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Can endRelated Patent Categories: Food Or Edible Material: Processes, Compositions, And Products, Packaged Or Wrapped Product, Packaging Structure Cooperating With Food Generated GasCan end description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070071856, Can end. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD [0001] The present invention relates to a pressurised can and in particular, to an end suitable for use on a pressurised food can. In a pressurised food can, the food product is inserted into the can and stored therein under pressure. The increased pressure in the can is achieved by pressuring the headspace above the food product. BACKGROUND ART [0002] Pressurisation of the headspace may be achieved in a number of different ways. For example, a droplet of liquid, inert gas may be inserted into the can prior to sealing with the end, as described in US 289844 PABST BREWING COMPANY) The liquid then evaporates and the resultant gas pressurises the headspace. Alternatively, after sealing, a portion of the can may be irreversible pushed inwardly to similarly pressurise the headspace gases by forced reduction of the volume of the headspace. This technique is described in EP 0521642 B (CMB FOODCAN) DISCLOSURE OF INVENTION [0003] The advantage of pressuring a can is that the can may be made of substantially thinner gauge metal, which is deformable under normal conditions. The internal pressure in the pressurised can supports the walls of the can, providing the rigidity required for handling and transport. [0004] However, a can whose contents are held under pressure has the disadvantage that upon first opening, the pressure inside the can is rapidly released to the atmosphere and the stream of released gases may carry a quantity of product. This problem is referred to as "spurting" and is highly undesirable for the consumer. In extreme circumstances, such "spurting" may have explosive force making the can dangerous. The present invention is concerned with mitigating or even eradicating "spurting", upon first opening of a pressurised can. [0005] Preferably, the volume of the headspace (the fee space between the surface of the product and the can) is minimised. This reduces the volume of pressurised gas released from the can upon first opening. However, the inventors have found that the height of the headspace at the point of first opening (i.e. the point at which the can is exposed to atmospheric pressure) needs to be maximised. The height of the headspace at the point of first opening has been found to be critical in determining whether the can will "spurt" when opened by a user. [0006] Conventional food cans comprise a hollow body, in which the product is stored, and at least one end, which is connected to the free edge of the body, conventionally by seaming and in particular by a technique known as double seaming. Conventional ends comprise a flat plate-like centre panel connected to a seaming portion (often referred to as the "cover hook") via a chuck wall, which-supports a seaming chuck during the double seaming process. At the base of the chuck wall a concave reinforcing bead (looking from the outside of the can) is normally provided, to strengthen the end and support the seam. Conventional can openers first pierce the can at a point adjacent to or lying within the reinforcing bead. Further shallow beads may also be provided on the wall of the can body and/or on the end, to strengthen the can. [0007] Accordingly the invention provides a pressurised can comprising a sealed vessel having an access region at which the sealed vessel is first opened, and a product defining o product surface and a head space, the product confined within the sealed vessel with the headspace arranged in fluid communication with the access region, characterised in that the sealed vessel is adapted to minimise the volume of the headspace, whilst maximising the height of the headspace above the product surface at the access region. [0008] Conventionally, the volume of the headspace in a can is minimised because any volume in the can not used for product is wasteful of space and poorly perceived by consumers. In a pressurised can, the volume of the headspace is particularly important, because this "space" contains the pressurised gas, which pressurises the can and has to be released into the atmosphere on first opening of the can. The inventors have found that the height of the headspace at the point of first opening is particularly important to the spurting properties of the can and should be maximised to reduce the risk of unacceptable spurting. Thus, the design of the can will involve a trade-off between minimising the volume of the headspace for the reasons discussed above and maximising the distance between the surface of the product and the point of first opening of the can, to reduce the chances/level of spurting. This may be achieved by increasing the height of the headspace within an access region, whilst reducing the height/volume of the headspace outside the access region. [0009] Where a can is opened using a conventional can opener or where the can end is a so-called "easy-open end" (i.e. EOLE.RTM.), the can is conventionally opened towards the peripheral edge of the can end. In this situation, the central portion of the end may be indented so that it lies closely adjacent to or even touching the surface of the product. This allows the headspace volume to be minimised whilst ensuring that the height of the headspace at the point of first opening is sufficiently large to prevent or at least significantly reduce the level of spurting. [0010] The inventors carried out a number of tests using conventional cans having two different types of end (EOLE.RTM.--Easy Open End and NEO--Non-easy Open End), different levels of headspace pressurisation and a height of headspace at the point of first opening of 8 mm. A headspace height of 8 mm was chosen as a good average of the headspace height provided in most conventional food cans. All tests were carried at an ambient temperature of 25.degree. C.; the filled cans were allowed to stand for at least 1/2 hour before opening and NEO samples were opened using a Standard Butterfly can opener. The level of spurting from the can upon first opening was recorded by holding a sheet of white paper above the end of the can to catch any splatter of product, which was ejected. This test is referred to as the white glove test (WGT). The test is intended to represent the degree of "spurting" that a user would experience, if opening the can whilst wearing white gloves. The test is considered successful, if the user could open the can, with no marks damaging the gloves. The results of the tests are shown in Table 1 (below). TABLE-US-00001 TABLE 1 Headspace Pressure Height Can End Type psi (bar) (mm) Product WGT Comments 1 EOLE 5 (0.34) 8 Water Fail Droplets ejected 2 EOLE 5 (0.34) 8 Water Pass 3 EOLE 5 (0.34) 8 Water Pass 1 EOLE 10 (0.69) 8 Water Fail Droplets ejected 2 EOLE 10 (0.69) 8 Water Fail Spurt of water 3 EOLE 10 (0.69) 8 Water Fail Spurt of water 1 EOLE 15 (1.03) 8 Water Fail Big spurt of water 2 EOLE 15 (1.03) 8 Water Fail Explosive opening 3 EOLE 15 (1.03) 8 Water Fail Big spurt of water 1 NEO 5 (0.34) 8 Water Pass 2 NEO 5 (0.34) 8 Water Fail Spurt of water 3 NEO 5 (0.34) 8 Water Fail Spurt of water 1 NEO 10 (0.69) 8 Water Pass 2 NEO 10 (0.69) 8 Water Fail Spurt of water 3 NEO 10 (0.69) 8 Water Fail Big spurt of water 1 NEO 15 (1.03) 8 Water Pass 2 NEO 15 (1.03) 8 Water Fail Big spurt of water 3 As NEO 15 (1.03) 8 Water Fail Big spurt of water [0011] As shown by these results, even at the lowest level of pressurisation of 5 psi (0.34 bar) "spurting" is problematic, for both types of ends. At higher levels of pressurisation, "spurting" becomes unacceptable. [0012] The same series of tests were then carried out for a headspace height at point of first opening of 12 mm and headspace pressurisation of 10 psi (0.69 bar) and 15 psi (1.03 bar), again using the same type of conventional cans and ends. The results of these tests are shown in Table 2. TABLE-US-00002 TABLE 2 Headspace Pressure Height Can End Type psi (bar) mm Product WGT Comments 1 EOLE 10 (0.69) 12 Water Pass No spurt/No water 2 EOLE 10 (0.69) 12 Water Pass No spurt/No water 3 EOLE 10 (0.69) 12 Water Pass No spurt/No water 1 EOLE 15 (1.03) 12 Water Pass No spurt/vapour? 2 EOLE 15 (1.03) 12 Water Fail Water ejected 3 EOLE 15 (1.03) 12 Water Pass No spurt/No water 1 NEO 10 (0.69) 12 Water Pass No spurt/droplets 2 NEO 10 (0.69) 12 Water Pass No spurt/droplets 3 NEO 10 (0.69) 12 Water Pass No spurt/droplets 1 NEO 15 (1.03) 12 Water Pass No spurt/droplets 2 NEO 15 (1.03) 12 Water Pass No spurt/droplets 3 NEO 15 (1.03) 12 Water Pass No spurt/droplets [0013] By comparison of the results from Tables 1 and 2 above, it can be seen that a headspace height of 12 mm at the access region/point of first opening significantly reduces the level of spurting for both EOLE and NEO ends. As expected, lower pressurisation of the headspace results in lower levels of spurting. [0014] This theory works well for liquid products (i.e. water) or products held in a liquid (vegetables in brine, for example), but further problems have been identified with more viscous products (chilli con carne and pet food, for example). When these products are agitated during transport, handling etc. or stored in an inverted position, it takes longer for the product to settle with the headspace in communication with the access region and in some cases this may never occur. In these circumstances, it is likely that at least some product will be retained within the access region, having the larger headspace height at the point of first opening. Consequently containers filled with such viscous products, have been found to spurt upon first opening of the container, despite the can having a maximised headspace height at this point. [0015] In order to gain a better understanding of this phenomenon, a transparent can was filled with various products, to observe the effect of the product on opening of the can. The surface tension of thicker products was observed to cause the product surface to creep up the sidewall of the can, reducing the overall headspace height at the point of first opening. [0016] However, the same surface tension forces of these thicker products can also be used to mitigate this problem, by the careful placement of attraction features within the headspace but outside the access region. If an indentation is provided extending into the headspace of the can, so that it touches or approaches close to the surface of the product, such viscous products will tend to be attracted to the indentation, which acts as an "attraction feature" and draws the product away from the access region, leaving the height of the headspace at the point of first opening largely unobstructed. [0017] Furthermore, the meniscus formed on the surface of a the product has been found to make a "meniscus jump" toward such attraction features, even when they are not in contact with the product surface. Thus, the attraction feature will still draw product away from the access region, increasing the headspace height in this region, providing that it extends far enough towards the product surface to allow the meniscus to make a "meniscus jump" towards it The viscosity and composition of the product will determine the size of gap between the product surface and the attraction feature and therefore the size of "meniscus jump" that the product surface will make. [0018] In an alternative embodiment the can/end are adapted, so that upon first opening (regardless of the headspace height/volume when the can was filled) the can/end accommodates a volume increase of the headspace and the can does not vent to the atmosphere until the end is lifted a predetermined height above the surface of the product. This may be achieved by providing a threaded can/end, in which the thread profile is modified to allow the end to be lifted relative to the can body before finally being unscrewed and the headspace vented to the atmosphere. [0019] This arrangement has several advantages. The can may be filled to conventional fill heights leaving a headspace, which is pressurised. During opening, a user simply unscrews the end. The thread profile is modified so that during unscrewing, the end is first raised relative to the can body without venting to atmosphere. This increases the volume of the headspace, thereby relieving some of the internal pressure in the can. Also, the height of the headspace is increased before the can is first opened (i.e. when the headspace gases vent to atmosphere) is raised. Both these effects minimise "spurting". BRIEF DESCRIPTIONS OF THE DRAWINGS [0020] FIG. 1 shows a side section through a conventional food can having a non-easy open end (NOE), identifying the height of the headspace (h) at the point of first opening. Continue reading about Can end... Full patent description for Can end Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Can end patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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