Abstract:
A tray of sheet paper material for containing foodstuffs in which there is a bottom and a side wall emerging therefrom and defining, in cooperation with said bottom, a holding space facing upwardly under use conditions of the tray; the side wall is defined by alternated straight portions and curved portions both having upwardly-facing flat surfaces ( 7, 9 ) to allow engagement of a closing film heat-sealed thereto; the straight portions ( 4 ) also have reinforcing tabs in engagement at the lower part thereof with the flat surfaces ( 7 ) and the tray is also provided with a reinforcing edge ( 10 ) folded downwardly along the whole upper perimeter of the container itself. The tray thus made has excellent features of mechanical resistance to deformations.

Description:
FIELD AND BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a tray for containing foodstuffs and to the method of producing the same. In detail, the invention relates to a container of paper material intended for conservation and possible cooking of foods such as lasagne, prepackaged dishes, etc.  
         [0002]     It is known that there is on the market a great number of food containers made of paper material and adapted to allow conservation and/or cooking of products of different nature.  
         [0003]     Containers defined by a flat bottom wall of substantially rectangular shape from which a side wall emerges and is adapted to delimit, in cooperation with the bottom wall, a holding space set to receive the appropriate food are well known.  
         [0004]     Such a holding tray is then provided, at the upper part thereof, with an outwardly-bent edge capable of defining a continuous flat surface over the whole upper periphery of the container.  
         [0005]     The flat surface (with an extension parallel to that of the bottom wall) defined by the bent edge is susceptible of enabling closure of the holding space by use of a plastic film for example, heat-sealed along the whole peripheral surface.  
         [0006]     While these trays (obtained by a series of bending operations in succession starting from a flat sheet of paper material) have been widely spread and used, the same products are not however devoid of technical and/or operating limits and drawbacks.  
         [0007]     The containers of the described type have a weak resistance to deformations, in particular to deformations taking place at the side walls. Actually, these containers do not offer a satisfactory resistance against forces directed transversely of the side walls, which results in the risk that deformations due to handling of the container already filled with the foodstuff may cause escape of the product.  
         [0008]     The above mentioned drawbacks have been at least partly eliminated by providing a tray as previously described applying a further rim of paper material, by gluing, close to the sealing surface so as to make the bent edge a two-layered edge and therefore increase the resistance to deformations transversely of the side wall.  
         [0009]     This solution too however, has many drawbacks. First of all the presence of glue and elements of different nature in engagement with each other can cause foodstuff contamination and also enable the humidity contained in the food to penetrate the paper fibres wetting them and therefore greatly lowering the resistance to stresses of same container.  
         [0010]     On the other hand, it is to be noted that, from the standpoint of the manufacturing costs, arrangement of this further reinforcing element is carried out starting from a flat sheet of paper material suitably cut out only a minimum portion of which is used whereas most of the material is to be discarded.  
       SUMMARY OF THE INVENTION  
       [0011]     Accordingly, the present invention aims at substantially solving all the mentioned drawbacks. It is a first aim of the invention to devise a tray of paper material that is provided with the necessary structure features enabling to withstand the transverse deformations of the side walls thereof.  
         [0012]     Another aim of the present invention is to obtain a container for foodstuffs made of paper material in which the food cannot come into contact with glue or the like and also cannot transfer its humidity to the cellulose fibres so as to maintain the mechanical-resistance features of said fibres as much as possible unimpaired.  
         [0013]     It is a further aim of the invention to obtain a product of paper material of reduced costs by decreasing or eliminating the working rejects as much as possible.  
         [0014]     It is a still further aim of the invention to obtain trays for containing foodstuffs that are of simple manufacture and require a limited number of manufacturing operations.  
         [0015]     The foregoing and further aims that will become more apparent in the course of the following description are substantially achieved by a tray for containing foodstuffs, and by a method for manufacture of same as recited in the appended claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0016]     Further features and advantages will be best understood from the detailed description of a preferred but not exclusive embodiment of the invention with reference to the accompanying drawings, in which:  
         [0017]      FIG. 1  shows a plan development of a tray in accordance with the present invention;  
         [0018]      FIG. 1A  shows the plan development of an alternative embodiment of a tray in accordance with the invention;  
         [0019]      FIG. 2  shows an intermediate passage of the production steps of the tray in accordance with the present invention;  
         [0020]      FIG. 3  is a view of the tray in accordance with the invention;  
         [0021]      FIGS. 4 and 5  show a section of the side wall of the tray at a straight portion of the side wall and a curved portion of the same side wall, respectively; and  
         [0022]      FIG. 5A  shows the section of a curved portion of a tray in accordance with an alternative embodiment of same. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]     With reference to the drawings, a tray for containing foodstuffs has been generally identified with reference numeral  1 .  
         [0024]     The container is fully made of paper material starting from a flat sheet of the type shown in  FIG. 1 , as better clarified in the following.  
         [0025]     In detail, the tray is intended for conservation and possible cooking of foodstuffs, such as prepackaged products for example.  
         [0026]     As can be seen from the accompanying drawings, the tray has a flat bottom wall  2  from which a side wall  3  emerges that, in cooperation with said bottom wall  2 , defines a holding space  6  set to receive the appropriate food.  
         [0027]     While not essential, bottom  2  can be of a substantially rectangular shape the sides of which are connected with each other by short curved sections.  
         [0028]     In this way the side wall  3  emerging from said bottom will show respective straight portions  4  emerging from the straight sections of bottom  2 , alternated with curved portions  5  (defining the tray corners) emerging from the respective curved sections of said bottom  2 .  
         [0029]     Since the tray is fully made starting from a flat sheet, the curved portions  5  will obviously have excess material that will be formed into pleats or the like (see  FIGS. 2 and 3 ).  
         [0030]     Therefore, the straight and curved portions  4 ,  5  of the side wall  3  define an inner holding surface  11  without a break. In other words, due to the fact that the present tray is obtained starting from a flat sheet, no cracks, cuts or the like that may give rise to leakage of the product contained therein can exist on the side wall or the inner holding surface.  
         [0031]     The upper region of the side wall  3  where the different folded edges are defined is now examined, and the following can be noticed as regards the engagement surfaces for reinforcement of the tray itself.  
         [0032]     First of all at least one straight portion  4  of the side wall  3  comprises a flat surface  7  facing upwardly and having a flat development substantially parallel to the bottom development.  
         [0033]     A reinforcing tab  8  (see  FIG. 2  in particular) is designed to be associated during the production steps at the lower part of the tray with the flat surface  7 , as visible in the section in  FIG. 4 .  
         [0034]     The curved portion of the side wall  3  too comprises a respective flat surface  9  facing upwardly as well, and having a development parallel to the development of the bottom wall.  
         [0035]     Obviously, due to the presence of excess material (since the tray is manufactured starting from a flat sheet of paper material), the flat surface  9  too will have respective pleated or crimped regions, or the like.  
         [0036]     Finally, at least one straight portion  4  and one curved portion  5  of the side wall  3  will have respective outer reinforcing edges  10  folded transversely (for example at right angles) with respect to the flat surfaces  7 ,  9  ( FIGS. 3, 4  and  5 ).  
         [0037]     As can be easily understood looking at the accompanying drawings, each straight portion  4  has the respective reinforcing tab  8  joined to the respective flat-surface  7  without a break; tab  8  will be then folded down against the lower side of surface  7  when the tray is assembled.  
         [0038]     The reinforcing edge  10  too extends over the whole side perimeter of the tray without a break and in such a manner that an optimal resistance to stresses transverse to the side wall is ensured.  
         [0039]     Therefore, taking into account the above described structure, the side wall will be in section as shown in  FIGS. 4 and 5 . In particular, the reinforcing edge  10  will be a two-layered edge at the straight portions (see  FIG. 4 ) and will consist of one layer alone at the curved portions  5  (see  FIG. 5 ).  
         [0040]     In addition, the presence of the flat surfaces  7  and  9  along the whole upper edge of the tray allows engagement of possible closing films therewith, which films are heat-sealed for conservation of the foodstuff.  
         [0041]     Advantageously, the tray has no other elements of paper material added by gluing, stapling or the like. In other words, arrangement of suitable reinforcing rims or other elements is not required in order to define the structural-resistance features of the container or modify the container structure.  
         [0042]     With reference to the alternative embodiment shown in  FIG. 1A , reinforcing tabs  8  can be provided with end portions  8 A that, once folded back, are adapted to abut against the lower side of the flat surfaces  9  defined by the curved portions. In this way the four tray corners are reinforced as well and they show in transverse section a double wall (see  FIG. 5A ).  
         [0043]     After describing the invention from a structural point of view, the method of manufacturing the tray shown in  FIG. 3  is the following.  
         [0044]     First of all a flat sheet of paper material having the appropriate size and basis weight is set and a portion of the type shown in  FIG. 1  is cut out therefrom.  
         [0045]     Then a drawing operation is executed on the sheet in order to define bottom  2  and the side wall  3  emerging from said bottom. In particular, bending at least along line A in  FIG. 1  is carried out. Then a bending operation along the chain line denoted at B in  FIG. 1  is carried out (obviously this operation can be executed simultaneously with the preceding one) in order to define an upwardly-facing flat surface  7 ,  9  at an upper region of the side wall.  
         [0046]     Once the above operations have been completed, the flat sheet has passed from the condition shown in  FIG. 1  to the condition shown in  FIG. 2 . Under this situation, folding of a predetermined number of reinforcing tabs  8  against the lower side of the flat surface  7  is carried out at each of the straight sides (folding line C in FIG.  1 ). Optionally these tabs can be glued to the lower side of the flat surface  7 .  
         [0047]     Then a further bending operation at the upper region of the side wall is executed in order to obtain the reinforcing edge  10  transverse to the flat surfaces  7 ,  9  over the whole perimeter of the side wall  3  so that the configuration shown in  FIG. 3  is reached and the finished product is obtained (folding lines D, E in  FIG. 1 ).  
         [0048]     Following the above described bending and folding operations, at the straight portions an edge of the type shown in section in  FIG. 4  is obtained and at the curved portions an edge of the type shown in section in  FIG. 5  is obtained.  
         [0049]     The invention achieves important advantages.  
         [0050]     First of all the tray in reference is obtained starting from a single flat sheet of paper material. In other words, no waste of paper material exists and therefore an important reduction in the costs connected with the raw materials is obtained.  
         [0051]     In addition, the tray is obtained by simple folding operations that could possibly be made by a single production machine during few operating steps in succession.  
         [0052]     The structure of the tray as made allows an excellent resistance to stresses transverse to the side walls and in addition no gluing regions are present at the foodstuff-holding space.  
         [0053]     Due to the absence of any cut, hole or the like, the paper material is inhibited from getting into contact with the humidity or water contained in the foods, which could weaken it and make the tray lose its structural features.  
         [0054]     The container of the invention is very practical, can be piled up and can be easily reproduced and is also provided with the necessary flat surfaces for carrying out heat-sealing of plastic closure films for conservation of the foods contained therein.