Abstract:
A method and machine for wrapping products in respective sheets of heat-seal material, whereby the products are fed successively along a first wrapping path to form, about each product, a tubular wrapping having two opposite open ends, and are then fed successively along a second wrapping path to close and seal the respective open ends; the products being fed with a first spacing along the first wrapping path, and with a second spacing, smaller than the first spacing, along the second wrapping path.

Description:
The present invention relates to a method of wrapping products. 
     The present invention is particularly advantageous for use on machines for cellophaning packets of cigarettes, to which the following description refers purely by way of example. 
     BACKGROUND OF THE INVENTION 
     On known machines for cellophaning packets of cigarettes, the packets of cigarettes are fed by a first conveyor at a given speed along a first wrapping path to form respective tubular wrappings, each comprising two opposite open ends about the packet, and are fed by a second conveyor at the same speed along a second wrapping path to close the ends of each tubular wrapping. 
     As it normally takes longer to close the ends than to form the tubular wrapping, and as the packets are fed at the same given speed along both paths, the second path must necessarily be longer than the first, which normally means a considerable increase in the size and cost of the second conveyor, on account of numerous technical features normally preventing changes to other construction characteristics of the machine. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a method of wrapping products, designed to eliminate the aforementioned drawback, and which at the same time is cheap and easy to implement. 
     According to the present invention, there is provided a method of wrapping products in respective sheets of wrapping material, the method comprising the steps of feeding said products successively along a first wrapping path to form, about each product, a respective tubular wrapping having two opposite open ends; and feeding said products successively along a second wrapping path to close and stabilize the respective said open ends; the method being characterized in that said products are fed along said first wrapping path in spaced relation from one another at intervals forming a first spacing between sucessive products along said first wrapping path, and said products are fed along said second wrapping path in spaced relation from one another at intervals forming a second spacing, smaller than the first spacing. 
     The present invention also relates to a machine for wrapping products. 
     According to the present invention, there is provided a machine for wrapping products in respective sheets of wrapping material, the machine comprising a first conveyor for feeding said products successively along a first wrapping path; first wrapping means located along said first wrapping path to form, about each product, a respective tubular wrapping having two opposite open ends; a second conveyor for feeding said products successively along a second wrapping path; and second wrapping means located along said second wrapping path to close and stabilize the respective said open ends; the machine being characterized in that said first and said second conveyor provide for feeding said products with a first and a second spacing respectively, the second spacing being smaller than the first spacing. 
    
    
     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 schematic, partially sectioned side view of a preferred embodiment of the machine according to the present invention; 
     FIG. 2 shows a larger-scale view of a first detail in FIG. 1; 
     FIGS.  3 ( a ) and ( b ) each shows a schematic, larger-scale view of a second detail in FIG. 1 in different operating positions; 
     FIG. 4 shows a larger-scale view in perspective of a third detail in FIG. 1; 
     FIGS.  5 ( a ) and ( b ) each shows a larger-scale view in perspective of a fourth detail in FIG.  1 . in two different operating positions. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Number  1  in FIG. 1 indicates as a whole a continuous cellophaning machine for overwrapping packets  2  of cigarettes in respective sheets  3  of heat-seal wrapping material. 
     Packets  2  are fed by a known supply device  5  to an input conveyor  4  of machine  1  at an input station S 1 . 
     Conveyor  4  feeds packets  2  from input station S 1  to a transfer station S 2  with a spacing St1 actually equal to approximately 180 mm; and, at station S 2 , each packet  2  is transferred to a respective conveyor head  6  fitted to a wrapping conveyor  7  to feed packets  2  successively along a wrapping path P 1 . 
     The spacing and the traveling speed of packets  2  along path P 1  substantially equal St1 and V1 respectively. However, due to certain movements performed, in use, by head  6  with respect to conveyor  7  and described in detail later on, the spacing and traveling speed of packets  2  along path P 1  vary temporarily about values St1 and V1 respectively. 
     As shown more clearly in FIG. 4, each packet  2  is elongated and substantially parallelepiped, and comprises two opposite longitudinal end bases  8  and a lateral surface  9  perpendicular to bases  8 ; and each conveyor head  6  engages bases  8  of a respective packet  2 . 
     Along path P 1 , each packet  2  is paired with a respective sheet  3  of wrapping material, which is subsequently folded to form about packet  2  a tubular wrapping  10 , which has two opposite open ends  11 , and at least partially encloses respective conveyor head  6 . 
     Path P 1  terminates at a transfer station S 3  where each packet  2  is transferred to a wrapping conveyor  12  which feeds packets  2 , enclosed in respective tubular wrappings  10 , successively along a wrapping path P 2  and with a spacing St2 smaller than spacing St1 and actually equal to 120 mm. 
     Along path P 2 , the open ends  11  of each tubular wrapping  10  are closed and stabilized by sealing to complete the overwrapping of packets  2  in respective sheets  3 . 
     Path P 2  terminates at a transfer station S 4  where the overwrapped packets  2  are transferred to a known output section (not shown) which feeds packets  2  along a drying path P 3  and then to a known output (not shown) of machine  1 . 
     Packets  2  are therefore fed along conveyor  4  and, substantially, along path P 1  with spacing St1, and are fed along path P 2  with a spacing St2 smaller than St1. To maintain a constant flow of packets  2  (i.e. the number of packets  2  processed per unit time) along machine  1 , the traveling speed V1 of packets  2  along conveyor  4  and path P 1  must be greater than the traveling speed V2 of packets  2  along path P 2 . In particular, to maintain a constant flow, the ratio between spacings St1 and St2, which is actually 1.5, must equal the ratio between speeds V1 and V2. 
     Input conveyor  4  comprises a belt  13  looped about two end pulleys  14  and having projections  15  equally spaced with spacing St1 and for engaging respective packets  2 . One of the two pulleys  14  is mounted idly to rotate about a fixed axis  16  perpendicular to the FIG. 1 plane, while the other pulley  14  is powered to rotate continuously about a further fixed axis  16  also perpendicular to the FIG. 1 plane. 
     Conveyor  7  comprises a powered wheel  17 , which is mounted to rotate continuously about a fixed central axis  18  parallel to axes  16 , and which supports a number of conveyor heads  6  equally spaced about axis  18 . 
     As shown more clearly in FIG. 4, each conveyor head  6  comprises a pair of opposed gripping pads  19 , each of which engages a respective base  8  of a packet  2  and is fitted to a respective rocker arm  20  connected to wheel  17  by a respective arm  21 , which is fitted at one end—together with arm  21  of the opposite pad  19 —to a shaft  22  connected in rotary manner to wheel  17  and oscillated, with respect to wheel  17  and about a respective axis  23  parallel to axis  18 , by a known cam control device (not shown). 
     Each rocker arm  20  is hinged to respective arm  21 , at the end opposite the end fitted to shaft  22 , by means of a hollow shaft  24  fitted idly to arm  21  to rotate, with respect to arm  21 , about a respective axis  25  parallel to axis  18 , and to slide axially, with respect to arm  21 , along axis  25 . 
     Each rocker arm  20  comprises an arm  26  fitted on the end with respective pad  19 ; and an arm  27 , which, as shown in FIG. 2, is connected at the end to a control device  28  comprising a sleeve  29  fitted idly to shaft  22  of arm  21  of the head  6  immediately upstream in the rotation direction (anticlockwise in FIG. 1) of wheel  17 . Sleeve  29  is also slid axially along said shaft  22  by a known cam control device (not shown). Device  28  also comprises a lever  30  integral with and extending radially from sleeve  29 , and the free end of which is hinged at  31  to the free end of arm  27  of rocker arm  20 . 
     Consequently, as each sleeve  29  slides axially along respective shaft  22 , respective pad  19  is moved to and from a closed position (FIG. 5 a ) contacting respective base  8  of respective packet  2 ; and, as a shaft  22  and respective arm  21  oscillate about respective axis  23 , respective rocker arm  20  oscillates about respective axis  25 , given the constant distance between respective hinge  31  and axis  23  of the arm  21  immediately upstream in the rotation direction of wheel  17 . 
     Each pad  19  comprises a cup-shaped body  32  projecting from pad  19  towards the opposite pad  19 , and the bottom surface of which is defined by respective pad  19 . Cup-shaped body  32  is axially and laterally open, and is defined by relatively thin metal plates  33  fitted to a lateral surface of respective pad  19  to contact, in use, lateral surface  9  of a respective packet  2 . 
     As shown more clearly in FIG. 5, each pad  19  comprises a respective retaining member  34  for retaining sheet  3  of wrapping material in a given fixed position with respect to pad  19 . Retaining member  34  comprises a lever  35  hinged to respective rocker arm  20  and oscillated about an axis  36  crosswise to respective axis  25  by a known cam control device (not shown). Lever  35  carries an end pad  37 , which is movable with lever  35  from a rest position (FIG. 5 a ) to a work position (FIG. 5 b ) in which end pad  37  laterally contacts respective gripping pad  19  to retain sheet  3  of wrapping material against gripping pad  19 . 
     As shown more clearly in FIG. 2, machine  1  comprises a belt conveyor  38  located at transfer station S 2 , parallel to and facing conveyor  4 , and defining, together with conveyor  4 , a channel  39  for guiding packets  2  during transfer from conveyor  4  to respective conveyor heads  6  on conveyor  7 . To better perform said guide function, conveyor  38  comprises a projection  40  for engaging a respective packet  2  together with respective projection  15  of conveyor  4 . 
     Machine  1  comprises a supply station  41  for supplying sheets  3  of wrapping material, and which is located along an initial portion of path P 1  and in turn comprises a known supply unit  42  for feeding a sheet  3  of wrapping material in a direction perpendicular to and through path P 1 . Supply unit  42  receives a continuous strip  43  of heat-seal wrapping material, which is unwound off a reel (not shown) and is cut by a pair of cutting rollers  44  into portions, each defining a sheet  3  of wrapping material. 
     Machine  1  comprises a passive wrapping fixture  45  (i.e. a fixture having no moving parts) located in a fixed position along path P 1 , immediately downstream from supply station  41 , and which is defined by a folding channel  46  for folding a sheet  3  of wrapping material into a U about a respective packet  2  fed by a respective head  6  along path P 1 . Channel  46  is defined by a pair of facing walls  47  located on opposite sides of path P 1  and having respective folding brushes  48 . 
     Once folded into a U about respective packet  2 , each sheet  3  of wrapping material has two wings  49  and  50  projecting transversely and rearwards from packet  2 . 
     Machine  1  comprises an active wrapping fixture  51  (i.e. a fixture having at least one moving part) located along path P 1 , immediately downstream from folding channel  46 , to fold wing  49  through 90° onto packet  2 . 
     Active wrapping fixture  51  comprises a wheel  52  powered to rotate continuously about a fixed axis  53  parallel to axis  18 ; and a number of wrapping tools  54 , each of which provides for folding wing  49  through 90° onto packet  2 , and is connected to the free end of a respective arm  55 . Each arm  55  is hinged to wheel  52  at the end opposite said free end, and is oscillated, with a given eccentricity and about an axis  56  parallel to axis  53 , by a known cam control device (not shown). 
     Wrapping tool  54  comprises a generating device  57  for generating an electrostatic field, which acts on wing  49  to polarize and enable wing  49 , once folded, to adhere at least temporarily to packet  2 . 
     Machine  1  also comprises a passive wrapping fixture  58  located in a fixed position along path P 1 , downstream from folding channel  46 , to fold wing  50  of sheet  3  of wrapping material through 90° onto respective packet  2  and partly onto the previously folded wing  49  to define respective tubular wrapping  10 . 
     Wrapping fixture  58  comprises a body  59  having a surface  60 , which defines a folding surface along which packet  2  is substantially rolled, by rotating respective head  6  about respective axis  25 , to fold wing  50  through 90°. 
     The bottom wall  47  of folding channel  46  extends beyond the top wall  47  and up to the beginning of surface  60 , with which it blends to keep the bottom portion of the U-folded sheet  3  in contact with respective packet  2 . 
     Machine  1  comprises a number of passive wrapping fixtures  61 , each of which is carried in a fixed position by wheel  17 , is associated with a respective conveyor head  6 , and is defined by a sealing device  62  for stabilizing a tubular wrapping  10  by on-edge sealing the superimposed portions of wings  49  and  50  folded onto respective packet  2 . 
     As shown in FIG. 1, wrapping conveyor  12  comprises a conveyor belt  63  moving continuously along path P 2  and having projections  64  spaced with spacing St2 to engage and feed forward packets  2 . Path P 2  comprises a straight initial portion P 4 ; a downstream straight portion P 5  connected to portion P 4  by a curved portion; and a circular end portion P 6  extending about a fixed axis  65  parallel to axis  18 . 
     Along circular portion P 6 , belt  63  extends about a wheel  66  powered to rotate continuously about axis  65 ; and, at the opposite ends of portion P 4 , belt  63  extends about a pair of idle transmission rollers  67  rotating about respective axes  68  parallel to axis  65 . 
     Conveyor  12  comprises a channel  69  extending along portion P 4  and defined on one side by a fixed surface  70  and on the other side by conveyor belt  63 . 
     Machine  1  comprises a folding device  71  located along straight portion P 5  of path P 2  to fold the open ends  11  of each tubular wrapping  10  onto respective packet  2  as packet  2  travels along portion P 5  of path P 2 . Folding device  71  comprises a known first movable folding element (not shown) for making a first fold of open ends  11 ; and two known fixed helical folding elements  72  (only one shown in FIG. 1) located on either side of path P 2  to engage respective open ends  11  of each tubular wrapping  10 . 
     Machine  1  also comprises a transfer unit  73  located between conveyors  7  and  12  at transfer station S 3 , and which in turn comprises a belt  74  looped about a pair of end pulleys (not shown) to guide packets  2  to an input  75  of channel  69 . Belt  74  comprises projections  76  spaced with spacing St1 to engage and feed forward packets  2  as packets  2  are transferred from conveyor  7  to conveyor  12 . 
     Wheel  66  comprises a number of pairs of sealing heads  77  (only a first head in each pair shown in FIG.  1 ), which are equally spaced about axis  65  and provide for stabilizing, by sealing, ends  11  of each tubular wrapping  10  folded by folding device  71 . The heads  77  in each pair are positioned facing each other to simultaneously engage respective opposite ends  11  of a respective tubular wrapping  10 . 
     Operation of cellophaning machine  1  will now be described with reference to one packet  2 , and as of the instant in which packet  2  is fed by supply device  5  onto conveyor  4  at station S 1  and with spacing St1. 
     As shown in FIG. 1, conveyor  4  engages packet  2  by lateral surface  9 , leaving bases  8  free, and feeds packet  2  continuously to station S 2  where packet  2  is transferred to a respective head  6  which, rotating about axes  18 ,  23  and  25 , feeds packet  2  along path P 1 . 
     As shown more clearly in FIG. 2, at station S 2 , respective control device  28  first positions pads  19  of head  6  facing and detached from bases  8  of packet  2  (FIG.  4 ), and then moves pads  19  into said closed position (FIG. 5 a ) in which respective cup-shaped body  32  of each pad  19  engages a respective longitudinal end of packet  2 . 
     The above passage of pads  19  into the closed position is completed as packet  2  travels along guide channel  39 , at the end of which, packet  2  leaves conveyor  4  and is conveyed solely by respective head  6  along path P 1  and through supply station  41 . At station  41 , supply unit  42  has already positioned a respective sheet  3  of wrapping material, still attached to strip  43 , perpendicular to path P 1 , so that, as packet  2  is fed along path P 1 , a portion  78 —frontwards in the traveling direction—of lateral surface  9  of packet  2  engages a corresponding portion of sheet  3 . 
     As packet  2  engages sheet  3 , said known cam control device (not shown) moves levers  35  of respective head  6  into said work position (FIG. 5 b ) in which each respective end pad  37  laterally contacts respective gripping pad  19  to retain sheet  3  of wrapping material in a given fixed position against gripping pad  19 . Sheet  3  is detached from strip  43  by cutting rollers  44  as soon as sheet  3  is clamped by pads  37 . 
     At this point, as head  6  continues along path P 1 , packet  2  is fed into folding channel  46 , which folds sheet  3  into a U about packet  2 , about respective plates  33 , and partly about respective pads  19 . Folding sheet  3  into a U about plates  33  poses no problem on account of the relatively small thickness of plates  33  and the flexibility of packet  2  and sheet  3 . 
     In an alternative embodiment not shown, folding channel  46  comprises a generating device for generating an electrostatic field, which acts on sheet  3  to polarize and enable sheet  3  to adhere at least temporarily to packet  2 . 
     At the end of channel  46 , sheet  3  is folded into a U about packet  2  with wings  49  and  50  projecting crosswise and rearwards from packet  2 . As packet  2  continues along path P 1 , the top wing  49  is folded through 90° onto packet  2 , and in particular onto a surface  79 —rearwards in the traveling direction—of lateral surface  9  of packet  2 , by a respective wrapping tool  54 , which is caused to gradually engage wing  49  by the combination of wheel  52  rotating about axis  53 , and respective arm  55  oscillating about axis  56 . 
     In the course of the above folding operation, wing  49  is polarized by an electrostatic field, generated by generating device  57  fitted to tool  54 , to adhere, once folded, at least temporarily to packet  2 . 
     As shown in FIGS. 2 and 3, once wing  49  is folded, packet  2  is substantially rolled along folding surface  60  to fold the bottom wing  50  of sheet  3  of wrapping material through 90° onto surface  79  of packet  2  and partly onto the previously folded wing  49  to form tubular wrapping  10 . Packet  2  is rolled along surface  60  by rotating respective head  6  about respective axis  25 ; which rotation is effected by said known cam control device (not shown) swinging respective arm  21  about respective axis  23 , and provides for moving packet  2  from a substantially tangential to a substantially radial position with respect to axis  18 . 
     As shown more clearly in FIG. 3, on leaving surface  60 , surface  79 , on which wings  49  and  50  have been overlapped, is engaged substantially seamlessly by a work surface  80  of a respective sealing device  62  carried on wheel  17  and associated with respective conveyor head  6 . That is, on coming into contact with respective packet  2 , surface  80  is so located as to form a substantially seamless extension of surface  60 , thus preventing sheet  3 , and in particular the newly folded wing  50 , from springing back to its original configuration. 
     Surface  79  remains contacting sealing device  62  along a portion of path P 1  extending more than 90° about axis  18 , from the output end of folding surface  60  up to transfer station S 3 , and which is sufficient to seal the superimposed portions of wings  49  and  50  and so stabilize tubular wrapping  10 . 
     Before reaching station S 3 , tubular wrapping  10  is released by retaining member  34 , the pads  37  of which are restored to the rest position; and, at transfer station S 3 , packet  2  is restored to a substantially tangential position with respect to axis  18  by rotating respective head  6  about respective axis  25 , which rotation is achieved by said known cam control device (not shown) swinging respective arm  21  about respective axis  23 . 
     At station S 3 , packet  2  is engaged simultaneously by conveyor head  6  and by belt  74  of transfer unit  73 , which assists in guiding packet  2  into channel  69  where packet  2  is engaged by belt  63  and respective projections  64 . 
     On entering channel  69 , packet  2  is engaged by belt  63 , and in particular by projections  64  of belt  63 , and is released by conveyor head  6 , the two pads  19  of which are moved by control device  28  into an open position in which respective cup-shaped bodies  32  are separated by such a distance as not to interfere with packet  2  or respective tubular wrapping  10 . 
     Since packets  2  are fed by conveyor  7  along path P 1  at speed V1 and with spacing St1, and are fed by conveyor  12  along path P 2  at speed V2 and with spacing St2, which are respectively slower and smaller than speed V1 and spacing St1, packets  2  undergo a change in speed at station S 3 , and in particular are slowed down during transfer from head  6  of conveyor  7  to conveyor  12 . In one embodiment, the above change in speed is effected gradually by counter-rotating head  6  about respective axis  23  to temporarily reduce the speed of packet  2  with respect the speed V1 normally imposed by the rotation of wheel  17 . 
     The continuous movement of belt  63  feeds packet  2  along path P 2  and in particular through channel  69  to straight portion P 5 , along which the two opposite open ends  11  of tubular wrapping  10  are engaged by fixed helical folding elements  72  of folding device  71  and are folded onto bases  8  of packet  2 . 
     At the end of straight portion P 5 , the two bases  8  of packet  2 , onto which ends  11  of tubular wrapping  10  have been folded, are engaged simultaneously by respective sealing heads  77  in a respective pair of heads  77  on wheel  66  to stabilize, by sealing, ends  11 . 
     Bases  8  remain in contact with respective sealing heads  77  along a portion of path P 2  extending more than 90° about axis  65 , from the output end of folding device  71  up to transfer station S 4 , and which is sufficient to seal ends  11  and so complete the overwrapping of packet  2  in sheet  3 . 
     Path P 2  terminates at transfer station S 4  where the overwrapped packet  2  is transferred in known manner to said known output section (not shown), which feeds packet  2  along a circular drying path P 3  extending about an axis  81  parallel to axis  65 , and then to said known output (not shown) of machine  1 . 
     In an alternative embodiment not shown, machine  1  comprises an application station located along conveyor  4  and having an application device for applying a label and/or coupon to each packet  2 . 
     In a further embodiment not shown, folding surface  60  is provided with a respective generating device for generating an electrostatic field, which acts on wing  50  to polarize and enable wing  50 , once folded, to adhere at least temporarily, to packet  2 . 
     Machine  1  is therefore relatively straightforward and cheap to produce by comprising only three wrapping tools—two of which passive—which are shared by all of packets  2 ; and by wrapping wheel  17  comprising a small number of moving parts (conveyor heads  6 ) and only supporting passive wrapping fixtures (sealing devices  62 ). 
     Moreover, machine  1  comprises two main sections defined respectively by wrapping conveyors  7  and  12 , and in each of which packets  2  are conveyed at a respective speed and with a respective spacing. More specifically, conveyor  7  feeds packets  2  along path P 1  at speed V1 and with spacing St1, while conveyor  12  feeds packets  2  along path P 2  at speed V2 and with spacing St2. 
     The above characteristic enables each section to operate with the spacing and/or at the speed best suited for the specific job performed by the section, and therefore provides for reducing cost and size for a given performance of machine  1 . That is, along path P 1 , the wider spacing provides for better arranging heads  6  about axis  18 , and the faster traveling speed of heads  6  for rapidly removing the U-folded sheet  3  from station  41  and so preventing wings  49  and  50  of sheet  3  from interfering with the next sheet  3 . Along path P 2 , on the other hand, the narrower spacing and slower traveling speed enable the use of a relatively small-diameter wheel  66  to reduce the overall size of machine  1  within acceptable limits.