Abstract:
Packets of cigarettes are conveyed from a packer to a cellophaner by a unit utilizing a first pocket conveyor connected to the infeed of the cellophaner, and a second pocket conveyor by which packets are directed onto the first conveyor at a transfer point; the unit is also equipped with a sensor that will check whether or not each pocket of the second conveyor is occupied by a packet, and a placement mechanism, interlocked to the sensor, of which the function is to fill any empty pockets of the first conveyor with packets recycled from the cellophaner.

Description:
This application claims priority to Italian Patent Application No. BO2004A000494, filed Aug. 3, 2004, which is incorporated by reference herein. 
   BACKGROUND OF THE INVENTION 
   The present invention relates to a unit for conveying products. 
   In particular, the present invention relates to a unit for conveying products to a user machine, and more exactly a unit comprising a first and a second conveyor set in continuous motion. 
   The invention finds application, to advantage, in the art field of conveying systems for packets of cigarettes, to which reference is made explicitly in the specification albeit implying no limitation in scope. 
   In a typical cigarette packaging line, packets turned out by a cigarette packer are directed into a cellophaner, which proceeds to envelop each one in an overwrapping of polypropylene; the packets are supplied to the cellophaner by a first conveyor carrying the main flow from the packer, randomly spaced, and by a second recycle conveyor or hopper, which carries unblemished packets readmitted to the production cycle upstream of the cellophaner. 
   The readmission step is made necessary for one reason more than any other, namely that to operate correctly, the user machine must be supplied with packets in a continuous and ordered succession, whereas in practice it can happen that gaps will appear in the flow of packets proceeding toward the cellophaner, and in consequence empty spaces on the conveyor, attributable to various different causes. 
   Owing to constraints determining the way that the outfeed conveyor of the cigarette packer and the infeed conveyor of the cellophaner are positioned in space, the path followed by the aforementioned first or main conveyor will generally incorporate 90° and 180° bends and changes of level, and it is therefore normal for the conveying path to include curvilinear stretches along which the packets are directed downwards toward the cellophaner. These non-rectilinear stretches of the conveying path can cause damage to packets propelled forward at the high operating speeds of modern cigarette packers. In effect, the packets advance broadside along the rectilinear sections of the path, proceeding in close order with one larger side face resting on the belt of the conveyor, and are caused to strike one against another when passing through the bends and down the gradients of the path. In particular, it will often happen that the corner of one packet rubs against the flank face of the packet in front, generating wear. 
   A further problem connected with random spacing of the packets is that the dynamic by which they are carried along the path cannot be controlled, so that it is not possible to apply additional items to the packets, such as coupons and/or leaflets, before their entry into the cellophaner. 
   Positioned generally alongside the main conveyor, the recycle hopper containing readmissible packets is associated with a push rod designed to eject the lowest packet from the hopper and direct it onto the main conveyor whenever there is a gap in the flow of packets advancing on the selfsame conveyor. 
   More particularly, given that the packets do not advance in a regularly spaced succession, it is not possible with this type of feed system to predict when there are going to be gaps on the conveyor, and the recycle hopper comes into operation only when the cigarette packer is at standstill. Even with the recycle hopper installed and in operation, consequently, there will always be unpredictable gaps in the flow of packets directed along the main conveyor toward the cellophaner, and the resulting empty spaces reduce the efficiency of the machine considerably. 
   Attempts have been made to avoid damage to the packets along the non-rectilinear stretches of the main conveyor, by employing conveyors on which the selfsame packets are fed to the cellophaner in a regularly spaced succession, each one occupying a stable position determined by a relative projection or ridge on the surface on the conveyor. 
   A solution of this type precludes the use of the conventional recycle hopper to readmit unblemished packets as described above, since, at the high operating speeds of the user machine, the cycle time needed for a push rod to transfer a packet from the hopper to the main conveyor would be much longer than the time taken by the empty space to pass across the outlet of the selfsame hopper. 
   Solutions of other types would be notably complex from the constructional standpoint, inasmuch as they would be based on the use of a hopper capable of traversing parallel with the feed direction of the flow of packets and thus allowing the outlet to track the adjacent gap so that a recycled packet can be placed accurately in the required position. 
   The object of the present invention is to provide a conveying unit for products, presenting a first conveyor and a second conveyor feeding respective ordered flows of the products, such as will allow products missing from the first ordered flow to be made up with products from the second ordered flow, even at the high operating speeds of user machines, employing a device of simple and practical design. 
   Adopting a unit in accordance with the invention, in particular, any packets missing from the first ordered flow can be made up as the selfsame flow advances, without its progress being interrupted. 
   SUMMARY OF THE INVENTION 
   The stated object is realized according to the present invention in a unit for conveying products, comprising a first conveyor with pockets feeding a succession of products toward the user machine, a second conveyor with pockets feeding products onto the first conveyor at a transfer point, also sensing means serving to detect the presence of products in the pockets of the second conveyor, and placement means, interlocked to the sensing means, by which products can be directed into the pockets of the first conveyor so as to obtain an unbroken succession of products occupying the pockets of the first conveyor downstream of the transfer point. 

   
     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 preferred embodiment of the unit for conveying products according to the present invention, viewed schematically in a side elevation with certain parts omitted in the interests of clarity; 
       FIG. 2  shows a detail of the unit in  FIG. 1 , viewed schematically in a side elevation and in a different operating situation; 
       FIG. 3  shows a detail of the unit in  FIG. 1 , viewed in perspective from above and with certain parts omitted better to illustrate others; 
       FIGS. 4 and 5  are respective schematic views showing a detail of the unit in  FIGS. 1 and 2 , in two different operating situations; 
       FIGS. 6 and 7  show a detail of the conveying unit according to the present invention, viewed in plan from above with certain parts omitted, and in two different operating situations. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 1 , numeral  1  shows a portion of a cigarette packing line, in its entirety. 
   The line  1  in question comprises a unit  2  by which packets  3  of cigarettes are conveyed to a user machine such as a cellophaner, represented schematically in  FIG. 1  by a block denoted  4 . 
   The packets  3  are turned out by an upstream unit consisting for example in a cigarette packer, shown schematically in  FIG. 1  as a block denoted  5 , and directed along the conveying unit  2  following a feed path denoted P. 
   The conveying unit  2  includes a first conveyor  6 , set in continuous motion, from which packets  3  are directed into the aforementioned user machine  4 , and a second conveyor  7 , likewise set in continuous motion, from which packets  3  are directed onto the first conveyor  6 . In an alternative embodiment of the unit  2 , the conveyors  6  and  7  might be driven intermittently. 
   The advancing packets  3  pass from the second conveyor  7  onto the first conveyor  6  at a transfer point denoted  8 . 
   The first conveyor  6  consists in a belt conveyor of familiar type equipped with ridges  9  combining in pairs to create respective pockets  10 , each one of which accommodates a single packet  3 . 
   The first conveyor  6  is looped around a plurality of pulleys  11  of which at least one (not indicated) is a driving pulley, whilst the remainder are idle pulleys. 
   Only certain of the pulleys  11  are illustrated in the accompanying drawings. 
   The first conveyor  6  comprises a substantially horizontal top transport branch  12  extending along a rectilinear direction D and providing one segment of the feed path P along which the packets  3  are directed toward the cellophaner. 
   Like the first conveyor  6 , the second conveyor  7  consists in a belt conveyor presenting ridges  9  that combine in pairs to establish a succession of pockets  10  each accommodating a single packet  3 . 
   The second conveyor  7  is looped around a plurality of pulleys  13  and rollers  14 . 
   Not all of the pulleys denoted  13  are illustrated in the accompanying drawings, and at least one (not indicated) is power driven whilst the remainder are idle pulleys. 
   The second conveyor  7 , which occupies a position above the first conveyor  6 , comprises a respective transport branch  15  composed of a horizontal upper infeed segment  16  on which the packets  3  emerging from the packer  5  are taken up, also a descending segment denoted  17 , and a horizontal lower outfeed segment  18  facing the top transport branch  12  of the first conveyor  6  in the neighborhood of the transfer point  8 . 
   The aforementioned descending segment  17  includes a substantially vertical rectilinear portion  17   a , and two curvilinear connecting portions  17   b  and  17   c  merged respectively with the horizontal upper and lower segments  16  and  18 . 
   Referring to  FIGS. 1 and 2 , the unit  2  further comprises a third belt conveyor and a fourth belt conveyor, denoted  19  and  20  respectively. 
   As illustrated in  FIG. 2 , the third conveyor  19  is looped around a driving pulley  21  and around a plurality of idle rollers  22  and  23 , the rollers denoted  22  occupying fixed positions, the rollers denoted  23  mounted flexibly to respective spring elements  24 . 
   The third conveyor  19  presents an active top branch  25  running in the direction of the arrow F in  FIG. 2 , and a bottom return branch  26 . 
   Similarly to the third conveyor  19 , the fourth conveyor  20  is looped around a driving pulley  27  and around a plurality of idle rollers  28  and  29 , the rollers denoted  28  occupying fixed positions and the rollers denoted  29  mounted flexibly to respective spring elements  30 . 
   The fourth conveyor  20  presents an active bottom branch  31  running in the direction of the arrow F in  FIG. 2 , and a top return branch  32 . 
   The two active branches  25  and  31  presented respectively by the third and fourth conveyors  19  and  20  are mutually opposed for delimiting a channel through which packs are advanced from the storage magazine to the transfer point. 
   With reference to  FIG. 1 , the unit  2  further comprises a magazine  33  of multiple hopper type design, in which to store packets  3  releasable to the first conveyor  6  in a manner to be described in due course. A fifth belt conveyor  34  substantially of familiar type, not described here in detail, is positioned to coincide with an area  35  at which the packets  3  are released from the magazine  33  and serves to feed the selfsame packets  3  toward the third and fourth conveyors  19  and  20 . 
   Referring to  FIG. 2 , the unit  2  comprises a pair of timing rollers  36  located between the third conveyor  19  and the first conveyor  6 , positioned one on each side of the selfsame first conveyor  6 ; one only of the two rollers  36  is visible in the accompanying drawings. 
   The two rollers  36  are rotatable about mutually parallel axes A 1 , and set in motion by drive means (not indicated) in opposing directions of rotation. 
   As discernible from the detailed illustration of  FIG. 3 , the unit  2  comprises a guide device  37  of which the purpose is to support and allow packets  3  coming from the second conveyor  7  to slide onto the first conveyor  6 , while at the same time allowing packets  3  already on the first conveyor  6  to pass directly through the transfer point  8 . 
   The guide device  37  includes a plurality of pairs of bridging members  38  angled downwardly along the feed path P followed by the packets  3  along the first conveyor  6 . 
   As illustrated to advantage in  FIGS. 6 and 7 , moreover, the two bridging members  38  of each pair are positioned respectively on opposite sides of the feed path P and present respective portions  38   a  converging on the selfsame path P. 
   In addition, the bridging members  38  are flexibly resilient when engaged, in a direction transverse to the rectilinear direction D aforementioned, by the advancing packets  3  carried in the pockets  10  of the first conveyor  6 . 
   Each bridging member  38  is incorporated into a lever element  39  embodied as a rocker and mounted to a relative fulcrum pivot  40 , capable of rocking thus on a respective axis A 2  independently of all the other lever elements  39 . 
   Each lever element  39  comprises a first arm  39   a  and a second arm  39   b  positioned on opposite sides of the pivot  40 . 
   The first arm  39   a  presents a side face  41  placed to engage the packets  3  occupying the pockets  10  of the first conveyor  6 , and a flat face  42  on which the packets  3  directed along the feed path P by the second conveyor  7  are supported and able to slide. 
   The aforementioned converging portion  38   a  is delimited by the side face  41 , and thus forms a part of the first arm  39   a  presented by the lever element  39 . 
   Anchored to the second arm  39   b  of each lever element  39  is a first end  43   a  of a coil spring  43 , of which a second end  43   b  is anchored to a mounting element  44 . 
   As illustrated in  FIG. 3 , the lever elements  39  are mounted sequentially in sets of three, each to a respective plate  45  carried in turn by a vertical bulkhead  46  of the frame (not illustrated) on which the conveying unit  2  is carried. 
   Observing  FIGS. 2 and 3 , the second conveyor  7  will be seen to comprise an element  47 , extending along the descending segment  17 , by means of which to guide and restrain the packets  3  advancing along the conveyor  7 . 
   The guiding and restraining element  47  is offered to the descending segment  17  in such a manner as to keep each of the packets  3  lodged internally of the relative pocket  10 , and terminates at the transfer point  8  in a tongue  48  adjacent to the bridging members  38  of the guidance device  37 . 
   Positioned along the transport branch  15  of the second conveyor  7 , at a given point upstream of the transfer point  8 , is a proximity transducer  49  such as will verify the presence or absence of packets  3  in the respective pockets  10  of the conveyor  7 . 
   The transducer  49  provides the conveying unit  2  with relative sensing means  50  serving to detect the presence of the packets  3 . 
   The guide device  37  functions both as means  51  by which packets  3  advancing in the pockets  10  of the second conveyor  7  are slidably supported, and as means  52  by which packets  3  already advancing in the pockets  10  of the first conveyor  6  are afforded a passage through the transfer point  8 . 
   The timing rollers  36  combine with the third conveyor  19  and the fourth conveyor  20  to provide the conveying unit  2  with placement means  53  by which packets  3  are directed into the pockets  10  of the first conveyor  6 . 
   In addition, the conveying unit  2  will include a computerized master control unit (not illustrated) serving to manage the various operations performed by the unit  2 . 
   In operation, single packets  3  emerging from the packer  5  are directed onto the horizontal upper segment  16  presented by the transport branch  15  of the second conveyor  6 , each one being placed, by substantially familiar methods, in a respective pocket  10  delimited by the aforementioned ridges  9 . 
   Thus, the packets  3  advance along the feed path P and down the descending segment  17  of the transport branch  15 , supported by the guiding and restraining element  47 , arriving ultimately at the point  8  of transfer to the first conveyor  6 . 
   Passing from the second conveyor  7  to the first conveyor  6 , the single packets  3  slide over the flat faces  42  of the lever elements  39  and locate in a respective pocket  10  presented by the top transport branch  12  of the first conveyor  6 . 
   For a number of different reasons such as, for example, the rejection of defective packets  3  emerging from the cigarette packer  5 , a pocket  10  of the second conveyor  7  may happen to contain no packet  3 , in which case the empty space is detected by the aforementioned transducer  49  located along the feed path P, upstream of the transfer point  8 , and a relative signal is sent to the computerized master control unit (not illustrated). 
   The computerized master control unit will pilot the placement means  53  to respond by preparing a recycled packet, denoted  3 ′, in readiness to fill the pocket  10  of the first conveyor  6  that should have been occupied, had the missing packet  3  been transferred as normal from the second conveyor  7  to the first conveyor  6 . 
   For this to occur, more exactly, the forwardmost of the packets  3 ′ advanced by the third and fourth conveyors  19  and  20  is positioned in contact with the cylindrical surfaces of the timing rollers  36 . 
   The timing rollers  36  are set in contrarotation at high speed about their respective axes A 1 , so that when contact is made with a recycled packet  3 ′ fed forward by the third and fourth conveyors  19  and  20 , the packet  3 ′ is accelerated to the point of locating against one ridge  9  of a predetermined pocket  10  presented by the first conveyor  6 . 
   The pocket  10  in question is precisely the one that would have been occupied by the packet  3  missing from the second conveyor  7 . 
   As illustrated in  FIG. 6 , the aforementioned packet  3 ′ is directed forward by a ridge  9  (not illustrated) of the corresponding pocket  10  and advanced along the feed direction D, to the point of engaging the lever elements  39  of the guide device  37 . 
   Referring to  FIGS. 6 and 7 , as the recycled packet  3 ′ makes contact with the side faces  41  of the single lever elements  39 , the lever elements  39  are caused to pivot on their respective fulcrum axes A 2 , spreading substantially in a transverse direction to allow the passage of the packet  3 ′ and then closing again immediately, returned by the action of the springs  43 . 
   As illustrated in  FIGS. 3 ,  6  and  7 , the unit  2  is equipped with a plurality of the aforementioned lever elements  39 , so that the section of the feed path P covered by the guide device  37  can be split between the selfsame levers, or rather between the relative flat faces  42 ; in other words, observing  FIG. 7 , whilst the lever elements  39  farthest downstream along the feed path P remain spread to allow the passage of a recycled packet  3 ′, the elements  39  farthest upstream will already have been returned to the closed position by the action of the springs  43 , in readiness to support another packet  3  advancing on the second conveyor  7 . Self-evidently, in the event that two or more adjacent packets  3  may be missing on the second conveyor  7 , the unit  2  is able to fill the gap by admitting two or more recycled packets  3 ′ in succession. 
   Thus, by replenishing any vacant pockets  10  of the first conveyor  6  with recycled packets  3 ′ fed directly onto the transport branch  12  of this same first conveyor  6 , it becomes possible to maintain an unbroken succession of packets  3  downstream of the transfer point  8 , each occupying a respective pocket  10  of the conveyor  6 . 
   With a conveying unit  2  according to the present invention, advantageously, a first continuously driven conveyor  6  equipped with pockets  10  can be supplied with packets  3 , through the agency of placement means  53 , from a second continuously driven conveyor  7  also equipped with pockets  10 , in such a way as to compensate any gaps presented by the second of the two conveyors. 
   In an alternative embodiment of the invention, not illustrated, packets  3  leaving the packer  5  could be fed by the conveying unit  2  directly to the first conveyor  6 , with the aforementioned transducer  49  providing sensing means  50  located alongside the first conveyor  6  and the placement means  53  operating in conjunction with the second conveyor  7  so as to direct the recycled packets  3 ′ onto this same second conveyor  7 . 
   In other alternative embodiments of the present invention, likewise not illustrated, the coil type return springs  43  of the lever elements  39  might be replaced by other elements equivalent in terms of the art, such as pneumatic or electric actuators (not illustrated). 
   In another alternative embodiment of a conveying unit  2  according to the present invention, again not illustrated, the first and second conveyors  6  and  7  described and illustrated could be driven intermittently.