Patent Publication Number: US-9834366-B2

Title: Thermal bag for foods and the like

Description:
TECHNICAL FIELD 
     The present invention relates to improvements to thermal bags, typically used to transport frozen products. 
     BACKGROUND OF THE INVENTION 
     Bags of this type are formed of composite material and normally include an outer sheet, typically a sheet of metallized polymer film, an inner sheet of polymer film defining the inner surface of the bag and a thermally insulating intermediate sheet disposed between the outer sheet and the inner sheet. These sheets are folded to form the bottom of the bag and the outer and inner sheets are welded together along the borders. A handle with closing members is normally provided at the level of the mouth. 
     Bags of this type have relatively small capacities and can tear if loaded excessively. 
     Thermal bags of this type are described in FR-A-2550768, in FR-A-2587302 and in US-A-2003/0035596. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     The object of the present invention is to produce a bag of the aforesaid type with increased capacity, which is more practical to use and is less likely to tear if it is overloaded. 
     In substance, according to the invention this and other objects, which shall be apparent to those skilled in the art from reading the text hereunder, are obtained with a bag as claimed in claim  1 . The dependent claims relate to further advantageous developments and improvements of the invention. 
     In substance, the invention relates to a thermal bag made of thermally insulating composite material, folded to form a bottom and welded along lateral borders to form a body of the bag with a mouth at the level of which a handle is applied; wherein the composite material defines a bottom folded in an accordion-like fashion opposite the mouth of the bag, and wherein a laminar stiffening element of the accordion-like bottom is disposed inside the bag. 
     Preferably, the laminar stiffening element is separated from the composite material forming said bag. This simplifies the production process as the aforesaid element can simply be positioned loose in the bag and does not require particular operations to fasten it to the walls of the bag. 
     According to a possible particularly advantageous embodiment, the composite material is composed of a first outer sheet, a second inner sheet and a thermally insulating sheet interposed between said outer sheet and said inner sheet. 
     In a possible embodiment of the bag according to the invention, in the folded position the accordion forming the bottom of the bag has beveled borders along which welding lines are produced, the beveled borders on each side of the bag converging in a corner, the two opposed corners being joined by a folding line of the accordion-like bottom. Along the beveled borders welds can advantageously be formed between opposite portions of the inner surface of the second inner sheet of the composite material forming the bag. 
     To obtain a bag which is more functional and efficient in preserving the products inserted therein, in an improved advantageous embodiment of the invention the laminar stiffening element contains a refrigerating fluid, such as a mixture of water and monopropylene glycol. 
     In a possible embodiment the laminar stiffening element is made of cellular plastic, such as cellular polypropylene. 
     In a different embodiment, the stiffening element is made of cardboard enclosed in a cover made of a polymer material. 
     The outer sheet of the composite material forming the body of the bag can be composed of a multilayer metallized polymer material. This multilayer metallized polymer material can be composed of a polyester (PET) and low density polyethylene (LDPE) laminate. 
     In a possible embodiment the outer sheet made of multilayer polymer material has two outer layers in a material weldable to itself. For example, the outer sheet can be composed of a laminate comprising a layer of polyester (PET) interposed between two layers of low density polyethylene (LDPE) or of a coextruded multilayer of polypropylene, polyester and low density polyethylene. By way of example, said three layers can have a thickness of 25, 12 and 40 micrometers. 
     The composite material forming the body of the bag can also have a thermally insulating intermediate sheet composed of a foamed polymer material, such as a foamed low density polyethylene with closed cells. 
     The inner layer of composite material can be composed of low density polyethylene. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood by following the description and accompanying drawing, which shows a non-limiting practical embodiment of the invention. More specifically, in the drawing: 
         FIG. 1  shows a perspective view of a bag produced according to the invention in an open position; 
         FIG. 1A  shows a perspective view of a bag according to the invention in a modified embodiment; 
         FIG. 1B  shows a section according to IB-IB in  FIG. 1A ; 
         FIG. 2  shows a side view II-II of  FIG. 1 ; 
         FIG. 3  shows a front view of the bag in a folded position; 
         FIGS. 4 and 5  show cross sections according to a vertical plane of the bag in an intermediate opening phase and in an open position respectively; 
         FIG. 6  schematically shows the steps to produce the bag according to the invention; 
         FIG. 7  shows a schematic enlargement of the detail indicated with VII in  FIG. 4 . 
         FIGS. 8A, 8B and 9  show a plan view of the production line and a side view of the initial area for insertion of the initial continuous material to produce the bags;  FIGS. 8A, 8B  representing two subsequent portions of the line. 
     
    
    
     DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION 
     The bag, indicated as a whole with  2 , has a body  1  formed of a portion of composite laminar material. This material is folded to form a bottom of the bag with an accordion-like configuration and is welded along two lateral borders  3 . The mouth of the bag is indicated with  5 , welded along which is a handgrip or handle, formed by the portions  7 A and  7 B, which also form a closing device of the mouth of the bag. 
     The bottom of the bag  2  has an accordion-like configuration and is defined by a portion of the composite material folded along a central folding line  9  and two lateral folding lines  11 . The folding lines  9  and  11  define two edges  12  of composite material which form the accordion defining the bottom of the bag. In the folded position ( FIG. 3 ) it can be seen that the edges  12  are beveled and the bag has a lower portion defined, besides by the folding lines  11 , by pairs of welding lines  13  inclined by approximately 45° with respect to the welded borders  3 . In the extended position the accordion formed by the edges  12  and by the folding lines  11  and  9  takes the configuration shown in  FIG. 5  and a laminar stiffening element  15 , which is physically detached from the composite material forming the body  1  of the bag  2 , rests on the inner surface of the extended accordion. 
     The composite sheet material which forms the body  1  of the bag  2  has (see enlargement in  FIG. 7 ) a first outer sheet  1 A, a second inner sheet  1 B and an intermediate sheet  1 C. In a possible embodiment the intermediate sheet  1 C is composed of a foamed polymer material, typically and preferably a closed cell foamed material, such as a low density polyethylene (LDPE). The innermost sheet  1 B can, for example, be composed of low density polyethylene, while the outer sheet  1 A can be a coextruded multilayer material. In a possible embodiment the sheet  1 A is composed of two layers, where the outer layer is polyester (PET) and the inner layer is low density polyethylene (LDPE). The outer layer is suitably metallized with aluminum. 
     With the configuration of the beveled accordion-like bottom shown in  FIG. 3 , the welding lines  13  are produced on opposite edges of the inner sheet  1 B made of polyethylene or another weldable material. Being made of polyester, the faces opposite and in reciprocal contact of the outermost sheet  1 A are not reciprocally welded. The bevel of the corners of the bottom of the bag make it possible to obtain, in the open position ( FIG. 1 ) a bag without protruding corners, which otherwise would form in the absence of bevels along the welding lines  13 . 
     To avoid beveling the base material forming the body  1  of the bag, an outer sheet  1 A composed of a coextruded three-layer material, such as an intermediate layer of polyester and two outer layers of low density polyethylene, can be used. The second material can be welded to itself so that when the accordion forming the bottom of the bag is in the folded position, the bag can extend quadrangularly with borders  3  welded up to the folding lines  11  of the accordion-like bottom. In this case, opening the accordion the bag approximately maintains the shape of a parallelogram without protruding edges and with a welding border  3  which extends from the mouth  5  to the extended bottom. A bag produced in this way is shown in  FIG. 1A . 
     Inserted inside the bag is a laminar stiffening element  15  rectangular in shape and with dimensions corresponding to the open accordion-like bottom ( FIGS. 1 and 5 ). 
     The laminar stiffening element can, for example, be composed of a sheet of cellular polypropylene or also corrugated cardboard covered with a plastic film to avoid deterioration caused by condensate which can form on the products contained in the bag  2 . 
     According to an advantageous embodiment, the rigid bottom can be made of plastic material, such as polypropylene, optionally cellular, inserted into a bag of polymer film, such as polyethylene or polyamide, containing a refrigerating mixture, i.e. a mixture capable of storing cold. Typically, this mixture can, for example, be a mixture of water and monopropylene glycol. As the laminar stiffening element is inserted loosely inside the bag, it can be removed from said bag and placed in a freezer to take the refrigerating mixture to low temperature. In this case, the stiffening element is used to stiffen the bottom of the bag and increase the stability and strength of the bag, consequently facilitating the use thereof, and also to preserve the degree of cold inside through storage of cold energy in the mixture contained in the cover surrounding the laminar stiffening element. 
     As can be seen in particular in  FIG. 3 , the handle or handgrip  7 A,  7 B has a dimension in length L less than the length La of the edges forming the mouth  5  of the bag, when said bag is flattened. Advantageously, the length L is less than the length La by an amount 2l, equal to or slightly less than the width of the accordion (see  FIG. 2 ), when this is flattened, i.e. when the bag is in the position of maximum volume. This dimension 2l is therefore substantially more or less equal to or slightly less than the transverse dimension of the laminar stiffening element  15 . More or less equal to or slightly less than is intended as a difference of the two lengths ranging approximately from 0 to 20%. In other words, the mouth of the bag can be smaller in dimensions to the flattened accordion, with a difference between the width of the mouth and the width of the accordion preferably no greater than 20%. This dimensioning of the handle allows the bag to take the completely open position shown in  FIGS. 1 and 2 , without the handle preventing the bag from being opened. 
     Moreover, to obtain a bag with sufficient capacity and stability in the open position, it is advantageous for the dimension 2l to be sufficiently large, typically approximately half the height H of the bag. In other words, the distance between the folding lines  11  and  9  (equal to l) is preferably approximately a quarter or more of the height of the bag. 
     The bag can be produced in a completely automated manner, as shown schematically in the sequence of operations in  FIG. 6 . The continuous composite material is folded in line, as shown in the section B-B, along three parallel longitudinal folding lines, indicated with  9  and  11 , corresponding to the folding lines  9  and  11  on the finished article. Subsequently, the composite material is welded along the lines  3  and  13  and subsequently cut along the same lines to separate the bags  2  from one another and eliminate the triangular scraps S at the level of the inclined welding lines  13 . The laminar stiffening element  15  is inserted through the mouth of the bag and the two components of the handle  7 A and  7 B, which have already been joined to each other, are applied along the two longer edges defining the mouth  5 . 
     The entire process can take place without requiring manpower and consequently in totally hygienic conditions with a particular advantage in consideration of the fact that this type of container is intended to be used for foods. 
       FIGS. 8A, 8B and 9  show a more detailed representation of the production line. The composite material to produce the bags is unwound from three separate reels B 1 , B 2  and B 3  respectively containing: the metallized web material M 1  forming the outer layer of the composite material; the insulating web material M 2  forming the intermediate layer of the composite material; the inner web material M 3 . The three superimposed layers M 1 , M 2  and M 3  are taken, by a position on the plane of the three materials M 1 , M 2  and M 3  with the longitudinal borders thereof L 1 , L 2  adjacent and, by means of a folding triangle  101  are folded along the folding lines  9  and  11  corresponding to the lines  9  and  11  of the finished bag. 
     A pair of rollers  103  draws the composite material, indicated with Mc, according to the arrow F along a series of processing stations described hereunder. A fixed or rotating (motorized or idle) disc-shaped element  104 , or other element with the same function, can be positioned directly downstream of the rollers  103 . The function of this element is to stabilize folding  9  of the material M 1 , M 2 , M 3  obtained by the folding triangle  101 . 
     Downstream of the element  104  is a first station  105  comprising a welding device  107 , which performs welding along inclined lines corresponding to the welding lines  13  of the finished bag. Downstream of the station  105  is a station  109  for inserting the laminar stiffening elements. A manipulator  111  picks up individual laminar elements from a pile (not shown) and inserts them between the edges L 1 , L 2  held suitably spread apart by a spreading device schematically indicated with  113 . Downstream of the station  109  is another station  115  in which the welding lines  13  performed by the welding bars of the welding device  107  are cooled, by cooling bars, e.g. chilled by cold water delivered from a cooling system, not shown. 
     Downstream of the station  115  is a station  117  in which two scissor blades or the like, cooperating with fixed blades, cut the trimming delimited by the welding lines  13  and the folding lines  11 . 
     In the subsequent station  119  the handles  7 A,  7 B are applied to the edges L 1 , L 2  which for this purpose are held spread apart by a spreading device  121  and in the subsequent station  123  welding is performed by a welding system  125  of the portions  7 A,  7 B of handle to the longitudinal borders L 1 , L 2  and reciprocal welding of the materials M 1 , M 2  and M 3  along said borders. 
     In the subsequent station, indicated with  127 , a transverse welding bar  129  is provided to perform welding along transverse lines that will define, on the finished bag, the welded edges  3 . The weld has a width (i.e. a dimension in machine direction F) equal to double the width of the weld of the border  3  of each bag. Downstream of the cooling station  131 , in which a chilled bar  133  cools this transverse weld, is a cutting station  135  in which a scissor blade cooperating with a counter-blade, or a hot wire system or the like, performs the transverse cut and separates the individual bags  1  along the welding lines made by the welding bar  129 . 
     When the bag is produced as in  FIG. 1A , with the external material M 1  which can be welded to itself, or when the triangular trimmings at the sides of the bottom do not require to be eliminated, the station  117  can be omitted or left idle. 
     Moreover, according to a different embodiment, the welds along the borders  3  and  13  can be produced in a single station as can cooling of the welds. In this case welding takes place downstream of the station  109  and preferably downstream of the station  123 . However, in this case it is more complex to modify the dimension of the accordion-like bottom portion of the bag, and in particular the distance between the folding lines  11  and the folding line  9 . This is because the position and dimension of the welding lines  13  must be modified. This requires modification of the welding blade and of the cooling bar, which will have a Y-shape. With the configuration in  FIGS. 8A, 8B , on the other hand, the dimension of these welding lines, performed in the station  105  and cooled in the station  115 , can be modified simply by moving the bars or welding blades transversely with respect to the machine direction F. This is also the case for the cooling bars of the cooling station  115  and for the cutting blades in the station  117 . 
     If the weld along the inclined lines  13  and the transverse lines  3  is performed in an single station with a single shaped welding bar or blade, a single shaped cutting blade can be provided to perform, in just one movement, the cut along the welding lines. Vice versa, a double cutting station, or a double cutting arrangement can be maintained: transverse along the borders  3  and inclined along the lines  13 . 
     Although less advantageous, it would also be possible first to perform the transverse welding line at the level of the border  3  of the bag and, downstream thereof, the inclined welding lines at the level of the welding borders  13 . 
     It is understood that the drawing purely shows an example provided by way of a practical embodiment of the invention, which may vary in forms and arrangements without however departing from the scope of the concept on which the invention is based.