Abstract:
An automatic cigarette maker and/or packer incorporates a welding or sealing head with an electrically conductive heating foil mounted to an electrically insulating backing element; the foil is retained on the backing element by an overlay of ceramic material, which is covered in turn by a further overlay of smooth silicone that can be offered in direct contact to a weldable or sealable wrapping material.

Description:
[0001]    This application claims priority to Italian Patent Application No. BO2007A000126, filed Feb. 27, 2007, which application is incorporated by reference herein. 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a machine for manufacturing and/or packing tobacco products. 
         [0003]    In particular, the invention finds application to advantage in machines equipped with devices of which the function is to weld or seal a wrapping material enveloping respective tobacco products. 
         [0004]    Conventionally, machines for manufacturing and/or packing tobacco products incorporate feed means by which the selfsame products are directed toward a welding/sealing station. 
         [0005]    In the case of cigarette makers, for instance, the aforementioned feed means advance a continuous cigarette rod toward a sealing device that serves to join together the overlapping longitudinal edges of a tubular wrap ensheathing a stream of tobacco filler. 
         [0006]    Thus, as the continuous cigarette rod advances, a heater head of the sealing device warms and activates an adhesive applied previously between the overlapping edges of the tubular wrap. 
         [0007]    The art field in question also includes machines by which packets of cigarettes enveloped initially in a heat-shrinkable wrapping material are advanced through the sealing station by a conveyor belt or a rotating drum. 
         [0008]    The single packets are conveyed normally in an ordered succession and stopped momentarily so that the heater head can engage an end face of the packet for a length of time sufficient to bond the free edges of the overwrap material. 
         [0009]    In particular, the welding/sealing head consists in a metal body furnished with a contact surface designed to engage a given portion of the wrap that needs to be welded or sealed. 
         [0010]    The welding/sealing head is activated by an electrical circuit that induces a current in the metal body and thus causes it to be heated by the Joule effect. 
         [0011]    The electrical circuit is piloted preferably by an electronic control system such as will regulate the current according to the temperature value that should register in the metal body. 
         [0012]    The aforementioned temperature value is selected on the basis of the type of material to be heated (packet overwrap, or cigarette rod paper), and the length of time the tobacco product remains in close proximity to the heated contact surface. 
         [0013]    Thus, having selected the speed at which products are fed through the welding or sealing station, the temperature at the contact surface of the metal body is regulated accordingly. 
         [0014]    Machines of the type in question are affected by an important drawback, however, attributable to the high thermal inertia of the heated metal body, that is to say the capacity of the body to cool down and heat up within a given period of time. 
         [0015]    As a result, the times involved in regulating the temperature of the metal body are somewhat lengthy. 
         [0016]    Consequently, if the speed at which the products advance should increase, the products will not be welded/sealed correctly until the contact surface is brought up to the appropriate temperature. Conversely, if the products begin to advance more slowly, they will be heated to excess and damaged. 
         [0017]    The object of the present invention is to provide a machine for manufacturing and/or packing tobacco products, such as will be unaffected by drawbacks of the type associated with prior art machines. 
         [0018]    In particular, the object of the invention is to provide a machine for manufacturing and/or packing tobacco products, equipped with welding or sealing heads in which thermal inertia is minimized. 
       SUMMARY OF THE INVENTION 
       [0019]    The stated objects are realized in a machine for manufacturing and/or packing tobacco products in accordance with the present invention, typically a cigarette maker and/or packer, equipped with a welding/sealing head that comprises an electrically conductive heating foil mounted to an electrically insulating backing element; the foil is retained on the backing element by an overlay of ceramic material, this covered in turn by a further overlay of smooth silicone such as can be offered in direct contact to a wrapping material being welded or sealed, without causing damage. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The invention will now be described in detail, by way of example, with the aid of the accompanying drawings, in which: 
           [0021]      FIG. 1  illustrates a machine for manufacturing and/or packing tobacco products according to the present invention, viewed schematically and in perspective; 
           [0022]      FIG. 2  shows a constructional part of a machine for manufacturing and/or packing tobacco products, viewed schematically in a side elevation and illustrating an alternative application; 
           [0023]      FIG. 3  shows a portion of a welding/sealing head forming part of the machine illustrated in  FIGS. 1 and 2 , viewed in perspective; 
           [0024]      FIG. 4  shows a welding/sealing head, viewed in a side elevation and in section; 
           [0025]      FIG. 5  is an exploded and perspective view of the welding/sealing head as in  FIG. 4 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]    With reference to the accompanying drawings, numeral  1  denotes a machine according to the invention, in its entirety, for manufacturing tobacco products and/or packing such products in a wrapping material. 
         [0027]    In practice, the present invention is applicable advantageously to tobacco products  2  of varying description, enveloped in a respective wrapping material  2   a  that presents a given portion  2   b  needing to be welded or sealed. By way of example, the products  2  in question might be packets  3  of cigarettes, or continuous cigarette rods  4 . 
         [0028]    To this end,  FIG. 1  shows a cigarette maker, or rather a machine  1  that manufactures cigarettes by forming a continuously advancing cigarette rod  4 . The rod  4  presents a tubular wrap  4   a  of which respective longitudinal edges  4   b  are overlapped in readiness to be sealed, as will be described in due course. 
         [0029]      FIG. 2  illustrates a constructional part of another machine  1 , namely a cigarette packer, in which the tobacco products  2  are packets  3  of cigarettes enveloped in a heat-shrinkable overwrap material  3   a.    
         [0030]    The overwrap material  3   a  presents free edges  3   b  positioned at an end face of the packet  3 , which must be sealed by the application of heat. 
         [0031]    With reference in particular to  FIG. 1 , the machine  1  presents an upstream end equipped with a tobacco feed and transport unit  100 , of which the function is to gather a mass of shredded tobacco into a continuous flow of tobacco particles. The component parts of the feed unit  100 , not described here in detail, being of conventional embodiment, are arranged in such a way as to direct the tobacco along a predetermined feed path toward a unit  101  by which it is formed into a continuous stream  102 . 
         [0032]    Two such streams  102  are illustrated, each caused to advance together with a web  103  of paper drawn from a roll  104 , following a path that passes through a print device  105  and toward a garniture tongue  106  on which the web  103  of paper is wrapped around the stream  102  of tobacco. The web  103  functions as the aforementioned tubular wrap  4   a  used to fashion the continuous cigarette rod  4 . Whilst the present invention is described and illustrated with reference to a twin track type of cigarette-making line with two garniture tongues, it is applicable likewise advantageously to lines having a single garniture tongue. 
         [0033]    The continuous rod  4  is advanced by feed means  5  along a respective feed direction D and through a welding/sealing station  6 , where the longitudinal edges  4   b  are joined permanently one to another. 
         [0034]    Located beyond the welding/sealing station  6  is a cutting station  107  where the continuous rod  4  is divided up by a rotary cutter device  108  into discrete cigarette sticks  109  of predetermined and constant length, and more exactly, twice the length of the stick that will ultimately form part of a single cigarette  110 . 
         [0035]    The cigarette sticks  109  are transferred to a filter attachment machine M of conventional type, not illustrated in detail. 
         [0036]    In the case of  FIG. 2 , the feed means  5  consist in a rotating drum  5   a  furnished with pockets, each containing a respective packet  3  of cigarettes. The packets  3  are advanced by the drum  5   a  along the feed direction D and through the welding/sealing station  6 . 
         [0037]    In both the solutions of  FIGS. 1 and 2 , the welding/sealing station  6  is equipped with at least one welding/sealing head  7  serving to heat the predetermined portion  2   a  of the product  2  mentioned previously. Preferably, the head  7  is carried below a respective holder element  8  not described in detail, being conventional in embodiment. 
         [0038]    To advantage, the holder element  8  can be coupled to motion-inducing actuator means  16  ( FIG. 2 ) of conventional embodiment, likewise not described in detail, rendering the head  7  capable of movement in a direction A transverse to the aforementioned feed direction D followed by the products  2 . 
         [0039]    Thus, as each packet  3  in turn is brought to a halt at the welding/sealing station  6 , the head  7  will move between an operating position of close proximity to the packet  3 , in which the edges  3   b  of the overwrap material  3   a  are bonded, and an idle position distanced from the packet  3 . 
         [0040]    As illustrated to advantage in  FIG. 4 , the welding/sealing head  7  consists in a heating foil  9  associated with a respective backing element  10 . 
         [0041]    More particularly, the foil  9  is electrically conductive and appears substantially as a plate, presenting a first surface  9   a  breasted with the backing element  10 , and a second surface  9   b  opposite to the first, directed toward the relative tobacco product  2 . 
         [0042]    Preferably, the foil  9  presents a substantially rectangular peripheral outline ( FIG. 3 ) and is furnished with connectors  11  extending from respective shorter sides  11   a  of the foil  9 . To advantage, the connectors  11  are associated with an electrical circuit, not illustrated in the accompanying drawings, such as will direct an electric current through the foil  9  and cause it to heat by the Joule effect. 
         [0043]    Moreover, the electrical circuit is coupled to an electronic control system of conventional type governing the electric current, likewise not illustrated in detail, such as will determine the temperature value registering in the foil  9 . 
         [0044]    In this way, the temperature of the foil  9  can be regulated on the basis of the rate at which the products  2  advance, hence the time for which each product  2  remains exposed to the head  7 . 
         [0045]    The gauge of the foil  9 , preferably a metal, will be less than 0.4 millimeters, and ideally 0.1 mm. 
         [0046]    As illustrated to best advantage in  FIG. 3 , the foil  9  is pierced at least in part, and preferably of mesh type embodiment, so as to minimize thermal inertia in the electrically conductive material. 
         [0047]    More precisely, the foil  9  presents a central portion  12  appearing as a grid, created by a plurality of through holes  12   a.    
         [0048]    To reiterate, the first surface  9   a  is offered to the backing element  10 , which appears substantially parallelepiped and rectangular in section. 
         [0049]    Advantageously, the backing element  10  is made of an electrical and heat insulating material. In a preferred embodiment, the backing element  10  will be ceramic or silicone, and of thickness between 4 and 5 millimeters. 
         [0050]    The backing element  10  is therefore appreciably thicker than the foil  9  ( FIG. 4 ), in order to guarantee the strength and rigidity of the head  7  and ensure that the holder element  8  is suitably heat-insulated, thereby preventing the transmission of heat to other parts of the machine  1 . 
         [0051]    The foil  9  is anchored to the backing element  10  by means of a first overlay  13  covering the entire second surface  9   b  presented by the foil  9 . 
         [0052]    This first overlay  13  consists in a film of ceramic material less than 0.4 millimeters thick, and ideally, 0.1 mm thick 
         [0053]    To retain the foil  9  on the backing element  10 , the material of the first overlay  13  passes through the holes  12   a  presented by the pierced structure of the central portion  12 , from one face of the foil to the other. 
         [0054]    In this situation, the foil  9  effectively remains sandwiched between the backing element  10  and the first overlay  13 , both of which are ceramic. As a result, the foil  9  remains electrically insulated and thereby prevented from entering into contact with certain electrically conductive components of the tobacco products  2 , like the metal foil paper wrapping contained in cigarette packets  3 , which could provide a route for current leakages or short circuits. 
         [0055]    Also, the foil  9  is protected from any oxidation that could be caused by the nature of the material from which it is made, and the continual variation in temperature to which it is subject. 
         [0056]    Observing  FIG. 4 , moreover, it will be seen that the first overlay  13  is particularly thin, presenting a thickness identical, or substantially identical, to that of the foil  9 . Consequently, even though the first overlay  13  may be made of a heat-insulating material, it does not impede the transmission of heat toward a product  2  positioned in close proximity. Finally, the welding/sealing head  7  comprises a second overlay  14  covering the entire first overlay  13 . 
         [0057]    The second overlay  14  consists preferably in a film of silicone having a thickness nominally between 0.01 and 0.1 millimeters, preferably between 0.02 and 0.07 mm, and ideally 0.05 mm. 
         [0058]    The second overlay  14  affords a smooth outer surface  15  offered in contact to the predetermined portion  2   a  of the tobacco product  2 . 
         [0059]    Advantageously, the second overlay  14  will also be particularly thin, and more precisely, thinner than the first overlay  13 . Accordingly, the second overlay  14 , like the first, will not impede the transmission of heat to a product  2  breasted with the outer surface  15 . 
         [0060]    The silicone material utilized for the second overlay  14  affords a particularly smooth and non-abrasive contact surface  15 , unlike the ceramic material, which is notoriously porous. 
         [0061]    To further advantage, considering the application illustrated in  FIG. 1 , where the cigarette rod  4  is heated while in motion, no damage is caused to the tubular wrap  4   a  as it slides against the outer surface  15 . In addition, the fact that the contact surface  15  has a non-porous structure makes it easy to clean. 
         [0062]    Significantly, as mentioned above, the heating foil  9  has a low thermal inertia, by virtue of its minimal thickness and its pierced structure. 
         [0063]    The temperature of the foil  9  can therefore be regulated swiftly, depending on the speed at which the products  2  advance, so as to ensure that the respective predetermined portions  2   a  of the products  2  are heated to optimum effect. 
         [0064]    In other words, the foil  9  can be brought swiftly to the appropriate temperature for the particular welding or sealing operation.