Abstract:
A method of forming groups of cigarettes on a packing machine, whereby a conveyor feeds a succession of pockets in steps past a number of group-forming stations, where the pockets receive respective groups of cigarettes fed axially to the relative pockets by means of independent pushers, which are operated in a normal cyclic operating sequence to move selectively through respective group-forming stations; and whereby the formation of a gap along the conveyor, caused by non-supply of a faulty group to a relative pocket, is prevented by replacing the normal cyclic operating sequence with a different cyclic sequence capable of ensuring all the pockets are filled as of the fully operative group-forming stations only.

Description:
The present invention relates to a method of forming groups of cigarettes on a packing machine. 
   More specifically, the present invention relates to a method of forming groups of cigarettes on a packing machine of the type comprising a conveyor moving in a constant sequence of steps along a loading path, and having a number of pockets spaced along the conveyor with a spacing equal to one of said steps, each pocket receiving a respective group of cigarettes; a hopper having n outlets, each for feeding a succession of groups of cigarettes to a respective group-forming station located along the loading path and receiving one respective group at a time, the stations being divided into k first groups (where k varies from one to n) spaced apart by a distance equal to at least two said steps, and the stations in each first group being spaced along the loading path with a spacing equal to one of said steps; and n independent pushers divided into k second groups, each pusher being movable through a respective station to transfer a respective group of cigarettes to a respective pocket. 
   BACKGROUND OF THE INVENTION 
   In packing machines of the type described above, the conveyor pockets are filled, as they travel along the loading path, by operating the pushers in a succession of cycles. At each cycle, all the pushers are operated once in an operating sequence in which the time lapse between operation of two consecutive pushers equals the time taken for the conveyor to advance a number of steps, which may even be zero, and which depends on the pair of pushers considered and may vary from one pair to another. 
   Though widely used for forming groups of cigarettes on packing machines, the above method has several drawbacks, mainly due to any faulty groups, i.e. incomplete groups or groups containing one or more faulty cigarettes, being rejected from the respective pockets downstream from the group-forming station. 
   As a result of the vacancy produced along the conveyor by rejection of a faulty group, the packing materials relative to the missing group must also be rejected, thus possibly resulting in jamming of the packing machine. To eliminate this drawback, complex, high-cost control systems have been proposed to detect a vacancy travelling along the packing machine, and to prevent supply of the relative packing materials accordingly. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a method of forming groups of cigarettes, which can be employed on a packing machine of the type described above, and which prevents the formation of vacancies along the conveyor and packing machine. 
   According to the present invention, there is provided, on a packing machine of the type described above, a method of forming groups of cigarettes, as claimed in the attached claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which: 
       FIG. 1  shows a view in perspective, with parts removed for clarity, of a unit for forming groups of cigarettes and implementing the method according to the present invention; 
       FIG. 2  shows a larger-scale front view of the  FIG. 1  unit; 
       FIG. 3  shows a cigarette group forming sequence on the  FIG. 1  unit in a normal operating condition; 
       FIGS. 4 and 5  are similar to  FIG. 3 , and show respective cigarette group forming sequences on the  FIG. 1  unit in respective further operating conditions. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Number  1  in  FIG. 1  indicates as a whole a unit for forming groups  2  ( FIG. 2 ) of cigarettes  3 . Unit  1  defines the input portion of a cigarette packing machine  4 , and comprises a belt conveyor  5  having a number of pockets  6  spaced with a spacing  7  along the periphery of conveyor  5 , and each for housing a respective group  2 . Conveyor  5  comprises a conveying branch  8  travelling, in a constant sequence S 1  of steps, each equal to spacing  7  and hereinafter referred to as step  7 , in a substantially horizontal direction  9  and along a loading path  10 , along which groups  2  are loaded into respective pockets  6 , to feed groups  2  to a packing line (not shown) of packing machine  4 . 
   As shown in  FIGS. 1 and 2 , unit  1  also comprises a hopper  11 , a bottom end portion of which is defined by four downward-tapering outlets  12 , each divided by a number of substantially vertical partitions  13  into a number of channels  14 , each for receiving a respective column of cigarettes  3  moving by force of gravity crosswise to their longitudinal axes. Each channel  14  is fitted, at a top inlet portion, with a sensor  15  connected to a central control unit  16  and for detecting hollow or missing cigarettes inside channel  14 . 
   Outlets  12  come out inside respective group-forming stations  17  arranged in two groups  18  spaced apart by a distance equal to twice spacing  7 , while stations  17  in each group  18  are spaced apart with a spacing equal to spacing  7 . 
   As shown more clearly in  FIG. 1 , each group-forming station  17  comprises a substantially parallelepiped-shaped box  19  positioned with one end facing conveying branch  8 , and divided longitudinally into a number of compartments  20 , each of which is aligned with the outlet of a corresponding channel  14 , and has a respective longitudinal axis crosswise to travelling direction  9 . 
   Each box  19  catches cigarettes  3  falling down relative channels  14  to form a respective group  2  inside compartments  20 . 
   As shown in  FIG. 1 , unit  1  also comprises four independent pushers  21  divided equally into two groups  22  and each aligned with a respective station  17 . Each pusher  21  comprises a comb  23 , which is defined by a number of teeth  24 , each aligned with a respective compartment  20  of relative box  19 , and is movable, by a respective known linear actuator (not shown) and in a direction crosswise to travelling direction  9 , between a withdrawn rest position, in which comb  23  is located outside respective station  17  and on the opposite side of station  17  to conveying branch  8 , and a forward work position, in which comb  23  extends through respective station  17  to feed cigarettes  3  in relative box  19  to a respective pocket  6  arrested in front of station  17 . 
   Operation of unit  1  will now be described relative to a normal operating condition, in which all four outlets  12  are operating normally. 
   In the normal operating condition, to feed respective groups  2  into all the pockets  6  travelling along loading path  10  and past stations  17  in a constant sequence S 1  of steps  7 , pushers  21  are selectively operated reciprocatingly, as of the withdrawn position, in a succession of cycles, in each of which, pushers  21  are all operated once in an operating sequence S 2 , in which the time lapse between operation of two consecutive pushers  21  equals the time taken for pockets  6  to advance a number of steps  7 , which may even be zero, and which depends on the pair of pushers  21  considered and may vary from one pair to another. 
   By way of example, sequence S 2  of a particular operating cycle of pushers  21  will be described with reference to  FIG. 3 . In  FIG. 3 , each two rows of rectangles represent the change in the position of pockets  6  following a step  7  of conveyor  5 ; pushers  21  are indicated A, B, C, D, as of the first pusher  21  on the right in  FIG. 1 ; the hatched rectangles indicate the full pockets  6 ; and the bold rectangles indicate the pockets  6  filled at the end of step  7  considered. 
   As shown in  FIG. 3 , at the start of a cycle, four consecutive empty pockets  6  are positioned along the portion of loading path  10  extending between pushers A and C. During the stop of conveyor  5  (top row), pushers A and B are operated simultaneously to feed respective groups  2  into respective pockets  6 . Once the respective groups  2  are transferred, pushers A and B withdraw into the withdrawn rest position, thus disengaging respective boxes  19  to allow further cigarettes  3  to drop down into respective compartments  20  to form another respective group  2 . 
   Following the next step  7  (second row from the top in  FIG. 3 ), the two empty pockets  6  downstream from pushers A and B are arrested at pushers C and D to receive respective groups  2  by simultaneously operating pushers C and D. The next three steps  7 , during which pushers A, B, C, D are not operated, conclude the cycle, and move the full pockets  6  downstream from pusher C (fifth row from the top in  FIG. 3 ) to return to the start configuration. 
   The succession of cycles of respective operating sequences S 2  may therefore be represented schematically as follows:
 
[AB-CD - - - ] [AB-CD - - - ] [AB-CD - - - ] [  1)
 
where each dash “-” indicates a step  7 , and each dash between two square brackets is a sequence S 2 .
 
   It should be pointed out that the same result would be obtained performing a succession of cycles of different sequences S 2 , such as:
 
[A-C-B-D-] [A-C-B-D-] [A-C-B-D-] [  2)
 
or
 
[AC - - - BD-] [AC - - - BD-] [AC - - - BD-] [  3)
 
   During operation of packing machine  4 , a sensor  15  may detect, along relative channel  14 , a faulty cigarette and/or a gap caused, for example, by clogging of the inlet of channel  14  or by an improperly positioned cigarette  3  inside channel  14 . Either of the above events results in the formation, at relative station  17 , of a faulty group; in which case, central control unit  16  prevents the faulty group from being fed to relative pocket  6  by somehow disabling relative station  17 , and replaces sequence S 2  with a sequence S 3 , which depends on the location, along loading path  10 , of the disabled station  17 , and ensures all the pockets  6  are filled as of the fully operational stations  17  only. 
   In connection with the above, it should be pointed out that there are various ways of disabling a station  17 , and the method selected by central control unit  16  normally depends on the type of event detected. For example, if a faulty cigarette is detected inside a channel  14 , the relative faulty group is normally formed at relative station  17  and then rejected, in known manner not shown, as it is being expelled from station  17  and before it reaches relative pocket  6 . Alternatively, if a gap is detected along a channel  14 , pusher  21  moving through the relative station  17  is locked inside station  17 , once the last complete group  2  is expelled, thus closing off relative outlet  12 , which is only reactivated following intervention by the operator and when it is again able to form complete groups  2 . 
   Sequence S 3  is continued for as long as a station  17  remains inactive. 
     FIGS. 4 and 5  show respective successions of S 2  and S 3  sequence cycles, in the event stations  17  associated with pusher A ( FIG. 4 ) and pusher C ( FIG. 5 ) are disabled. The same symbols are used in  FIGS. 4 and 5  as in  FIG. 3 , with the addition of a dash line above each rectangle indicating a pocket  6  arrested in front of a disabled station  17 . 
   In the first case, a cycle S 3  may be illustrated schematically as follows:
 
[B-CD - - ]  4)
 
and in the second case:
 
[AB - - D-]  5)
 
   In connection with the above, it should be pointed out that, though the above takes into consideration only one disabled station  17 , sequences S 3  may also be used to ensure all the pockets  6  of conveyor  5  are filled in the event of two simultaneously disabled stations  17 . In this case, however, the output speed of packing machine  4  would most likely drop to such an extent as to make stoppage of packing machine  4  and a return to normal operating conditions inevitable. 
   The method according to the present invention does not only apply to unit  1 , but also to units similar to unit  1  and comprising a different number of stations  17 , i.e. units in which stations  17  are other than four in number and divided into other than two groups  18 . 
   In fact, for any n number of stations  17  of two or more, and for any k number of groups  18  of one or more, sequences S 2  ensuring all the conveyor pockets  6  are filled can always be found; and, similarly, sequences S 3  can always be found to ensure the same result in the event of simultaneous disabling of a number of stations  17  ranging from one to n−1.