CANS OR GROUPS OF CANS FOR FOOD PRODUCTS WITH A HYGIENIC PROTECTION; METHOD AND APPARATUS THEREFOR

Abstract: A can capping method comprises the following operational stages: a film of thermoformable plastic material (9) is heated and placed on the upper portion (11) of a group of cans comprising at least one can (10), the film is made to adhere by mechanical means to the surface of said upper portion in correspondence with a closed line, to define a closed chamber in combination with said upper portion; the air is extracted from said chamber; the film surface is made to adhere completely to said upper portion; that film portion adhering completely to the upper portion of the group of cans is separated from the rest of the film; said film being heated to a suitable temperature such that the film, on shrinking as a result of cooling, remains adhering to the surface of said upper portion and retains its shape.

Description: Description CANS OR GROUPS OF CANS FOR FOOD PRODUCTS WITH A HYGIENIC PROTECTION; METHOD AND APPARATUS THEREFOR Technical field This patent concerns the hygienic protection of container cans for food products and drinks, and in particular drink cans having in their upper end a tear-off opening through which the drink is consumed, possibly by bringing the can directly to the mouth. Background art The widespread practice of conserving drinks in cans has raised the general problem of safeguarding the health of the user. In this respect, after being filled, the cans are transported and stored without it in practice being possible to protect them from dust or other more dangerous contaminants, making the consumption of the liquid highly anti-hygienic whether the liquid is poured into a tumbler, or, much more serious, whether the user drinks it directly from the can. The situation is further aggravated by the appearance of cans in which the opening tab is not pulled off, but instead bent down into the interior of the can, into direct contact with its contents. There is therefore the need to protect the can upper end containing the opening tab from dust and other contaminants. An object of the present invention is to rationally satisfy the aforesaid requirement without substantially affecting the canning cost. A further object of the present invention is to provide packaging means for at least two cans arranged to provide packs of at least two cans held together by a single support sheet, while at the same time protecting their lids from contamination. Disclosure of the invention The invention is based on the solution of directly forming on the upper portion of the can, by basically using this as a forming die, a cap of food-quality plastic material which "hermetically" covers this upper portion. The method of the invention comprises heating a film of thermoformable plastic material and positioning it on the upper portion of the can, then making it adhere to the surface of said upper portion by extracting the air contained between this surface and the film. Finally, the film portion adhering to the can upper portion is separated from the rest of the film. During the described procedure, the film is heated to a suitable temperature such that the film is able to satisfy the conditions for thermoformability, after which, by shrinking following cooling, it adheres intimately to the surface which it covers, and retains its shape. A cap is obtained formed from a film portion which mates with and covers the surface of the upper portion of the can. This cap, which can be easily and rapidly removed by the consumer, covers, and effectively and hermetically protects from dust and any other contaminant, the region comprising the can opening and the entire can upper part and upper edge contacted by the lips, so maintaining this in a positively hygienic condition. Moreover, after the can has been opened, the same cap can be further used to close the can and hence prevent accidental contamination by foreign bodies. Said cap forming procedure is very rapid and does not retard the production rate of the canning line in which it is inserted. Moreover the apparatus required for effecting the procedure is relatively very simple and of low cost. The merits and the constructional and functional characteristics of the invention will be apparent from the detailed description given hereinafter of two preferred embodiments thereof given by way of non-limiting example and illustrated in the figures of the accompanying drawings. Figure 1 is a section through the apparatus of the invention taken on a longitudinal vertical plane. Figures 2 to 5 show an enlarged detail of Figure 1 , in successive stages of the method of the invention. Figure 2A is a section on the plane II—II of Figure 2. Figure 6 is an enlarged detail of Figure 3. Figure 6A is a further enlarged detail of Figure 6. Figure 7 is an enlarged detail of Figure 4. Figure 7A is a further enlarged detail of Figure 7. Figure 8 is a section through the upper portion of the capped can. Figure 9 is a partly sectional schematic side view of a further embodiment of the apparatus according to the invention. Figure 10 is an enlarged detail of Figure 9, shown in a subsequent operating position. Figure 11 shows the detail of Figure 10 in the next operating position to that of Figure 10. Figure 12 shows the detail of Figure 10 in the next operating position to that of Figure 11. Figure 13 shows the detail of Figure 10 in the next operating position to that of Figure 12. Figure 14 shows the detail of Figure 10 in the next operating position to that of Figure 13. Figure 15 is similar to Figure 14, but with a different type of cutting blade. Figure 16 is a section through a pack of two cans resulting from the preceding operations. Figure 17 is a view from above showing the can-containing tray illustrated in Figure 9. Figures 18 to 20 are views from above showing packs respectively of two, three and four cans obtained by the apparatus of the invention. An apparatus and relative method for capping individual cans are described hereinafter with reference to Figures 1 to 8. The can, indicated by 10 in the figures, is of known type. Specifically, it comprises an upper portion 11 formed from the substantially flat top end 12 of the can, its upper frusto-conical neck 13 and the circular rim 14 which joins the end 12 to the neck 13 (see specifically Figure 8). The illustrated apparatus comprises a backing plate 21 with a plurality of circular through apertures 22, each of which can receive with slight clearance the upper portion 11 of a relative can 10. Specifically, each aperture 22 is defined by a ring 23 positioned in a seat 23a in the plate 21 and forming an integral part of the plate, to act as an "adaptor", ie it is changed for different can diameters (Figures 6, 6A, 7, 7A) . The plate 21 is carried by a lower support plate 25 having a plurality of circular through apertures 26, each of which is positioned coaxially to a respective aperture 22 and is arranged to house with slight clearance that can portion below the upper portion 11. Each aperture 26 is defined by a sleeve 27 positioned in a seat 27a in the plate 25 and forming an integral part of the plate, to act as an "adaptor", ie it is changed for different can diameters. The plurality of cans 10 on which the apparatus of the invention operates during each cycle are carried by a loader tray 15 provided with a corresponding plurality of seats 16 housing as virtually an exact fit the lower portions of the cans 10. The seats 16 are geometrically arranged relative to each other so as to be coaxial to the apertures 22. The loader 15 is subjected to movement means (of known type, not shown) which arrange the plurality of cans 10 in correspondence with the apertures 22, such that the can upper portions 11 project beyond the upper surface of the plate 21. Above the plate 21 there is positioned a grid 31 comprising a plurality of walls 32 having their numerous lower edges facing downwards to define a corresponding plurality of apertures. Each of these apertures is arranged to coaxially surround a corresponding aperture 22 in the backing plate 21 , the lower edge of the walls 32 being able to be lowered into contact with the upper surface of the backing plate 21. Above the upper portion 11 of the cans and below the grid 31 there is positioned a web of undefined length of a film 9 of thermoformable plastic material of a type suitable for foods, such as HiPS, PP, PET, PVC, PE or PS. The film web 9 is unwound from an initial reel 8 and is wound (as scrap) onto a final reel 7, it being kept guided by suitable means (shown schematically in Figure 1). The grid 31 is moved by means (of known type, not shown) which press it against the upper surface of the backing plate 21 , with the film 9 interposed. To the upper end of each sleeve 27, on its inside, there is fixed a gasket 28 arranged to make contact with the lateral surface of the can 10, in particular with its frusto-conical neck 13, to produce a seal during the suction stage. In addition, the upper end of the sleeve 27 forms radial channels 271 (Figure 6A) which, together with small radial ducts (not shown in the figures), connect that region surrounded by the apertures 22 to pump means (not shown in the figures) for drawing air from said region (as further described hereinafter). Above the plate 21 , within the apertures defined by the grid 31 , there are positioned a like number of presser means 40, having a vertical support shank 41 to which there is lowerly fixed a plate 42 carrying a lower layer 43 of yieldable material, with which it presses against the upper end 12 of the can 10. Springs 44, positioned about the shanks 41 , provide the downward force with which the pressers 40 press on the can 10. Above the plate 21 there are positioned a plurality of cylindrical blades 50 (or punches), each positioned coaxially about a respective presser means 40 and driven in a vertical direction by known means, not shown in the figures. The cutting edge 51 of each blade 50 faces downwards and has a closed contour arranged to pass about the upper end 12 of the can 10 and to skim the upper edge of the aperture 22 so that in combination with this edge it cuts the film 9 (as further described hereinafter). The aforedescribed apparatus implements the following procedure. At the commencement of each capping cycle, a plurality of cans 10 are loaded onto the loader 15, this then being positioned below the plates 21 and 25 (Figure 1). In the meantime the grid 31, the pressers 40 and the blades 50 are raised to be spaced from the plate 21. A hole-free continuous portion of the film 9 is heated by means 4 located upstream of the plate 21 , and is immediately afterwards advanced to above the plate 21. Advantageously, the means 4 are infrared radiation means, heating the portion of film 9 to a temperature of between 120°C and 230°C, according to the polymer type. At this point the loader 15 is raised to position the upper part of the cans 10 through the apertures 22 and 26, and urge them slightly upwards to press their neck 13 into contact with the respective gaskets 28. When in this position the upper portion 11 of the cans projects slightly beyond the upper surface of the plate 21. The combination of the loader 15 and plates 21 and 25 is then moved upwards so that the upper end 12 of the cans skims the film 9 (Figure 2). In the next stage (Figure 3) the grid 31 and (virtually simultaneously) the pressers 40 are lowered to press the heated portion of film 9 against the upper end of the cans 10 and against the upper surface of the backing plate 21. The lower edge of the walls 32 presses on the film 9 against the upper surface of the plate 21 , to create a circular seal strip through which air does not pass. Consequently, in correspondence with each aperture 22 an interspace is formed between the film 9 and the can upper portion 11, which is isolated from the external environment. In detail, this interface is bounded lowerly by the surface of the can upper portion 11, as far as the point in which this is in contact with the gasket 26. Upperly it is bounded by that portion of film 9 surrounded by the lower edge of the walls 32, by that part of the upper surface of the plate 21 (ring) surrounded by said edge of the walls 32, and by the inner surface of the apertures 22. Lowerly, this interspace is bounded by the gasket 28. During this stage, the air present in the interspace is extracted through the channels 271 and the other channels (not shown) by said pump means, and consequently the portion of film 9 surrounded by the wall 32 adheres hermetically to the outer surface of the can upper portion 11 (and also to the upper surface of the ring 23) to give rise to a cap 9a, which for the moment is still joined to the remaining part of the film 9, but exactly matches the form of the upper portion 11. This adhesion action is further aided by the pressers 40, the yieldable layer 43 of which presses the film against the upper end 12. In the next stage (Figures 4, 7 and 7A) , the blades 50 are lowered to graze the upper edge of the apertures 22 with their cutting edge 51 , and then produce a corresponding closed circular cut in the film 9, to separate the film portion adhering to the can 10 (cap 9a) from the remainder of the film 9. The cans 10 are then lowered by lowering the loader 15 and aided by the pressers 40 which press downwards against the cans, and are finally removed (Figure 5). The grid 31, the blades 50 and the pressers 40 are raised away from the plate 21 , and the described cycle recommences to cap further cans. On cooling, the cap 9a completes its shrinkage against the surface of the upper portion 11, to adhere to and exactly mate with its outer form, and then permanently retains this assumed shape. Moreover the cap 9a adheres under vacuum to the can surface, hence covering it hermetically to securely protect it from any external contaminant . With reference to Figures 9 to 20, the method and apparatus for capping groups of cans will now be described. The figures show a conveyor 91 driven stepwise, and on which equidistant trays 92 are arranged in succession. The trays 92 are best seen in Figure 17, and comprise a base with uniformly distributed recesses 93 to each receive a group of cans 94 to be formed into a pack. More precisely, each recess 93 has in plan view a shape representing the envelope of the group of cans, and from its base there upwardly extend partitioning baffles 931 occupying the space which would otherwise remain free between one can and the next, said baffles having a height equal to the height of the cylindrical part of the cans. The conveyor belt 91 carries the trays to a processing station 95, where it is supported by an underlying support surface 911. Above the station 95 there is a first vertically movable plate 96 having in plan view the same shape as the underlying tray 92 and comprising through apertures 961 which correspond to the recesses 93 and have the same shape as these latter. Alternatively the clamping plate 96 is fixed, and that conveyor portion supporting the tray 92 is movable to raise the tray to below the clamping plate. The plate 96, which will be called the backing/centering plate, comprises channelling 962 communicating with a vacuum vessel or vacuum pump, neither shown, and a lattice of gaskets 963 which surround the through apertures 961. To the plate 96 there is upperly fixed a thin steel blade 97, which is perforated as the plate 96 and is provided with hardened sleeves 971 positioned to circumscribe each of the through apertures 961. The plate 96 and relative blade 97 are overlaid by a second vertically movable plate 98 carrying the operating means described hereinafter. A film pressing grid 981, movable relative to the plate 98, is fixed to the lower side of the plate 98 and, when lowered, rests on the blade 97. The plate 98 also carries a series of shanks 982 which are provided with a base disc 983 and are coaxial to the seats defined by the underlying recesses 93 and baffles 931 so that each of the discs 983 is able to descend and press against the lid of a can 94. The shanks 982 are contained in through apertures 984, conjugate with the underlying apertures in the centering plate but slightly wider than these latter. Each of the apertures 984 carries a downwardly projecting cylindrical blade 985 having a closed contour circumscribing at a short distance therefrom the edge of the through apertures 961 , and arranged to interact with the sleeves 971 of the blade 97. In the embodiment shown in Figure 1 4 the blade 985 rests on the sleeves 971 . If the fiim 991 is substantially rigid so as to hinder can removal or cause separation of the shaped film portion which caps the cans, the embodiment shown in Figure 15 is preferable, in which the blade 985 enters the sleeve 971 as an exact fit, to act as shears . The apparatus also comprises a device carrying a reel 99 of thermofor able film 991. After unwinding from the reel 99 the film passes through the station 95 immediately above the blade 97 and is rewound as scrap on a reel 912 positioned downstream. A tunnel 913 for heating the film 91 is provided between the reel 99 and the station 95. The aforedescribed apparatus is able to implement the following method, the description of which will also clarify the operation of the apparatus. A succession of trays 92 already carrying cans 94 in their recesses 93 are loaded onto the conveyor belt 91. Advancement of the belt 91 is intermittent and is such that it halts with the tray positioned in the station 95, with the recesses 93 always perfectly aligned with the through apertures 961 of the overlying centering plate 96. When the belt 91 halts, the plate 96 descends until it rests in a sealed manner, by virtue of the gaskets 963, on the underlying tray 92, as shown in Figure 10. Alternatively, as stated, the backing plate portion 911 raises the portion of the conveyor 91 to bring the tray 92 below the fixed plate 96. At this point the fiim pressing grid 981 descends from the plate 98 to spread the taut film 91 over the end parts of the cans 94 which project beyond the blade 97 of the plate 96, as shown in Figure 11. After the descent of the grid 981 , the discs 983 are made to descend to press the film onto the lid of the cans, as in Figure 12, to cause the film 91 to perfectly adhere to the upper part of the cans, after which the connection between the channelling 962 and the vacuum chamber is opened. The subsequent descent of the plate 98 with the blades 984 causes separation from the film 91 of that part adhering to the cans, as shown in Figure 13. On termination of the cycle, all the devices return to their initial position, as shown in Figure 14, the cans arranged in each recess of the tray 92 being joined together by the film 91 which surrounds their end parts as shown in Figure 15. In the illustrated example the plate 96 and the underlying tray 92 have the shape shown in Figure 16 for forming two-can packs. It is however apparent that the trays and the plates 96, 97 and 98 can be of any shape for forming multi-can packs, as shown in Figures 17, 18 and 19. From the aforegoing it is apparent that, by virtue of the described apparatus, can group packs can be formed without interrupting the flow of the can processing line, by simply inserting the apparatus into the line. This constitutes one of the many merits of the invention, in that the insertion into the line avoids rehandling the products for their packing and further manipulation, to the advantage of production costs. It should also be noted that with the same apparatus, cans of different height but of equal cross-section can be packed by simply adjusting the distance between the conveyor 91 and the unit formed by the plates 96 and 98 plus relative accessories.

Claims: Claims 1. A can capping method, characterised in that a film of thermoformable plastic material is heated and placed on the upper portion or a group of cans comprising at least one can; - the film is made to adhere by mechanical means to the surface of said upper portion in correspondence with a closed line, to define a closed chamber in combination with said upper portion; the air is extracted from said chamber; the film surface is made to adhere completely to said upper portion; that fiim portion adhering completely to the upper portion of the group of cans is separated from the rest of the film; said film being heated to a suitable temperature such that the film, on shrinking as a result of cooling, remains adhering to the surface of said upper portion and retains its shape. 2. A can capping method as claimed in claim 1, characterised in that the plastic material film is heated before being placed on the upper portion of the group of cans. 3. A can capping method as claimed in claim 1, characterised in that that film portion adhering to the can upper portion is separated by cutting along a closed line which closely surrounds the upper end of the can. 4. A method as claimed in claim 1, characterised in that that film portion adhering to the upper portion of the group of cans is separated by cutting along a closed line which surrounds on the outside the line constituting the envelope of said upper portion. 5. An apparatus for capping, as a single pack, groups of cans comprising at least one can, characterised by comprising: at least one tray provided with recesses arranged to each receive a group of at least one can, each recess being provided with a partitioning baffle which occupies the space left free between the outer walls of the cans and the inner wall of the recess ; an overlying backing/centering plate with a plurality of through apertures, each arranged to receive, with slight clearance, the upper portion of the groups of at least one can contained in the underlying tray; means for arranging said tray in correspondence with said backing/centering plate in a position such that the upper portion of the groups of at least one can contained in the tray projects beyond the upper surface of the backing/centering plate; means for arranging a web of plastic film above the backing/centering plate and above the projecting upper portion of the groups of at least one can; - grid means defining a corresponding plurality of apertures, each arranged to surround a corresponding aperture of the centering plate, the lower edge of said grid means being arranged to press the film against the upper surface of the centering plate; - between said centering plate and said tray, pneumatic seal means which surround the recesses containing the groups of at least one can; means for putting the chambers formed by the recesses and the overlying film under vacuum; and - means for cutting said film in proximity to the outer edge of said through apertures of the centering plate. 6. An apparatus as claimed in claim 5, characterised in that each recess contains only one can. 7. An apparatus as claimed in claim 6, characterised in that the pneumatic seal means act between the backing/centering plate and the neck of the can. 8. An apparatus as claimed in claim 6, characterised in that the pneumatic seal means consist of an annular gasket. 9. An apparatus as claimed in claim 5, characterised by comprising yieldable presser means for pressing the plastic film against the upper end of the cans. 10. An apparatus as claimed in claim 5, characterised by comprising, in correspondence with each aperture of the centering plate, a sleeve of hard material against which the film cutting means act. 11. An apparatus as claimed in claim 5, characterised in that the film cutting means are a plurality of vertically movable cylindrical blades, the cutting edge of which faces downwards and has a closed contour arranged to circumscribe at a short distance therefrom the edge of the through apertures of the centering plate. 12. An apparatus as claimed in claim 5, characterised in that the blade cutting edge rests on the sleeve to act as a punch. 13. An apparatus as claimed in claim 5, characterised in that the blade cutting edge enters the sleeve to act as shears. 14. A container can for food products and drinks, characterised by comprising a portion of film (9) which mates with and covers the surface of the can upper portion (11). 15. A group of at least two container cans for food products and drinks, characterised by comprising a single portion of film which mates with and covers the surface of the upper portion of the cans forming part of the group.

Inventors: GROPPI SILVANO, GROPPI, SILVANO
Applicants: C G R TECHNOLOGIES S R L, GROPPI SILVANO, C.G.R. TECHNOLOGIES S.R.L., GROPPI, SILVANO
Application year: 1997
Main classification: B65B17
IPC codes: B65B17, B65D51, B65D71