Patent Publication Number: US-6336309-B1

Title: Method and apparatus for providing hygenic protection on cans or groups of cans

Description:
This application is the national phase under 35 U.S.C. §371 of prior PCT International Application No. PCT/EP97/03716 which has an International filing date of Jul. 9, 1997 which designated the United States of America. 
    
    
     DESCRIPTION 
     Method and apparatus for capping, individually or in groups, container cans for food products and drinks, and cans or groups of cans capped in this manner. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention is directed to 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 direct to the mouth. 
     2. Background Art 
     The widespread practices 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. 
     The U.S. Pat. No. 5,088,269 discloses a method and an apparatus in which a film of thermoformable plastic material is applied to the tops of a plurality of cans. 
     The portions of the film overlying the top of the cans are softened by heating limited to the areas in alignment with the tops of the cans but smaller than the can tops. 
     The unsoftened areas of the film surrounding the softened areas are pushed in direction of the tops of the can and snap beneath the rim of the can lops, providing a cover which does not mate with the upper surface, or lid, of the can but is stretched at a distance therefrom resting on the rim. 
     The areas of the film distant from the lid are exposed to breakage while the cans are transported and stored, and the air contained in the sealed chamber under the film is subjected to condense and gives rise to highly anti-hygienic mildew. 
     The method and the apparatus of U.S. Pat. No. 5,008,269 do not fully satisfy the requirement of avoiding contamination. 
     There is therefore the need to protect the can upper end containing the opening tab from dust and other contaminants 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the present invention is to rationally satisfy the aforesaid requirement without substantially affecting the calming 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. 
     The present 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 present 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 exacting 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 hardening following cooling, it adheres intimately to the surface which it covers, and retains its shape. 
     A cap is obtained and 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, thereby maintaining this region in a positively hygienic condition. 
     Moreover, after the can has opened, the same cap can be further used to close the can and hence prevent accidental contamination by foreign bodies. The 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. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The merits and the constructional and functional characteristics of the present 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. 
     FIG. 1 is a section through the apparatus of the invention taken on a longitudinal vertical plane. 
     FIGS. 2 to  5  show an enlarged detail of FIG. 1, in successive stages of the method of the invention. 
     FIG. 2A is a section on the plane II—II of FIG.  2 . 
     FIG. 6 is an enlarged detail of FIG.  3 . 
     FIG. 6A is a further enlarged detail of FIG.  6 . 
     FIG. 7 is an enlarged detail of FIG.  4 . 
     FIG. 7A is a further enlarged detail of FIG.  7 . 
     FIG. 8 is a section through the upper portion of the capped can. 
     FIG. 9 is a partly sectional schematic side view of a further embodiment of the apparatus according to the invention. 
     FIG. 10 is an enlarged detail of FIG. 9, shown in a subsequent operating position. 
     FIG. 11 shows the detail of FIG. 10 in the next operating position to that of FIG.  10 . 
     FIG. 12 shows the detail of FIG. 10 in the next operating position to that of FIG.  11 . 
     FIG. 13 shows the detail of FIG. 10 in the next operating position to that of FIG.  12 . 
     FIG. 14 shows the detail of FIG. 10 in the next operating position to that of FIG.  13 . 
     FIG. 15 is similar to FIG. 14, but with a different type of cutting blade. 
     FIG. 16 is a section through a pack of two cans resulting from the preceding operations. 
     FIG. 17 is a view from above showing the can-containing tray illustrated in FIG.  9 . 
     FIGS. 18 to  20  are views from above showing packs respectively of two, three and four cans obtained by the apparatus of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An apparatus and relative method for capping individual cans are described hereinafter with reference to FIGS. 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 FIG.  3 ). 
     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  23   a  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 (FIGS. 6,  6 A,  7 ,  7 A). 
     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  27   a  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 FIG.  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  (FIG. 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 . Which is positioned below the plates  21  and  25  (FIG.  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 heater  4  located upstream of the plate  21 , and is immediately afterwards advanced to a position above the plate  21 . Advantageously, the heater  4  are infrared radiation means for, heating a portion of the 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  (FIG.  2 ). 
     In the next stage (FIG. 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  9   a,  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  and the yieldable layer  43  which presses the film against the upper end  12   
     In the next stage (FIGS. 4,  7  and  7 A), 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  9   a ) 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, are finally removed (FIG.  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  9   a  completes its hardening against the surface of the upper portion  11 , to adhere to and exactly mate with its outer form, and them permanently retains this assumed shape. 
     Moreover, the cap  9   a  adheres under vacuum to the can surface, hence covering it hermetically to securely protect it from any external contaminant. With reference to FIGS. 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 FIG. 17, and comprise a base with uniformly distributed recesses  93  for receiving 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 paritioning 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 introduced 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 FIG. 14 the blade  985  rests on the sleeves  971 . 
     If the film  910  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 FIG. 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 thermoformable 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  51  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 FIG.  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 film 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 FIG.  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 FIG. 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 FIG.  13 . 
     On termination of the cycle, all the devices return to their initial position, as shown in FIG. 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 FIG.  15 . 
     In the illustrated example the plate  96  and the underlying tray  92  have the shape shown in FIG. 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 FIGS. 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.