Patent Publication Number: US-8979013-B2

Title: Rapid tearing device of a strip in a rewinding machine

Description:
The present invention relates to a rapid tearing device of a strip in a rewinding machine. 
     In the field of machines suitable for the formation of rolls or “logs” of paper destined for the preparation of toilet paper, blotting paper and/or similar products, rewinding machines are envisaged, which wind the continuous paper coming from a large paper roll, onto cores. For the production of paper rolls, in fact, there is a feeding of a continuous strip of paper material along a pre-defined route. It should be noted that the continuous strip, after starting its unwinding in a certain course, encounters a punching group whereby it is provided with transversal perforation lines to facilitate breakage and consequently the tearing of short sections of paper having a predetermined length. 
     The continuous strip therefore contains a series of transversal perforated weakening lines, parallel to each other and spaced at regular intervals. 
     The continuous strip thus treated, is introduced into the rewinding machine, where it is wound onto a cardboard supporting core, tubular in form, externally having a pre-determined portion of glue along a generatrix of the core. 
     The rotation of the core by means of a group of winding rolls causes the winding of the continuous strip until the respective roll or “log” of wrapping paper has been formed. As already mentioned, at the beginning of the winding, a piece of the strip is joined to the core by means of glue positioned on the latter. 
     At the end of the winding of a predetermined amount of continuous paper strip, the tail of the log must be separated thus contemporaneously creating the head of a new log to be formed. 
     The separation operation of the continuous strip is effected, for example, by means of tearing which causes the breakage of the continuous strip along one of the perforated lines produced on the paper and mentioned above. 
     This separation can be effected in various ways and using various devices. The tearing action of the continuous strip can be effected, for example, by varying the rotation rate of the winding rolls so as to create a section of strip sufficient for causing its breakage along a respective transversal perforated line. 
     Alternatively, in EP 1618057, the tearing of the continuous strip is effected by the high-pressure blowing of a fluid against the perforated line in order to cause its breakage. 
     Comb- or buffer-elements are also envisaged, which intervene on the strip near a perforation line and block the paper on the upper winding cylinder in order to effect the above-mentioned separation. 
     Even if the above systems and methods for the separation of the continuous strip of paper material allow the desired breakage of the paper to be effected along the transversal perforated line selected, these methods are either particularly complex or they generate folds on the paper and problems downstream during rewinding. 
     The general objective of the present invention is to solve the above-mentioned drawbacks of the known art in a simple, economical and particularly functional way. 
     Another objective of the invention is to provide device for the rapid tearing of a strip in a rewinding machine which does not cause folds on the paper which is being wound onto the core. 
     Yet another objective of the invention is to provide a device for the rapid tearing of a strip in a rewinding machine which causes the least possible waste of paper being wound before the paper adheres to the glue carried by the core. 
     A further objective of the present invention is to provide a device for the rapid tearing of a strip in a rewinding machine which does not use buffers or, in any case, does not exploit the combined action with the upper winding roll. 
     In view of the above objectives, according to the present invention, a device has been conceived for the rapid tearing of a strip in a rewinding machine having the characteristics indicated in the enclosed claims. 
    
    
     
       The structural and functional characteristics of the present invention and its advantages with respect to the known art will appear more evident from the following description referring to the enclosed drawings, which show, inter alia, a scheme of an embodiment of a rapid tearing device of a strip in a rewinding machine produced according to the same invention. In the drawings: 
         FIG. 1  shows a schematic and synthetic view of the main parts of a rewinding machine which comprises a rapid tearing device of a strip, according to the present invention; 
         FIG. 2  is an enlarged detail of what is shown in  FIG. 1 , in a subsequent operative phase; 
         FIGS. 3 to 5  show, in similar views of  FIG. 1 , subsequent operative phases of the rapid tearing device of a strip in a rewinding machine according to the invention. 
     
    
    
     With reference to  FIG. 1 , this substantially illustrates the core of a rewinding machine in which a rapid tearing device of a continuous strip of paper according to the invention, is positioned. 
     The rewinding machine at which a continuous strip of paper  11  arrives, such as, for example, toilet paper, blotting paper and/or other types of paper materials, essentially comprises an area in which the rolls or logs  12  of paper are prepared. 
     A conveyor  13  equipped with pushers  14  for the advancing of cores  15 , made of cardboard for example, is positioned upstream of this area for the formation of the log. 
     The end of the conveyor  13  faces a channel  16  defined by a series of cradles  17  integral with the structure of the rewinder. 
     An upper winding roll  18  is positioned above the channel  16 , or cradles  17 , whereas a lower winding roll  19  is situated almost at the end of the cradles  17 . A third oscillating roll  20  is positioned above the lower winding roll  19 , cooperating with it and with the upper winding roll and acting as a press with a variation in the dimension of the log  12  being formed between the three mentioned rolls  18 ,  19  and  20 . 
     The cores  15 , carried by the conveyor  13  by means of the pushers  14 , are previously provided with sections of glue  21 , situated in correspondence with the area where the finger on a watch indicates nine. According to the present invention, a device according to the present invention is situated in a similar arrangement of the rewinder. 
     A pair of arms  22  are in fact envisaged, only one of which is shown, situated in opposite positions with respect to the ends of the rolls. The two arms  22  carry a cross-piece  23 , for example tubular, on which a blade  24  is positioned, arranged transversally with respect to the advancing of the paper, which has the same size as the width of the mentioned rolls  18 ,  19  and  20  (size of the bench). 
     The blade  24  can be moved by means of actuators, between a stand-by position and an engagement position on a core  15 , when this core  15  is discharged by the conveyor  13  and introduced into the channel  16  so as to block, between the core  15  and blade  24 , the paper  11  which is being unwound and passing through this point. 
     The arms  22  oscillate around central pins  25  and two spring cylinders  27  are connected to these at a first end, in further pins  26 , the spring cylinders  27  being hinged in turn at the other end of the arms by means of pins  28  to the structure of the rewinder. 
     The cylinders  27  act as elastic means and operate so that the arms are pulled back according to the arrow  29  of  FIG. 1 , i.e. moved away from the upper roll  18  so that the blade  24  does not interfere with one of the cores  15  pushed forwards by the pushers  14  of the conveyor  13 , to be sent inside the channel  16 . Furthermore, they normally keep the feelers  30  in contact with a cam wheel  31 . 
     The device of the invention also envisages that the arms  22  oscillate by means of a cam wheel—movable feeler coupling in synchronism with a discharge introducer  34  of a core  15  from the conveyor  13  towards the channel  16 . 
     More specifically, the cam wheel—movable feeler coupling envisages that a feeler  30  be positioned at the end of the oscillating arms  22 , opposite to that where the blade  24  is situated. The feeler  30  is kept in contact with an outer surface of a cam wheel  31  positioned on the same axis  33  as a toothed wheel  32  which activates the movement of the conveyor  13 . In this way the above-mentioned actuating means of the blade  24  are produced. 
     Furthermore, the cam wheel  31 , or toothed wheel  32 , carries at least one introducer  34  which discharges the core  15  carried by the pushers  14  of the conveyor  13  and introduces or inserts it at the inlet of channel  16 . 
     A cam portion  35  radially protruding outwardly from the cam wheel  31 , acts on the feeler  30  of the two arms  22  when a core  15  is introduced by the introducer  34  at the inlet of the channel  16 . 
     In this way, the arms  22  oscillate clockwise in  FIG. 3 , according to the arrow  36 , overcoming the force of the spring cylinders  27  and the core  15  is pressed between the blade  24 , the pusher  14  and the cradles  17  ( FIG. 3 ). 
     In this way, the paper  11  is also pressed between the walls in contact with each other, and stops. The paper  11  is torn in the transversal perforated line  37 , closest to the core  15 , due to the strong deceleration it undergoes as a result of the pressure of the core  15  on the blade  24  which has stopped in the maximum proximity position towards the conveyor  13 . In this way, the log  12 , in formation, is freed and can be removed from its grip between the rolls  18 ,  19  and  20 . In addition, the head of the paper is created, which will be wound around the core  15  which is thus introduced into the channel  16 . 
       FIG. 4  shows how, by continuing the introduction of the core  15  into the channel  16  by means of the pusher  34 , the lengths of glue  21 , i.e. the glue, are put in contact with the paper  11  just before the head of the paper separated by the device of the invention. 
       FIG. 5  shows a subsequent step, wherein the core  15 , with the respective glued paper  11 , is made to roll into the channel  16  by the action of the upper roll  18 , to be positioned between the rolls  18 ,  19  and  20  of the rewinder to produce another log  12 . 
     In the meantime, in an immediately subsequent step to that of the tearing shown in  FIG. 3 , the continuous rotation of the toothed wheel  32 , or cam wheel  31 , causes disengagement between the cam portion  35  of the cam wheel  31  and feeler  30  of the two arms  22 , with backward oscillation of the same arms brought back by the cylinders  27  ( FIG. 4 ). 
     The originality of this device consists in the fact that, as in previous devices, there is no specific device (a buffer, for example) which slows down the paper and tears it in the point closest to the perforation, acting on the upper winding roll. It is, in fact, the same core  15  which, in collaboration with the blade  24  situated near the paper  11 , grips the paper and tears it. 
     The operative phases previously illustrated can be summarized by making reference to the figures. 
       FIG. 1  shows the rewinding machine and the device of the invention appears in stand-by, whereby the introducer  34  does not act and the blade  24  is raised, far from the cores  15  and from the paper  11 . 
     In  FIG. 2 , the core  15  is in an exchange phase, the introducer  34  is adjacent to it and the cam portion  35  of the cam wheel  31  is about to come into contact with the feeler  30  to make the arms  22  oscillate. 
     In  FIG. 3 , the introducer  34  is in movement and acts on the core  15 , the cam portion  25  moves the arms  22  and causes the blade  24  to descend and block the paper  11  which is torn in the closest point to the perforation after the core  15 . 
     In  FIG. 4 , the core  15  enters the cradles  17  and is rotated by the upper roll  18 . In this way, the glue  21  is put, with the core, in contact with the paper  11  so as to form a new winding. 
     Finally,  FIG. 5  illustrates more clearly how the log  12  formed between the rolls leaves the same and the wound core  15  is brought to the winding phase. It is also evident that the introducer  34  returns to the low disengagement position and another core  15  is moved forwards. 
     It can therefore be seen that the device of the invention is extremely simple and the capturing strip of the paper is extremely short and reduced to the minimum. 
     The objective mentioned in the preamble of the description has therefore been achieved. 
     The forms of the structure for the production of a device according to the invention, as also the materials and assembly modes, can obviously differ from those shown for purely illustrative and non-limiting purposes in the drawings. 
     The protection scope of the present invention is therefore delimited by the enclosed claims.