Abstract:
A spray gluing unit in a machine for wrapping products advancing along a pass line comprises a gluer equipped with a nozzle having an outlet from which adhesive is directed onto a wrapping material enveloping the products, and a cleaning station equipped with a first movable member carrying a scraper blade and a wetting pad to which silicone oil is supplied; the scraper blade and the wetting pad are designed to interact with a flat surface of the gluer and with an end face of the outlet, occupying substantially the same plane, so as to remove any residual adhesive from the gluer and keep the outlet moistened.

Description:
BACKGROUND OF THE INVENTION The present invention relates to a spray gluing unit.  
         [0001]    The invention finds application to advantage in the art field of packaging machines, and packers in particular, to which explicit reference will be made in the following specification albeit implying no limitation in scope.  
           [0002]    The need exists in such machines for an adhesive substance to be applied to predetermined portions of paper material, for example flat diecut blanks folded ultimately into containers or packets, or to labels that will be affixed to such containers or packets.  
           [0003]    It is standard practice in machines of the type in question to employ spray gluing units disposed facing a pass line, along which sheets for gluing are caused to advance, each such unit comprising at least one spray gluer with a nozzle connected to a circuit supplying the adhesive substance.  
           [0004]    Spray gluing units of the aforementioned type betray the drawback that the nozzles need servicing and cleaning at frequent intervals, due especially to the fact that traces of the adhesive substance tend to dry on the nozzle tips whenever a temporary and/or prolonged stoppage occurs during operation of the machine.  
           [0005]    In particular, the nozzles employed are furnished generally with outlets having tips of conical or frustopyramidal geometry, and it is on the outer surfaces of these tips that the sprayed adhesive becomes lodged and clings, due to its viscosity, forming encrustations and residues that compromise the correct operation of the gluer especially when the residues in question have dried.  
           [0006]    The accumulated residues need to be removed, and accordingly the prior art embraces gluing units in which the nozzle is capable of movement between an operating position, in which the adhesive substance is sprayed onto the aforementioned sheets, and a cleaning station where the nozzle is subjected to the action of means serving to remove any deposits of the adhesive substance that may have dried, or simply to prevent the deposits from drying.  
           [0007]    Alternatively, in certain types of machine, the means by which the residues of adhesive are removed can themselves be made capable of movement and thus offered to the nozzle, which remains substantially motionless in the operating position, although the cleaning operation is essentially no different.  
           [0008]    The operation of cleaning the nozzle is in any event a difficult one. Owing to the aforementioned geometry of the nozzle, which presents sharp corner edges, cleaning means of mechanical type will tend to be particularly complex, whereas cleaning means of hydraulic type, using jets, require particularly high operating pressures that can produce overspray and cause the cleaning liquid to splash undesirably on other parts of the machine.  
           [0009]    The object of the present invention is to provide a gluing unit unaffected by the drawbacks mentioned above, while being functional, economical and of compact dimensions.  
         SUMMARY OF THE INVENTION  
         [0010]    The stated object is realized in a spray gluing unit according to the present invention, applicable to a product packaging machine, comprising at least one spray gluer equipped with a nozzle having a respective outlet from which an adhesive substance is directed at a wrapping material enveloping the products, also means by which to clean the gluing nozzle, the gluing nozzle and the cleaning means being capable of movement one relative to another for the purpose of cleaning the outlet.  
           [0011]    To advantage, the spray gluer presents a surface surrounding and joined to an end face of the nozzle outlet, and cleaning means comprise means capable of interacting with the end face of the outlet and with the surrounding surface at least during the relative movement of the cleaning means and the nozzle, in such a way as to remove any residues of the adhesive substance. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    The invention will now be described in detail, by way of example, with the aid of the accompanying drawings, in which:  
         [0013]    [0013]FIG. 1 is a schematic illustration of the gluing unit according to the present invention;  
         [0014]    [0014]FIGS. 2, 3,  4  and  5  are respective schematic illustrations showing the gluing unit of FIG. 1 in a succession of operating steps;  
         [0015]    [0015]FIGS. 6, 7,  8 ,  9  and  10  are respective schematic illustrations showing a second embodiment of the gluing unit according to the present invention in a succession of operating steps;  
         [0016]    [0016]FIG. 11 is a schematic illustration showing a further embodiment of the gluing unit according to the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]    Referring to FIG. 1 of the drawings,  1  denotes the gluer of a spray gluing unit  2 .  
         [0018]    In an active gluing position indicated by phantom lines in FIG. 1, the gluer  1  is disposed facing a conveying line (not illustrated) along which sheets of paper material (not illustrated) requiring the application of an adhesive substance are caused to advance through a packaging machine, likewise not illustrated, in a direction denoted A.  
         [0019]    The gluer  1  comprises a cylindrical body  3  of which the longitudinal axis is denoted B, and of which a first end  3   a  is associated rigidly with a rotary member  4  mounted to a support element  5 , this associated rigidly in turn with the packaging machine (not illustrated). The rotary member  4  is driven pivotably about a respective axis C by means of familiar type, not illustrated, in such a way as to rotate the gluer  1  between the aforementioned gluing position, facing the conveying line, and an at-rest position facing a cleaning station  6 .  
         [0020]    The gluer  1  also comprises a nozzle  7 , located at a second end  3   b  of the cylindrical body  3  opposite to the first end  3   a , comprising a relative outlet  8  from which the adhesive substance is projected.  
         [0021]    The nozzle outlet  8  presents an end face  9  that is directed toward the cleaning station  6  whenever the gluer  1  occupies the at-rest position.  
         [0022]    Also forming part of the gluer  1  is a cylindrical cap  10  coupled with and surrounding the nozzle  7 , presenting a flat surface  11  disposed perpendicular to the aforementioned longitudinal axis B, which occupies substantially the same plane as the end face  9  of the nozzle outlet  8  and affords a hole  12  through which the adhesive substance is projected into space from the tip of the nozzle.  
         [0023]    The cleaning station  6  includes a first member  13  capable of movement along a path D substantially perpendicular to the longitudinal axis B of the body  3 , as viewed with the gluer  1  occupying the at-rest position, between a first non-operating position distanced from the gluer  1  and a second operating position of proximity to the gluer  1 .  
         [0024]    The first movable member  13  is furnished at a first end  13   a , directed toward the gluer  1 , with means  14  serving to remove residues of the adhesive substance from the selfsame gluer  1 .  
         [0025]    In the preferred embodiment of FIGS.  1  to  5 , such removal means  14  advantageously comprise a scraper blade  15  of flexible plastic material such as will engage both the end face  9  of the outlet  8  and the flat surface  11  of the cap  10  during the passage of the first movable member  13  along the aforementioned path D.  
         [0026]    Likewise to advantage, the plastic material from which the scraper blade  15  is fashioned will be a non-stick material, for example Arnite (registered trademark), to which the adhesive substance does not cling.  
         [0027]    The scraper blade  15  presents an inside face  15   a  directed toward the first movable member  13  and an outside face  15   b  on the opposite side to the inside face.  
         [0028]    Also mounted to the movable member  13 , alongside the removal means  14 , is a wetting pad  16  designed to engage the nozzle outlet  8  sequentially with the scraper blade  15  to the end of maintaining a given level of moistness at the outlet  8 .  
         [0029]    The wetting pad  16  carried by the first movable member  13  receives a fluid substance, for example silicone oil, supplied by way of a feed duct  17  connected to a device  18  represented schematically as a block in the drawings, by which the fluid is atomized in a stream of gas directed to the pad  16 .  
         [0030]    As discernible from the drawings, the cleaning station  6  also comprises a pan  19  disposed facing the outlet  8  when the gluer  1  occupies the at-rest position and serving thus to catch the adhesive substance discharged when the nozzle is purged.  
         [0031]    The pan  19  is connected to a relative supporting structure  20  associated rigidly with the packaging machine (not illustrated) by means of magnetic elements  21 , in such a way that it can be removed swiftly when filled with the adhesive substance and replaced immediately with an empty pan  19 .  
         [0032]    The means  14  for removing the adhesive substance and the wetting pad  16  together constitute means  30  by which to clean the gluing unit  2 .  
         [0033]    Similarly, the atomizer device  18  and the feed duct  17  carrying the silicone oil, also a temporary storage tank (not illustrated) containing oil of this same type, together constitute feed means  40  by which the oil is supplied to the pad.  
         [0034]    In operation, referring to FIG. 1, the gluer  1  is caused during a non-operating step of the cycle performed by the gluing unit  2  to rotate together with the cylindrical body  3  through the agency of the drive means (not illustrated), in the direction of the arrow denoted F 1 , from the active gluing position indicated by phantom lines to the at-rest position facing the cleaning station  6 .  
         [0035]    The cleaning operation, which commences as soon as the gluer  1  reaches the aforementioned at-rest position, consists in four distinct steps: a first step of removing any residues of the adhesive substance from the flat surface  11  of the cap  10  and from the end face  9  of the outlet  8 , a second step of wetting the nozzle  7  with silicone oil, a third step of removing the silicone oil deposited on the nozzle  7  and on the flat surface  11 , and a fourth step of purging the gluer  1 .  
         [0036]    Departing from the retracted and non-operating position of FIG. 1, the first movable member  13  begins moving along the path D in the direction of the arrow denoted F 2  to effect the first step of the cleaning operation, as illustrated in FIG. 2, in which the scraper blade  15  carried by the first end  13   a  is caused to engage the flat surface  11  of the cap  10  and the end face  9  of the outlet  8  and thus remove any residues of the adhesive substance that may have accumulated on these parts.  
         [0037]    During this same first step, the scraper blade  15  is able to bend, even minimally, in such a way that the outside face  15   b  appears convex and the inside face  15   a  concave, with the concave surface directed toward the first movable member  13 .  
         [0038]    The cap  10  is fashioned from a non-stick plastic material such as will prevent the aforementioned residues of adhesive substance from clinging to the flat surface  11  and thus facilitate their removal.  
         [0039]    Residues of the adhesive substance dislodged in the course of the first removal step by the scraper blade  15  from the flat surface  11  of the cap  10  and the end face  9  of the outlet  8 , are taken up onto the outside face  15   b  of the scraper blade  15  and able to run off freely as the blade is fashioned advantageously from non-stick material.  
         [0040]    With reference to FIG. 3, which illustrates the aforementioned second step of wetting the nozzle  7 , the first movable member  13  advances further along the path D to the point of placing the pad  16  in front of and in contact with the nozzle  7 . During this second step, the wetting pad  16  is kept in the position of contact with the nozzle  7 , occluding the outlet  8 , and dampened with aerated silicone oil received by way of the feed duct  17  from the atomizer device  18 , to the end of maintaining the outlet  8  suitably moist and lubricated.  
         [0041]    With reference to FIG. 4, which illustrates the third step of removing the silicone oil deposited on the nozzle  7  and the flat surface  11  during the second wetting step, the first movable member  13  moves back along the path D in the direction of the arrow denoted F 3 , away from the gluer  1 , to resume the first non-operating position of FIG. 1.  
         [0042]    During this third step, the scraper blade  15  is able to bend in the direction opposite to that of the first step, even minimally, in such a way that the outside face  15   b  appears concave and the inside face  15   a  convex, with the convex surface directed toward the first movable member  13 .  
         [0043]    As the first movable member  13  retracts in the direction of the aforementioned arrow F 3  during the third step, the flat surface  11  of the cap  10  and the end face  9  of the outlet  8  are wiped by the inside face  15   a  of the scraper blade  15 , and there is therefore no risk of them being fouled by the adhesive substance removed previously and picked up on the outside face  15   b  of the blade  15 .  
         [0044]    With reference to FIG. 5, which illustrates the fourth purging step  1 , the first movable member  13  will remain motionless in the first non-operating position while the gluer  1 , positioned with the outlet  8  directly facing the pan  19 , discharges a continuous jet  22  of the adhesive substance in such a way as to simulate and restore normal operating conditions in the gluing unit following the pause.  
         [0045]    [0045]FIG. 6 illustrates an alternative embodiment of the gluing unit according to the invention, wherein the cap  10  presents a smooth surface  23  of curved profile and the cleaning station  6  comprises a second movable member  24  rotatable about an axis E substantially parallel to the axis C of the rotary member  4  and perpendicular to the viewing plane.  
         [0046]    In like manner to the first movable member  13  described previously, the second movable member  24  carries a respective scraper blade  25  and a wetting pad  26  designed to engage the curved surface  23  of the cap  10  when rotated in the direction of the arrow denoted F 4 , departing from the non-operating condition illustrated in FIG. 6, to the end of removing any residues of the adhesive substance from the selfsame surface  23 .  
         [0047]    As discernible from FIGS. 7, 8,  9  and  10  and in like manner to the sequence already described, the cleaning operation consists in four distinct steps: a first step, illustrated in FIG. 7, of removing any residues of the adhesive substance from the curved surface  23  of the cap  10  and from the end face  9  of the outlet  8 ; a second step, illustrated in FIG. 8, of wetting the nozzle  7  with silicone oil; a third step, illustrated in FIG. 9, of removing the silicone oil from the nozzle  7  and the curved surface  23 ; and a fourth step, illustrated in FIG. 10, of purging the gluer  1 .  
         [0048]    It will be observed in particular that during the fourth step illustrated in FIG. 10, the second movable member  24 , illustrated by phantom lines, is retracted by drive means of conventional embodiment (not illustrated) along a direction substantially parallel to the relative axis E of rotation and perpendicular to the viewing plane, in such a way that the selfsame member  24  remains clear of the jet  22  discharged into the pan  19  by the gluer  1  when purging.  
         [0049]    Observing FIGS. 7, 8,  9  and  10 , the various steps in question are implemented by rotating the second movable member  24  about the relative axis E. In particular, the second movable member  24  rotates first in the direction of the arrow denoted F 4  to the point of assuming the position of FIG. 8, in which the wetting pad  26  is brought into alignment with the nozzle  7 , and thereafter in the opposite direction indicated by the arrow denoted F 5 , so as to complete the third step of removing the silicone oil, illustrated in FIG. 9, and ultimately regain the initial angular position of FIG. 6, which is indicated by phantom lines in FIG. 10.  
         [0050]    In the example of FIG. 11, which illustrates a further embodiment of the invention, means  14  by which the adhesive substance is removed from the cap  10  comprise a circular brush  27  mounted to the first movable member  13  and set in rotation by drive means of familiar embodiment (not indicated) about a respective axis G extending substantially perpendicular to the viewing plane.  
         [0051]    For the cleaning operation to be accomplished to best advantage, importantly, the first movable member  13  carrying the rotary brush  27  needs to be operated in such a way that the brush  27  will make no contact with the flat surface  11  when distanced from the gluer  1  after the flat surface  11  has been wetted by the pad  16  and the nozzle  7  lubricated with silicone oil, as there would be a risk of the flat surface  11  being fouled again.  
         [0052]    In another alternative embodiment of the present invention, not illustrated in the drawings, the gluer  1  might comprise a nozzle  7  with the cap  10  embodied integrally, in which the aforementioned surrounding flat surface and the face  9  of the outlet  8 , advantageously, are one and the same.