Patent Publication Number: US-6907715-B2

Title: Device for stretching a film in an automatic product packaging machine

Description:
The present application claims priority to Italian patent Application Serial No. MI 2002A 000686, filed Apr. 3, 2002. 
   BACKGROUND OF THE INVENTION 
   The present invention refers to a device for stretching a film in an automatic product packaging machine, in particular products of any thickness and size. 
   In the current method of distribution of publications such as envelopes, newspapers, magazines and books, with or without gadgets, wrapped in plastic and similar, there is the problem of packaging the products to facilitate automatic handling. This is particularly important in the field of postal sorters that do not accept film-packaged items where there is an excess of film with respect to the product, which in general causes jamming. 
   For said purpose the products must not be allowed to move freely inside the wrapping film as this prevents automatic handling. 
   This problem becomes even more evident when the film also contains additional inserts that tend to move, if the film does not tightly envelop the entire contents of the package. 
   Furthermore, it should not be forgotten that loose wrapping of the film on the products inside the package involves the use of more film than necessary which, with the large quantities used, involves an increase in packaging costs. 
   It should also not be forgotten that the variability in size and thickness of the packages does not always make it easy to obtain a tidy package in which the material inside can be checked by the packaging machine devices. 
   SUMMARY OF THE INVENTION 
   It is therefore the general aim of this invention to identify and produce a device for stretching a film in an automatic product packaging machine which solves all the above-mentioned technical problems. 
   A further aim of the invention is to produce a device of the type specified above that operates with any product thickness and size, without any problem. 
   A further aim of the invention is to produce a device that permits a certain saving on film, while performing correct accurate product packaging. 
   A further aim of the present invention is to produce a device that can be directly combined with a packaging machine already in use. 
   Yet another aim is to identify a device that makes performance of the correct packaging operations and, above all, subsequent handling of the packages thus obtained as automatic and rapid as possible. 
   These and other aims according to the present invention are achieved by producing a device for stretching a film in an automatic product packaging machine in particular products ( 12 ) of any thickness and size, spaced from each other at a pre-set distance, which are fed from a first conveyor belt ( 14 ) to a second conveyor belt ( 19 ) combined with a wrapping film feeder ( 26 ,  28 ), an oscillating longitudinal sealer ( 34 ) and a transverse sealer ( 35 ) for sealing said film wrapped over said products ( 12 ), wherein said device comprises a pair of drive rollers ( 25 ) for stretching said film ( 26 ) at the inlet of said second conveyor belt ( 19 ) and a cylinder ( 29 ) attached to a stem ( 32 ) fitted with an idle pressure roller ( 33 ) which engages said stretched film ( 26 ) on said second conveyor belt ( 19 ). 
   Further relevant characteristics of the present invention are illustrated in the subordinate claims. 
   The device according to the present invention therefore ensures correct packaging at all times of the products that arrive in succession spaced on a feed conveyor belt which conveys them, once packaged, to the subsequent handling and shipping operations. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     It should be noted that said device can be rapidly adapted to packaging lines already in use. 
     The functional and structural characteristics and the advantages of a device according to the invention will become more evident from the description of a form of embodiment illustrated as an non-restrictive example, with reference to the attached FIGURE. Said FIGURE shows schematically, in a side elevation view, a device for stretching a film in a machine for automatic packaging of products fed in succession, which is positioned between a first conveyor belt for feeding said products and a second conveyor belt which seals them in a film. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   With reference to the drawing, a device for stretching a film in an automatic product packaging machine according to the present invention is shown, indicated overall by number  11 , which is fed with products, schematised in  12 , of any thickness and dimension. These products  12  can be either single products or several products combined, also of different sizes, for packaging in the same film. 
   The products  12 , moved forward by a piston conveyor  13 , are arranged on a first feed conveyor belt  14 , on which they are spaced from each other by means of an upper spacer belt  15  which spaces the products  12  in succession. The spacer belt  15  is synchronised on roller  18  by a transmission  16  connected to a roller  17  of the first feed conveyor belt  14 . 
   A further roller  21  of a second conveyor belt  19 , positioned after the first belt  14 , is synchronised by a transmission  20  connected to a roller  17  of the first conveyor belt  14 . 
   The second conveyor belt  19  is controlled by a motor  22 , connected to an encoder  23 , to which a second motor  24  is connected, in its turn, controlling a pair of drive rollers  25 . 
   According to the invention, these rollers  25  feed a film  26  at a lower speed than that of the second conveyor belt  19 , thus acting as stretching elements for the film. Said speed of the pair of rollers  25  can be adjusted and correlated with that of the second conveyor belt ( 19 ). 
   This film is unwound from a reel  28  and serves to produce a finished package  27  at the outlet of the packaging machine, shown only partly. 
   According to the invention, furthermore, a cylinder  29  is provided, integral with a supporting structure  31  of the packaging machine by means of a pin  30  located at one end. A stem  32  protrudes, controlled by the cylinder  29 , and is fitted with an idle pressure roller  33 , which engages on the film positioned on the second conveyor belt  19 . This pressure roller  33  forces the film  26  to move forward from that point of contact with the second conveyor belt  19  at the same speed as said conveyor belt  19 , thus creating an element that engages the film  26  on the second conveyor belt  19 . 
   Alternatively, this engagement element can be a simple roller which engages via an elastic element or similar, of the adjustable type. 
   Naturally, as already said, the travel speed of the second conveyor belt  19  is higher than that of the pair of drive rollers  25  of the film  26 , thus stretching the film  26 . 
   The stretched film  26  moves forward on the second conveyor belt  19  and wraps in tubular fashion around the products  12  which are moving forward. An oscillating longitudinal sealer  34  and a transverse sealer  35 , which is raised and lowered, enclose the product  12  inside the stretched film. They operate in conjunction with a pressure belt  36  which is controlled at the same travel speed as the second conveyor belt  19  by means of a transmission  37  which connects it to the encoder  23  and to the main motor  22 . The pressure belt  36  also helps to keep the film  26  stretched. 
   Alternatively, the pressure belt  36  can be replaced by a belt with suction which is particularly useful for irregularly shaped products which must not be subjected to pressure. In this case the conveyor belt  19  can also be provided with a suction area corresponding to the upper suction belt  36 . All these elements constitute further means for maintaining the film stretched during the packaging and sealing phases with the product inside the film. 
   Immediately downstream of the transverse sealer  35  a suction box  38  is provided, connected to a vacuum pump  40 , which exerts suction on the product contained in the partially sealed film via a perforated conveyor belt  39 . This suction keeps the film  26  taut until the product has been finally sealed, after which it is de-activated and the packaged product, i.e. the package  27 , is released. 
   Alternatively to the suction box  38  an engagement roller  38 ′ can be provided which engages on the product contained in the film  26  positioned on a conveyor and keeps the film taut until transverse sealing has been completed and the product is completely packaged in the film. 
   This set of pressure elements or elements keeping the film tensioned or stretched guarantees a well-tensioned film until completion of longitudinal and transverse sealing of the film on the product, with well-tensioned final packaging. 
   The packaging obtained according to the present device is therefore free from all the disadvantages that previously limited its functionality. 
   In fact, the elimination of parts of film protruding from the packaging prevents obstruction of automatic package handling systems, thus avoiding jamming of the handling machine. 
   Stretching of the film, in fact, ensures that the film fully adheres to the product which also looks neat and well-packaged. 
   Furthermore, if inserts or other are combined with the product being packaged, they are well-secured in the film which, since it is stretched, adheres to the whole contents and, on release, adapts to the contents, thereby securing them. 
   Said use of the film which is placed stretched over the products, also offers a considerable saving on film during packaging. This saving on large quantities used for packaging involves a reduction in packaging costs. 
   It should also be remembered that said device can be easily installed also on existing packaging machines. In fact, it is sufficient to fit the component parts without having to modify the structure of the machine. 
   It is possible to obtain the required stretching by simply adjusting the pair of drive rollers  25 . In fact, a reduction or an increase in their speed with respect to the travel speed of the second conveyor belt  19  permits setting of the required degree of stretching. 
   It is obvious that the term “product” indicates a packaged or non-packaged product, single or composite with varying thickness, in the form of a publication or otherwise, for insertion into a film. Furthermore, as already said, the basic product, such as a newspaper, a magazine, a book or other, can be combined with at least one second product, of equal or different dimensions, that acts as an additional element, such as any type of gadget, a compact disc, a floppy disc, a perfume, or any other object of fairly limited size. 
   It is therefore evident that the present invention offers a simple convenient solution to the general problem previously referred to. 
   The stretching device of the present invention thus conceived is subject to numerous modifications and variations which all fall within the scope of the invention. 
   Furthermore, in practice the materials used, in addition to their dimensions and the components, may be of any type according to technical requirements.