Abstract:
Apparatus for the mechanized replacement of the sealing and cutting modules in the sealing station of machines for the packaging of products in trays, with said station comprising a lower mold with seats for the support of the edges of the trays with product and that by way of motion means is cyclically raised and lowered vertically with respect to an upper mold which supports in the lower part said modules by way of hooking and releasing means so that said modules can be removed and replaced in a selective manner, characterized in that said hooking and releasing means of the modules are provided between the upper plate of each module and the respective hooking plate of the upper mold, with complementary mechanical engaging means of such a kind and oriented so as to be coupled and uncoupled individually and/or simultaneously, imparting to each said module an approaching and separating vertical movement with respect to said hooking plate of the upper mold.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to PCT International Application No. PCT/EP2014/054498 filed on Mar. 7, 2014, which claims priority to Italian Patent Application No. BO2013A000105 filed Mar. 12, 2013, 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 relates to the so-called tray sealers, namely to machines that seal with a cover film pans or trays filled with a product to be packaged, such as a food product. In particular the invention finds application in the sealing station of these machines, usually provided with a lower horizontal mold, provided with compartments open upwards wherein pliers insert and set in support, with their peripheral edge, trays filled with a product and provided with an upper and opposed mold to the previous one, under which passes a film of thermoplastic material coming from a feed reel arranged above and in correspondence to one end of said upper mold and connected to a collecting take-up reel also arranged above and in correspondence to the other end of the same upper mold, inside which the heat-sealing and cutting means are arranged, which after the rising of the lower mold, respectively close each tray by heat-sealing on its peripheral edge a portion of the interposed film and then cut around the perimeter and outside of the sealing said closing film portion, to separate it from the continuous film, so that when the lower mold lowers, the trays closed with the heat-sealed film remain therein, that by way of extractors are arranged in a raised position for the gripping by way of a part of said pliers that, while performing said feeding step of new trays to be closed, transfer the sealed trays from the sealing station in a subsequent unloading station. The waste of the film portion arranged under the upper mold, is cyclically advanced so as to be moved away towards the downstream collecting means and to be replaced by a new portion of intact film coming from the upstream supply means. 
         [0004]    The tray sealers are typically arranged to operate cyclically on assemblies of trays formed by many trays arranged on a row or on two or more parallel rows. The technical problems that occur most frequently in these machines, are due to the necessity of having to replace the cutting means or the electrical resistances of the upper cutting and sealing means and to simplify the resolution of these problems, the tendency is to arrange the cutting and sealing assemblies as modules, to be mounted removably on a single hooking plate associated with the upper mold and which carries the electrical systems, so that in case of a malfunctioning module it can be replaced quickly without having to move the other sealing and cutting modules. This same trend also facilitates the so-called format-change operations of the tray sealers, involving replacement of the cutting and sealing modules to vary the size of the trays to be sealed. 
         [0005]    As state of the prior art, we mention the Japanese patent JP 3743880 B2 with priority date Jul. 10, 2000 and the publication of the patent application U.S. 2011/0072764A1 deposited in Sep. 28, 2010. In this latter prior art is described how the sealing and cutting modules are provided with handles so as to be easily assembled and disassembled, and how their electric power supply and control cables are connected to an outlet arranged laterally to the modules upper hooking structure in order to facilitate maintenance. This document does not describe how the modules are fixed to said upper support structure. From the observation of an advertising catalog taken from Internet, the machine IN50 of the American firm ROSS, holder of the patent application U.S. 2011/0072764A1, it seems that the sealing and cutting modules are mounted on the support structure having a drawer-like solution, with the ability of sliding on horizontal guides and perpendicular to the advancement direction of the trays, and then with the possibility of engaging and extraction from one or both sides of the machine. In this same prior solution, the replacement of the cutting and sealing modules must be done manually, with considerable loss of time for releasing and mechanically re-fixing the modules, for opening and closing the electrical connections and allowing first a sufficient cooling of the module to be replaced in order to avoid dangerous burns to the maintenance personnel. This same solution cannot be applied on sealing and cutting assemblies acting on more than two rows of trays, as for accessing the modules of the inner rows the modules of the external rows should be removed. It is then evident how this same solution requires wide free space on the sides of the machine, in order to perform said drawer-like engagement and extraction operations of the sealing and cutting modules. 
       SUMMARY OF THE INVENTION 
       [0006]    The invention provides to obviate the limitations and the drawbacks of the known art, with the solution described in the annexed claim  1  and subsequent dependent claims, which exploits the following solution idea. The sealing and cutting modules are provided with mechanical engaging means which presuppose a vertical movement of the modules themselves and each module is provided with a vertical electric plug which engages in a corresponding electrical vertical outlet arranged on the modules upper hooking plate, to achieve the necessary electrical connection of the removable electrical power and signal systems. To disassemble a cutting and sealing module, a forced orientation in the seat of the lower mold is arranged which would receive the tray and which is aligned vertically with the module to be replaced, a template, all or in part of insulating plastic material, provided with comfortable side handles and having a shape complementary to the bottom one of the cutting and sealing module to be replaced and when said template is lifted up with the rising of the lower mold, the same template is available under the module to be replaced and with means associated thereto, releases the module from the upper support plate, so that the module is arranged in a centered support on the template which is then sent down and is removed with the module to be changed, which may also be hot as the template is in thermo-insulating material and can be safely grasped, even with bare hands by way of its side handles. During the release of the mechanical hooking means of the module to the upper support plate and during the next downward stroke of the lower mold, the electrical plug of the module slips off automatically from the upper outlet, therefore the whole operation of extraction of the module can be mechanized and can be performed quickly and safely. For the hooking of a new cutting and sealing module, this is arranged with a forced orientation on a support template, which is mountable with forced guidance too in the empty seat of the lower mold, which is then raised to hook the module to the upper hooking plate and to engage its corresponding plug in the electric outlet of the same upper hooking plate. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Further characteristics of the invention and the advantages deriving therefrom, will appear more evident from the following description of a preferred embodiment thereof, illustrated purely by way of non-limiting example, in the figures of the six attached drawing sheets, wherein: 
           [0008]      FIG. 1  shows in perspective and from above a cutting and sealing module according to the invention; 
           [0009]      FIG. 2  shows in perspective from above a portion of the module support and hooking plate of  FIG. 1 , with one of said modules mounted; 
           [0010]      FIG. 3  shows other details of the assembly of  FIG. 2  sectioned along the line III-III; 
           [0011]      FIG. 4  shows with mild lateral perspective and from above, the template used for the release of a cutting and sealing module; 
           [0012]      FIG. 5  shows the two molds of the machine arranged to operate on two tray rows sectioned along the line V-V of  FIG. 2 , with a template arranged in a compartment of the lower mold shown in the low resting position; 
           [0013]      FIG. 6  shows in perspective and from above the same means of  FIG. 5 , limitative to a cutting and sealing module and at the end of the rising stroke of the lower mold; 
           [0014]      FIG. 7  shows the same means of  FIG. 6  sectioned along the line VII-VII; 
           [0015]      FIG. 8  shows the same means of  FIG. 7  in the lowering step of the lower mold with the template and with the cutting and sealing module released from the upper mold hooking plate; 
           [0016]      FIG. 9  shows the same means of  FIG. 8  in the next hooking step of a new cutting and sealing module on the upper mold hooking plate; 
           [0017]      FIGS. 10 and 11  show enlarged details of the hooking system of the cutting and sealing module, shown respectively in the engaging condition as indicated by broken lines in  FIG. 9  and after the engaging step, when the module is supported by the upper hooking plate; 
           [0018]      FIG. 12  shows the electrical plug of each module transversely sectioned, engaged in the respective plug of the hooking plate, when said plate touches the module as in the condition of  FIG. 10 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    With reference to  FIGS. 1 to 3  it is noted that each sealing module M comprises an upper plate  1  with a plan shape correlated to that of the die F for the perimetral cutting of the sealing lid of the trays by the sealing machine that engages said module M and at the center of the plate  1  is superiorly integral and protrudes perpendicularly therefrom, a shank  2  of cylindrical shape, with a round base, with height greater than the thickness of the hooking plate  3  of the module M (see below), which ends with a frustoconical head  102  and with flared edges and which is laterally provided, in opposite positions and with parallel orientation to two sides of the module, for example the shorter sides, with rectilinear grooves  4 ,  4 ′ of equal size and equally spaced from the underlying plate  1 . Seen transversely and in the median area, the grooves  4 ,  4 ′ have a U section and their parallel sides are perpendicular to the axis of the shank  2 . The free edges of the grooves  4 ,  4 ′ are suitably beveled. As illustrated in detail in  FIG. 3 , the shank  2  is provided axially with a guide seat  5  in which a spark plug  6  axially slides having a bearing head  106  on said shank  2  and that with the lower end is removably fixed with suitable means  9 , to the central part of the plate  110  that carries the sealing frame  10  oriented downward and heated by the electric resistance  11 . A counteracting spring  12  strikes the spark plug  6 , reacting on the upper part against a seat of the shank  2  and with the lower end acting on the plate  110  to maintain the sealer  10  in the low resting position. 
         [0020]    To the sealer  10  is usually associated at least one temperature control sensor, not shown in the drawings, therefore for piloting the electric module M is necessary to provide within the same a small electrical circuit formed by five wires: two power wires for the power supply of the electric resistance  11 ; two signal wires connected to said temperature sensor and one grounding wire. These five wires are connected on the other end to a penta-polar plug  13  that with its own insulating body  113  protrudes in part from a window  14  obtained on the plate  1  ( FIG. 1 ) and that brings its own five metal plugs  213  protruding from said insulating body, oriented upward and perpendicular to the plate  1  (see below). 
         [0021]    From  FIG. 1  it is noted that the cutting and sealing module M carries fixed perpendicularly on the support plate  110  of the sealer  10 , a pin  15  with countersunk head  115 , which passes through a slot  215  of the plate  1  and protrudes from the latter for a right segment, both to avoid the rotation of the sealing assembly around the axis of the spark plug  6 , and for other anti-rotation purposes mentioned later. On the side surface of the plate  1 , for example on the edges of the long sides of the latter, protruding references have been arranged made for example by the cylindrical head of the screws arranged for example one in the middle of one side, as indicated with  16  and two on the opposite side, with symmetric arrangement, as indicated with  116  and  216 . It is understood that these references can be differently formed by piece parts of the plate  1 . 
         [0022]    With reference to  FIGS. 2 and 3  it is noted that the plate  3  to which the modules M are hooked underneath, for each module is provided with a cylindrical hole and with round section  17 , of a diameter such as to be crossed with good accuracy by the cylindrical shank  2  of the module M and whose edges are properly rounded. Once the shank  2  is engaged in the hole  17 , the side grooves  4 ,  4 ′ of the same shank protrude from the upper face of the plate  3  where gripping means are provided that readily engage into said grooves to retain the module M hooked to the same plate  3 . For this purpose, on the upper face of the plate  3 , on one side and on the other side of the hole  17  small seats  18 ,  18 ′ are formed by material removal, parallel to each other and to the grooves  4 ,  4 ′ of the shank  2 , which end in a recess  19  provided on one side of the plate  3  and said seats  18 ,  18 ′ have a depth slightly greater than the thickness of flat levers  20 ,  20 ′ pivoted with one of their ends in  21 ,  21 ′ within the same seats  18 ,  18 ′ and which extend up to protrude with the other end from the same side recess  19  of the plate  3 , where they present integral lower cylindrical extensions  22 ,  22 ′ and where the same levers  20 ,  20 ′ are interconnected by a traction spring with cylindrical helix  23  which causes said levers  20 ,  20 ′ to engage the grooves  4 ,  4 ′ of the shank  2  and to retain the module M hooked to the plate  3 . Even the spring  23  is housed without interference in said recess  19 . In the hooking position of the module M, as well as in the resting position, when the shank  2  is not engaged in the hole  17 , the levers  20 ,  20 ′ are maintained by the spring  23  bearing against the inner side of their seats  18 ,  18 ′ and with a portion of their inner sides protrude inside the hole  17 , so that when in said hole the shank  2  is engaged and raised, the tapered end  102  of said shank can progressively enter between said levers  20 ,  20 ′ and widen them, until they cooperate with the cylindrical portion of the shank  2  and when the grooves  4 ,  4 ′ thereof reach the height of the levers  20 ,  20 ′, these come to snap into the same grooves  4 ,  4 ′ and firmly engage the module M to the support plate  3  (see below). To avoid unwanted bending and bending-torsion stress on the levers  20 ,  20 ′ when these cooperate by sliding with the shank  2 , the seats  18 ,  18 ′ are closed by a small plate  24  fixed, for example by screws on the upper face of the plate  3 , as shown in continuous lines in  FIG. 3  and in broken lines in  FIG. 2 . 
         [0023]    Always in  FIG. 2  it is noted that the hooking plate  3  is provided in a pre-fixed position, with a hole  25  with flared edges, which houses the protruding segment of said pin  15  of the sealing module M to prevent the latter from rotating on the coupling formed by the shank  2  and the hole  17  that houses it. For the cooperation between these same parts  15  and  25 , the module M assumes a forced and predetermined position on the plate  3 , useful for the correct cooperation of the same module M with the seat carrying the tray in the lower mold of the sealing machine. Also for the mutual cooperation with said parts  15 ,  25 , the module M is arranged with its own side reference  16  ( FIG. 1 ) in alignment with the centerline of said recess  19  of the hooking plate  3 . 
         [0024]    The hooking plate  3  is finally provided with an electrical penta-polar outlet  26 , whose insulating body  126  protrudes downward from a window  27  of the same plate  3  and carries the contact metal bushings  226  open downward and in the vertical alignment position, useful for the coupling with the pins  213  of the electrical plug  13  of the sealing and cutting module M as shown in  FIG. 1 . With  28  is indicated the bundle of electric wires connected to the outlet  26  and in abutment against the electrical panel (not shown) for powering and controlling the sealing assembly  10  of the various modules M hooked to the plate  3 . 
         [0025]    With reference to  FIGS. 4 and 5  is now described the equipment to be used and the respective method of use to disengage from the hooking plate  3  a defective sealing module M. In  FIG. 5  is indicated with C 1  the lower mold with the seats S that in operating machine house each a tray to be sealed. The mold C 1  is initially in the low resting position and away from the overlying mold C 2  of a distance such that on the same mold C 1  the equipment that is described below with reference to  FIG. 4  can be arranged easily. In the upper mold C 2  a plate  3  for hooking the modules M is housed provided in number of one for each said lower seat S, which are illustrated here in the resting position, with the sealer  10  protruding below the cutting die F.  FIG. 5  shows, purely by way of example, how the hooking plate  3  is supported by medians spark plugs  29  sliding in the guide bushings  30  fixed on a support structure  31  and from these bushings said spark plugs  29  protrude upwards with a segment pushed upwards by a contrast spring  32 . On the same support structure  31  are arranged in a position equidistant from the bushings  30 , additional bushings  33  for the sliding of the spark plugs  34  fixed to the bell  100  of the upper mold C 2  and pushed downwards by counteracting springs  35 . In the rest position, the hooking plate  3  bears against the spacers  50  integral with the bell  100  of the mold and C 2  and appears evident that there is a sufficient clearance between the upper end of the hooking shanks  2  of the modules M and the same bell  100  whose lower perimeter with a channel-profile  100 ′ is arranged below the sealing and cutting  10  assemblies of the same modules M. 
         [0026]    Have not been illustrated in  FIG. 5  the means that on command push downwards the plate  3  with the modules M to perform the cutting and sealing step of the trays lids, as it is not necessary for the understanding of the invention which is expected to operate on the upper bell C 2  at rest conditions. 
         [0027]    The equipment to be used for the purposes in question, is illustrated in  FIG. 4  and comprises a template  36  having the shape of a parallelepiped box and inverted, made with any thermo-setting plastic material, provided with a flat upper wall  136  on which is intended to rest the lower part of the module M and peripherally surrounded by a relief edge  236  for containing the same module M, provided with comfortable grip handles  37  on the short sides, with downward extensions  336  of its side walls, with which it engages the perimeter of the seat S of the lower mold C 1  to properly center therein the template  36  which with its corner portions  436  rests on the upper face of the plate  38  with the seats S, that in this way takes over the mechanical support function of the same template  36 . On one of said corner portions  436  of the template  36  a projecting vertical peg  39  is provided which must enter into a hole  40  provided only on one of the portions with which the plate  38  supports the corner areas of the template  36 , so that the latter will result arranged on the lower mold C 1  with a forced orientation and such that a plate  41  with which the template  36  is laterally provided on the half of one of its long sides, which extends above the peak  136 ,  236  of the template and that carries in the upper part of the oblique sides  141  and a median slit  42 , appears below and in vertical alignment with the recess  19  ( FIG. 2 ) of the hooking plate  3  and with the side reference  16  of the module M arranged therein. On half of the other long side, in opposition and parallel to the plate  41 , the template  36  carries a rectangular and protruding plate  43 , of a height less than that of the plate  41  and provided at the top with a pair of slits  44  which are in vertical alignment with the pair of side references  116 ,  216  with which the module M is provided ( FIG. 1 ). 
         [0028]    After mounting the template  36  in a seat S of the lower mold C 1 , as mentioned earlier with reference to  FIG. 5 , the rising of the same mold C 1  is controlled with a preset stroke towards the upper mold C 2  which remains stationary and the end of this rising stroke is illustrated in  FIG. 6 , from which is detected how the side references  116 ,  216  of the module M are engaged into the slits  44  of the plate  43 , how the side reference  16  of the same module M is engaged in the slit  42  of the plate  41  and how, before these references touch the bottom of said slits and before the sealing assembly  10  touches the peak  136  of the template  36 , the oblique sides  141  of the same plate  41  cooperate with the end extensions  22 ,  22 ′ of the levers  20 ,  20 ′, by spreading said levers and extracting them from the side slots  4 ,  4 ′ of the shank  2  of the module M, with the result that said module is released by gravity from the hooking plate  3  and under the guide of the side plates  41 ,  43  falls on the nearest upper wall  136 ,  236  of the template  36  that takes over in the supporting the module, while the slots  4 ,  4 ′ are arranged below the levers  20 ,  20 ′ still in the open position, as shown in  FIG. 7 . When the lower mold C 1  is lowered, as shown in  FIG. 8 , while the oblique sides  141  of the plate  41  leave the ends  22 ,  22 ′ of the levers  20 ,  20 ′ and these latter are close up again, the inner sides of said levers are to cooperate with the upper cylindrical part and then with the conical head  102  of the shank  2 , finally abandoning the module M that descends with the lower mold C 1 , resting and in the correct centering position on the template  36 . While the template  36  is lowered and moves away from the hooking plate  3 , also the electrical contacts of the plug  13  detach from the bushings of the outlet  26  of the same plate  3 , thanks to the weight of the module M that is much greater than the frictional resistance that the plug meets by detaching from said outlet. When the mold C 1  has reached the end of the lowering stroke, it is easy and safe for the operator, to grasp the template  36  by the handles  37  and remove this component with the module M from the seat S for freeing it and have it ready for the next mounting step of a new cutting and sealing module M′. Even if the extract module M is warm, the thermo-insulating nature of the template  36  makes the handling of the ensemble extremely safe. 
         [0029]    The engaging step of a new module M′ on the hooking plate  3 , is an operation which is also very simple and rapid, which involves the provision in the empty seat S of the lower mold C 1 , of a template  36 ′ as from  FIG. 9 , which differs from the  36  used for the releasing, for the fact that the previous plate  41  ( FIG. 4 ) is replaced by a plate  41 ′ of much lower height, devoid of the upper oblique sides since this plate  41 ′ must not cooperate with the ends  22 ,  22 ′ of the hooking levers  20 ,  20 ′ and provided with a short central slot  42 ′ adapted to cooperate with the side reference  16  of the new module M′. The plate opposite to that  41 ′, indicated in  FIG. 9  by broken lines, is quite equal to that of  43  and is provided with two upper slots  44  for the cooperation with the side references  116 ,  216  of the module M′ that for the cooperation effect with these plates is correctly oriented with respect to the holes  17 ,  25  and to the electric outlet  26  of the hooking plate  3 . Once the new template  36 ′ with the new module M′, correctly oriented, is successfully mounted and oriented in the seat S of the mold C 1 , the rising of the same lower mold C 1  is controlled with a preset stroke that causes the shank  2  to enter in the hole  17 , to spread the levers  20 ,  20 ′ which then snap hook in the side grooves  4 ,  4 ′ of the same shank  2  and that causes the plug  13  of the same module M′ to engage in the outlet  26  of the plate  3 . When the lower mold C 1  is taken back into the low position, the new module M′ remains hooked to the plate  3  and, after removing the template  36 ′ from the seat S, the machine is ready to be put back into tension and to return operative. It is obvious that in the release and hook steps described of a module M, M′ from and to the plate  3 , the outlet  26  is not under tension. It is also evident that the described operations of orientation of the template, of orientation of the module with respect to the template itself and of opening and closing of the levers  20 ,  20 ′ for the releasing and hooking steps of the modules M, M′, if desired, may be easily controlled and monitored with electrical sensors or electric micro-switches easily arrangeable and connectable by experts in the field, to ensure that in the event of non-compliance with the orientation protocol of the template  36 ,  36 ′ on the lower mold C 1  and/or of the module M, M′ on the same template, the movement of the lower mold is automatically stopped and acoustic and/or visual signals are activated to indicate the type of incident that occurred. All this leads to the substitution operation of one sealing and cutting mold in a tray sealer becomes of such simplicity that can be safely performed even by non-qualified personnel, with the great economic benefits that this entails. 
         [0030]    In  FIG. 10  is shown enlarged a side of the shank  2  of a module M at the end of the rising stroke for the hooking of the plate  3  to the upper mold C 2 . In this step, the upper face of the plate  1  of the module M abuts against the lower face of the plate  3  and the grooves  4 ,  4 ′ of the shank  2  are aligned with the levers  20 ,  20 ′ and since the height dimension of each groove  4 ,  4 ′ is slightly greater than the thickness of each said lever, and because small clearances G, G′ are formed above and below said parts, the levers  20 ,  20 ′ enter without resistance and with safety in the grooves  4 ,  4 ′ and when the lower mold is lowered, the module M moves to the condition of  FIG. 11 , with the upper face of the grooves  4 ,  4 ′ resting on the levers  20 ,  20 ′ which take over in supporting the shank  2  and the module M whose upper plate  1  moves away from the lower face of the support plate  3  with a clearance G″ of small entity, related to the abovementioned clearances G, G′. It follows that when the cutting and sealing module works by way of thrust on the tray for sealing the cover thereon, the plate  1  of said module comes in contact with the plate  3 , as mentioned with reference to  FIG. 10 . These small oscillations of the modules M with respect to the hooking plate  3  allow that if the plug  13  and the outlet  26  were fixed to the respective plates  1  and  3 , the same would be cyclically subjected to a small movement towards and away one with respect to the other, with possible formation of wear in the electric contacts and with the dangers that would follow. The invention intends to overcome this drawback, leaving the small clearances previously mentioned, that simplify the hooking and releasing operations, and by mounting the plug and the electrical outlet on respective support plates, with a floating solution, as is now described with reference to  FIG. 12 . From said figure it is noted that the plug  13  and the outlet  26  are provided with respective base swellings  113 ′ and  126 ′ of their insulating body, arranged respectively below the plate  1  and above the plate  3 , having a substantially rectangular shape in plan, provided in the corner areas with holes for the passage of the shank of respective screws  45 ,  45 ′ screwed in holes of the respective plates  1  and  3  and having a length greater than the thickness of said bases  113 ′ and  126 ′ so to fulfill a sufficient approaching and spacing displacement with respect to the respective plates  1 ,  3 . The holes for the passage of said screws  45 ,  45 ′ are provided with respective widenings open towards the head of the same screws and in said widenings springs  46 ,  46 ′ are housed which push the same bases  113 ′ and  126 ′ into contact with the plates  1 ,  3 , to determine a sufficient projection from the windows  14  and  27  of the insulating body  113 ,  126  of the plug  13  and of the outlet  26 . From the above it follows that when the plate  1  of the module is raised into contact with the hooking plate  3 , as shown in  FIG. 12 , because the thrust force of the springs  46 ,  46 ′ is greater than the engaging friction of the plugs  213  in the bushings  226 , these components are immediately coupled to each other and at the end of the engaging stroke, the protruding portions of the insulating bodies  113 ,  126  touch each other and move away their bases  113 ′ and  126 ′ from the respective plates  1 ,  3 , forming a clearance G′″ which has for example, approximately, the value of the clearance G″ of  FIG. 11 , so that when said clearance is formed between the plates  1  and  3  during the operating cycles of the sealing and cutting modules M, the insulating parts  113 ,  126  of the body of the outlet and plug assembly  13 ,  26  move through respective apertures  14 ,  27  but remain always in contact with each other and the plugs  213  are always fitted and axially blocked into the plug bushings  226 , avoiding relative sliding and the previously mentioned drawbacks. It is obvious that the context of the invention also comprises the variant embodiment which envisages that the springing of only one of the insulating bodies of the outlet or of the plug, even if the solution shown is to be considered preferable in that the movements and the stresses are distributed on the two units, ensuring a lower stressing and a longer life of the system. A further variant may refer to the placement inversion of the plug  13  and of the outlet  26  and/or to a different orientation of these components with respect to what illustrated in the drawings. 
         [0031]    It is understood that the description refers to a simple, reliable and preferred embodiment of the invention, to which numerous variations and constructive modifications can be made, all of which without abandoning the guiding principle of the invention, as described, illustrated and as claimed below. In the claims, the references between brackets are purely indicative and do not limit the protection scope of the claims.