Patent Publication Number: US-6219995-B1

Title: Packaging machine

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a packaging machine. 
     Explicit reference will be made in the following specification to the field of packaging machines for manufacturing packets of cigarettes, albeit no limitation is implied. 
     Packaging machines embraced by the prior art, as disclosed for example in U.S. Pat. No. 4,918,901, comprise a wrapping wheel equipped with a plurality of conveying heads each affording a first seat, of which the function is to admit and retain a product for wrapping, and a second seat serving to admit and retain a respective sheet of wrapping material held in a predetermined position across an opening presented by the first seat through the agency of a pair of vacuum type gripping elements located one on either side of the opening and operated by means of a control device mounted to the wrapping wheel in a central position. 
     In operation the wrapping wheel is made to rotate intermittently about a fixed central axis in such a way as to index the conveying head through a first infeed station, at which the product is directed into the first seat, then a second infeed station at which the wrapping sheet is taken up into the second seat, and finally an outfeed station where the product is ejected from the first seat in such a way as to associate with the wrapping sheet, and transferred together with the sheet to a further wrapping wheel. 
     Packaging machines of the type outlined above are somewhat costly inasmuch as the wrapping wheel must carry both the gripping elements and the relative control device, and tends as a result to be complex in design and construction. 
     The object of the present invention is to provide a packaging machine free from the drawback outlined above, and therefore simple and economical to carry into effect. 
     SUMMARY OF THE INVENTION 
     The stated object is realized according to the invention in a packaging machine that incorporates a conveying head; a first seat afforded by the conveying head, presenting an opening and serving to receive a product; a second seat afforded by the conveying head, positioned to coincide with the opening of the first seat and serving to receive a wrapping sheet; gripper means by which a relative wrapping sheet is held in contact with the second seat; actuator means operating the gripper means; a conveyor by which the conveying head is advanced along a wrapping path; also a first infeed station located along the wrapping path, at which a product is taken up by the first seat; a second infeed station located along the wrapping path at which a wrapping sheet is taken up by the second seat; and ejector means by which a product is distanced from the conveying head and transferred together with a respective wrapping sheet to external conveying means. 
     To advantage, in the packaging machine disclosed, the actuator means are positioned externally of the conveyor. 
    
    
     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 is a schematic elevation showing a preferred embodiment of a packaging machine according to the present invention, illustrated partly in section and with certain parts omitted for clarity; 
     FIG. 2 shows a detail of FIG. 1, enlarged and in two different operating configurations; 
     FIG. 3 shows the detail of FIG. 2 in an alternative embodiment; 
     FIG. 4 shows a further embodiment of the detail of FIG. 2 in two different operating configurations. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1 of the drawings,  1  denotes a cigarette packaging machine, in its entirety, which comprises a power driven wrapping wheel  2  indexable about an axis  3  of rotation perpendicular to the viewing plane of FIG.  1  and carrying four peripheral conveying heads  4  equispaced around the axis  3 . Each head  4  incorporates a first seat  5  designed to admit and retain a group  6  of cigarettes, disposed radially to the axis  3  of rotation, also a second seat  7  extending along the periphery of the wheel  2  and associated with the first seat  5 , designed to receive and retain a sheet  8  of wrapping material in a position tangential to the periphery of the wheel and straddling an opening  9  afforded by the first seat  5 . 
     The single head  4  is made by the rotation of the wheel  2  to advance along a path, denoted P, through a first infeed station S 1  at which the first seat  5  receives a group  6  of cigarettes from a seat  10  of a conventional power driven feed wheel  11  rotatable about an axis (not indicated) lying parallel to the axis  3  of the wheel  2 . The head  4  is also made to advance through a second infeed station S 2 , where the second seat  7  receives a sheet  8  of wrapping material from a feed unit  12 , and finally through an outfeed station denoted S 3  at which the group  6  of cigarettes is ejected from the head  4  in such a manner that it will be associated and transferred together with the wrapping sheet  8  into a seat  13  afforded by another power driven wrapping wheel  14  of conventional embodiment indexed about an axis (not indicated) extending parallel to the axis  3  of rotation. 
     Each of the heads  4  comprises a gripper device  15  associated with the corresponding first seat  5  and serving to retain a relative group  6  of cigarettes internally of the selfsame seat, thus counteracting the centrifugal force generated by the rotation of the wheel  2 . The gripper device  15  includes two jaws  16  pivotable about respective axes  17  disposed parallel to the axis  3  of the wheel  2  and capable thus of movement, brought about by a cam mechanism (not indicated, being of conventional embodiment), toward and away from a gripping position in which the opening  9  of the relative seat  5  is partially occluded by two profiles  18  at the extremities of the two jaws  16 . 
     Also forming a part of each conveying head  4  is a push rod  19  of familiar embodiment operated by a conventional cam mechanism (not illustrated) and capable of movement through the respective first seat  5  in concert with a corresponding push rod  20  associated with the seat  10  of the feed wheel  11 , by which a group  6  of cigarettes is transferred from the feed wheel seat  10  to the wrapping wheel seat  5  opposite, and with a corresponding push rod (not illustrated) associated with the seat  13  of the wheel  14  next in sequence, so as to transfer a group  6  of cigarettes from the one seat  5  to the adjacent seat  13 . 
     Lastly, each head  4  comprises a gripper device  21  associated with the respective second seat  7  and serving to retain a relative wrapping sheet  8  in contact with the seat  7 , occupying a predetermined position, thus counteracting the centrifugal force generated by the rotation of the wheel  2 . 
     In order to keep each successive wrapping sheet  8  breasted in contact with the relative seat  7  during the movement of the head  4  from the second infeed station S 2  to the outfeed station S 3 , the machine  1  comprises a pair of restraints  22  disposed facing and parallel to the periphery of the wheel  2  and combining to create an opening  23 , located at the outfeed station S 3 , through which the group  6  of cigarettes is transferred from the first seat  5  to the seat  13  of the adjacent wheel. 
     The feed unit  12  is a conventional feed mechanism comprising an outer power driven wheel  24  set in rotation about a fixed axis  25 , extending parallel to the axis  3  of the wheel  2 , and about a fixed inner wheel  26  functioning as the valve element for a pneumatic system by which a negative pressure is generated through a plurality of holes  27  in the outer wheel  24  so as to retain a wrapping sheet  8  in contact with the surface of this same wheel  24 . 
     Each gripper device  21  comprises a single clip  28  located on the part of the relative second seat  7  disposed forwardmost in the feed direction, hence to one side of the respective opening  9 . 
     Each clip  28  is mounted pivotably to the wheel  2  and made to oscillate about an axis  29  parallel to the axis  3  of rotation, by means of an actuator device  30 , between a position of disengagement (indicated by phantom lines in FIG. 1) in which a relative wrapping sheet  8  is received or released, and a position of engagement (indicated by solid lines in FIG. 1) in which the wrapping sheet  8  is held in contact with the second seat  7 . 
     The actuator device  30  comprises a pair of single actuators  31  serving to operate the clip  28 , which are entirely similar and located externally of the wrapping wheel  2  occupying fixed positions relative to the machine  1  at the second infeed station S 2  and the outfeed station S 3  respectively. 
     Each actuator  31  is designed to bring about the movement of a single clip  28  from the position of engagement to the position of disengagement against the action of a relative bias spring  32 , by which the clip  28  is maintained normally in the position of engagement with a predetermined force. 
     In the example of FIG. 2, each clip  28  is embodied in a ferromagnetic material, and each actuator  31  comprises an electromagnet, denoted  33 , of which the operation is piloted by a control device  34  in such a way that the creation of a magnetic field will attract the clip  28  and cause it to assume the position of disengagement, opposing the action of the spring  32 . 
     In the example of FIG. 3, each clip  28  is embodied in a ferromagnetic material, and each actuator  31  comprises a permanent magnet, denoted  35 , mounted slidably and capable of movement in a direction  36  normal to the wrapping path P, brought about by a relative control device  37 , toward and away from an operating position of close proximity to a clip  28 , in which the clip is attracted and caused to assume the position of disengagement, opposing the action of the spring  32 . 
     In the embodiments of FIGS. 2 and 3, each gripper device  21  comprises a rocker  38 , mounted pivotably to the wheel  2  and able thus to oscillate about the relative axis  29 , of which one arm  39  functions as the movable clip  28  and another arm  40  is connected mechanically to the relative spring  32 . 
     In the example of FIG. 4, each gripper device  21  again comprises a rocker  38 , mounted pivotably to the wheel  2  and able thus to oscillate about the relative axis  29 , of which a first arm  39  provides the movable clip  28 , a second arm  40  is connected mechanically to the spring  32  and a third arm  41  carries a cam follower  42  consisting in a roller that can be operated in such a manner as to shift the clip  28  from the position of engagement to the position of disengagement. 
     Still referring to FIG. 4, the single actuator  31  comprises a fixed cam profile  43  which operates in conjunction with each individual roller  42  in such a way as to shift the relative clip  28  toward the position of disengagement against the action of the spring  32 . 
     In a further embodiment, not illustrated in the accompanying drawings, the actuator  31  associated with the second infeed station S 2  might include a pushing element carried by the wheel  24  of the feed unit  12  and operating in conjunction with each roller  42  in such a manner as to shift the relative clip  28  into the position of disengagement against the action of the spring  32 . 
     Referring to FIG. 1, the operation of the machine will now be described following the movements of a single conveying head  4 , beginning from the moment when the head  4  is brought into the first infeed station S 1  by the rotation of the wheel  2 . 
     At this first station S 1 , a group  6  of cigarettes is transferred to the first seat  5  of the head  4  in familiar manner, whereupon the wheel  2  rotates 90° (counterclockwise as seen in FIG. 1) to advance the head toward the second infeed station S 2 . During the first part of the movement toward the second station S 2  the jaws  16  assume the gripping position in order to retain the group  6  of cigarettes in the seat  5 . 
     As the head  4  reaches the station S 2  the relative actuator  31  will cause the leading clip  28  to pivot away from the position of engagement and toward the position of disengagement, so that the seat  7  can receive a corresponding wrapping sheet  8  from the feed unit  12  in familiar manner. 
     Once the sheet  8  has been taken up by the seat  7 , the first actuator  31  changes state and the clip  28  is returned by the action of the spring  32  to the position of engagement, pinning the sheet  8  in a predetermined position relative to the seat  7 . The head  4  then rotates a further 90° (counterclockwise in FIG. 1) toward the outfeed station S 3 . As the head  4  draws into alignment with the station S 3  the second actuator  31  changes state and the clip  28  is made to shift away from the position of engagement to the position of disengagement, thus allowing the sheet  8  to be removed from the seat  7  when invested by the group  6  of cigarettes directed toward the seat  13  of the adjacent wheel  14  by the action of the push rod  19 . 
     Once the group  6  has been transferred from the one seat  5  to the other seat  13 , the actuator  31  again changes state and the clip  28  is returned to the position of engagement by the spring  32 . Finally, the wheel  2  rotates 180° (counterclockwise in FIG. 1) to return the head  4  to the first infeed station S 1  and the sequence of steps described thus far will be repeated for a successive group  6  of cigarettes and a successive wrapping sheet  8 .