Abstract:
The invention relates to a method for producing reclosable packages and to a deep-drawing packaging machine with an embossing station for embossing recesses into a top foil.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims foreign priority benefits under 35 U.S.C. §119(a)-(d) to German patent application number DE 102010034021.9, filed Aug. 11, 2010, which is incorporated by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    The present disclosure relates to a method of producing reclosable packages as well as to a deep-drawing packaging machine for executing said method. 
       BACKGROUND 
       [0003]    U.S. Pat. No. 7,172,779 B2 and DE 202005006262 Ul disclose packages which offer the possibility of reclosing the package by means of locking elements formed in the lower part of the package as well as in the lid, so as to guarantee that, when part of the products has been removed, the remaining part of the products in the package will be preservable for a sufficiently long period of time. The locking elements serve to confirm, by an audible snap, that the package is reclosed and to interconnect the two package halves such that, when the upper package half is raised, the lower package half cannot detach itself from the upper one in spite of the weight of the product. 
         [0004]    U.S. Pat. No. 7,665,281 B2 and US 2007/0138192 A1 disclose a method in the case of which the locking elements are simultaneously formed in both package halves in a work station, when both said package halves have been closed in a sealing station of a deep-drawing packaging machine so as to form a hermetically sealed package. During this deformation process, the locking elements are produced by impressing embossing means into the sidewalls of both package halves into a counter-support. This method is not suitable for very stable hard foils used as a bottom foil (product tray). 
         [0005]    On the contrary, the foils are subjected to cold forming in the area of the locking elements and this may lead to a formation of cracks and to indefinite differences in the wall thicknesses of the individual foils. This, in turn, may lead to leakiness and, consequently, to flaws in the package. 
         [0006]    Another drawback is the high impressing force of the embossing means required for simultaneously cold forming both foils in common. 
       SUMMARY 
       [0007]    It is an object of the present disclosure to provide a method for producing a reclosable package and a deep-drawing packaging machine for executing said method, in the case of which the above-described drawbacks can be eliminated. 
         [0008]    A method for producing reclosable packages according to the present disclosure comprises the following steps: in a first forming station, package trays are formed in a bottom foil and, simultaneously, locking elements are formed in the sidewalls of the respective tray formed. The heating of the bottom foil required for this forming process is effected e.g. via one or a plurality of heating stations and/or a heating plate integrated in the forming station. Subsequently, the respective package trays formed are filled with products in an area of the product insertion track. 
         [0009]    In a second forming station, a lid is formed in a normally slightly thinner top foil in such a way that flat surfaces are formed on the sidewalls of the lid, said flat surfaces covering the first locking elements of the package tray when said package tray and the lid have been combined. 
         [0010]    The package tray filled with products and provided with locking elements is supplied to a sealing station together with the top foil or the lid formed, said sealing station welding the top foil or the lid formed to the package tray under a vacuum and/or a modified atmosphere whereby a hermetically sealed package is produced. 
         [0011]    By means of a foil conveying system provided on both sides of the bottom foil, a group of packages, which are still interconnected through the bottom foil, is conveyed out of the sealing station and supplied to a downstream embossing station. In this embossing station, the top foil has embossed therein recesses, which match with the first locking elements of the package tray at least partially and which thus fulfill the requirement with respect to an audible snap when the package is being reclosed. 
         [0012]    According to the present disclosure, the first locking elements are formed on at least two opposed sides of the package tray in the first forming station. In this respect, it will be advantageous to provide a plurality of locking elements or an elongate locking element per side of the package tray, said locking elements cooperating with at least two recesses in the lid. The locking elements may, however, be formed in the package tray on each side thereof or, in the case of round/oval packages, at an arbitrary location. 
         [0013]    One variant of the method according to the present disclosure is so conceived that the locking elements of the package tray are configured such that they extend outwards, since this has hardly any negative influence on the forming process and since the forming tools need not have a more complicated structural design for this purpose. 
         [0014]    In an embossing station, the embossing of recesses in the top foil is preferably carried out by means of a counter support on the outer surface of the package tray. According to an advantageous embodiment, the shape of the counter support corresponds in certain areas thereof to the shape of the locking elements of the package tray. The shape of the recesses may be complementary to that of the locking elements, but it may also deviate therefrom, so that the lid can be closed and/or retained in the closed position more easily. 
         [0015]    A deep-drawing packaging machine according to the present disclosure provides a first forming station used for forming in a bottom foil at least one package tray and locking elements. The locking elements are adapted to be used for reclosing a package. In a second forming station of the deep-drawing packaging machine, a lid is formed in a top foil whereby flat surfaces are formed on the sides of the lid, said flat surfaces covering the locking elements of the package tray when said package tray and the lid have been combined. The deep-drawing machine comprises a product insertion region for inserting products into the package tray, and a sealing station for sealingly attaching the top foil or lid to the package tray. According to the present disclosure, an embossing station located downstream of the sealing station is configured for embossing into the top foil recesses which cooperate, at least in certain areas thereof, with the first locking elements formed in the package tray. 
         [0016]    According to an advantageous embodiment, the embossing station comprises at least one embossing tool for embossing the recesses into the top foil and a counter support which cooperates with the embossing tool and the package. It will be particularly advantageous to hold the package during the embossing operation at least in certain areas thereof on the edge and in the area of the sealing seam, respectively, so as to counteract the force of the embossing tool applied to the package. 
         [0017]    An inventive embodiment is so conceived that it comprises a forming station which is suitable for forming the locking elements of the package tray such that they extend outwards. 
         [0018]    It proved to be particularly advantageous when the embossing tool moves in a pivoting direction of movement. Alternatively, the movement can take place in a combination of vertical and horizontal movements. 
         [0019]    It will be advantageous to use a servomotor or a pneumatic cylinder as a drive for the embossing tool, since this also allows a continuously variable control of the penetration depth of the embossing tool in the top foil, whereby the reclosing characteristics of the package can be influenced. In particular the use of a pneumatic drive will be suitable for a maximum penetration depth of the embossing tool up to the counter support. 
         [0020]    In the following, an advantageous embodiment of the present disclosure will be described in more detail making reference to the below drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  shows a schematic side view of a deep-drawing packaging machine according to the pre-sent invention; 
           [0022]      FIG. 2   a  shows a schematic view of a package tray of a package; 
           [0023]      FIG. 2   b  shows a schematic view of a further package tray of a package; 
           [0024]      FIG. 3  shows a schematic view of a top foil of a package; and 
           [0025]      FIGS. 4   a ,  4   b ,  4   c  and  4   d  show schematic views of an embossing unit for forming recesses in the top foil. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    Identical components are always provided with identical reference numerals in the figures. 
         [0027]      FIG. 1  shows a deep-drawing packaging machine  1  comprising a forming station  2 , a sealing station  3 , an embossing station  4 , a cross-cutting unit  5  and a longitudinal cutting station  6 . Via a conveying system  7 , the packages  8  are conveyed out of the deep-drawing packaging machine  1 . A bottom foil  9  is unwound from a foil holder  10  and intermittently conveyed in a conveying direction R through the deep-drawing packaging machine  1  by means of a foil advancement system, which is not shown. In an insertion area  11 , the products  12  are inserted in a package tray  13 , which was formed in the bottom foil  9  in the forming station  2 . The package tray  13  having the product  12  inserted therein is supplied to the sealing station  3  together with a top foil  14 , said top foil  14  being deep drawn in a top foil forming station  15  so as to form a lid  14 ′. The bottom foil  9  and the top foil  14  are welded to one another, preferably under a modified atmosphere or under a vacuum. An embossing station  4  following the sealing station  3  forms recesses in the lids  14 ′ formed in the top foil  14 , the geometry of said recesses corresponding in certain areas thereof to that of locking elements  16  (cf.  FIG. 2   a ) of the package tray  13 . The locking elements  16  of the package tray  13  are deep drawn on at least two opposed sides of the package tray  13  in the forming station  2  under the influence of temperature, pressure and/or a vacuum. 
         [0028]      FIG. 2   a  shows a foil detail of a deep drawn package tray  13  (additional package trays in the foil compound are not shown) with two respective opposed locking elements  16 . These locking elements  16  can be arranged parallel to or transversely to the conveying direction R or they may be provided on additional or on all sides. The locking elements  16  are preferably configured as a longitudinal groove, as shown in  FIG. 2   b , so as to guarantee the area and force required for audibly reclosing the package  8  by reinstalling the lid  14 ′. The area  17  extending along the edge of the package identifies the sealing of the top foil  14  to the bottom foil  9  and the package tray  13 , respectively. When the package  8  is opened for the first time, said sealing is opened, i.e. detached in the area  17 . 
         [0029]      FIG. 2   b  shows a package tray  13  provided with continuous locking elements  16  extending parallel in the conveying direction R and arranged on both sides of the package tray  13 . 
         [0030]      FIG. 3  shows a detail of the top foil  14  in a condition in which said top foil  14  has been formed in the lid forming station  15  such that a deep-drawn area  18  of the lid  14 ′ can be installed in the open area of the package tray  13  whereby a lateral border  19  of the lid  14 ′ comes into contact with the inner wall of the package tray  13  and abuts thereon in certain areas so as to produce a sealing effect between the interior of the package and the environment. The lateral border  19  of the lid  14 ′ then covers the locking elements  16  of the package tray  13 . 
         [0031]      FIGS. 4   a  to  4   d  show various operating conditions of the embossing station  4  with embossing tools  20 . 
         [0032]    In  FIG. 4   a , the package  8  consisting of the package tray  13  and the top foil  14  sealed thereto has been transported into the embossing station  4  by a conveying unit, which is not shown, and the embossing tools  20 , which may also be heated, are pivoted into the area of the locking elements  16 , which have already been formed in the bottom foil  9  in the forming station  2 . 
         [0033]    In  FIG. 4   b  the embossing tools  20  continue their pivotal movement in the direction of the locking elements  16 . In the course of this process, the top foil  14  is deformed outwards towards the package tray  13 . 
         [0034]    As shown in  FIG. 4   c , the embossing tool  20  pushes the top foil  14  into the locking element  16  to such an extent that the recess  21  in the top foil  14 ′ comes, at least in certain areas thereof, into contact with the locking element  16  so as to obtain during opening and reclosing of the package  8  a perceptible effect with respect to a reliable and audible engagement between the locking element  16  and the recess  21 . 
         [0035]    A counter support strip  22  including a longitudinal groove oriented in the conveying direction R is configured in accordance with the shape of the locking element  16  and serves as a stop for the movement of the embossing tool  20 . 
         [0036]    For continuing the transport of the package  8 , the embossing tools  20  are pivoted away from the package collision area, as can be seen in  FIG. 4   d , and the package  8  can be advanced to an optional labeller, which is not shown. 
         [0037]    The locking element  16  may have the shape of a semicircle or of half an oval. A trapezoidal shape or a polygonal shape are, however, imaginable as well. This applies to the recess  21  as well. 
         [0038]    While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.