Abstract:
A label feeder unit associated with a machine for packing tobacco products holds a stack of labels placed in a channel presenting an infeed end, and an outfeed end from which the labels are released to a take-up station, then picked up singly and transferred to a further unit of the machine. The outfeed end of the channel incorporates a transfer mechanism comprising a pair of contrarotating rollers placed on either side of the channel at a distance less than the width of the stack in such a way as to intercept the labels and transfer them to the take-up station, which is movable relative to the outfeed end of the channel under the pressure transmitted to the station by the labels taken up between the rollers. The transfer mechanism forms part of a feedback control loop by which the pressure registering through the labels at the take-up station is kept within prescribed limits.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a label feeder unit and to a method of feeding labels in a packer machine for tobacco products. 
     In particular, the invention finds application in the art field of devices for dispensing revenue stamps, coupons or tamper-evident seals, and of units for picking up and transferring such items to equipment by which they are affixed or applied to packets containing tobacco products. 
     In conventional machines for applying labels to packets containing tobacco products, the labels are fed to a pick-up and transfer unit by which they will be gummed and then affixed to the packets. 
     During the step of feeding the labels to the pick-up and transfer unit, the labels are arranged in one or more ordered stacks, each comprising a plurality of labels placed one on top of another. The labels therefore combine to form a single compact block. 
     Machines of prior art type for applying labels to packets of tobacco products are equipped with arms supporting the stack of labels, and serving also to establish a feed path along which the labels are advanced. The stack is subjected to a pushing force, directed toward the pick-up unit, so that the labels remain compacted together. 
     The pressure applied thus to the stack of labels can be generated by simple force of gravity, in the case of a vertical machine, or by push rods in the case of a horizontal machine; at all events, a force is directed through the stack, impinging ultimately on restraints afforded by the ends of the arms aforementioned and facing the pick-up unit. 
     The function of the restraints is to hold the labels in a predetermined position when taken up from the stack, in such a way as to facilitate the step by which the single labels are picked up. 
     It has been found, during the operation of conventional machines, that the step of picking up the labels can be problematic. 
     In effect, a degree of adhesion is created between the stacked labels, due mainly to the force applied at the top or rear of the stack to keep it compact, which works in opposition to the pick-up action. 
     The extent of the adhesion aforementioned is also difficult to predict, since the force applied to the stack of labels is dependent (especially in vertical machines) on the number of labels remaining in the stack as each successive pick-up is completed. 
     In addition, the force applied to the compacted labels induces an elastic deformation of the stack, in measure proportional to the number of labels making up the stack at any given moment. 
     Consequently, it happens in certain circumstances that no label will be picked up, or that two or more labels are picked up at once. 
     The drawback in question is betrayed particularly by label feeder units in cigarette packers of the latest generation, where labels must be taken from the stack and transferred at rates of up to a thousand per minute. 
     Accordingly, the object of the present invention is to provide a unit and a method for feeding labels in a packer machine for tobacco products, such as will be unaffected by the drawbacks mentioned above. 
     One object of the invention, in particular, is to provide a unit and a method for feeding labels in a packer machine for tobacco products, designed to allow a correct and systematic release of the single labels from the dispensing device to the pick-up and transfer unit. 
     A further object of the invention is to provide a unit and a method for feeding labels in a packer machine for tobacco products, by which labels can be transferred correctly in high numbers per unit of time. 
     SUMMARY OF THE INVENTION 
     The stated objects are realized according to the present invention in a unit for feeding labels in a packer machine for tobacco products, comprising a channel with an infeed end and an outfeed end, accommodating a stack of labels, a take-up station associated operationally with the outfeed end of the channel, from which the labels are taken up singly and transferred to a user machine, and means by which to transfer a succession of labels, operating between the outfeed end of the channel and the take-up station. The take-up station is movable relative to the outfeed end of the channel in response to the pressure exerted on the station by the succession of labels advanced by the transfer means, and the transfer means form part of feedback control means designed to ensure that the pressure exerted by the succession of labels on the take-up station can be kept within prescribed values. 
     The aforementioned objects are realized similarly in a method implemented by means of the unit disclosed, which includes the steps of loading a stack of labels into the unit, transferring the labels from the stack to a take-up station, then picking up the labels from the station and transferring them singly to a further machine unit. The method of the invention also includes the steps of measuring the pressure exerted on the take-up station by the transferred labels, and employing a feedback control loop to set the transfer rate of the labels on the basis of the measurement, in such a way as to maintain the pressure exerted on the take-up station within prescribed values. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described in detail, by way of example, with the aid of the accompanying drawings, in which: 
         FIG. 1  shows a label feeder unit in a packer machine for tobacco products according to the present invention, illustrated in plan with certain parts omitted better to reveal others; 
         FIG. 2  is a perspective view of the unit in  FIG. 1 ; 
         FIG. 3  is a side view of the label feeder unit according to the present invention; 
         FIG. 4  is a sectional view showing a portion of the unit as in  FIG. 3 , illustrated in a first operating position; 
         FIG. 5  is a sectional view showing the portion of  FIG. 4 , illustrated in a second operating position and with certain parts omitted better to reveal others. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the drawings, numeral  1  denotes a label feeder unit, in its entirety, forming part of a packer machine for tobacco products. The single labels are denoted  100  in the drawings. 
     The term ‘label’, in the context of the present invention, can signify a revenue stamp, a coupon, a tamper-evident seal or other such slip typically of paper material, applicable for whatever purpose to packets containing tobacco products. 
     As shown in  FIG. 3 , the unit  1  is associated operationally with pick-up and transfer means  2  by which labels  100  are conveyed singly and in ordered succession to user means denoted  101 , schematized in  FIG. 3  as a rotating drum  3 . 
     The feeder unit  1  comprises means  3  by which to support a plurality of labels  100  placed one on top of another to form a stack  102 . 
     The labels  100  are supplied to the unit  1  through the agency of a conventional mechanism not shown in the drawings, such as will direct a flow of the labels  100  to a first end of the stack  102 . 
     In detail, the support means  3  comprise a plate  4  anchorable to a fixed structure employing means of conventional type (not illustrated), and two guide rails  5  stably associated with the plates  4 . 
     The two guide rails  5  extend parallel one with another and function as respective flat walls  6 . The two walls  6  and the portion of the plate  4  delimited by the guide rails  5  combine to create a channel  7  accommodating the stack  102  of labels  100 , which presents an infeed end  7   a  facing the aforementioned supply mechanism, and an outfeed end  7   b.    
     The width of the channel  7 , that is to say the distance between the two walls  6 , corresponds to one of the dimensions of a single label  100 , so that the stack of labels can be housed in the channel  7  substantially to an exact fit. 
     In an alternative embodiment of the invention (not indicated), the guide rails  5  might be capable of movement toward and away from one another in such a way as to adapt the width of the channel  7  to the size of label  100  in use. 
     The labels  100  are arranged in the channel  7  such that each occupies a respective plane substantially perpendicular to the plate  4 . 
     With the labels  100  subjected to a constant feed and pick-up action, the stack  102  is caused to pass continuously along the channel  7 , and in particular along a direction coinciding with the longitudinal axis A of the stack  102 . 
     To this end, the unit  1  comprises pushing means of conventional embodiment (not illustrated) located at the infeed  7   a  of the channel  7 , such as will apply a pushing force to the stack  102 , directed along the axis A of the selfsame stack  102  toward the outfeed end  7   b  of the channel  7 . 
     Located beyond the outfeed  7   d  of the channel  7  is a station  8  at which the labels  100  are taken up by the pick-up and transfer means  2  in readiness for their release to the user means  101 . 
     As illustrated in the accompanying drawings, the unit  1  further comprises transfer means  9  located between the outfeed  7   b  of the channel  7  and the take-up station  8 , by which labels  100  are received in sequence one at a time from the bottom of the stack  102  and transferred to the take-up station  8 . 
     The take-up station  8  is adjustable for position relative both to the outfeed  7   b  of the channel  7  and to the transfer means  9 , according to the pressure exerted on the selfsame station  8  by the succession of labels  100  in the process of being transferred. 
     More exactly, the greater the number of labels  100  transferred per unit of time from the outfeed end  7   b  of the channel to the take-up station  8 , the greater the pressure exerted by the labels  100  on the selfsame station  8  and consequently the greater the displacement of the station. 
     The unit  1  further comprises feedback control means  10  acting on the transfer means  9  in such a way as to ensure that the pressure exerted by the succession of labels  10  on the take-up station  8  is kept within prescribed values. 
     Thus, advantageously, the pressure that registers through the labels  100  occupying the take-up station remains substantially constant, favoring a correct release of the labels  100  to the pick-up and transfer means  2 . 
     In effect, it has been verified by experiment that the labels  100  will be taken up correctly, one by one, avoiding the release of two or more single labels at a time, when the pressure acting on the labels at the outfeed end of the stack, and therefore at the take-up station  8 , is maintained substantially constant and above a predetermined minimum threshold. 
     In addition, and to advantage, the action of the feedback control means  10  on the transfer means  9  serves also to ensure that the distance between the outfeed end  7   b  of the channel  7  and the take-up station  8  is kept likewise within prescribed values, thereby maximizing the efficiency of the pick-up and transfer means  2 . 
     In practice, control over the distance between the take-up station  8  and the outfeed end  7   b  of the channel  7  is a function, indeed a consequence, of the control maintained over the pressure exerted by the labels  100  on the take-up station  8  given that it is this same pressure, as mentioned previously, that causes the take-up station  8  to move away from or toward the outfeed end  7   b  of the channel  7 . 
     To advantage, therefore, when the pressure exerted on the take-up station  8  is maintained within prescribed values, the distance between this same station  8  and the outfeed end  7   b  of the channel  7  is kept likewise within prescribed values. 
     As discernible from  FIG. 1 , in particular, the transfer means  9  also function as detent means by which the feed motion of the stack  102  is checked at the outfeed end  7   b  of the channel  7 . 
     In this situation, the pressure directed from the stack  102  toward the take-up station  8 , generated by the force of the aforementioned pushing means, or of gravity in the case of a vertical unit  1 , will not actually be transmitted to the take-up station  8 . 
     Accordingly, the stack  102  retains its elasticity, and the pressure exerted on the take-up station  8  is not influenced by the number of labels  100  making up the stack, but dependent only on the number of labels  100  released per unit of time by the transfer means  9  to the take-up station  8 . 
     In a preferred embodiment of the unit, the take-up station  8  comprises at least two abutment members denoted  11 , each incorporating a restraint  12  presented by one end of a rod-like element  13 . 
     The restraints  12  of the two abutment members  11  are mutually opposed and positioned to interact with the opposite edges of a label  103  at the moment of release, in such a way that the label is steadied and presented to the pick-up and transfer means  2 . 
     The abutment members  11  are slidable independently of one another along an axis parallel to the axis A of the stack  102  of labels in response to the pressure exerted by the advancing labels  100  on the restraints  12 . 
     As illustrated in  FIGS. 1 and 2 , in particular, the rod-like elements  13  are slidable in grooves  15  afforded by the guide rails  5  of the channel  7 , their translational motion guided by link rods  15  connecting the rod-like element  13  to the plate  4 . 
     The feedback control means  10  comprise at least one traction element  16  schematized as a spring in  FIGS. 1 and 2 , which indicate two such springs, each operating between an abutment member  11  and a guide rail  5 . 
     In particular, each of the traction elements  16  is connected at one end to one rod-like element  13  and at the opposite end to a portion of the guide rail  5  located upstream of the portion presenting the groove  14  in which the rod-like element  13  is slidable. 
     The traction elements  16  exert a predetermined force on the abutment members  11 , generated in a direction opposite to the force exerted by the labels  100  on the restraints  12 , in such a way that motion will be induced in the abutment members  11  when the pushing force on the restraints  12  is greater or less than the force exerted by the traction elements  16 . 
     The movement of the abutment members  11  is also piloted by position sensors  17 , illustrated in  FIGS. 1 and 2 , which form part of the feedback control means  10 . 
     In the example of the accompanying drawings, the position sensors  17  are located internally of the guide rails  5  so as to measure the displacement of the rod-like elements  13 ; in practice, however, any other type of sensor might be used equally well to measure the displacement of the abutment members  11 . 
     Whatever the type adopted, the position sensors  17  will be connected to a master control unit (not illustrated) which, in possession of data indicating the force exerted on the abutment members  11  by the traction elements  16 , and of data indicating the displacement of the abutment members  11 , is able to compute the pressure exerted at any given moment on the restraints  12  by the labels  100  passing through the transfer means  9 . 
     Thus, the master control unit acts in feedback mode on the transfer means  9 , raising or lowering the rate at which the labels  100  are released to the take-up station  8  according to the pressure acting on the restraints  12  at any given moment. 
     Importantly, to reiterate, the position of the restraints  12  will also be monitored continuously and kept within prescribed values. 
     In the example illustrated, the transfer means  9  include a first pair of rollers  18  mounted rotatably to the plate  4 , each turning on a respective axis X 1  and X 2  normal to the plate  4  and thus orthogonal to the axis A of the stack  102  of labels. 
     The rollers  18  are placed at the outfeed end  7   b  of the channel  7  on opposite sides of the stack  102  and set in contrarotation by drive means, not shown in the drawings, so as to engage and transfer the labels from the stack  102  to the take-up station  8 . 
     With this end in view, to ensure the labels  100  are taken up cleanly, the revolving surfaces of the rollers  18  present a knurled profile  19 . The ridges of the knurled profile  19  extend along directions parallel to the axes X 1  and X 2  of rotation of the rollers  18 , thus lying parallel to the respective edges of the labels  100  with which they engage. 
     The rollers  18  are set apart one from another by a distance less than the width of the stack  102 , so as to intercept and advance the labels  100 . 
     It will be seen therefore that the rollers  18  also provide the aforementioned detent means checking the feed motion of the stack  102 . 
     In effect, the rollers  18  (when not in rotation, self-evidently) intercept the stack  102  and prevent the labels  100  from advancing, irrespective of the pressure exerted on the rollers  18  by the selfsame labels. 
     Accordingly, the pressure exerted via the stacked labels  100  on the rollers  18  is not transmitted to the abutment members  11  of the take-up station  8 , bringing the advantages mentioned previously. 
     The point at which the stack  102  of labels is intercepted by the rollers  18  coincides with a halt line B extending parallel to and upstream of the line joining the centers of the rollers  18 , as illustrated in  FIGS. 1 and 4 . 
     Conversely, the restraints  12  coincide with a line of mutual alignment extending parallel to and below the line joining the centers of the rollers  18 . 
     To advantage, with the abutment members  11  capable of movement independently of one another, as in the preferred embodiment described thus far, it becomes possible to identify and correct any transfer of the labels  100  which, though made at the correct rate, occurs with the labels not perfectly at right angles to the axis A of the stack  102 . 
     In this situation, the pressures impinging on the two abutment members  11  would be dissimilar one to another, indicating that the labels  100  entering the take-up station  8  are skew relative to the correct transfer plane. 
     The master control unit corrects the misalignment by increasing or reducing the speed at which one of the two rollers  18  rotates, for a limited period, following which the labels  100  will realign and the pressure exerted on both abutment members  11  is equalized. 
     In an alternative embodiment, not illustrated, a further pair of rollers could be provided, flanking the rollers  18  of the first pair, and two further abutment members operating independently of one another, flanking the two abutment members  11  already described. 
     The four abutment members would interact with the four corners, or corner edges, of the labels. 
     With this arrangement, similarly, it will also be possible to correct a misalignment of the advancing labels  100  relative to a plane perpendicular to the plane described previously. 
     In other words, adopting a solution of this type, it will be possible to verify and ensure that the labels  100  advance exactly orthogonal to the axis A of the stack  102 , or at all events aligned on any given plane. 
     The rollers  18  of the pair illustrated in the drawings combine to create a path converging along the transfer direction of the labels  100  toward the pick-up station  8 , in such a way that the labels are deformed during the transfer step. 
     To advantage, the deformation of the transferred labels  100  is induced by bending each one relative to the plane occupied at the outfeed end  7   b , thereby generating a concave face directed back toward the stack  102 . Each deformed label  100  thus presents a bowed central portion of which the convex face is directed toward the pick-up and transfer means  2 , as illustrated in the bottom part of  FIGS. 1 and 2 . 
     Accordingly, the restraints  12  are angled in such a way as to lie tangential to the bowed portion of the endmost label  103 . 
     The aforementioned pick-up and transfer means  2  comprise a rotary conveyor  105  shown in  FIG. 3 , rotatable about an axis denoted X 3 , by which the single labels  103  are received from the take-up station  8  and conveyed to the aforementioned user means  101 . 
     The pick-up and transfer means  2  comprise a plurality of gripping and retaining carriers  106  arranged around a peripheral surface of the rotary conveyor  105  and defining a feed path along which the successive endmost labels  103  of the stack are transported, retained by suction during the rotation of the conveyor  105 . 
     As illustrated in detail in  FIGS. 4 and 5 , each gripping and retaining carrier  106  comprises a pair of suction cups  107  disposed side by side, thereby combining with the other carriers to form two rows of cups around the periphery. 
     The suction cups  107  of each pair can be offered simultaneously to the endmost single label  103  of the stack  102 , which is thereupon taken up by vacuum force. To this end, each of the suction cups  107  is connected by way of a duct  108  to vacuum means of conventional type, not illustrated in the drawings. 
     Each carrier  106  also comprises motion-inducing means  109  that serve to guide the suction cups  107  between a plurality of pick-up positions in which the two cup rims occupy respective mutually inclined gripping planes, as illustrated in  FIG. 4 , and a release position in which the rims occupy a common plane, as illustrated in  FIG. 5 . 
     The motion-inducing means  109  present a pivotable mechanism  110  supporting the suction cups  107 , of which the rocking motion defines the aforementioned pick-up position and release position of the suction cups  107 . 
     The pivotable mechanism  110  incorporates a first arm  110   a  and a second arm  110   b , each hinged to the peripheral surface of the rotary conveyor  105  about a respective pivot axis X 4  and carrying a respective suction cup  107 . The two arms  110   a  and  110   b  are interconnected by way of a translatable hinge  110   c  occupying an intermediate position between the two arms  110   a  and  110   b , so that the selfsame arms can be contrarotated through an identical angle about the respective pivot axes X 4 , and the suction cups  107  made to assume the pick-up and release positions. 
     The motion-inducing means  109  further comprise a push-pull rod  111  linked to the two arms  110   a  and  110   b , which acts on the hinge  110   c  in such a way as to rotate the arms  110   a  and  110   b  and thus cause the suction cups  107  to shift between the two operating positions. 
     The push-pull rod  111  is preferably reciprocated, capable of movement between a position retracted partly into the rotary conveyor  105 , with the two arms  110   a  and  110   b  rotated in such a way as to bring the two suction cups  107  closer together, and an extended position with the two arms  110   a  and  110   b  rotated in such a manner as to spread the suction cups  107  farther apart. The rod  111  might be actuated electrically or pneumatically, by way of example. 
     The suction cups  107  are secured to respective clevis mounts  112 , each attached pivotably to the respective arm  110   a  and  110   b  and rotatable thus about a relative axis X 5 . Anchored pivotably in this way, the suction cups  107  are able to assume the pick-up and release positions described above. 
     The position in which the rims of the two suction cups  107  occupy mutually inclined planes, or rather the pick-up position, coincides with the extended position of the push-pull rod  111  in which the two arms  110   a  and  110   b  are rotated and the associated suction cups  107  are spread apart, effectively to their maximum distance one from another. In this situation, the endmost label  103  of the stack  102  can be taken up smoothly and efficiently by the suction cups  107 , which are configured in such a way as to adapt to the bowed surface of the label  103 , as discernible in  FIG. 4 . 
     The release position of the suction cups  107  is assumed when the push-pull rod  111  occupies the retracted position, causing the arms  110   a  and  110   b  to rotate in such a way that the suction cups  107  are drawn together, effectively to their minimum distance one from another. 
     The objects stated at the outset are realized in accordance with the invention. 
     In effect, utilizing a feedback loop to monitor the pressure exerted by the labels on the take-up station and to control the rate at which the labels of the stack are released to this same station, the pressure exerted on the station can be maintained substantially constant, as also can the position of the station itself. 
     Thus, the best conditions possible are created for a swift and smooth transfer of the single labels.