a horn 32 and an anvil 30 of an ultrasonic welding machine disposed either side of the two portions of the rims 6 and 8 that are to be joined and sealed. Each of horn 32 and anvil 30 will be shaped according to the shape of container required to be sealed, for example, if the lid portion 2 and body portion 4 are substantially circular then so too will horn 32 and anvil 30 be circular to fit to that shape. Anvil 30 has a spike projection 34 extending around an inner edge of the anvil 30 and this spike projection 34 is used to create a tear line which will be discussed with reference to the figures to follow.

In Figure 2c, the lower exterior surface 33 of horn 32 is brought into engagement with upper surface 10 of rim 6 and an upper exterior surface 35 of anvil 30 is brought into engagement with lower surface 16 of rim 8. The projection 34 now protrudes through the rim 8. It is to be noted that the projection 34 may extend

through a portion of the rim 8 or through the rim 8 and a portion of rim 6.

Ultrasonic welding takes place as seen in Figure 2 (d) where the rims 6 and 8 are joined to form a seal as indicated by the cross hatching. The welding takes place at a frequency of about 20kHz. The particular method of sealing is not limited to using the ultrasonic welding but can use any one of a number of bonding methods including using adhesive, hot plate welding, hot plate welding with adhesive, spin welding, spike welding, ultrasonic welding with adhesive or laser welding. The welding need not be continuous around the rims but may be intermittent, that is, there may be portions of each rim that are welded together separated by portions of the rim that are not welded together.

In Figure 2e, an alternative welding arrangement is shown whereby a seal is created along a major portion of the two surfaces 12 and 14 at interface 5 apart from a region 36 adjacent cut 38. The cut 38 was formed from the projection 34 of anvil 30 and this cut extends around the entire rim 8. A tear line or score line 40 is created by the cut 38 where a thin seal or weld extends along this tear line between the two rims. The process of creating the cut 38 and tear line 40 is called coining.

Again, the ultrasonic welding used to create the tear line 40 may be a continuous weld or an intermittent weld but is preferably a continuous weld. It is a matter of choice as to how the welds are to be formed, whether they are continuous or intermittent, depending on the available energy from the ultrasonic welding machine and also as to how much steam must be removed during the process whereby steam is expelled through the portions where no welding has taken place.

After the welding process the horn 32 and anvil 30 are removed from the rims 6 and 8 and in Figure 2f a seal has now been created between the lid portion 2 and body portion 4. To remove the lid portion 2 from the body portion 4, vertical pressure is applied by a user such that the tear line 40 is allowed to break on either the lid portion 2 or the body portion 4.

In Figure 2g, the lid portion 2 shown is completely separated from the body portion

4 where the seal has been broken at 42. The contents of the body portion 4 can now be accessed and when the user is finished the container can be resealed by downward pressure of the lid portion 2 onto the body portion 4 so that ribs 26 fit into corresponding grooves 28 to create the resealing of the contents.

Figure 3 shows in plan view the cross hatched areas where welding has taken place. As can be seen, a thin weld has taken place around the whole periphery of the rims of the region between cut 38 and where the inner parts of rims 6 and 8 join and on the other side of cut 38, major welding has taken place intermittently.

An alternative arrangement is to have the cut 38 extending only along a portion of the rims 6 and 8 with the remaining portion being completely sealed and having no cut 38. This is to allow for possibility of only partially opening or removing the lid portion 2 from body portion 4. Lid portion 2 would be able to bend around a fold line to access the contents in body portion 4 and after use is allowed to be resealed in the manner previously described where ribs 26 engage corresponding grooves 28 between the side portions of rims 6 and 8. By way of example referring to Figure 4, there is shown a fold line 44 extending across the perimeter 45 of lid portion 2. The cut 38 extends along interface 5 between the rims 6 and 8 of lid portion 2 and body portion 4 on one side of the fold line 44 between the ends of the fold line 47 and 49. Score line 40 also extends on the same side as the cut 38 along the rims 6 and 8 between end points 47 and 49. On the other side of the fold line 44 a continuous welding process has occurred to join the respective rims of the lid portion 2 and body portion 4.

Therefore a user may apply vertical pressure to the region 50 of lid portion 2 such that tear line 40 is allowed to break on either the lid portion 2 or body portion 4 along respective rims 6 or 8 on that side of the fold line 44. Once the seal is broken the region 50 is folded back on itself along fold line 44 to provide access to the contents of body portion 4. The region 52 on the other side of the fold line 44 remains in tact so that the lid portion 2 is only partially opened by the folding of

region 50. The region 50 of lid portion 2 may be re-sealed by applying downward pressure onto the body portion 4 so that ribs 26 engage with corresponding grooves 28 previously described.

Shown in Figure 5 (a), the lower surface 12 of rim 6 has a protrusion 46 in the form of a ridge extending outwardly and downwardly of lower surface 12. As the anvil 30 and horn 32 are brought into engagement with upper surface 10 of rim 6 and lower surface 16 of rim 8 respectively the welding process commences such that the ridge 46 assists in concentrating the energy derived through the welding process. The ridge 46 directs the energy to provide a more consistent weld or join at the interface 5 between the lid portion 2 and body portion 4. Energy is initially directed through the ridge 46 and then into the gap 51 such that the energy is directed outwardly from point 53 and the gap 51 is eventually filled by the bonding between the rims 6 and 8 at the interface.

Shown in Figure 5 (c) is an alternative to providing a ridge on lower surface 12 of rim 6. Instead a protrusion 48 in the form of a ridge extends outwardly and upwardly from upper surface 14 of rim 8 of the body portion 4. A similar process as just described occurs when welding is about to commence to join rims 6 and 8 as is shown in Figure 2 (d). Alternatively, a ridge may be provided on both surfaces 12 and 14 respectively to provide a more consistent weld or join between the rims 6 and 8. The ridge 46 or 48 may extend around the entire surface 12 or 14 respectively or be intermittent such that it occurs in particular areas around those surfaces 12 and 14.

The present invention provides a unique method of sealing a container that can easily show evidence of tampering. The container so formed may be resealed to prevent contamination of the food produce stored in the container and does not require an intermediate film between a body portion and lid portion of the container.