Abstract:
Apparatus with facing bell members, for modified-atmosphere packaging of products placed in trays, which comprises means for the cyclic positioning of an extended portion of bather film between the said two open bell members and over trays housed with gasket means in the seats of the bottom bell member, which comprises means for moving the said bell members towards each other so as to close between them the said film and to close under and at a suitable distance from this latter the edge of the tray, apparatus of the type that when the bell members are closed, they form therein two volumes not directly communicating, one of which is formed by the internal chambers of the same bell members that communicate with each other via circuits, for example peripheral, while the other volume is formed by the main chambers of the trays with the product, wherein the said chambers are connected with a portion of their perimeter to holes and to a dedicated circuit for the controlled introduction of process gases and are connected with another portion of their same perimeter to discharge holes for implementation of the air extraction and washing steps, comprising internal valve means to enable the said discharge holes of the main chambers of the trays to communicate, or not, with the said internal chambers to balance the differences in pressures between the said two volumes during the exchange cycle of the gases required to produce packaging of the type known as MAP.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to PCT International Application No. PCT/EP2013/070743 filed on Oct. 4, 2013, which claims priority to Italian Patent Application No. BO2012A000549 filed Oct. 9, 2012, the entirety of the disclosures of which are expressly incorporated herein by reference. 
     
    
     STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT 
       [0002]    Not Applicable. 
       BACKGROUND OF THE INVENTION 
       [0003]    The invention refers to those systems or apparatus that sealingly weld a closing film on at least one tray containing a product to be packaged. The apparatus according to the invention is of the type with facing bell members, classifiable in IPC B65B31/04, capable of producing packages of the kind known as MAP (Modified Atmosphere Packages), in which the product is enclosed inside a sealed package containing a modified atmosphere useful to improve the preservation of the product, without any substantial difference in pressure between inside and outside. In order to modify the atmosphere inside the pack, in a step in which the barrier film is placed over the product placed in the tray for subsequent closing, kept at a suitable distance from the perimeter edge of the same tray, the air is firstly removed from the inside of the tray and then replaced with a modified atmosphere, for example based on nitrogen, carbon dioxide, oxygen and/or other gases. The prior art closest to the invention is described in the Italian patent application No. BO2011A-000403 dated Jul. 6, 2011, in the name of the same Applicant, which refers to an apparatus comprising a top bell member which is open downwards, usually containing the welding means and also the means for cutting the barrier film for closing the trays and comprising a bottom bell member, facing the preceding bell member and open in this direction, with a chamber and with a seat for housing at least one tray which may be inserted into and extracted from the said seat by specific means, comprising means for cyclic positioning of an extended portion of film between the said two open bell members and above the trays placed in the bottom bell member, which also comprises means for moving the said bell members towards each other, to close between them the edge of the tray and over this said film and comprising means for performing in this sequence the steps of extraction of the air from the tray and introduction of process gases therein for preservation of the produced place in the tray before to the subsequent step of welding of the film on the edge of the same tray and cutting of the perimeter of the portion of film welded to the same tray. This apparatus comprises means for ensuring that during the step for mutual closing of the bell members, these form therein a main chamber defined at the top by the film for covering the tray, at the bottom by the same tray with the product and at the side by any interface structure that surrounds and connects the perimeter of the said film to the perimeter of the top edge of the tray and on the structure of which holes or slots are provided, suitably distributed and positioned on the outside of the perimeter of the tray and communicating with the said main chamber. In the same apparatus according to the prior art indicated above, when the two bell members are closed, two volumes, which do not directly communicate which each other, are formed inside the said bell members, a first volume formed by the said main chamber, with the tray and with the covering film, and a second volume formed by the internal intercommunicating chambers of the said two bell members. Some of the holes of the said interface structure open out substantially along a portion or side of the tray and are connected to a first header or circuit located in the bottom bell member, while other said holes open out along at least one portion or opposite side of the same tray and are connected to a second header or circuit also located inside the bottom bell member, whereas the internal chambers are connected to one another and to at least a third circuit, Means are provided such that, via the said first and second header or circuit, connected to the said main chamber and via the said third circuit connected to the internal chambers of the two bell members, it is possible to produce MAP-type packages without having to previously form very high vacuums in the trays and limiting the use of process gases. An apparatus of this type has a certain degree of structural complexity, must be reprogrammed to vary the format of the trays and also requires complex calibration to balance the two volumes concerned in the step of introducing the process gas and the balancing step, in order to obtain packages always with the desired appearance. 
       SUMMARY OF THE INVENTION 
       [0004]    The invention proposes a structural simplification of the apparatus in question, still producing them with a view to forming two volumes which do not communicate directly with each other, when the two bell members are closed and with three circuits, as stated in the prior art indicated above, but with a new solution that automates the balancing step and provides for the use of valve means, via which it is possible, in given situations, to automatically balance the pressure differences between the said two volumes. To obtain a solution to this technical problem, it was also necessary to solve the following ensuing problem: to ensure a separation with safe and reliable seal between the main chamber with the product and the internal chamber of the bottom bell member, as the current solutions that entrust this separation either to the edge of the tray and/or to gaskets that operate on the bottom face of the edge of the same tray have proved to be somewhat unreliable due to the fact that this edge is not always perfectly planar and due to the thrust, often insufficient and useful for the purpose, exerted by the weight of the product placed in the tray. The invention intends to solve the said main problem of the invention with the following idea for solution. The holes for outflow of the washing air and through which the vacuum in the main chamber of the tray is initially obtained, are raised to a level such as to be initially covered by the film covering the tray and these same holes communicate with the internal chamber of the bottom bell member. With this solution and with the other small circuit arrangements indicated below, it is possible to use the film as a membrane valve to open or close the said holes below to obtain, with the best result and completely automatically, the steps of depressurization, washing and pressurization with process gases of the main chamber with the internal volume of the tray. The said secondary problem is solved by providing, in each seat for housing a tray, a flexible lip seal gasket, which projects into the internal opening of each said seat, to cooperate with seal with the external lateral and usually inclined surface of the tray. 
         [0005]    As prior art documents, the following documents are cited: WO 2011/124548 (D1); DE 23 35 021 (D2); JP S52 042 161 (D3); U.S. Pat. No. 3,992,850 (D4); U.S. Pat. No. 3,481,100 (D5). No means are provided in the device according to D1 to discontinue the communication between the main chamber end the internal chambers, which are always in indirect communication through holes, and not through valves. Starting from this document which is regarded as being the prior art closest to the subject-matter of the invention, the problem to be solved is that of further automatize the evacuation, gasification and compensation steps, without adding constructive complications. The document D2 shows a gas discharge element, which however is not a valve, in the sense that it cannot discontinue the communication between the main chamber and the internal chambers. The document D3 shows a valve which however is not used for putting into communication the main chamber with the internal chambers, rather to inject steam in the main chamber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Further characteristics of the invention, and the advantages deriving therefrom, will be more apparent from the following description of a preferred embodiment thereof, illustrated purely by way of non-limiting example, in the figures of the three accompanying drawings, wherein: 
           [0007]      FIG. 1  is a cross-sectional view of the two facing bell members, in the first step of closing over the film and over the trays containing product to be conditioned and closed, with a schematic illustration of the circuit for conditioning the same trays and which controls operation of the same apparatus; 
           [0008]      FIG. 2  is a top view of the bottom bell member with the seats for housing the trays illustrated partly empty and partly loaded with the related tray; 
           [0009]      FIG. 3  schematically illustrates comparative diagrams of the operating steps of the main components of the apparatus; 
           [0010]      FIG. 4  illustrates a perspective view of the central part of the apparatus closed as in  FIG. 1  and in the step of forming the vacuum inside the trays; 
           [0011]      FIG. 5  illustrates the left seat of the apparatus as in  FIG. 1 , in the step of washing and of injecting the process gases for preservation into the tray; 
           [0012]      FIGS. 6 and 7  illustrate the central part of the apparatus, as in  FIG. 4 , respectively in the step of injecting the process gases into the tray and in the step of lowering the means of the top bell member that carry the welding and cutting means for welding and cutting the film on the top edge of the trays. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]    In  FIG. 1 , the numeral  1  indicates the top bell member with its inner annular edge  101  and with the outer and facing edges  201  defining together with the inner edge  101  facing chambers  102 , which, via openings  3  provided on the same inner edge  101 , communicate with the internal volume  2  of the bell member  1 , which is connected to specific vertical guiding and raising-lowering means, schematically indicated by the double arrow Fl and not shown in detail, as they are known. Inside the bell member  1  there is positioned a plate  4 , of known type, connected to specific and selective raising and lowering means  104  and which with interposed respective guiding and spring means  105 , supports at the bottom heat-welding units  5  and carries cutting means  6  that externally surround each sealing unit  5  and that are normally retracted from the bottom useful edge of these components  5 . The bell members illustrated in  FIG. 1  are such as to be able to operate simultaneously on two parallel rows of trays V, and V′, while it is understood that the scope of protection of the invention also includes bell members capable of operating on more than two rows of trays, or on a single row of trays or a single tray, all in a manner deducible and easily obtainable by those skilled in the art. The numeral  100  denotes known means that dampen closing of the top bell member  1  on the bottom bell member, indicated below. The heat-weldable barrier film H, with which the preformed trays V, V′ filled with the product M are to be sealingly closed, passes underneath the bell member  1 ; the trays are positioned by any suitable means under the same bell member  1 , resting on extractors  7  of known type associated with the bottom bell member  8 , with respective guiding and movement means  107 . The bottom bell member  8  is itself connected to specific known raising and lowering means, represented schematically by the double arrow F 2 , and is provided with an internal chamber  9  having a shape and size suitable to house the extractors  7  with the trays V, V′ when the same bell member is raised (see below) and this chamber  9  is closed at the top by a horizontal frame  10 , provided with mouths or seats  110  of a shape correlated with that of the trays, on the perimeter edges  210  of which the edges of the same trays are intended to rest and at the centre of which the extractors  7  operate; in the raised position the extractors receive the trays, are then lowered to insert the same trays into the seats  110 , with perfect self-centring thereof with respect to the various components of the bell members  1  and  8 , and at the end of the cycle are raised again to prepare the same closed trays for the step of removal and replacement with new trays to be closed. 
         [0014]    In the prior art, on the edges  210  of the seats  110  there can be provided annular gaskets, made of elastomeric material, on which the lower side of the edges of the trays rested, also to ensure sealed separation between the internal chambers of the bell members  1  and  8  when in closed position. As this separation was difficult to achieve, for the reasons specified above, the invention proposes a solution to this technical problem by fixing on the edge  210  of the seats  110 , for example via a small frame  11  and appropriately distributed fixing screws  12 , an annular gasket  13 , flat and flexible, for example made of silicone rubber, which projects with a lip seal and with the right portion inside each seat  110 , which is preferably provided in the corner areas with recesses  113 , arched and connected with the appropriate connection to the consecutive portions of the same gasket, which in this way is capable of uniting, intimately and with perfect seal, the top or medium-top lateral part of the tray and of ensuring the desired conditions of sealed separation of the internal chambers of the two bell members via the seats  110  and the trays inserted therein. The gasket  13  as described above has proved to be very effective for sealing purposes and such as to facilitate both insertion and removal of the tray into and from the same gasket  13 , without it being subject to undesirable deformation and/or wear from friction and from the thrusts of the tray. At a higher level to that of the edges of the tray when they are resting on the edge  210  of the seats  110 , the lower bell member  8  has a horizontal surface  14  with a closed annular gasket  15  with which the edge  101  of the upper bell member  1  cooperates in the closed position and the same surface  14  has facing extensions, onto which there open out slots  16  surrounded by portions of the said gasket  15  and by supplementary gaskets  115 , with which the external edge  201  of the upper bell member cooperates with seal so that, via the chambers  102 , the openings  3  and the slots  16 , the internal chamber  2  of the top bell member  1  communicates directly and preferentially with a duct  109  associated with the bottom bell member  8 , which with its ends communicates with the said slots  16  and which is provided with calibrated openings  103  for connection with the chamber  9  of the same bottom bell member. The duct  109  is provided with a mouth  17 , which via intercepting units with valves means  18 ,  118 , controlled by a processor  19 , can be connected disconnected to or from a buffer  121 , in turn connected to a vacuum forming pump  21 , or to and from a buffer  122  with related pump  22 , for the controlled supply of filtered air at the appropriate pressure (see below). A pressure switch or vacuum switch  23 , which sends its data to the processor  19 , is branched off the circuit coupled to the duct  17 . The numeral  20  denotes a unit for programming and optionally interrogating and controlling the processor  19  and the various components coupled to it. From  FIGS. 1 and 2  it can be seen that the portion of surface  14  of the frame  10  of the bottom bell member, which is positioned between the two rows of seats  110 , is provided with rows of holes  24 , which preferably have a larger diameter and are greater in number on the said portions of surface positioned at the nodes or intersections of the two rows of seats  110 , for example arranged in several parallel rows, as indicated with  124 . Optional specific holes  224  can also be provided on the ends of the flat portions  14  orthogonal to those carrying the said holes  24 .  124 . All the holes  24 ,  124  are suitably flared at the top end and at the bottom communicate freely with the internal chamber  9  of the bottom bell member. For correct operation of the apparatus the sum of the sections of the holes  24 ,  124  is less than the sum of the sections of the slots  16  with the openings  3  for connection between the internal chambers  9  and  2  of the bell members  1  and  8  (see below) and the sum of the sections of the openings  103  is less than the sum of the sections of the slots  16  with the said openings  3 , so that the flow in the duct  109  is in preferential connection with the internal chamber  2  of the top bell member  1 . As a result of this preferential connection, the vacuum or pressure conditions that are created in the duct  109  extend rapidly to the chamber  2  of the top bell member and with a delay also extend to the chamber  9  of the bottom bell member. It is understood that the circuit solution  17 ,  109 ,  103 ,  9 ,  16 ,  3 ,  2  illustrated in  FIG. 1  is provided purely by way of non-limiting example and can be widely modified, also as a function of structural requirements, without departing from the scope of the invention. From  FIGS. 1 and 2  it can also be seen that each seat  110  for housing a tray is surrounded by an annular and recessed groove  25 , which in one or more areas facing or at a suitable distance from the rows of holes  24 ,  124 , is in turn provided with holes  26  connected to headers  27  positioned inside the bell member  8  and which via branched lines  127  are in turn connected to a centralized mouth  227  connected to an intercepting unit  28 , in turn connected to a buffer  29  for supplying the process gases to be introduced into the trays and a pressure switch and/or vacuum switch  30 , which also sends its data to the processor  19 , is provided branched off to the same mouth  227 . The apparatus functions as described below. 
         [0015]    During an intermediate and initial step of the operating cycle, the apparatus is in the condition shown in  FIG. 1 . The trays V, V′ with the product M are inserted in the seats  110  of the bottom bell member  8 ; with their body they cooperate with the gaskets  13  now deflected downward and which touch with seal the outer body of the same trays, which their top edge rest on the frame  11  that fixes the same gaskets  13  in place. The bell members  1  and  8  are closed against each other with the edges  101 ,  201  touching the gaskets  15 ,  115  with seal, and with a portion of barrier film H gripped between the gasket  15  of the bottom bell member and the edge  101  of the top bell member. The film H is suitably raised off the trays V, V′ as positioned in seats  110  retracted with respect to the top surface  14  of the bottom bell member, on which surface  14  the same film rests and is thus positioned over all of the holes  24 ,  124  and touches the flared top end thereof. In this way, between the bottom face of the film H and the trays V, V′ main chambers P are produced, communicating freely only with the holes  26 , as these chambers P are separated from the internal chambers  2  and  9  of the bell members by the film H that surmounts and closes all the holes  24 ,  124 . In a first step of the operating cycle, the intercepting means  28  are closed and the processor  19  controls opening of the intercepting means  18  and connection of the mouth  17  to the suction means  22 ,  122 , with consequent activation of the suction step  31  ( FIG. 3 ) of the air from the internal chambers  9  and  2  of the bell members. As a large part of the lower face of the film H is covered by the trays V, V′, isolated from the chamber  9  by the action of the annular gaskets  13  and due to the more direct connection of the duct  109  with the chamber  2  of the top bell member, a vacuum is rapidly created in the same chamber  2 , which tends to raise the film H, as indicated by the arrows F 3  in  FIG. 4  and by step  32  of  FIG. 3  and this raising action causes opening of the holes  24 ,  124 , with the result that via these open holes the main chambers P of the trays are placed in communication with the chamber  9  of the bottom bell member, which is also under suction, and the remaining air is rapidly removed therefrom. When the vacuum pressure values on the opposite faces of the film H are equal, the film returns to its original lower position, as indicated by step  132  of  FIG. 3 . The suction step  31  can be predetermined in terms of time (see below) and is controlled by the processor  19 , also via the instruments  23  and  30 . At the end of the step  31  and after closing of the intercepting means  18 , the step  33  of introducing the process gases into the trays takes place, with opening of the intercepting means  28  of  FIG. 1 . The process gases enter the trays via the holes  26  and thrust the film H upwards, as indicated in step  232  of  FIG. 3  and as illustrated in  FIG. 5 , carrying the same film into contact with stop means  34  housed in a specific bottom recess of the welding means  5  and into contact with the flexible elastic gasket  136  of a spring press  36 , positioned on the plate  4 , over the holes  24 ,  124  and which shall be specified below. As a result of raising of the film H into a dome, a vertical flow, indicated schematically by the arrows F 4  in  FIG. 2 , is created in the main chamber P of the trays and gradually saturates this chamber P and performs the washing step, pushing the air remaining in the various chambers P to exit through the holes  24 ,  124  not intercepted by the same film H which is in a high position. After a correct time interval  35  ( FIG. 3 ) from the start of the step for introducing gases inside the packages, the intercepting means  118  ( FIG. 1 ) that connects the compressed air source  22 ,  122  with the internal chambers  9  and  2  of the bell members are opened carry out the balancing step, indicated with  36  in  FIG. 3 . The balancing air has a pressure higher than the ambient pressure (see below), so that due to the preferential circulation guaranteed by the internal free passages  16  and  3  between the bell members, on account of the limited total section of the holes  24 ,  124  and on account of the gaskets  13  that separate the main chambers P from the internal chamber  9  of the bottom bell member, the same balancing air forms in the volume  2  and consequently on the top face of the film H, a pressure higher than the pressure in the main chamber P, generating the action indicated in  FIG. 6  by the arrows F 6 , which moves the same film H downwards, with substantial immediate closing of the holes  24 ,  124 , preventing the balancing air present in the chamber  9  of the bottom bell member from rising via the same holes  24 ,  124 , from reaching the inside of the trays and from polluting them. In close sequence of steps, the volume  9  of the bottom bell member is also filled with balancing air, until reaching the same pressure as the volume  2  of the top bell member. The action F 5  ( FIG. 6 ) generated through the holes  24 ,  124  by the pressure of the balancing air present in the bottom chamber  9 , is not able to raise the film H as generated by the same pressure values but incident on a smaller area of the same film, the area covering the holes  24 ,  124 , while the action F 6  occurs on the whole of the top face of the same film H. In this sequence of steps, the plate  4  is lowered as in step  38  of  FIG. 3 , so that the press  36  firmly closes the holes  24 ,  124  as indicated in  FIG. 7  and the film is then heat-welded to the edge of the trays by the welding means  5  and, finally, the welded portion of film is separated from the scraps by the action of the cutting means  6 . In this sequence, the switching units  28 ,  118  of  FIG. 1  are closed, the bell members  1  and  8  are opened, the closed trays are raised by the extractors  7 , removed and replaced by new trays to be closed, the film H moves forward to be positioned with a new portion thereof over the new trays, and the cycle described above is repeated. 
         [0016]    The operating procedure of the apparatus as described can be summarised with the sequence of the following operating steps, already considered above with reference to the diagrams of  FIG. 3  and, for example, with the following operating values, which are indicated purely by way of non-limiting example, as they are easily deducible through experiments:
       a step  31  of applying the vacuum in the internal chambers  9 ,  2  of the two closed bell members  1 ,  8 , for example of −890 mbar, for a time of around 3000 msec, also to remove air from the main chambers P of the trays V, V′;   at the end of the said vacuum step  31 , the step  33  is activated of introducing process gases into the main chamber P of the trays, via the dedicated holes  26  and the related circuits. This step lasts, for example, around 360 msec and supplies the said gases from the buffer  29  at the pressure of around 2.5 bar. During this step, the residual air of the main chambers P of the trays is discharged into the chamber  9  of the bottom bell member via the dedicated holes  24 ,  14  left free by the film H which is temporarily raised;   after around  150  msec from the start of the said step  33  of introducing process gases, the step  37  starts, for supplying compressed air from the buffer  122 , at the pressure of around 2.5 bar. This step lasts, for example, for around 300 msec and during this time the film H closes the holes  24 ,  124  which first connected the main chamber P of the trays with the internal chamber  9  of the bottom bell member  8 , so as to prevent any form of pollution of the said chamber P;   in sequence, following steps  33 ,  37  of supplying process gases and of external balancing with compressed air, the step  38  takes place for lowering the unit carrying the said press  36  to close the said holes  24 ,  124  and which subsequently carries the welding means  5  to weld the film H on the top edge of the tray and which finally carries the cutting means  6  to cut and separate from the film the portion thereof welded on the same tray. It is once again understood that the values indicated above are purely indicative and non-limiting and that the description refers to a preferred embodiment of the invention, to which numerous variants and structural modifications can be made, all without departing from the informing principle of the invention, as described, illustrated and as claimed below. In the claims the references indicated in brackets are purely indicative and do not limit the scope of protection of the same claims.