Abstract:
A device for wrapping packets of cigarettes has a conveyor for feeding the packets successively along a path; and a number of heating heads, each of which is brought into contact with a respective packet and accompanies the packet from a contact station to a withdrawal station along part of the path; on reaching the withdrawal station, the heating heads are withdrawn, crosswise to the path, from the respective packets, and are conveyed, parallel to the path, from the withdrawal station to the contact station.

Description:
The present invention relates to a method and device for wrapping articles. 
     The present invention may be used to advantage for packing cigarettes, to which the following description refers purely by way of example. 
     More specifically, the present invention relates to a device for wrapping tobacco products, and which comprises a folding unit for folding a sheet of wrapping material about a respective article to form a wrapping having two superimposed portions; and a first conveyor for feeding the wrapping in a first direction along a first path. The device also comprises a heating head for joining, by transferring heat to, the two said portions; and a second conveyor for feeding the heating head in the first direction, in phase and in contact with the wrapping and from a contact station to a withdrawal station, along a second path parallel to at least one portion of the first path. 
     BACKGROUND OF THE INVENTION 
     Known devices of the above type, such as the device described, for example, in Patent Application WO 0249918 A1, have the drawbacks of being relatively complex, expensive, and bulky, and requiring extremely precise maintenance involving considerable downtime. 
     Other known devices for wrapping articles comprise a wrapping wheel having a number of peripheral seats, each of which, at each operating cycle, transfers a respective group of cigarettes and a respective sheet of wrapping material from an input station to an output station along a work branch of a substantially circular path, and returns to the input station along a return branch of the substantially circular path. 
     Devices of this sort comprise embodiments of a first type, in which a respective heating head is associated with each seat; and embodiments of a second type, in which a number of heating heads are located in substantially fixed positions along the work branch, as described, for example, in Patent U.S. Pat. No. 4,887,408. 
     Both types of embodiments have drawbacks. 
     Embodiments of the first type comprise a relatively large number of heating heads, which are not exploited along the return branch; and the devices are relatively expensive, and relatively complicated to service : a large number of heating heads must be simultaneously functional. 
     In embodiments of the second type, contact between the heating heads and the sheets of wrapping material is relatively short, so that the sheets of wrapping material are not always stabilized properly about the respective groups of cigarettes. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a method and device designed to at least partly eliminate the aforementioned drawbacks, and which at the same time are cheap and easy to implement. 
     According to the present invention, there are provided a method and device 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 schematic side view, with parts removed for clarity, of a device in accordance with the present invention; 
         FIGS. 2 to 7  show a schematic side views, with parts removed for clarity, of the  FIG. 1  device in different operating positions; 
         FIGS. 8 to 10  show steps in the wrapping of a packet of cigarettes by the  FIG. 1  device. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Number  1  in  FIG. 1  indicates as a whole a device for wrapping hinged-lid packets  2  (shown schematically) of cigarettes (not shown) in sheets  3  of heat-seal wrapping material. Device  1  comprises a feed wheel  4  for feeding packets  2  one at a time to a conveyor  5 , which feeds packets  2 , in a direction A along a path P 1 , from an input station  6  to an output station  7 ; and a folding unit  8  for folding each sheet  3  of wrapping material about respective packet  2  to form a wrapping  9 , in particular a tubular wrapping, having two superimposed portions  10  and  11  ( FIGS. 8 to 10 ). Device  1  also comprises a feed unit  12  for supplying sheets  3  of wrapping material at input station  6 ; and a conveyor  13  for feeding heating heads  14  in direction A along a path P 2 , which extends parallel to a portion of first path P 1 , so that, at each operating cycle, each heating head  14  travels in phase and in contact with a respective wrapping  9 . Each heating head  14  provides for sealing, by transferring heat to, the two portions  10  and  11  of respective wrapping  9 . 
     Conveyor  5  comprises a wheel  15 , which rotates about a respective axis  16  and, in turn, comprises a number of peripheral seats  17 , each for housing a respective wrapping  9  at each operating cycle. 
     Folding unit  8  comprises a moving member  18  for folding portions  10  upwards; and a fixed contrast member  19 , with which portions  11 , as wheel  15  rotates, are brought into contact and folded downwards onto respective portions  10 . 
     Conveyor  13  comprises a wheel  20 , which rotates about axis  16  and is fitted integrally with a number of fluidic or any other type of actuators  21 . Each actuator  21  supports a respective heating head  14 , and moves respective heating head  14  crosswise to paths P 1  and P 2 , in particular, radially with respect to axis  16 . 
     It should be pointed out that heating heads  14  are arranged in a line, and are so spaced that, in use, adjacent heating heads  14  can contact adjacent wrappings  9 . 
     In a further embodiment, not shown, conveyor  13  comprises one fluidic or any other type of actuator for moving a support—to which heating heads  14  are fitted integrally—crosswise to paths P 1  and P 2 , in particular, radially with respect to axis  16 . 
     Operation of device  1  will now be described as of the instant in which heating heads  14  are each located at a respective contact station  22 . 
     At this point, each actuator  21  moves respective heating head  14  towards and into contact with relative wrapping  9  ( FIG. 1 ). 
     Upon each heating head  14  contacting relative wrapping  9 , wheels  15  and  20  rotate in steps in direction A until the leading heading head  14 ′ in the line of heating heads  14  is positioned immediately upstream from output station  7  ( FIGS. 2 to 5 ). 
     At this point, each heating head  14  is located at a respective withdrawal station  23 , where each actuator  21  withdraws respective heating head  14  from relative wrapping  9 . 
     Once heating heads  14  are withdrawn from respective wrappings  9 , wheel  20  is reversed to feed each heating head  14  continuously from respective withdrawal station  23  to respective contact station  22  along path P 2  in a direction B opposite direction A ( FIGS. 6 and 7 ) 
     It should be pointed out that the contact station  22 ′ of the leading heating head  14 ′ substantially coincides with or (in further embodiments) is located downstream from the withdrawal station  23 ″ of the trailing heating head  14 ″ in the line of heating heads  14 . In the embodiment shown, contact station  22 ′ is located immediately downstream from withdrawal station  23 ″. 
     It should also be pointed out that wheel  20  conveys heating heads  14  in direction B at a second speed V 2  greater than a first speed V 1  at which wheel  20  conveys heating heads  14  in direction A. 
     More specifically, speeds V 1  and V 2  are related by the equation:
 
 V 2≧( n - m )× V 1
 
where V 1  is the first speed; V 2  is the second speed; n is the given number of heating heads  14 ; and m is a integer smaller than n. In the embodiment shown, n equals six, m equals four, and speeds V 1  and V 2  are related by the equation:
 
 V 2≅2 ×V 1
 
     When n is greater than one, m preferably equals one; in which case, for device  1  to operate well, contact station  22 ′ substantially coincides with withdrawal station  23 ″. 
     The particular design and operation of device  1  provide for achieving top-quality sealing of portions  10  and  11 , by maintaining relatively prolonged contact between each heating head  14  and relative wrapping  9 . Furthermore, device  1  comprises a relatively small number of heating heads  14 , which, in use, travel along short trajectories and are moved by a relatively straightforward, compact conveyor  13 . 
     It should be pointed out that, though the embodiment shown comprises six heating heads  14 , device  1  may even comprise only one heating head  14  and preferably at least two heating heads  14 . 
     In further embodiments not shown, device  1  comprises folding and sealing members for folding and completely stabilizing sheets  3  of wrapping material about respective packets  2 . 
     It should also be pointed out that, though the embodiment and drawings shown relate to a device  1  for wrapping packets  2  in sheets  3  of heat-seal material, the teachings of the present invention also apply to stabilizing sheets  3  of paper material applied with heat-setting and/or hot-melt adhesive. 
     Though the above description and attached drawings relate to stabilizing a conventional hinged-lid packet  2  of cigarettes, the teachings of the present invention obviously also apply to any type of packet, such as a “soft” packet of cigarettes. 
     Moreover, in alternative embodiments not shown, some longitudinal and/or transverse edges of packet  2  may be non-square rounded or bevelled edges. For example, the longitudinal edges may be non-square rounded or bevelled edges, or (as in the packet of cigarettes described in Patent Application EP-A1-0764595), the major transverse edges may be non-square rounded or bevelled edges; or some longitudinal and transverse edges may be non-square edges, so as to have both non-square rounded or bevelled longitudinal and transverse edges. 
     In a different embodiment not shown, packet  2  may resemble the packet of cigarettes described in Patent Application EP-A1-1066206; in which case, each major lateral wall is outwardly convex, and comprises a flat central portion and two curved, creased lateral bands. 
     The teachings of the present invention obviously also apply to the manufacture of cartons of cigarettes, and to packages of other than cigarettes, such as food products, confectionary, or toiletries.