Abstract:
A variable-capacity store for objects, wherein an endless conveyor defines a conveying branch, for conveying a mass of objects, and a return branch, which respectively form a first and a second spiral of given lengths, each of which coils about a respective fixed first drum and a respective second drum movable to and from the relative first drum; and wherein the second drums are located on the same side with respect to the relative first drums, and are connected to each other by a transmission powered by a single reversible motor to equally and oppositely adjust the distances between the second drums and the relative first drums.

Description:
The present invention relates to a variable-capacity store for objects. 
     More specifically, the present invention relates to a variable-capacity store for objects defined, for example, by elongated elements, and of the type comprising an input station and an output station located in series along a feed path of the elongated elements; an endless conveyor comprising a conveying branch, for feeding said elongated elements along said path, and a return branch, which respectively form a first and a second spiral of given lengths about respective pairs of guide drums; and adjusting means for adjusting said lengths in complementary manner; said pairs of drums each comprising a fixed first drum, and a second drum movable to and from the relative first drum; and said second drums being located on the same side with respect to the relative first drums. 
     The present invention may be used to advantage for storing cigarettes, to which the following description refers purely by way of example. 
     BACKGROUND OF THE INVENTION 
     For storing cigarettes, a store of the type defined above, and as described for example in EP 0738478, is interposed between a cigarette manufacturing machine and a packing machine to compensate for any difference between the number of cigarettes produced and the number of cigarettes packed, by lengthening or shortening the first or conveying spiral, and by shortening or lengthening the second or return spiral in complementary manner. 
     To move one of the two movable drums away from the relative fixed drum and move the other movable drum towards the relative fixed drum in complementary manner, known stores of the above type normally employ two independent reversible motors controlled by a single central control unit sensitive to any difference between the number of cigarettes produced and the number packed. 
     In known stores of the above type, the two motors, which must be operated simultaneously and in relation to each other, may give rise to both functional and mechanical problems, and in any case involve relatively high production and maintenance costs. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a store of the above type, designed to eliminate the aforementioned drawbacks. 
     According to the present invention, there is provided a variable-capacity store for objects, the store comprising an input station and an output station located in series along a feed path of the objects; an endless conveyor comprising a conveying branch, for feeding said objects along said path, and a return branch, which respectively form a first and a second spiral of given lengths about respective pairs of guide drums; and adjusting means for adjusting said lengths in complementary manner; said pairs of drums each comprising a fixed first drum, and a second drum movable to and from the relative first drum; said second drums being located on the same side with respect to the relative first drums; and the store being characterized in that said adjusting means comprise a transmission connecting said second drums and for moving the second drums equally and oppositely with respect to the relative first drums; and a reversible motor for powering said transmission. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A number of non-limiting embodiments 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 first preferred embodiment of the store according to the present invention; 
     FIG. 2 shows a larger-scale view in perspective of a detail in FIG. 1; 
     FIGS. 3 and 4 show two schematic plan views, with parts removed for clarity, of a second and, respectively, third preferred embodiment of the store according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Number  1  in FIG. 1 indicates as a whole a variable-capacity store for objects defined, for example, by elongated elements  2 , in particular for cigarettes, and comprising, for elements  2 , an input station  3  and an output station  4  located in series along a feed path P of elements  2 . More specifically, store  1  provides for storing a number of elements  2  varying as required with a given range, and for feeding elements  2  to station  4  in the same order in which they are fed, in use, into store  1  at station  3 . 
     From an output conveyor  5  forming part of a manufacturing machine (not shown) and located at station  3 , store  1  receives a number of elements  2  arranged in bulk in a continuous stream  6 , and feeds elements  2  to an input conveyor  7  forming part of a packing machine (not shown) and located at station  4 . 
     Store  1  also comprises an endless conveyor  8 , in turn comprising a conveying branch  9  extending between an input pulley  10  at station  3  and an output pulley  11  at station  4  to convey elements  2  from station  3  to station  4 , and a return branch  12  extending between an input pulley  13  at station  4  and an output pulley  14  at station  3 . 
     Store  1  also comprises an adjusting assembly  15  for adjusting a length L 1  of conveying branch  9  and a length L 2  of return branch  12  in complementary manner to adjust the storage capacity of store  1 , and which comprises two transmission assemblies  16  and  17 . Assembly  16  is associated with conveying branch  9 , and comprises two transmission drums  18  and  19  located between pulleys  10  and  11 ; assembly  17  is associated with return branch  12 , and comprises two transmission drums  20  and  21 ; drum  20  is closer to pulley  13 , and receives return branch  12  via two transmission pulleys  22  and  23 ; and drum  21  is closer to pulley  14 , and feeds return branch  12  to pulley  14  via two transmission pulleys  24  and  25 . 
     Conveyor  8  is a belt conveyor, which forms a first spiral  26  of a given pitch P 1  about drums  18  and  19  of transmission assembly  16 , and a second spiral  27  of a given pitch P 2 —in this case, equal to P 1 —about drums  20  and  21  of transmission assembly  17 . 
     Pulleys  10  and  14  are located at input station  3  and mounted for rotation about respective perpendicular axes  10   a  and  14   a , of which axis  10   a  is parallel to an axis  28  of a transmission pulley  29  of conveyor  5 . Pulleys  10  and  29  are bridged at the top by a supporting plate  30  for supporting elements  2  entering store  1 , and have respective encoders  10   e  and  29   e  for measuring their angular operating speed. Pulleys  11  and  13  are located at output station  4  and mounted for rotation about respective perpendicular axes  11   a  and  13   a , of which axis  11   a  is parallel to both axis  10   a  and an axis  31  of a transmission pulley  32  of conveyor  7 . Pulleys  11  and  32  are bridged at the top by a supporting plate  33  for supporting elements  2  leaving store  1 , and are powered in known manner so as to have the same surface speeds in use. More specifically, pulley  11  provides for activating conveyor  8 . 
     As shown in FIG. 2 (which relates to drum  19 , which has the same structure as the other drums  18 ,  20 ,  21 ), each drum  18 - 21  comprises a respective substantially vertical shaft  34 ; and a number of respective rims  35 , each of which is fitted idly to respective shaft  34  and, together with another rim  35  fitted idly to the other shaft  34  in the same transmission assembly  16 ,  17 , supports a relative coil of relative spiral  26 ,  27 . 
     Transmission assembly  16  comprises a support  36 , in turn comprising a substantially horizontal guide  37  extending between two blocks  38  and  39 ; block  38  supports shaft  34  of drum  18  in fixed manner; while shaft  34  of drum  19  is carried by a slide  40  mounted to run along guide  37 . Similarly, transmission assembly  17  comprises a support  41  located alongside support  36 , and in turn comprising a substantially horizontal guide  42  extending parallel to guide  37  between two blocks  43  and  44 ; block  44  faces block  38  and supports shaft  34  of drum  21  in fixed manner; while shaft  34  of drum  20  is carried by a slide  45  mounted to run along guide  42 . 
     Adjusting assembly  15  also comprises an actuating device  46  associated with drums  18 - 21  and for moving drums  19  and  20  in opposite directions along respective guides  37  and  42  to adjust lengths L 1  and L 2  in complementary manner and therefore the storage capacity of store  1 . Actuating device  46  comprises a transmission  47 , in turn comprising two pulleys  48  and  49 . Pulley  48  is fitted to a shaft  50  parallel to shafts  34 , and which in turn is fitted in rotary manner to a cross member  51  connecting blocks  39  and  43 , and defines the output shaft of a reversible motor  52  for powering transmission  47 ; and pulley  49  is fitted in rotary manner to a shaft  53  parallel to shaft  50  and fitted in fixed manner to a cross member  54  connecting blocks  38  and  44 . A belt  55 , forming part of transmission  47 , is looped about pulleys  48  and  49 , and comprises two branches  56  and  57  parallel to and alongside respective guides  37  and  42 , and connected to respective slides  40  and  45  by an arm  58  and an arm  59  respectively. 
     In a variation of the present invention, pulleys  48  and  49  may be replaced by toothed wheels also indicated  48  and  49 , and about which is looped, instead of belt  55 , a chain also indicated  55 . 
     Adjusting assembly  15  also comprises a known central control unit  60  connected to motor  52  and for controlling rotation of pulley  48  so as to move drums  19  and  20  by the same distance but in opposite directions along relative guides  37  and  42 . Central control unit  60  is also connected to a comparing circuit  61  for receiving a known signal from each encoder  10   e  e  29   e , and for supplying central control unit  60  with an error signal proportional to the difference between the angular speeds of pulleys  10  and  29  to regulate said movements of drums  19  and  20 . 
     In the FIG. 3 variation, actuating device  46  in FIG. 1 is replaced by an actuating device  62 , in which vertical shaft  50  of motor  52  is connected to a transmission  63  comprising a pinion  64  fitted to shaft  50  and located centrally between guides  37  and  42 ; and two racks  65  and  66 , which are parallel to guides  37  and  42 , are connected to and located on opposite sides of pinion  64 , and are integral with arm  58  and arm  59  respectively. 
     Like actuating device  46 , each rotation of pinion  64  of actuating device  62  corresponds to equal and opposite movements of racks  65  and  66 , and therefore of drums  19  and  20 . 
     In the FIG. 4 variation, actuating device  46  in FIG. 1 is replaced by an actuating device  67 , in which vertical shaft  50  of motor  52  is connected to a transmission  68  defined by a rocker arm fitted to shaft  50  and comprising two arms  69  and  70  of equal length and having, close to their free ends, respective axial slots  71  and  72  engaged in transversely sliding manner by shaft  34  of drum  19  and shaft  34  of drum  20  respectively. 
     In actual use, elements  2  are fed continuously by conveyor  5  over plate  30  to an input portion of conveying branch  9 , and are fed by conveying branch  9  to an output portion of conveying branch  9  located at output station  4 , where elements  2  are fed over plate  33  onto conveyor  7  in the same order in which they arelfed into store  1 . 
     In normal operating conditions, the number of elements  2  fed by conveyor  5  to input station  3  equals the number of elements  2  absorbed by conveyor  7  at output station  4 , and said output portion of conveying branch  9  has the same linear speed as conveyor  5 . Comparing circuit  61  therefore supplies central control unit  60  with a zero error signal, so that motor  52  remains idle, and therefore the distances between drums  19 ,  20  and respective drums  18 ,  21  remain unchanged. 
     When the number of elements  2  fed to input station  3  is greater than the number of elements  2  absorbed at output station  4 , comparing circuit  61  sends an error signal to central control unit  60 , which activates motor  52 , and therefore transmission  47 ,  63 ,  68 , so as to move drum  19  away from drum  18 , and move drum  20  towards drum  21  by a distance depending on the difference between the number of incoming and outgoing elements. Moving drum  19  away from drum  18  increases the storage capacity of store  1 , but requires that conveying branch  9  wound about drums  18  and  19  be lengthened accordingly; the amount of conveyor  8  required to compensate which is provided by moving drum  20  towards drum  21 . 
     Conversely, when the number of elements  2  fed to input station  3  is less than the number of elements  2  absorbed at output station  4 , comparing circuit  61  sends an error signal to central control unit  60 , which activates motor  52 , and therefore transmission  47 ,  63 ,  68 , so as to move drum  19  towards drum  18 , and move drum  20  away from drum  21  by a distance depending on the difference between the number of incoming and outgoing elements. Moving drum  19  towards drum  18  reduces the storage capacity of store  1 , but requires that conveying branch  9  wound about drums  18  and  19  be shortened accordingly, so the surplus amount of conveyor  8  is absorbed by moving drum  20  away from drum  21 .